[Federal Register: June 6, 2005 (Volume 70, Number 107)]
[Rules and Regulations]
Department of Labor
Mine Safety and Health Administration
30 CFR Part 57
Diesel Particulate Matter Exposure of Underground Metal and Nonmetal
Miners; Final Rule
DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Part 57
Diesel Particulate Matter Exposure of Underground Metal and
AGENCY: Mine Safety and Health Administration (MSHA), Labor.
ACTION: Final rule.
SUMMARY: This final rule revises MSHA's existing standards addressing
diesel particulate matter (DPM) exposure in underground metal and
nonmetal (M/NM) mines. In this final rule, MSHA changes the interim
concentration limit measured by total carbon (TC) to a comparable
permissible exposure limit (PEL) measured by elemental carbon (EC),
which renders a more accurate DPM exposure measurement. Also, this
final rule increases flexibility of compliance for mine operators by
requiring MSHA's longstanding hierarchy of controls for its other
exposure-based health standards at M/NM mines, but retains the
prohibition on rotation of miners for compliance. Furthermore, this
final rule: Requires MSHA to consider economic as well as technological
feasibility in determining if operators qualify for an extension of
time in which to meet the final DPM limit; deletes the requirement for
a control plan; and makes conforming changes to existing provisions
concerning compliance determinations, environmental monitoring and
DATES: Effective Date: The final rule is effective on July 6, 2005.
FOR FURTHER INFORMATION CONTACT: Office of Standards, Regulations, and
Variances, MSHA, 1100 Wilson Blvd., Room 2350, Arlington, Virginia
22209-3939; 202-693-9440 (telephone); or 202-693-9441 (facsimile).
You may obtain copies of this final rule and the Regulatory
Economic Analysis (REA) in alternative formats by calling 202-693-9440.
The alternative formats available are either a large print version of
these documents or electronic files that can be sent to you either on a
computer disk or as an attachment to an e-mail. The documents also are
available on the Internet at http://www.msha.gov/REGSINFO.HTM.
Outline of Preamble
This outline will assist the mining community in finding
information in this preamble.
I. List of Common Terms
II. Rulemaking Background
A. First Partial Settlement Agreement
B. Second Partial Settlement Agreement
III. The Final PEL
IV. The 31-Mine Study
B. Subsequent Activities
V. Compliance Assistance
A. Baseline Sampling
B. DPM Control Technology
VI. DPM Exposures and Risk Assessment
B. DPM Exposures in Underground M/NM Mines
C. Health Effects
D. Significance of Risk
B. Technological Feasibility
C. Economic Feasibility
VIII. Summary of Costs and Benefits
IX. Section-by-Section Analysis
X. Distribution Table
XI. Regulatory Impact Analysis
XII. References Cited
I. List of Common Terms
Listed below are the common terms used in the preamble.
Commission........................ Federal Mine Safety and Health
CV................................ coefficient of variation.
DE................................ diesel exhaust.
DOCs.............................. diesel oxidation catalysts.
DPF............................... diesel particulate filter.
DPM............................... diesel particulate matter.
EC................................ elemental carbon.
ETS............................... environmental tobacco smoke.
Filter Selection Guide............ Diesel Particulate Filter. Selection
Guide for Diesel-powered Equipment
in Metal and Nonmetal Mines.
First Partial Settlement Agreement 66 FR 35518 (2001) & 66 FR 35521
(2001): basis for July 5, 2001
HEI............................... Health Effects Institute.
HWE............................... healthy worker effect.
MARG.............................. Methane Awareness Resource Group.
MSHA.............................. Mine Safety and Health
NIOSH............................. National Institute for Occupational
Safety and Health.
NTP............................... National Toxicology Program.
OC................................ organic carbon.
PAPR.............................. powered air-purifying respirator.
PEL............................... permissible exposure limit.
PPM............................... parts per million.
QRA............................... quantitative risk assessment.
REA............................... Regulatory Economic Analysis.
Second Partial Settlement 67 FR 47296 (2002): basis for August
Agreement. 14, 2003 NPRM.
SD................................ standard deviation.
SKC............................... SKC, Inc.
TC................................ total carbon.
USWA.............................. United Steelworkers of America.
[mu]g/cm \2\...................... micrograms per square centimeter.
[mu]g/m \3\....................... micrograms per cubic meter.
2001 final rule................... January 19, 2001 DPM final rule.
Amended 2001 final rule........... 2001 final rule amended on February
2002 final rule................... February 27, 2002 final rule.
2002 ANPRM........................ Advance Notice of Proposed
Rulemaking published on September
2003 NPRM......................... Notice of Proposed Rulemaking
published on August 14, 2003.
II. Rulemaking Background
On January 19, 2001, MSHA published a final rule (2001 final rule)
addressing DPM exposure in underground M/NM mines (66 FR 5706), amended
on February 27, 2002 at 67 FR 9180 (2002 final rule). The 2001 final
rule established new health standards for underground M/NM mines that
use equipment powered by diesel engines. The effective date of the 2001
final rule was listed as March 20, 2001. On January 29, 2001, AngloGold
(Jerritt Canyon) Corp. and Kennecott Greens Creek Mining Company filed
a petition for review of the 2001 final rule in the District of
Columbia Circuit Court of Appeals. On February 7, 2001, the Georgia
Mining Association, the National Mining Association (NMA), the Salt
Institute, and the Methane Awareness Resource Group (MARG) Diesel
Coalition filed a similar petition in the Eleventh Circuit. On March
14, 2001, Getchell Gold Corporation petitioned for review of the rule
in the District of Columbia Circuit. The three petitions were
consolidated, and are pending in the District of Columbia Circuit. The
United Steelworkers of America (USWA) intervened in the litigation.
While these challenges were pending, the AngloGold petitioners
filed with MSHA an application for reconsideration and amendment of the
2001 final rule and for postponement of the effective date of the 2001
final rule pending judicial review. The Georgia Mining Association
petitioners similarly filed with MSHA a request for an administrative
stay or postponement of the effective date of the 2001 final rule. On
March 15, 2001, MSHA delayed the effective date of the 2001 final rule
until May 21, 2001, in accordance with a January 20, 2001 memorandum
from the President's Chief of Staff (66 FR 15032). The delay was
necessary to give Department of Labor officials the opportunity for
further review and consideration of new regulations. On May 21, 2001
(66 FR 27863), MSHA published a document in the Federal Register
delaying the effective date of the 2001 final rule until July 5, 2001.
The purpose of this delay was to allow the Department of Labor the
opportunity to engage in further negotiations to settle the legal
challenges to the 2001 final rule.
A. First Partial DPM Settlement Agreement
As a result of a partial settlement agreement with the litigants,
MSHA published two documents in the Federal Register on July 5, 2001
addressing the 2001 final rule. One document (66 FR 35518) delayed the
effective date of Sec. 57.5066(b) regarding the tagging provision of
the maintenance standard; clarified the effective dates of certain
provisions of the 2001 final rule; and included correcting amendments.
The second document (66 FR 35521) proposed a rule to clarify Sec.
57.5066(b)(1) and (b)(2) regarding maintenance and to add a new
paragraph (b)(3) to Sec. 57.5067 regarding the transfer of existing
equipment between underground mines. MSHA published these changes as a
final rule on February 27, 2002 (67 FR 9180) (2002 final rule), with an
effective date of March 29, 2002.
Under the first partial settlement agreement, MSHA also conducted
joint sampling with industry and labor at 31 underground M/NM mines to
determine existing concentration levels of DPM; to assess the
performance of the SKC, Inc., Eighty Four, PA (SKC) submicron dust
sampler with the NIOSH Method 5040; to assess the feasibility of
achieving compliance with the standard's concentration limits at the 31
mines; and to assess the impact of interferences on samples collected
in the M/NM underground mining environment before the limits
established in the final rule became effective. The final report was
issued on January 6, 2003.
B. Second Partial Settlement Agreement
Settlement negotiations continued on the remaining unresolved
issues in the litigation. On July 15, 2002, the parties signed an
agreement (second partial settlement agreement) that formed the basis
for MSHA's August 14, 2003 proposed rule (68 FR 48668) (2003 NPRM). On
July 18, 2002, MSHA published a document in the Federal Register (67 FR
47296) announcing, among other things, that the following provisions of
the 2001 final rule would become effective on July 20, 2002:
Sec. 57.5060(a), Addressing the interim concentration
limit of 400 micrograms of TC per cubic meter of air;
Sec. 57.5061, Compliance determinations; and
Sec. 57.5071, Environmental monitoring.
The document also announced that the following provisions of the
rule would continue in effect:
Sec. 57.5065, Fueling practices;
Sec. 57.5066, Maintenance standards;
Sec. 57.5067, Engines;
Sec. 57.5070, Miner training; and
Sec. 57.5075, Diesel particulate records, as they relate
to the requirements of the rule that went into effect on July 20, 2002.
The document also stayed the effectiveness of the following
provisions pending completion of this final rule:
Sec. 57.5060(d), Permitting miners to work in areas where
the level of DPM exceeds the applicable concentration limit with
advance approval from the Secretary;
Sec. 57.5060(e), Prohibiting the use of personal
protective equipment (PPE) to comply with the concentration limits;
Sec. 57.5060(f) Prohibiting the use of administrative
controls to comply with the concentration limits; and
Sec. 57.5062, DPM control plan.
Finally, the July 18, 2002, document outlined the terms of the DPM
settlement agreement and announced MSHA's intent to propose specific
changes to the rule, as discussed below.
On September 25, 2002, MSHA published an Advance Notice of Proposed
Rulemaking (2002 ANPRM) (67 FR 60199) to amend certain provisions of
the 2001 DPM rule.
The comment period closed on November 25, 2002. MSHA received
comments from underground M/NM mine operators, trade associations,
organized labor, public interest groups and individuals. On August 14,
2003, MSHA published the 2003 NPRM in the Federal Register (68 FR
48668) recommending certain revisions to the DPM rule as part of a
settlement agreement reached in response to a legal challenge to the
DPM standard. Public hearings were held in Salt Lake City, Utah; St.
Louis, Missouri; Pittsburgh, Pennsylvania; and Arlington, Virginia in
September and October 2003. The comment period closed on October 14,
2003. On February 20, 2004, MSHA published a document in the Federal
Register announcing a limited reopening of the comment period on the
2003 NPRM. This document reopened the comment period to obtain public
input on three new documents related to the August 14, 2003 rulemaking
(69 FR 7881). The three documents were as follows:
(1) United States (U.S.) Department of Health and Human Services,
Center for Disease Control, National Institute of Occupational Safety
and Health, ``The Effectiveness of Selected Technologies in Controlling
Diesel Emissions in an Underground Mine--Isolated Zone Study at
Stillwater Mining Company's Nye Mine,'' January 5, 2004.
(2) U.S. Department of Labor, Bureau of Labor Statistics, and U.S.
Department of Health and Human Services, Center for Disease Control,
National Institute of Occupational Safety and Health, ``Respirator
Usage in Private Sector Firms, 2001,'' September, 2003.
(3) Chase, Gerald, ``Characterizations of Lung Cancer in Cohort
Studies and a NIOSH Study on Health Effects of Diesel Exhaust in
Miners,'' undated, received January 5, 2004.
The subsequent comment period closed on April 5, 2004. MSHA
received and reviewed written and oral statements on the 2003 NPRM from
all segments of the mining community.
MSHA informed the mining community in both its 2002 ANPRM and its
2003 NPRM of its intentions to incorporate into the record of the
current rulemaking the existing rulemaking record, including the risk
assessment to the 2001 final rule. Commenters were encouraged to submit
additional evidence of new scientific data related to health risks to
underground M/NM miners from exposure to DPM.
This final rule for DPM exposure at M/NM mines is based on
consideration of the entire rulemaking record, including all written
comments and exhibits received related to the 2001 final rule as well
as all related data received to the close of this rulemaking record. To
serve the interest of the mining community, MSHA is revising Sec. Sec.
57.5060, 57.5061, 57.5071, and 57.5075 and republishing Sec. Sec.
57.5065, 57.5066, 57.5067, and 57.5070 of the DPM standards at 30 CFR
part 57 in order to present all sections in their entirety in this
document. What follows is a discussion of the specific revisions to the
2001 DPM standard:
Sec. 57.5060(a) addressing the interim limit on
concentration of DPM. MSHA has changed the 2001 final rule's interim
concentration limit of 400 micrograms of TC per cubic meter of air
(400TC [mu]g/m3) to a comparable permissible
exposure limit of 308 micrograms of EC per cubic meter of air
Sec. 57.5060(c) addressing application and approval
requirements for an extension of time in which to reduce the final DPM
limit. MSHA has changed the 2001 final rule by requiring MSHA to
consider economic feasibility along with technological feasibility
factors in weighing whether to grant special extensions; has deleted
the limit on the number of special extensions that may be granted to
each mine; has limited each extension to a period of one year; has
allowed for annual renewals of special extensions; and has allowed the
MSHA District Manager, rather than the Secretary, to grant extensions.
This final rule retains the scope of the 2001 provision for operators
to apply for extensions to the final DPM limit;
Sec. 57.5060(d) addressing certain exceptions to the
Sec. 57.5060(e) prohibiting use of PPE to comply with the
Sec. 57.5060(f) prohibiting use of administrative
controls to comply with the concentration limits. MSHA has changed the
2001 final rule by implementing the current hierarchy of controls as
adopted in MSHA's other exposure-based health standards for M/NM mines.
MSHA's hierarchy includes primacy of engineering and administrative
controls to the extent feasible to reduce a miner's exposure to the
PEL, but MSHA continues to prohibit rotation of miners for compliance
purposes. If a miner's exposure cannot be reduced to the PEL with use
of feasible controls, controls are infeasible, or do not produce
significant reductions in DPM exposures, the new final rule requires
mine operators to supplement a miner's protection with respirators and
implement a respiratory protection program. This respiratory protection
program must meet the requirements in existing 30 CFR 57.5005, but
miners may only use the respirator filters specified by MSHA for DPM in
this section. Therefore, MSHA removes the 2001 prohibition against use
of respiratory protection without approval by the Secretary and
clarifies that use of administrative controls other than rotation of
miners is allowed;
Sec. 57.5062, addressing the diesel particulate control
plan. This final rule removes the existing requirement for a DPM
control plan; and
conforming changes to the following existing standards
that were proposed on August 14, 2003:
[cir] Sec. 57.5061, addressing compliance determinations;
[cir] Sec. 57.5071, addressing exposure monitoring; and,
[cir] Sec. 57.5075, addressing recordkeeping requirements.
This final rule does not include provisions for written procedures
for administrative controls, a written respiratory protection program,
medical examination of miners before they are required to wear
respiratory protection, and medical transfer of miners who are unable
to wear respiratory protection for medical and psychological reasons.
III. The Final Concentration Limit
In the 2002 ANPRM, MSHA notified the mining community that this
rulemaking would revise both the interim concentration limit of 400
micrograms per cubic meter of air and the final concentration limit of
160 micrograms per cubic meter of air under Sec. 57.5060(a) and (b) of
the 2001 final rule. Some commenters to the ANPRM recommended that MSHA
propose separate rulemakings for revising the interim and final DPM
limits to give MSHA an opportunity to gather further information to
establish a final DPM limit. In the 2003 NPRM, MSHA agreed with these
commenters and solicited other information from the mining community
that would lead to an appropriate final DPM standard. Moreover, MSHA
announced its intentions to publish a separate rulemaking to amend the
existing final concentration limit in Sec. 57.5060(b). To assist MSHA
in achieving this purpose, MSHA requested comments on an appropriate
final permissible exposure limit rather than a concentration limit; and
asked for information on an appropriate surrogate for measuring miners'
DPM exposures. MSHA concluded its request for information by clarifying
that revisions to the final DPM concentration limit would not be a part
of this rulemaking.
In their comments to the 2003 NPRM, organized labor requested that
MSHA lower the final DPM limit below 160 micrograms based on
feasibility data and the significance of the health risks from exposure
to DPM. Industry trade associations and individual mine operators
recommended that MSHA repeal the final limit based on issues related to
health effects, inability of the mining industry to meet a lower limit
than 400 micrograms per cubic meter of air, and the need for MSHA to
have the results from the National Institute for Occupational Safety
and Health/National Cancer Institute (NIOSH/NCI) study and exposure-
MSHA believes that evidence in the current DPM rulemaking record is
inadequate for MSHA to make determinations regarding revision to the
final DPM limit.
IV. The 31-Mine Study
On January 19, 2001, MSHA published a final standard addressing
exposure of underground metal and nonmetal miners to diesel particulate
matter (DPM). The standard contained staggered effective dates for
interim and final concentration limits. The standard was challenged by
industry trade associations and several mining companies, and the
United Steelworkers of America (USWA) intervened in the litigation. The
parties agreed to resolve their differences through settlement
negotiations with MSHA. Thereafter, MSHA delayed the effective date of
certain provisions of the standard. As part of the settlement
negotiations, MSHA agreed to conduct joint sampling with the litigants
at 31 metal and nonmetal underground mines covered by the standard to determine
existing concentration levels of DPM in operating mines and to measure
DPM levels in the presence of known or suspected interferences.
The goals of the study were to use the sampling results and
related information to assess:
--The validity, precision and feasibility of the sampling and
analysis method specified by the diesel standard (NIOSH Method
--The magnitude of interferences that occur when conducting
enforcement sampling for total carbon as a surrogate for diesel
particulate matter (DPM) in mining environments; and,
--The technological and economic feasibility of the underground
metal and nonmetal (MNM) mine operators to achieve compliance with
the interim and final DPM concentration limits.
--The parties developed a joint MSHA/Industry study protocol to
guide sampling and analysis of DPM levels in 31 mines. The parties
also developed four subprotocols to guide investigations of the
known or suspected interferences, which included mineral dust, drill
oil mist, oil mist generated during ammonium nitrate/fuel oil (ANFO)
loading operations, and environmental tobacco smoke (ETS). The
parties also agreed to study other potential sampling problems,
including any manufacturing defects of the DPM sampling cassette.
(Executive Summary, Report on the 31-Mine Study)
MSHA requested that NIOSH peer review the draft Report on the 31-
Mine Study, and NIOSH's conclusions were as follows:
1. Most mines have DPM concentrations higher than
2. The impactor was effective in eliminating mineral dust from
collecting onto the filter analyzed for carbon by NIOSH Method 5040.
3. The ANFO data was inconclusive.
4. Oil mist from the stoper drill is a sub-micron aerosol and a
potential interference. Oil mist contamination from the driller can
be avoided by sampling upstream of stope or far enough downstream
that the oil mist has been diluted enough to give minimal TC
concentrations (if this type of sampling is possible).
5. No information about the interference of environmental
tobacco smoke is present in this report.
6. The inter-laboratory comparison of the NIOSH method 5040 of
paired punches from the same filter showed reasonable agreement
between MSHA results and commercial laboratory results and excellent
agreement between MSHA and NIOSH laboratory results. (Summary of
Findings of this Report in ``NIOSH Comments and recommendations on
the MSHA DRAFT report: Report on the Joint MSHA/Industry Study:
Determination of DPM Levels in Underground Metal and Nonmetal
Mines,'' dated June 3, 2002)
On January 6, 2003, MSHA issued its final report entitled, ``MSHA's
Report on Data Collected During a Joint MSHA/Industry Study of DPM
Levels in Underground Metal And Nonmetal Mines'' (Report on the 31-Mine
Study). MSHA's major conclusions drawn from the study are as follows:
--The analytical method specified by the diesel standard gives an
accurate measure of the TC content of a filter sample and the
analytical method is appropriate for making compliance
determinations of DPM exposures of underground metal and nonmetal
--SKC satisfactorily addressed concerns over defects in the DPM
sampling cassettes and availability of cassettes to both MSHA and
--Compliance with both the interim and final concentration limits
may be both technologically and economically feasible for metal and
nonmetal underground mines in the study. MSHA, however, has limited
in-mine documentation on DPM control technology. As a result, MSHA's
position on feasibility does not reflect consideration of current
complications with respect to implementation of controls, such as
retrofitting and regeneration of filters. MSHA acknowledges that
these issues may influence the extent to which controls are
feasible. The Agency is continuing to consult with the National
Institute of Occupational Safety and Health, industry and labor
representatives on the availability of practical mine worthy filter
--The submicron impactor was effective in removing the mineral dust,
and therefore its potential interference, from DPM samples.
Remaining interference from carbonate interference is removed by
subtracting the 4th organic peak from the analysis. No reasonable
method of sampling was found to eliminate interferences from oil
mist or that would effectively measure DPM levels in the presence of
ETS with TC as the surrogate * * * (Executive Summary, Report on the
MSHA's complete report on the 31-Mine Study is contained in the
MSHA and NIOSH have reviewed the performance characteristics of the
SKC sampler, and are satisfied that it accurately measures exposures to
DPM. NIOSH found in laboratory and field data that the SKC DPM cassette
collected DPM efficiently. In a side protocol of the 31-Mine Study,
MSHA tested the efficiency of the SKC DPM cassette to avoid mineral
dust in four different mines and did not measure any mineral dust on
the filter when the SKC DPM cassette was used. This was confirmed by
laboratory results at NIOSH. (Noll, J. D., Timko, R. J., McWilliams,
L., Hall, P., Haney, R., ``Sampling Results of the Improved SKC Diesel
Particulate Matter Cassette,'' JOEH, 2005 Jan; 2(1):29-37.)
Results of the 31-Mine Study and the MSHA baseline compliance
assistance sampling demonstrated that the SKC submicron impactor
removed potential interferences from mineral dust from the collected
Interference from drill oil mist was found on personal samples
collected on the stoper and jackleg drillers and on area samples
collected in the stope where drilling was being performed. Use of a
dynamic blank did not eliminate drill oil mist interference. Tests to
confirm whether oil mist from ANFO loading operations could be an
interference were not conclusive. Blasting did not interfere with
diesel particulate measurements. MSHA found no reasonable method of
sampling to eliminate interferences from oil mist when TC is used as
No reliable marker was identified for confirming the presence of
ETS in an atmosphere containing DPM. Use of the impactor does not
remove the ETS as an interferent. No reasonable method of sampling was
found that would effectively measure DPM levels in the presence of ETS
with TC as the surrogate.
MSHA has found that the use of EC eliminates potential sampling
interference from drill oil mist, tobacco smoke, and organic solvents,
and that EC consistently represents DPM. In comparison to using TC as
the DPM surrogate, using EC would impose fewer restrictions or caveats
on sampling strategy (locations and durations), would produce a
measurement much less subject to questions, and inherently would be
more precise. Furthermore, NIOSH, the scientific literature, and the
MSHA laboratory tests indicate that DPM, on average, is approximately
60 to 80% elemental carbon, firmly establishing EC as a valid surrogate
As part of the 31-Mine Study, representatives from MSHA, NIOSH, and
SKC met to address the following issues:
The quality of manufactured SKC DPM cassettes;
The feasibility of adding a dynamic blank filter to the
SKC DPM cassette; and
The possibility of putting a number on each SKC DPM
Also, in its October 16, 2001 letter, MSHA informed SKC about the
problems that MSHA and the industry encountered using the SKC DPM
sampling cassette with the submicron impactor. These problems included:
dark flecks, alleged leaks, loose fitting nozzles and connectors, and
difficulty in shipping the sampler. As discussed in the report on the
31-Mine Study, SKC was responsive in addressing those concerns.
B. Subsequent Activities
Some industry commenters continued to state that the sampling and
analytical processes for DPM are too new for regulatory use. Other
commenters questioned the availability and reliability of the SKC
MSHA moved expeditiously to help resolve the back-order and
manufacturing delays for samplers reported in the 31-Mine Study.
However, operators who sample alongside MSHA continued to request ample
notice to have enough samplers available. MSHA purchased many of the
initial production runs of these samplers to conduct its compliance
assistance baseline sampling. Once the initial orders were filled, the
sampler became more widely available.
Some commenters stated that SKC changed the impactor, and that
NIOSH should test the new SKC sampler and evaluate its comparability to
the model used in the 31-Mine Study. One of these commenters stated
that the shelf life of the prior sampler affected TC measurements by
adsorbing organic carbon (OC) from the polystyrene assembly onto the
filter media and increasing TC measurement. These commenters questioned
MSHA's changes to the SKC sampler following completion of the 31-Mine
Study, and suggested that a defect to the sampler could have affected
the results of the study. During the 31-Mine Study, MSHA observed that
the deposit area of the SKC submicron impactor filter was not as
consistent as those obtained for preliminary evaluation. This was
attributed to inconsistent crimping of the aluminum foil cone on the
Prior to the 31-Mine Study, MSHA had determined the deposit area of
the sample filter to be 9.12 square centimeters (cm\2\) with a standard
deviation of 3.1 percent (%). During the initial phases of the sampling
analysis of the 31-Mine Study, it became apparent that the variability
of the deposit area was greater than originally determined. The filter
area is critical to the concentration calculation. The filter area
(measured in cm\2\) is multiplied by the results of the analysis
(micrograms per cm\2\) to get the total filter loading (micrograms).
While individual filter areas could be measured, it is more practical
to have a uniform deposit area for the calculations. As a result, NIOSH
and MSHA consulted with SKC to develop an improved filter cassette
design. With the cooperation of MSHA and the technical recommendations
and extensive experimental verification by NIOSH, SKC was able to
modify their cassette design to produce a consistent and regular DPM
deposit area, satisfactorily resolving the problem. SKC, in cooperation
with MSHA and NIOSH, then modified the DPM cassette following the 31-
The modification was limited to replacing the foil filter capsule
with a 32 millimeter (32-mm) ring. This was done to give a more uniform
deposit area (8.04 cm\2\) with negligible variability, and to
accommodate two 38-mm quartz fiber filters in tandem (double filters).
These double filters are assembled into a single cassette along with
the impactor. The 38-mm filters also eliminate cassette leakage around
the filters. These modifications were completed and incorporated into
units manufactured after November 1, 2002.
The results of this project were prepared into a scientific
publication, ``Sampling Results of the Improved SKC Diesel Particulate
Matter Cassette,'' referenced above. This paper has been peer reviewed
and was published in January 2005. The following abstract was prepared
for the study results:
Diesel particulate matter (DPM) samples from underground metal/
non-metal mines are collected on quartz fiber filters and measured
for carbon content using National Institute for Occupational Safety
and Health Method 5040. If size selective samplers are not used to
collect DPM in the presence of carbonaceous ore dust, both the ore
dust and DPM will collect on the quartz filters, causing the carbon
attributed to DPM to be artificially high. Because the DPM particle
size is much smaller than that of mechanically generated mine dust
aerosols, it can be separated from the larger mine dust aerosol by a
single stage impactor. The SKC DPM cassette is a single stage
impactor designed to collect only DPM aerosols in the presence of
carbonaceous mine ore aerosols, which are commonly found in
underground nonmetal mines. However, there is limited data on how
efficiently the SKC DPM cassette can collect DPM in the presence of
ore dust. In this study, we investigated the ability of the SKC DPM
cassette to collect DPM while segregating ore dust from the sample.
We found that the SKC DPM cassette accurately collected DPM. In the
presence of carbon-based ore aerosols having an average
concentration of 8 mg/m3, no ore dust was detected on SKC
DPM cassette filters. We did discover a problem: the surface areas
of the DPM deposits on SKC DPM cassettes, manufactured prior to
August 2002, were inconsistent. To correct this problem, SKC
modified the cassette. The new cassette produced, with 99%
confidence, a range of DPM deposit areas between 8.05 and 8.28
cm2, a difference of less than 3%.
Because the design of the inlet cyclone, impaction nozzles, and the
impaction plate and the flow rate did not change, the modifications to
the filter assembly did not alter the collection or separation
performance of the impactor. Throughout the compliance baseline
sampling, the impactor has been a consistent and reliable sampling
Tandem filters were used in the oil mist and ANFO interference
evaluations during the 31-Mine Study. The top filter collects the
sample and the bottom filter is a dynamic blank. The dynamic blank
provides a unique field blank for each DPM cassette. The use of EC as a
surrogate would resolve the commenter's concern about shelf life and OC
out-gassing on the filter. Shelf life and OC out-gassing are issues
relative to OC measurements. These two issues do not apply to an EC
measurement. Once the cassettes have been preheated during
manufacturing, there is no source, other than sampling, to add EC to
the sealed cassette filters.
MSHA discussed in the preamble to the 2003 NPRM issues related to
interferences, field blanks and the error factor. Some comments on the
2003 NPRM still expressed concerns on interferences and further stated
that the MSHA industrial hygiene studies, conducted to verify the
magnitude of the interference problem, were not published or peer
reviewed and should be removed from the rulemaking record. However,
MSHA, organized labor, and the mining industry, through the
negotiations process, jointly developed the protocol for conducting the
31-Mine Study. All of the parties agreed on the protocol following
numerous discussions among industry, labor, and government experts, and
had an opportunity to comment and make changes to the document.
Thereafter, MSHA conducted the study, following the agreed upon
protocol, and published its results. Before publication, the report was
peer reviewed by NIOSH. Industry was given an opportunity to publish
their separate results simultaneously with the government. During this
rulemaking, industry submitted to MSHA through the notice and comment
process their conclusions on the 31-Mine Study in a report titled,
``Technical and Economic Feasibility of DPM Regulations.'' The industry
report is contained in the rulemaking record, and was considered by
MSHA in reaching determinations for this final rule.
In response to the question on whether there are interferences when
EC is used as the surrogate, some commenters stated that interferences
were thoroughly discussed in the preamble to the 2001 final rule, and
that reasonable practices to avoid them were stipulated in the rule
itself. According to these commenters, this problem should not be revisited in this
Other commenters maintained that the 31-Mine Study did not contain
the necessary protocols to address all potential interferences. Thus,
in their view, MSHA does not have all the data required to answer this
question. More specifically, some commenters stated that carbonaceous
particulate in host rock has a smaller diameter than the impactor cut
point and so, may contaminate EC samples. These commenters then
concluded that MSHA should propose additional research and seek
comments on the research before concluding that sampling EC with an
impactor will eliminate all interference problems. However, no data
were presented to support this claim or conclusion. Commenters
submitted no new information relative to interferences in response to
the 2003 NPRM.
(2) Field Blanks
A field blank is an unexposed control filter meant to account for
background interferences and systematic contamination in the field,
spurious effects due to manufacturing and storage of the filter, and
systematic analytical errors. The tandem filter arrangement in the
sample cassette provides a primary filter for collecting an air sample
and a second filter, behind (after) the primary filter, which provides
a separate control filter for each sample. This is a much more flexible
method of sampling for the mining industry, since it eliminates the
need to send a separate control filter to the analytical lab. MSHA
informed the public of its intentions to adjust the EC result obtained
for each sample by the result obtained for the corresponding media
blank when MSHA measures for compliance purposes. When MSHA conducts
compliance measurements, MSHA will adjust the result obtained for each
corresponding sample by the field blank (tandem filter) result. No
comments or information related to field blanks were submitted to MSHA
in response to the 2003 NPRM.
In its comments on the 2002 ANPRM, NIOSH noted that two types of
blanks, media and field, are normally used for quality assurance
purposes. A media blank accounts for systematic contamination that may
occur during manufacturing or storage. A field blank accounts for
possible systematic contamination in the field. NIOSH does not
recommend use of field blanks when EC is the surrogate. This is because
EC measurements are not subject to sources of contamination in the
field that would affect OC and TC results. Quartz-fiber filters are
prone to OC vapor contamination in the field and to contamination by
less volatile OC (such as oils) during handling. However, such
contamination is irrelevant when EC is the surrogate.
(3) Error Factor
MSHA intends to cite a violation of the DPMEC exposure
limit only when MSHA has valid evidence that a violation actually
occurred. As with all other measurement-based M/NM compliance
determinations, MSHA will issue a citation only if a measurement
demonstrates noncompliance with at least 95% confidence. MSHA will
achieve this 95% confidence level by comparing each EC measurement to
the EC exposure limit multiplied by an appropriate error factor.
Generally, an error factor is used to compensate for certain known
inaccuracies in the sampling and analytical process, including such
things as the reliability of sampling equipment and precision of
analytical instrumentation. MSHA will continue to determine that an
overexposure has occurred when a sample exceeds the interim limit times
the error factor.
In this rulemaking, MSHA is discussing the procedure used to obtain
the error factor. This procedure is further discussed on the MSHA web
site at http://www.msha.gov under, ``Single Source Page for Metal and Nonmetal
Diesel Particulate Matter Regulations.'' Error factors are based on
sampling and analytic errors. The manufacturers of sampling devices
thoroughly investigate and quantify the error factors for their
devices. While MSHA does not frequently change an error factor, it
retains that latitude should significant changes to either analytical
or sampling technology occur.
The formula for the error factor was based on three factors
involved in making an eight-hour equivalent full-shift measurement of
EC concentration using NIOSH Method 5040: (1) Variability in air volume
(i.e., pump performance relative to the nominal airflow of 1.7 L/min);
(2) variability of the deposit area of particles on the filter
(cm2); and (3) accuracy of the laboratory analysis of EC
density within the deposit ([mu]g/cm2). Modifications made
to the sampler since the time of the 31-Mine Study have no bearing on
the first and third of these factors. Variability of the filter deposit
area was represented by a 3.1% coefficient of variation, based on an
experiment carried out before the foil filter capsule in the sampling
cassette was replaced by a 32-mm ring. Measurements subsequent to
introduction of the ring show that variability of the filter deposit
area is now less than 3.1% (Noll, J. D., et al, ``Sampling Results of
the Improved SKC Diesel Particulate Matter Cassette''). This change
slightly reduces the error factor stipulated for EC measurements, but
not by enough to be of any practical significance.
MSHA's error factor model accounts for the joint and related
variability in laboratory analysis, and combines that variability with
pump flow rate, sample collection size, and other sampling and analytic
variables. MSHA was then able to determine the appropriate error factor
for EC samples based on a statistically strong database.
The analytical method (NIOSH 5040) relies on a punch taken from
inside the deposit area on the sample filter. In effect, the punch is a
sample of the dust sample. To account for uniformity in the
distribution of DPM deposited on the filter, as reflected by different
possible locations at which a punch might be extracted, MSHA compared
two punches taken from different locations on the same filter to
evaluate the accuracy of the analytical method. Therefore, variability
between punch results due to their location on the filter is also
included in the error factor as calculated by MSHA.
Commenters to the 2003 NPRM further questioned whether the NIOSH
Method 5040 has been commercially tested. As in the preamble to the
2003 NPRM, MSHA has discussed in detail its findings regarding the
NIOSH Method 5040 in this section. NIOSH's peer review of the 31-Mine
Study also concludes that the analytical method specified by the diesel
standard gives an accurate measure of the TC content of a filter
sample. NIOSH confirmed this position by letter of February 8, 2002, in
which NIOSH stated that,
MSHA is following the procedures of NIOSH Method 5040, based on our
review of MSHA P13 (MSHA's protocol for sample analysis by NIOSH
Method 5040) and a visit to the MSHA laboratory.
V. Compliance Assistance
A. Baseline Sampling Summary
Under the second partial DPM settlement agreement, MSHA agreed to
provide compliance assistance to the M/NM underground mining industry
for a one-year period from July 20, 2002 through July 19, 2003. As part
of its compliance assistance activities, MSHA agreed to conduct
baseline sampling of miners' personal exposures at every underground
mine covered by the 2001 final rule.
Our baseline sampling began in October 2002 and continued through
October 2003. During this period a total of 1,194 valid baseline
samples were collected. A total of 183 underground M/NM mines are
represented by this analysis. The number of samples per mine range from
one to twenty. All 874 valid baseline sampling results in the analysis
published in the preamble of the 2003 NPRM are included in this updated
analysis. MSHA is including 320 additional valid samples because MSHA
decided to continue to conduct baseline sampling after July 19, 2003 in
response to mine operators' concerns. MSHA has analyzed all baseline
samples, and updated its analysis. Some of these mines were either not
in operation or were implementing major changes to ventilation systems
during the original baseline period. MSHA is including supplementary
samples from seasonal and intermittent mines, mines that were under-
represented, and mines that were not represented in the analysis
published in the preamble to the 2003 NPRM. Sixty mines included in the
former analysis had additional samples taken during the extended
assistance period. There are 12 mines in this updated analysis that
were not represented in the 2003 analysis. The results of this sampling
were used by MSHA in this preamble to estimate current DPM exposure
levels in underground M/NM mines using diesel equipment. These sampling
results also assist mine operators in developing compliance strategies
based on actual exposure levels.
This section summarizes analytical results of personal sampling for
DPM collected during compliance assistance. There are a total of 1,206
samples. However, 12 samples are invalid due to abnormal sample
deposits, broken cassettes or filters, contaminated backup pads,
instrument failure or pump failure. Table V-1 lists the frequencies of
invalid samples within each commodity.
The mines that were sampled produce clay, sand, gypsum, copper,
gold, platinum, silver, gem stones, dimension marble, granite, lead-
zinc, limestone, lime, potash, molybdenum, salt, trona, and other
miscellaneous metal or nonmetal ores. These commodities were grouped
into four general categories for calculating summary statistics: Metal,
stone, trona, and other nonmetal (N/M) mines. These categories were
selected to be consistent with the categories used for analysis of data
for the 31-Mine Study. Most commodities are well represented in this
analysis with the average number of valid samples per mine ranging from
6.0 to 8.2 (average across all mines is 6.5 samples per mine). The
average number of samples per mine classified as ``Gold Ore Mining,
N.E.C.'' increased from an average of 2.0 samples per mine published in
the 2003 NPRM preamble to an average of 4.6 samples in this data set.
Approximately 79% of all mines sampled during the assistance period
have four or more results from DPM sampling in this analysis. Table V-3
lists the number of samples for each category of specific commodity.
Average number of samples for more general commodity groups is listed
in Table V-2.
MSHA used the same sampling strategies for collecting baseline
samples as it intends to use for collecting samples for enforcement
purposes. These sampling procedures are described in the Metal and
Nonmetal Health Inspection Procedures Handbook (PH90-IV-4), Chapter A,
``Compliance Sampling Procedures'' and Draft Chapter T, ``Diesel
Particulate Matter Sampling.'' Chapter A includes detailed guidelines
for selecting and obtaining personal samples for various contaminants.
All personal samples were collected in the miner's breathing zone and
for the miner's full shift regardless of the number of hours worked.
For the 1,194 valid personal samples, 85% were collected for at least
eight hours. TC and EC levels, as well as DPM levels, are reported in
units of micrograms per cubic meter for an 8-hour full shift
MSHA collected DPM samples with SKC submicron dust samplers that
use Dorr-Oliver cyclones and submicron impactors. The samples were
analyzed either at MSHA's Pittsburgh Safety and Health Technology
Center, Dust Division Laboratory or at the Clayton Laboratory using
MSHA Method P-13 (NIOSH Analytical Method 5040, NIOSH Manual of
Analytical Methods (NMAM), Fourth Edition, September 30, 1999) for
determining the TC content. Each sample was analyzed for organic,
elemental, and carbonaceous carbon and calculated TC. Raw analytical
results from both laboratories as well as administrative information
about the sample were stored electronically in MSHA's Laboratory
Information Management System.
If a raw carbon result was greater than or equal to 30 [mu]g/
cm2 of EC or 40 [mu]g/cm2 of TC from the exposed
filter loading, then the analysis was repeated using a separate punch
of the same filter. The results of these two analyses were then
averaged. The companion tandem blank was also tested for the same
analyses. Otherwise, an unexposed filter from the same manufacturer's
lot was used to correct for background levels. In the event the initial
TC result was greater than 100TC [mu]g/cm2, a
smaller punch of the same exposed filter (in duplicate and with the
corresponding blank) was taken and used in the analysis. Blank-
corrected averaged results were used in the analysis when the sample
was tested in duplicate.
The equation used to calculate a 480-minute (8-hour) full shift
equivalent (FSE) exposure of TC is Total Carbon Concentration =
[GRAPHIC] [TIFF OMITTED] TR06JN05.014
EC = The corrected elemental carbon concentration measured in the
thermal/optical carbon analyzer, [mu]g/cm\2\,
OC = The corrected organic carbon concentration measured in the
thermal/optical carbon analyzer, [mu]g/cm\2\,
A = The surface area of the deposit on the filter media used to collect
the sample, cm\2\,
Flow Rate = Flow rate of the air pump used to collect the sample
measured in Liters per minute, and
480 minutes = Standardized eight-hour work shift.
All levels of carbon or DPM are reported in 8-hour full shift
equivalent TC concentrations measured in [mu]g/m\3\.
Because personal sampling was conducted and no attempt was made to
avoid interference from cigarette smoke or other OC sources, TC was
also calculated using the formula prescribed in the second partial DPM
Total Carbon Concentration = EC x 1.3.
MSHA agreed to use the lower of the two values (EC x 1.3 or EC +
OC) for enforcement until a final rule is published reflecting EC as
The electronic records of the 1,194 samples available for analysis
were reviewed for inconsistencies. Internally inconsistent or extreme
values were questioned, researched, and verified. Although no samples
were invalidated as a result of the administrative verification, 12
samples (1.0%) were removed from the data set for reasons unrelated to
the values obtained. The reasons for invalidating these samples are
listed in Table V-1. These samples were subjected to the same
laboratory quality assessments as samples collected for compliance
purposes. Accordingly, MSHA has included 1,194 samples from miners in
the analyses. Table V-2 is a list of the number of valid samples by
Table V-1.--Reasons for Excluding Samples.
Reason for excluding from analysis Metal Stone Trona Other N/M Total
Abnormal Sample Deposit........................ 0 1 0 0 1
Cassette/Filter Broken......................... 0 2 0 1 3
Contaminated Backup Pad........................ 1 0 0 0 1
Instrument Failure............................. 1 1 0 0 2
Pump Failed.................................... 1 4 0 0 5
Total...................................... 3 8 0 1 12
Table V-2.--Number of Mines and Valid Samples, by Commodity Group.
Average number of
Commodity group Number of mines Number of valid valid samples by
Metal.................................................. 40 284 7.1
Stone.................................................. 115 689 6.0
Trona.................................................. 4 25 6.3
Other N/M.............................................. 24 196 8.2
Total.............................................. 183 1,194 6.5
Table V-3 lists the number of samples collected by specific
commodities and sorted by average number of samples per mine. Although
MSHA made efforts to sample all underground M/NM mines covered by this
rulemaking within the specified time frame, several mines have few or
no samples for DPM in this analysis. Some M/NM mining operations are
seasonal in that they are operated intermittently or operate at less
than full production during certain times. These types of variable
production schedules limited efforts to collect compliance assistance
samples. MSHA extended its period of baseline sampling especially to
incorporate into its analysis those mines with a low sampling frequency
or where no samples were collected as of March 26, 2003.
Table V-3.--Number of Valid Samples per Mine for Specific Commodities
Specific commodity No. of mines No. of samples per
Gemstones Mining, N.E.C......................................... 2 5 2.5
Dimension Marble Mining......................................... 3 9 3.0
Limestone....................................................... 2 6 3.0
Talc Mining..................................................... 1 3 3.0
Uranium-Vanadium Ore Mining, N.E.C.............................. 1 3 3.0
Gold Ore Mining, N.E.C.......................................... 19 87 4.6
Construction Sand & Gravel Mining, N.E.C........................ 1 5 5.0
Crushed & Broken Sandstone Mining............................... 1 5 5.0
Hydraulic Cement................................................ 1 5 5.0
Lime, N.E.C..................................................... 4 20 5.0
Copper Ore Mining, N.E.C........................................ 2 11 5.5
Dimension Limestone Mining...................................... 3 18 6.0
Crushed & Broken Limestone Mining, N.E.C........................ 90 550 6.1
Crushed & Broken Marble Mining.................................. 4 25 6.3
Trona Mining.................................................... 4 25 6.3
Crushed & Broken Stone Mining, N.E.C............................ 4 28 7.0
Gypsum Mining................................................... 4 29 7.3
Salt Mining..................................................... 14 122 8.7
Clay, Ceramic & Refractory Minerals, N.E.C...................... 1 9 9.0
Miscellaneous Metal Ore Mining, N.E.C........................... 1 9 9.0
Lead-Zinc Ore Mining, N.E.C..................................... 10 96 9.6
Platinum Group Ore Mining....................................... 2 20 10.0
Potash Mining................................................... 3 30 10.0
Molybdenum Ore Mining........................................... 2 22 11.0
Silver Ore Mining, N.E.C........................................ 3 36 12.0
Miscellaneous Nonmetallic Minerals, N.E.C....................... 1 16 16.0
Average of all samples...................................... 183 1,194 6.5
There are 63 different occupations in underground M/NM mines
represented in this analysis. The most frequently sampled occupations
are Blaster, Drill Operator, Front-end Loader Operator, Truck Driver,
Scaling (Mechanical), and Mechanic. Table V-4 lists the number of valid
samples by occupation and commodity group. Only occupations with 14 or
more total samples are listed individually. Occupations with fewer
samples were aggregated into a combined group for this table.
Table V-4.--Valid Samples, by Occupation and Mine Category.
Occupation Metal Stone Trona Other N/M Total
Truck Driver................................... 87 152 0 13 252
Front-end Loader Operator...................... 40 149 6 19 214
Blaster, Powder Gang........................... 12 98 0 24 134
Scaling (mechanical)........................... 1 66 0 13 80
Drill Operator, Rotary......................... 3 63 0 9 75
Drill Operator, Jumbo Perc..................... 10 19 0 9 38
Mechanic....................................... 7 15 0 12 34
Complete Load-Haul-Dump........................ 7 2 0 23 32
Utility Man.................................... 6 4 15 4 29
Scaling (hand)................................. 4 20 0 2 26
Mucking Mach. Operator......................... 19 1 0 3 23
Roof Bolter, Rock.............................. 5 9 0 7 21
Drill Operator, Rotary Air..................... 1 19 0 1 21
Miner, Drift................................... 16 1 0 0 17
Crusher Oper/Worker............................ 0 13 0 2 15
Miner, Stope................................... 14 0 0 0 14
All Others Combined............................ 52 58 4 55 169
Totals..................................... 284 689 25 196 1,194
TC levels calculated by EC x 1.3 were lower than TC levels
calculated by OC + EC in 858 (72%) of the 1,194 baseline samples. Of
the 336 samples where TC = OC + EC was the lower value, 68% of the TC =
EC x 1.3 values were within 12% of the TC = OC + EC value. Table V-5
summarizes the results of the baseline samples when determining the TC
level using either EC x 1.3 or OC + EC. Approximately 6.4% of the
paired results did not concur with respect to the 400TC
[mu]g/m\3\ standard when measuring TC by the two calculations (OC + EC
vs. EC x 1.3). Approximately 19.3% of the samples were above the
400TC [mu]g/m\3\ interim concentration limit when using TC =
EC x 1.3 and approximately 22.7% were above the concentration limit
when using TC = OC + EC. There is 93.6% concurrence between the two
methods of calculating TC and comparing the calculations to the
400TC [mu]g/m\3\ interim concentration limit.
Table V-5.--Comparison of Results With 400TC [mu]g/m3 Calculating TC by OC + EC or EC x 1.3
EC x 1.3
All valid samples < 400TC [mu]g/ > 400TC [mu]g/ Total
< 400TC [mu]g/m\3\.......................................... 905 18 923
(75.8%) (1.5%) (77.3%)
> 400TC [mu]g/m\3\.......................................... 59 212 271
(4.9%) (17.8%) (22.7%)
Total....................................................... 964 230 1,194
(80.7%) (19.3%) (100.0%)
Table V-6 lists the 26 occupations found to have at least one
sample in which the level of TC was over the 400TC [mu]g/
m\3\ interim concentration limit (TC = EC x 1.3). Table V-6 is sorted
by the median (middle) TC result. The median is reported because it is
a more robust measure of the middle value. Changing a single value
won't change the median very much. In contrast, the value of the mean
can be strongly affected by a single value that is very low or very high. The table also lists the minimum value, maximum value, and the total number of valid samples for these
occupations. TC values varied widely among all miners' occupations.
Table V-6.--Occupations With at Least One Sample Greater Than or Equal to 400TC [mu]g/m3 (TC = ECx 1.3)
Occupation Total -----------------------------------
samples Minimum Median Maximum
Diamond Drill Operator.......................................... 1 2,030 2,030 2,030
Ground Control/Timberman........................................ 2 368 545 722
Washer Operator................................................. 4 353 438 808
Engineer........................................................ 1 438 438 438
Roof Bolter, Mounted............................................ 12 98 335 1,063
Mucking Mach. Operator.......................................... 23 15 334 872
Miner, Stope.................................................... 14 100 283 622
Cleanup Man..................................................... 2 66 283 499
Scoop-Tram Operator............................................. 7 14 272 583
Drill Operator, Rotary Air...................................... 21 0 240 1,353
Miner, Drift.................................................... 17 16 228 1,459
Blaster, Powder Gang............................................ 134 6 227 1,340
Belt Crew....................................................... 8 26 225 502
Roof Bolter, Rock............................................... 21 63 223 1,310
Truck Driver.................................................... 252 0 211 1,581
Shuttle Car Operator (diesel)................................... 3 95 201 419
Complete Load-Haul-Dump......................................... 32 19 189 824
Drill Operator, Jumbo Perc...................................... 38 5 179 1,098
Drill Operator, Rotary.......................................... 75 3 171 1,109
Motorman........................................................ 8 59 168 419
Front-end Loader Operator....................................... 214 0 158 2,979
Scaling (mechanical)............................................ 80 0 139 1,246
Supervisor, Co. Official........................................ 13 1 130 856
Utility Man..................................................... 29 29 94 991
Scaling (hand).................................................. 26 18 87 2,013
Mechanic........................................................ 34 0 84 420
Table V-7 and Chart V-1 provide the percent of overexposures among
the four commodity groups. Chart V-2 provides the number of
overexposures among the four commodity groups. The metal mines have the
highest percent of overexposures followed by stone, then other non-
metal mines. For all samples combined, 19.3% were above
Table V-7.--Baseline Samples by Commodity (TC = EC x 1.3)
Commodity Number < 400TC Number > 400TC Total Samples 400TC [mu]g/
[mu]g/m\3\ [mu]g/m\3\ m\3\
Metal........................................... 195 89 284 31.3
Stone........................................... 571 118 689 17.1
Other N/M....................................... 174 22 196 11.2
Trona........................................... 24 1 25 4.0
All Mines....................................... 964 230 1,194 19.3
BILLING CODE 4510-43-U
[GRAPHIC] [TIFF OMITTED] TR06JN05.001
[GRAPHIC] [TIFF OMITTED] TR06JN05.002
Chart V-3 shows the number of mines with a specific number of
overexposures. Examination of the frequency of mines with one or more
overexposures shows that 68 mines (37%) are in this category. There
were no mines with more than 12 samples > 400TC [mu]g/m\3\
for that mine.
[GRAPHIC] [TIFF OMITTED] TR06JN05.003
At four of the mines, all samples taken during the assistance
period were above 400TC [mu]g/m\3\. Between one and ten
samples were taken at each of these four mines. No overexposures were
found in 115 (63%) of the mines sampled. (See Chart V-4.)
BILLING CODE 4510-43-C
[GRAPHIC] [TIFF OMITTED] TR06JN05.004
Tables V-8 and V-9 summarize sample statistics by commodity for TC
calculated by TC = EC x 1.3 and TC = EC + OC respectively. Overall, the
mean TC as calculated by EC x 1.3 is 255 [mu]g/m\3\. The median level
is 174 [mu]g/m\3\. The mean TC level by OC + EC is 293 [mu]g/m\3\ and
the median level is 226 [mu]g/m\3\. Individual exposure levels of TC
vary widely within all commodities and most mines. The commodity
groupings reported in Tables V-8 and V-9 were chosen to be consistent
with those reported in the 31-Mine Study and the Quantitative Risk
Assessment (QRA) for this rule.
The mean and median TC values for each group, using EC x 1.3, are
lower than the interim compliance limit of 400 [mu]g/m3. The
mean (median) TC value for metal mines is 356(271) [mu]g/m3.
The mean (median) for stone mines is 236(149), other non-metal mines is
194(148), and trona mines is 105(82) [mu]g/m3. Table V-8
lists additional statistics for TC values compiled by commodity.
Table V-8.--Average Levels of TC by Commodity Measured in [mu]g/m3 (EC x 1.3)
[Estimated 8-hour Full Shift Equivalent TC Concentration ([mu]g/m3)]
TC = EC x 1.3 Metal Stone Other N/M Trona All Mines
No. of Samples................................. 284 689 196 25 1,194
Maximum........................................ 2,026 2,979 960 407 2,979
Median......................................... 271 149 148 82 174
Mean........................................... 356 236 194 105 255
Std. Error................................. 19 10 12 16 8
95% CI Upper............................... 392 256 217 138 270
95% CI Lower............................... 319 216 172 73 239
The mean and median TC values for each group of mines as calculated
by OC + EC are also lower than the interim compliance limit of 400
[mu]g/m3. The mean (median) TC value for metal mines is
370(313) [mu]g/m3. The mean for stone mines is 282(209), other non-metal mines is 238(191) and for trona mines is 140(126) [mu]g/m3. Table V-9 lists additional
statistics for TC values compiled by commodity group.
Table V-9.--Average Levels of TC by Commodity Group Measured in [mu]g/m3 (OC + EC)
[Estimated 8-hour Full Shift Equivalent TC Concentration ([mu]g/m3)]
TC = OC + EC Metal Stone Other N/M Trona All Mines
No. of Samples................................. 284 689 196 25 1,194
Maximum........................................ 2,045 2,796 1,230 344 2,796
Median......................................... 313 209 191 126 226
Mean........................................... 370 282 238 140 293
Std. Error................................. 17 11 12 12 8
95% CI Upper............................... 404 303 263 165 308
95% CI Lower............................... 336 261 214 115 278
Tables V-10, V-11, and V-12 show summary statistics for whole DPM
exposures for the baseline sampling and the 31-Mine Study. For baseline
sampling whole DPM was calculated by EC x 1.3 x 1.25 and by (OC + EC) x
1.25. The 1.25 factor represents the assumption that TC comprises 80%
of whole DPM. The other 20% includes the solid aerosols such as ash
particulates, metallic abrasion particles, sulfates and silicates. The
vast majority of these particulates are in the sub-micron range.
Section VI-B discusses the relationship between EC and TC. For
whole DPM concentrations, the mean (median) value is 444(339) [mu]g/
m3 for metal mines, 295(186) for stone mines, 243(185) for
other non-metal mines, and 132(102) [mu]g/m3 for trona
mines. The whole DPM exposures for Table V-11 were calculated as (OC +
EC) x 1.25.
Table V-10.--Baseline Whole DPM Concentrations (EC x 1.3 x 1.25, [mu]g/m3), by Mine Category
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration ([mu]g/m3)]
DPM = EC x 1.3 x 1.25 Metal Stone Other N/M Trona All Mines
Number of Samples.............................. 284 689 196 25 1,194
Maximum........................................ 2,532 3,724 1,200 509 3,724
Median......................................... 339 186 185 102 218
Mean........................................... 444 295 243 132 318
Std. Error................................. 23 13 15 20 10
95% CI Upper............................... 490 320 272 173 338
95% CI Lower............................... 399 270 214 91 299
Table V-11.--Baseline Whole DPM Concentrations ((EC + OC) x 1.25, [mu]g/m 3), by Mine Category
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration ([mu]g/m3)]
DPM = (EC + OC) x 1.25 Metal Stone Other N/M Trona All Mines
Number of Samples.............................. 284 689 196 25 1,194
Maximum........................................ 2,556 3,495 1,538 430 3,495
Median......................................... 392 262 238 158 283
Mean........................................... 463 353 298 175 366
Std. Error................................. 21 13 16 15 10
95% CI Upper............................... 505 379 329 206 385
95% CI Lower............................... 421 327 267 144 347
The mean whole DPM concentration for metal and stone mines (as
measured by (EC + OC) x 1.25) was significantly lower during baseline
compliance assistance sampling than the levels measured during the 31-
Table V-12.--31-Mine Study Whole DPM Concentrations ([mu]g/m3) by Mine Category
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration ([mu]g/m3)]
DPM = (EC + OC) x 1.25 Metal Stone Other N/M Trona
Number of Samples........................................... 116 105 83 54
Maximum..................................................... 2,581 1,845 1,210 331
Median...................................................... 491 331 341 82
Mean........................................................ 610 466 359 94
Std. Error.............................................. 45 36 27 9
95% CI Upper............................................ 699 537 412 113
95% CI Lower............................................ 522 394 306 75
Chart V-5 compares the means from Tables V-10, V-11 and V-12. The
mines selected in the 31-Mine Study (Table V-12) were not randomly
selected, and the study is, therefore, not considered representative of
the underground M/NM mining industry. Additionally, the industry has
continued to change the diesel-powered fleet to low emission engines
that reduce DPM exposure. Workers inside equipment cabs were not
sampled during the 31-Mine Study due to possible interference from
cigarette smoke. During baseline compliance assistance sampling,
however, personal samples were taken on miners inside cabs.
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MSHA received several comments on the baseline sampling. Some
commenters stated that many mines were sampled in a manner that
rendered results exceedingly low and not representative of operating
conditions. Commenters also stated that the results of independent DPM
sampling conducted by operators indicate MSHA's results underestimate
DPM exposure. These commenters did not provide data or analyses from
mine operators' sampling programs to substantiate their claim.
MSHA compliance specialists collected baseline samples in the same
manner they have been instructed to use for collecting samples for
enforcement purposes. It is expected that personal exposure to DPM will
fluctuate due to variations in day to day operations in a mine.
Reported levels of DPM are representative of the exposures of the
highest risk miners identified during compliance assistance. In an
ideal situation, and with unlimited resources, every potentially
exposed miner would be individually sampled. It is not necessary or
practical, however, to sample all miners on a mine property in order to
evaluate personal exposures. Suspected and potential health hazards may
be reasonably and adequately evaluated by sampling the maximum risk
miner in a work area. The maximum risk miner is the one expected to
have the greatest exposure of all of the miners in the area. Other
miners in the same work area or area of common exposure sources may
reasonably be expected to experience lesser concentrations of
occupational hazards than the maximum risk miner. There may be more
than one maximum risk miner when activities, operations, and exposure
sources vary throughout the day. MSHA acknowledges that some samples
were not taken on the highest possible risk occupation at some mines.
As previously stated, we continued baseline sampling past the date of
July 19, 2003 in response to this concern.
A miner experiences high risk because of the location and type of
tasks performed relative to the source of the suspected hazard. The
miner's predicted environment or duties may change during the course of
the work shift. If the working conditions present during the exposure
assessment are not typical of the regular mining operation, the sample
results may not represent the typical exposure for that occupation.
Compliance specialists strive to characterize the higher exposure
levels during typical work shifts. The baseline samples are
representative of the conditions experienced on work shifts during the
defined compliance assistance period. MSHA has obtained the best
available information for characterizing recent activities at the relevant M/NM mines.
B. DPM Control Technology
MSHA participated in a number of compliance assistance activities
directed at improving sampling and assisting mine operators with
selecting and implementing appropriate DPM control technology. Some of
these activities were directed to either a segment of the mining
industry, or to the entire industry, while others were conducted on a
mine specific basis. In general, activities directed toward a large
number of mines included outreach programs, workshops, web site postings
and publications, while activities directed at an individual mine
included evaluation of a specific control technology, and review of the
technology in use by or available to a specific mine.
Regional DPM Seminars. During September and October, 2002, MSHA
conducted regional DPM seminars at the following locations: Ebensburg,
PA; Knoxville, TN; Lexington, KY; Des Moines, IA; Kansas City, MO;
Albuquerque, NM; Coeur d'Alene, ID; Green River, WY; and Elko, NV. MSHA
offered these full-day seminars free of charge in the major underground
M/NM mining regions of the country to facilitate attendance by key
mining industry personnel. The seminars covered the health effects of
DPM exposure, the history and specific provisions of the regulation,
DPM controls, DPM sampling, and the DPM Estimator, a computerized
program that calculates DPM concentration reduction.
NIOSH Diesel Emission and Control Technologies in Underground M/NM
Mines Workshops. MSHA participated in these two workshops in February,
2003 in Cincinnati, OH and March, 2003, in Salt Lake City, UT. The
workshops served several purposes. They provided technical
presentations and a forum for discussing control technology for
reducing exposure to particulate matter and gaseous emissions from the
exhaust of diesel-powered vehicles in underground mines. Additionally,
they intended to help mine managers, maintenance personnel, safety and
health professionals, and ventilation engineers select and apply
control technologies in their mines. Speakers, representing MSHA,
NIOSH, and several mining companies, provided ample time for questions
and in-depth technical discussion of issues raised by participants.
National Stone, Sand & Gravel Association (NSSGA)/MSHA DPM Sampling
Workshop. This three day seminar, hosted by the Rogers Group, Inc.'s
Jefferson County Stone and Underground in Louisville, Kentucky, was
held on December 11 through 13, 2002. On the first day, MSHA reviewed
DPM sampling procedures, and presented training on pump calibration,
sample train assembly and note taking. On the second day, participants
traveled to the Rogers Group Jefferson County Mine to conduct full
shift sampling on underground miners. Our technical support staff took
ventilation measurements and collected area samples to assess DPM
emissions in the mine. On the third day, MSHA reviewed engine emission
and ventilation measurements. Additionally, MSHA reviewed and discussed
DPM outreach material. Approximately 10 industry participants attended
Nevada Mining Association Safety Committee. In April, 2003, MSHA
discussed DPM control technologies at a meeting of the Nevada Mining
Association Safety Committee in Elko, NV. Discussion topics included
bio-diesel fuel blends, various fuel additives and fuel pre-treatment
devices, mine ventilation, environmental cabs, clean engines, and
diesel particulate filter (DPF) systems. Mining company representatives
discussed their experiences with and perspectives on these
technologies. MSHA discussed experiences and observations that it made
at various mines, and results of its laboratory and field testing.
MSHA South Central Joint Mine Safety and Health Conference. MSHA
presented a DPM workshop at this conference in April 2003, in New
Orleans, LA. The workshop included a detailed history and explanation
of the provisions of the DPM regulation, and a technical presentation
on feasible DPM engineering controls. At the April 2004 conference in
Albuquerque, NM, MSHA presented a review of DPM control strategies that
have generally been adopted in the underground M/NM mining industry.
National Meeting of the Joseph A. Holmes Safety Association,
National Association of State Mine Inspection and Training Agencies,
Mine Safety Institute of America, and Western TRAM (Training Resources
Applied to Mining). MSHA presented a DPM workshop at this conference in
June 2003, in Reno, NV. The workshop included a detailed history and
explanation of the provisions of the regulation, and a technical
presentation on DPM sampling, analytical tools for identifying and
evaluating DPM sources in mines, and feasible DPM engineering controls.
DPM Sampling and Control Workshops. In March 2004, MSHA presented
full one day workshops in Bloomington, IN and Des Moines, IA. In these
workshops, MSHA reviewed the sampling procedures that MSHA inspectors
would use for DPM, and MSHA provided hands on instruction to the
participants in these procedures. MSHA also presented a review of DPM
control strategies that have generally been adopted in the underground
M/NM mining industry.
Equipment Manufacturers Association (EMA) DPM Workshop. In August
2003, MSHA conducted a DPM workshop for the EMA in Chicago, IL. At this
workshop, MSHA reviewed the M/NM DPM regulations, discussed the need
for clean engine technology, explained engine emission testing for
mines, reviewed the importance of environmental cabs and discussed
Web site. Our Web site, http://www.msha.gov, contains a single source page
for DPM rules for M/NM mines. The page has links to specific topics,
Draft Metal and Nonmetal Health Inspection Procedures
Handbook, Chapter T--Diesel Particulate Matter Sampling.
DRAFT Diesel Particulate Matter Sampling Field Notes.
Metal and Nonmetal Diesel Particulate Matter Standard
Error Factor for TC Analysis.
MSHA Metal and Nonmetal DPM Standard Compliance Guide of
August 5, 2003, addressing the interim DPM limit.
MSHA-NIOSH Diesel Particulate Filter Selection Guide for
Diesel-powered Equipment in Metal and Nonmetal Mines (Filter Selection
Guide), last updated February 20, 2003.
Baseline DPM Sample Results, updated October 2003.
Presentation from Compliance Assistance Workshop, October
Summary of Requirements: MSHA Standard on Diesel
Particulate Matter Exposure of Underground Metal and Nonmetal Miners
that are in effect as of July 20, 2002.
Link to SKC Web site: SKC Diesel Particulate Matter
Cassette with Precision-jeweled Impactor.
Diesel Particulate Matter Control Technologies, last
updated January 14, 2004.
--Table I: Paper/Synthetic Filters.
--Table II: Non-Catalyzed Particulate Filters, Base Metal Particulate
Filters, Specially Catalyzed Particulate Filters, and High Temperature
--Table III: Catalyzed (Platinum Based) Diesel Particulate Filters.
Work Place Emissions Control Estimator.
Federal Register documents concerning this and prior DPM
Public comments on this rulemaking.
Economic analyses for this rule and prior DPM rules.
MSHA News Release: MSHA Rules Will Control Miners'
Exposure to Diesel Particulate, January 18, 2001.
Program Information Bulletins:
--PIB01-10 Diesel Particulate Matter Exposure of Underground Metal and
Nonmetal Miners, August 28, 2001.
--PIB02-04 Potential Health Hazard Caused by Platinum-Based Catalyzed
Diesel Particulate Matter Exhaust Filters, May 31, 2002.
--PIB02-08 Diesel Particulate Matter Exposure of Underground Metal and
Nonmetal Miners---Summary of Settlement Agreement, August 12, 2002.
Additionally, our diesel single source page for the coal industry
contains topics that may also be of interest to the M/NM mining
industry, particularly for those operations at gassy mines where
permissible equipment is required.
Specific control technology studies. Following the settlement
agreement, MSHA was invited by various mining companies to evaluate the
effectiveness of different control technologies for DPM, including
ceramic filters, alternative fuels and a fuel oxygenator. Company
participation was essential to the success of each test. MSHA evaluated
ceramic filters in two mines, one where MSHA was the only investigator
and one where NIOSH was the primary investigator. In our test, MSHA
evaluated DPM on a production unit with and without ceramic filters
installed on the loader and trucks. In the NIOSH study a variety of
ceramic filters were tested in an isolated zone.
MSHA evaluated bio-diesel fuel in two mines. In one, MSHA evaluated
a 20% and a 50% recycled bio-diesel fuel and a 50% new bio-diesel. In
the other, MSHA evaluated a 35% recycled bio-diesel fuel and a 35% new
MSHA evaluated the fuel catalyst system in one mine. MSHA sampled
the mine exhaust with fuel catalyst systems installed on all production
equipment, and also without the units installed.
MSHA evaluated water emulsion diesel fuel in four mines.
Following is a summary of the individual mine technology evaluation
Kennecott Greens Creek Mining Company: MSHA participated with
Kennecott Greens Creek Mining Company in a collaborative test to verify
the efficiency of catalyzed ceramic DPFs for reducing diesel
particulate emissions. The goal of the testing was to identify site-
specific practical mine-worthy filter technology.
This series of tests was designed to determine the reduction in
emissions and personal exposure that can be achieved when ceramic
filters are installed on a loader and associated haulage trucks
operating in a production stope. MSHA also determined relative engine
gaseous and DPM emissions for the equipment under specific load
MSHA conducted the tests over a two-week period. MSHA sampled three
shifts with ceramic after-filters installed; and three shifts without
the after-filters. MSHA also collected personal samples to assess
worker exposures, and area samples to assess engine emissions. MSHA
took both gaseous and diesel particulate measurements.
Sampling results indicate significant reductions in both personal
exposures and engine emissions. These results also indicated that
factors such as diesel particulate contamination of intake air, stope
ventilation parameters, and isolated atmospheres in vehicle cabs as
well as the ceramic DPFs may have a significant impact on personal
exposures. The following findings and conclusions were obtained from
1. The results of the raw exhaust gas measurements conducted during
the test indicate that the engines were operating properly.
2. The ceramic filters installed on the machines used in this test
do not adversely affect machine operation. Even with some apparent
visual cracking from the rotation of the filter media, the ceramic
filters removed more than 90% of the DPM. The filters passively
regenerated during machine operation.
3. The Bosch smoke test provides an indication of filter
deterioration; however, the colorization method does not quantify the
4. Personal DPM exposures were reduced by 60% to 68% when after-
filters were used.
5. CO levels decreased by up to one-half while the catalyzed
filters were used. There appeared to be an increase in NO2
(Nitrous Dioxide) while catalyzed filters were being used; however, it
is unclear whether this increase was due to data variability, changes
in ventilation rate, or the use of the catalyzed filters.
6. The use of cabs reduced DPM exposure by 75% when DPFs were in
use and by 80% when DPFs were not in use.
7. Ventilation airflow was provided to the stopes through fans with
rigid and bag tubing. Airflow was the same or greater than the
Particulate Index, but typically lower than the gaseous ventilation
8. The use of ceramic DPFs reduced average engine DPM emissions by
9. The reduction in personal exposure was not attributed solely to
DPF performance because other factors such as ventilation, upwind
equipment use, and cabs also influence personal exposure.
Carmeuse North America, Inc., Maysville Mine: MSHA entered into a
collaborative effort with NIOSH, industry, and the Kentucky Department
of Energy to test DPM emissions and exposures when using various blends
of bio-diesel fuels in an underground stone mine. As part of our
compliance assistance program, MSHA provided support to mining
operations to evaluate diesel particulate control technologies. The
test was initiated by the industry partner, and, along with NIOSH, MSHA
provided support for test design, data collection, and sample and data
analysis. The project was funded by Carmeuse and Kentucky Department of
Energy, through the Kentucky Clean Fuels Coalition.
The initial test was conducted in two phases, using a 20% and a 50%
bio-diesel blend of recycled vegetable oil (RVO), each mixed with low
sulfur No. 2 standard diesel fuel. Baseline conditions were established
using low sulfur No. 2 standard diesel fuel. In a third phase of the
test, a 50% blend of new soy bio-diesel fuel was tested.
Area samples were collected at shafts to assess equipment
emissions. Personal samples were collected to assess worker exposure.
These samples were analyzed by NIOSH using the NIOSH 5040 method to
determine TC and EC concentrations. Results indicate that significant
reductions in emissions and worker exposure were obtained for all bio-
diesel mixtures. These reductions were in terms of both elemental and
TC. Results for the 20% and 50% RVO indicated 33% and 69% reductions in
DPM emissions, respectively. Results for the tests on the 50% blend of
new soy bio-diesel fuel, showed about a 37% reduction in DPM emissions.
Carmeuse North America, Inc., Black River Mine: Following the
success of the bio-diesel tests at Maysville Mine, Carmeuse requested
our assistance in continuing the bio-diesel optimization testing at
their Black River Mine. Two bio-diesel blends were tested, and a
baseline test was made. In each test personal exposures and the mine
exhaust were tested for two shifts. The two bio-diesel blends included a
35% RVO and a 35% blend of new soy oil. Results for the 35% RVO
showed a 32% reduction in DPM emissions.
Results of the 35% blend of new soy bio-diesel fuel showed an
approximate 16% reduction in DPM emissions.
Stone Creek Brick Company, Water Emulsion Fuel Tests: During the
Stone Creek Brick Company compliance assistance visit, MSHA identified
several control strategies that would reduce DPM emissions and
exposures. These strategies included: The installation of clean
engines, the use of alternative fuels, and an increase in mine
ventilation. The mine chose to implement alternative fuel use followed
by an engine replacement program. MSHA provided in-mine testing to
evaluate the impact of using an alternative fuel. The company chose to
use a water emulsion fuel. This fuel is an EPA approved fuel,
consisting of a 20% blend of water with No. 2 diesel fuel. A surfactant
is added to keep the water and diesel fuel from separating. MSHA
sampled at the mine before (using No. 2 diesel fuel) and after the
implementation of the fuel. MSHA collected personal samples to evaluate
the worker exposure and area samples to evaluate emissions.
Results of the testing showed that the highest exposure was reduced
from 823TC [mu]g/m3 to 321TC [mu]g/
m3 (61% reduction). EC emissions were reduced by 49% and TC
emissions were reduced by 3%. The lack of a reduction in TC emissions
was attributed to the lower combustion temperature resulting from the
water emulsion fuel and the older engine technology in use. The older
engines have larger injector nozzles which do not provide efficient
fuel burning. The mine has been using the fuel for approximately one
year, and continues to be satisfied with the results.
Carmeuse North American, Inc., Maysville Mine, Water Emulsion Fuel
Tests: MSHA provided assistance to Carmeuse North American, Inc., to
evaluate summer and winter blends of a water emulsion fuel at their
Maysville Mine. For the first test, emission reductions for a 10% blend
(winter blend) of water with No. 2 diesel fuel was compared to a 35%
blend of RVO. Emission reductions were compared to both a 35% blend of
RVO and standard No. 2 diesel fuel. MSHA collected personal samples to
evaluate the worker exposure and area samples to evaluate emissions.
Results of the testing showed that the highest average exposure
(high scaler working outside a cab) was reduced from 254TC
[mu]g/m3 to 145TC [mu]g/m3 (43%
reduction) when changing from RVO to the water emulsion. EC emissions
were reduced by 52% and TC emissions were reduced by 49% for the water
emulsion to 35% RVO fuel comparison. EC emissions were reduced by 77%
and TC emissions were reduced by 74% for the water emulsion to standard
diesel fuel comparison.
For the second test, emission reductions for a 20% blend (summer
blend) of water with No. 2 diesel fuel was compared to a 35% blend of
RVO. Emission reductions were compared to both a 35% blend of RVO and
standard No. 2 diesel fuel. The comparison to No. 2 diesel fuel was
obtained by combining the water emulsion to the 35% RVO results and
previously obtained 35% RVO to No. 2 diesel fuel results. MSHA
collected personal samples to evaluate the worker exposure and area
samples to evaluate emissions. For the summer blend, EC emissions were
reduced by 60% and TC emissions were reduced by 59% for the water
emulsion to 35% RVO fuel comparison. EC emissions were reduced by 81%
and TC emissions were reduced by 79% for the water emulsion to standard
diesel fuel comparison.
Carmeuse North American, Inc., Black River Mine, Water Emulsion
Fuel Tests: MSHA provided assistance to Carmeuse North American, Inc.
to evaluate summer and winter blends of a water emulsion fuel at their
Black River Mine. For these tests, emission reductions for 10% and 20%
blends (winter blend) of water with No. 2 diesel fuel was compared to a
35% blend of RVO. Emission reductions were compared to both a 35% blend
of RVO and standard No. 2 diesel fuel. MSHA collected personal samples
to evaluate the worker exposure and area samples to evaluate emissions.
For the winter blend (10%), EC emissions were reduced by 46% and TC
emissions were reduced by 45% for the water emulsion to 35% RVO fuel
comparison. EC emissions were reduced by 63% and TC emissions were
reduced by 62%, for the water emulsion to standard No. 2 diesel fuel
For the summer blend (20%), EC emissions were reduced by 61% and TC
emissions were reduced by 54% for the water emulsion to 35% RVO fuel
comparison. EC emissions were reduced by 73% and TC emissions were
reduced by 68% for the water emulsion to standard diesel fuel
Martin Marietta, Durham Mine, Water Emulsion Fuel Tests: MSHA
provided assistance to Martin Marietta to evaluate a summer blend of
water emulsion fuel at their Durham Mine. This was a multi-level mine,
with a 15% ramp between levels. For this test, emissions for a 20%
blend of water with No. 2 diesel fuel was compared to standard No. 2
diesel fuel. MSHA collected personal samples to evaluate the worker
exposure and area samples to evaluate emissions. Even with the 15%
ramps, the loss in horsepower due to the fuel did not adversely effect
the mine operations.
Results of the testing showed that the highest average exposure
(powder crew working outside a cab) was reduced from 372TC
[mu]g/m\3\ to 54TC [mu]g/m\3\ (85% reduction) when changing
from No. 2 diesel fuel to the water emulsion. EC emissions were reduced
by approximately 80% for the water emulsion compared to standard
Rogers Group, Jefferson County Mine: MSHA was invited to this mine
to evaluate a fuel catalyst system that was installed in the fuel line
of the diesel equipment. The company had installed the units to
increase fuel economy, and sought to determine the effects of the units
on DPM. Prior to the units having been installed, MSHA had conducted
baseline sampling and had collected personal samples on production
workers and area samples in the mine exhaust airflow. After the units
were installed on loaders and trucks and the units had accumulated 100
hours of operation, sampling was repeated. Results indicated that the
use of the fuel catalyst had no measurable effect on either DPM
exposure or emissions.
Summary of DPM control technology: In addition to conducting
baseline sampling and providing assistance in developing DPM control
strategies at specific mines, MSHA assessed the effectiveness of
various DPM controls during and following the compliance assistance
period. These controls included alternative fuels, fuel oxygenators,
environmental cabs and ceramic DPFs. Alternative fuels evaluated
included various blends of bio-diesel fuels (including both Virgin Soy
Oil (VSO) and RVO), No. 1 diesel fuel, and water emulsion fuels.
The resulting reduction in DPM emissions for each of these controls
is given in Chart V-6. All reductions are compared to diesel emissions
with low sulfur No. 2 diesel fuel. All bio-diesel tests were conducted
at mines with relatively clean engines. The first water emulsion test
was conducted at a mine utilizing older engines. Subsequent water
emulsion tests were conducted at mines utilizing clean engines with
oxidation catalytic converters.
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Assistance for Developing Control Strategies
Martin Marietta Aggregates: MSHA provided compliance assistance
during full-day visits at the North Indianapolis Mine and the Parkville
Mine in March, 2003, and at the Kaskaskia Mine and the Manheim Mine in
May, 2003. MSHA reviewed each mine's DPM sampling history, current operating and
equipment maintenance practices, ventilation, diesel equipment
inventory, and steps taken to date and future plans to reduce DPM
exposures. MSHA discussed the full range of engineering controls,
demonstrated an exhaust temperature measurement and data logging
system, and presented a spreadsheet for using such data to select
appropriate filter systems. MSHA presented a simple approach for
measuring the effectiveness of cab air filtering and pressurization
systems, identified the highest DPM-emitting equipment (so future
equipment-specific DPM control efforts could be appropriately focused),
and discussed the likely effect of various ventilation system upgrades.
Rogers Group, Oldham County Mine: MSHA provided compliance
assistance at this mine during a full-day visit in November 2002. MSHA
conducted extensive DPM sampling at the mine, collecting both personal
exposure samples and area samples. Further, MSHA collected DPM samples
from both inside and outside of equipment cabs. No personal samples
exceeded 160TC [mu]g/m\3\. MSHA reviewed current operating
and equipment maintenance practices, ventilation, diesel equipment
inventory, and steps taken to date and future plans to reduce DPM
exposures. MSHA discussed the full range of engineering controls.
Results from this survey indicate the environmental cabs significantly
reduced the DPM exposure of equipment operators.
Rogers Group, Jefferson County Mine: MSHA provided compliance
assistance at this mine during a full-day visit in December 2002. MSHA
collected both personal exposure samples and area samples. The highest
personal sample, collected on the loader, was 468TC [mu]g/m
\3\. This loader was operated with the window open. MSHA reviewed
current operating and equipment maintenance practices, ventilation,
diesel equipment inventory, and steps taken to date and future plans to
reduce DPM exposures. Mechanical ventilation was provided for the mine.
MSHA discussed the full range of engineering controls, demonstrated an
exhaust temperature measurement and data logging system, and presented
a spreadsheet for using such data to select appropriate filter systems.
MSHA presented a simple approach for measuring the effectiveness of cab
air filtering and pressurization systems, identified the highest DPM-
emitting equipment (so future equipment-specific control efforts could
be appropriately focused), and discussed the likely effect of various
ventilation system upgrades.
Nalley and Gibson, Georgetown Mine: MSHA provided compliance
assistance at this mine during a full-day visit in May 2003. MSHA
reviewed current operating and equipment maintenance practices,
ventilation, diesel equipment inventory, and steps taken to date and
future plans to reduce DPM exposures. MSHA collected DPM samples to
assess improvements since the baseline sampling. At that time,
mechanical ventilation provided airflow to the mine. MSHA discussed the
full range of engineering controls, demonstrated an exhaust temperature
measurement and data logging system, and presented a spreadsheet for
using such data to select appropriate filter systems. MSHA presented a
simple approach for measuring the effectiveness of cab air filtering
and pressurization systems, identified the highest DPM-emitting
equipment (so future equipment-specific DPM control efforts could be
appropriately focused), and discussed the likely effect of various
ventilation system upgrades.
Stone Creek Brick Company: MSHA provided compliance assistance at
this mine during a full-day visit in May 2003. MSHA reviewed current
operating and equipment maintenance practices, ventilation, diesel
equipment inventory, and steps taken to date and future plans to reduce
DPM exposures. MSHA collected DPM samples from underground miners. The
mine was using mechanical ventilation. None of the equipment had
environmental cabs. MSHA discussed the full range of engineering
controls, presented a spreadsheet for using such data to select
appropriate filter systems, identified the highest DPM-emitting
equipment (so future equipment-specific DPM control efforts could be
appropriately focused), and discussed the likely effect of various
ventilation system upgrades.
Wisconsin Industrial Sand Co., Maiden Rock Mine: MSHA provided
compliance assistance at this mine during a full-day visit in May 2003.
MSHA reviewed the mine's current operating and equipment maintenance
practices, ventilation, diesel equipment inventory, and steps taken to
date and future plans to reduce DPM exposures. MSHA discussed the full
range of engineering controls, presented a spreadsheet for using such
data to select appropriate filter systems, and identified the highest
DPM-emitting equipment so future equipment-specific DPM control efforts
could be appropriately focused.
Gouverneur Talc Company, Inc., No. 4 Mine: MSHA provided compliance
assistance at this mine during a full-day visit in May 2003. DPM
samples were collected on underground workers. MSHA reviewed then
current operating and equipment maintenance practices, ventilation,
diesel equipment inventory, and steps taken to date and future plans to
reduce DPM exposures. MSHA discussed the full range of engineering
controls, demonstrated an exhaust temperature measurement and data
logging system, and presented a spreadsheet for using such data to
select appropriate filter systems. MSHA presented a simple approach for
measuring the effectiveness of cab air filtering and pressurization
systems, identified the highest DPM-emitting equipment (so future
equipment-specific control efforts could be appropriately focused), and
discussed the likely effect of various ventilation system upgrades.
Additional specific mine compliance assistance: Following the
initial baseline sampling period, MSHA compiled a list of mines having
at least one DPM sample which exceeded the 400TC [mu]g/m\3\
limit. Of the 183 mines sampled, approximately 69 mines had at least
one sample over the 400TC [mu]g/m\3\ interim TC limit. Of
the 69 mines with one or more overexposures, 44 used room and pillar
mining methods. These include stone mines, salt mines and a potash
mine. Of the 44 room and pillar mines, MSHA provided specific
compliance assistance to 36 of these mines (two mines were closed and
two mines declined assistance). Although trona mines use room and
pillar mining methods, they were not visited because they were in
compliance with the 400TC [mu]g/m\3\ limit. The remaining 15
mines with overexposures were multilevel metal mines using a variety of
stoping mining methods. Industry seminars were provided to assist these
Typically, the high risk workers in the mines visited were the face
workers that worked outside an environmental cab. Production loader and
truck operators had elevated exposures when they either did not have an
environmental cab or when the cab was not being properly maintained.
Additional high risk workers include the blasting crew, drillers, and
During each mine visit, DPM samples were collected unless the mine
had been recently sampled or the mine reported no additional DPM
controls had been implemented since MSHA's previous sampling was
conducted. The DPM controls, including engines, ventilation, cabs,
fuels and work practices, were reviewed with mine management. Specific
engine emission rates, mine ventilation rates, cab pressures and
work practices were determined. At some mines, a temperature trace of
an engine exhaust was made. The information was entered into a computer
spreadsheet model to assess the effect of control changes on DPM levels
and to assist the mine in developing a DPM control strategy.
Laboratory Compliance Assistance: In addition to the compliance
assistance field tests, our diesel testing laboratory has been working
with manufacturers to evaluate various types of DPM control
technologies. Certain of these technologies can be applied in either
underground M/NM or coal mines.
Evaluating paper/synthetic media as exhaust filters: MSHA has
evaluated paper/synthetic media as exhaust filters. These filters have
shown DPM removal efficiencies in excess of 90% in the laboratory when
tested on our test engine using the test specified in subpart E of part
7. The laboratory has tested approximately 20 different paper/synthetic
media from 10 different filter manufacturers. Although much of this
work is directed to underground coal mine applications for use on
permissible equipment, this technology is available for use on
permissible equipment that is used in underground gassy M/NM mines. In
addition, some underground coal mine operators have considered adding
exhaust heat exchanger systems to nonpermissible equipment in order to
use the paper/synthetic filters in place of ceramic filters. The heat
exchanger is needed to reduce the exhaust gas temperature to below
302[deg] F for these types of filters. This could also be an option for
equipment in M/NM mines, particularly gassy mines where permissible
equipment is required.
Evaluating Ceramic Filter Systems: MSHA worked with six ceramic
filter manufacturers to evaluate the effects of their catalytic wash-
coats on NO2 production. As discussed under the
``Effectiveness of the DPM Estimator'' portion of this preamble,
catalytic wash-coats on the ceramic filters may cause increases in
NO2 levels. MSHA used our test engine (Caterpillar 3306
PCNA) and followed the test procedures in subpart E of 30 CFR part 7.
The DPM single source webpage lists the ceramic filters that have
significantly increased NO2 levels, as well as the ceramic
filters that are not known to increase NO2 levels. MSHA
tested the DPM removal efficiencies of these filters during the
laboratory tests. The efficiency results agree with the efficiencies
posted on our web site DPM Control Technologies with Percent Removal
Efficiency page (85% for cordierite and 87% for silicon carbide).
Finally, MSHA worked with NIOSH during these tests to collect DPM
samples for EC analysis using the NIOSH 5040 method. The laboratory
results showed that the filters removed EC at up to 99% efficiency.
Evaluation of Fuel Oxygenator System: MSHA'S laboratory completed
tests on the Rentar \TM\ in-line fuel catalyst. The Rentar \TM\ unit
was installed on a Caterpillar\TM\ 3306 ATAAC, which was coupled to a
generator. MSHA used an electrical load bank to load the engine under
various operating conditions. To establish a baseline, MSHA tested the
engine for gaseous and DPM emissions without the Rentar \TM\ unit. The
unit was then installed, and MSHA operated the engine for a 100 hour
break-in period. MSHA then repeated the gaseous and DPM emission
measurements. The test results of the one laboratory evaluation for
this control device to date showed no significant reductions in whole
diesel particulate, however, the data did not show any adverse effects
on the raw whole DPM exhaust emission. NIOSH's results were consistent
with MSHA's results, and showed no significant EC reductions and no
adverse effects on the engine's emissions. MSHA has discussed with
Rentar \TM\ further laboratory tests.
Evaluation of a Magnet System: MSHA performed laboratory tests for
Ecomax, a manufacturer of a magnet system installed on the fuel line,
oil filter, air intake and radiator. MSHA performed a preliminary field
test of this product at a surface aggregate operation. The magnetic
device demonstrated a 30% reduction in CO levels. The laboratory tests
were performed with the Ecomax system installed and compared to our
baseline engine data. The test results of the one laboratory evaluation
for this control device to date showed no significant reductions in
whole diesel particulate, however, the data did not show any adverse
effects on the raw DPM exhaust emissions.
Evaluation of the Fuel Preporator [reg] System: MSHA's
laboratory tested a fuel preparator system. The system is designed to
remove collected air from the fuel system for better fuel combustion.
The results of the system installed were compared to the baseline
engine. The test results of the one laboratory evaluation for this
control device to date showed no significant reductions in whole diesel
particulate, however, the data did not show any adverse effects on the
raw DPM exhaust emissions. NIOSH also conducted tests in our lab on the
Fuel Preporator [reg] and the results were consistent with
MSHA's results. There were no significant EC reductions and no adverse
effects on the engine's emissions.
VI. DPM Exposures and Risk Assessment
In support of the 2001 final rule, MSHA published a comprehensive
risk assessment (66 FR at 5752-5855, with corrections at 35518-35520).
In the following discussion, we will refer to the risk assessment
published in conjunction with the 2001 final rule as the ``2001 risk
The 2001 risk assessment presented MSHA's evaluation of health
risks associated with DPM exposure levels encountered in the mining
industry. This was based on a review of the scientific literature
available through March 31, 2000, along with consideration of all
material submitted during the applicable public comment periods.
The 2001 risk assessment was divided into three main sections.
Section 1 (66 FR at 5753-5764) contained a discussion of U.S. miner
exposures based on field data collected through mid-1998. An important
conclusion of this section was that, prior to the 2001 final rule,
* * * median dpm concentrations observed in some underground mines
are up to 200 times as high as mean environmental exposures in the
most heavily polluted urban areas [footnote deleted] and up to 10
times as high as median exposures estimated for the most heavily
exposed workers in other occupational groups. [66 FR at 5764]
Section 2 of the 2001 risk assessment (66 FR at 5764-5822) reviewed
the available scientific literature on health effects associated with
DPM exposures. This review covered effects of both acute and chronic
exposures and also contained a discussion of potential mechanisms of
toxicity. The review of acute effects included anecdotal reports of
symptoms experienced by exposed miners, studies based on exposures to
diesel emissions, and studies based on exposures to particulate matter
in the ambient air. The review of chronic effects included studies
based specifically on exposures to diesel emissions and studies based
more generally on exposures to fine particulate matter in the ambient
air. As part of this discussion, MSHA evaluated 47 epidemiologic
studies examining the prevalence of lung cancer within groups of
workers occupationally exposed to DPM and discussed the criteria used
to evaluate and rank these studies (66 FR at 5774-5810). For both acute
and chronic health effects, information from genotoxicity studies and studies
on laboratory animals was discussed in the separate subsection on mechanisms
of toxicity. Section 2 of the 2001 risk assessment also explained MSHA's rationale
for utilizing certain types of information whose relevance had been questioned during
the public comment periods: health effects observed in animals, health
effects that are reversible, and health effects associated with fine
particulate matter in the ambient air (66 FR at 5765-55767).
In section 3 of the 2001 risk assessment (66 FR at 5822-5855), MSHA
evaluated the best available evidence to ascertain whether exposure
levels currently existing in mines warranted regulatory action pursuant
to the Mine Act. To do this, MSHA addressed three questions: (a)
Whether health effects associated with occupational DPM exposures
constitute a ``material impairment'' to miner health or functional
capacity; (b) whether exposed miners were at significant excess risk of
incurring any of these material impairments; and (c) whether the 2001
final rule would substantially reduce such risks. After careful
consideration of all the submitted public comments, the 2001 risk
assessment established three main conclusions:
1. Exposure to dpm can materially impair miner health or
functional capacity. These material impairments include acute
sensory irritations and respiratory symptoms (including allergenic
responses); premature death from cardiovascular, cardiopulmonary, or
respiratory causes; and lung cancer.
2. At dpm levels currently observed in underground mines, many
miners are presently at significant risk of incurring these material
impairments due to their occupational exposures to dpm over a
3. By reducing dpm concentrations in underground mines, the rule
will substantially reduce the risks of material impairment faced by
underground miners exposed to dpm at current levels.
The third of these conclusions was supported primarily by a
quantitative risk assessment for lung cancer (66 FR at 5848-5854).
Throughout the current rulemaking, MSHA advised the mining
community of its intent to include the 2001 risk assessment in the
current rulemaking record to support this final rule. In this preamble,
MSHA supplements the 2001 risk assessment with new exposure data and
health effects literature published after March 31, 2000. MSHA asked
that public comment be focused on this supplemental information.
Nevertheless, some commenters presented critiques challenging the 2001
risk assessment and disputing scientific support for any DPM exposure
limit, especially by means of an EC surrogate. Other commenters
endorsed the 2001 risk assessment and stated that recent scientific
publications support MSHA's conclusions.
MSHA also received a number of comments from the mining industry
suggesting that the risk assessment lacks an adequate scientific
foundation and does not comply with present requirements under OMB and
information quality guidelines to use the best available, peer reviewed
science. The risk assessment sustaining this final rule uses the best
available, peer-reviewed scientific studies. It supplements the risk
assessment sustaining the 2001 final rule and the existing coal DPM
final rule also promulgated on January 19, 2001 (66 FR 5526) (coal
rule). The coal rule was unchallenged by the mining community.
Before promulgating the 2001 final rule, MSHA provided a copy of
its draft risk assessment supporting the 2001 rule for peer review to
two experts in the field of epidemiology and risk assessment. These
experts evaluated the overall methodology used by MSHA in the draft
risk assessment, the appropriateness of the studies selected by MSHA,
and MSHA's conclusions. MSHA had the draft independently peer-reviewed,
published the evidence and tentative conclusions for public comment,
and incorporated the reviewers' recommendations in the final version.
In the 2001 risk assessment, MSHA carefully laid out the best available
evidence, including shortcomings inherent in that evidence.
Of particular note is that the two quantitative meta-analyses of
lung cancer studies supporting the 2001 risk assessment were peer
reviewed and published in scientific journals. (Bhatia, Rajiv, et al.,
``Diesel Exhaust Exposure and Lung Cancer,'' Journal of Epidemiology,
9:84-91, January 1998, and Lipsett M., and Campleman, Susan,
``Occupational Exposure to Diesel Exhaust and Lung Cancer: A Meta-
Analysis,'' American Journal of Public Health, (89) 1009-1017, July
MSHA informed the public as early as September 25, 2002, in the
2002 ANPRM for this final rule, and again in the 2003 NPRM, that MSHA
would incorporate the existing rulemaking record, including the 2001
risk assessment, into the record of this rulemaking. MSHA was open to
considering any new scientific evidence relating to its risk
assessment. Commenters were encouraged in the instant rulemaking to
submit additional evidence of new scientific information related to
health risks associated with exposure to DPM. After considering both
the more recent scientific literature and all of the submitted
comments, MSHA has concluded that no change is warranted in the 2001
risk assessment's conclusions with respect to health risks associated
with DPM exposures.
Section VI.B updates Section 1 of the 2001 risk assessment by
summarizing the new exposure data that became available after
publication of the 2001 final rule. This summary includes a description
of the relationship between EC and TC observed in these exposure
measurements, and addresses public comments on possible health
implications of substituting EC for TC as a surrogate measure of DPM.
In Section VI.C, MSHA reviews some of the more recent scientific
literature (April 2000-March 2003) pertaining to adverse health effects
of DPM and fine particulates in general. In addition, this section
updates the 2001 risk assessment's discussion of scientific evidence on
mechanisms of DPM toxicity. Thus, Section VI.C supplements Section 2 of
the 2001 risk assessment. Section VI.C also discusses a document by Dr.
Gerald Chase that purports to analyze preliminary data extracted from
an ongoing NIOSH/NCI study. Finally, in Section VI.D, MSHA assesses
current risk to underground M/NM miners in light of the most recent
exposure and health effects information. Section VI.D also responds to
a critique of the 2001 risk assessment submitted by Dr. Jonathan Borak
on behalf of the MARG Diesel Coalition (MARG) and the NMA.
B. DPM Exposures in Underground M/NM Mines
In Section 1 of the 2001 risk assessment, MSHA evaluated exposures
based on 355 samples collected at 27 underground U.S. M/NM mines prior
to promulgating the 2001 rule. Mean DPM concentrations found in the
production areas and haulageways at those mines ranged from about 285
[mu]g/m\3\ to about 2000 [mu]g/m\3\, with some individual measurements
exceeding 3500 [mu]g/m\3\. The overall mean DPM concentration was 808
[mu]g/m\3\. All of the samples considered in the 2001 risk assessment
were collected prior to 1999, and some were collected as long ago as
Two new bodies of DPM exposure data, collected after promulgation
of the 2001 final rule, have now been compiled for underground M/NM
mines: (1) Data collected in 2001 and 2002 from 31 mines for purposes
of the 31-Mine Study and (2) data collected between 10/30/2002 and 10/
29/2003 from 183 mines to establish a baseline for future samples. Key
results from these two datasets are summarized in the next two subsections
below. Following these summaries, the relationship between EC and TC,
including the ratio of EC to TC (EC:TC) is discussed. This discussion is based
exclusively on samples taken for the 31-Mine Study, since those samples were
controlled for potential TC interferences from tobacco smoking and oil mist, whereas
the baseline samples were not. The subsection concludes with a response to comments
on the potential health effects of substituting EC for TC as a surrogate measure of DPM.
It should be noted that the new exposure data reflect conditions at
least two years, and up to five years, later than the most recent
miners' exposure data considered in the 2001 risk assessment.
Furthermore, all of the new exposure data were obtained after
promulgation of the 2001 rule. It is, therefore, reasonable to expect
that the data discussed below would show generally different exposure
levels than those presented in the 2001 risk assessment--both on
account of normal technological changes over time and because of DPM
controls that may have been implemented in response to the 2001 rule.
(1) Data from 31-Mine Study
MSHA collected 464 DPM samples in 2001 and 2002 at 31 underground
M/NM mines. (For a more detailed description, see MSHA's final report
on the 31-Mine Study.) Of these 464 samples, 106 were voided--mostly
because of potential interference by sources of OC other than DPM.
Table VI-1 shows how the remaining 358 valid DPM samples were
distributed across four broad mine categories. All samples at one of
the metal mines were voided, leaving 30 mines with valid samples
indicating DPM concentrations.
Table VI-1.--Number of DPM Samples, by Mine Category
Number of mines Avg. number of
with valid Number of valid valid samples per
samples samples mine
Metal.................................................. 11 116 10.5
Stone.................................................. 9 105 11.7
Trona.................................................. 3 54 18.0
Other.................................................. 7 83 11.9
Total.............................................. 30 358 12.5
Table VI-2 summarizes the valid DPM concentrations observed in each
mine category, assuming that submicrometer TC, as measured by the SKC
sampler, comprises 80% of all DPM. The mean concentration across all
358 valid samples was 432 [mu]g/m\3\ (Std. error = 21.0 [mu]g/m\3\).
The mean concentration was greatest at metal mines, followed by stone
and ``other.'' At the three trona mines sampled, both the mean and
median DPM concentration were substantially lower than what was
observed for the other categories. This was due to the increased
ventilation used at these mines to control methane emissions.
Table VI-2.--DPM Concentrations ([mu]/m\3\), By Mine Category
[DPM Is Estimated by TC / 0.8]
Metal Stone Trona Other
No. of samples.............................. 116 105 54 83
Minimum..................................... 46. 16. 20. 27.
Maximum..................................... 2581. 1845. 331. 1210.
Median...................................... 491. 331. 82. 341.
Mean........................................ 610. 465. 94. 359.
Std. Error.............................. 44.7 36.0 9.4 26.6
95% UCL................................. 699. 537. 113. 412.
95% LCL................................. 522. 394. 75. 306.
After adjusting for differences in sample types and in occupations
sampled, DPM concentrations at the non-trona mines were estimated to be
about four to five times the concentrations found at the trona mines.
Although there were significant differences between individual mines,
the adjusted differences between the general categories of metal,
stone, and other mines were not statistically significant.\1\ For the
304 valid samples taken at mines other than trona, the mean DPM
concentration was 492 [mu]g/m\3\ (Std. error = 23.0 [mu]g/m\3\).
\1\ These conclusions derive from an analysis of variance, based
on TC measurements, described in the Report on the 31-Mine Study.
They depend on an assumption that the ratio of DPM to TC is
uncorrelated with mine category, sample type (i.e., personal or
area), and occupation.
Again assuming that submicrometer TC as measured by the SKC sampler
comprises 80% of DPM, the mean DPM concentration observed was 1019
[mu]g/m\3\ at the single mine exhibiting greatest DPM levels. Four of
the nine valid samples at this mine exceeded 1487 [mu]g/m\3\. In
contrast, DPM concentrations never exceeded 500 [mu]g/m\3\ at 8 of the
30 mines with valid samples (2 of the 11 metal mines, 1 of the 3 stone,
all 3 trona, and 2 of the 7 others). (Note that 500 [mu]g/m\3\ is the
whole particulate equivalent of the 400TC [mu]g/m\3\ interim
limit.) Some individual measurements exceeded 200DPM [mu]g/
m\3\ at all but one of the mines sampled.
(2) Baseline Data
MSHA s baseline sampling results are presented in Section III,
Compliance Assistance. These results provide the basis for the present
discussion. The baseline samples discussed here, in connection with the
risk assessment, were collected and analyzed between October 30, 2002
and October 29, 2003. They comprise a total of 1,194 valid samples
collected from 183 mines. MSHA is including 320 additional valid samples
because MSHA decided to continue to conduct baseline sampling after
July 19, 2003 in response to mine operator's concerns. Some of these
mines were either not in operation or were implementing major changes
to ventilation systems during the original baseline period. MSHA is including
supplementary samples from seasonal and intermittent mines, mines that
were under-represented, and mines that were not represented in the analysis
published in the proposed preamble in 2003.
Table VI-3 summarizes, by general commodity, the EC levels measured
during MSHA's baseline sampling through October 29, 2003. The overall
mean eight-hour full shift equivalent EC concentration was 196 [mu]g/
m\3\, and the overall median was 134 [mu]g/m\3\. Table VI-4 provides a
similar summary for estimated DPM levels, using DPM [ap] TC/0.8 and TC
[ap] 1.3 x EC.\2\ Under these assumptions, the estimated mean DPM level
was 318 [mu]g/m\3\, and the median was 218 [mu]g/m\3\. Since the
baseline data and the 31-Mine Study both showed significantly lower
levels at trona mines than at other underground M/NM mines, Tables VI-3
and VI-4 present overall results both including and excluding the three
underground trona mines sampled.\3\
\2\ The relationship DPM [ap] TC/0.8 is the same as that assumed
in the 2001 risk assessment. The relationship TC 1.3 x EC was
formulated under the settlement agreement, based on TC:EC ratios
observed in the joint 31-Mine Study, as described in the subsection
VI.3 of this preamble.
\3\ The distributions of EC values are skewed. Therefore, the
standard errors and confidence intervals reported in Tables VI-3 and
VI-4 should be interpreted with caution.
Table VI-3.--Baseline EC Concentrations
8-hour Full Shift Equivalent EC Concentration ([mu]g/m\3\ )
Metal Stone Other N/ Trona Total excluding
No. of Samples................................ 284 689 196 25 1,194 1,169
Maximum....................................... 1,558 2,291 738 313 2,291 2,291
Median........................................ 208 115 114 63 134 137
Mean.......................................... 273 181 150 81 196 198
Std. Error................................ 14 8 9 12 6 6
95% UCL................................... 302 197 167 106 208 210
95% LCL................................... 245 166 132 56 184 186
Table VI-4.--Baseline DPM Concentrations
[DPM is estimated by (1.3 x EC) / 0.8]
Estimated 8-hour Full Shift Equivalent DPM Concentration ([mu]g/
Metal Stone Other N/M Trona Total excluding
No. of Samples................................ 284 689 196 25 1,194 1,169
Maximum....................................... 2,532 3,724 1,200 509 3,724 3,724
Median........................................ 339 186 185 102 218 223
Mean.......................................... 444 295 243 132 318 322
Std. Error................................ 23 13 15 20 10 10
95% UCL................................... 490 320 272 173 338 342
95% LCL................................... 399 270 214 91 299 303
Baseline EC sample results varied widely between mines within
commodities and also within most mines. Table VI-5 summarizes baseline
EC results for the 26 occupations found to have at least one sample
where the EC level exceeded the 308 [mu]g/m3 8-hour full
shift equivalent interim EC limit. As indicated by the table, EC levels
varied widely within each occupation.
Table VI-5.--Baseline EC Concentrations for Occupations With at Least One Value Exceeding Interim EC Limit
8-hour full shift equivalent EC
Number of Concentration ([mu]g/m\3\ )
Occupation valid --------------------------------------
samples Minimum Median Maximum
Diamond Drill Operator...................................... 1 1,561 1,561 1,561
Ground Control/Timberman.................................... 2 283 419 555
Washer Operator............................................. 4 272 337 621
Engineer.................................................... 1 337 337 337
Roof Bolter, Mounted........................................ 12 76 258 818
Mucking Mach. Operator...................................... 23 12 257 671
Miner, Stope................................................ 14 77 218 479
Cleanup Man................................................. 2 51 217 384
Scoop-Tram Operator......................................... 7 10 210 449
Drill Operator, Rotary Air.................................. 21 0 185 1,041
Miner, Drift................................................ 17 12 175 1,122
Blaster, Powder Gang........................................ 134 5 175 1,031
Belt Crew................................................... 8 20 173 386
Roof Bolter, Rock........................................... 21 48 172 1,007
Truck Driver................................................ 252 0 162 1,216
Shuttle Car Operator (diesel)............................... 3 73 154 323
Complete Load-Haul-Dump..................................... 32 14 145 634
Drill Operator, Jumbo Perc.................................. 38 4 137 845
Drill Operator, Rotary...................................... 75 2 132 853
Motorman.................................................... 8 46 129 322
Front-end Loader Operator................................... 214 0 121 2,291
Scaling (mechanical)........................................ 80 0 107 958
Supervisor, Co. Official.................................... 13 1 100 658
Utility Man................................................. 29 22 73 762
Scaling (hand).............................................. 26 14 67 1,548
Mechanic.................................................... 34 0 64 323
Figure VI-1 depicts, by mine category, the percentage of baseline
samples that exceeded the interim EC limit of 308 [mu]g/m\3\.
Underground metal mines exhibited the highest proportion of samples
exceeding this limit, followed by stone and then other nonmetal mines.
In the three trona mines sampled, 24 of the 25 samples were lower than
the proposed limit. Across all commodities, 19.3% of the 1,194 valid
baseline samples exceeded the interim EC limit.
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Figure VI-2 shows how samples exceeding the interim EC limit were
distributed over individual mines. One to 20 baseline samples were
taken at each mine. In 115 of the 183 mines sampled (63%), none of the
baseline EC measurements exceeded 308 [mu]g/m\3\. The remaining 68
mines (37%) had at least one sample for which EC exceeded 308 [mu]g/
m\3\. All samples taken at 4 of the mines exceeded the interim limit.
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(3) Relationship Between EC and TC
The 2001 final rule stipulated that TC (i.e., EC + OC) measurements
would be used to monitor and limit DPM concentration levels. Although
it was recognized that TC measurements were subject to various
interferences from non-DPM sources, MSHA believed that, in underground
metal and nonmetal mines, it could effectively eliminate such
interferences by a combination of selective sampling procedures and
careful analytical techniques. During the 31-Mine Study, however, MSHA
found no reasonable sampling method that would adequately protect TC
measurements from interference by such sources of organic carbon as oil
mist and ammonium nitrate fuel oil (ANFO). Furthermore, MSHA found that
it was cumbersome and impractical to restrict its TC sampling so as to
avoid potential interference from environmental tobacco smoke (ETS).
Indeed, as indicated earlier, nearly one fourth of the TC samples
collected during the 31-Mine Study (106 out of 464) had to be voided on
account of potential interferences from extraneous sources of OC.
Therefore, in concert with the Second Partial Settlement Agreement, the
2003 NPRM proposed to ``[r]evise the existing diesel particulate matter
(DPM) interim concentration limit measured by total carbon (TC) to a
comparable permissible exposure limit (PEL) measured by elemental
carbon (EC) which renders a more accurate DPM exposure measurement.''
(68 FR 48668) Using EC as the surrogate permits direct sampling of
miners (such as those who smoke, operate jackleg drills, or load ANFO)
for whom accurate DPM monitoring would be difficult or impossible using
Also in accordance with the Second Partial Settlement Agreement,
the NPRM proposed to convert the existing interim exposure limit,
expressed in terms of TC measurements, to a ``comparable'' EC limit by
applying a specific conversion factor obtained from data gathered
during the 31-Mine Study, as explained below. MSHA is adopting this
proposal with the intention of providing at least the same degree of
protection to miners as the existing interim limit. However, since it
is unlikely that EC and OC have identical health effects, it is
important to consider the extent to which the ratio of EC to OC (and
hence of EC to TC) may vary in different underground mining
Unlike the 31-Mine Study, no special precautions were taken during
MSHA's baseline sampling to avoid ETS or other substances that could
potentially interfere with using TC as a surrogate measure of DPM.
Therefore, the baseline data should not be used to evaluate the OC
content of DPM or the ratio of EC to TC within DPM. In the 31-Mine
Study, on the other hand, great care was taken to void all samples that
may have been exposed to ETS or other extraneous sources of OC.
Consequently, the analysis of the EC:TC ratio presented here relies
entirely on data from the 31-Mine Study. It is important to note that
nearly all of the samples in this study were taken in the absence of
exhaust filters to control DPM emissions. Since exhaust filters may have different effects
on EC and OC emissions, the results described here apply only to mine
areas where exhaust filters are not employed.
Figure VI-3 plots the EC:TC ratios observed in the 31-Mine Study
against the corresponding TC concentrations. The various symbols shown
in the plot identify samples taken at the same mine. The EC:TC ratio
ranged from 23% to 100%, with a mean of 75.7% and a median of 78.2%.
Note that the reciprocal of 0.78, which is 1.3, equals the median of
the TC:EC ratio observed in these samples.\4\ The 1.3 TC:EC ratio was
the value accepted, under terms of the settlement agreement, for the
purpose of temporarily converting EC measurements to TC measurements.
\4\ The median of reciprocal values is always equal to the
reciprocal of the median. This relationship does not hold for the
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The 2001 rule set a TC interim concentration limit of 400 [mu]g/
m3. Under the new rule, this TC interim limit is replaced
with an EC interim limit of 400/1.3 = 308 [mu]g/m3. Table
VI-6 indicates the impact of this change, based on the EC and TC data
obtained from the 31-Mine Study. Both the original 400 [mu]g/
m3 TC limit and the new 308 [mu]g/m3 EC limit
were exceeded by about 31% to 32% of the samples. The difference (one
sample out of 358) is not statistically significant in the aggregate.
Seven samples, however, exceeded the TC limit but not the EC limit, and
six samples exceeded the EC limit but not the TC limit.
Table VI-6.--Compliance With Original 400 [mu]g/m3 TC Limit and/or New 308 [mu]g/m3 EC Limit. Numbers in
Parentheses Are Percentages
TC > 400 [mu]g/m3
EC > 308 [mu]g/m3 -------------------------------------- Total
No..................................................... 239 (66.8) 7 (2.0) 246 (68.7)
Yes.................................................... 6 (1.7) 106 (29.6) 112 (31.3)
Total.............................................. 245 (68.4) 113 (31.6) 358 (100.0)
Several commenters noted that the ratio of EC to TC in DPM can vary
widely. One commenter pointed out that EC appeared to make up nearly
all of the TC at the mine with which he was affiliated. This commenter
stated that replacing a 400 [mu]g/m3 TC limit with a 308
[mu]g/m3 EC limit would impose a much more stringent
standard at that mine. Another commenter noted that a 308 [mu]g/
m3 EC limit would be less protective of miners than the 400
[mu]g/m3 TC limit in cases where the ratio of EC comprised
less than 78% of the TC. MARG submitted comments by a consultant, Dr.
Jonathan Borak, who emphasized that the highly variable nature of the
EC to OC ratio introduces ``large and important uncertainties in the
exposure assessments needed to sustain QRA [i.e., quantitative risk
As indicated by Figure VI-3, the percentage of EC tended to
increase with increasing TC concentration--except for cases showing a
TC concentration of less than about 60 [mu]g/m3. In many of
the samples for which TC < 60 [mu]g/m3, the recorded ratio
of EC to TC was at or near 100%. Since TC concentrations less than 60
[mu]g/m3 appear to deviate from the general pattern and are
far below the interim limit, our response to commenters concerns about
variability in the ratio of EC to TC will focus on those samples for
which TC exceeds 60 [mu]g/m3.
There were 319 samples with TC > 60 [mu]g/m3. For these
samples, the mean and median EC:TC ratio were 76.3% and 78.4%,
respectively. In accordance with standard statistical practice, an
arcsine transformation was applied to these 319 EC:TC ratios in order
to normalize them for further statistical analysis (Snedecor and
Cochran, Statistical Methods, 7th Ed., pp 290-291). The transformed
EC:TC ratios are plotted against corresponding TC concentrations in
Figure VI-4. Various symbols are used to identify the mineral commodity
corresponding to each sample.
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It is clear from Figures VI-3 and VI-4 that individual samples in
the 31-Mine Study exhibited considerable variation in their EC:TC
ratios. What is not so clear from these plots, however, is whether
different mines and/or working environments tended to experience
different EC:TC ratios. To answer this question, an analysis of
variance (ANOVA) was performed to determine whether there were
statistically significant differences in the EC:TC ratios exhibited at
different mines and on different days at the same mine. Table VI-7
contains the results of this ANOVA. At a confidence level exceeding
99.9%, the data show statistically significant differences in the mean
EC:TC ratios between mines and between different sampling days within
Table VI-7.--Analysis of Variance for Arcsin of EC:TC Ratios, Restricted to Samples With TC > 60 [mu]g/m3
Source Sum of of Mean F-ratio P
squares freedom square
MINE..................................................... 3.360 29 0.116 6.960 0.000
DAY within MINE.......................................... 1.643 30 0.055 3.290 0.000
Error.................................................... 4.295 258 0.017 ......... .........
Figure VI-5 illustrates the magnitude and extent of differences in
the mean EC:TC ratio between mines. Note that values on the arcsin
scale of 0.7, 0.9, and 1.1 correspond to EC:TC ratios of 64%, 78%, and
Since TC = EC + OC, variability in the EC:TC ratio corresponds to
variability in the ratio of either EC or TC to OC. Dr. Borak stated
that if DPM is carcinogenic, then the carcinogenic agents (for humans)
are probably in the organic fraction (i.e., OC). Consequently,
according to Dr. Borak, neither EC nor TC provides an appropriate
surrogate for assessing or limiting health risks.
MSHA believes that Dr. Borak's assumption that any carcinogenic
effect of DPM is due entirely to the organic fraction is speculative.
This assumption contradicts findings reported by Ichinose et al.
(1997b) and does not take into account the contribution that
inflammation and active oxygen radicals induced by the inorganic carbon
core of DPM may have in promoting lung cancers. Indeed, identifying the
toxic components of DPM, and particulate matter in general, is an
important research focus of a variety of government agencies and
scientific organizations (see, for example: Health Effects Institute,
2003; Environmental Protection Agency, 2004b). The 2001 risk assessment
discusses possible mechanisms of carcinogenesis for which both EC and
OC would be relevant factors (66 FR at 5811-5822). Multiple routes of
carcinogenesis may operate in human lungs--some requiring only the
various organic mutagens in DPM and others involving induction of free
radicals by the EC core, either alone or in combination with the
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BILLING CODE 4510-43-C
In focusing on the carcinogenic agents in OC, Dr. Borak has also
ignored non-cancer health effects documented in the 2001 risk
assessment--e.g., immunological, inflammatory, and allergenic responses
in healthy human volunteers exposed to 300DPM [mu]g/
m3 (i.e., 240TC [mu]g/m3) for as
little as one hour (66 FR at 5769-70, 5816-17, 5820, 5823, 5837, 5841,
The 308 [mu]g/m3 interim EC PEL established by this rule
is intended to be commensurate with the interim TC limit of 400 [mu]g/
m3 established under the 2001 rule--i.e., to be equally
protective and equally feasible. Although, as shown by Table VI-7 and
Figure VI-5, the EC:TC ratio can exhibit considerable variability in
specific cases, MSHA has concluded that application of the 1.3 average
conversion factor, as suggested in the second partial settlement
agreement, generally achieves the goal of equal protection and
C. Health Effects
A key conclusion of the 2001 risk assessment was:
Exposure to DPM can materially impair miner health or functional
capacity. These material impairments include acute sensory
irritations and respiratory symptoms (including allergenic
responses); premature death from cardiovascular, cardiopulmonary, or
respiratory causes; and lung cancer. [66 FR at 5854-5855]
MSHA has reviewed the scientific literature pertaining to health
effects of fine particulates in general and DPM in particular published
later than what was considered in the 2001 risk assessment. As will be
shown below, the more recent scientific evidence generally supports the
conclusion above, and nothing in our review suggests that it should be
altered. In fact, the U.S. Environmental Protection Agency (EPA)
recently reached very similar conclusions after reviewing all of the
evidence to date (EPA; 2002, 2004b).
Some commenters endorsed the 2001 risk assessment, and suggested
that the latest evidence strengthens its conclusions. For example, one
group of commenters jointly stated:
The evidence presented in MSHA's 2001 risk assessment is
overwhelming * * * The evidence linking exposure to particulate air
pollution and/or diesel particulate matter with lung cancer,
cardiovascular and cardiopulmonary and other adverse health effects
continues to mount.
Similarly, another pair of commenters jointly stated that ``[t]he
scientific evidence for the [adverse] health effects of DPM is
overwhelming'' and that ``evidence for the carcinogenicity and non-
cancer health effects of DPM has grown since 1998.''
Other commenters contended that all of the evidence to date is
insufficient to support limitation of occupational DPM exposures.
Several of these commenters ignored evidence presented in the 2001 risk
assessment and/or mischaracterized its conclusions. For example, the
NMA, MARG, and the Nevada Mining Association (NVMA) all erroneously
stated that promulgation of the 2001 rule was based on only ``two
principal health concerns: (1) The transitory, reversible health
effects of exposure to DPM; and, (2) the long-term impacts that may
result in an excess risk of lung cancer for exposed workers.''
Actually, as shown in the conclusion cited above, the 2001 risk
assessment identified three different kinds of material health
impairment associated with DPM exposure: (1) Acute sensory irritations
and respiratory symptoms (including allergenic responses); (2)
premature death from cardiovascular, cardiopulmonary, or respiratory
causes; and (3) lung cancer. Although the cardiovascular,
cardiopulmonary, and respiratory effects leading to an increased risk
of premature death were associated with acute DPM exposures, commenters
presented no evidence that any such effects were ``transitory'' or
``reversible.'' Nor did commenters present evidence that immunological
responses associated with either short-term or long-term DPM exposure
were ``transitory'' or ``reversible.''
In addition, some commenters erroneously stated that ``no
[quantitative] dose/response relationship related to the PELs could be
demonstrated by MSHA.'' These commenters apparently ignored the
discussion of exposure-response relationships in the 2001 risk
assessment (66 FR at 5847-54) and failed, specifically, to note the
quantitative exposure-response relationships shown for lung cancer in
the two tables provided (66 FR at 5852-53). Relevant exposure-response
relationships were also demonstrated in articles by Pope et al. cited
in the 2003 NPRM, which will be discussed further below.
Some commenters objected that the exposure-response relationships
presented in the 2001 risk assessment did not justify adoption of the
specific DPM exposure limits promulgated. These commenters mistakenly
assumed the limits set forth in the 2001 final rule were derived from
an exposure-response relationship. As explained in 66 FR at 5710-14,
the choice of exposure limits, while justified by quantifiable adverse
health effects, was actually driven by feasibility concerns. The
exposure-response relationships provided clear evidence of adverse
human health effects (both cancer and non-cancer) at levels far below
those determined to be feasible for mining.
In the 2003 NPRM, MSHA identified scientific literature pertaining
to health effects of fine particulates in general and DPM in particular
published subsequent to the 2001 final rule. The 2003 NPRM stated
MSHA's intentions to continue its reliance on the 2001 risk assessment
and cited the newer literature in a neutral manner, soliciting public
comment on its implications for the 2001 risk assessment.
Two commenters complained that MSHA had not described the recent
scientific literature in sufficient detail to determine whether it
supports the 2001 risk assessment. Most of the commenters who evaluated
the recent literature found that it supported and/or strengthened the
conclusions of the 2001 risk assessment. Some other commenters,
however, disagreed. Accordingly MSHA will present the supplemental
literature in more detail than in the 2003 NPRM and explain why MSHA
believes that it continues to support the 2001 risk assessment. This
discussion will include our review of an analysis by Dr. Gerald Chase
of some preliminary data from an ongoing NIOSH/NCI study.
The scientific literature cited in the 2003 NPRM was meant only to
update and supplement the evidence of health effects cited in the 2001
risk assessment. Although MSHA believes the 2001 risk assessment
presented ample evidence to justify its conclusions, MSHA is adding
this supplemental literature because it represents more recent
scientific investigations related to DPM health effects. The following
discussion of literature cited in the 2003 NPRM is organized into four
categories, roughly corresponding to the three types of material health
impairments identified in the 2001 risk assessment, followed by a
category covering toxicology studies: (1) Respiratory and immunological
effects, including asthma, (2) cardiovascular and cardiopulmonary
effects, (3) cancer, and (4) mechanisms of toxicity. Although the
discussion of cancer will focus on lung cancer, it will also take note
of two recent meta-analyses of epidemiological studies investigating
DPM in connection with bladder and pancreatic cancers.
(1) Respiratory and Immunological Effects, Including Allergenic
In the 2001 risk assessment, acute sensory irritations with
respiratory symptoms, including immunological or allergenic effects
such as asthmatic responses were grouped together, and all such effects
as material health impairments likely to be caused or exacerbated by
excessive DPM exposures were identified. This finding was based on
human experimental and epidemiological studies and was supported by
experimental toxicology. (For an explanation of why MSHA considers such
effects to be material impairments, regardless of whether they are
``reversible,'' See, 66 FR at 5766.)
Table VI-8 summarizes six additional studies dealing with possible
respiratory and immunological effects of DPM and/or fine particulates
in general. Three of these studies (Frew et al., 2001; Holgate et al.,
2002; Salvi et al., 2000) involved experiments in which human subjects
inhaled specified doses of DPM. These three studies all support the
view that occupational DPM exposures are likely to promote or
exacerbate adverse respiratory symptoms and immunological responses. A
fourth study (Svartengren et al., 2000) exposed human subjects to high
and low doses of an unspecified mix of diesel and gasoline engine
exhausts. Although 30-minute PM2.5 exposures greater than
100 [mu]g/m3 were found to increase asthmatic response, the authors of
this study attributed the effects they observed primarily to
NO2 exposure. The fifth study (Oliver et al., 2001)
attempted to relate pulmonary function test results and asthmatic conditions to
estimated lifetime diesel exposure in a cohort of 359 ``heavy and
highway'' (HH) construction workers. After adjustment for smoking and
other potential confounders, the results indicated an elevated risk of
asthma for exposed workers in enclosed spaces (tunnel workers),
relative to other HH workers. The lack of additional statistically
significant results may be attributable to the small cohort size. The
sixth study (Fusco et al., 2001) examined the relationship between
various markers of engine exhaust pollution levels and daily hospital
admissions for acute respiratory infections, COPD, asthma, and total
respiratory conditions in Rome, Italy. No direct measurements of fine
particulate concentrations were available. However, having found a
significant correlation between respiratory-related admissions and CO
and NO2 levels, the authors noted that since CO and
NO2 are good indicators of combustion products in vehicular
exhaust, the detected effects may be due to unmeasured fine and
Table VI-8.--Studies of Human Respiratory and Immunological Effects,
Authors, year Description Key results
Frew et al., 2001........... 25 healthy subjects Both the asthmatic
and 15 subjects and healthy
with mild asthma subjects developed
were exposed to increased airway
diesel exhaust (108 resistance after
[mu]g/m3) or exposure to diesel
filtered air for 2 emissions, but
hr, with airway inflammatory
intermittent responses were
exercise. Lung different for the 2
function was groups. The healthy
assessed using a subjects showed
computerized whole statistically
body significant BW
plethysmograph. neutrophilia and
Airway responses BAL lymphocytosis 6
were sampled by hr after exposure.
bronchial wash The neutrophilic
(BW), response of the
bronchoalveolar healthy subjects
lavage (BAL), and was less intense
mucosal biopsies 6 than that seen in a
hr after ceasing previous study
exposures. using a DPM
Fusco et al., 2001.......... Analysis of daily Respiratory
hospital admissions admissions among
for acute adults were
infections, COPD, correlated with CO
asthma, and total and NO2 levels, but
respiratory not with suspended
conditions in Rome, particles. The
Italy. authors noted that
since CO and NO2
are good indicators
effects may be due
to unmeasured fine
Holgate et al. 2002......... 25 healthy and 15 Healthy and
asthmatic subjects asthmatic subjects
were exposed for 2 exhibited evidence
hours to 100 [mu]g/ of
m3 of DPM and to bronchioconstrictio
filtered air on n immediately after
separate days. exposure
Another 30 healthy Biochemical tests of
subjects were inflammation
exposed for 2 hours yielded mixed
to DPM results but showed
concentrations small inflammatory
ranging from 25 to changes in healthy
311 [mu]g/m3 and subjects after DPM
compared to 12 inhalation.
subjects exposed to
were assessed using
lung function tests
tests of bronchial
Oliver et al., 2001......... Pulmonary function After adjusting for
tests and smoking and some
questionnaire data other potential
were obtained for confounders, HH
350 ``heavy and workers showed
highway'' (HH) elevated risk of
construction asthma. One
workers. Intensity subgroup (tunnel
of DPM exposure was workers) also
estimated according showed elevated
to job risk of both
classification. undiagnosed asthma
Duration of and chronic
exposure was bronchitis,
estimated based on compared to other
length of union HH workers.
membership. Respiratory symptoms
as measured length
this as suggesting
that HH workers
tend to leave their
trade when they
Salvi et al., 2000.......... 15 healthy Diesel exhaust
nonsmoking exposure enhanced
volunteers were gene transcription
exposed to 300 of IL-8 in the
[mu]g/m3 DPM and bronchial tissue
clean air for one and airway cells
hour at least three and increased IL-8
weeks apart. and GRO-[alpha]
Biochemical protein expression
analyses were in the bronchial
performed on epithelium. This
bronchial tissue was accompanied by
and bronchial wash a trend toward
cells obtained six increased IL-5 mRNA
hours after each gene transcripts in
exposure. the bronchial
showed effects on
in the lower
airways of healthy
are associated with
of asthma and
Svartengren et al;. 2000.... Twenty nonsmoking Subjects with PM2.5
subjects with mild exposure >= 100
allergic asthma [mu]g/m3 exhibited
were exposed for 30 slightly increased
minutes to high and asthmatic
low levels of responses.
engine exhaust air Association with
pollution on two adverse outcome
separate occasions variables were
at least four weeks weaker for
apart. Respiratory particulates than
symptoms and for NO2.
during and after
periods. Four hours
exposure, the test
challenged with a
low dose of inhaled
were monitored for
several hours after
The 2003 NPRM also cited five new review articles that summarize
the scientific literature pertaining to the respiratory and
immunological effects of DPM and fine particulate matter in general.
These review articles, published after the 2001 risk assessment, are
identified and briefly described in Table VI-9. The three articles most
specifically dealing with DPM effects are Pandya et al. (2002), Peden at al. (2002),
and Sydbom et al. (2001). In general, these reviews indicate that while DPM is likely
to contribute to asthmatic and/or other immunological responses, the role of DPM in
producing these health effects is complex. As noted by Pandya et al.
(op cit.), DPM may have a far greater impact as an adjuvant with
allergens than alone. Nevertheless, all three of these review articles
support the view that there is significant evidence of adverse
respiratory and immunological effects to warrant regulating DPM
exposures. The remaining review articles (Gavett and Koren, 2001;
Patton and Lopez, 2002) offer little new support for the 2001 risk
assessment, but MSHA found no studies that either refute or challenge
the 2001 risk assessment.
Table VI-9.--Review Articles on Respiratory and Immunological Effects,
Authors, year Description Key results
Gavett and Koren, 2001...... Summarizes results Studies indicate
of EPA studies done that PM enhances
to determine allergic
whether PM can sensitization in
enhance allergic animal models of
sensitization or allergy exacerbate
exacerbate existing inflammation and
asthma or asthma- airway hyper-
like responses in responsiveness in
humans and animal asthmatics and
models. animal models of
Pandya et al. 2002.......... Reviews human and Evidence indicates
animal research that DPM is
relevant to associated with the
question of whether inflammatory and
DPM is associated immune responses
with asthma. involved in asthma,
but DPM appears to
have far greater
impact as an
DPM appears to
chemokines. DPM may
also promote the
of free radicals in
Patton and Lopez, 2002...... Review of evidence Evidence suggests
and mechanisms for that air pollutants
the role of air (including DPM)
pollutants in ``affect allergic
allergic airways response by
increase total IgE
allergens and the
IgE response to a
Pollutants also may
act by increasing
inflammation and by
addition, it is
well known that
pollutants can be
direct irritants of
in patients with
Peden, 2002................. Review of ``studies DPM ``may play a
that exemplify the significant role
impact of ozone, not only in asthma
particulates, and exacerbation but
toxic components of also in TH2
particulates on inflammation via
asthma.''. the actions of
hydrocarbons on B
``* * * PM in which
the active agents
active metal ions
residues * * * may
effects on asthma,
demonstrated by the
diesel exhaust in
Sydbom et al. 2001.......... Review of scientific The epidemiological
literature on support for
health effects of particle effects on
disease exhaust, asthma and
especially the DPM respiratory health
components. is very evident;
systemic effects of
DPM have been
documented in a
wide variety of
Acute effects of DPM
irritation of the
nose and eyes, lung
Exposure studies in
healthy humans have
documented a number
changes in the
before changes in
can be detected.
Such effects may be
suspected of being
the most aggressive
component of diesel
In its 2002 ``Health Assessment Document for Diesel Engine
Exhaust,'' the Environmental Protection Agency (EPA) reached the
following conclusion with respect to immunological effects of diesel
Recent human and animal studies show that acute DE [diesel exhaust]
exposure episodes can exacerbate immunological reactions to other
allergens or initiate a DE-specific allergenic reaction. The effects
seem to be associated with both the organic and carbon core fraction
of DPM. In human subjects, intranasal administration of DPM has
resulted in measurable increases of IgE antibody production and
increased nasal mRNA for some proinflammatory cytokines. These types
of responses also are markers typical of asthma, though for DE,
evidence has not been produced in humans that DE exposure results in
asthma. The ability of DPM to act as an adjuvant to other allergens
also has been demonstrated in human subjects. (EPA, 2002)
(2) Cardiovascular and Cardiopulmonary Effects
In the 2001 risk assessment, the evidence presented for DPM's
adverse cardiovascular and cardiopulmonary effects relied on data from
air pollution studies in the ambient air. This evidence identifies
premature death from cardiovascular, cardiopulmonary, or respiratory
causes as an endpoint significantly associated with exposures to fine
particulates. The 2001 risk assessment found that ``[t]he mortality
effects of acute exposures appear to be primarily attributable to
combustion-related particles in PM2.5 [i.e., fine
Particulate Matter] (such as DPM) * * *.''
There are difficulties involved in utilizing the evidence from such
studies in assessing risks to miners from occupational DPM exposures.
As noted in the 2001 risk assessment,
First, although dpm is a fine particulate, ambient air also contains
fine particulates other than dpm. Therefore, health effects
associated with exposures to fine particulate matter in air
pollution studies are not associated specifically with exposures to
dpm or any other one kind of fine particulate matter. Second,
observations of adverse health effects in segments of the general
population do not necessarily apply to the population of miners.
Since, due to age and selection factors, the health of miners
differs from that of the public as a whole, it is possible that fine
particles might not affect miners, as a group, to the same degree as
the general population.
Since dpm is a type of respirable particle, information about health
effects associated with exposures to respirable particles, and
especially to fine particulate matter, is certainly relevant, even
if difficult to apply directly to dpm exposures. [66 FR 5767]
Pope (2000) reviewed the epidemiological evidence for adverse
health effects of PM2.5 and characterized populations at
increased risk due to PM2.5 exposure. He found that ``[t]he
overall epidemiologic evidence indicates a probable link between fine
particulate air pollution and adverse effects on cardiopulmonary
health.'' The observed endpoints include ``death from cardiac and
pulmonary disease, emergency and physician office visits for asthma and
other cardiorespiratory disorders, hospital admissions for
cardiopulmonary disease, increased reported respiratory symptoms, and
decreased measured lung function.'' Moreover, according to Pope, recent
research suggests that ``those who are susceptible to increased risk of
mortality from acutely elevated PM may include more than just the most
old and frail who are already very near death.'' Pope went on to state
that, with respect to chronic exposure, ``[t]here is no evidence that
increased mortality risk is confined to any well-defined susceptible
Table VI-10 identifies five studies on cardiovascular and
cardiopulmonary effects published since the 2001 risk assessment
(Lippmann et al., 2000; Magari et al., 2001; Pope et al., 2002; Samet
et al., 2000a, 2000b; Wichmann et al., 2000). Three of these studies
(Pope et al., 2002; Samet et al., 2000a, 2000b; Wichmann et al., 2000)
significantly strengthen MSHA's existing evidence implicating
particulate exposures with premature mortality from cardiovascular and
cardiopulmonary causes.\5\ The Samet and Pope (2002) articles both
establish statistically significant exposure-response relationships.
\5\ As discussed below, Pope et al. (2002) also provides strong
evidence linking chronic PM2.5 exposure with an elevated
risk of lung cancer.
Table VI-10.--Studies Relating to Cardiovascular and Cardiopulmonary
Authors, years Description Key results
Lippmann et al. 2000........ Day-to-day After adjustment for
fluctuations in the presence of
particulate air other pollutants,
pollution in the significant
Detroit area were associations were
compared with found between
corresponding particulate levels
fluctuations in and an increased
daily deaths and risk of death due
hospital admissions to circulatory
for 1985-1990 and causes. However,
1992-1994. relative risks were
about the same for
PM2.5 and larger
Magari et al., 2001......... Longitudinal study After adjusting for
of a male potential
occupational cohort confounding factors
examined the such as age, time
relationship of day, and urinary
between PM2.5 nicotine level,
exposure and PM2.5 exposure was
cardiac autonomic significantly
function. associated with
Pope et al., 2002........... Prospective cohort After adjustment for
mortality study, other risk factors
based on data and potential
collected for confounders, using
Cancer Prevention a variety of
II Study, which statistical
began in 1982. methods, fine
Questionnaires were particulate (PM2.5)
used to obtain exposures were
individual risk significantly
factor data (age, associated with
sex, race, weight, cardiopulmonary
height, smoking mortality (and also
history, education, with lung cancer).
marital status, Each 10-[mu]g/m\3\
diet, alcohol increase in mean
consumption, and level of ambient
occupational fine particulate
exposures). For air pollution was
about 500,000 associated with an
adults, these were increase of
combined with air approximately 6% in
pollution data for the risk of
metropolitan areas cardiopulmonary
throughout the U.S. mortality.
and with vital
status and cause of
death data through
Samet et al., 2000a, 2000b.. Time series analyses Results of both the
were conducted on 20-city and 90-city
data from the 20 mortality analyses
and 90 largest U.S. are consistent with
cities to an average increase
investigate in cardiovascular
relationships and cardiopulmonary
between PM10 and deaths of more than
other pollutants 0.5% for every 10
and daily mortality. [mu]g/m\3\ increase
in PM10 measured
the day before
effects are, in
lower using a more
Dominici et al.,
Wichmann et al., 2000....... Time series analyses Higher levels of
were conducted on both fine and
data from Erfurt, ultrafine particle
Germany to concentrations were
relationships associated with
between the number increased mortality
and mass rate.
ultrafine and fine
particles and daily
Pope et al. (2002) warrants special attention because this study
addresses chronic effects of long-term PM2.5 exposures.
(Other studies on PM2.5, described in the 2001 risk
assessment, have almost all dealt with acute exposure effects.) The
authors concluded that ``* * * the findings of this study provide the
strongest evidence to date that long-term exposure to fine particulate
air pollution * * * is an important risk factor for cardiopulmonary
mortality.'' In the 2001 risk assessment, the conclusion related to
cardiopulmonary effects was motivated mostly by evidence on short-term
exposures from daily time series analyses. Therefore, in finding a
significant increase in cardiopulmonary mortality attributable to
chronic fine particulate exposures, this study provides important
supplement evidence supporting this conclusion. The portion of the
study related to lung cancer effects is summarized in the next section.
The EPA's 2004 Air Quality Criteria Document for particulate matter
(EPA, 2004b) describes a number of additional studies related to the
cardiopulmonary and cardiovascular effects of PM2.5,
including work published later than that cited in the 2003 NPRM. One of
the summary conclusions presented in that document is:
Overall, there is strong epidemiological evidence linking (a) short-
term (hours, days) exposures to PM2.5 with cardiovascular
and respiratory mortality and morbidity, and (b) long-term (years,
decades) PM2.5 exposure with cardiovascular and lung
cancer mortality and respiratory morbidity. The associations between
PM2.5 and these various health endpoints are positive and
often statistically significant. [EPA, 2004b, Sec. 9 p. 46]
1. Cancer Effects
The 2001 risk assessment concluded that DPM exposure, at
occupational levels encountered in mining, was likely to increase the
risk of lung cancer. The assessment also found that there was
insufficient evidence to establish a causal relationship between DPM
and other forms of cancer. Both of these conclusions are supported by
the most recent scientific literature. The first part of this update
contains a description of three new human research studies and a
literature review relating DPM and/or other fine particulate exposures
to lung cancer. Since it relates specifically to lung cancer, this
subsection also discusses Dr. Chase's analysis. New research on the
relationship between DPM exposures and other forms of cancer are
described immediately after the lung cancer discussion.
Table VI-11 presents three human studies pertaining to the
association between lung cancer and exposures to DPM or fine
particulates in general completed after the 2001 risk assessment was
Table VI-11.--Studies on Lung Cancer Effects, 2000-2002.
Authors, year Description Key results
Boffetta et al., 2001....... Cohort consisting of Statistically
entire Swedish significant
working population elevations in
other than farmers. relative risk (RR)
Exposure assessment of lung cancer
based on job title among men for job
and industry, categories with
classified medium, and high
according to exposure to diesel
probability and exhaust, compared
intensity of diesel to workers in jobs
exhaust exposure. classified as
Gustavsson et al., 2000..... Case-control study Adjusted RR for the
involving all 1,042 highest quartile of
male cases of lung estimated lifetime
cancer and 2,364 exposure was 1.63,
randomly selected compared to the
controls (matched group with no
by age and exposure.
inclusion year) in
Sweden from 1985
through 1990. Semi-
exposure to diesel
Risk (RR) estimates
adjusted for age,
exposure to NO2.
Pope et al., 2002........... Prospective cohort After adjusting for
mortality study other risk factors
using data and potential
collected for the cofounders, chronic
American Cancer PM2.5 exposures
Society Cancer found to be
Prevention II Study significantly
(began 1982). associated with
Questionnaires used elevated lung
to obtain cancer mortality.
individual risk Each 10-[mu]g/m\3\
factor data increase in mean
including age, sex, level of ambient
race, weight, fine particulate
height, smoking air pollution
history, education, (PM2.5) associated
marital status, with statistically
diet, alcohol significant
consumption, and increase of
occupational approximately 8% in
exposures. This risk of lung cancer
risk factor data mortality.
combined with air
pollution data for
throughout U.S. and
vital status and
cause of death data
through 1998 for
Boffetta et al. (2001) investigated a Swedish cohort comprised of
the whole Swedish working population not employed as farmers. Job title
and industry were classified according to probability and intensity of
diesel exhaust exposure in 1960 and 1970 and also according to the
authors' confidence in the assessment. Cohort members were followed up
for mortality for the 19-year period from 1971 through 1989. Cause of
death and specific cancer type, when applicable, were obtained from
Compared to workers in jobs classified as having no occupational
exposure to diesel emissions, relative risks (RR) of lung cancer among
men were 0.95, 1.1, and 1.3 for job categories with low, medium, and
high exposure intensity, respectively. The elevated risks for the
medium and high exposure groups were statistically significant, and no
similar pattern was observed for other cancer types. The authors
concluded that these results ``provide evidence of a positive exposure-
response relationship between exposure to diesel emissions and lung
cancer among men.''
Although this study adds to the cumulative weight of evidence
establishing a causal link between DPM exposure and lung cancer, it
does not provide very strong evidence when viewed in isolation. One
weakness of the study is that the exposure assessment was based on
self-reported occupation and industry, with no information on duration
of employment in various jobs. (This sort of uncertainty in the
exposure assessment, however, would not normally be expected to induce
a false exposure-response relationship.) Another weakness is that there was
no information on potential confounders, such as tobacco smoking and lifestyle factors
that may be associated with certain jobs. While recognizing this
limitation, the authors considered it unlikely that confounders could
account for the increasing trend in relative risk observed according to
intensity of diesel exposure.
Gustavsson et al. (2000) performed a case-control study involving
all 1,042 male cases of lung cancer and 2364 randomly selected controls
(matched by age and inclusion year) in Stockholm County, Sweden from
1985 through 1990. Occupational exposure, smoking habits, and other
potential risk factors were assessed based on written questionnaires
mailed to the subject or next of kin. Relative Risk (RR) estimates were
adjusted for age, selection year, tobacco smoking, residential radon,
occupational exposures to asbestos and combustion products, and
environmental exposure to NO2. Compared to the group with no
exposure, adjusted RR for the highest quartile of estimated lifetime
exposure was 1.63 (95% CI = 1.14 to 2.33). The authors concluded that
``[t]he present findings add further evidence for an association
between diesel exhaust and lung cancer * * * ''
Strengths of this study include a semi-quantitative exposure
assessment and adjustment of the relative risk for several important
potential confounders. The statistically significant result
corroborates the finding of a link between DPM exposure and lung cancer
in MSHA's 2001 risk assessment.
Pope et al. (2002) used the cohort established by the American
Cancer Society Cancer Prevention II Study to examine the relationship
between lung cancer and PM2.5 air pollution. This
prospective cohort mortality study, which began in 1982, used
questionnaires to obtain individual risk factor data (age, sex, race,
weight, height, smoking history, education, marital status, diet,
alcohol consumption, and occupational exposures). For about 500,000
adults, these risk factors were combined with air pollution data for
metropolitan areas throughout the U.S. and with vital status and cause
of death data through 1998.
After adjusting for other risk factors and potential confounders,
using a variety of statistical methods, chronic PM2.5
exposures were found to be significantly associated with elevated lung
cancer mortality.\6\ Each 10 [mu]g/m\3\ increase in the mean level of
ambient fine particulate air pollution was associated with a
statistically significant increase of approximately 8% in the risk of
lung cancer mortality. Within the range of exposures found in the
study, the exposure-response relationship between PM2.5 and
lung cancer was monotonically increasing. The authors concluded that
``[e]levated fine particulate exposures were associated with
significant increases in lung cancer mortality * * * even after
controlling for cigarette smoking, diet, occupational exposure, other
individual risk factors, and after controlling for regional and other
\6\ As discussed earlier, Pope et al. (2002) also provides
strong evidence that chronic PM2.5 exposure increases the
risk of premature cardiopulmonary mortality.
Szadkowska-Stanczyk and Ruszkowska (2000) performed a literature
review of studies relating to the carcinogenic effects of diesel
emissions. The authors concluded that long-term exposure (> 20 years)
was associated with a 30% to 40% increase in lung cancer risk in
workers in the transport industry. This article was written in Polish,
and MSHA was unable to obtain a translation of it for this update.
However, based on the English abstract, it appears to add no new
information to the 2001 risk assessment.
Several commenters expressed opinions on the unpublished document
by Dr. Gerald Chase (2004) entitled Characterizations of Lung Cancer in
Cohort Studies and a NIOSH Study on Health Effects of Diesel Exhaust in
Miners, which was placed into the public record at MARG's request. This
document presents an analysis of some preliminary data provided by
NIOSH and NCI at a public stakeholder meeting held on Nov. 5, 2003.
These data were taken from unpublished charts that NIOSH and NCI used
to inform the public on the status and progress of their ongoing
project, A Cohort Mortality Study with a Nested Case-Control Study of
Lung Cancer and Diesel Exhaust Among Nonmetal Miners [NIOSH/NCI 1997].
Researchers involved in that project have thus far published no
analyses or conclusions based on these data. Dr. Chase, however,
concluded that ``based on the limited data available to date, the
number and pattern of lung cancer deaths reported * * * are in
agreement with lung cancer deaths from the general population for the
age groups involved * * *'' and ``* * * are possible without
attributing any excess cancers to the study subject matter: diesel
exhaust'' [emphasis added]. He offered no opinion as to whether the
preliminary data actually demonstrate that there were no excess lung
cancers attributable to DPM exposures.
Although Dr. Chase noted that his analyses and conclusions were
limited and based on incomplete information, some commenters
interpreted his report as casting serious doubt on any increased risk
of lung cancer associated with occupational DPM exposures. For example,
one commenter said the report ``suggests lung cancer is not a problem
in this worker population.'' Another commenter interpreted Dr. Chase's
findings as providing ``startling evidence rebutting MSHA's PELs and
risk analysis.'' Other industry commenters asserted that Dr. Chase's
analysis ``eliminates the rationale upon which the final 160 microgram
standard was premised.'' Another commenter claimed that Dr. Chase's
analysis shows MSHA's justification for limiting DPM exposures is
``contradicted by the NIOSH/NCI data.''
Commenters representing organized labor, on the other hand, focused
on the preliminary and incomplete nature of the data Dr. Chase
analyzed. One such commenter pointed out that these data had not been
made directly available on MSHA's web site and that the status of the
NIOSH/NCI study was not discussed in the re-opening announcement.
Another commenter argued that the Chase analysis does not meet minimal
standards of ``real epidemiological research'' and that it ``is
worthless for the purpose of [MSHA's DPM] rulemaking.'' This commenter
also stated that ``the record already contains ample evidence of the
carcinogenicity of DPM'' and that ``the NIOSH/NCI study will not shake
those findings, even if it should prove to be inconclusive.''
The Chase analysis ignores at least three factors that can
reasonably be expected to heavily influence the findings of the NIOSH/
NCI study: (a) Differentiation between exposed and unexposed miners
within the study, (b) quantification of exposure, and (c) possible
``healthy worker effect.'' According to the 1997 NIOSH/NCI study
protocol, these three factors will be taken fully into account before
any conclusions are published. The remainder of this subsection will
explain how ignoring them, as in the Chase report, can mask adverse
health effects potentially associated with DPM exposures.
(a) Differentiation Between Exposed and Unexposed Miners
Approximately 50% of the miners in the NIOSH/NCI study cohort are
expected to be surface workers (NIOSH/NCI, 1997, Tables A.1 and B.2).
These miners are likely to have experienced far lower levels of DPM
exposure than underground miners in the cohort. The NIOSH/NCI study
protocol specifies that such members of the cohort--i.e., those who
have had little or no occupational DPM exposure `` will be used as the
``unexposed'' control group for the study. In other words, the protocol
calls for statistically comparing the health of these surface workers
to the health of the much more highly exposed underground workers.
Dr. Chase did not distinguish between surface and underground
workers in the cohort. Consequently, his analysis may dilute the lung
cancer rate for exposed miners by combining it with the rate for miners
with relatively little exposure. As noted by Dr. Chase, the preliminary
data presented indicate that 9.8% of the deaths in the overall cohort
were from lung cancer. He also suggests that the normal or
``background'' percentage is 8.0%, based on the national lung cancer
mortality rate and that the excess of 9.8% over 8.0% is not
statistically significant. Suppose, however, that the overall excess of
lung cancer deaths arose entirely from that half of the cohort
comprising exposed, underground workers. Then, for miners in the
``exposed'' group, the percentage of deaths from lung cancer would
actually be 11.6%. Since 8.0/2 + 11.6/2 = 9.8, the 8.0% rate for
surface workers would have diluted the 11.6% rate for exposed
underground workers to yield an average rate of 9.8%. In this case, the
lung cancer rate for underground miners would be about 45% greater than
the national background rate (i.e., 11.6/8.0).
Dr. Chase also claims that the 8% ``background'' rate is too low,
since it combines all ages and includes relatively low lung cancer
death rates for ages below 55 years. Although it is true that age-
specific lung cancer mortality rates increase after age 55, this should
be considered only in conjunction with the age at death for members of
the specific study cohort. Approximately two-thirds of the cohort
members were born after 1940, with a maximum age at death of 56 years.
For this age group, less than 5% of all deaths are attributed to lung
cancer. Therefore, for purposes of comparison with this particular
study cohort, an 8% background rate may be too high rather than too
low, and the excess for underground workers may be even greater than
the 45% indicated above.
(b) Quantification of Exposure
As explained in the 2001 risk assessment, quantification of
exposure was an important element in MSHA's evaluation of epidemiologic
studies on DPM and lung cancer (FR 66 at 5784-5785, 5795ff). Relatively
little weight was placed on studies that took no account of duration
and intensity of exposure. At the time of the NIOSH/NCI Joint Study
Meeting to discuss information with stakeholders on the progress of the
study, exposure data for individual miners still were being processed.
Since such exposure data were not presented at the meeting, they could
not be used in Dr. Chase's analysis.
The lack of detailed exposure data in Dr. Chase's analysis could
potentially cause major distortions in interpretation of the results.
The study cohort includes a number of workers with relatively short
exposure duration. This is demonstrated by a 1981 NIOSH study showing
that the mean tenure of underground trona miners working in 1976 was
only about 3 years for ages greater than 25 years. (Attfield et al.
1981). The two largest trona mines included in that study were also
included in the NIOSH/NCI study (identified as Numbers 6 and 8 in Table
A.1 of the 1997 NIOSH/NCI study protocol). Therefore, a substantial
portion of the NIOSH/NCI study cohort may have been occupationally
exposed to DPM for three years or less. If such short exposures produce
little or no excess in lung cancers, then this portion of the cohort
could mask a significant excess among workers with longer exposures.
Since Dr. Chase's analysis lumps miners together without regard to
exposure duration, it provides no effective way to evaluate effects
associated with long-term exposure.
(c) Internal Versus External Analysis
Another important element in MSHA's evaluation of epidemiologic
studies on DPM and lung cancer was equitable composition of the groups
being compared (FR 66 at 5783-5784, 5795ff). As explained in the
Federal Register, comparison of an exposed cohort to an external
control group can give rise to various forms of selection bias. For
example, the ``healthy worker effect,'' which is widely recognized in
the occupational health literature, tends to reduce estimates of excess
risk in a group of workers when that group is compared to a general
population. Several of the lung cancer cohort studies reviewed in the
2001 risk assessment cohorts showed no excess lung cancers among
exposed workers compared to an external population. Nevertheless, those
studies showed excess lung cancers among exposed workers compared to
otherwise similar but unexposed workers.
To avoid selection biases, the 2001 risk assessment favored
comparisons against internal control groups or studies that compensated
for the healthy worker effect by means of an appropriate adjustment.
Dr. Chase's analysis, however, focuses entirely on external comparisons
with no compensating adjustment--an approach that the 2001 risk
assessment generally discounted. Although the NIOSH/NCI study protocol
explicitly calls for internal comparisons, the detailed exposure data
necessary for such comparisons were not available to Dr. Chase since
they were not presented during the November 5, 2003 public meeting.
(d) Conclusions Regarding Dr. Chase's Analysis
Dr. Chase has argued that some preliminary and incomplete data made
available from the NIOSH/NCI study do not demonstrate any excess lung
cancer associated with DPM exposure. Even if Dr. Chase is correct,
however, this may merely reflect limitations of the preliminary and
incomplete data upon which his analysis relies. Because necessary data
were not yet available, the Chase analysis was unable to consider a
possible healthy worker effect, occupationally unexposed workers within
the cohort, or potentially important variations in exposure intensity
and duration. When the NIOSH/NCI study is completed, we are confident
that it will take all these factors into account in accordance with the
MSHA concludes that the data on which Dr. Chase's analysis is based
are inadequate for identifying or assessing the relationship between
occupational DPM exposure and excess lung cancer mortality. These
incomplete data provide little insight into what a comprehensive
analysis of the NIOSH/NCI study results will ultimately show, when
carried out in accordance with the study protocol.
Boffetta and Silverman (2001) performed a meta-analysis of 44
independent results from 29 distinct studies of bladder cancer in
occupational groups with varying exposure to diesel exhaust. Studies
were included only if there were at least five years between time of first
exposure and development of bladder cancer.
Separate quantitative meta-analyses were performed for heavy
equipment operators, truck drivers, bus drivers, and studies with semi-
quantitative exposure assessments based on a job exposure matrix (JEM).
The overall relative risk (RR) for heavy equipment operators was RR =
1.37 (95% CI: 1.05-1.81); for truck drivers, RR = 1.17 (1.06-1.29); for
bus drivers, RR = 1.33 (1.22-1.45); and for JEM, RR = 1.13 (1.0-1.27).
A quantitative meta-analysis was also performed on 8 independent
studies showing results for ``high'' diesel exposure. The combined
results were RR = 1.23 (1.12-1.36) for ``any exposure'' and RR = 1.44
(1.18-1.76) for ``high exposure.''
The authors discovered a strong indication of publication bias for
truck and bus driver studies, a tendency for studies to be published
only when they showed a positive result. However, the summary RR for
the seven largest truck or bus driver studies was 1.26 (1.18-1.34),
which is very close to the RR based on all 27 truck or bus driver
results. There was no indication of publication bias for studies with
semi-quantitative exposure assessments.
The results of this meta-analysis suggest a statistically
significant association between diesel exposure and an elevated risk of
bladder cancer not fully explained by publication bias. Nevertheless,
potential confounding by vibration, dietary factors, and infrequency of
urination among drivers preclude a causal interpretation of this
Not included in this meta-analysis was a study by Zeegers et al.
(2001). This was a prospective case-cohort study involving 98 cases of
bladder cancer among men occupationally exposed to diesel exhaust. A
cohort of 58,279 men who were 55 to 69 years old in 1986 was followed
up through December 1992. Exposure was assessed by job history given on
a self-administered questionnaire, combined with experts' assessment of
the exposure probability for each job. A ``cumulative probability of
exposure'' was determined by multiplying job duration by the
corresponding exposure probability. Four categories of relative
cumulative exposure probability were defined: none, lowest third,
middle third, and highest third. Relative risks were adjusted for age,
cigarette smoking, and exposure to other occupational risk factors.
The relative risk for the category with highest cumulative
probability of exposure was RR = 1.17 (95% CI: 0.74-1.84). In light of
the meta-analysis results described above, the lack of statistical
significance found in this study may be due to low statistical power
for detecting diesel exhaust effects, combined with nondifferential
errors in the exposure assessment.
As with the epidemiological studies on diesel exposure and bladder
cancer considered in the meta-analysis, no adjustment was made in this
study for infrequency of urination or for dietary patterns possibly
associated with occupations having diesel exposures. Therefore, this
study, like the meta-analysis performed by Boffetta and Silverman, has
no impact on the 2001 risk assessment.
Ojaj[auml]rvi et al. (2000) performed a meta-analysis of 161
independent results from 92 studies on the relationship between diesel
exhaust exposure and pancreatic cancer. No elevated risk was associated
with diesel exposure. The combined relative risk was RR = 1.0 (95% CI:
0.9-1.3). This result is consistent with the 2001 risk assessment,
which identified lung cancer and bladder cancer as the only forms of
cancer for which there was evidence of an association with DPM
4. Mechanisms of Toxicity
Table VI-12 describes 15 DPM toxicity studies published after the
2001 risk assessment and cited in the 2003 NPRM. Table VI-12 also
describes a 16th toxicity study (Arlt et al., 2002), which was cited by
Dr. Jonathan Borak in comments submitted by MARG. All of these studies
lend some degree of support to the conclusions of the 2001 risk
assessment. In addition to briefly describing each study and its key
results, the table identifies the agent(s) of toxicity investigated and
indicates how the results support the risk assessment by categorizing
the toxic effects and/or markers of toxicity found. The categories used
to classify toxic effects are: (A) Immunological and/or allergic
reactions, (B) inflammation, (C) mutagenicity and/or DNA adduct
formation, (D) induction of free oxygen radicals, (E) airflow
obstruction; (F) impaired clearance; (G) reduced defense mechanisms;
and (H) adverse cardiovascular effects.
Table VI-12.--Studies on Toxicological Effects of DPM Exposure, 2000-2002
Agent(s) of Toxic
Authors, year Description Key results toxicity effect(s) * Limitations
Al-Humadi et al., 2002....... IT instillation Exposure to DPM DPM and carbon A ...............
in rats of 5 mg/ or carbon black
kg saline, DPM, black augments particles.
or carbon black. OVA
(of DPM) may
Arlt et al., 2002............ In Vitro and in Increased DNA 3-NBA, a C No DPM used.
Vivo: adduct constituent of
investigation formation due the organic
of metabolic to in the fraction of
activation of 3- presence of DPM.
nitrobenzanthro human N,O
ne (3-NBA) by acetyltransfer
human enzymes. ases and
B[uuml]nger et al., 2000..... In Vitro: Production of DE generated C ...............
assessment of black carbon from diesel
content of and engine.
polynuclear polynuclear DPM collected
aromatic aromatic on filters and
compounds and compounds that soluble
mutagenicity of are mutagenic; organic
DPM generated correlation extracts
from four with sulfur prepared.
fuels, Ames content of
assay used. fuel and
Carero et al., 2001.......... In Vitro: DNA Damage DPM, urban C ...............
assessment of produced, but particulate
DPM, carbon no matter (UPM),
black, and cytotoxicity and carbon
urban produced. black (CB).
particulate DPM, UPM
matter purchased from
genotoxicity, NIST, CB
human alveolar purchased from
Castranova et al., 2001...... In Vitro: DPM depresses No information D, F, G ...............
assessment of antimicrobial on generation
DPM on alveolar potential of of DPM.
macrophage macrophages, (details may be
functions and thereby found in
role of increasing previous
adsorbed susceptibility publications
chemicals; rat of lung to from this lab).
In Vivo: effect due to
assessment of adsorbed
DPM on alveolar chemicals
macrophage rather than
functions and carbon core of
role of DPM.
Fujimaki et al., 2001........ In Vitro: Adverse effects DE generated A Sensitization
assessment of of DE on from diesel to OA via IP
cytokine cytokine and engine. injection.
production, antibody DPM, CO2, SO2, Changes in
spleen cells production by and NO/NO2/NOx pulmonary
used. creating an measured. function not
In Vivo: imbalance of assessed.
assessment of helper T-cell
to OA and
exposure to 1.0
mg/mg \3\ DE
for 12 hr/day,
over 4 weeks,
Gilmour et al., 2001......... In Vivo: Exposure to Woodsmoke, oil A, B No DPM used.
assessment of woodsmoke furnace
infectivity and increased emissions, and
allergenicity susceptibility residual oil
following to and fly ash (ROFA)
exposure to severity of used.
woodsmoke, oil streptococcal
emissions, or exposure to
residual oil residual oil
fly ash, mouse fly ash
model used, IT pulmonary
used in rats. ty reactions.
Hsiao et al., 2000........... In Vitro: Seasonal PM collected C No DPM used.
assessment of variations in Hong Kong area
cytotoxic PM, in their and solvent-
effects (cell solubility, extractable
proliferation, and in their organic
DNA damage) of ability to compounds used.
PM2.5 (fine PM produce
and PM2.5-10 cytotoxicity.
(coarse PM), Long-term
rat embryo exposure to
cells used. doses of PM
may lead to
of DNA lesions.
Kuljukka-Rabb et al., 2001... In Vitro: Temporal and Some DPM C Use of only
assessment of dose-dependent purchased from soluble
adduct DNA adduct NIST, some DPM organic
formation formation by collected on fraction of
following PAHs. filters from DPM.
exposure to Carcinogenci diesel
DPM, DPM PAHs from vehicle, and
extracts, diesel solvent-
benzo[a]pyrene, extracts lead extractable
or 5-methyl- to stable DNA organic
chrysene, adduct compounds used.
Moyer et al., 2002........... In Vivo: 2-phase Induction and/ Indium B, H Nine
retrospective or phosphide, particulate
study, review exacerbation cobalt sulfate compounds
of NTP data of arteritis heptahydrate, selected to
from 90-day and following vanadium represent al
2-yr exposures chronic pentoxide, PM.
to exposure gallium
particulates, (beyond 90- arsenide,
use of mouse day) to nickel oxide,
inhalation particulates. nickel
Saito et al., 2002........... In Vivo: DE alters DE generated A ...............
assessment of immunological from diesel
cytokine responses in engine.
expression the lung and DPM, CO, SO2
following may increase and NO2
exposure to DE susceptibility measured.
(100 [mu]g/m\3\ to pathogens,
or 3 mg/m\3\ low-dose DE
DPM) for 7-hrs/ may induce
day x 5 days/wk allergic/
x 4 wks, mouse asthmatic
Sato et al., 2000............ In Vivo: DE produced DE generated C ...............
assessment of lesions in DNA from light-
mutant and was duty diesel
frequency and mutagenic in engine.
mutation rat lung. Concentration
spectra in lung of suspended
following 4-wk particulate
exposure to 1 matter (SPM)
or 6 mg/m\3\ measured, 11
DE, transgenic PAHs and
rat ihalation nitrated PAHs
model used. identified and
Van Zijverden et al., 2000... In Vivo: DPM skew immune DPM, carbon A Questionable
assessment of response black relevance of
immuno- toward T particles exposure route
modulating helper 2 (Th2) (CBP) and (sc
capacity of side, and may silica injection).
DPM, carbon facilitate particles
black, and initiation of (SIP) used.
silica allergy. DPM donated by
mouse model University,
used (sc CBP and SIP
injection into purchased from
hind footpad). BrunschwichChe
mie and Sigma.
Vincent et al., 2001......... In Vivo: Increases in Diesel soot, H ...............
assessment of endothelin-1 carbon black
cardiovascular and -3 (two and urban air
effects vasoregulators particulates
following 4-hr ) following used.
exposure to 4.2 ambient urban Diesel soot
mg/m\3\ diesel particulates purchased from
soot, 4.6 mg/ and diesel NIST, carbon
m\3\ carbon soot exposure. black donated
black, or 48 mg/ Small increases by University
m\3\ ambient in blood of California,
urban pressure urban air
particulates, following particulates
rat inhalation exposure to collected in
model used. ambient urban Ottawa.
Walters et al., 2001......... In Vivo: Dose and time- DPM, PM, and A, B ...............
assessment of dependent coal fly ash
airway changes in used.
reactivity/ airway DPM purchased
responsiveness, responsiveness from NIST, PM
and BAL cells and collected in
and BAL inflammation Baltimore, and
cytokines following coal fly ash
following exposure to PM. obtained from
exposure to 0.5 Increase in BAL Baltimore
mg/mouse cellularity power plant.
aspirated DPM, following
ambient PM, or exposure to
coal fly ash. DPM, but
Whitekus et al., 2002........ In Vitro: Thiol DE generated A, D Changes in
assessment of antioxidants from light- pulmonary
ability of six (given as a duty diesel function
antioxidants to pretreatment) engine, DPM associated
interfere in inhibit collected, with
DPM-mediated adjuvant dissolved in sensitization
oxidative effects of DPM saline, and not assessed.
stress, cell in the aerosolized.
cultures used. induction of
In Vivo: OA
assessment of sensitization.
to OA and/or
(A) Immunological and/or allergic reactions.
(C) Mutagenicity/DNA adduct formation.
(D) Induction of free oxygen radicals cardiovascular effects.
(E) Airflow obstruction.
(F) Impaired clearance.
(G) Reduced defense mechanisms.
In addition to the new toxicity studies, four new reviews on
various aspects of the scientific literature related to mechanisms of
DPM toxicity were cited in the 2003 NPRM. These are listed in Table VI-
13. Two of these reviews (ILSI, 2000 and Oberdoerster, 2002) focus on
the applicability of the DPM rat toxicity studies to low-dose
extrapolation for humans and conclude that such extrapolation is not
appropriate. Since the 2001 risk assessment does not attempt to make
any such extrapolation, these reviews do not affect MSHA's conclusions.
As noted in the 2001 risk assessment, evidence that the carcinogenic
effects of DPM in rats are due to overload of the rats' lung clearance
mechanism does not rule out a mutagenic mechanism of carcinogenesis at
lower exposure levels in other species. The other two review articles
generally support the discussion in the 2001 risk assessment of
inflammation responses due to DPM exposures.
Table VI-13.--Review Articles on Toxicological Effects of DPM Exposure, 2000-2002
Agent(s) of Toxic effects
Authors, year Description Conclusions toxicity *
ILSI Risk Science Institute Review of rat No overload of rat Poorly soluble
Workshop Participants, 2000. inhalation studies lungs at lower particles
on chronic lung doses of DPM nonfibrous
exposures to DPM and no lung cancer particles of low
and to other hazard anticipated acute toxicity
poorly soluble at lower doses. and not directly
nonfibrous genotoxic (PSPs).
particles of low
that are not
Nikula, 2000.................... Review of animal Species differences DE, carbon black, B, F
inhalation studies in pulmonary titanium dioxide,
on chronic retention patterns talc and coal
exposures to DE, and lung tissue dust.
carbon black, responses
titanium dioxide, following chronic
talc and coal dust. exposure to DE.
Oberdoerster, 2002.............. In Vivo: review of High-dose rat lung Fibrous particles,
toxicokinetics and tumors produced by and nonfibrous
effects of fibrous poorly soluble particles that
and nonfibrous particles of low are poorly
particles. cytotoxicity soluble and have
(e.g., DPM) not low cytotoxicity
appropriate for (PSP).
overload occurs in
rodents at high
Veronesi and Oortigiesen, 2001.. In Vitro: review of Pulmonary receptors PM: residual oil A, B
nasal and stimulated/ fly ash,
pulmonary activated by PM, woodstove
innervation leading to emissions,
(receptors) and inflammatory volcanic dust,
pulmonary responses. urban ambient
responses to PM, particulates,
mainly BEAS cells coal fly ash, and
sensory neurons and oil fly ash.
(A) Immunological and/or allergic reactions
(C) Mutagenicity/DNA adduct formation
(D) Induction of free oxygen radicals
(E) Airflow obstruction
(F) Impaired clearance
(G) Reduced defense mechanisms
(H) Adverse cardiovascular effects.
D. Significance of Risk
The first principal conclusion of the 2001 risk assessment was:
Exposure to DPM can materially impair miner health or functional
capacity. These material impairments include acute sensory
irritations and respiratory symptoms (including allergenic
responses); premature death from cardiovascular, cardiopulmonary, or
respiratory causes; and lung cancer.
MSHA agrees with those commenters who characterized the weight of
evidence from the most recent scientific literature as supporting or
even strengthening this conclusion. Furthermore, this conclusion has
also been corroborated by comprehensive scientific literature reviews
carried out by other institutions and government agencies.
In 2002, for example, the U.S. EPA, with the concurrence of its
Clean Air Scientific Advisory Committee (CASAC), published its Health
Assessment Document for Diesel Engine Exhaust (EPA, 2002). With respect
to sensory irritations, respiratory symptoms, and immunological
effects, this document concluded that:
At relatively high acute exposures, DE [diesel exhaust] can cause
acute irritation to the eye and upper respiratory airways and
symptoms of respiratory irritation which may be temporarily
debilitating. Evidence also shows that DE has immunological toxicity
that can induce allergic responses (some of which are also typical
of asthma) and/or exacerbate existing respiratory allergies. [EPA,
In 2003, the World Health Organization (WHO) issued a review report
on particulate matter air pollution and health. WHO concluded that
``fine particles (commonly measured as PM2.5) are strongly
associated with mortality and other endpoints such as hospitalization
for cardiopulmonary disease, so that it is recommended that air quality
guidelines for PM2.5 be further developed.'' (WHO, 2003)
In the 10th edition of its Report on Carcinogens, the National
Toxicology Program (NTP) of the National Institutes of Health formally
retained its designation of diesel exhaust particulates as ``reasonably
anticipated to be a human carcinogen.'' (U.S. Dept. of Health and Human
Services, 2002) The report noted that:
Diesel exhaust contains identified mutagens and carcinogens both in
the vapor phase and associated with respirable particles. Diesel
exhaust particles are considered likely to account for the human
lung cancer findings because they are almost all of a size small
enough to penetrate to the alveolar region.
* * * Because of their high surface area, diesel exhaust
particulates are capable of adsorbing relatively large amounts of
organic material * * * A variety of mutagens and carcinogens such as
PAH and nitro-PAH * * * are adsorbed by the particulates. There is
sufficient evidence for the carcinogenicity for 15 PAHs (a number of
these PAHs are found in diesel exhaust particulate emissions) in
experimental animals. The nitroarenes (five listed) meet the
established criteria for listing as ``reasonably anticipated to be a
human carcinogen'' based on carcinogenicity experiments with
laboratory animals. [U.S. Dept. of Health and Human Services, 2002]
Similarly, EPA's 2002 Health Assessment Document for Diesel Engine
Exhaust concluded that diesel exhaust (as measured by DPM) is ``likely
to be a human carcinogen.'' Furthermore, the assessment concluded that
``[s]trong evidence exists for a causal relationship between risk for
lung cancer and occupational exposure to D[iesel]E[xhaust] in certain
occupational workers.'' (EPA, 2002, Sec. 9, p. 20)
Although most commenters agreed that the adverse health effects
associated with miners' DPM exposures warranted an exposure limit, some
commenters continued to challenge the scientific basis for linking DPM
exposures with an increased risk of lung cancer. An industry trade
group submitted a critique of the 2001 risk assessment by Dr. Jonathan
Borak, and this critique was endorsed by several other commenters
representing the mining industry. The following discussion addresses
Dr. Borak's comments in the same order that he presented them.
1. Dr. Borak suggested that MSHA should have classified studies
into 3 categories: positive, negative, and inconclusive. He indicated
that MSHA's classification was asymmetric in the way that it classified
studies as ``positive'' or ``negative,'' thereby distorting the results
of MSHA's tabulation and nonparametric sign test, as presented in the
2001 risk assessment.
This comment was apparently based on a misunderstanding of how MSHA
classified a study as ``negative'' for purposes of the sign test. In
describing MSHA's criterion for classifying a study as negative, Dr.
Borak quoted a passage from the 2001 risk assessment that actually
pertained to a statistically significant negative study. The
tabulations to which Dr. Borak referred symmetrically counted
epidemiologic results as positive or negative based on whether the
reported relative risk or odds ratio fell above or below 1.0.
2. Dr. Borak stated that ``MSHA approached the analysis as though
any study failing to document a protective effect of diesel must
perforce be evidence of a harmful effect.''
This statement is false and stems from Dr. Borak's misunderstanding
of the symmetric criteria for MSHA's tabulations, as explained above.
Furthermore, Dr. Borak's discussion of statistical significance and
hypothesis testing in connection with this comment is applicable to
evaluating the results of a single study--not to risk assessment based
on combining multiple results.
To evaluate the statistical significance of the aggregated
epidemiologic evidence, the 2001 risk assessment relied largely on two
meta-analyses (Bhatia et al., 1998; Lipsett and Campleman, 1999). MSHA
applied the nonparametric sign test to its tabulation of all 47 studies
in order to roughly summarize the combined evidence.
3. Dr. Borak quoted the 2001 risk assessment as stating that ``MSHA
regards a real 10% increase in the risk of lung cancer (i.e., a
relative risk of 1.1) as constituting a clearly significant health
hazard.'' He then stated that the concept of a ``real 10-percent
increase'' is ``actually undefined and subjective.''
Dr. Borak paraphrased language in the 2001 risk assessment,
substituting a ``reported'' 10% increase for a ``real'' 10% increase
(top of his p. 5). The risk assessment's distinction between
``reported'' and ``real'' relative risks is important and corresponds
to the fundamental distinction between a statistical estimate and the
quantity being estimated.
Contrary to Dr. Borak's characterization, the risk assessment
recognized that epidemiological results are often subject to a great
deal of statistical uncertainty. Such uncertainty can be expressed by
means of a confidence interval for the ``real'' value being estimated
by a ``reported'' result. For example, a reported relative risk (RR) of
1.5 estimates the real relative risk underlying a particular study, for
which a 95% confidence interval might be 1.3 to 1.7. This interval is
designed to circumscribe the real relative risk with 95% probability.
A 95% confidence interval for the real relative risk may be so
broad (e.g., 0.8 to 1.4) as to overlap 1.0 and thereby render the
reported result statistically non-significant. Because of the
statistical uncertainty associated with a reported RR, extremely large
study populations are required in order to obtain statistically significant
results when the real relative risk is near 1.0. The point being made
in the passage that Dr. Borak quoted and then incorrectly paraphrased
is that notwithstanding this statistical uncertainty, a real (as
opposed to merely reported) 10% increase in the risk of lung cancer
would constitute a clearly significant health effect. Therefore,
reported results whose associated confidence intervals overlap 1.1 are
consistent with potential health effects that are sufficiently large to
be of practical significance.
4. Dr. Borak asserted that ``* * * Federal Courts have held that
relative risks of less than 2.0 are not sufficient for showing
causation * * * but MSHA has rejected that view.''
MSHA has not rejected the view expressed in the court decisions to
which Dr. Borak alluded. Daubert v. Merrell Dow Pharmaceuticals, 509
U.S. 579 (1993); and Hall v. Baxter Healthcare Corp., 947 F Supp. 1387
(1996). As explained in the 2001 risk assessment, these decisions
pertain to establishing the specific cause of disease for a particular
person and not to establishing the increased risk attributable to an
exposure. (FR 66 at 5787-5789) This distinction was illustrated by two
analogies in the 2001 risk assessment: (1) There is low probability
that a particular death was caused by lighting, but exposure to
lighting is nevertheless hazardous; and (2) a specific smoker may not
be able to prove that his or her lung cancer was ``more likely than
not'' caused by radon exposure, yet radon exposure significantly
increases the risk--especially for smokers. (FR 66 at 5787) As stated
in the 2001 risk assessment, the court decisions are inapplicable
because ``[t]he excess risk of an outcome, given an excessive exposure,
is not the same thing as the likelihood that an excessive exposure
caused the outcome in a given case.'' (FR 66 5787)
Dr. Borak ignored MSHA's explanation of why the federal court
rulings do not apply to the 2001 risk assessment. Instead, he attempted
to differentiate the available epidemiologic studies on diesel exposure
and lung cancer from examples, presented in the risk assessment, of
studies reporting RR less than 2.0 that were nevertheless instrumental
in previous clinical and public health policy decisions. For example,
Dr. Borak pointed out that all ten of the results cited on the
relationship between smoking and cardiovascular-related deaths achieved
statistical significance. The risk assessment presented these examples,
however, only to support the position that there is ``ample precedent''
for utilizing studies with RR less than 2.0 in a risk assessment. This
was in response to comments urging MSHA to ignore all such results,
even the many results with RR less than 2.0 that were also
statistically significant. Thus, the ten results linking smoking to
cardiovascular deaths, eight of which involved RR less than 2.0,
adequately serve their intended illustrative purpose. Similarly, Dr.
Borak's discussion of radon studies is not germane to their use as
examples of studies with RR less than 2.0 that have not been generally
discounted. Although the residential radon studies cited may, as Dr.
Borak suggests, have been more powerful and had better exposure
assessments than those available for DPM, they nevertheless demonstrate
that there has been no blanket rejection of epidemiologic results
whenever RR is less than 2.0.
5. Dr. Borak objected to what he termed MSHA's ``reliance on the
`healthy worker effect' [HWE] to explain the finding of small or no
differences in various studies.'' He argued that ``[a]s a result, MSHA
has biased its own evaluation of this literature in a manner that
exaggerates the alleged human cancer risks of DPM, while diminishing
studies that are not directly supportive of the MSHA perspective.''
The 2001 risk assessment expresses a clear preference for studies
using internal comparisons or well-matched cases and controls--studies
in which the question of whether an HWE adjustment is desirable does
not even arise. In fact, internal comparisons or matched cases and
controls were utilized in all eight of the epidemiological studies
identified in the risk assessment as presenting ``the best currently
available epidemiological evidence.'' In contrast, the risk assessment
identified six negative (i.e., RR or OR < 1.0) studies (out of 47) and
noted that all six relied on unmatched cases and controls or on
external comparisons to general populations, with no allowance for any
potential HWE. However, potential bias due to HWE was not the only
weakness identified in these six studies. The assessment also noted
that five of the six studies had low statistical power due to a small
study population, insufficient allowance for latency, or both.
Furthermore, the assessment noted that all six of these negative
studies contained weak DPM exposure assessments and failed to adjust
for potentially different patterns of tobacco smoking in the disparate
groups being compared. Dr. Borak did not dispute MSHA's exclusion of
these six studies from the rank of best available epidemiologic
More specifically, Dr. Borak objected to a relatively simple method
of adjusting for the HWE used in one part of a meta-analysis by Bhatia
et al. (1998) and also in some of the individual studies cited in the
risk assessment. Dr. Borak noted that ``most epidemiologists agree that
the effects of selection bias are generally more important early in a
person's work life and do not apply equally to all diseases and disease
processes.'' Citing the adjustment formula from Bhatia et al. (1998),
Dr. Borak claimed that it is ``implicit throughout the MSHA
discussion'' that ``the effects of HWE on observed lung cancer
mortality are essentially equivalent (i.e., proportional) to its
effects on mortality from all causes.''
Although most epidemiologists may agree selection biases do not
apply equally to all diseases, this does not render consideration of
HWE irrelevant to epidemiologic studies of lung cancer. Health Effects
Institute (HEI) (1999) states that ``[w]orker mortality tends to be
below average for all major causes of death.'' The 2001 risk assessment
accepted a proportional adjustment only insofar as it was utilized in
some of the published epidemiological studies. Although Dr. Borak may
be correct that compensating for HWE is not really so simple, a
proportional adjustment may nevertheless be better than no adjustment
at all. MSHA did not itself make any such adjustments or otherwise
attempt to quantify the impact of HWE in any of the studies. MSHA did,
however, accept HWE adjustments as they appeared in published studies.
Although he did not explicitly say so, Dr. Borak presumably shares
what he says is ``the general view that studies of cancer, particularly
lung cancers, are not much affected by HWE.'' This view, however, is
not universal. It is not, for example, shared by HEI (1999) or U.S. EPA
(2002). Dr. Borak dwelled on pre-employment interviews and health exams
as a source of HWE that would probably not apply to lung cancer
studies, but pre-employment health screenings are not, after all, the
only potential source of bias leading to HWE. Dr. Borak did not dispute
the proposition that HWE reflects a potential bias when a working
population is compared to a more general control population, or that
this may be one of several factors contributing to a lack of positive
results or statistical significance in some studies. As he has
suggested, the potential impact of HWE in lung cancer studies may be
greatest among those involving the shortest latency allowances and/or follow-up times.
6. In the study published by S[auml]verin et al. (1999), exposure
measurements were obtained in 1992, whereas ``the mines ceased
production in 1991'' when ``most of the miners were dismissed and
abandoned underground work and exposure.'' Based on this apparent
discrepancy, Dr. Borak questioned the argument used by S[auml]verin et
al., and accepted in the risk assessment, to justify their assumption
that their exposure measurements were representative of exposures from
1970 to 1991. Dr. Borak speculated that the 1992 exposure measurements
were likely to have been made during a ``staged simulation'' and that
these measurements may have underestimated DPM levels under conditions
of routine production.
To resolve this issue, MSHA contacted Dr. S[auml]verin directly and
asked him to explain the sequence of events relating to mine closures
and exposure measurements. Dr. Saverin replied as follows:
* * * [t]he full potash production of millions of tons per year in
the seventies and eighties declined in the years after 1989, the
official closing date being in 1991. But until 1994, there was a lot
of mining activity underground because a mine cannot be abandoned
immediately. So, in 1992, we had no problems to find exposure
conditions not merely similar to but exactly like the routine-
production situation before. Thus, we did not have to rely on any
staged simulation but made our measurements as state of the art
requires. [S[auml]verin, R. 2005]
Thus, despite any ambiguity in the published article, Dr. S[auml]verin
maintains that the 1992 measurements were obtained under normal
production conditions and were fully representative of exposures from
1970 through 1991. MSHA accepts Dr. S[auml]verin's assessment.
As stated in the 2001 risk assessment, NIOSH commented that
``[d]espite the limitations discussed * * * the findings from the
S[auml]verin et al. (1999) study should be used as an alternative
source of data for quantifying the possible lung cancer risks
associated with Dpm exposures.'' MSHA is not relying on any single
study but, instead, is basing its evaluation on the weight of evidence
from all available data.
7. Dr. Borak identified a number of weaknesses and limitations in
the epidemiologic studies by S[auml]verin et al. (1999) and Johnston et
al. (1997). Despite their shortcomings, the 2001 risk assessment ranked
these two studies among the eight ``that provide the best currently
available epidemiologic evidence.''
As Dr. Borak indicated, all of the weaknesses and limitations he
identified were recognized and discussed in the 2001 risk assessment.
The risk assessment consistently and repeatedly emphasized that the
strength of evidence relating DPM exposure to an increased risk of lung
cancer lies not in any individual study but in the cumulative weight of
the research literature taken as a whole. As stated in the risk
* * * MSHA recognizes that no single one of the existing
epidemiologic studies, viewed in isolation, provides conclusive
evidence of a causal connection between DPM exposure and an elevated
risk of lung cancer in humans. Consistency and coherency of results,
however, do provide such evidence. An appropriate analogy for the
collective epidemiologic evidence is a braided steel cable, which is
far stronger than any of the individual strands of wire making it
up. (66 FR at 5825)
Both of the additional epidemiological studies cited in the 2003
NPRM specifically relating DPM exposures to lung cancer (Gustavsson et
al., 2000 and Boffetta et al., 2001) found statistically significant
positive results. The 2002 EPA document, which was compiled too early
to consider these two newest studies, concluded that even at the far
lower levels typically encountered in ambient air, ``[t]he available
evidence [from toxicity studies and occupational epidemiology]
indicates that chronic inhalation of DE is likely to pose a lung cancer
hazard to humans.''
This conclusion has now received important additional confirmation
from a large scale mortality study involving exposure to combustion-
related fine particulate air pollution (Pope et al., 2002). This study,
which included estimates of lung cancer effects, was cited in the NPRM
but not considered in either the 2001 risk assessment or the 2002 EPA
document. As described earlier, a statistically significant exposure-
response relationship was discovered between chronic PM2.5
exposure in the ambient air and an increased risk of lung cancer. This
finding is especially significant for confirming causality because it
represents an entirely new source of evidence not subject to unknown
biases that might tend to distort occupational epidemiology results in
the same direction.
Dr. Borak also stated that presently available data are
insufficient to establish an exposure-response relationship for lung
cancer that would justify setting the PEL at any specific level. The
2001 risk assessment recognizes uncertainty in lung cancer exposure-
response and presents a broad range of estimated exposure-response
relationships (66 FR at 5852-53). Even the lowest estimate shows
unacceptable risk at levels commonly encountered in underground mines.
Lack of a definitive exposure-response relationship means MSHA cannot
precisely distinguish differences in health effects--e.g., between
50DPM [mu]g/m3 and 100DPM [mu]g/
m3. Nevertheless, as explained below, MSHA can confidently
say that exposures above the interim PEL are significantly more
hazardous than exposures below the interim PEL.
The second principal conclusion of the 2001 risk assessment was:
At DPM levels currently observed in underground mines, many miners
are presently at significant risk of incurring these material
impairments due to their occupational exposures to DPM over a
As described in Section VI.B, two new bodies of exposure data have been
compiled since promulgation of the 2001 rule. Comparison of these data
is not straightforward, since they employed different methods for
measuring DPM. Nevertheless, the data suggest that exposure levels in
many underground M/NM mines have dropped significantly, as compared to
the 1989-1999 period covered by the 2001 risk assessment.
The 2001 risk assessment quantified excess lung cancer risk based
on a mean DPM concentration of 808 [mu]g/m3. This was based
on 355 MSHA area and personal samples collected in production areas and
haulageways at 27 underground M/NM mines between 1989 and 1999. Nearly
all of these samples were collected without an impactor and analyzed
for DPM content using the RCD method. The new samples, on the other
hand, were collected with an impactor and analyzed for TC or EC using
NIOSH Method 5040. To see how more recent exposure levels tie into the
quantitative exposure-response models used in the 2001 risk assessment,
it is necessary to convert sample results from both new sources of
exposure data to approximate DPM concentrations.
Samples from the 31-Mine Study were collected in 2001 using an
impactor and were analyzed by NIOSH Method 5040. These samples showed a
mean DPM concentration of 432 [mu]g/m\3\--assuming, as in the 2001 risk
assessment, that TC comprises 80 percent of total DPM. Excluding the
samples from trona mines, which were found to have significantly lower
DPM levels than the other 27 underground M/NM mines with valid samples,
the mean DPM concentration was approximately 492 [mu]g/m\3\.\7\
\7\ These values may be somewhat inflated due to the old
``crimped foil'' SKC sampler design used for many of the samples
collected during the 31-Mine Study. As explained elsewhere in this
preamble, this design resulted in lower-than-expected filter deposit
areas in many cases, leading to overestimates of the corresponding
TC concentrations. (The SKC sampler design was eventually modified
by substituting a retainer ring for the crimped foil. However, the
systematic errors in deposit area observed during the 31-Mine Study
have no bearing on the ``paired punch comparison'' used in that
study to evaluate analytical measurement precision.)
The other, more recent and more extensive, body of DPM exposure
data considered here consists of 1,194 baseline samples obtained at 183
mines in 2002-2003. These samples were all collected using a
submicrometer impactor and analyzed by NIOSH Method 5040. Assuming that
TC [ap]1.3 x EC and, as before, that TC comprises about 80 percent of
the DPM, the mean DPM concentration observed was approximately 320
[mu]g/m\3\.\8\ MSHA considers the baseline sampling results to be more
broadly representative of DPM concentrations currently experienced by
underground M/NM miners than the generally higher DPM concentrations
reported in the 31-Mine Study. Since the baseline samples were
collected later, part of the apparent reduction in mean concentration
levels may be due to improved DPM controls implemented in response to
the 2001 rule.
\8\ The laboratory analysis of the baseline samples yielded two
measures of TC: TC = EC + OC and TC = 1.3 x EC. However, since the
intention under baseline sampling was to rely always on the lesser
of these two values from each sample, no precautions were taken to
avoid sampling near tobacco smoke and other substances that
potentially interfere with the use of TC = EC + OC as a surrogate
measure of DPM. Therefore, in the present discussion, MSHA is using
only the TC = 1.3 x EC value to estimate baseline DPM levels.
The 2001 risk assessment used the best available data on DPM
exposures at underground M/NM mines to quantify excess lung cancer
risk. ``Excess risk'' refers to the lifetime probability of dying from
lung cancer during or after a 45-year occupational DPM exposure. This
probability is expressed as the expected excess number of lung cancer
deaths per thousand miners occupationally exposed to DPM at a specified
mean DPM concentration. The excess is calculated relative to baseline,
age-specific lung cancer mortality rates taken from standard mortality
tables. In order to properly estimate this excess, it is necessary to
calculate, at each year of life after occupational exposure begins, the
expected number of persons surviving to that age with and without DPM
exposure at the specified level. At each age, standard actuarial
adjustments must be made in the number of survivors to account for the
risk of dying from causes other than lung cancer. Occupational exposure
is assumed to begin at age 20 and to continue, for surviving miners,
until retirement at age 65. The accumulation of lifetime excess risk
continues after retirement through the age of 85 years.
Table VI-14, taken from the 2001 risk assessment, shows a range of
excess lung cancer estimates at mean exposures equal to the interim and
final DPM limits. The eight exposure-response models employed were
based on studies by Saverin et al. (1999), Johnston et al. (1997), and
Steenland et al. (1998). Assuming that TC is 80 percent of whole DPM,
and that the mean ratio of TC to EC is 1.3, the interim DPM limit of
500 [mu]g/m\3\ shown in Table VI-14 corresponds to the 308 [mu]g/m\3\
EC surrogate limit adopted under the present rulemaking.
Table VI-14.--Excess Lung Cancer Risk Expected at Specified DPM Exposure
Levels Over an Occupational Lifetime
[Extracted from Table III-7 of the 2001 risk assessment]
Excess lung cancer deaths per
1,000 occupationally exposed
Study and statistical model -------------------------------
Final DPM Interim DPM
limit 200 limit 500
Saverin et al. (1999):
Poisson, full cohort................ 15 44
Cox, full cohort.................... 70 280
Poisson, subcohort.................. 93 391
Cox, subcohort...................... 182 677
Steenland et al. (1998):
5-year lag, log of cumulative 67 89
5-year lag, simple cumulative 159 620
Johnston et al. (1997):
15-year lag, mine-adjusted.......... 313 724
15-year lag, mine-unadjusted........ 513 783
[dagger] Assumes 45-year occupational exposure at 1,920 hours per year
from age 20 to retirement at age 65. Lifetime risk of lung cancer
adjusted for competing risk of death from other causes and calculated
through age 85. Baseline lung cancer and overall mortality rates from
The mean DPM concentration levels estimated from both the 31-Mine
Study (432-492 [mu]g/m\3\, depending on whether trona mines are
included) and the baseline samples ([ap]320 [mu]g/m\3\) fall between
the interim and final DPM limits shown in Table VI-14. All of the
exposure-response models shown are monotonic (i.e., increased exposure
yields increased excess risk, though not proportionately so).
Therefore, using the most current available estimates of mean exposure
levels, they all predict excess lung cancer risks somewhere between
those shown for the interim and final limits. Thus, despite substantial
improvements apparently attained since the 1989-1999 sampling period
addressed by the 2001 risk assessment, underground M/NM miners are
still faced with an unacceptable risk of lung cancer due to their
occupational DPM exposures.
The third principal conclusion of the 2001 risk assessment was:
By reducing DPM concentrations in underground mines, the rule will
substantially reduce the risks of material impairment faced by underground
miners exposed to DPM at current levels.
Although DPM levels have apparently declined since 1989-1999, MSHA
expects that further improvements will continue to significantly and
substantially reduce the health risks identified for miners. There is
clear evidence of DPM's adverse health effects, not only at pre-2001
levels but also at the generally lower levels currently observed at
many underground mines. These effects are material health impairments
as specified under section 101(a)(6)(A) of the Mine Act. From the
baseline sampling results, 68 out of the 183 mines (37%) had at least
one sample exceeding the interim exposure limit. Because the exposure-
response relationships shown in Table VI-14 are monotonic, MSHA expects
that industry-wide implementation of the interim limit will
significantly reduce the risk of lung cancer among miners.
Section 101(a)(6)(A) of the Mine Act requires the Secretary of
Labor in establishing health standards, to most adequately assure, on
the basis of the best available evidence, that no miner will suffer
material impairment of health or functional capacity over his or her
working life. Standards promulgated under this section must be based
upon research, demonstrations, experiments, and such other information
as may be appropriate. MSHA, in setting health standards, is required
to achieve the highest degree of health and safety protection for the
miner, and must consider the latest available scientific data in the
field, the feasibility of the standards, and experience gained under
this or other health and safety laws.
The legislative history of the Mine Act states:
This section further provides that ``other considerations'' in the
setting of health standards are ``the latest available scientific
data in the field, the feasibility of the standards, and experience
gained under this and other health and safety laws.'' While
feasibility of the standard may be taken into consideration with
respect to engineering controls, this factor should have a
substantially less significant role. Thus, the Secretary may
appropriately consider the state of the engineering art in industry
at the time the standard is promulgated. However, as the circuit
courts of appeals have recognized, occupational safety and health
statutes should be viewed as ``technology-forcing'' legislation, and
a proposed health standard should not be rejected as infeasible
``when the necessary technology looms on today's horizon''. AFL-CIO
v. Brennan, 530 F.2d 109 (3d Cir. 1975); Society of Plastics
Industry v. OSHA, 509 F.2d 1301 (2d Cir. 1975), cert. denied 427
U.S. 992 (1975).
Similarly, information on the economic impact of a health
standard, which is provided to the Secretary of Labor at a [public]
hearing or during the public comment period, may be given weight by
the Secretary. In adopting the language of [this section], the
Committee wishes to emphasize that it rejects the view that cost
benefit ratios alone may be the basis for depriving miners of the
health protection which the law was intended to insure. Rep. No. 95-
181, 95th Cong. 1st Sess. 21 (1977).
In promulgating standards, hard and precise predictions from
agencies regarding feasibility are not required. The ``arbitrary and
capricious test'' is usually applied to judicial review of rules issued
in accordance with the Administrative Procedure Act. The legislative
history of the Mine Act further indicates that Congress explicitly
intended the ``arbitrary and capricious test'' be applied to judicial
review of mandatory MSHA standards. ``This test would require the
reviewing court to scrutinize the Secretary's action to determine
whether it was rational in light of the evidence before him and
reasonably related to the law's purposes.'' S. Rep. No. 95-181, 95th
Cong., 1st Sess. 21 (1977). In achieving the Congressional intent of
feasibility under the Mine Act, MSHA may also consider reasonable time
periods of implementation. Ibid. at 21.
Though the Mine Act and its legislative history are not specific in
defining feasibility, the Supreme Court has clarified the meaning of
feasibility in the context of OSHA health standards in American Textile
Manufacturers' Institute v. Donovan (OSHA Cotton Dust), 452 U.S. 490,
508-09 (1981), as ``capable of being done, executed, or effected,''
both technologically and economically.
MSHA need only base its predictions on reasonable inferences drawn
from existing facts. In order to establish the economic and
technological feasibility of a new rule, an agency is required to
produce a reasonable assessment of the likely range of costs that a new
standard will have on an industry, and an agency must show that a
reasonable probability exists that the typical firm in an industry will
be able to develop and install controls that will meet the standard.
United Steelworkers of America, AFL-CIO-CLC v. Marshall, (OSHA Lead)
647 F.2d 1189, 1273.
B. Technological Feasibility
Courts have ruled that in order for a standard to be
technologically feasible an agency must show that modern technology has
at least conceived some industrial strategies or devices that are
likely to be capable of meeting the standard, and which industry is
generally capable of adopting. Ibid. (citing American Iron and Steel
Institute v. OSHA, (AISI-I) 577 F.2d 825 (3d Cir. 1978) at 832-35; and,
Industrial Union Dep't., AFL-CIO v. Hodgson, 499 F.2d 467 (DC
Cir.1974)); American Iron and Steel Institute v. OSHA, (AISI-II) 939
F.2d 975, 980 (DC Cir. 1991). The existence of general technical
knowledge relating to materials and methods which may be available and
adaptable to a specific situation establishes technical feasibility. A
control may be technologically feasible when ``if through reasonable
application of existing products, devices or work methods with human
skills and abilities, a workable engineering control can be applied''
to the source of the hazard. It need not be an ``off-the-shelf''
product, but ``it must have a realistic basis in present technical
capabilities.'' (Secretary of Labor v. Callanan Industries, Inc.
(Noise), 5 FMSHRC 1900, 1908 (1983)).
The Secretary may also impose a standard that requires protective
equipment, such as respirators, if technology does not exist to lower
exposures to safe levels. See United Steelworkers of America, AFL-CIO-
CLC v. Marshall, (OSHA Lead) 647 F.2d 1189, 1269 (DC Cir. 1981).
MSHA has established that it is technologically feasible to reduce
underground miners' exposures to the DPM interim permissible exposure
limit (PEL) of 308 micrograms of EC per cubic meter of air
(308EC [mu]g/m3) by using available engineering
control technology and various administrative control methods. However,
MSHA acknowledges that compliance difficulties may be encountered at
some mines due to implementation issues and the cost of purchasing and
installing certain types of controls. Therefore, this final rule
incorporates the industrial hygiene concept of a hierarchy of controls
for implementing DPM controls. To attain the interim DPM limit, mine
operators are required to install, use, and maintain engineering and
administrative controls to the extent feasible. When such controls do
not reduce a miner's exposure to the DPM limit, controls are
infeasible, or controls do not produce significant reductions in DPM
exposures, operators must continue to use all feasible engineering and
administrative controls and supplement them with respiratory
protection. When respiratory protection is required under the final
standard, mine operators must establish a respiratory protection
program that meets the specified requirements. Thus, MSHA has provided a regulatory
scheme that adequately accomplishes control of exposure under
circumstances where a mine operator cannot reduce a miner's exposure to
the interim PEL solely by use of engineering and administrative
controls, including work practices.
DPM control technology is not new to the mining industry. MSHA has
afforded the mining industry a significant period of time to implement
DPM controls. The existing DPM standard was first promulgated on
January 19, 2001 (66 FR 5706) with an effective date of July 19, 2002
for meeting the interim concentration limit of 400 micrograms of TC per
cubic meter of air. The instant rulemaking provides for a comparable EC
PEL of 308 EC [mu]g/m3. Under the settlement
agreement, MSHA allowed mine operators an additional year in which to
begin to install appropriate engineering and administrative controls to
reduce DPM levels due to feasibility constraints at that time.
Altogether, the mining industry has had over four years to institute
controls required under this rulemaking. Any controls currently used to
meet the existing concentration limit can be used to reduce miners'
exposures to the interim PEL.
MSHA acknowledges that the current DPM rulemaking record lacks
sufficient feasibility documentation to justify lowering the DPM limit
below 308 EC [mu]g/m3 at this time. Therefore,
MSHA is not lowering the limit in this rulemaking. MSHA believes that
this interim limit is reasonable, and that MSHA can document
feasibility across the affected sector of underground M/NM mines. MSHA
is continuing to gather information on the feasibility of the mining
industry to comply with a final DPM PEL of less than 308 EC
MSHA emphasizes that a DPM control may be deemed feasible, and
therefore be required by MSHA even if a miner's exposure is not reduced
to the DPM limit. Mine operators cited for DPM overexposures will
continue to be required to implement feasible engineering and
administrative controls even if these controls are not fully successful
in attaining the DPM exposure limit. In the context of this rule,
feasible DPM controls must be capable of achieving a significant
reduction in DPM. MSHA considers a significant reduction in DPM to be
at least a 25% reduction in the affected miners' exposures. Thus, for
mines that are out of compliance with the DPM interim limit, controls
would be required that attain compliance, or that achieve at least a
25% reduction in DPM exposure if it is not possible to attain
compliance by implementing feasible controls. If feasible engineering
and administrative controls are not capable of attaining compliance, or
at least of achieving a DPM exposure reduction of 25%, MSHA would not
require the implementation of those controls. In such cases, which MSHA
believes will be very limited, MSHA would require miners to be
protected using appropriate respiratory protective equipment.
Some commenters criticized the 25% threshold for a significant
reduction because it lacks a scientific basis, and that controls should
be evaluated individually in reference to site-specific conditions and
DPM levels for significance or effectiveness. MSHA notes that the 25%
threshold for DPM is lower than the 50% threshold adopted in MSHA's
noise rule. However, DPM's classification as a carcinogen justifies the
more protective 25% level for determining whether controls achieve a
significant reduction for purposes of assessing feasibility.
MSHA also notes that most of the practical and effective controls
that are currently available, such as DPM filters, enclosed cabs with
filtered breathing air, and low-emission engines will achieve at least
a 25% reduction. Other controls such as ventilation upgrades or
alternative fuel blends may achieve a 25% reduction, depending on
exposure circumstances and the specific nature of the subject control.
It should also be noted that reductions of less than 25% could be due
to normal day-to-day variations in mining operations as opposed to
reductions due to implementing a control technology. MSHA's Compliance
Guide includes the 25% significant reduction for determining
If a particular DPM control were capable of achieving at least a
25% reduction all by itself, MSHA would evaluate the costs of that
individual control to determine its economic feasibility. If a number
of controls could together achieve at least a 25% reduction, but no
individual control, if implemented by itself, could achieve a 25%
reduction, MSHA would evaluate the total costs of all controls added
together to determine their economic feasibility as a group. In
determining whether a combination of controls is economically feasible,
MSHA would consider whether the total cost of the combination of
controls is wholly out of proportion to the expected results. MSHA will
not cost the controls individually, but will combine their expected
results to determine if the 25% significant reduction criteria can be
MSHA's rulemaking record addressing feasibility includes: MSHA's
final report on the 31-Mine Study; NIOSH's peer review of the 31-Mine
Study; results from MSHA's baseline sampling at mines covered under the
DPM standard; results of MSHA's comprehensive compliance assistance
work at mining operations with implementation issues affecting
feasibility; NIOSH's conclusions on the performance of the SKC sampler
and the availability of technology for control of DPM; NIOSH's Diesel
Emissions Workshops in 2003 in Cincinnati and Salt Lake City; the
Filter Selection Guide posted on the MSHA and NIOSH Web sites; MSHA's
final report on DPM filter efficiency; NIOSH's report titled, ``Review
of Technology Available to the Underground Mining Industry for Control
of Diesel Emissions''; and, the NIOSH Phase I Isozone study titled,
``The Effectiveness of Selected Technologies in Controlling Diesel
Emissions in an Underground Mine--Isolated Zone Study at Stillwater
Mining Company's Nye Mine'' all of which were developed following
promulgation of the 2001 DPM final rule.
One other NIOSH document resulting from the DPM M/NM Partnership
became available to MSHA in April 2004. That document is titled, ``An
Evaluation of the Effects of Diesel Particulate Filter Systems on Air
Quality and Personal Exposure of Miners at Stillwater Mining Case
Study: Production Zone (Phase II Study).'' As stated in the final
The objective of Phase II of this study was to determine the effects
of those DPF systems being used on production vehicles at Stillwater
Mine on workplace concentrations of EC and regulated gases in an
actual mining application where multiple diesel-powered vehicles
operated simultaneously during full-shift mining activities.
MSHA evaluated this evidence as it relates to feasibility and found
that unlike the Phase I Isozone Study, the Phase II study does not
contain any new significant information affecting the ability of the
mining industry to comply with the requirements of this final rule.
MSHA, therefore, finds this data to be cumulative in nature and has
included it in the rulemaking record as supplemental information. MSHA
discusses the Phase II study results in more detail in this section of
the preamble. MSHA emphasizes that mine operators obtained access to
this study on the date of publication since the study was generated by
the DPM M/NM Partnership.
MSHA committed to implementing several initiatives related to enforcement
and enhancing the mining industry's ability to comply with the 2001 final rule.
Among other things, MSHA agreed that it would not issue citations for potential
violations of the interim concentration limit promulgated in the 2001 standard
until after MSHA and NIOSH were satisfied with the performance characteristics
of the SKC sampler and the availability of practical mine worthy DPM filter
technology. MSHA also agreed to provide DPM sampling training for its inspectors,
and to provide comprehensive compliance assistance to the industry through
July 19, 2003. MSHA's compliance assistance activities included:
Conducting compliance assistance meetings throughout the
country to discuss how to comply with the DPM standard;
Providing a compliance guide answering key questions;
Conducting an inventory of existing underground diesel-
Providing information to mine operators on feasible DPM
Obtaining baseline sampling results at each underground
mine covered under the standard solely for the purpose of compliance
assistance rather than for enforcement purposes.
Additional compliance assistance activities also were conducted, and
are discussed later in this section of the preamble.
During the compliance assistance period, MSHA agreed that mine
operators would not be cited for potential violations of the interim
limit provided they took good-faith steps to develop and implement a
written compliance strategy and cooperated with MSHA. Also, MSHA would
issue a noncompliance citation for exceeding the interim concentration
limit only if MSHA believed that an operator was not acting in good
faith, or if an operator failed to cooperate in the compliance
assistance. Per the agreement, after July 19, 2003, MSHA began to issue
citations for violations associated with the interim limit. During the
compliance assistance period (through July 19, 2003), MSHA did not
identify any mines that failed to take good faith steps toward
achieving compliance or cooperate with MSHA. Consequently, no citations
for violations associated with the interim limit were issued prior to
July 20, 2003.
MSHA provided DPM training to its inspectors and to the extent
possible, completed its compliance assistance activities in accordance
with the settlement agreement. During September and October 2002,
seminars covering the rule, MSHA's enforcement policy, DPM sampling,
and DPM engineering control technologies were held in Ebensburg, PA,
Knoxville, TN, Lexington, KY, Des Moines, IA, Kansas City, MO,
Albuquerque, NM, Coeur d'Alene, ID, Elko, NV, and Green River, WY. The
DPM Compliance Guide was posted on the MSHA DPM Single Source Page and
also issued as an MSHA Program Policy Letter (PPL P03-IV-1,
effective August 19, 2003). Extensive information on feasible controls
for DPM was included in the Compliance Guide/Program Policy Letter and
listed on MSHA's DPM Single Source Page for DPM. The inventory of
diesel engines was completed September 30, 2002. Baseline DPM samples
were not obtained at a remaining few mines until after July 20, 2003
primarily to allow time to cover sampling at intermittent operations.
However, enforcement sampling at these mines was delayed until after
completion of baseline sampling to provide these mine operators with
further opportunity to implement controls, if necessary.
As discussed below in this section of the preamble, both MSHA and
NIOSH are satisfied with the performance of the SKC sampler and on the
availability of practical DPM filter technology.
DPM Sampling Method. Though not under substantive review in this
rulemaking, existing Sec. 57.5061(b) establishes that MSHA will
continue to sample miners' personal exposures by using a respirable
dust sampler equipped with a submicrometer impactor and analyze samples
for the amount of EC using the NIOSH Analytical Method 5040, or any
other method that NIOSH determines gives equal or improved accuracy in
DPM sampling. The DPM sampling method is discussed in the section-by-
section portion of this preamble under Sec. 57.5060(a) addressing the
permissible exposure limit. MSHA includes a more detailed discussion of
its sampling method on its DPM Single Source Web page. Based on current
information in the rulemaking record, MSHA concludes that it has a
technologically feasible measurement method that operators and MSHA can
use to accurately determine if miners' exposures exceed the interim
Performance of the SKC Sampler. MSHA and NIOSH are satisfied with
the performance of the SKC sampler. The 31-Mine Study includes a
comprehensive discussion of MSHA's and NIOSH's work with SKC that
improved the performance of the sampler. In MSHA's final report on the
31-Mine Study, it concluded that SKC satisfactorily addressed concerns
over earlier known defects in the DPM sampling cassettes and
availability of cassettes to both MSHA and mine operators. Just prior
to and during the 31-Mine Study, NIOSH and MSHA observed that the
perimeter of the DPM deposit on the filter was not consistently
circular and varied among the SKC samplers. This resulted in a variable
and unpredictable deposit area. The cause of this was found and quite
successfully remedied allowing NIOSH to express its satisfaction with
the performance of the SKC sampler by letter of June 25, 2003, to MSHA
that states, in part:
Concurrent with the work of the partnership were research tasks to
ensure that diesel particulate matter can be accurately measured in
these mines. The SKC DPM cassette is a size selective sampler
designed to collect DPM samples that are characterized by an
aerodynamic diameter less than 0.8[mu]m, while avoiding
contamination with mineral dust. The use of the SKC sampler could
not be recommended initially because of a problem relating to
irregular deposition of DPM on the cassette sample. However, this
problem has been solved, and we are now satisfied with the
performance of the SKC sampler. The research regarding the
performance of the SKC sampler has been documented, peer-reviewed,
and is currently accepted for publication by Applied Occupational
and Environmental Hygiene Journal.
Baseline Sampling. For the 2001 standard, MSHA based its
feasibility projections on an average DPM concentration level of over
800TC [mu]g/m\3\. MSHA found in the 31-Mine Study that
miners' average TC exposure was 345 [mu]g/m\3\. MSHA's baseline
sampling revealed that miners average EC exposure was 196 [mu]g/m\3\.
The average TC exposure measured as EC + OC was 293 [mu]g/m\3\, and as
calculated by EC x 1.3 was 255 [mu]g/m\3\. MSHA believes that these
lower averages probably result from the introduction of DPFs, clean
engines, better maintenance, and the elimination of interferences as
confirmed by MSHA's compliance assistance baseline sampling. The
baseline sampling results are discussed in detail in Section V.
DPM Enforcement. MSHA believes that final Sec. 57.5060(d)
adequately addresses feasibility issues related to meeting the interim
limit of 308EC [mu]g/m\3\ under Sec. 57.5060(a). Under
these sections, MSHA has amended the type of exposure that will be
regulated along with the methods of compliance with the interim PEL to
provide mine operators with greater flexibility in reducing DPM
exposures. This final DPM rule adopts MSHA's long-standing enforcement
practice established for other exposure-based standards applicable to M/NM mines. Also, MSHA
underscores the fact that the enforcement scheme established in this
final rule also is based on the DPM settlement agreement.
In spite of the changes in this final rule that increase
flexibility, MSHA realizes that some mine operators will continue to
need on-site technical assistance. MSHA is committed to assisting these
operators in special mining situations that could affect the successful
use of DPFs or other engineering control systems. Mine operators can
request this assistance from their respective MSHA District Manager.
Additionally, MSHA concludes that the established hierarchy of
controls for complying with the DPM interim limit adequately protects
miners from exposure to DPM in those circumstances where MSHA found
control methods to be infeasible under existing Sec. 57.5060(d)(2) for
certain activities including inspection, maintenance and repair
activities. MSHA has removed from this final rule the requirement for
mine operators to apply to the Secretary of Labor for relief from
applying control technology to comply with the final DPM limit.
Instead, MSHA's hierarchy of controls strategy will result in quicker
responses to supplementing protection for miners exposed to the health
risks associated with DPM.
MSHA believes that it has sufficiently accommodated the mining
industry's needs with respect to complying with the DPM standard and
has developed an appropriate and reasonable enforcement scheme under
this rule. MSHA estimates that approximately 183 mines are covered
under the standard. These mines produce commodities such as gold,
limestone, trona, platinum, lead, silver, zinc, marble, gypsum, salt,
and potash. Based on MSHA's baseline sampling results, over 70% of
these underground mines were in compliance with the interim DPM limit.
MSHA is confident that engineering and administrative controls
(including work practice controls) exist that are capable of reducing
DPM exposures to the interim PEL of 308EC [mu]g/m\3\ in all
types of underground M/NM mines. MSHA believes that virtually all mine
operators will successfully attain compliance with the interim limit by
choosing from among various currently available feasible engineering
and administrative DPM control options, including but not limited to
DPF systems, ventilation upgrades, oxidation catalytic converters,
alternative fuels, fuel additives, enclosures such as cabs and booths
with filtered breathing air, improved diesel engine maintenance
procedures and instrumentation, diesel engines with lower DPM
emissions, various work practices and administrative controls. MSHA has
given the mining industry flexibility under the final standard in
selecting the individual or combination of DPM controls that best suit
a mine operator's specific needs, conditions, and operating practices.
MSHA received numerous comments concerning the technological
feasibility of the 2003 NPRM. Some commenters opposed any changes in
the 2001 DPM standard. A few of these commenters suggested that MSHA's
current rulemaking record does not support revising the 2001 final
rule. They believe that in order to justify a change that in their view
reduces health protection, MSHA must first make a determination that
the DPM limits established in the 2001 final rule are infeasible for
the mining industry as a whole to attain. These commenters note that,
to the contrary, MSHA fully substantiated its conclusions regarding
feasibility in the 2001 final rule.
According to these commenters, during the period from August 2001
through January 2002, MSHA stated in the final report to the 31-Mine
Study that the mean concentration of DPM was 345TC [mu]g/
m\3\, substantially below the required concentration limit of
400TC [mu]g/m\3\. These commenters pointed out that these
results were obtained at a time when MSHA believes few mining
operations had begun to implement DPM controls, or where the
implementation of such controls was in its early stages and had not yet
achieved significant reductions in DPM exposure. Other supportive
evidence noted by these commenters included the results of the baseline
sampling indicating that only 30% of the mines tested were out of
MSHA agrees that it should utilize data from its final report on
the 31-Mine Study and the baseline sampling in assessing technological
feasibility, but MSHA does not consider the mean concentration obtained
in the 31-Mine Study or the number of mines with baseline samples
exceeding the interim limit to be the definitive data sources in this
assessment. For example, although the mean concentration of DPM
reported in the final report to the 31-Mine Study was only
345TC [mu]g/m\3\, the mean DPM concentration value does not
reflect the wide range of sample results obtained between mines or
within individual mines, some of which exceeded 1000TC
[mu]g/m\3\. Likewise, although only 30% of the mines had baseline
sampling results exceeding the interim limit, MSHA expects some of
these mines may have encountered compliance difficulties due to
implementation issues relating to such factors as DPF regeneration and
retrofitting DPFs to existing pieces of equipment, and due to the costs
of purchasing and installing DPM controls.
Therefore, in assessing technological feasibility, MSHA believes it
should also consider data obtained subsequently from other sources,
including MSHA's comprehensive compliance assistance work at mining
operations, current agency enforcement experience, the NIOSH Diesel
Emissions Workshops in Cincinnati and Salt Lake City, and the NIOSH
Phase I Isozone Study. MSHA agrees with commenters who take the
position that the interim DPM limit can be attained by the industry as
a whole through implementation of feasible engineering and/or
administrative (including work practice) controls. However, MSHA does
not agree with commenters who oppose any changes to the 2001 final
Some commenters suggested that the proposed modification to the
2001 standard would reduce health protection for miners, a consequence
that Sec. 101(a)(9) of the Mine Act prohibits. MSHA disagrees. Section
101(a)(9) of the Mine Act provides that: ``No mandatory health or
safety standard promulgated under this title shall reduce the
protection afforded miners by an existing mandatory health or safety
standard.'' MSHA interprets this provision of the Mine Act to require
that all of the health or safety benefits resulting from a new standard
be at least equivalent to all of the health or safety benefits
resulting from the existing standard when the two sets of benefits are
evaluated as a whole. Int'l Union v. Federal Mine Safety and Health
Admin., 920 F.2d 960, 962-64 (DC Cir. 1990); Int'l Union v. Federal
Mine Safety and Health Admin., 931 F.2d 908, 911 (DC Cir 1991).
In fact, MSHA believes that the interim EC limit established in
this rulemaking is comparable to the existing TC limit. Correcting the
surrogate for identifying miners' exposures to DPM is critical for
protection of miners and will result in a valid DPM sample that MSHA
can adequately substantiate. MSHA's hierarchy of controls strategy in
the final rule is based on long-standing industrial hygiene practice in
both the mining industry and general industry. As implemented in this
final rule, the hierarchy of controls ensures that the most protective
means of compliance (engineering and administrative controls) are used
first, and that respiratory protection is permitted only where MSHA determines
that: Engineering and administrative controls are infeasible; controls
do not produce significant reductions in DPM exposures; or controls do
not reduce exposures to the interim DPM limit.
The DPM litigants raised their concerns to MSHA with implementation
issues related to regeneration and retrofitting exhaust after-treatment
controls on existing mining equipment. These, along with various other
compliance concerns, eventually led to the 31-Mine Study. At that time,
only a few mine operators in the U.S. had begun to implement after-
treatment control technology on their underground diesel-powered
equipment. As is often the case when unfamiliar technologies are
integrated into an industry sector, the process was slow, and at least
initially, the results were less-than-fully satisfactory. As noted
elsewhere in this section, many mine operators, for example,
experimented with DPF installations on a few pieces of equipment on a
trial basis, with mixed results at best. MSHA does not dispute these
findings, but believes that DPF failures were the result of
inappropriate DPF selection for a given application. However at the
time, these operators were convinced that DPF technology was
fundamentally deficient for application in underground mining. In an
effort to resolve a variety of issues raised by the industry that were
believed to present potential compliance problems, MSHA agreed to
conduct the 31-Mine Study.
Many commenters also claimed that MSHA's determination that the
rule is technologically feasible assumed the widespread utilization of
DPFs, which these commenters do not believe have proven mine worthy and
which may be affected by the aforementioned implementation issues. In
response, MSHA notes that while it continues to highly recommend use of
DPFs, its technological feasibility determination was based on the
application of a variety of engineering and administrative control
approaches for obtaining compliance, and was not limited to DPFs. MSHA
has determined that DPF systems are available and mine worthy for
controlling miners' exposures to DPM. As discussed later in this
section of the preamble, both MSHA and NIOSH are satisfied that DPF
systems are currently available for most mining equipment, and that
these systems can be successfully applied if mine operators make
informed decisions regarding filter selection, retrofitting, engine and
equipment deployment, operation, and maintenance, and specifically work
through issues such as in-use efficiencies, secondary emissions, engine
backpressure, DPF regeneration, DPF reliability and durability.
Implementation issues, such as DPF regeneration and retrofitting
DPFs to existing pieces of equipment, primarily affect a small number
of mines. Mines affected are those that will need to utilize DPFs to
attain compliance because other control options, such as ventilation
upgrades, low-emission engines, alternative diesel fuels, and cabs with
filtered breathing air are either infeasible at these particular mines,
or because these mine operators have already utilized these other
control options to the maximum extent feasible but have not yet
attained compliance. Since a variety of feasible control options are
available, and implementation issues relating to DPFs affect a
relatively small number of mines, the industry as a whole will not be
impeded from attaining compliance with the interim PEL.
MSHA does not dispute this early experience with DPF installations
in U.S. underground mines, and in fact, acknowledged these concerns in
the final report of the 31-Mine Study. One of the major conclusions of
the study states:
Compliance with both the interim and final concentration limits may
be both technologically and economically feasible for metal and
nonmetal underground mines in the study. MSHA, however, has limited
in-mine documentation on DPM control technology. As a result, MSHA's
position on feasibility does not reflect consideration of current
complications with respect to implementation of controls, such as
retrofitting and regeneration of filters. MSHA acknowledges that
these issues may influence the extent to which controls are
feasible. The Agency is continuing to consult with the National
Institute of Occupational Safety and Health, industry and labor
representatives on the availability of practical mine worthy filter
After completing the 31-Mine Study, however, MSHA obtained
additional documentation on DPM control technology that it had
previously lacked. This information includes data on both
implementation issues and costs, and was obtained from such sources as
MSHA's comprehensive compliance assistance activities, MSHA's
enforcement experience, and NIOSH's Diesel Emission Workshops in
Cincinnati and Salt Lake City. Also, MSHA now has in-mine data on the
filter efficiency of DPFs in U.S. mines as a result of the NIOSH Phase
I Isozone study (discussed in detail in this preamble).
Effectiveness of the DPM Estimator. MSHA's DPM Estimator is a
Microsoft[reg] Excel spreadsheet computer program that
calculates the reduction in DPM concentration that can be obtained by
implementing individual, or combinations of engineering controls in a
given production area of a mine. MSHA has repeatedly advised the mining
community throughout the DPM rulemakings that the Estimator is one of
many tools that can be used to assist mine operators with assessing
feasibility of compliance with the DPM limits. MSHA used the estimator
to support its feasibility assessment for the 2001 final rule, as well
as the feasibility section of the 31-Mine Study which is used to
support this final rule.
The analyses in the 31-Mine Study were based on the highest DPM
sample result obtained at each mine. Using the Estimator, new DPM
levels were computed for this ``worst case'' sample result based on the
application of one, or a combination of the following control
technologies: DPFs, low emission engines, and upgraded ventilation. To
adequately protect all miners even if the mine operator changes
equipment deployment schemes in the future, the methodology for the
technological feasibility analysis required all major emission sources
at a given mine, plus similar spare equipment, to be provided with the
same DPM controls that were specified for the equipment associated with
the ``worst case'' sample result.
Likewise, the economic feasibility analysis for each mine was based
on costing the same controls for all major DPM emission sources, and
similar spare equipment, as were required to reduce the ``worst case''
sample result to the compliance level. The rationale for this approach
is that if the same controls are applied to all major DPM sources and
spare equipment as are required to attain compliance for the ``worst
case'' exposures, all exposures in the mine will be reduced at least to
the compliance level, if not lower, regardless of future equipment
usage, equipment deployment, mine production levels, etc.
In the 31-Mine Study, DPFs were assumed to be capable of achieving
an 80% reduction in DPM emissions. This 80% filtration efficiency value
was based on laboratory tests. Since the 2001 final rule was
promulgated, MSHA has obtained the results of the NIOSH Phase I Isozone
Study conducted under actual in-mine testing, and which concludes that
filter efficiency is about 75% for total DPM and ranged over 88% to 90%
for EC for ceramic monolith wall-flow type DPFs of either silicon
carbide or cordierite composition. DPM reductions obtained by replacing older
existing engines with new, low-emission engines are based on the DPM
emissions of the new engine relative to the DPM emissions of the
existing engine. For instance, if a new engine emits 0.10 grams per
brake horsepower-hour (g/bhp-hr) of DPM and the existing engine emits
0.50 g/bhp-hr of DPM, the Estimator would compute a DPM reduction of
80% when the new engine replaces the existing engine. DPM reductions
obtained through ventilation upgrades are based on the new ventilation
airflow rate compared to the existing ventilation airflow rate. For
example, if the new ventilation airflow rate is 80,000 cfm and the
existing airflow rate is 40,000 cfm, the Estimator would compute a
reduction in the DPM concentration of 50%.
The Estimator was peer-reviewed during the 2001 final rulemaking
and was published both as an SME Preprint for the 1998 SME Annual
Meeting (Preprint 98-146, March 1998) and in the April 2000 SME
Journal. Its predictions have been compared to actual in-mine DPM
measurements (before and after DPM controls were implemented) with good
agreement. Indeed, one commenter who was critical of the Estimator,
nonetheless, noted that, ``The math which forms the basis for the
Estimator's calculations cannot be challenged `` total exhaust
emissions from diesel equipment (in grams/hr) when diluted with mine
ventilation air flows (in cubic feet per minute) yield an estimated DPM
concentration (in micro-gram per cubic meter) if the emissions are
perfectly mixed with the air flow.''
Despite its sound mathematical basis, this and other commenters
stated that the Estimator was flawed, and hence, the technological and
economic feasibility assessments were likewise flawed. These commenters
specifically stated that the Estimator was flawed because two inputs
utilized by the Estimator, DPM emissions (both raw and reduced via
DPFs) and air flows, are subject to interpretation and assumptions.
Furthermore, they believe that the Estimator's computations of DPM
concentrations are valid only if engine emissions are perfectly mixed
with the air flow, which they suggest does not occur in an actual mine.
MSHA disagrees with this conclusion. These commenters make an
erroneous assumption with respect to MSHA's utilization of the
Estimator. The Estimator actually incorporates two independent means of
calculating DPM levels: one based on DPM sampling data for the subject
mine, and one based on the absence of such sampling data. Where no
sampling data exist, the Estimator calculates DPM levels based on a
straightforward mathematical ratio of DPM emitted from the tailpipe (or
DPF, in the case of filtered exhaust) per volume of ventilation air
flow over that piece of equipment. This is referred to in the Estimator
as the ``Column B'' option for calculating DPM concentrations. The
commenters' observation that the Estimator fails to account for
imperfect mixing between DPM emissions and ventilating air flows is a
valid criticism of the ``Column B'' option. For this and other reasons,
the Estimator's instructions urge users to utilize the ``Column A''
option whenever sampling data are available.
In the ``Column A'' option, the Estimator's calculations are
``calibrated'' to actual sampling data. Whatever complex mixing between
DPM emissions and ventilating air flows existed when DPM samples were
obtained, are assumed to prevail after implementation of a DPM control.
This is an entirely reasonable assumption, and in fact, there is no
engineering basis to assume otherwise. Indeed, comparisons of ``Column
A'' Estimator calculations and actual DPM measurements taken in mines
before and after implementation of DPM controls have shown good
agreement, indicating that Estimator calculations do adequately
incorporate consideration for complex mixing of DPM and air flows when
the ``Column A'' option is used.
The Estimator was originally developed with both the Column A and
Column B options because at that time, the specialized equipment
required for DPM sampling, such as the submicron impactor, was not
widely available. Consequently, few mine operators were able to obtain
the in-mine DPM sample data required for utilizing the Column A option.
Now that the required sampling equipment is readily available, MSHA
strongly recommends that the Column A option be used exclusively, as
MSHA did in the 31-Mine Study. Since all Estimator analyses conducted
during the 31-Mine Study utilized the Estimator's ``Column A'' option,
the comment regarding imperfect mixing is not relevant.
The Estimator utilizes raw (an unfiltered emission) tailpipe DPM
emissions per se as an input data value only when a low-emission engine
is specified as a DPM control. For most of the mines in the 31-Mine
Study, unfiltered tailpipe DPM emissions were not factored into
Estimator analysis because a change in engines was not specified. Where
new engines were specified, MSHA based its estimate of unfiltered
tailpipe emissions on laboratory dynamometer testing conducted
according to the EPA 8-mode test duty cycle. This test is a common
standard used by government and industry for diesel engine emissions
analysis. Where actual test data were not available for a given engine,
emissions were estimated based on the type of engine (make and model,
model year, direct injection, pre-chamber, naturally aspirated,
turbocharged, electronic controlled, etc.) and horsepower. Filtered
emissions were assumed to be 20% of unfiltered tailpipe emissions,
corresponding to 80% filter efficiency. As noted above, the 80% filter
efficiency was a conservative assumption based on MSHA and other
laboratory and NIOSH in-mine test data indicating DPM efficiencies of
80% to 87% for both cordierite and silicon carbide filters. Note that
these efficiencies relate to DPM filtration. Higher filtration
efficiencies are obtained for TC and EC. Air flows, where relevant for
estimator analysis, were based on the sampler's comments, and/or the
accompanying mine ventilation plans or maps.
A number of commenters suggested that MSHA's DPM sampling results
in isolated sections of mines are assumed by MSHA to be representative
of on-going exposure levels in those mines, despite the fact that
results varied widely. In the 31-Mine Study, MSHA did not, in fact,
assume a sample result from an isolated section of a mine was
necessarily representative of on-going DPM exposure levels throughout
that mine. The study methodology stipulated that the highest observed
DPM level for a given mine would be the basis for specifying DPM
controls for the entire mine. A key underlying assumption of this
methodology is that DPM levels do vary, often significantly, from one
part of a mine to another. However, to insure that study findings would
be conservative, the study methodology required that the highest DPM
level, not the average or lowest DPM level, was the basis for
Some commenters asserted that when analyzing sampling data for the
31-Mine Study, MSHA assumed that ventilation flows measured at the
sampling location applied throughout the subject section of the mine.
They also asserted that MSHA assumed effective ventilation for dilution
existed throughout the mine, and that neither of these assumptions was
necessarily valid. For most of the mines in the 31-Mine Study for which
a DPM reduction was necessary, ventilation was not an issue, and
consequently, MSHA did not specify any changes in ventilation. For
these mines, DPM reductions were obtained by utilizing DPFs and/or
low-emission engines, and the only assumption regarding ventilation
was that it would not be changed.
In the few cases where ventilation upgrades were specified, the
upgrades were limited to auxiliary systems that supplied air to the
sampled area only. Initial air flows utilized by the Estimator for
those areas prior to implementing the upgrades were based on the
comments and/or any accompanying ventilation plans or maps accompanying
the sample. Where upgraded auxiliary ventilation was specified, MSHA
frequently noted deficiencies in existing auxiliary ventilation system
components such as inappropriately placed fans and blast-damaged or
otherwise deteriorated and compromised vent bags. In these cases, the
specified ventilation changes involved simply correcting the obvious
deficiencies in the existing systems and increasing fan capacity.
MSHA recognizes that there has to be a sufficient air quantity
present in the main ventilation system in order for an auxiliary system
to function properly (i.e. without recirculation), and that DPM levels
in the main ventilation system from which the auxiliary system draws
its air must be sufficiently below the DPM limit to prevent miners'
overexposures in the stopes.
Some commenters stated that in the 31-Mine Study, MSHA assumed that
the only equipment needing DPM controls was the equipment operating
while sampling took place. As noted above, the study methodology
insured a conservative result by applying the same controls required to
attain compliance for the equipment associated with the ``worst case''
sample to all similar DPM sources (and spares) in the entire mine, even
if the subject ``worst case'' sample concentration was substantially
higher than the remaining samples for that mine, and regardless of
whether a particular piece of equipment was operating during sampling
or not. For most mines in the study requiring DPM reductions, controls
were specified for all or most of the normal production contingent of
equipment, along with an allowance for spare equipment, particularly
loaders and trucks, which are typically the largest source of DPM.
Some commenters stated that in the 31-Mine Study, MSHA assumed 80%
DPF filtration efficiency, and gave no consideration to potential
NO2 problems related to DPFs. As noted above, the assumption
of 80% filtration efficiency is conservative, and is based on actual
laboratory and in-mine test data. Regarding NO2 generation
from DPFs and the associated health concerns, MSHA acknowledges that
NO2 can be produced by passive DPFs that are wash-coated
with platinum-based catalysts. However, when such filters are utilized
under reasonable ventilation conditions, the NO2 increases
should be manageable and should not constitute a serious health hazard
or compliance problem for the mine operator. An example of successfully
using highly platinum-catalyzed DPFs without creating hazardous
NO2 concentrations is Greens Creek mine which has installed
such filter systems on its large trucks and loaders. During MSHA
compliance assistance sampling at this mine in January 2002,
NO2 increases of around 1 ppm were observed downstream of
stopes where 1 loader and 2 or 3 trucks were operating for 2 to 3
MSHA also notes that in situations where passive DPF regeneration
is desired, but where ventilation may be insufficient to adequately
dilute and carry away harmful NO2 concentrations,
alternatives to highly platinum-catalyzed DPFs exist. Examples include
base metal catalyzed DPFs and lightly platinum-catalyzed filters used
in conjunction with a fuel-borne catalyst, which have a regeneration
temperature somewhat higher than highly platinum-catalyzed filters.
These passively regenerating DPFs do not increase NO2
concentrations compared to unfiltered exhaust emissions.
Even more importantly, however, in the 31-Mine Study, all DPFs were
specified as active type regeneration systems, not passive type
systems. Likewise, in the corresponding economic feasibility
assessment, all costs for DPFs included an assumption that mine
operators would opt for active regeneration. Without detailed on-site
analysis and evaluation of the subject equipment and duty cycles, MSHA
could not assume a DPF system would passively regenerate. Also, active
filter systems are typically more costly than an equivalent passive
system, so specifying an active system would be more conservative from
a costing perspective. Since actively regenerated DPFs have no platinum
wash-coatings applied to the filters (and in fact, have no wash-
coatings at all), they do not produce any increased NO2
emissions compared to unfiltered engines. NO2 emissions and
associated health concerns were not addressed in the 31-Mine Study
because the DPM controls specified in the study did not affect
Some commenters also stated that MSHA failed to specify any major
ventilation upgrades (new main fans, new ventilation shafts, etc.) in
the 31-Mine Study, and that by avoiding major ventilation upgrades, the
resulting compliance cost estimates were unrealistically low. In
responding, MSHA notes that it did not specify any major ventilation
upgrades in the 31-Mine Study because, based on the study methodology,
the analysis did not indicate the need for major ventilation upgrades
in order to attain compliance with either the interim or final DPM
limits at any of the 31 mines.
This does not mean that major ventilation upgrades would have been
ill-advised, ineffective, or unbeneficial for any of the mines in the
study. MSHA did note in the final report that strategies other than
those specified in the study could also be successful, and there may be
valid reasons why a mine operator might choose a different mix of
controls (such as a major ventilation upgrade) for a given mine based
on mine-specific factors to which MSHA's analysts were not privy at the
time of the study. It was explicitly stated in the final report that
the DPM controls specified for a particular mine did not necessarily
represent the only feasible control strategy, nor the optimal control
strategy for that mine. The purpose of specifying controls for each
mine was simply to demonstrate that feasible controls capable of
attaining compliance existed, and to provide a framework for costing
such controls on a mine-by-mine basis.
Indeed, since the completion of the 31-Mine Study, MSHA has
observed that mine operators in the stone industry, for example, have
chosen to attain compliance without utilizing DPFs. These operators
instead have opted to upgrade ventilation (usually by adding or re-
positioning booster fans and installing or repairing ventilation
control structures such as air curtains and brattices), install low-
emission engines, utilize equipment cabs with filtered breathing air,
initiate a variety of work practices that contribute to reducing
personal exposures to DPM, and in a few cases, use alternative diesel
fuels such as bio-diesel fuel blends and diesel/water emulsions.
Some of these mine operators may have had reasons other than DPM
compliance alone that helped justify their decisions. For example,
ventilation upgrades can also improve gaseous emission levels, dust
levels, visibility, clearance of blasting smoke and gases, and
inefficient or even counterproductive deployment of booster fans. Mine
operators that have opted to replace older, dirty engines with newer,
low emission engines benefit from greater fuel economy and better
maintenance diagnostics. Cabs with filtered breathing air improve
operator comfort and productivity, as well as reducing dust and noise exposures.
DPFs suitable for any duty cycle are currently commercially
available for most engine sizes and types used in underground M/NM
mining. DPF options include silicon carbide and cordierite ceramic
monolith type wall flow filters designed for passive regeneration,
active on-board or active off-board regeneration, or passive/active
regeneration. For most filters requiring active regeneration, the time
required for filter regeneration varies from less than 1 hour to 8
hours, depending on system type. Another option that is suitable for
smaller, light duty equipment is a high-temperature disposable pleated
Although every mine is unique, and virtually every DPF application
has unique features, the variety of DPF systems available make it
feasible to apply a DPF to most types of equipment or engines, and
application or duty cycle. The only exception known to MSHA would be
applying a DPF to a very old (pre-1970s vintage technology) engine
having very high DPM emissions and a medium or light duty cycle. In
theory, such an application would collect DPM, but due to rapid soot
build-up on the filter media and corresponding rapid increase in engine
back-pressure, such a DPF application would probably be impractical.
MSHA has observed very few such engines in the underground M/NM mining
industry, but in the few instances where emissions from such engines
need to be controlled, mine operators are advised to choose a control
option other than a DPF.
MSHA is aware of reports by mining companies and others that some
DPFs have not performed satisfactorily in the field. These reports
refer to problems such as short filter life (a matter of weeks in some
cases), equipment that bogs down when filters are installed, and
uncontrolled regenerations and similar problems resulting in damaged or
destroyed filters. MSHA has determined that most DPF failures result
from inappropriate filter selection due to the failure by mine
operators to fully consider all filter selection criteria prior to
ordering DPF systems. In a few cases, filter failures were traced to
manufacturing defects that were later resolved, while in a few others,
an unrelated component failure on the host equipment (such as a
turbocharger failure) caused a failure in the downstream DPF.
Most problems with filter selection relate to the installation of a
passively regenerating type filter on a machine that does not produce
sufficient exhaust temperature for a sufficient portion of the duty
cycle to initiate passive regeneration. A passive type filter that
doesn't regenerate continues to trap soot until the backpressure on the
engine causes the engine to ``bog down,'' or an uncontrolled
regeneration occurs. The system may function satisfactorily for a
while, either regenerating as expected, or at least partially
regenerating. But if the machine's duty cycle lessens in severity, even
for a single shift (for example, a production loader that is normally
worked very hard might be used for a shift to perform road maintenance
or clean-up duty), the filter may become overloaded.
MSHA's determination that DPFs are a technologically feasible DPM
control option is based on two factors: Laboratory and in-mine testing
which has documented their high filtration efficiency, and numerous
successful applications in routine production mining situations where
DPFs have been appropriately matched to machines and duty cycles. When
DPFs are properly selected and maintained for an application, the
result is optimal performance and maximum filter life.
In order to achieve satisfactory filter performance, filter life,
and filtration efficiency, it is critical that a DPF be appropriately
matched both to the diesel engine, and to the duty cycle and intended
application of the subject equipment. For example, two identical
machines may need different types of filter systems based on the
machines' respective duty cycles. One machine that works hard due to
the road grades that the machine must transverse during a shift may
generate sufficient exhaust gas temperatures to support a passive
regeneration DPF system. However, the second machine may run
continuously on flat roads in the mine and, therefore, may not be
capable of generating sufficient exhaust gas temperatures to support
passive regeneration. Consequently, the second machine must use an
active regenerating DPF system, or change out a disposable filter on a
regular basis. Importantly, if the first machine, due for example to a
breakdown of the second machine, assumes the second machine's duties,
even on a temporary basis, it would be very possible if not likely,
that its passive DPF system would fail to regenerate. Hence, when
specifying a DPF system for a particular piece of equipment, mine
operators should consider not only the intended application and duty
cycle of the machine, but also other applications and duty cycles to
which that machine may be occasionally assigned on a nonroutine basis.
In order to assist the mining industry in selecting an appropriate
filter, the MSHA and NIOSH internet web sites include a comprehensive
compliance assistance tool, the Filter Selection Guide. One of many
MSHA DPM compliance assistance tools, the Filter Selection Guide
provides mine operators with detailed step-by-step assistance in
selecting appropriate DPF systems that are compatible with their
specific equipment and duty cycles. Also, the Filter Selection Guide
provides information on modifications and adjustments to diesel-powered
equipment that mine operators may have to make to successfully apply
Prior to initiating the DPF selection process, mine operators
should make certain that they are properly maintaining their engines,
and that the engines are not consuming excessive amounts of crankcase
oil. Operators should then obtain exhaust temperature logs or traces
for several shifts, and use these traces to help select the appropriate
DPF system for that machine and application. Exhaust temperature traces
can be analyzed by mine personnel or DPF suppliers to assist in
selecting a workable DPF system. Exhaust gas temperatures are an
important factor in selecting a DPF because passive filter regeneration
is possible only if sufficient exhaust gas temperatures are attained
for specified minimum time periods throughout the engine's duty cycle.
The exhaust temperatures that must be attained, and the corresponding
DPFs, are listed in Table VII-1.
Table VII-1.--Ceramic Wall-Flow Monolith DPF Regeneration Options
exhaust must exceed
DPF regeneration type at least 30% of the DPF media Comments
time for passive
regeneration to occur
Passive........................... >550[deg]C........... Uncatalyzed media; can be Exhaust temperatures
either cordierite or >550[deg]C rarely if
silicon carbide. ever occur; thus,
passive regeneration of
uncatalyzed DPFs is not
a practical option.
>390[deg]C........... Base metal catalyzed No increase in NO2.
>340[deg]C........... Lightly platinum-catalyzed Special provisions must
cordierite or silicon be made to ensure
carbide with fuel additive is always
additive. present in fuel and that
equipment w/o DPFs
cannot be fueled with
fuel. No increase in
>325[deg]C........... Platinum-catalyzed Lab results indicate
cordierite or silicon significant NO to NO2
carbide. conversion; field
results are mixed;
depends on consistently
exhaust temperatures and
adequate ventilation to
dilute and carry away
Active............................ Not applicable....... Uncatalyzed cordierite or DPFs manually regenerated
silicon carbide. on-board or off-board
depending on system
Not applicable....... Uncatalyzed silicon Active/passive\1\ type
carbide or cordierite. system uses fuel burner
to assist regeneration
at any exhaust gas
temperature and duty
based on exhaust
\1\ MSHA is aware of another type of active/passive system utilizing an on-board electrical heating source to
assist regeneration of sintered metal filter media, but is not aware of any underground mining applications of
this system at this time.
As Table VII-1 indicates, passive DPF systems will regenerate
successfully at or above the exhaust gas temperature specified by the
manufacturer. However, these exhaust gas temperatures must be
maintained for at least 30% of the shift to be sufficient for passive
regeneration. An active regenerating system will work at any exhaust
The tune of the engine will also be a factor for proper
regeneration. If an engine goes out of tune and begins to emit higher
DPM concentrations in the exhaust, the exhaust backpressure may
increase too quickly. Therefore, MSHA and DPF manufacturers recommend
that mine operators install backpressure monitoring devices on machines
equipped with DPFs in order to properly monitor the condition and
regeneration state of the filter.
In the DPM settlement agreement, MSHA agreed to a compliance
assistance period of one year beginning July 20, 2002 and ending July
19, 2003. Among its many compliance assistance activities during this
period, MSHA examined the mine worthiness of available DPF systems. In
the preamble discussion to the 2003 NPRM, MSHA stated:
MSHA has found that most mine operators can successfully resolve
their implementation issues if they make informed decisions
regarding filter selection, retrofitting, engine and equipment
deployment, operations, and maintenance. The Agency recognizes that
practical mine-worthy DPF systems for retrofitting most existing
diesel powered equipment in underground metal and nonmetal mines are
commercially available and are mine worthy to effectively reduce
miners' exposures to DPM. MSHA also recognizes that installation of
DPF systems will require mine operators to work through technical
and operational situations unique to their specific mining
circumstances. In view of that, MSHA has provided comprehensive
compliance assistance to the underground metal and nonmetal mining
NIOSH also stated its position on the DPF systems currently
available for most mining equipment during this period. By letter of
June 25, 2003, to MSHA, NIOSH stated:
With regard to the availability of filters and the interim standard,
the experience to date has shown that while diesel particulate
filter (DPF) systems for retrofitting most existing diesel-powered
equipment in underground metal and nonmetal mines are commercially
available, the successful application of these systems is predicated
on solving technical and operational issues associated with the
circumstances unique to each mine. Operators will need to make
informed decisions regarding filter selection, retrofitting, engine
and equipment deployment, operation, and maintenance, and
specifically work through issues such as in-use efficiencies,
secondary emissions, engine backpressure, DPF regeneration, DPF
reliability and durability. NIOSH is of the opinion that these
issues can be solved if the informed decisions mentioned above are
made. This view is supported by comments made by mine operators at
the NIOSH-sponsored workshops entitled ``Diesel Emissions and
Control Technologies in Underground Metal and Nonmetal Mines.''
Analysis of the recently completed Stillwater Mine experiments and
related in-mine tests will also provide information regarding in-
mine filter efficiency performance of these systems as compared to
their performance in the laboratory.
Assuming that the results show comparable filter efficiency
performance, metal/nonmetal mine operators in similar circumstances
will be able to use the information with confidence to predict
performance results in reducing DPM levels in particular
MSHA believes that this document confirms that DPF systems are
available and mine-worthy to reduce miners' exposures to DPM.
Some commenters stated that the intermittent duty cycles (bursts of
heavy work, followed by idle time) common for large front-end loaders
used in the stone mining industry are unlikely to produce sufficiently
high exhaust temperatures for passive regenerating DPFs to be a
feasible DPM control option. MSHA notes that during its 2003 compliance
assistance visits, exhaust temperature monitoring conducted on a
production loader indicated sufficient temperatures for a sufficient
portion of the duty cycle to permit that loader to utilize a passively
regenerating DPF system. Clearly, such limited testing was not
definitive, and the mine operator would need to conduct additional
temperature monitoring to verify these results over the complete range of work activities
performed by this loader. However, there was nothing particularly
unusual about this loader or its duty cycle, so the commenter's
suggestion that loaders in the stone industry, in general, cannot
utilize passive regenerating DPFs, is inaccurate.
Also, MSHA notes that there are feasible alternatives to passive
regeneration for filtering the exhaust of any size engine used in the
stone mining industry. Mine operators could choose on-board or off-
board active regeneration, including an on-board fuel burner type
system that actively regenerates the filter during normal production
operations without any intervention by the equipment operator, without
shutting down the equipment, and without any increase in NO2
Industry commenters related the experiences of four mining
companies to support the position that DPF systems are not a
technologically feasible DPM control option for attaining compliance
with the interim DPM limit in underground mining applications. The four
companies were the Stillwater Mining Company (Stillwater mine in
Montana), Newmont Gold (Carlin East and Deep Post mines in Nevada),
Kennecott Minerals (Greens Creek mine in Alaska), and Cargill Salt
(Avery Island mine in Louisiana).
Commenters reported that platinum wash-coated passive DPFs have
proven successful at the Stillwater mine. They indicated that the
equipment best suited to utilizing passive systems includes 19 primary
haulage trucks, eight locomotives, and two large LHDs which together,
are estimated to account for about 35% of the mine's DPM emissions.
This equipment tends to work in haulageways where there is frequently a
good ventilation air flow. However, as noted elsewhere in this section
of this preamble, the commenters noted problems with high
NO2 emissions from equipment fitted with platinum wash-
coated passive DPFs. MSHA has determined that the NO2
problems at this mine result from inadequate ventilation, and that high
NO2 levels at this mine pre-dated the use of platinum wash-
coated passive DPFs.
These commenters indicated that the remaining 321 machines at this
mine do not have high enough duty cycles and exhaust temperatures to
utilize passive DPFs, and that active DPF systems are not considered
feasible by the mine operator. As discussed in detail below in this
section, MSHA believes that the mine operator's determination of
infeasibility of active filters is based on a proposed active
filtration concept that is not optimal for this mine.
These same commenters also discussed the technological and economic
feasibility analyses for the Stillwater mine included in the 31-Mine
Study. MSHA has acknowledged that the cost estimates contained in the
31-Mine Study final report significantly underestimate the probable DPM
compliance costs for this mine. At the time the 31-Mine Study was
conducted, MSHA's analysts had been supplied with inaccurate
information regarding this mine's diesel equipment inventory. MSHA
subsequently revised its analysis based on updated equipment inventory
data. The revised estimate of compliance cost for the Stillwater mine
is considerably higher than the estimate included in the 31-Mine Study.
However, as discussed later in this section, it is nonetheless
consistent with the estimated compliance cost for a precious metals
mine of this size as detailed in MSHA's REA for the 2001 final rule.
The commenters indicated that Newmont has experimented with both
passive and active DPFs in the Carlin East and Deep Post mines, and
that a problem exists. The commenters state that engine backpressures
range from 37 to 43 inches of mercury when DPFs are in use, and one of
their engine suppliers, Caterpillar, will not warrant engines when
backpressure exceeds 27 inches of mercury. In response, MSHA references
the NIOSH/MSHA Filter Selection Guide, which states that DPF systems
must be sized so that backpressure is within the engine manufacturer's
The commenters go on to relate Newmont's successes with DPFs,
including both platinum wash-coated passive filters on haulage trucks
and base metal wash-coated passive/active filters on smaller LHDs and
jammers. Although elevated NO2 emissions can be associated
with platinum wash-coated DPFs, the trucks equipped with these filters
are used to haul ore up well ventilated ramps to the surface, so the
potential for NO2 overexposure is minimized. The smaller
LHDs and jammers are typically used in production areas with lower
ventilation rates, so base metal wash-coated filters are used which do
not generate NO2. Because of the limited duty cycle of these
smaller machines, total filter regeneration may not occur. However, the
wash-coat promotes enough regeneration that the filters are able to
function properly between set service intervals that coincide with the
equipment's preventive maintenance schedule, at which time the filters
are changed-out, and the ``dirty'' filters actively regenerated off-
The commenters also related Newmont's experience with ``failed''
DPFs, including a filter that was destroyed due to excess vibration and
another that was destroyed when an upstream turbocharger failed and
blew oil into the DPF. However, the commenter went on to describe the
steps taken by Newmont to successfully correct the vibration problem
(shock absorbing filter mounts), and the other destroyed DPF was
clearly caused by the failed turbocharger, not an integral failure of
the DPF. MSHA has repeatedly advised the mining community that a
certain amount of applications engineering will be required to insure
the successful deployment of DPFs on underground mining equipment. The
vibration failure example illustrates that as mine operators obtain
experience with DPFs, problems will inevitably be encountered, but they
can be readily solved by applying reasonably simple hardware solutions.
These commenters also questioned MSHA's assumptions regarding the
feasibility of auxiliary ventilation system upgrades discussed in the
31-Mine Study, however, the upgrades specified for Carlin East in the
31-Mine Study related to achieving the final DPM limit. Compliance with
the interim limit was projected without ventilation upgrades.
These commenters concluded that overall DPM compliance costs are
too high for Newmont Gold. Newmont estimates that the, ``purchase and
installation of DPFs, including downtime on production vehicles, will
be $1.9 million for its two mines--Deep Post and Carlin East.'' No
further cost breakdown is provided, so MSHA could not assess the
reasonableness of this estimate. However, accepting this estimate as
submitted, and assuming a two-year DPF service life, Newmont's estimate
of its DPF costs implies a yearly cost of $1.05 million for the two
mines ($1.9 million annualized over two years at a 7% discount rate).
MSHA notes in the REA for the 2001 final DPM rule that its estimated
compliance cost for a medium-sized gold mine employing 20 to 500 miners
is $171,900 per year based on a diesel equipment fleet size of 24
pieces of diesel equipment. This estimate was based on analysis
indicating about 78% of overall compliance costs would relate to DPFs.
Adjusting MSHA's estimated annual cost to correspond to the combined
166 pieces of equipment at Newmont's two mines yields an estimated
annual DPF-related compliance cost of about $927,000, which is only 12%
less than Newmont's estimate of its annual DPF-related compliance cost.
The same commenters described DPF installations on haulage trucks
and loaders equipped with Detroit Diesel Series 60 engines rated at 450
horsepower and 350 horsepower, respectively, at the Kennecott Greens
Creek mine in Alaska. Regarding the trucks, the same commenters
reported that, ``After initial problems, mainly caused by incorrect
installation and sizing of filters, the mine has successfully equipped
its fleet of six Toro trucks with DPFs.'' This experience confirms two
important aspects of DPF utilization that MSHA has emphasized
repeatedly in its compliance assistance communications with the
industry, including (1) the likely need for a certain amount of
applications engineering to resolve implementation and installation
issues, and (2) the need to appropriately match the DPF to the machine
and duty cycle.
With respect to installations on two identical Toro 1250 loaders,
it was noted that the platinum wash-coated DPF on one unit consistently
passively regenerated, while the DPF on the other unit, which had a
lesser duty cycle and exhaust temperatures that were 40 to 50[deg]C
lower, did not. This experience does not illustrate the failure of DPF
technology. Rather, it confirms MSHA's consistent advice that the
successful deployment of passively regenerating DPFs requires careful
determination of exhaust temperatures to assess whether passive
regeneration is feasible for that particular machine and in that
application. Indeed, in this example, the filter functioned precisely
as designed. The failure of the filter to passively regenerate on the
second machine could have been reliably predicted based on the exhaust
In their comments, industry also relates Greens Creek's successful
application of an active DPF system on an Elphinstone R1300 3\1/2\-yd
LHD with a Cat engine. This loader is used for relatively light duty
clean up work, and is therefore not a suitable candidate for
application of a passively regenerating DPF.
It should be noted that industry also commented that, ``Those
engines in the 250-350 horsepower, and greater-than 350 horsepower
ranges are considered unsuitable for DPFs with present technology. This
general conclusion of unsuitability for DPF usage for these large
engines comes from use of DPFs in real mine situations.'' These
statements are directly contradicted by Greens Creek's successful
experience filtering the exhaust from 350 horsepower and 475 horsepower
Industry also presented the experience of Cargill Salt's Avery
Island mine in Louisiana which installed two DCL Mine X DPF filters on
a Cat 992G loader equipped with a Cat 3412 engine rated at 650
horsepower. One 15 inch diameter by 15 inch long filter was connected
to each bank of the V-12 engine. This model DPF is wash-coated with a
platinum catalyst to facilitate passive regeneration. The mine reported
that there are no problems with elevated NO2 levels, and
visible emissions have been reduced. However, the mine also reported
that the loader has lost almost all of its power, to such an extent
that the loader is only used for clean-up duty.
These symptoms--no elevated NO2 levels, visible
emissions reduced, and loss of power--are all typical of a mismatch
between the duty cycle of the application and the performance
specifications of the DPF. In order to passively regenerate, this DPF
requires exhaust temperatures of about 325[deg]C or higher for at least
30% of its duty cycle. An insufficiently demanding duty cycle produces
lower exhaust temperatures which are not sufficient to ignite and burn
off accumulated DPM. Such a filter continues to collect DPM, resulting
in lower visible emissions, but as the filter loads, even for a single
work shift, backpressure on the engine increases, resulting in loss of
power. Although these commenters report that mine mechanics worked
closely with the local Caterpillar dealer in installing the system, it
is very likely that this experience illustrates an inappropriate DPF
application rather than a failed filter system.
Normally, the local Caterpillar dealers and any other engine
manufacturer's dealers work more with issues concerning the engine
installation and repairs than with DPM filter applications. Since
engine manufacturers at this time do not install a DPF to the engine at
the time of engine production, the local engine dealers are not usually
familiar with DPF systems that are installed as retrofits on the
However, even in the case of the Greens Creek experience, where the
mine operator worked with the engine manufacturer, the vehicle
manufacturer, and the filter manufacturer at the onset to incorporate a
DPF on a new machine, the mine still initially had a failure of the DPF
because of regeneration issues. As Greens Creek reported,
the unit (DPF) was used on a waste rock backhaul route, with loads
being carried down the ramp or on relatively flat hauls. Had the
unit been used for ore haulage uphill routes, it would have achieved
the high exhaust temperatures for the designed passive regeneration.
This mine's experience continues to emphasize that the mine must
understand the duty cycle of the machine to which the DPF is being
equipped to see if the duty cycle can support the regeneration needed
for the DPF. In the case of Greens Creek, the waste rock backhaul
vehicle did not have a sufficiently demanding duty cycle to generate
the exhaust gas temperature needed for regeneration for a passive
regeneration system. In such instances, the mine operator needs to go
to another method of regeneration for the vehicle's DPF as discussed
elsewhere in this preamble. Mine operators should also refer to the M/
NM Filter Selection Guide on MSHA's Web site for assistance in choosing
the appropriate DPF system for its particular circumstances.
Industry also discussed various issues relating to compliance
problems for stone mines, such as feasibility of filters for large
engines, biodiesel fuel, and ventilation. These issues are addressed
elsewhere in this preamble in sections that deal specifically with
these topics. Some commenters stated that MSHA presumed that operators
would retrofit DPFs on existing diesel-powered equipment as the primary
method of compliance. These commenters questioned whether
implementation issues with retrofitting and regeneration would make
DPFs infeasible. In response, MSHA has determined on the basis of in-
mine tests conducted by NIOSH, MSHA, individual mining companies and
others, and on the experiences of mining companies that have
implemented DPM filtration on a routine production basis, that DPFs are
a practical, mine-worthy, and effective means for reducing exposure to
DPM in underground M/NM mines. Further, MSHA has determined that use of
DPFs independently or in conjunction with other feasible and effective
DPM engineering and administrative controls will enable most mine
operators to attain compliance with the DPM interim limit. However,
MSHA agrees with the commenters that implementation issues with
retrofitting and regeneration may present compliance difficulties for
some mines, and additional time may be required at some mines due to
the cost of purchasing and installing controls.
Many commenters have cited problems with DPFs which they believe
support the contention that DPFs are neither technologically nor
economically feasible. As noted above, some commenters provided examples
from several underground mines that experienced failed DPFs. Commenters
indicated that a ceramic filter, using passive type regeneration would be the
only type filter that would be acceptable to them. Commenters also stated
that ceramic DPFs that require active regeneration, a fuel borne catalyst, a catalyst
that could have the potential to increase NO2 emissions, and
any kind of filter for engines less than 50 horsepower or greater than
250 horsepower were infeasible for use in underground M/NM mines. Some
commenters described installations that produced high exhaust
backpressure on engines that could lead to voiding engine warranties or
render a vehicle unusable. A commenter also stated that the number of
regeneration stations that would be required to be built and maintained
would make active regeneration infeasible.
Other commenters stated that when DPFs are appropriately sized and
fitted to equipment, and there is a good match between the equipment
application/duty cycle and the DPF regeneration method, long filter
life and significant DPM reductions will result. Several commenters
indicated that, after an initial trial-and-error ``learning period,''
they had experienced success with passive type DPFs and were using them
on a routine production basis.
Some commenters stated that DPFs continue to be a feasible
technology for significantly reducing DPM exposures. One commenter
reported the successful application of an on-board active regeneration
DPF. This system includes an exhaust backpressure monitor that warns
the equipment operator when DPF regeneration is required. This is a
feature MSHA recommends for all DPF installations.
As noted above, MSHA acknowledges the numerous documented examples
of failed DPF applications in the underground M/NM mining industry.
However, MSHA believes such failures are the result of inappropriate
filter selection, manufacturing defects, and unrelated failures of
equipment components (such as turbochargers) that have caused damage to
DPFs. MSHA is confident that proper filter selection will result in
satisfactory long term DPF performance, and NIOSH agrees with MSHA that
DPFs are technologically feasible for most mining equipment after some
technical and operational problems are solved, and that these problems
can be solved in most cases.
To help mine operators avoid having to rely on costly and time
consuming trial-and-error methods for DPF selection, the Filter
Selection Guide was developed. It is the result of a joint effort of
MSHA and the Diesel Team from the NIOSH Pittsburgh Research Laboratory.
The Filter Guide provides mine operators with information on feasible
and available DPFs. NIOSH will work with MSHA to maintain the Filter
Guide on the internet.
MSHA continues to urge mine operators to thoroughly evaluate each
application to insure that the appropriate DPF and regeneration system
is chosen. Such an evaluation is well within the technical capabilities
of most mine operators to perform. For the few operators that would be
unable to independently perform this evaluation, technical assistance
can be obtained from mining equipment manufacturers, engine
manufacturers, DPF manufacturers, and MSHA.
As noted earlier, selection of an appropriate DPF for a given
application requires consideration of such factors as engine type,
model, and horsepower, as well as the intended usage of the equipment
and related equipment duty cycles. Mine operators are fully capable of
obtaining this information for every piece of equipment that is a
candidate for DPF installation. In addition, the engine's DPM emission
rate and exhaust temperatures must be obtained. For MSHA-approved
engines, DPM emission rates are determined by MSHA and included with
the engine approval. For non-approved engines, DPM emission information
can be obtained from the engine manufacturer or estimated based on the
characteristics of the engine (direct injection, pre-chamber, make and
model, model year, naturally aspirated, turbocharged, electronically
controlled, etc.). To obtain exhaust temperatures, various inexpensive
(approximately $200) data logging thermocouple systems are commercially
available that can be attached to the exhaust system to provide
detailed exhaust temperature profiles over time periods ranging from
several hours to several shifts. During its compliance assistance mine
visits in the spring and summer of 2003, MSHA noted that several mine
operators had acquired exhaust temperature data logging systems and
were using them to systematically measure exhaust temperatures on
equipment that might need to be equipped with a DPF in the future.
DPFs collect significant amounts of DPM from the engine's exhaust,
thus lowering DPM exposures. This fact was not disputed by the
commenters. The results from MSHA's compliance assistance work with
Kennecott at their Greens Creek Mine, NIOSH's isolated zone tests
conducted at the Stillwater Mine, NIOSH's production zone tests at the
Stillwater mine, MSHA's laboratory data, laboratory and in-mine test
results from Canadian and European studies, and various other industry
applications prove that DPFs provide high efficiency reductions in both
DPM and EC. For EC, the data indicate filtration efficiencies as high
as 90% to 99+%.
MSHA disputes commenters' views that if passive regeneration cannot
be successfully employed (due, for example, to an insufficient duty
cycle and correspondingly low engine exhaust temperatures), then DPM
filter technology is infeasible. Passive regeneration is only one of
many regeneration schemes available to the mine operator. Clearly, not
all machines or all applications are suitable for passive regeneration.
One commenter stated that one of his firm's two loaders was able to use
a passive regeneration DPF due to the exhaust gas temperatures reached
during its duty cycle, while the other could not or was marginal. This
experience demonstrates precisely what MSHA's consistent message to the
industry has been--that successful application of passive regeneration
DPFs depends on matching the filter to the application, and mine-worthy
systems are commercially available for most any machine and any duty
It is important to note that a sufficiently heavy duty cycle does
not, by itself, guarantee that a passive regeneration DPF will function
properly and provide satisfactory long-term performance. It is an
essential prerequisite, but the other steps in the DPF selection
process must also be followed rigorously. Without the necessary exhaust
temperatures for the specified amount of time, passive regeneration is
impossible, regardless of how carefully the other steps in the
selection process are followed. However, once the necessary exhaust
temperature profile has been verified through sufficient in-mine
temperature monitoring, users are urged to carefully complete the
remaining steps in the selection process.
For whatever reason, if a particular machine requires a DPF, but is
an unsuitable candidate for application of a passive regeneration
system, the mine operator has the option of using a combination
passive/active regeneration scheme or to use a purely active
regeneration system. Because the option exists for utilizing either
passive, active/passive, or active regeneration systems, MSHA maintains
that a suitable DPF system is available for any size diesel engine and
any application in the underground M/NM mining industry. The mine
operator may need to address various implementation issues regarding
retrofitting and regeneration, but MSHA is confident these issues can be resolved.
NIOSH's Phase I Isozone and Phase II Production Zone Studies
Related to DPFs at the Stillwater Mine. NIOSH conducted a series of in-
mine tests on DPF systems at the Stillwater Mining Company's
underground platinum mine at Nye, MT. The tests were conducted in two
phases. The Phase I tests were conducted from May 19-30, 2003, and the
Phase II tests were conducted from September 8-12, 2003. The purpose of
Phase I was to assess the effectiveness of DPM control technologies in
an isolated zone. The purpose of Phase II was to assess the capability
of DPFs to effectively control the exposure of underground miners to
DPM in actual in-mine production mining scenarios.
NIOSH issued two final reports on these studies. The final report
for Phase I was entitled ``Effectiveness of Selected Technologies in
Controlling Diesel Emissions in an Underground Mine--Isolated Zone
Study At Stillwater Mining Company's Nye Mine,'' and the report was
released on January 5, 2004. NIOSH included the following in its
discussion of the objective of the study:
The objective of this study was to determine the in-situ
effectiveness of the selected technologies available to the
underground mining industry for reducing particulate matter and
gaseous emissions from diesel-powered equipment. The protocol was
established to determine the effectiveness of those technologies in
an underground environment under operating conditions that closely
resemble actual production scenarios.
The study was designed to provide Stillwater, and the general
mining community, with better insights into the performance of
control technologies and enable them to identify the appropriate
devices for reducing diesel emissions. The focus of the Stillwater
research was on technologies that offer solutions for reducing DPM
emissions. This report provides the results and assessment of the
following control technologies: diesel particulate DPFs, disposable
paper DPFs, diesel oxidation catalytic converter, and reformulated
The Phase II final report was entitled, ``An Evaluation of the
Effects of Diesel Particulate Filter Systems on Air Quality and
Personal Exposures of Miners at Stillwater Mine Case Study: Production
Zone,'' and the report was released April 1, 2004. The objective of
Phase II was to determine the effects of DPF systems installed on
production equipment at the Stillwater Mine on workplace concentrations
of EC and regulated gases in an actual production mining application
where multiple diesel-powered vehicles operated simultaneously during
full shift mining activities. The effects of DPF systems were examined
by comparing ambient concentrations of EC, CO, CO2, NO, and
NO2 in a production area for two different test conditions.
For the baseline condition, all vehicles that operated within the
ventilation split were equipped with standard exhaust systems--a diesel
oxidation catalyst (DOC) and muffler--but without DPFs. For the second
condition, three of the vehicles, an LHD and two haulage trucks had
their DOC and muffler systems replaced with DPF systems.
The NIOSH Phase II study conducted at the Stillwater Mine is
similar to the in-mine tests conducted by MSHA in January 2003 as a
part of its compliance assistance program at the Kennecott Greens Creek
Mine near Juneau, AK, which is discussed elsewhere in this preamble.
NIOSH Phase I study. The majority of the control devices tested
were DPFs. Phase I also tested biodiesel fuel and the differences
between 1 diesel fuel (D1) and 2 diesel fuel (D2).
DPFs included both ceramic and high temperature disposable (synthetic
media) filters. NIOSH reported that some problems did occur during the
tests, mainly dealing with ventilation issues in the isolated zone and
an occasional vehicle passing nearby the intake to the isolated zone.
However, these problems were minor and did not compromise most tests.
As reported, NIOSH chose to normalize the data based on MSHA's
nameplate gaseous ventilation rates. One commenter stated that he
understood why NIOSH normalized the Phase I data to the MSHA nameplate,
however, the commenter felt this was a disservice to the miners since
M/NM mines do not have to comply with the ventilation rates on the
approval plates. Indeed, engines in M/NM mines are not required to be
MSHA approved and ventilation rates are not available for non-MSHA
approved engines. MSHA agrees with the commenter that the Phase I
report had the correct intent to normalize the data for reporting
purposes. MSHA also agrees that the results may not be typical for
operations in the M/NM sector because the ventilation schemes used by
many M/NM mines do not comply with approval plate quantities for MSHA
The Phase I report shows that the EC reduction in the isolated zone
with one system was 88%, and that two other systems gave greater than
96% EC reductions when the measured concentrations were normalized by
ventilation rate. NIOSH reported that several tests were discarded and
not reported due to unexplainably low CO2 concentrations
found at low ventilation rates.
The filter media used in all the DPF systems during the Phase I
test was either Cordierite, Silicon Carbide, or the disposable high
temperature synthetic material. (An analysis conducted by an MSHA
contracted laboratory indicated the synthetic material is fiberglass.)
All the DPF media have very similar efficiencies for EC reductions.
Even though NIOSH did not report the EC reduction efficiencies of all
the DPF systems tested in Phase I, MSHA believes, based on its own
evaluations, that the efficiencies for EC reductions of those DPFs not
reported would have been approximately equal to the results obtained
for DPF systems that were reported.
Many commenters agreed that the Phase I study accomplished its
objective by showing that DPM filters are viable for reducing DPM from
diesel engines and that the filter systems performed as designed.
However, some of these commenters stated that the elaborate test setup
in the Phase I study was only a replication of a laboratory type
environment that did not represent actual mine conditions. Commenters
pointed out that some of the control technologies did not perform as
well as expected during the study.
MSHA agrees that the Phase I study demonstrated that DPM filters
are an effective tool for reducing DPM emitted from diesel engines. The
Phase I study did involve an elaborate test setup, but this test setup
was primarily aimed at controlling the ventilation conditions so that
extraneous DPM from upstream diesel traffic would be eliminated,
thereby enabling a meaningful and accurate determination of the DPM
reductions obtained by the various DPFs tested. In other respects,
however, the test setup was quite realistic, in that the testing
occurred underground and involved a realistic simulation of a
production mining operation. For example, in testing of LHDs, the test
protocol required a production LHD to repeatedly follow a proscribed
duty cycle involving loading at a muckpile, tramming up a 9% grade
along the main haulageway a distance of approximately 1,000 feet with a
loaded bucket, various forward and reverse maneuvers over short travel
distances at each end of the haulageway, and raising and lowering a
loaded bucket to simulate loading a haulage truck. Other than the
removal of existing exhaust system components (DOC and muffler) to
accommodate installing the subject DPFs, and the installation of
certain monitoring instrumentation, the equipment used in the study
was unmodified and in ``as is'' condition from the mine's equipment inventory.
Although this testing was based on simulated mining operations, the suggestion
that it replicates a laboratory environment is an inaccurate characterization.
MSHA believes that the Phase I Isozone data is sound science,
establishing with certainty that DPFs can be implemented on a broad
scale in mines in the U.S. and that DPFs are capable of achieving
significant reductions in miner's DPM exposures. MSHA notes that these
data are consistent with the results of other similar tests, including
both laboratory tests conducted by MSHA, NIOSH and others, and a
Canadian in-mine isolated zone test in which NIOSH also participated.
MSHA discussed the results of this Canadian test in the preamble to the
2001 final rule.
One commenter stated that the Phase I isolated zone test should
have been completed long before the DPM rule was rushed to publication.
MSHA does not agree with the commenter. In fact, MSHA used the results
of the above mentioned Canadian isolated zone study in its original
2001 DPM rule to show the effectiveness of DPFs. The recent NIOSH
isolated zone testing confirmed the results obtained by the Canadians.
As noted above, the pertinent data that were derived from the Canadian
study on the efficiencies of DPFs were referenced in the preamble to
the 2001 final rule.
At the end of the Phase I report, NIOSH indicated that the
Stillwater mine had at that time over one dozen DPFs in use for a
combined total of over 22,000 operating hours. NIOSH reported that only
one of these DPFs had failed (runaway regeneration), and that the other
systems have been virtually maintenance free. Again, even though
Stillwater's experiences with DPFs on a routine production mining basis
have been with heavily platinum-catalyzed passive systems, the
commercially available DPF media are the same for passive systems using
other catalyst wash coats as well as for active regeneration systems
that utilize uncatalyzed filter media. Moreover, all DPF media
basically provide equivalent filtration efficiencies for DPM, TC, and
NIOSH Phase II study. The Phase II study confirmed and expanded on
the results obtained in the Phase I study. In the final report, NIOSH
indicated that greater EC reductions were observed in the field than
were obtained in the laboratory for whole diesel particulate:
* * * laboratory determination of DPF efficiencies, based on
reductions in total DPM mass (fairly equivalent to TPM [Total
Particulate Matter]), substantially underestimates the ability of
DPF systems to reduce EC emissions, the metric used by MSHA for
compliance,* * *
which highlights the high EC filtration efficiency for DPFs.
MSHA believes that the Phase II study helped to confirm existing
agency data that shows that it is technologically feasible to reduce
miners' exposures to DPM to the 308EC [mu]g/m\3\ interim
PEL. The Phase II study utilized three machines (1 LHD and 2 Haul
Trucks) equipped for the first three days with highly platinum-
catalyzed Englehard DPX[supreg] DPFs, and the last day without the
DPFs, but with DOCs. The equipment engaged in normal production
activities in a typical production mining area of the Stillwater mine,
as opposed to the simulated mining tasks that were conducted in an
isolated zone in the Phase I study. Personal sampling on equipment
operators was conducted, as well as area sampling upstream and
downstream from the working area where the equipment was operating.
Tests were conducted with and without DPFs installed so that the
capability of the DPFs to reduce personal DPM exposures and DPM levels
in the ambient mine air could be quantified.
The results of the personal EC samples from the three machine
operators equipped with filters were provided in the final report.
NIOSH did not report Day 1 results due to inadequate sampling
locations. The EC results for personal samples for Day 3 showed that
the DPM exposures of all three miners were well below 308EC
[mu]g/m\3\, and in fact, well below 160EC [mu]g/m\3\. Day 2 showed
exposures also below 308EC [mu]g/m\3\, but almost double the
results of Day 3. However, it appears that the ventilation air flow
through the working area on Day 2 was about half the ventilation air
flow for Day 3. Thus, the differences in measured DPM levels are not
contradictory, but rather, demonstrate the effectiveness of increased
ventilation flow as an engineering control to reduce DPM levels in the
ambient air. The EC reduction efficiencies of the DPFs based on
personal exposures comparing test days with and without the filters in
place were approximately 71% for the LHD operator and 78% for the haul
truck drivers. These reductions are very similar to the results
obtained for personal exposures in the Greens Creek study conducted by
MSHA in January 2003.
NIOSH reported that some of the filters used during the Phase II
testing at Stillwater may have been compromised. However, NIOSH
indicated in the Phase II final report that, ``* * * even when the DPF
systems are performing below expectations, they can significantly
reduce the EC concentrations when compared to conditions when DPF
systems were not used.'' Significantly, MSHA made a very similar
observation in its report on Greens Creek. During testing at Greens
Creek, there were obvious visible cracks in some of the ceramic media.
But analysis of DPM concentrations in the equipment exhaust indicated
that EC filtration efficiency was still quite high (>90%) despite the
cracks. Clearly, even compromised DPM filters can reduce personal DPM
exposures to levels below the interim PEL.
NIOSH reported increased NO2 concentrations during the
study when using DPFs, and suggested that the source of the increase
was the platinum catalyst used as a wash coat for the Cordierite filter
media. The platinum wash coat on the filter is used for regeneration
purposes and does not affect filter efficiency for EC measurements.
Therefore, the reduction observed in EC concentrations from the Phase
II study should be expected when any filter is installed that has a
Cordierite filter media. As discussed elsewhere in this preamble, a
Silicon Carbide filter media is also used in many DPF systems and EC
filtering efficiency for Silicon Carbide is very similar to Cordierite.
As noted above, NIOSH reported increases in NO2
concentrations when highly platinum-catalyzed DPFs were used. NIOSH
stated in the Phase I final report that ``* * * if the required MSHA
ventilation rates were maintained during the tests, the average
concentration of NO2 over the test periods would have not
exceeded 3 ppm, the long term exposure limit for NO2.'' The
greatest increase in NO2 during the Phase I study came from
the highly platinum-catalyzed DPF. When this filter was used, the
ceiling limit of 5 ppm was briefly exceeded each time the equipment
repeated the duty cycle. These NO2 peaks were noted at the
downstream sampling location and at about the same levels at a sampling
location on the equipment near the operator's position.
NIOSH stated in the Phase II report that tests 2 and 3 (with DPF
installed) were terminated when the multi-gas monitor carried by the
equipment operator indicated that the 5 ppm NO2 ceiling
limit had been exceeded. NIOSH reported that they also believe the NO2
level may have been above 5 ppm for personal exposure on test 4 when the DPFs were not
installed on the machines (DOCs were installed on test 4).
Although tests 2 and 3 were terminated earlier than planned, these
tests lasted between approximately 2\3/4\ hours and 4\3/4\ hours,
respectively. MSHA believes that these tests were sufficient in
duration to demonstrate the differences in EC exposures with and
without DPFs. At most mines, mucking operations in an individual stope
or development end are usually completed within 2-4 hours. In fact, the
Greens Creek report results were based on approximately 2-3 hours of
sample time, which was the total time required to muck out the subject
From the intake side to the return side of the Phase II test zone,
average NO2 increase as reported were 1.2 ppm for Day 2, and
1.1 ppm for Day 3 with DPFs. The average NO2 increase was
1.1ppm for Day 4 with DOCs. It is significant to note that these
increases are consistent with the NO2 increases observed
during the Greens Creek tests, and would not be expected to result in
hazardous NO2 exposures in mines with adequate ventilation.
It should also be noted that there was no significant difference
between average NO2 increases with and without DPFs in the
test area (the DPFs were replaced by DOCs on Day 4).
As stated above, NIOSH noted that Phase II tests 2 and 3 were
terminated early due to excessive NO2 levels measured in the
cabs of the test equipment. Due to the layout of the area where Phase
II tests were conducted, it is likely that the vehicles experiencing
the highest NO2 levels were operated for part of the duty
cycle in a lower quantity of ventilation air than was available in the
main haulageway. The observed personal overexposures to NO2
occurred when the haul trucks were in this poorly ventilated area where
the intake air split at an orepass and a development section. MSHA
believes that if the air flows to these locations had been maintained
at levels near the nameplate value, the overexposure to NO2
would very likely not have occurred.
It should be noted that MSHA has documented very low ventilation
air flows in several stopes at the mine where NIOSH's Phase II study
was conducted. Ventilation measurements obtained by MSHA during a
compliance assistance visit to the mine in June 2004 identified
significant leakages from most of the auxiliary stope ventilation
systems that were evaluated. In the six stopes for which ventilation
air flow measurements could be obtained at both the auxiliary fan
location and at the end of the vent bag, the average air flow at the
fan location was 24,400 cfm and the average flow at the end of the vent
bag was 5,100 cfm. In one stope, auxiliary ventilation system leakage
was 89% and in another, leakage was 85%. Even in stopes where auxiliary
system leakage was relatively low, significant recirculation was
observed. With stope ventilation flow rates compromised to this extent
due to auxiliary system leakage and recirculation, it is not surprising
that both high gaseous emission levels and high DPM emissions have been
measured at this mine.
The NIOSH Phase II data show that gaseous contaminant levels and
ventilation flows had stabilized in the test area a short time after
the testing was initiated (within approximately the first 30 minutes),
indicating that roughly steady-state conditions had been achieved. If
tests 2 and 3 had not been terminated prematurely (i.e., if the poorly
ventilated area had been sufficiently ventilated), it is therefore
likely that the reported DPM and gaseous emission levels could have
been maintained indefinitely, or at least until mining operations were
completed in the test area.
As stated earlier, MSHA advised mine operators through the issuance
of a PIB that the use of highly platinum-catalyzed DPFs has the
potential to increase concentrations of NO2. The increases
in NO2 observed during the Stillwater Phase I and Phase II
tests demonstrate that mine operators who choose to use highly
platinum-catalyzed DPFs must maintain sufficient ventilation in areas
where the machines operate, and must monitor for any increases in
NO2. This advice is particularly important for mines that
had experienced NO2 problems prior to the introduction of
platinum wash-coated DPFs, as was the case at the Stillwater mine.
Where NO2 levels cannot be adequately controlled by
ventilation, alternatives to highly platinum-catalyzed passive filter
systems are commercially available which do not increase ambient
NO2 levels. An example that is particularly well suited to
heavy duty applications is the fuel burner type active regenerating
DPF. A system of this type is currently installed and under evaluation
at the Stillwater mine.
The results of these studies support MSHA's position that feasible
control technology exists that is commercially available to effectively
reduce miner exposures to DPM. As with any new mining machinery, mine
operators will need to thoroughly evaluate their needs prior to
ordering DPF systems to insure that each system is appropriate to the
piece of equipment, engine, application, and duty cycle. Failure to
appropriately consider these factors will likely result in poor filter
performance, poor engine performance, possible engine and filter
damage, or all of the above. Alluding to this issue, NIOSH states in
the Phase II study final report that, ``Due to the nature of the study,
Phase II did not address other and no less important matters relating
to the application of control technologies in underground mines. These
matters include selection of DPF regeneration strategies, economic,
logistical, and technical feasibility of implementation of various DPF
systems on mining vehicles, and the reliability and durability of the
systems in mine settings.''
MSHA has consistently stated that the application of commercially
available DPF systems is a task that requires mines to evaluate machine
installations on a case by case and application by application basis.
NIOSH agrees. Consequently, NIOSH and MSHA jointly developed an on-line
Internet-based Filter Selection Guide which is discussed elsewhere in
this preamble. NIOSH's written response to MSHA in this rulemaking
supports the use of DPFs as a control device that can significantly
reduce DPM exposures, but also states that the mine operator must
evaluate each machine prior to selection and installation of DPM filter
systems to insure a successful match between filter and application.
When properly selected and installed for an application, DPFs are both
durable and mine worthy. Almost without exception, failed DPFs that
have been reported to MSHA were the result of inappropriate filter
selection, manufacturer defect, or the failure of an unrelated
component (usually the turbocharger) that affected the DPF.
Active Regeneration DPFs. The active regeneration systems discussed
below are normally not catalyzed so they do not produce an increase in
Table VII-2.--Scenarios for Active Regeneration.
System name Regenerating location controller location Comments
On-board........................... On Equipment.......... On Equipment.......... Requires on-board source of
On-board........................... On Equipment.......... Designated and fixed- Requires equipment to come
location. to a specific regeneration
Off-board.......................... Off equipment......... Fixed-location........ DPFs are exchanged and must
be small enough to be
handled by one person.
Increases number of DPFs
On-board........................... On-equipment.......... On-equipment during System is complex yet fuel
operation. burner provides advantage
of regeneration during
Scenarios for active regeneration systems are listed in Table VII-
2. The second system listed in Table VII-2 is an on-board active system
that requires about one to two hours of machine down time for
regeneration, which might be available between shifts at some mines. To
regenerate these filters, the piece of equipment must be parked at a
designated location during the regeneration period so that the filter
can be connected to electrical power and compressed air. MSHA
recognizes that presently in some mines, production equipment is not
necessarily brought to a central location at the end of each shift. At
such mines, operators may need to make operational changes to
accommodate such DPF regeneration designs.
Alternatively, mine operators may choose off-board active
regeneration type filters, wherein, for example, the equipment operator
removes the DPF at the end of the shift and brings it to a central
station for regeneration. The next operator of that piece of equipment
takes a regenerated DPF to the equipment at the start of the next
shift. This system enables uninterrupted equipment operation, and does
not require the equipment to travel to a central location for filter
regeneration at the end of the shift. Where active off-board filters
are used, the size and weight of the filter element is a significant
factor in filter selection and overall system feasibility, as mine
personnel need to be capable of removing the filter at the end of the
shift and transporting it to a central regeneration station. Multiple
DPFs may be installed on a machine in place of a single large filter in
order to decrease the size and weight of individual DPFs.
Engine malfunctions and effects on DPF. Normally in mining, engine
malfunctions are indicated by excessively smoky exhaust. That indicator
will not occur when a DPF system is installed. Malfunctions such as
excessive soot emissions, intake air restriction, fouled injector, and
over-fueling, may result in an abnormal rise in back pressure in
systems that do not spontaneously regenerate. Also, these conditions
could lead to abnormal changes in back pressure in passive systems
because the malfunction may raise exhaust temperatures causing the
excess soot to be burned off. These malfunctions may be detected during
the usual 250-hour maintenance and emissions checks conducted upstream
of the DPF using carbon monoxide (CO) as an indicator. The other major
filter malfunction is excessive oil consumption that is sometimes
associated with blue smoke that could be masked by the performance of
the DPF. However, excessive oil consumption leads to a rapid increase
in baseline backpressure due to ash accumulation. Excessive oil
consumption can be detected if records are kept on oil usage.
Detecting malfunctioning DPF. As noted above, the DPF can be
damaged mainly by thermal events such as thermal runaway. Shock,
vibration, or improper ``canning'' of the filter element in the DPF can
also lead to leaks around the filter element. A Bacharach/Bosch smoke
spot test can be used to verify the integrity of a DPF. Smoke spot
numbers below ``1'' indicate a good filter; smoke numbers above ``2''
indicate that the DPF may be cracked or leaking. Smoke spot and CO
tests during routine 250 hour preventative maintenance are good
diagnostic practices. Note that although a smoke spot number above
``2'' may indicate a cracked or leaking filter, such a result does not
necessarily mean the filter has ``failed'' and is not functioning
adequately. In MSHA evaluations of DPF performance at the Greens Creek
mine, filters that tested with smoke numbers above ``2'' of 7 were
still shown to be over 90% effective in capturing EC, based on
subsequent NIOSH 5040 analysis of the smoke spot filters.
Low DPM-Emitting Engines. Through its 2003 and 2004 compliance
assistance mine visits and a review of its nation-wide inventory of
diesel engines used in underground M/NM mines, MSHA has determined that
hundreds of low DPM emission engines have been introduced into
underground M/NM mines in recent years. MSHA notes that, for many mines
in the stone sector, use of low emission engines has been one of the
primary means of achieving compliance with the interim PEL.
EPA and European on-highway and non-road engine emission standards
have forced engine manufacturers to reduce both DPM and gaseous
emissions from their engines. Mine operators can purchase newer design
engines with low DPM emissions in their new diesel-powered equipment as
well as retrofitting such engines in their older equipment.
As noted earlier in this section of the preamble, the amount of DPM
reduction that can be obtained by switching to low DPM emitting engines
depends on the emission rate of the original engine compared to the
emission rate of the replacement engine. For example, if the original
engine emits 1.0 gram of DPM per horsepower per hour of operation, and
the replacement engine emits 0.2 grams of DPM per horsepower per hour
of operation, the engine replacement would achieve an 80% reduction in
emitted DPM. Other benefits of newer technology engines include better
fuel economy and more efficient maintenance diagnostics. The improved
maintenance diagnostics associated with electronic engine monitoring
systems enable lower overall equipment operating costs as well as
allowing mine operators to better monitor their engines and provide the
appropriate maintenance to keep exhaust emissions as low as possible.
During the compliance assistance visits to mines that had at least
one baseline DPM sample result exceeding the interim DPM limit, MSHA
observed numerous new or nearly new pieces of equipment powered by
Original Equipment Manufacturer (OEM)-installed MSHA-Approved engines
that had very high DPM emissions. The operators at these mines
indicated that they were unaware of the DPM emissions of the engines
that were supplied in the equipment they had just purchased. They
believed that by specifying an MSHA-Approved
engine, they would be in full compliance with the rule. While it is
true that MSHA-Approved engines satisfy the requirements of Sec.
57.5067, not all MSHA-Approved engines are necessarily low in DPM
emissions. Non-Approved EPA Tier 1 (for engines less than 50 horsepower
or 175 horsepower and greater) and Tier 2 (for engines of 50 horsepower
or greater, but less than 175 horsepower) engines are also compliant
with Sec. 56.6067, but they have lower DPM emissions. During the
compliance assistance visits, and in subsequent discussions with the
Equipment Manufacturer's Association (EMA), MSHA emphasized the need
for modern low DPM emission engines to be installed in new machines
earmarked for the underground mining industry.
Ventilation Upgrades. Several commenters expressed the view that
ventilation system upgrades, though potentially effective in principle,
would be infeasible to implement for many mines. Specific problems that
could prevent mines from increasing ventilation system capacity include
inherent mine design geometry and configurations (drift size and
shape), space limitations, and other external prohibitions, as well as
MSHA acknowledges that ventilation system upgrades may not be the
most cost effective DPM control for many mines, and for others,
ventilation upgrades may be entirely impractical. However, at many
other mines, perhaps the majority of mines affected by this rule,
ventilation improvements would be an attractive DPM control option,
either implemented by itself or in combination with other controls.
Indeed, MSHA observed during its DPM compliance assistance visits
that ventilation upgrades have been implemented at many mines in the
stone sector for DPM control, directly contradicting the commenters'
assertion that ventilation upgrades are infeasible. Nearly every stone
mine visited by MSHA had completed, had begun, or was planning to
implement ventilation system upgrades.
At many high-back room-and-pillar stone mines, MSHA observed
ventilation systems that were characterized by (1) inadequate main fan
capacity (or no main fan at all), (2) ventilation control structures
(air walls, stoppings, curtains, regulators, air doors, brattices,
etc.) that are poorly positioned, in poor condition, or altogether
absent, (3) free standing booster fans that are too few in number, too
small in capacity, and located inappropriately, and (4) no auxiliary
ventilation for development ends (working faces). At some mines, the
``piston effect'' of trucks traveling along haul roads underground,
along with natural ventilation pressure, provide the primary or only
driving forces to move air.
In naturally ventilated mines, temperature-induced differences in
air density between the surface and underground result in natural air
flows through mine openings at different elevations. Warmer and lighter
mine air rises up out of a mine during the colder winter months, which
draws in cooler and heavier air at lower elevation mine openings. In
the summer, cooler and denser mine air flows out of lower elevation
openings, which draws warmer less dense air into higher elevation
openings. Under the right conditions, such air flows can be
significant, but they are usually inadequate by themselves to dilute
and carry away DPM sufficiently to reduce miners' exposures to the
The other principal shortcoming of natural ventilation is the
inherent lack of a method of controlling air flow quantity and
direction. Ventilation air flows can slow or stop when temperature
differences between the surface and underground are small (common in
the spring and fall), and the flow direction reverses between summer
and winter, and sometimes even between morning and afternoon.
Mine operators normally supplement natural ventilation with booster
fans underground. However, if overall air flow is inadequate, as is
usually the case with naturally ventilated mines, and when mine
elevation differences or surface and underground temperature
differences are small, booster fans are largely ineffective.
The all too frequent result of these deficiencies is a ventilation
system that is plagued by insufficient dilution of airborne
contaminants, short circuiting, recirculation, and airflow direction
and volume that are not controllable by the mine operator. These
systems are barely adequate (and sometimes inadequate) for maintaining
acceptable air quality with respect to gaseous pollutants (CO,
CO2, NO, NO2, SO2, etc.), and are
totally inadequate for maintaining acceptable concentrations of DPM.
Mines experiencing these problems could benefit greatly from upgrading
main, booster, and/or auxiliary fans, along with the construction and
maintenance of effective ventilation control structures.
MSHA believes that ventilation upgrades alone, along with the
normal turnover of engines to newer, low-polluting models, may be
sufficient for many stone mines to achieve compliance with the interim
DPM limit. Consequently, MSHA has urged the mining industry to utilize
mechanical ventilation to improve overall air flows and to enable
better control of ventilating air.
Ventilation fan upgrades for the stone mining sector are usually
relatively inexpensive due to the low mine resistance associated with
large openings. In many of these mines, a 250,000 cfm air flow can be
obtained at less than 1 inch of water gage pressure. This air flow can
be provided by a 50 horsepower motor. The major cost in these
applications is usually distribution of the air flow underground to
insure that adequate air quantities reach the working faces rather than
short-circuiting to a return or recirculating around free-standing
booster fans. Good air flow distribution requires such practices as
installing or repairing ventilation control structures (brattice line,
air curtains, etc.) or changes in mine design to incorporate unmined
pillars as air walls.
Deep multi-level metal mines have entirely different geometries and
configurations from high-back room-and-pillar stone mines. They
typically require highly complex ventilation systems to support mine
development and production. These systems are professionally designed,
they require large capital investments in shafts, raises, control
structures, fans, and duct work, and they are costly to maintain and
operate. At these mines, high ventilation system costs provide a major
economic incentive to operators to optimize system design and
performance, and therefore, there are typically few if any feasible
upgrades to main ventilation system elements that these mines haven't
already implemented, or would have implemented anyway, whether or not
the DPM rule existed. Accordingly, and though it remains an option that
might be attractive in new development, MSHA expects very few mines of
this type to implement major ventilation system upgrades to achieve
compliance with this rule.
Despite the built-in incentives to design and operate efficient
ventilation systems, however, MSHA has observed aspects of ventilation
system operation at such mines that can be improved, usually relating
to auxiliary ventilation in stopes. Auxiliary fans are sometimes sized
inappropriately for a given application, being either too small (not
enough air flow) or too large (causing recirculation). Auxiliary fans
are sometimes poorly positioned, so that they draw a mixture of fresh
and recirculated air into a stope. Auxiliary fans are sometimes
connected to multiple branching ventilation ducts, so that the air
volume reaching a particular stope face may be considerably less than
the fan is capable of delivering. Perhaps most often, the ventilation
duct is in poor repair, was installed improperly, or has been damaged
by blasting or passing equipment to the extent that the volume of air
reaching the face is only a tiny fraction of that supplied by the fan.
MSHA believes that these and similar problems exist at many mines, even
if the main ventilation system is well designed and efficiently
An example is the mine where NIOSH conducted its Phase II
Production Zone study of DPFs. As noted earlier, several auxiliary
stope ventilation systems were evaluated by MSHA during an extended
compliance assistance visit to this mine in June 2004. In the six
stopes for which ventilation air flow measurements could be obtained at
both the auxiliary fan location and at the end of the vent bag, the
average air flow at the fan location was 24,400 cfm and the average
flow at the end of the vent bag was 5,100 cfm. Auxiliary ventilation
system leakage was 89% in one stope and 85% in another. Even in stopes
where auxiliary system leakage was relatively low, significant
recirculation was observed.
Optimized auxiliary ventilation system performance alone, as one
commenter noted, will not necessarily insure compliance with the DPM
interim limit. Auxiliary ventilation systems simply direct air to a
stope face so that the DPM generated within the stope can be diluted,
transported back to, and carried away by the main ventilation air
course. If this air is already heavily contaminated with DPM when it is
directed into a stope, as could happen at mines employing series or
cascading ventilation, its ability to dilute newly-generated DPM is
diminished. In these situations, the intake to the auxiliary system
must be sufficiently clean to achieve the desired amount of dilution,
requiring implementation of effective DPM controls upstream of the
auxiliary system intake. Such upstream controls might include a variety
of approaches, such as DPM filters, low-polluting engines, alternate
fuels or fuel blends, and various work practice controls, as well as
main ventilation system upgrades at the few mines where they might be
feasible. Toward the return end of a series or cascading ventilation
system, if the DPM concentration of the auxiliary system intake is
still excessive, other engineering control options would include
enclosed cabs with filtered breathing air on the equipment that
operates within the stope, or remote control operation of the equipment
in the stope to remove the operator from the stope altogether.
Environmental Cabs With Filtered Breathing Air. Cabs on mobile
equipment and control rooms or booths for stationary installations, if
provided with filtered breathing air, can be highly effective for
reducing personal DPM exposures. MSHA has determined that environmental
cabs can reduce operator exposures to DPM by 50% to 80%. In addition,
such cabs and booths can significantly reduce exposures to harmful
noise and dust, and they can also improve equipment operator comfort
The majority of equipment used in underground M/NM mining,
especially in stone mines, have suitable cabs installed. However, MSHA
has observed that many cabs, due to poor maintenance and operating
practices, fail to provide effective control of DPM exposure. Typical
problems are broken windows, ineffective door seals, inoperative AC
systems and fans, plugged or missing air filters, openings into the cab
where hoses or cables enter, and lack of company policies requiring
doors and windows to be maintained in the closed position during
Some cab ventilation and filtration systems are undersized for the
volume of air they should be moving. During MSHA's compliance
assistance visits in 2003, MSHA observed numerous pieces of equipment,
especially face drills, that were equipped with undersized cab air
filtration systems. Research has shown that cab ventilation systems
should be sized to achieve approximately one-half to one air change per
minute in their respective cabs. For example, a 100 cubic foot cab
should be ventilated by a system having the capacity to move 50 to 100
cubic feet per minute. Cabs should also be sealed to obtain a positive
pressure greater than 0.2 inches of water gage.
MSHA DPM-Related Compliance Assistance. As noted earlier, MSHA has
engaged in extensive DPM-related compliance assistance since the
existing rule was issued in 2001, and these activities are continuing.
Compliance assistance has included seminars at various locations
throughout the country, hands-on sampling training workshops, the
online Filter Selection Guide, a compliance guide, a ``single source''
internet Web site devoted to underground M/NM DPM issues, DPM baseline
sampling at all mines affected by the rule, online listings of MSHA-
Approved diesel engines and DPF efficiencies, the Estimator, and on-
site compliance assistance visits at dozens of mines, among others.
MSHA continues to consult with the M/NM Diesel Partnership (the
Partnership). The Partnership is composed of NIOSH, industry trade
associations, and organized labor. MSHA is not a member of the
Partnership due to its ongoing DPM rulemaking activities. The primary
purpose of the Partnership is to identify technically and economically
feasible controls to curtail particulate matter emissions from existing
and new diesel-powered vehicles in underground metal and nonmetal
MSHA's diesel testing laboratory located in Triadelphia, WV has
been active in evaluating many DPM control technologies. An example is
the investigation to characterize NO2 emissions from
catalyzed DPFs. As a result of this work, MSHA provided information to
the mining community on the effects of catalyzed DPF's on
NO2 production. MSHA's laboratory determined under steady
state engine operating conditions, that a heavily platinum-catalyzed
DPF would increase the NO2 concentration measured in the raw
exhaust after the exhaust gas passed through the DPF. The increase in
NO2 was compared to the required gaseous ventilation rate
for the test engine without the DPF installed. The laboratory data
showed that the gaseous ventilation rate would increase with a highly
platinum-catalyzed DPF installed. MSHA's laboratory also tested DPFs
that were either specially catalyzed with platinum (lower wash-coat
platinum content) or a base metal wash-coat (no platinum used). The
results of the laboratory tests showed no increase in the gaseous
ventilation quantity when compared to the quantity without the DPFs
installed. MSHA provided the industry with a Program Information
Bulletin (PIB) P02-04, ``Potential Health Hazard Caused By Platinum-
Based Catalyzed Diesel Particulate Matter Exhaust Filters,'' dated May
31, 2002. This PIB is located on MSHA's web page at the following
internet address: http://www.msha.gov/regs/complian/PIB/2002/pib02-04.htm.
The PIB states that mine operators that choose to use catalyzed
DPFs that have shown an increase in NO2 in the laboratory
need to ensure that the machines installed with these filters have
adequate ventilation, and recommends that personal monitoring for
NO2 should be performed.
MSHA also provides an updated list on the internet of DPFs that
have been evaluated by MSHA. The internet address is: http://www.msha.gov/01-995/Coal/DPM-FilterEfflist.pdf.
This list is divided into three tables.
Table I includes paper and synthetic filters, mainly intended to be
disposable. These DPFs are only used when the exhaust gas temperature
is maintained to below 302[deg]F, as is required in inby areas of gassy
mines. This is normally accomplished by the use of an exhaust gas heat
exchanger. Temperature sensors and backpressure sensors must be used
with these filters to protect the DPF from exhaust gas temperatures
that would exceed 302 [deg]F or backpressures that would exceed the
engine manufactures allowable limit. Table II lists ceramic and high
temperature disposable pleated element media DPFs that do not increase
the concentration of NO2 in the exhaust. Table III lists the
DPFs that are platinum-catalyzed and have been determined in the
laboratory to increase NO2 concentrations above the test
engine's gaseous ventilation rate.
MSHA's laboratory has also conducted limited tests on several
control technologies other than DPFs. Evaluations have been conducted
on an Ecomax which consists of a series of magnets installed on the
fuel system lines, Rentar, an in-line fuel catalyst installed in the
machine's fuel line, and the Fuel Preporator, a system for removing
collected air from the fuel system design for better fuel combustion.
The test results of the laboratory evaluations were inconclusive in
demonstrating significant reductions in whole diesel particulate,
however the data did not show any adverse effects on the raw DPM
NIOSH also analyzed the Rentar and Fuel Preporator for their EC
reduction potential. NIOSH's results were consistent with MSHA's
results, and showed no significant EC reductions and no adverse effects
on the engine emissions.
MSHA's laboratory evaluated the changes in engine exhaust emissions
when operating at high altitudes (greater than 1000 feet in elevation).
MSHA used two electronic fuel injected engines for the test, a Mercedes
904 and a Deutz BF4M 1013FC. MSHA first conducted field tests at engine
laboratories located at 4000 feet and 6700 feet. Next, MSHA brought the
two test engines to its laboratory. Using an altitude simulator setup,
MSHA verified the accuracy of the simulator and ran various tests to
evaluate the effects of altitude on the gaseous emissions and DPM. This
high altitude work led to the development of guidelines that MSHA is
using for approving diesel engines under 30 CFR, part 7, subpart E for
engine operation above 1000 feet.
MSHA received comments suggesting that its compliance assistance
visits at various mine sites support the position that the DPM rule,
even at the 400TC [mu]g/m\3\ interim limit, is economically
and technologically infeasible. MSHA did visit a number of mines that
were not in compliance with the interim DPM limit to provide compliance
assistance, but at each such mine, the operator was presented with
recommendations for utilizing feasible engineering and work practice
controls for attaining compliance. MSHA determined that these mines
were out-of-compliance not because it was infeasible for them to attain
compliance, but because the respective mine operators had not yet fully
implemented all feasible controls that were available to them.
MSHA's compliance assistance work at the Greens Creek mine included
an evaluation of DPM reductions obtained using heavily platinum-
catalyzed ceramic DPFs that relied on passive regeneration. The
machines were equipped with engines ranging from 300 to 475 horsepower.
The results of this testing showed that personal DPM exposures for the
subject equipment operators (loaders and haulage trucks) were reduced
by 57% to 70% when the DPFs were installed. The use of the ceramic DPFs
reduced the average engine emissions by 96%.
The Greens Creek report also showed that high DPM reductions (>90%)
occurred even when a ceramic filter was compromised by cracking around
the edges. This cracking was determined to be caused by a manufacturing
defect related to the ``canning'' process (securing the ceramic filter
in a stainless steel ``can'' for installation on the subject diesel
equipment). Through discussions with the manufacturer, Greens Creek
resolved the problem, and DPFs delivered since then have performed
satisfactorily without any cracking. In addition, the use of
environmental cabs reduced the DPM concentrations (i.e., concentration
inside the cab versus outside the cab) by 75% when DPFs were used and
80% when DPFs were not in use.
As expected, NO2 increases were observed during these
tests because the mine operator was using heavily platinum-catalyzed
DPFs. However, the increases were so small (about 1 ppm in the
downstream air flow compared to the upstream air flow in the area where
a loader and two or three trucks were operating) that it was unclear
whether the cause was data variability, slight changes in ventilation
rate, or the use of heavily platinum-catalyzed DPFs. Greens Creek
stated in its comments to this rulemaking that a 1-2 ppm increase in
NO2 is experienced when highly platinum-catalyzed DPFs are
used, but that this increase has been manageable for the mine.
MSHA agrees that a highly platinum-catalyzed filter may increase
NO2 levels based on engine duty cycle and ventilation.
NO2 is formed from NO in the engine's exhaust in the
presence of the catalyst. This reaction occurs at exhaust gas
temperatures of approximately 325[deg]C. This temperature is also the
temperature at which the platinum catalyst will allow for passive
regeneration. Manufacturers of platinum-catalyzed DPFs have normally
wash-coated their filters with large amounts of platinum to make sure
that the DPFs will regenerate. This large concentration of platinum, in
combination with the relatively long retention time of the exhaust gas
in the filter, results in the formation of NO2.
Manufacturers have been evaluating wash-coat formulations
containing less platinum loading to lower the NO2 effects.
Catalytic converters are also wash-coated with platinum; however, the
loading used on catalytic converters is lower than ceramic DPFs, and
due to faster movement of the exhaust gas through the catalytic
converter compared to the ceramic filter, NO2 increases are
minimal. One manufacturer provides an exhaust gas recirculation system
(EGR) that reduces both oxides of nitrogen (NOX) and DPM
when used in combination with a DPF.
Mine operators also have the option of using DPFs that are not
heavily wash-coated with a platinum catalyst. One manufacturer offers a
lightly platinum-catalyzed DPF that is used in conjunction with a
platinum-cerium fuel-borne catalyst (Fuel additive). This system has a
slightly higher passive regeneration temperature requirement than
heavily platinum-catalyzed DPFs, but it produces no excess
NO2. Other options which do not produce excess
NO2 include base metal catalyzed passive regenerating DPFs,
and various on-board and off-board active regenerating DPFs. As noted
earlier, part of the DPF selection process involves an evaluation of
potential NO2 problems along with related ventilation
issues. Where NO2 exposures could be problematic, MSHA
recommends that heavily platinum-catalyzed DPFs be avoided.
Table VII-1 provides information in the ``Comments'' column on the
effects of DPF catalysts on NO2 emissions. MSHA has tested
in their laboratory the types of DPFs listed, and has posted on its web site a
list of the DPFs that can cause NO2 increases from the engine
and those catalytic formulations that do not significantly increase NO2.
MSHA is currently not aware of problems with overexposure to
NO2 at mines using platinum-catalyzed DPFs on a routine
production basis, where the overexposures are uniquely related to the
DPFs. One mine operator that had been experiencing frequent
overexposures to NO2 noted that these overexposures ceased
after a major ventilation upgrade, despite increased use of heavily
PIB 02-04 alerted mine operators that the platinum-
catalyzed DPFs identified on MSHA's web site could increase
NO2. MSHA continues to advise mine operators to monitor for
any increases in ambient NO2 concentrations with the
addition of platinum-catalyzed DPFs to their inventory.
When NIOSH's Phase II study tests 2 and 3 were terminated
prematurely due to high NO2 levels, the overexposures were
determined to be due mainly to insufficient ventilation. As discussed
previously, the average increase in NO2 from the use of
platinum-catalyzed DPFs in the test area was approximately 1 ppm, but
brief 3-5 ppm spikes were also observed. As stated above, mine
operators are advised to sample for NO2 when platinum wash-
coated DPFs are used to ensure miners are not overexposed. Mine
operators who use platinum-catalyzed DPFs should maintain ventilation
systems that are able to remove or dilute the NO2 to a non-
hazardous level, and they must be aware of localized areas where
NO2 could build up more quickly and create a health hazard
for exposed miners.
As discussed in the Greens Creek report, the use of catalyzed DPFs
at that mine did not produce substantial increases in NO2
levels. MSHA is continuing to work with filter manufacturers to
evaluate catalytic formulations on NO2 generation.
Stillwater mine DPM compliance. In its comments addressing the 2003
NPRM, Stillwater Mining Company (SMC) provided discussion and several
tables detailing its estimated DPM-related compliance costs. In its
April 2004 comments in response to the February 20, 2004 limited
reopening of the public record on this rulemaking, SMC provided further
discussion and another compliance cost summary table which grouped cost
elements into major categories. These estimates totaled about $114 to
$117 million over a 10 year period.
Using the Stillwater compliance cost estimates and other
information obtained by MSHA during visits to the Stillwater mine, MSHA
analyzed and evaluated Stillwater's estimated costs and developed a
compliance cost estimate for this mine based on an alternative DPM
control strategy. This analysis and evaluation is discussed below, and
a summary is provided in Table VII-3. MSHA conducted this analysis and
evaluation to demonstrate both to Stillwater and to other mines having
some of the same or similar equipment, mine layouts, and operating
practices that their choice of control strategy can significantly
impact overall compliance costs, and therefore, the feasibility of
MSHA's estimated yearly compliance costs for this mine, which are
based largely on the itemized cost estimates provided by Stillwater,
are between $1.24 million and $2.09 million per year. The lower end of
this range relates to estimated compliance costs not including a recent
$9 million ventilation upgrade. As discussed below, although Stillwater
included the cost of this upgrade in its estimated DPM compliance
costs, MSHA believes this cost item should not be considered DPM-
related, or is only partially attributable to DPM compliance because
the ventilation system at this mine required a major upgrade anyway,
independent of DPM issues. MSHA's $2.09 million yearly compliance cost
estimate includes the $9 million ventilation upgrade.
Although Stillwater's DPM-related compliance costs will be
significant, they are not substantially different from expectations
based on MSHA's 2001 REA. In the REA for the 2001 final DPM rule, MSHA
determined that annual compliance costs would be about $128,000 for an
average underground M/NM mine. However, Stillwater's mining operations
are not representative of an average mine. Its fleet of 350+ pieces of
diesel equipment is many times larger than the average mine's. MSHA's
estimated yearly DPM-related compliance costs for large precious metals
mines included in the REA was $659,987, based on a fleet size of 133
diesel vehicles. Stillwater's fleet is about 2.6 times larger than the
133 vehicle basis for this estimate. Thus, yearly compliance costs of
2.6 x $659,987, or $1.72 million for Stillwater would be consistent
with the 2001 REA's compliance cost estimate for a precious metals
mining operation of this size.
If the cost of Stillwater's recent ventilation system upgrade is
not included as a DPM compliance cost, which as noted below, is a
reasonable determination based on long-standing ventilation system
deficiencies at this mine, Stillwater's estimated yearly compliance
cost would be $1.24 million. As noted in the preceding paragraph, by
way of comparison, an estimated compliance cost of $1.72 million for a
precious metals mine of this size would be consistent with the 2001
REA. If, however, the entire ventilation system upgrade is considered
DPM-related, MSHA's estimated yearly compliance cost of $2.09 million
for Stillwater would be about 22% higher than expected, based on the
2001 REA. If the entire ventilation system upgrade is considered DPM-
related, but the annual savings resulting from the associated reduction
in ventilation fan power consumption is deducted from the annualized
cost of the upgrade, MSHA's estimated yearly compliance cost of $1.57
million for Stillwater would be about 9.5% less than expected, based on
the 2001 REA.
For MSHA's analysis and evaluation, Stillwater's DPM compliance
costs were grouped into six major cost categories. The analysis and
evaluation of these six major cost categories is discussed below:
1. Ventilation. As noted above, a $9 million ventilation upgrade
was recently completed at the Stillwater mine, and the cost of this
upgrade was included by Stillwater in its DPM compliance cost estimate.
However, MSHA believes this upgrade would have been necessary with or
without a DPM rule due to ongoing air quality problems and plans for
increased mine development. Thus, this expenditure should not be
considered a DPM compliance cost, or at most, only partially a DPM
Total ventilation at the mine prior to the upgrade was about
627,000 cfm, corresponding to approximately 52 cfm/actual utilized
horsepower. After the upgrade, total ventilation volume increased to
840,000 cfm, which is about 69 cfm/actual utilized horsepower.
Most of Stillwater's diesel equipment has MSHA nameplate
ventilation rates between 50 and 70 cfm/horsepower. These laboratory
derived values indicate the ventilation necessary to maintain
compliance with MSHA exposure limits for CO, CO2, NO, and
NO2. Taking into account such practical in-mine factors as
varying equipment duty cycles, imperfect mixing, use of DOCs, etc.,
acceptable air quality can sometimes be attained at ventilation rates
somewhat less than the nameplate values. However, other factors,
including out-of-tune engines, marginal auxiliary ventilation system
performance, on-shift blasting, and heavy concentrations of diesel equipment in particular
sections of a mine can result in chronic localized noncompliance with
gaseous emission limits.
For example, Stillwater has had a persistent problem with
NO2 overexposures for many years, indicating inadequate
ventilation. Per company policy, whenever an NO2 monitor
(carried by equipment operators) exceeded 5 dpm at the operator's
location, that operator was removed to the surface. The mine operator
has frequently removed miners to the surface for this reason over
recent years. Thus, the ventilation upgrade was overdue, even without
consideration for DPM levels underground.
Other considerations also factored into the decision to carry out
the ventilation upgrade, including planned production tonnage
increases, the need to utilize trucks to haul ore up grade from below
the level of the shaft bottom, an excessive number of booster fans
(sometimes competing with each other for limited air), and the desire
to increase the number of ventilation intakes into the mine (resulting
in more fresh air escape routes and lower intake air velocities to
improve miner comfort and dust conditions). By any number of measures,
mine development had overreached the old ventilation system. The
ventilation upgrade accomplished all of the above objectives, and
resulted in a reduction of total fan power consumption by 1,000
Even if this ventilation upgrade could be entirely attributed to
DPM compliance, the cost must be annualized over the expected 20+ year
life of the asset, so the yearly cost (using a 7% discount rate) would
be about $850,000. This yearly cost is partially offset by savings in
electricity costs resulting from the 1,000 horsepower reduction in fan
power consumption, so the ventilation upgrade actually resulted in a
net annual cost to Stillwater of only about $197,000 (1,000 hp x 24
hours/day x 365 days/year x 0.745 kw-hr/hp-hr x 10[cent]/kw-hr =
$652,620; $849,536 - $652,620 = $196,916).
2. Diesel Engines and Engine Upgrades. Only a portion of the
expense of new diesel engines and engine upgrades should be considered
a DPM compliance cost. Diesel engines have a finite life and need to be
renewed and replaced periodically. Some new engines and engine upgrades
would have been necessary with or without a DPM rule. Also, new, low-
emission engines enable improved operating efficiencies due to lower
fuel consumption and better maintenance diagnostics, resulting in
significant operating cost savings that partially off-set purchase
Like the ventilation upgrade, however, even if the total cost of
engines and engine upgrades was attributable to DPM compliance, these
costs (estimated by Stillwater at $1.2 million) must be annualized over
the expected 10 year life of an engine, resulting in a yearly cost of
about $171,000 (using a 7% discount rate).
3. Soot Traps, Filters, Passive DPFs. The mine currently has fewer
than 30 passive regeneration DPF systems and only one passive/active
regeneration DPF system (fuel burner) in use, and reports no
operational problems at this time, except one filter destroyed by a
In its comments to the 2003 NPRM, Stillwater outlined a plan for
utilizing a combination of passive and active DPFs to control DPM in
its mine. Passive filters would be used where equipment duty cycles and
corresponding exhaust temperatures suggested the application would be
successful, and active filters would be utilized on the remaining
equipment. Stillwater reports $160,000 in passive filter costs to date.
Assuming a filter life of two years, this results in a yearly cost of
about $88,500 (using a 7% discount rate).
4. Engine Test Equipment. The engine test equipment has a 5-year
life, resulting in an annualized cost of about $68,000 (using a 7%
5. Emissions expenditure. The basis for Stillwater's ``Emissions
expenditure'' line item cost of $43,000/month is unclear. As noted
above, the mine currently has fewer than 30 passive regeneration DPF
systems and only one active regeneration DPF system in use, and reports
no operational problems at this time, except one filter destroyed by a
failed turbo-charger. Engine-related emissions expenses are addressed
in the diesel engines, engine upgrades, and engine test equipment line
items above. However, ``emissions expenditures'' of $516,000 per year
($43,000 per month x 12 months) are included as submitted by Stillwater
in MSHA's estimated compliance cost.
6. Active Regeneration Systems. Based on Stillwater's existing
knowledge base relating to equipment duty cycles and exhaust
temperatures, their plan for controlling DPM emissions included passive
filters for only a small percentage of the mines' fleet: the large
loaders and ore haulage trucks. In contrast, about 200 vehicles were
expected to require active regeneration DPF systems.
For costing the active systems, Stillwater made the following
a. Regeneration of the DPFs would be accomplished on-board the
vehicles. Vehicles equipped with DPFs would travel from their normal
work areas (stopes, develop ends, haulageways, etc.) to specially
excavated regeneration stations provided with the necessary means of
connecting the filters to power and compressed air. Upon arrival at a
regeneration station, the filters would be ``plugged in'' to electrical
power and compressed air utilities to accomplish regeneration.
b. In addition to including the costs of filters and associated
regeneration equipment, Stillwater's active DPF cost estimates also
included excavating the regeneration stations and installing the
required electrical power and compressed air.
c. To insure reasonable travel distances to regeneration stations
as mine workings advance over time, Stillwater's cost estimate was
developed in the context of a 10-yr mine plan that included the
excavation of new regeneration stations periodically over the 10 years.
Stillwater's total estimated costs for active filter systems,
regeneration equipment, and regeneration stations was about $104.4
million over the 10-yr period of the mine plan. Of this total, $100.8
million (96.6%) was for excavation of the regeneration stations, and
$3.6 million was for active filter systems and regeneration equipment.
Neither the number of active systems required at Stillwater, nor
the estimated total cost of implementing active filters as specified in
Stillwater's comments is disputed by MSHA. However, MSHA does not
believe the particular plan developed by Stillwater is the optimal
means of utilizing active DPM filters at this mine. Various alternative
approaches for utilizing active filters exist which would be far less
Since excavating regeneration stations accounted for over 96% of
the total cost of implementing Stillwater's active filter plan,
alternatives that do not include such excavation costs would have a
significant cost advantage over Stillwater's plan. It is somewhat
curious that Stillwater developed its active DPF plan on the basis of
this particular on-board active regeneration system, despite the
extraordinarily high cost of excavating the regeneration stations, and
Stillwater's prior experience with premature failure of the on-board
heating elements built into the filters.
A lower cost alternative to Stillwater's approach utilizes an on-
board fuel burner system to regenerate filters. The ArvinMeritor
[reg] system has been on trial at this mine since February
2004 with excellent results. This system actively regenerates the filter media
during normal equipment operations, and does not require the host vehicle to
travel to a regeneration station to regenerate its filter.
Another less costly alternative would be to utilize off-board
regeneration instead of on-board regeneration. In off-board
regeneration, a dirty filter is removed and replaced with a clean
filter at the beginning of each shift. During shift change, the dirty
filters are then transported by the equipment operator or a designated
filter attendant to a central regeneration station or stations.
Such stations could be a fraction of the size of the regeneration
stations envisioned in Stillwater's plan, because they would only need
to accommodate the filters, not the host vehicles. Since the host
vehicles would not need to travel to the regeneration stations, the
travel distance from normal work areas to the regeneration stations
would be less important, greatly lessening the need for frequent
construction of new regeneration stations as the workings advance. It
is very likely that such stations could be co-located in existing
underground shops, unused muck bays, unused parking areas, or other
Off-board regeneration might not be practical on larger machines
due to the size of the filters. For larger machines that are not
suitable for passive regenerating filters, the fuel burner approach
might be preferable. But many of the machines targeted for active
filtration are quite small, having 40 to 80 horsepower engines. Active
filters for these engines are correspondingly small, and could be
easily and quickly removed and replaced using quick disconnect
Another lower cost option would be to utilize disposable high-
temperature synthetic fabric filters, especially on smaller, light duty
equipment such as pickups, boss buggies, and skid steers. Depending on
equipment utilization, such filters might only need to be replaced once
or twice per week.
In Table VII-3, the line for active filters shows the 10-year cost
of Stillwater's plan for utilizing active filters along with MSHA's
estimate of the yearly cost of alternatives to Stillwater's plan.
MSHA's cost estimate for this line item is based on Stillwater's
estimated cost for active filter systems, minus the cost of excavating
regenerations stations, or $3.6 million over 10 years. Annualizing
these active filter costs over the two-year expected life of these
filters using a discount rate of 7% results in a yearly cost of about
Table VII-3.--Stillwater's and MSHA's DPM Compliance Cost Estimates
Cost item estimate MSHA cost estimate MSHA comments
Mine Ventilation Upgrade........... >$9 million........... $0.................... This upgrade necessary with
or without DPM rule to
address ongoing air
quality problems and plans
for mine development.
$849,536/yr \1\....... Even if upgrade necessary
for DPM compliance, this
capital cost annualized
over expected 20+ year
life of the asset.
$327,440/yr \1\....... Annualized cost over
expected 20+ year life of
the asset minus annual
power cost savings.
Engine upgrades, other misc. >$1.2 million......... $170,853/yr \1\....... Some engines/upgrades part
expenses. of normal turnover of
engines and not DPM
compliance cost. Cost of
annualized over 10 year
expected engine life.
Test Equipment..................... >$280,000............. $68,289/yr \1\........ Cost of test equipment
annualized over 5 year
expected equipment life.
Soot traps, filters, passive DPFs.. $160,000.............. $88,495/yr \1\........ Cost of DPFs annualized
over 2 year expected
Emissions expenditure.............. $43,000/month......... $516,000/yr \1\....... Cost element is unclear
based on current filter
Active DPF systems, regeneration $104.4 million over 10 $398,226/yr \2\....... Less costly approaches for
equipment, and regeneration years. implementing active
station excavation. regeneration were
that do not require
excavation of regeneration
stations save $100.8
million over 10 years.
$3.6 million would still
be required for filters
equipment, however, this
expense would be incurred
over 10 years.
Grand Total.................. $104.4 million over 10 Annual cost of $1.24 Certain cost elements
years for active to $2.09 million. should not be considered
DPFs, plus $10-$13 $1.24 million if cost DPM compliance costs.
million for other of ventilation However, even including
costs over 10 years. upgrade is not ALL listed costs for
Total cost $114-$117 included;. ventilation, passive and
million over 10 years. $2.09 million if cost active DPFs, engines/
of ventilation engine upgrades, test
upgrade is included;. equip, and emissions
$1.57 million if cost expenditures, MSHA
of ventilation estimates total yearly
upgrade is included cost for DPM compliance
minus power cost will not exceed $2.09
savings. million. Excluding
total yearly cost is $1.24
considering power cost
savings, estimated total
yearly cost is $1.57
million. Estimated yearly
compliance cost of $1.72
million for a precious
metals mine of this size
would be consistent with
\1\ Cost estimate based on commenter's estimated cost, annualized over the expected life of the item using a 7%
discount rate. The annualization factor for a capital expenditure is 9.4% for 20 years, 14.2% for 10 years,
24.4% for 5 years, and 55.3% for 2 years.
\2\ Cost estimate based on commenter's estimated cost for active systems minus the cost of excavating
regeneration stations, annualized over the expected life of the active systems.
Kerford Limestone DPM compliance. Kerford Limestone reported the
results of a consultant's study that indicated compliance with the DPM
limit for that mine would cost $348,000 for engine improvements, $1.15
million for ventilation upgrades, and $25,500 to $38,500 per year for
DPFs. They reported investing $975,000 to date toward DPM compliance.
Kerford's engine costs of $348,000, when annualized over 10 years
at a discount rate of 7%, results in a yearly cost of about $49,500.
The $1.15 million ventilation cost, when annualized at the same
discount over the expected 20+ year life of this asset, results in a
yearly cost of about $108,600. When these two yearly costs are added to
the maximum estimated annual DPF cost of $38,500, the total yearly cost
for Kerford is about $196,600.
Without commenting specifically on the reasonableness of Kerford's
itemized cost estimates or whether the overall DPM control strategy
proposed by its consultant was optimized for this mine, MSHA notes that
Kerford's self-reported total yearly compliance cost of about $196,000
is not excessive for an underground stone mine in its size category. By
way of comparison, a yearly compliance cost of over $300,000 for a
stone mine of this size would be consistent with MSHA's REA for the
existing 2001 final rule.
MSHA's REA for the existing 2001 final rule estimated compliance
costs for a medium sized (20 to 500 employees) stone mine to be
$150,738. However, this estimate was based on a fleet size of 9.5
pieces of production equipment for this industry sector and mine size
category. Kerford operates 19 pieces of production equipment. Adjusting
the REA estimate of $150,738 for the larger fleet size at Kerford
results in an estimated yearly compliance cost of $301,476. Thus,
Kerford's estimated $196,600 yearly compliance cost is only about 65%
of the level that would be expected for an underground stone mine of
this size, based on the 2001 REA. The cost is virtually unchanged in
the REA supporting this final rule.
It was suggested by a commenter that MSHA underestimated Kerford
Limestone's compliance costs by over $1 million, and it was further
suggested that this underestimate, if extrapolated to the entire
underground stone mining industry, resulted in industry-wide compliance
costs exceeding $100 million. However, Kerford Limestone's yearly
compliance costs, using its own cost estimates, are substantially less
than expected, based on the 2001 REA for a medium sized underground
Bio-Diesel tests at Carmeuse Black River and Maysville mines.
Commenters stated that in-mine tests with bio-diesel fuel produced
measurable reductions in ambient DPM concentrations, but did not bring
the subject mine into compliance. These comments refer to MSHA's
compliance assistance work at the Carmeuse Black River and Maysville
stone mines in Kentucky. At both mines, the use of bio-diesel fuel
produced reductions in DPM. The recycled vegetable oil (RVO) with a 50%
blend of bio-diesel to standard diesel fuel showed a 69% reduction in
DPM, based on TC, for the area samples at the Maysville mine. Personal
samples collected at the Black River Mine showed a 44% reduction in DPM
with RVO at a 35% blend of bio-diesel to standard diesel fuel. The
Virgin Soy Oil (VSO) mixtures showed reductions, but they were not as
effective as the RVO at similar blends.
The Maysville mine was in compliance with the interim limit based
on the baseline samples and the samples taken with bio-diesel. In
contrast, the Black River Mine was not in compliance with the interim
limit based on the samples taken, even with the reduction in DPM using
bio-diesel. One main difference between the two mines was that the
Maysville mine had significantly more ventilation than Black River.
This result indicates that the Black River mine will have to implement
additional DPM controls to come into compliance, such as ventilation
upgrades, cleaner engines, or DPFs.
These commenters did not dispute the DPM reductions obtained.
However, they indicated the following: That Deutz Corporation's
Technical Circular does not approve the use of bio-diesel blends above
20%; that a 50% bio-diesel fuel presented insurmountable equipment
problems; and that the cost of bio-diesel has increased significantly,
adversely impacting the feasibility potential of the 20% mixture.
MSHA reviewed Deutz's Technical Circular (0199-3005en), and
discussed this issue with Deutz. The Technical Circular provides a
general statement that bio-diesel fuel is approved for Deutz brand
engines. The Technical Circular does not mention any limitation on the
use of bio-diesel above a certain percentage blend. Deutz requires that
all fuels used in their engines meet Deutsches Institute fur Normung
e.V. (DIN) specifications (German National Standards). The Deutz
Technical Circular provides the DIN specifications for bio-diesel fuel.
Comments regarding equipment problems relate to reports of bio-
diesel fuel causing clogging of fuel filters, resulting in excessive
equipment downtime. One commenter expressed concern that Tier 2 engines
used fuel filtering systems that would not be compatible with bio-
diesel. MSHA understands that engine manufacturers are working with the
filter manufacturers to provide the best filtration for all engines.
MSHA is not aware of any unique changes for EPA Tier 2 engines as
related to fuel filtering systems or for utilizing bio-diesel fuel. As
the engine technology continues to improve, especially in the area of
the fuel system components, better fuel filtration systems will be
utilized by the engine manufacturers.
There are frequent references in the technical literature to bio-
diesel fuels initially cleaning old sediments out of fuel lines,
thereby causing fuel filters to clog. It follows that fuel filters
should be changed more frequently when bio-diesel is first used in a
fuel system. However, the commenter suggests an entirely different type
of incompatibility that is not limited to the transition period when
bio-diesel is first used. This may or may not be a unique situation
that may take additional work to resolve. The mine may have to install
an additional by-pass filtering system on the machine to allow the
operator to switch to another set of fuel filters instead of shutting
down production if a fuel filter clogs.
MSHA is not aware of long term filter clogging with the use of bio-
diesel fuel. However, through the NIOSH List-Server, mine operators
have the opportunity to share experiences like the filter clogging
problem with the mining community, and possibly receive a solution. A
mine operator may use the List-Server to ask others in the mining
community if their problem has been observed in other situations.
Interested parties can respond, thus sharing experiences and solutions
in a timely manner. The List-Server was established by the diesel team
at NIOSH, Pittsburgh in response to the expressed and obvious need for
a means to disseminate and share information and experiences concerning
the application of available technologies for the reduction of miner
exposures to DPM and gaseous emissions in underground mines.
Regarding the cost of bio-diesel, MSHA acknowledges that users pay
a premium for bio-diesel over standard diesel fuel. The cost for bio-
diesel can vary based on such factors as market price swings in the
cost of feed-stocks, state tax incentives, proximity to production
facilities, etc., but normally, where bio-diesel is available, the
premium is about one cent per gallon per percent bio-diesel in the fuel
blend. At higher percentage bio-diesel blends, this premium can result
in significantly higher overall fuel costs for the end-user. Depending
on mine-specific factors, however, use of bio-diesel may be a cost-
effective DPM control option, either used by itself or in conjunction
with other controls. Since the rule is performance oriented, the mine
operator is free to choose the means of compliance.
Based on these results and other data, MSHA's believes that bio-
diesel is a feasible DPM control. In the case of the Black River mine,
bio-diesel would have to be used in combination with other controls for
the mine to achieve compliance, or the mine operator may choose to
abandon bio-diesel altogether and rely entirely on other controls for
attaining compliance. MSHA disagrees with the commenters' assertion
that a 50% bio-diesel blend presents ``insurmountable equipment
problems.'' Bio-diesel is recognized by the EPA as an alternative clean
fuel, engine manufacturers do not recommend against its use, and
clogging can be prevented by the use of by-pass filtering systems.
Water Emulsion Fuel: As discussed under the MSHA compliance
assistance activities, we conducted tests at four mines to evaluate
water emulsion fuel. These tests included a test at a small clay mine
that used older technology engines, two single level limestone mines
that used clean burning engines, and one multilevel limestone mine that
used clean burning engines. Summer (20% water) and winter (10% water)
blends of fuel were tested at two mines. Only summer blends of fuel
were tested at the other two mines. MSHA evaluated the reduction in
total mine DPM emissions by taking measurements at the mine exhaust
openings, with and without the water emulsion fuel in use, and
comparing these to similarly made measurements when standard No. 2
diesel fuel was used. Table VII-4 summarizes the reductions in
emissions measured for the tests.
For clean burning engines the reduction in DPM emissions (as EC)
ranged from 63 to 81 percent. For older engines the reduction in DPM
emissions (as EC) was approximately 49 percent. Personal exposures were
also reduced, however, this reduction was more variable than the
reduction in engine emissions. This variability was attributed to the
use of cabs, location in the mine and the specific ventilation rates at
the work area in the mine.
Table VII-4.--Emission Reductions for Water Emulsion Fuel Tests
Mine in EC in EC
Clay............................................ .......... 49
Limestone....................................... 77 81
Limestone....................................... 63 73
Multilevel Limestone............................ .......... 80
For each mine test, equipment operators reported a noticeable loss
of horsepower. However, this horsepower loss, even in the multilevel
limestone mine, did not adversely effect production. In fact, during
several of the mine tests, production was significantly above normal.
The water emulsion fuel was favorably received by the employees.
Workers reported that visibility improved. The water emulsion fuel has
the same per gallon cost as No. 2 diesel fuel. Several operators
reported as much as a 20 percent increase in fuel usage to compensate
for the power loss.
During the water emulsion fuel tests, a potential operating problem
was observed when the fuel was used in Deutz engines. Simply put, some
engines would not run. The source of this problem was traced by the
engine and fuel manufacturers to a high efficiency water separator in
the engine fuel line. The engine and fuel manufacturers have indicated
that the problem can be corrected by replacing the standard high
efficiency water separator with a less efficient unit.
We believe that the use of water emulsion fuels provides a
significant reduction in diesel engine emissions over a broad range of
applications. Currently the biggest impediment to the use of the
emulsified fuel is distribution. The manufacturer is making efforts to
make the fuel more widely available.
MSHA has not tested the fuel at high altitude mines (above 5000
feet). At these elevations there are potential problems due to
additional horsepower loss, steep grades and low winter temperatures.
MSHA is working with the fuel manufacturer and mining industry to
evaluate these concerns.
Combining DPM Controls Into An Overall Strategy. The DPM rule
allows mine operators flexibility in choosing engineering and
administrative controls that are appropriate for site-specific
conditions and operating practices. During its compliance assistance
visits, MSHA urged mine operators to combine various engineering and
administrative controls, including work practices, into an integrated
DPM control strategy for their mines. For example, in stone mines where
haulage trucks transport broken stone out of the mine to a surface
crusher, and where the truck drivers are protected by effective
environmental cabs with filtered breathing air, MSHA recommends that
the main ramp used by the haulage trucks to travel out of the mine be
maintained as an exhaust air course. Typically, the combined horsepower
of the production loader and haulage trucks at a stone mine exceeds the
horsepower of all other equipment combined. When haulage trucks travel
loaded upgrade out of the mine, they generate significant amounts of
DPM. If the ramp used by these trucks is maintained as an intake air
course, the fresh air supply for the entire mine can become
contaminated. Maintaining this ramp as an exhaust air course and
requiring the loaded trucks to haul up this ramp as an administrative
control enables the mine operator to provide better ventilation air
quality along the face line. Depending on mine layout and ventilation,
it may be possible to maintain all ramps traveled by the haulage trucks
as exhaust air courses. It is especially important, however, that the
ramps used for upgrade loaded haulage be maintained as exhaust air
courses. This combination of engineering (cabs and ventilation) and
administrative controls (loaded trucks haul up the ramps used as
exhaust air course) particularly benefits powder crew workers who are
required to work most of their shift outside of a protective cab.
Some commenters stated that the industry has exhausted the ``easy''
methods of DPM control, and reducing DPM to lower limits would be
prohibitively expensive. MSHA is not entirely certain what is meant by
``easy'' methods, but suspects the commenter was referring to DPM
controls other than major ventilation upgrades (new main fans, new
ventilation shafts, etc.) and DPFs, which are either more costly than
other options, or are perceived as more costly. At some mines, ``easy''
could also mean ``familiar,'' indicating the methods and strategies
with which these mine operators have had actual first-hand experience.
Based on this meaning, easy upgrades appear to be: Ventilation fans
(main or booster), airflow distribution systems, environmental cabs,
modern engines and alternate fuels.
By either definition, MSHA believes that only a small portion of
the industry has exhausted these control methods. For example, based on
compliance assistance mine visits, baseline sampling results, and other
data, MSHA has observed that many mines have not yet implemented relatively low
cost ventilation upgrades, and that at most mines that have initiated
such programs, not all necessary upgrades have been completed.
Another example involves environmental cabs with filtered breathing
air. As noted above, even though most major pieces of production
equipment in stone mines are provided with cabs, the corresponding
health benefits are seldom fully realized due to open or broken
windows, company policies that permit equipment to be operated with its
doors open, inoperative or poorly maintained AC systems and cab
pressurizing fans, damaged door seal gaskets, etc.
A final example relates to the failure to employ effective work
practices such as utilizing return air courses as truck haulage roads
when the truck drivers are protected by environmental cabs with
filtered breathing air.
MSHA determined that compliance costs were economically feasible
for the M/NM mining industry. In the REA for the 2001 final DPM rule,
MSHA determined that annual compliance costs would be about $128,000
for an average underground M/NM mine. Some mines, in particular mine
size and commodity groups, because of mining methods used, equipment
deployments, etc., would be expected to incur higher than average
compliance costs. For example, the REA estimated yearly compliance
costs for large precious metals mines to be $660,000. Based on its
compliance assistance mine visits, baseline sampling results, and other
data, MSHA believes that most mines have expended far less than the
expected $128,000 yearly for DPM compliance. Though expenditures will
undoubtedly need to rise in the future as the familiar and less costly
DPM control methods are exhausted, they are not expected to exceed
levels previously determined by MSHA to be economically feasible.
C. Economic Feasibility
MSHA has determined that a PEL of 308 micrograms per cubic meter of
air (308EC [mu]g/m3) is economically feasible for
the M/NM mining industry. Economic feasibility does not guarantee the
continued viability of individual employers, but instead, considers the
industry in its entirety. It would not be inconsistent with the Mine
Act to have a company which turned a profit by lagging behind the rest
of an industry in providing for the health and safety of its workers to
consequently find itself financially unable to comply with a new
standard; See United Steelworkers of America v. Marshall, 647 F.2d
1189, 1265 (1980). Although it was not Congress' intent to protect
workers by putting their employers out of business, the increase in
production costs or the decrease in profits would not be sufficient to
strike down a standard. See Industrial Union Dep't., 499 F.2d at 477.
On the contrary, a standard would not be considered economically
feasible if an entire industry's competitive structure were threatened.
Id. at 478; See also, AISI-II, 939 F.2d 975, 980 (DC Cir. 1991); United
Steelworkers, 647 F.2d at 1264-65; AISI-I, 577 F.2d 825, 835-36 (1978).
This would be of particular concern in the case of foreign competition,
if American companies were unable to compete with imports or substitute
products. The cost to government and the public, adequacy of supply,
questions of employment, and utilization of energy may all be
considered when analyzing feasibility.
MSHA has also determined that there will be a small cost savings in
economic impact on the mining industry under this final rule, because
the requirements for meeting the PEL are similar to those in the
existing DPM enforcement policy for the 2001 DPM standard.
Specifically, MSHA will continue to require mine operators to
establish, use and maintain all feasible engineering and administrative
control methods to reduce a miner's exposure to the PEL. The final rule
affords mine operators the flexibility to choose either engineering or
administrative controls, or a combination of controls to reduce a
miner's exposure. In the event that controls do not reduce a miner's
exposure to the PEL, are not feasible, or do not produce significant
reductions in DPM exposures, the operator must use and maintain
controls to reduce the miner's exposure to as low as feasible and
supplement controls with respiratory protection. Mine operators must
establish a respiratory protection program when controls are
infeasible. If MSHA confirms that mine operators have met all of the
abovementioned requirements for addressing a miner's overexposure, and
the miner's exposure continues to exceed the PEL (not counting
respirators), MSHA will not issue a citation for an overexposure.
Instead, MSHA will continue to monitor the circumstances leading to the
miner's overexposure, and as controls become feasible, MSHA will
require the mine operator to install and maintain them to reduce the
miner's exposure to the PEL.
MSHA believes that it has established in this final rulemaking that
the new interim PEL is comparable to the TC interim concentration
limit. Therefore, in determining the economic feasibility of
engineering and administrative controls that the M/NM underground
industry will have to use under this final rule, MSHA evaluated the
cost of controls that are used to comply with the existing DPM TC
interim concentration limit to that of the newly promulgated EC interim
PEL. These controls include DPFs, ventilation upgrades, oxidation
catalytic converters, alternative fuels, fuel additives, enclosures
such as cabs and booths, improved maintenance procedures, newer
engines, various work practices and administrative controls. MSHA's
evaluation includes costs of retrofitting existing diesel-powered
equipment and regeneration of DPFs.
On the basis of evidence in the rulemaking record, including MSHA's
current enforcement experience, MSHA has determined that this final
rule results in a cost savings of $3,634 per year, primarily due to
MSHA's determination to delete the DPM control plan.
In highly unusual circumstances where the use of further controls
may not be economically viable, the standard provides for a hierarchy
of control strategy that allows specifically for the cost impact to be
considered on a case-by-case basis. MSHA's DPM enforcement policy,
therefore, takes into account the financial hardship on an
individualized basis which MSHA believes effectively accommodates mine
operator's economic concerns, particularly those of small mine
Whether controls are feasible for individual mine operators is
based in part upon legal guidance from decisions of the independent
Federal Mine Safety and Health Review Commission (Commission) involving
enforcement of MSHA's noise standards for M/NM mines, 30 CFR 56.5-50
(revised and recodified at 30 CFR 62.130). According to the Commission,
a control is feasible when it: (1) Reduces exposure; (2) is
economically achievable; and (3) is technologically achievable. See
Secretary of Labor v. A. H. Smith, 6 FMSHRC 199, 201-02 (1984);
Secretary of Labor v. Callanan Industries, Inc., 5 FMSHRC 1900, 1907-09
In determining the economic feasibility of an engineering control,
the Commission has ruled that MSHA must assess whether the costs of the
control are disproportionate to the ``expected benefits,'' and whether
the costs are so great that it is irrational to require implementation
of the control to achieve those results. The Commission has expressly
stated that cost-benefit analysis is unnecessary to determine whether a
control is required.
Consistent with Commission case law, MSHA considers three factors
in determining whether engineering controls are feasible at a
particular mine: (1) The nature and extent of the overexposure; (2) the
demonstrated effectiveness of available technology; and (3) whether the
committed resources are wholly out of proportion to the expected
results. A violation under the final standard will entail an agency
determination that a miner was overexposed, that controls are feasible,
and that the mine operator failed to install or maintain such controls.
According to the Commission, an engineering control may be feasible
even though it fails to reduce exposure to permissible levels contained
in the standard, as long as there is a significant reduction in a
miner's exposure. Todilto Exploration and Development Corporation v.
Secretary of Labor, 5 FMSHRC 1894, 1897 (1983).
MSHA will consistently utilize its longstanding enforcement
procedures under its other exposure-based standards at M/NM mines. As a
result, MSHA will consider the total cost of the control or combination
of controls relative to the expected benefits from implementation of
the control or combination of controls when determining whether the
costs are wholly out of proportion to results. If controls are capable
of achieving a 25% reduction, MSHA will evaluate the cost of controls
and determine whether their costs would be a rational expenditure to
achieve the expected results.
MSHA emphasizes that the concept of ``a combination of controls''
is not new to the mining industry. It is MSHA's consistent practice not
to cost controls individually, but rather, combine their expected
results to determine if the 25% significant reduction criteria, as
discussed earlier in this section, can be satisfied.
MSHA heavily weighs the potential benefits to miners' health when
considering economic feasibility and does not conclude economic
infeasibility merely because controls are expensive. Mine operators
have the responsibility for demonstrating to MSHA that technologically
feasible controls are so costly as to result in a significant economic
In situations where MSHA finds that the mine operator has not
installed all feasible controls, MSHA will issue a citation and
establish a reasonable abatement date. Based on a mine's technological
or economic circumstances, the standard gives MSHA the flexibility to
extend the period within which a violation must be corrected. If a
particular mine operator is cited for violating the DPM PEL, but that
operator believes that the standard is technologically or economically
infeasible for that operation, the operator ultimately can challenge
the citation in an enforcement proceeding before the independent
MSHA found that most of the practical and effective DPM controls
that are available, such as DPFs, enclosed cabs with filtered breathing
air, alternative diesel fuels, and low-emission engines, will achieve
at least a 25% reduction in DPM exposure. Though this final rule
affords each mine operator the flexibility to select the DPM control or
combination of controls that are appropriate to their site-specific
conditions, MSHA believes that the most cost effective DPM controls are
DPF systems. MSHA believes that there are a number of available DPFs
that do not increase production of NO2.
MSHA estimates that DPFs for the M/NM underground mining industry
range in cost from $5,000 to $12,000 per filter. This range of cost is
consistent with the reported DPF costs from the NIOSH Phase I Study. A
typical example is a 15 x 15 Engelhard DPX
platinum-catalyzed DPF used on 475 horsepower haulage trucks at a
multilevel metal mine in Alaska that costs $8,700.
The average life expectancy of a DPF is approximately 8,000 hours.
Some commenters, however, have reported life expectancies of between
2,000 and 4,000 hours, while some other commenters have reported life
expectancies for longer than 8,000 hours. However, in most of these
cases the shortened DPF life was due to a malfunction of another piece
of equipment, installation problems or a manufacturer's defect,
depending on the type of DPF selected by an operator. MSHA's 8,000 hour
estimate is based on an operation and maintenance guide prepared by DCL
Incorporated and two technical papers given at the Mining Diesel
Emission Conference in Toronto, Canada, November 1999. (See MSHA's REA
for 2001 final rule.) Support for this estimate is provided by NIOSH in
its publication titled ``Review Technology Available to the Underground
Mining Industry for Control of Diesel Emissions'' (George H.
Schnakenberg, PhD, Information Circular 9462, 2002) which reports that
average ceramic DPF service life at Agrium's Canadian potash mines is 5
years. This publication also references reports of a few Engelhard DPFs
that have been in service 10 years.
MSHA believes that the requirements for engineering and
administrative controls clearly meet the feasibility requirements of
the Mine Act, its legislative history and related case law.
The trends in DPM control technology development to date,
especially DPFs, indicate that manufacturers are creating more
innovative designs. MSHA believes that more cost effective control
methods are on the horizon. This reasoning is supported by a recently
published EPA final rule for the control of emissions from nonroad
diesel engines. The ``Clean Air Nonroad Diesel--Final Rule'' (Control
of Emissions of Air Pollution from Nonroad Diesel Engines and Fuel, 69
FR 38958 (2004)) sets emission standards for airborne contaminants,
including DPM, for all diesel engine horsepower ranges. For engines up
to 750 horsepower, the requirements will be phased in from 2008 through
2014. For engines above 750 horsepower, the final compliance date is
extended to 2015. EPA's Clean Air Nonroad Diesel Rule is a
comprehensive national program to reduce emissions from future non-road
diesel engines used in industries such as construction, agriculture and
mining. To meet these emission standards, engine manufacturers will
produce new engines with advanced emission-control technologies similar
to catalytic technologies used in passenger cars. Exhaust emissions
from these engines will decrease by more than 90%. Because the
emission-control devices can be damaged by sulfur, the EPA is also
adopting a limit to decrease the allowable level of sulfur in nonroad
diesel fuel by more than 99% from current levels (from approximately
3,000 parts per million [ppm] now to 15 ppm in 2010). This will be
consistent with the on-highway fuel sulfur requirements. New engine
standards take effect, based on engine horsepower, starting in 2008.
Both the EPA and the diesel engine manufacturers agree that clean
engine technology alone cannot achieve EPA's newly mandated emission
limits; manufacturers will also have to use advanced technology options
such as DPFs.
MSHA believes DPFs are currently commercially available for any
engine, application, or duty cycle used in underground M/NM mining.
These new EPA rules, however, will undoubtedly be technology forcing
and result in an increase in the variety, features, and capabilities of
DPFs from which mine operators may choose, as well as lower the cost of
DPFs and promote other technological innovation in this field.
In spite of these trends in new technology, MSHA recognizes that,
in a few cases, individual mine operators, particularly small
operators, may have economic difficulty in achieving full compliance with
the interim limit immediately because of a lack of financial resources to
purchase and install engineering controls.
MSHA's revised enforcement strategy is designed to accommodate this
problem. Under this enforcement strategy, MSHA allows mine operators
with feasibility issues the necessary time to reduce exposures to the
MSHA also has demonstrated that the effective date for this final
rule does not pose an economic burden for underground M/NM mine
operators. As stated earlier, the EC surrogate standard is comparable
to the existing TC surrogate standard which has been in effect since
July 2002, and has been enforced by MSHA since July 20, 2003.
Consequently, MSHA cannot justify affording mine operators additional
time to comply with an exposure limit currently enforced. MSHA believes
that the startup date is justified by the rulemaking record and the
mining industry's present capability of complying with the existing
Moreover, MSHA has afforded the underground M/NM mining industry
additional consideration in relieving the financial impact of this
final rule by delaying the period of time that was allowed for
compliance with the 2001 comparable TC concentration limit. In response
to concerns raised by the mining industry and the terms of the DPM
settlement agreement, MSHA allowed as much as 2\1/2\ years for a DPM
compliance phase-in strategy.
Specifically, on March 15, 2001, MSHA published a notice delaying
the effective date of the final DPM rule of January 19, 2001, (66 FR
5706) until May 21, 2001 (66 FR 15032). By notice of May 21, 2001, (66
FR 27863), MSHA delayed the final rule another 45 days, until July 5,
2001. Furthermore, by notice of July 5, 2001, (67 FR 9180), MSHA
delayed Sec. 57.5066(b), Maintenance standards, relating to
``tagging'' requirements. MSHA also clarified that the interim
concentration limit at Sec. 57.5060(a) and its related provisions in
the final rule would not apply until after July 19, 2002, pursuant to
its original effective date. By notice of July 18, 2002, MSHA stayed
the effectiveness of: Sec. 57.5060(d), permitting miners to work in
areas where DPM exceeds the applicable concentration limit with advance
approval from the Secretary; Sec. 57.5060(e), prohibiting the use of
PPE to comply with the concentration limits; Sec. 57.5060(f),
prohibiting the use of administrative controls to comply with the
concentration limits; and, Sec. 57.5062, addressing the DPM control
plan. These provisions were stayed pending completion of this final
Finally, in the DPM settlement agreement, MSHA agreed to enforce:
Sec. 57.5060(a), addressing the interim concentration of 400
micrograms of TC per cubic meter of air; Sec. 57.5061, addressing
compliance determinations; Sec. 57.5070, addressing miner training;
and Sec. 57.5071, addressing environmental monitoring. However, to
further assist the mining industry in instituting engineering controls,
MSHA gave the mining industry an additional year, from July 20, 2002,
until July 20, 2003, to begin to develop a written strategy of how they
intended to comply with the interim DPM concentration limit. Operators
with DPM levels above the concentration limit were to begin to order
and install controls to reduce miners' exposures by July 20, 2003.
Concurrently, MSHA provided comprehensive compliance assistance to M/NM
underground operators. MSHA retained the discretion to take appropriate
enforcement actions against operators who refuse either to cooperate in
good faith with MSHA's compliance assistance, or to take good-faith
steps to develop and implement a written compliance strategy for their
mines. Mine operators had the obligation to develop a strategy to
control DPM emissions and order engineering controls. MSHA began
enforcing the interim limit at M/NM underground mines on July 20, 2003,
under the terms of the settlement agreement.
MSHA received a number of comments in response to its proposed
economic feasibility discussion. Several commenters wanted MSHA to
define ``economic feasibility.'' They believe that controls should be
considered economically feasible if implementation would not bankrupt
the company or force the mine to close. They also believe that MSHA's
2003 NPRM did not indicate how MSHA will enforce the new language and
wanted access to records of feasibility determinations made by MSHA.
MSHA has chosen not to define ``economic feasibility'' nor
``technological feasibility'' since the Supreme Court has done so in
the OSHA Cotton Dust decision. As stated earlier in this part, the
Supreme Court defined ``feasibility'' as ``capable of being done''
(American Textile Manufacturers' Institute v. Donovan (OSHA Cotton
Dust), 452 U.S. 490, 508-509 (1981)). This preamble also discusses how
the independent Commission explains the Secretary's burden of proof in
establishing technological and economic feasibility of controls.
Commenters criticized the high costs of DPM controls associated
with attempts to achieve a significant reduction. These commenters
stated that mine ventilation systems cost more than $100 million and
provide a benefit only of a 3% to 4% DPM reduction, whereas a less-than
$100 million administrative control could achieve a 21% to 22%
First, MSHA disputes the assertion that a ventilation system costs
$100 million. MSHA assumes mines already have some form of ventilation,
since ventilation is needed whether or not DPM is a consideration. The
existing system may be minimal, and rely partly or largely on natural
ventilation, but a basic ventilation network must be present per
existing MSHA ventilation regulations (Sec. 57.8518 through Sec.
57.8535) and air quality standards (Sec. 57.5001 through Sec.
57.5039) to support normal mining operations. Thus, in the context of
the final rule, the question is not whether a ventilation system needs
to be provided for compliance, but rather, whether an upgrade to an
existing ventilation system is needed. If so, mine operators must
examine whether major additions (new shaft, new main fan, etc.) are
required, versus relatively minor improvements such as booster fans,
auxiliary ventilation system upgrades, or repair or extensions to
existing ventilation control structures. Even in an extreme case where
a new ventilation shaft and main fan installation could be justified
solely on the basis of DPM compliance, such upgrades cost far less than
$100 million. Costs in the range of $5 million to as much as $20
million would be more accurate.
MSHA also notes that the level of DPM reduction obtained through a
ventilation upgrade is proportional to the ratio of new ventilation air
flow to the existing ventilation air flow. If overall air flow is
doubled, DPM levels would be roughly cut in half. Of course factors
such as imperfect mixing and effective distribution of air flow
underground would ultimately determine the actual DPM reduction
achieved. Major ventilation upgrades costing $5 to $20 million would
typically result in DPM reductions of at least 20% to 30% or more,
which is far greater than the 3% to 4% reduction that commenters
estimated for a ventilation upgrade costing $100 million.
It is also significant to note that some DPM controls that may be
easier fixes for controlling DPM exposures may actually be quite high
in overall life-cycle costs compared to other approaches that mine
operators perceive to be higher cost options. For example, if the operator of a stone mine
determined that compliance could be achieved by installing a 150
horsepower fan costing $25,000, this control option might appear to be
advantageous compared to installing DPFs with an expected filter life
of two years on the mine's production loader and three haulage trucks
at a cost of $60,000 (4 filters x $15,000 per filter = $60,000).
However, if the total cost of the ventilation upgrade is considered,
including power costs to operate the fan 12 hours per day 6 days per
week, the annual cost for ventilation surpasses the cost for filters.
The $60,000 cost for DPFs, annualized over the two-year filter life is
$33,186 (using a 7% discount rate). The fan power cost alone would be
over $40,000 annually at $0.10 per kilowatt-hour (150hp x 12 hours/day
x 6 days/week x 52 weeks/year x 0.745 kw-hr/hp-hr x .10 $/kw-hr).
One commenter suggested that MSHA's failure to specify major
ventilation upgrades for any mine in its 31-Mine Study results in a
serious underestimate of compliance costs for those mines and the
industry as a whole. This commenter states that the trona mines have
already attained compliance with the final limit because of their high
ventilation air flow rates, and that similarly high flows will be
required at many other mines to attain compliance.
MSHA notes that the final rule is performance oriented, and allows
mine operators great latitude to choose the DPM control or controls
that are most efficient and cost effective for a given mine. The trona
mines are required to ventilate at very high rates for reasons other
than DPM compliance to address methane issues, for instance. For them,
ventilation is the logical DPM control because the control is already
in place. Other type mines have more and varied choices, and selecting
the optimum DPM control strategy involves evaluation of a broad range
of factors such as current DPM levels, equipment and engines used,
equipment deployments, mine layout, existing ventilation system,
availability of alternate diesel fuels, and many more.
For reasons of financial self-interest, mine operators would be
unwise to implement high cost controls that achieve very little DPM
reduction, such as a $100 million ventilation system that reduces DPM
levels by only 3% to 4%. Such a choice would preclude less costly and
more effective options available, such as DPFs, low emission engines,
alternative diesel fuels, and cabs with filtered breathing air.
As stated earlier, the final rule incorporates economic feasibility
in its hierarchy of controls enforcement scheme. MSHA, likewise, could
not require a mine operator to implement a control or combination of
controls where the costs are wholly out of proportion to the expected
results. MSHA would judge a ventilation upgrade costing $100 million,
or even $5 to $20 million that achieves a DPM reduction of 3% to 4% as
infeasible because the cost is wholly out of proportion to the expected
results, and it is likely a mine operator would consider it a poor DPM
compliance strategy for the same reason. The commenter suggests a lower
cost administrative control that achieves a 21% to 22% reduction would
be a better choice. MSHA agrees, if this control in combination with
other controls would result in at least a 25% reduction.
As noted previously, with some DPFs, filter efficiency is as high
as 99+% for EC. MSHA, however, believes that both economic and
technological feasibility must be considered. Whereas filter efficiency
is a major component of technological feasibility, MSHA must consider
all aspects of feasibility including implementation issues and cost of
compliance to the mining industry. As stated earlier in this preamble,
MSHA believes that some mine operators would need more time to meet a
lower DPM limit presently based on economic feasibility and
implementation issues with DPFs.
Establishing a lower interim limit in this final rule would present
complications with respect to economic feasibility, particularly where
ventilation upgrades would be needed to meet a lower limit. Moreover,
MSHA envisions that mine operators would have to filter larger numbers
of diesel-powered equipment in order to meet a lower limit. Such a
requirement could impose higher costs for the mining industry before
experience is gained at the current level and the mining industry is
given adequate time to meet a lower standard.
Some commenters objected to MSHA's assessment of the number of
mining operations that will need costly ventilation upgrades. These
operators believe that a large number of mines will have to make
ventilation improvements, provide cab improvements, add other
engineering controls, implement other administrative controls, replace
engines, and utilize DPFs. In response, the DPM rulemaking record does
not sustain this position. MSHA found in its baseline sampling that
only 37% of the mining operations covered by this DPM rule had miners
overexposed to DPM. Consequently, at 63% of the mines sampled, MSHA
found no overexposures to DPM. MSHA conducted this sampling in the same
manner as it does its enforcement of the 2001 interim limit DPM rule.
MSHA collected roughly 1,194 samples at 183 mines. Additionally, MSHA
responded to each mine operator's request for compliance assistance and
technical support for resolving engineering control implementation
issues. The results of MSHA's work are included in the rulemaking
record. Overall, the mining industry has been successful in reducing
average DPM levels as demonstrated in the comparison of baseline
sampling and 31-Mine Study data shown in Chart V-5.
Also, in the 31-Mine Study, MSHA established that most mining
operations would not need major ventilation changes, but rather, could
implement less costly ventilation upgrades and DPFs. In most instances,
the ventilation upgrades require no more than adding booster fans or
auxiliary ventilation, and repairs or extensions to ventilation control
structures such as brattice lines or air walls.
A commenter suggested that ventilation costs for complying with the
DPM rule for the Kerford Limestone mine were projected to be $1.15
million, plus $348,450 for engine replacements, plus an additional
$25,500 to $38,500 for DPF maintenance. According to the commenter,
this mine has invested $975,000 since October 2001, primarily for
ventilation improvements including sinking a shaft, consultant costs, a
new blasting truck, and a new engine for a bolter. The commenter points
out that in the 31-Mine Study, MSHA projected that first-year
compliance costs for this same mine would be only $77,600, and suggests
the discrepancy is an example of MSHA's underestimate of DPM compliance
MSHA notes that 13 DPM samples were taken during the 31-Mine Study
at the Kerford mine. Sample results ranged from 143TC [mu]g/
m\3\ to 490TC [mu]g/m\3\. Per the 31-Mine Study methodology,
DPM controls were specified based on the highest sample result.
However, since the highest sample result only exceeded the interim DPM
limit by about 23% (490TC [mu]g/m\3\ versus the interim DPM
limit of 400TC [mu]g/m\3\), the controls necessary to attain
compliance at this mine were not very extensive. Indeed, MSHA's
analysis indicated that controlling DPM emissions from the mine's three
loaders (two loaders used in normal operations plus one spare) using
active DPF systems with filter efficiencies of 80% would enable the
mine to attain compliance with the interim limit. MSHA estimated the
first year cost of three filter systems for the subject loaders plus an
oven for regenerating the filters (active off-board regeneration) to be
MSHA has not seen the consultant's report that indicates new
engines, DPFs, and a major ventilation upgrade would be required for
the Kerford mine to comply with the interim DPM limit. However, these
recommendations appear excessive based on MSHA's analysis in the 31-
Mine Study and also on the fact that compliance for this mine requires
only a relatively small reduction in DPM levels from 490TC
[mu]g/m\3\ to 400TC [mu]g/m\3\.
As noted in the 31-Mine Study final report, MSHA is not suggesting
that its findings represent the optimum compliance strategy for this or
any mine. Rather, MSHA maintained merely that the controls specified in
the final report are feasible and would be expected to attain
compliance. MSHA suspects that the combination of controls recommended
by Kerford's consultant, though capable of attaining compliance, is not
the optimum and most cost effective approach available.
As discussed in the Technological Feasibility section of this
preamble, MSHA also notes that the total yearly cost represented by the
consultant's recommended engine, ventilation system, and DPF
expenditures is roughly in line with MSHA's 2001 REA estimate for an
average mine, even though Kerford Limestone is substantially larger
than average. The engine costs of $348,000, when annualized over 10
years at a discount rate of 7%, results in a yearly cost of $49,500.
The $1.15 million ventilation cost, when annualized over the expected
20+ year life of this asset, results in a yearly cost of $108,600. When
these two yearly costs are added to the maximum estimated annual DPF
cost of $38,500, the total yearly cost for Kerford is about $196,600.
When compared to the MSHA REA's estimated compliance cost of over
$300,000 for a stone mine of this size, Kerford's costs are
Some mines, in particular mine size and commodity groups, because
of their mining methods used, equipment deployments, etc., would be
expected to incur higher than average compliance costs of $128,000 per
year. For example, the REA estimated yearly compliance costs for large
precious metals mines to be $660,000. Based on its compliance
assistance mine visits, baseline sampling results, and other data, MSHA
believes that most mines have expended far less than the expected
$128,000 yearly for DPM compliance. Though expenditures will
undoubtedly need to rise in the future as the easy DPM control methods
are exhausted, they are not expected to exceed levels previously
determined by MSHA to be economically feasible.
Another mine that disputed MSHA's estimated DPM compliance cost
estimates is the Stillwater Mine. MSHA estimated in the 31-Mine Study
that DPM filters would be required on all LHDs and haulage trucks at
this mine in order to attain compliance with the interim limit.
Accordingly, MSHA estimated Stillwater's first year costs to be
$470,100 and annual costs to be $108,163 for three loaders and twelve
trucks used in normal mining production operations plus three more
spare loaders and four more spare trucks. In its comments on the 2003
NPRM, Stillwater indicated that its total diesel equipment inventory
consists of over 350 pieces of diesel equipment, including over 90
loaders and 40 haulage trucks, plus miscellaneous production equipment
and spares. MSHA has since acknowledged that it had an inaccurate
inventory of diesel equipment for the Stillwater mine when the 31-Mine
Study was conducted. On the basis of the newly obtained inventory data,
MSHA raised its compliance cost estimate for this mine to $935,000 to
cover DPFs for the total production fleet.
In its comments on the 2003 NPRM, Stillwater submitted its own
compliance cost estimates. This estimate included a $9 million
ventilation upgrade, $160,000 for passive DPFs, $1.2 million for engine
upgrades, $280,000 for engine test equipment, $43,000 per month in
emissions expenditures, over $100 million over ten years for active
DPFs, plus various miscellaneous costs. Combining these items resulted
in an estimated annual compliance cost for Stillwater of $11 to $12
Clearly, the most significant cost item listed by Stillwater is
active DPF systems. However, almost 97% of Stillwater's estimated
active DPF systems costs are for excavation of parking areas.
Stillwater's active DPF system implementation plan specified on-board
active filter regeneration, wherein a vehicle would travel to a
regeneration station and its DPF would be connected to electrical power
and compressed air for regeneration. To insure reasonable travel
distances between normal working areas and regeneration stations,
Stillwater's active filter cost estimate was developed in the context
of a ten-year mine plan, wherein new regeneration stations would be
excavated periodically with the advance of the mine workings.
As discussed in detail in the Technological Feasibility section of
this preamble, MSHA analyzed and evaluated the Stillwater compliance
cost estimate, and determined that compliance could be attained at a
much lower cost. Since the cost of excavating regeneration stations was
such a significant component of Stillwater's overall cost estimate,
MSHA focused on eliminating this cost element. As explained in the
Technological Feasibility section, MSHA described three feasible
alternative approaches for utilizing active filtration that do not
require excavation of regeneration station parking areas. Although MSHA
disputed several of the remaining cost items, MSHA nonetheless accepted
these costs as submitted by Stillwater in developing an alternate
compliance cost estimate for this mine. The inclusion of these disputed
items accounts for MSHA's estimated compliance cost of $1.57 million
for the Stillwater mine being somewhat higher than the revised 31-Mine
Study cost estimate of $935,000.
As noted in the Technological Feasibility section of this preamble,
MSHA's estimate of $1.57 million in annual DPM compliance cost is
significant. However, it is less than MSHA estimated in the REA for the
2001 final DPM rule for a large precious metals mine. The REA estimated
annual compliance costs of $660,000 based on a fleet size of 133
vehicles. Adjustment for Stillwater's fleet size of 350+ vehicles
results in an estimated compliance cost of $1.7 million.
Several other commenters suggested that MSHA's compliance cost
estimates, in general, were unrealistically low. However, without
specific examples to evaluate and analyze, such comments are difficult
to refute. MSHA has supported its cost estimating methodologies in
general, and where specific examples have been provided by commenters,
MSHA has fully supported its compliance cost estimates, such as the
above discussions of the Kerford and Stillwater mines.
Except for general comments regarding the DPM Estimator, MSHA did
not receive information to dispute the technological and economic
feasibility for mines using room and pillar mining methods to meet the
308EC [mu]g/m\3\ limit. These mines include stone, salt,
trona and potash mines. When additional controls were necessary to
attain DPM compliance, these mines have typically elected to meet the
interim limit by upgrading ventilation, using cabs with filtered
breathing air, use of alternative fuels, and using equipment with clean engines. The
comments received from mines in these sectors of industry focused on
the difficulties of installing after-filters on large, high horsepower
equipment and the increasing cost of bio-diesel fuel. These issues,
along with the DPM Estimator, are discussed in detail in the
Technological Feasibility section of this preamble.
VIII. Summary of Costs and Benefits
The provisions in this final rule will increase compliance
flexibility with the existing final rule, and continue to reduce
significant health risks to underground miners. These risks include
lung cancer and death from cardiovascular, cardiopulmonary, or
respiratory causes, as well as sensory irritations and respiratory
symptoms. In Chapter III of the REA in support of the 2001 final rule,
MSHA demonstrated that the rule will reduce a significant health risk
to underground miners. This risk included the potential for illnesses
and premature death, as well as the attendant costs to the miners'
families, to the miners' employers, and to society at large. Benefits
of the January 19, 2001 final rule include reductions in lung cancers.
MSHA estimated that in the long run, as the mining population turns
over, a minimum of 8.5 lung cancer deaths per year will be avoided.
MSHA noted that this estimate was a lower bound figure that could
significantly underestimate the magnitude of the health benefits. For
example, the estimate based on the mean value of all the studies
examined in the 2001 final rule was 49 lung cancer deaths avoided per
year. MSHA uses the 2001 risk assessment for support of this rule.
This final rule results in net cost savings of approximately $3,634
annually, primarily due to reduced recordkeeping requirements. All MSHA
cost estimates are presented in 2002 dollars. This represents an
average annual savings of $20 per mine for the 177 underground metal/
non-metal mines that would be affected by this 2003 NPRM. Of these 177
mines, 66 have fewer than 20 workers, 107 have 20 to 500 workers; and 4
have more than 500 workers. The cost savings per mine for mines with
fewer than 20 workers will be $74. The cost increase per mine for mines
having 20 to 500 workers and more than 500 workers will be $10 and $10,
respectively. In the 2001 REA, MSHA estimated that the costs per
underground dieselized metal or nonmetal mine for the existing rule to
be about $128,000 annually, and the total cost to the mining sector to
be about $25.1 million a year, even with the extended phase-in time.
Nearly all of those anticipated costs would be investments in equipment
to meet the interim and final concentration limits.
IX. Section-By-Section Discussion of the Final Rule
A. Section 57.5060(a) Interim DPM Limit
MSHA's existing interim DPM limit at Sec. 57.5060(a), which became
applicable July 20, 2002, restricts TC concentrations in underground
mines to 400TC [mu]/m\3\. The concentration limit applies to
areas where miners normally work or travel. In the 2001 final rule,
MSHA chose TC as the surrogate for measuring DPM concentrations.
Consistent with the 2003 NPRM, final Sec. 57.5060(a) changes the
surrogate from TC to EC, which renders a more accurate measurement. In
addition, MSHA is basing the interim limit on a miner's personal
exposure rather than on an environmental concentration, which results
in a PEL. The new interim limit restricts a miner's personal exposure
for a full shift to 308EC [mu]g/m\3\. MSHA believes that
this new interim limit is comparable to the existing TC limit.
Because EC comprises only a fraction of TC, MSHA used a conversion
factor to adapt the former interim concentration limit of TC to a new
EC PEL. MSHA proposed to use a factor of 1.3, to be divided into
400TC [mu]g/m\3\, which produces a reasonable estimate of TC
without interferences. The final EC limit is based on the median TC to
EC (TC/EC) ratio of 1.3 that was observed for valid samples in the 31-
Mine Study and the DPM settlement agreement. The 1.3 factor also is
supported by information provided by NIOSH indicating that the ratio of
TC to EC in the 31-Mine Study is 1.25 to 1.67. Most commenters to
MSHA's 2003 NPRM supported an interim EC PEL of 400TC [mu]g/
m\3\ divided by 1.3 = 308EC [mu]g/m\3\.
Also in the 31-Mine Study, MSHA concluded that the submicron
impactor that MSHA used for DPM sampling was effective in removing
carbonaceous mineral dust from the DPM sampler, and therefore, its
potential for interfering with the MSHA sampling analysis. The
remaining carbonate interference is removed from the sample analysis by
subtracting the 4th organic peak. No reasonable method of sampling was
found in the 31-Mine Study that would eliminate interferences from
sources of oil mist and ammonium nitrate fuel oil (ANFO). Moreover,
MSHA could not determine DPM levels in the presence of ETS with TC as
the surrogate. Using EC as the surrogate will enable MSHA to directly
sample miners, such as those who smoke, operate jackleg drills or load
ANFO, for whom valid personal samples would be difficult to obtain with
TC as the surrogate for DPM.
MSHA has found that EC consistently represents DPM. Compared to
using TC as the DPM surrogate, using EC accomplishes the following:
Imposes fewer restrictions or caveats on sampling strategy (locations
and durations); produces a more accurate measurement; and inherently
will be more precise than TC. Furthermore, NIOSH, the scientific
literature, and the MSHA laboratory tests (see NIOSH letter dated April
3, 2002 and July 31, 2000 comment to the proposed rule for the 2001
rule) indicate that DPM, on average, is approximately 60% to 80% EC,
firmly establishing EC as a valid surrogate for DPM.
Under the new standard, MSHA is not reducing the protection from
that afforded miners under the former interim TC concentration limit,
since the old TC and new EC limits are comparable in exposure
reduction. Establishing a standard that focuses control efforts on
diminishing the DPM level in air breathed by a miner is supported by
some commenters in labor. Some commenters stated, ``We agree that
personal sampling gives a better representation of real exposure, and
we support the change.''
MSHA has determined that this new interim limit is both
technologically and economically feasible for the M/NM mining industry
to achieve. Although the risk assessment indicates that a lower DPM
limit would enhance miner protection, it would be infeasible at this
time for the underground M/NM mining industry to reach a lower interim
limit. MSHA will continue to monitor the feasibility of the affected
mining industry to comply with a lower EC exposure limit. MSHA believes
that it is critical to gain compliance experience, both from the
standpoint of DPF efficiency and implementation issues raised by the
mining industry during this rulemaking, in order to address a final DPM
Most commenters supported the value of 308EC [mu]g/m\3\
for the interim PEL. Some commenters suggested a limit of
320EC [mu]g/m\3\ as the preferred PEL. Some of these
commenters cited research by Cohen, Borak and Hall in support of their
position. The evidence in the rulemaking record, however,
overwhelmingly supports MSHA's decisions on the appropriate interim DPM
limit of 308EC [mu]g/m\3\. MSHA's review of the cited
publication by these authors demonstrated no reference to a value of
320EC [mu]g/m\3\. A 320EC [mu]g/m\3\
limit value would have resulted from using a conversion factor of 1.25,
and represents the high end of the range reported by NIOSH. MSHA
disagrees with using a limit of 320EC [mu]g/m\3\ and
believes that the limit of 308EC [mu]g/m\3\ is the
appropriate limit based on the evidence contained in the rulemaking
Another commenter stated that mine data gathered since the current
final rule was promulgated requires MSHA to lower the 2001 interim
limit. This commenter believes that all of industry could reach
compliance with the interim concentration limit without significant
economic investment and that the control technology is available to
reduce DPM to below the 2001 interim limit for feasible costs.
MSHA agrees that most of the M/NM mining industry has the
capability of reaching the new interim PEL. MSHA, however, does not
agree that compliance with the new PEL can be accomplished in every
instance and circumstance due to implementation issues that vary from
mine to mine.
During MSHA's compliance assistance visits, on many occasions it
was observed that mines had purchased new equipment or installed modern
engines in existing equipment. Several mines were using or testing
alternative fuels and many mines had made upgrades to their ventilation
systems by improving airflow distribution systems. MSHA mostly observed
that mines had not begun to install DPM filters to reduce miners'
exposures, as recommended by MSHA as the most cost-effective method of
compliance. The DPM standard does not specify that mine operators must
use a specific type of control, but MSHA recommended DPFs as a very
effective method for controlling DPM. MSHA chose to leave that decision
to the individual mine operator's judgment.
Most commenters from industry and labor continued to strongly
support the change in the surrogate from TC to EC. These commenters
stated that given the interferences known to be present in underground
mining environments, using EC as the surrogate would improve the
accuracy of MSHA samples. Some commenters criticized MSHA for not
realizing earlier that EC was a more appropriate surrogate than TC and
that use of EC would lower sampling costs of the mining industry. At
the time that the 2001 final rule was promulgated, MSHA's rulemaking
record supported TC as the more appropriate surrogate. Following
completion of the 31-Mine Study, MSHA obtained sufficient data to
change the surrogate.
Some other commenters opposed changing the surrogate. One commenter
stated that the change is without foundation because the record does
not support MSHA's claim that the amount of EC is an accurate surrogate
for the amounts of DPM that need to be measured under actual mining
conditions. MSHA disagrees. MSHA supports using EC as the most suitable
surrogate for measuring DPM. Moreover, this commenter believes that the
record does not support MSHA's claim that there is no solution to
interference issues that arise when TC is used as the surrogate for
DPM. MSHA disagrees with this comment, as well. Data in the rulemaking
record from the 31-Mine Study demonstrates that there is no
``reasonable'' solution to interference issues when using TC as the
Another commenter stated that MSHA should consider using a better
surrogate than EC, since most DPM studies were conducted on whole DPM
which would measure exposure to the most relevant substance. In
addition, this commenter believes that a substance other than EC could
be the ultimate carcinogenic agent in DPM. Many organic compounds in
DPM are known carcinogens, and there is no stable EC:TC ratio. This
commenter also believes that interferences from ETS introduce less
variability than EC. Furthermore, the commenter states that the
interference problem could be solved another way since Harvard
investigators have successfully adjusted DPM measurements for ETS.
Since the commenter did not provide a specific reference cite for the
Harvard investigation, MSHA was unable to verify this claim. MSHA based
its decisions in this final rule on the best data available to MSHA.
That data demonstrates that measuring EC for determining DPM exposures
will allow MSHA to sample miners' exposures in the presence of ETS
without interference issues. No adjustment has to be made in the sample
analysis because ETS does not affect the measurement of EC. During the
31-Mine Study, NIOSH found that there was no reliable marker for
cigarette smoke in the presence of DPM.
Some commenters suggested that MSHA establish an ``action level * *
* at which additional sampling and some controls kick in.'' These
commenters recognized that it would be difficult for MSHA to enforce an
action level below the PEL. MSHA believes that the best method of
protecting miners from exposure to DPM is through the primary use of
reliable controls. In Section VII of its feasibility analysis, MSHA
determined that the rulemaking record has little evidence at this time
to lower the PEL due to implementation and cost issues for the mining
industry. Also, MSHA's air quality standards for M/NM mines do not
include requirements for regulating action levels for other airborne
contaminants. Furthermore, pursuant to Sec. 57.5071 of the DPM rule,
mine operators are required to monitor as often as necessary to
effectively determine whether the concentration of DPM in any area of
the mine where miners normally work or travel exceeds the applicable
limit. In MSHA's experience at M/NM mines, this approach to worker
protection is more effective and practical than establishing an
``action level'' that the commenters recognize may be unenforceable.
Several comments were received on the use and development of the
error factor for DPM sampling. One commenter stated that error factors
give the benefit of doubt to mine operators and exposes miners to DPM
above an already inadequate exposure limit. This commenter also stated
that miners' health should be given precedence over mine operators'
property rights. MSHA believes that it has the burden of proving that a
sample is above the PEL for enforcement purposes. Establishment of an
error factor assists MSHA and reviewing courts in knowing when that
burden has been met. Mine operators should review their sample results
and make decisions on the level of controls required or when
improvements to controls might be necessary. However, MSHA's practice
has been to cite only when an exposure sample exceeds the standard
times the error factor.
MARG submitted data and a consultant's comments on the sampling and
analytical variability of EC measurements. These comments will be
referred to below as the ``Borak/Sirianni analysis.'' The Borak/
Sirianni analysis examined three bodies of EC sampling data. The first
of these consisted of 25 groups of four or five simultaneous EC
concentration measurements collected by MARG and summarized in Table 1
of the appendix submitted with the Borak/Sirianni analysis. This
dataset, identified below as the ``MARG basket data,'' is a portion of
the data obtained in the MARG study which was conducted in seven
underground nonmetal mines (Cohen HJ, Borak J, Hall T, et al.: Exposure
of miners to diesel exhaust particulates in underground nonmetal mines,
Am Ind Hyg Assoc J 63:651-658, 2002). The second body of data,
identified below as the ``baseline paired punches,'' consisted of two
analytical EC results on each of 223 samples from MSHA's compliance
assistance database. The third body of data examined in the Borak/
Sirianni analysis was a relatively small subset (63 samples out of over
800) of the paired-punch EC data available from the 31-Mine Study. This
dataset will be identified below as the ``31-Mine Study Subset.''
Based on the Borak/Siriani analysis, MARG concluded that ``* * *
the [measurement] system is not accurate and not feasible.'' MSHA
disagrees. Our analysis of the same data shows variability of the EC
measurements presented to be well within acceptable limits. As will be
shown below, the Borak/Sirianni analysis is mathematically invalid.
Each of the datasets is discussed below, first with respect to
deficiencies in the Borak/Sirianni analysis and then with respect to
what the submitted data actually reveal about sampling and analytical
MARG Basket Data
The submitted MARG basket data consisted of 25 groups of four or
five samples in which at least one EC measurement fell within the range
of 75 [mu]g/m3 to 200 [mu]g/m3. Neither MARG nor
the Borak/Sirianni analysis explained whether MARG collected additional
basket data falling outside of this range. Additionally, no explanation
was provided as to why the submitted data were restricted in this way,
if more data were collected.
Unfortunately, the samples were collected without the submicron
impactor. The sample results are, therefore, not appropriate to use in
this rulemaking. The study reference does not indicate the type of
filter holder and cyclone attachment configuration or if the mineral-
dust-related carbonate that occurs in the organic portion of the
analysis was subtracted off the OC determination.
When using a filter holder with an internal cyclone connection, the
cyclone nozzle acts as an impactor jet and mineral dust is deposited in
the center of the filter. This gives a high level of mineral dust in
the center of the filter, and a non-uniform deposit of material on the
filter surface. A non-uniform deposit precludes any analysis of
duplicate sample punch repeatability. Additionally, three of the seven
mines produced either limestone or trona. Both of these minerals
contain carbonates which are evolved in the organic portion of the
analysis. Failure to remove this mineral dust by use of an impactor may
affect the split point between OC and EC. The referenced study
indicates that up to 15 mg/m3 of total mineral dust was
present at one of the mines.
MARG did not provide individual sample results for this dataset.
Nor did MARG provide any information on sampling times or filter
loadings ([mu]g/cm2), both of which affect expected
analytical variability. Only summary data, consisting of the EC
measurement range, mean, standard deviation (SD), and coefficient of
variation (CV), were provided for each group of ``four or five''
samples. There was no indication of which groups contained four and
which groups contained five samples. Despite the statistical
instability of estimated SDs, CVs, and means based on as few as four or
five measurements, no confidence intervals or other measures of
statistical uncertainty were provided for the summary statistics.
The Borak/Sirianni analysis consisted of tabulating ``the number
and proportion of baskets corresponding to CV ranges of 0-4.99, 5-9.99,
>10 and >12.5%. More specifically, Borak/Sirianni observed that ``32%
of baskets containing at least one sample in the 75-200 [mu]g/
m3 range had a CV >= 12.5%.'' Although they presented no
mathematical evaluation of this finding s statistical significance,
Borak/Sirianni concluded that it was ``inconsistent with the NIOSH
criteria for appropriateness of analytical methods and does not meet
guidelines presented in the proposed Final Rule.'' \9\
\9\ The proposed rule does not, in fact, present any such
The Borak/Sirianni analysis of these data appears to be founded on
an elementary misconception: That a high percentage of individual
baskets with CV > 12.5% (based on four or five measurements per basket)
provides evidence of a high sampling and analytical CV. Actually, as
demonstrated below, the Borak/Sirianni finding reflects statistical
instability (i.e., lack of reliability) in CV estimates calculated
using only four or five measurements. CV estimates based on a limited
number of measurements display random variability around the true CV
value underlying the measurement process. It should, therefore, be
expected that many of the CV estimates based on individual baskets will
fall below, many will fall above, and none or few will fall exactly on
the true CV. More specifically, the Borak/Sirianni finding is entirely
consistent with a measurement process satisfying the NIOSH accuracy
To illustrate this point, MSHA generated a dataset of 10,000
simulated measurements randomly drawn from a log normal distribution
having mean = 126 and CV = 12%.\10\ More than 96% of these measurements
fell within 25% of the 126 mean or ``reference value,''
thereby showing that the simulated measurement process satisfied the
NIOSH Accuracy Criterion. The 10,000 ``measurements'' were then grouped
into simulated ``baskets'' of four or five measurements each,\11\ and a
separate unbiased estimate of the CV was calculated from the data
within each basket. This resulted in 2,250 separate CV estimates of the
same underlying CV, with each calculation based on four or five
measurements. Figure IX-1 displays the cumulative distribution of the
individual CV estimates. Despite the fact that the underlying CV was
12% for all these data, 808 (35.9%) of the CV estimates based on
individual baskets exceeded 12%. This demonstrates that the
corresponding Borak/Sirianni finding (32%) is consistent with meeting
the NIOSH Accuracy Criterion.
\10\ The simulated data were generated and analyzed using SYSTAT
Statistical Software, Version 10. A computer file containing this
dataset, along with a number indicating the ``basket'' to which each
``measurement'' was randomly assigned, is being placed into the
public record under the name SYMBASKETS.txt. The mean value of 126
was chosen to coincide with the overall mean concentration for the
MARG basket data, but this choice has no substantive bearing on the
results. The CV value of 12% was chosen in order to exemplify an
unbiased measurement process that satisfies the NIOSH accuracy
\11\ Since the Borak/Sirianni analysis did not reveal how many
of MARG's baskets contained four and how many contained five
samples, the 10,000 simulated measurements were divided equally into
baskets of four and five. This resulted in 1250 simulated
``baskets'' of four measurements each and 1000 ``baskets'' of five
As mentioned earlier, MARG did not provide filter loadings ([mu]g/
cm2) or sampling times for the basket data. Figure IX-2,
which is derived from the paired-punch comparison of EC results from
the 31-Mine Study,\12\ shows how NIOSH Method 5040 analytical
uncertainty is expected to vary with different filter loadings. In the
range of EC concentrations exhibited by MARG's basket data, sampling
times substantially less than 480 minutes could substantially increase
variability in the analytical results due to relatively low filter
loadings. Even if we assume, however, that MARG's basket samples were
all taken for at least 480 minutes, the submitted data do not show
excessive sampling and analytical variability. A crude estimate of the
overall CV can be obtained by pooling results from all 25 baskets. The
average of the 25 CV values given is 10.8% at a mean EC concentration
of 126 [mu]g/m3. For a dpm sample, collected with the
submicron impactor (filter area 8.04 cm2), for 480 minutes
at a flow rate of 1.7 Lpm, the concentration in [mu]g/m3 is
approximately 10 times the filter loading in [mu]g/cm2 (8.04
x 1000/480/1.7 = 9.85). As a result, the 126 [mu]g/m3
corresponds to a mean EC filter loading of 12.8 [mu]g/cm2.
Figure IX-2 shows that, at this loading, the CV expected for analytical
variability alone is approximately 10%. Since variability within
baskets reflects not only analytical variability but also variability
in the volume of air pumped and in location within each basket, an
overall CV of 10.8% is neither surprising nor excessive.
\12\ Analytical imprecision of EC measurements is quantified,
based on paired-punch results from the 31-Mine Study, in the
technical document on MSHA's Web site cited as Reference 4
in the Borak/Sirianni Analysis. In the notation of that document,
the quantity plotted in Figure IX-2 is CV[mu] [X]
calculated using [sigma][tau] = 0.256.
[sigma][tau] incorporates both intra- and inter-
laboratory analytical variability.
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MARG provided no indication that any of the analytical results for
its basket data were averaged over two punches, as per MSHA's procedure
for samples used to cite noncompliance with the DPM standard (2003
NPRM, 68 FR 48672). It should, therefore, be noted that the analytical
component of variability observed in these data would
have been reduced by a factor equal to if such averaging had been
performed [radic]2. For example, if the analytical portion of
variability amounted to a CV of 10%, then this would have been reduced
to 7.1% if two punches had been averaged for every measurement.
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BILLING CODE 4510-43-C
Baseline Paired Punches
The baseline paired-punch data examined in the Borak/Sirianni
analysis consisted of laboratory results from 223 samples, collected
during MSHA's baseline compliance assistance program, that were
analyzed twice for EC content.\13\ In accordance with MSHA's interim
policy for DPM noncompliance determinations, a second punch was
analyzed from each of these samples because the first punch showed EC
>= 30 [mu]g/cm\2\ or TC >= 40 [mu]g/cm\2\ (see 2003 NPRM, 68 FR 48672).
Results from the two punches were then averaged for purposes of
determining compliance or noncompliance with the interim exposure
\13\ The Borak/Sirianni analysis erroneously states that all 223
of these samples were ``collected using an older version of the SKC
impactor that differs from the impactor proscribed [sic] in the
proposed final rule.'' We assume that the intended word was
``prescribed.'' As explained in the 2003 NPRM at 68 FR 48679-80 and
48706, there has been no change to the impactor in the SKC sampler.
For reasons explained elsewhere in this preamble, an improvement was
made in the SKC filter capsule, but this change has no bearing on
the comparison of paired punches taken from within the area of
deposit on the filter. The older design, employing a crimped foil
capsule, was used for 93 of the 223 samples. The remaining 130
samples utilized the newer design, in which a retaining ring
replaced the crimped foil.
The Borak/Sirianni analysis of these 223 paired-punch results
consisted of calculating, for each pair, the ``percentage difference''
between the two punch results and tabulating the frequency of cases in
which that quantity fell into three categories: 0-4.99%, 5-9.99%, and
>=10%. The ``percentage difference'' was apparently calculated as
X1, where X1 is the first measurement recorded
within each pair. No explanation was given of the statistical
properties of this quantity, and no discussion was presented of its
mathematical relationship to a CV, which is defined quite differently.
In particular, Borak/Sirianni made no attempt to relate the
``percentage difference'' mathematically to CVA, which
refers to the coefficient of variation for the average (not
difference!) of two punch results. Nevertheless, the authors concluded
(without explanation) that the frequency of cases in which the
``percentage difference'' exceeded MSHA's estimate of CVA
indicates that MSHA's estimate is too low. They also asserted that ``it
is almost certain'' that these data ``document failure to meet the
NIOSH and MSHA acceptability criteria.''
The Borak/Sirianni analysis of these data commits the following
five errors. The first three of these distort their analysis
sufficiently to render its conclusions entirely without merit.
1. Our best estimate of the true carbon loading on a filter is
given by the average of the two available punch results from that
filter. Therefore, individual measurement errors are best estimated as
the distance of each result from the midpoint between them. In
contrast, the ``percentage difference,'' as defined by the Borak/
Sirianni formula, is twice the size of the percentage deviation of
either punch result from the midpoint between them. This serves to
exaggerate the deviation of each result from the true value.
Mathematically, the relative standard deviation (RSD) of the difference
exceeds the RSD of an individual punch result by a factor of [radic]2
(prior to any blank adjustment).
2. Borak/Sirianni fail to account for the fact that MSHA's estimate
of CVA applies to the average of two punch results, rather
than to an individual analytical measurement. The RSD of an individual
punch result exceeds the RSD of the two-punch average by another factor
of [radic]2 (again, prior to any blank adjustment).
3. The combined effect of (1) and (2) is that, when blank
adjustments are negligible, variability in the ``percentage
difference,'' as expressed by an appropriate CV within pairs, would be
expected to exceed analytical imprecision in a 2-punch average by a
factor of 2. However, Borak/Sirianni made no attempt to calculate such
a CV or make any other meaningful comparison. Instead, they simply
tabulated instances in which the ``percentage difference'' exceeded
CVA. CVA, like any coefficient of variation, does
not represent an upper bound on individual deviations or differences.
Indeed, approximately one-third of individual errors (without regard to
direction) would normally be expected to exceed the corresponding CV.
(This is why MSHA multiplies the appropriate CV by a ``confidence
coefficient'' when establishing a 1-tailed 95% confidence error factor
for noncompliance determinations.) Combining the factor of 2 explained
above with a 95% 2-tailed confidence coefficient (1.96), ``percentage
differences,'' as defined by Borak/Sirianni, are expected to exceed
2x1.96xCV more than 5% of the time. (The reason such excesses would be
expected more than 5% of the time is given below, under point 4.)
4. The Borak/Sirianni method of calculating ``percentage
difference'' causes such differences to take on more extreme values
than they would if they were calculated relative to the average of the
two punch results (i.e., if the denominator of the calculation were the
average of X1 and X2 rather than just the
X1 result). For example, using the Borak/Sirianni formula, a
sample with two punch results of 192 and 212 would yield a ``percentage
difference'' of either 10.4% or 9.4%, depending on which one of the two
measurements is recorded as X1. If, instead, the average of
X1 and X2 were used as the denominator, then the
percentage difference would be calculated as 9.9%.\14\ So long as the
smaller result is equally likely to be X1 as X2,
the Borak/Sirianni formula for ``percentage difference'' increases some
percentage differences and decreases others. Nevertheless, as shown in
this example, the Borak/Sirianni formula artificially increases the
count of differences exceeding 10% (or any other specified value).
Furthermore, as will be explained later, the Borak/Sirianni formula for
``percentage difference'' induces an even greater systematic bias in
their analysis of the 31-Mine Study subset.
\14\ Note that, in this example, the relative deviation of
either X1 or X2 from the midpoint between them
is actually 10/202 = 4.95%. This would be the appropriate value for
comparison to a CV or RSD quantifying measurement imprecision.
5. The Borak/Sirianni analysis ignores heterogeneity of the
analytical CV within the range of EC loadings considered. As indicated
by Figure IX-2, the frequency of relatively large percentage
differences would be expected to increase at low EC loadings. The
method shown in ``Metal and Nonmetal Diesel Particulate Matter (Dpm)
Standard Error Factor for TC Analysis,'' published on MSHA's Web site
at http://www.msha.gov/01-995/dieselerrorfactor.pdf, provides one way
of properly estimating analytical variability from the baseline paired
punches while accounting for such heterogeneity. This method was also
published as Appendix II of the 31-Mine Study (BKG-54-2) and as
Appendix 2 of MSHA's web document on the error factor (AB29-BKG-61,
cited as Ref. 4 by Borak/Sirianni).
To properly analyze the baseline paired punch data by the method of
MSHA's web document on the error factor, the square root of each punch
result ([mu]g/cm2) is first calculated. Next, we calculate
the difference between square roots within each pair and compute the
standard deviation of these differences. The result for these data is
an estimated SD of [sigma] = 0.175. Contrary to the Borak/Sirianni
conclusions, this is substantially less than the corresponding value,
[sigma][tau]=0.256, derived from EC analyses on 621 pairs of punches
obtained during the 31-Mine Study and published in MSHA's web document
on the error factor (Borak/Sirianni Ref. 4). Although Borak/
Sirianni stated that ``MSHA has not evaluated its proposed method by
means of systematic determinations of the CV for samples obtained under
real mining settings,'' their Ref. 4 contains such an
evaluation based on real mine data (621 pairs of punches) obtained
during the 31-Mine Study. The lower analytical variability exhibited in
these baseline paired punch data, as compared to the 31-Mine Study, is
not surprising, since, for the baseline samples, both punches within
each pair were analyzed by the same laboratory. For the 31-Mine Study,
this was not generally the case, so both intra- and inter-laboratory
variability are included in [sigma][tau].
As shown in MSHA's web document on the error factor, the analytical
CV for an individual punch result (X) at a specified loading ([mu]) is
[GRAPHIC] [TIFF OMITTED] TR06JN05.000
This quantity, which is plotted in Figure IX-2 using [sigma] = 0.256,
must be further divided by [radic]2 to specify analytical imprecision
for a 2-punch average, as in the value of CVA cited by
Borak/Sirianni. Therefore, at an EC loading of [mu] = 10 [mu]g/
cm2, the estimated analytical error CV for a 2-punch average
is 8.1% using [sigma] = 0.256 (as in MSHA's web document on the error
factor) or 5.5% using [sigma] = 0.175 (based on the baseline paired-
punch data). For simplicity, the effect of applying a blank adjustment
(by means of a control filter) has been left out of these calculations.
However, the formula for CVA provided in MSHA's web document
(AB29-BKG-61) does account for the effect of a blank adjustment on
31-Mine Study Subset
The third body of data examined in the Borak/Sirianni analysis
consisted of 63 pairs of EC results extracted from the 31-Mine Study.
As in the baseline paired punches, each pair consisted of the results
for two punches taken from the same sample filter. Each analytical EC
punch result was converted to a blank-adjusted EC concentration ([mu]g/
m3) and multiplied by 1.3.
No explanation was provided as to why these particular 63 pairs
were included in the Borak/Sirianni analysis while about 750 other
paired punch results available from the 31-Mine Study were excluded.
However, by examining the identification numbers of the 63 samples
included, MSHA determined that they included 52 samples collected from
the three trona mines involved in the 31-Mine Study, along with 11
samples collected from one of the lead/zinc mines. All 63 of these
samples had one of the punches acidified so that the effects of such
acidification could be evaluated. But this was apparently not the only
inclusion criterion, since the Borak/Sirianni analysis excluded
approximately 150 other paired-punch samples in which one of the
punches was acidified. Acidification is the process by which carbonates
(CaCO3) are chemically removed from a DPM sample prior to
the Method 5040 analysis. The collected DPM filter is exposed to
hydrochloric (HCl) acid vapors. The chlorine combines with the calcium;
carbon dioxide and water are evolved from the sample. Results from the
31-Mine Study showed that the submicron impactor successfully removed
the carbonate minerals from the sample, and that acidification was not
required prior to the analysis.
MSHA based its statistical analysis of EC analytical precision
(AB29-BKG-61) on all 621 paired-punch samples from the 31-Mine Study
for which (1) valid analytical results were available on both punches
and (2) both punches had received identical treatment with respect to
acidification. Since all 63 samples included in the Borak/Sirianni
analysis had one punch acidified and the other not acidified, they,
along with approximately 150 other such samples were excluded from
MSHA's statistical analysis of analytical precision.
The Borak/Sirianni method of analyzing these data was, with one
notable exception, identical to the method they used for the baseline
paired punches. As in their statistical analysis of the baseline paired
punches, they tabulated, for these 63 samples, the frequency of cases
in which the ``percentage difference'' fell into three categories: 0-
4.99%, 5-9.99%, and >=10%. The only methodological difference was that,
for these data, the percentage difference was always calculated
relative to the lower of the two punch results within each pair. Borak/
Sirianni provided no explanation or justification for why they
rearranged the data within each pair so that the lower value always
appears as ``Punch A'' and thus forms the denominator in their
calculation of percentage difference.
The Borak/Sirianni analysis reached the same conclusion with
respect to this dataset as with the baseline paired punches: that ``it
is almost certain'' that these data ``document failure to meet the
NIOSH and MSHA acceptability criteria.'' Likewise, since they used
essentially the same statistical method, the authors reproduced the
same five fallacies described earlier in connection with the baseline
paired punches. There are, however, at least three more reasons why the
Borak/Sirianni analysis of this particular dataset is invalid, in
addition to points 1-5 above:
6. One of the punches in each pair was acidified, and the other was
not. Therefore, differences in the analytical results within pairs
confound analytical variability with the potential effects of
acidification and differential handling. For this reason, these 63
samples (along with all others that were similarly treated) were
excluded from MSHA's paired-punch analysis of analytical variability
7. Fifty of the 63 Punch A results (79%) fell below 10 [mu]g/
cm2 and 33 of them (52%) fell below 5 [mu]g/cm2.
As shown in Figure 2, EC loadings below 5 [mu]g/cm2 exhibit
substantially greater analytical variability than loadings
corresponding to EC concentration limits anticipated in the second
partial settlement agreement. Indeed, results for the three samples
showing the greatest ``percentage difference'' all fell below the
minimum value (2 [mu]g/cm2) normally reported by a
laboratory EC analysis.
8. In addition to the bias explained under point 4 above, the
Borak/Sirianni calculation of ``percentage difference'' was further
biased by rearranging the data within each pair so that the ``Punch A''
result (X1) is always less than ``Punch B'' (X2).
If the Punch A and B designations (as provided in the original 31-Mine
Study spreadsheet) had been left unchanged, then the ``percentage
difference'' would sometimes have been calculated relative to the lower
value and sometimes relative to the higher, as in the Borak/Sirianni
analysis of the baseline paired punches. In their analysis of the 31-
Mine Study subset, however, the lower of the two values always forms
the denominator for the ``percentage difference.'' This yields
systematically higher percentages than a denominator equal to the
average of the two punches.
The sample identified as SKC-1D-166 illustrates the impact of
points 7 and 8 on the Borak/Sirianni analysis and conclusions. In the
original spreadsheet, the EC results for Punch A and B, prior to any
blank adjustment, were 0.92 [mu]g/cm2 and 0.76 [mu]g/
cm2. Under normal procedures, EC values this low would not
even be reported by the laboratory. However, the percentage difference,
relative to the average of these two values, is 9.5%. A percentage
difference of this magnitude is inconsequential, given that the mean EC
loading is only 0.84 [mu]g/cm2. In the Borak/Sirianni
analysis, however, a blank adjustment of 0.58 [mu]g/cm2 was
applied to both punch results, yielding adjusted values of 0.34 and
0.18 [mu]g/cm2. The punch A and B designations were then
switched, and the percentage difference was calculated relative to the
lower value, yielding a reported 89% difference. (If the punch A and
punch B designations had not been switched, then Borak/Sirianni would
presumably have reported the ``percentage difference'' as 47%.) Thus,
the reported percentage difference is mostly an artifact of applying
the blank adjustment to such small EC loadings and of calculating the
percentage relative to the lower value.
Despite the additional potential variability attributable to
differential handling of the punches, punch-to-punch variability in
this dataset appears to be well within acceptable limits when the EC
loadings are taken into account. The estimated value of [sigma]
calculated for these 63 data pairs by the method of MSHA's web document
on the error factor is 0.090. This is substantially lower than the
corresponding value ([sigma][b.tau] = 0.256) used in the
calculation of CVA for the average of two blank-adjusted
punches as described in MSHA's web document (AB29-BKG-61). Therefore,
contrary to the Borak/Sirianni assessment, this dataset exhibits less
variability than what MSHA has assumed in determining an appropriate
error factor. MSHA believes that this data, when analyzed correctly,
verifies that the sampling and analytical method meet the NIOSH
B. Section 57.5060(c)
Section 57.5060(c) of the 2001 final rule allows mine operators to
apply to the Secretary for additional time to meet the final
concentration limit of 160TC [mu]g/m3 of air.
Operators are allowed only one special extension per mine, which cannot
exceed a period of two years. The rule also contains certification and
posting requirements and requires operators to provide a copy of the
approved application to the authorized representative of miners. The
rule, however, does not apply to the interim concentration limit.
In the DPM settlement agreement, MSHA agreed to adapt this
provision to apply it to the interim EC limit, include consideration of
economic feasibility, and allow for annual renewals of special
extensions. MSHA proposed to revise the standard pursuant to the terms
of the settlement agreement.
Unlike the 2003 NPRM, final Sec. 57.5060(c)(1) does not expand the
scope of the provision to the interim PEL. Instead, MSHA has decided to
retain the scope of the 2001 final rule so that a special extension
applies solely to the final concentration limit. MSHA believes that the
feasibility data in the rulemaking record does not justify providing
for an extension of time in which to comply with the interim PEL. MSHA
found that the baseline sampling results project that 63% of miners
sampled were not overexposed to the interim DPM limit. In the 2001
final rule, MSHA intended that this provision apply to mine operators
who needed more time to implement technological solutions to control
DPM in their individual mines. Also, MSHA wanted to give mine operators
some flexibility where the regulatory scheme prohibited administrative
controls and respiratory protection. Under this final rule, MSHA has
included its traditional hierarchy of controls. The test for
determining if an individual operator has implemented all feasible
controls is very similar to that for qualifying for a special extension
absent burdensome paperwork requirements.
MSHA believes that by incorporating the hierarchy of controls
approach, this final rule addresses the primary concern expressed by
industry commenters who supported special extensions: that compliance
with the interim DPM limit using engineering and administrative
controls alone is not feasible for each individual operator's
circumstances. MSHA, however, has decided to retain the 2001
requirement, as revised, for the final concentration limit. At this
time, the DPM rulemaking record does not contain sufficient information
to delete the requirement as it applies to the final limit.
In final Sec. 57.5060(c)(1), MSHA will consider both economic and
technological feasibility when determining whether operators qualify
for a special extension for the final concentration limit. MSHA
believes that both technological and economic feasibility must be
assessed on a case-by-case basis. Therefore, mine operators will have
an opportunity to demonstrate to MSHA that there is no cost-effective
solution to reducing a miner's exposure to DPM.
Section 57.5060(c)(1) also authorizes the MSHA District Manager,
rather than the Secretary, to approve special extensions to the final
concentration limit. MSHA believes that the district managers have
extensive knowledge of the specific conditions and circumstances that
exist at mines within their regions. Consequently, MSHA has determined
that they are the appropriate entity to assess technical and economic
feasibility issues at mines. In unusual or particularly complex
circumstances, district staff may be assisted by personnel from MSHA's
Directorate of Technical Support.
When determining whether to grant a special extension for complying
with the final concentration limit, MSHA will apply the criteria of the
standard. MSHA will conduct an analysis of the circumstances at a
mining operation to determine whether the mine operator has exhausted
all feasible engineering and administrative controls before using
respiratory protection to supplement controls. A mine operator's
application for an extension must include information that explains why
the operator believes engineering and administrative controls
sufficient to achieve compliance with the applicable limit are
economically and/or technologically infeasible. The application also
must include the most recent DPM monitoring results, and specify the
actions the operator intends to take during the extension period to
minimize miners' exposures to DPM, such as monitoring, ordering
controls, adjusting ventilation, respiratory protection, and other good
faith actions of the mine operator. The circumstances under which MSHA
requires respiratory protection are in this final Sec. 57.5060(d). In
order for MSHA to approve an application for a special extension, MSHA
will evaluate whether the mine operator has utilized all feasible
controls. Such an evaluation will involve consideration of numerous
factors including the specific mining conditions, type of mining
equipment used, nature of the overexposure, controls used by the mine
operator, and MSHA policy and case law governing the economic and
technological feasibility of controls. Comprehensive discussion
regarding economic and technological feasibility, and enforcement of
feasible controls is included elsewhere in this preamble.
Where an extension is granted, overexposed miners will be required
to wear respiratory protection under a respiratory protection program
as specified in Sec. 57.5060(d). As MSHA stated in the preamble to the
2003 NPRM, it does not intend for PPE to be permitted during an
extension period as a substitute for feasible engineering and
administrative controls. Rather, MSHA will require mine operators to
implement all feasible engineering and administrative controls to
reduce exposures to the applicable limit, or if that is not possible,
to the lowest level feasible. Once these controls are implemented, MSHA
will consider whether to grant the extension. During the period of the
extension, the mine operator will be required to maintain these
engineering and administrative controls, along with implementation of a
respiratory protection program fully compliant with ANSI Z88.2-1969 for
all miners whose exposure to DPM continues to exceed the applicable DPM
Like the 2003 NPRM, Sec. 57.5060(c)(2) of the final rule retains
the requirement for the mine operator to certify that one copy of the
application was posted at the mine site for at least 30 days prior to
the date of application, and another copy was provided to the
authorized representative of miners. It is the agency's position that
such advance notification provides miners with the opportunity to
provide comments to the District Manager regarding the information
provided by the mine operator in the application. This record also is
subject to access to records requirements under Sec. 57.5075 of the
2001 final rule.
One commenter questioned the need for the requirement under Sec.
57.5060(c)(2) to provide advance notification to a miners'
representative when a mine operator is going to submit an application
for a special extension. This commenter suggested instead that it is
sufficient to give a copy to the miner's representative at the time the
application is submitted. MSHA disagrees for the above reasons.
Final Sec. 57.5060(c)(3) limits each special extension to a period
of one year from the date of approval, and removes the limit on the
number of special extensions that may be granted to each mine. MSHA's
determination is based on limited data in the rulemaking record at this
time to conclude that mine operators feasibly can meet the final DPM
MSHA also considered longer durations for special extensions. MSHA
acknowledges that durations longer than one year would reduce the
paperwork burden on mine operators. However, MSHA rejected the concept,
since MSHA has observed rapid progress in the development of improved
DPM control technology since 2001. Moreover, introduction of new mining
equipment models increasingly include features aimed at better reducing
DPM exposures, such as cleaner engines and better environmental cabs.
It is not MSHA's intent to allow mine operators to use respiratory
protection for extended periods of time where controls are feasible.
Other commenters who supported the proposed changes to Sec.
57.5060(c) wanted the criteria used for granting or denying a special
extension to be communicated clearly and unambiguously to the mining
industry in the body of the standard. Moreover, these commenters wanted
MSHA to give a mine operator an extension if the operator meets the
criteria under this standard.
Given that each mine has unique circumstances affecting economic or
technological feasibility to comply with the DPM standard, MSHA chose
to include generic criteria in the standard for mine operators to
develop and for MSHA to consider in granting extensions.
Final Sec. 57.5060(c)(4) requires mine operators to comply with
the terms of an approved application for a special extension. This
provision also requires mine operators to post a copy of the approved
application at the mine site for the duration of the extension, and
provide a copy to the authorized representative of the miners.
One commenter stated that posting a copy of the application on the
mine bulletin board for the duration of the extension is excessive. As
an alternative, this commenter suggested posting the application for a
sufficient time for miners to view it. MSHA believes that miners and
their representatives should have the right to review the approved
special extension at the mine site for the duration of its
effectiveness. Consequently, MSHA has retained the posting requirement
in this final rule.
MSHA requested comments on whether proposed Sec. 57.5060(c) would
be necessary in light of MSHA's recommendations to prescribe use of
feasible engineering and administrative controls supplemented by
respiratory protection. MSHA also requested that the public give
examples of how this requirement would benefit mine operators if it
were included in the final regulatory framework. MSHA stated in the
preamble to the 2003 NPRM that it was interested in avoiding
duplication and increased paperwork for the mining industry to resolve
feasibility issues at individual mining operations. Therefore, MSHA was
seeking further input from the public on the need for proposed Sec.
57.5060(c) and how this provision fits within the comprehensive
structure of the current rulemaking.
With respect to the interim limit, MSHA agrees with the commenter
who observed that MSHA routinely handles compliance problems that are
due to circumstances beyond the control of the mine operator without
special extensions, and that therefore, if these same procedures are
followed with respect to DPM, special extensions of the interim DPM
limit are not justified. The commenter's other suggestion that
remaining issues regarding special extensions be deferred until
rulemaking begins on the final DPM limit will be considered by MSHA at
that time. Until then, provisions relating to special extensions to the
final DPM limit have been retained in this final rule.
MSHA apprised the mining community in the proposed preamble of its
concerns over whether a special extension is necessary given the
changes to the methods of compliance in the new final rule. MSHA
believes that these revisions accomplish the same objective as a
special extension, but without the associated paperwork and
recordkeeping. MSHA explained that it believed special extensions were
appropriate in the context of the original 2001 final rule, because it
prohibited respiratory protection and administrative controls as means
of compliance. The 2001 final rule would have required mine operators
to comply with the applicable DPM limit using only engineering and work
practice controls. Respiratory protection and administrative controls
(defined uniquely as job rotation) were expressly prohibited as means
Numerous comments to the 2003 NPRM were received concerning this
provision. Several commenters supported the proposed changes to Sec.
57.5060(c). Some other commenters supported the proposed changes, but
suggested that an appeals process should be specified so a mine that is
denied a special extension by the District Manager could appeal that
decision to a higher authority. Several commenters who supported the
addition of an appeals process suggested that a time limit of 30 days
be imposed on the District Manager to determine whether to grant a
special extension. In addition, they suggested that an additional 60
days be provided for an appeal if the District Manager does not grant
the special extension. MSHA believes that the Mine Act currently
affords mine operators adequate due process rights to a hearing on the
merits before an administrative law judge (ALJ) of the independent
Commission. If an operator disagrees with the ALJ's decision, the
operator may request an appeal before the Commission, which is composed
of five independent commissioners. Any person adversely affected by a
determination of the Commission may obtain review from a U.S. court of
appeals for the applicable circuit. For the foregoing reasons, MSHA
sees no reasonable basis for creating parallel procedures to accomplish
the same objective as existing procedures.
One of the commenters suggested that MSHA grant extensions prior to
issuance of a citation for an overexposure to DPM, rather than using
the citation as the triggering event that initiates the special
extension process. Under the final provision, a citation does not need
to be issued before MSHA can grant an extension. MSHA, however, must
assess feasibility of compliance before granting an extension or
denying an application for an extension. If MSHA finds a miner
overexposed to DPM and the mine operator does not comply with all
aspects of Sec. 57.5060(d), MSHA will cite the operator for
Several comments were received that were opposed to any form of
special extension or any mechanism by which mine operators could delay
compliance with the applicable DPM limits using exclusively engineering
or work practice controls. Commenters who opposed special extensions
stated that MSHA lacks evidence to substantiate the need for expanding
the scope of the special extension provision to include the interim limit.
These commenters believe that the rulemaking record adequately documents
feasibility of the mining industry, as a whole, to comply with the DPM limits.
Commenters noted that MSHA requested examples that substantiate this need,
but none were submitted by the mining industry. One commenter suggested
that just because some operators require technical help doesn't mean the rule is infeasible
for the industry as a whole. This commenter also noted that the
proposed changes to the special extension provision address both the
interim and final DPM limits, despite the fact that the preamble to the
2003 NPRM stated that MSHA, ``is only now seeking information about
whether the final limit needs to be changed.''
MSHA wishes to clarify that it proposed making changes to Sec.
57.5060(c) that would have applied special extensions to both the
interim and final DPM limits. MSHA strongly agrees that the mining
industry, as a whole, can comply with the interim PEL. Also, the 31-
Mine Study, baseline sampling results, compliance assistance visits,
and MSHA's current experience with enforcing a comparable interim limit
all sustain MSHA's determination regarding the interim PEL. MSHA,
however, does not have adequate evidence at this time to delete the
special extension requirement for the final concentration limit.
Commenters opposed to special extensions also expressed that the
proposed changes to the special extension provision are less protective
than the existing provision because respirators could be substituted
for more protective engineering and work practice controls. These
commenters stated further that such action violates the Mine Act
requirement in Section 101(a)(6)(a) that such rules attain the highest
degree of protection for miners, with feasibility as a consideration.
Since these commenters believe feasible engineering and work practice
controls exist for the industry as a whole to comply with the
applicable DPM limits, they reasoned that a provision permitting
compliance by respirators would constitute a diminution of protection
to miners. MSHA disagrees. Nowhere does this final rule allow
respiratory protection in lieu of feasible engineering and
administrative controls. If anything, MSHA has provided greater
protection for miners by allowing prompt usage of supplemental
protection for miners when feasible controls have been exhausted.
C. Sections 57.5060(d) and 57.5060(e)
Section 57.5060(d) of the 2001 final rule permits miners engaged in
specific activities involving inspection, maintenance, or repair
activities to work in concentrations of DPM that exceed the interim and
final limits, with advance approval from the Secretary. MSHA specifies
in the standard that advance approval is limited to activities
conducted as follows:
(i) For inspection, maintenance or repair activities to be
(A) In areas where miners work or travel infrequently or for
brief periods of time;
(B) In areas where miners otherwise work exclusively inside of
enclosed and environmentally controlled cabs, booths and similar
structures with filtered breathing air; or
(C) In shafts, inclines, slopes, adits, tunnels and similar
workings that the operator designates as return or exhaust air
courses and that miners use for access into the mine or egress from
Operators must meet the conditions set forth in the standard for
protecting miners when they engage in the specified activities in order
to qualify for approval of the Secretary to use respiratory protection
and work practices. MSHA considers work practices a component of
In tandem with this requirement is Sec. 57.5060(e) of the 2001
final rule which prohibits use of respiratory protection to comply with
the concentration limits, except as specified in an approved extension
under Sec. 57.5060(c), and then, only for activities related to
inspection, repair, or maintenance activities. Additionally, Section
57.5060(f) of the 2001 final rule prohibits use of administrative
controls to comply with the concentration limits. On July 18, 2002,
MSHA stayed Sec. Sec. 57.5060(d), (e) and (f) of the 2001 final rule
(67 FR 47296) pending completion of their revisions in this final
Pursuant to the DPM settlement agreement, MSHA proposed to adopt
the same hierarchy of controls as required in MSHA's other exposure-
based health standards for M/NM mines, and considered requiring
application to the Secretary before respirators could be used to comply
with the DPM standard. MSHA further specified that employee rotation
would not be allowed as an administrative control for compliance with
As proposed, the new final rule on the interim limit requires that
when a miner's exposure exceeds the PEL, operators must reduce the
miner's exposure by installing, using and maintaining feasible
engineering and administrative controls; except operators are
prohibited from rotating a miner to meet the DPM limits. When controls
do not reduce a miner's exposure to the DPM limits, controls are
infeasible, or controls do not produce significant reductions in DPM
exposures, operators must continue to use all feasible controls and
supplement them with a respiratory protection program, the details of
which are discussed below in this preamble. The new final rule does not
include requirements for written administrative control procedures,
written respiratory protection programs, medical examinations of
respirator wearers or transfer of miners unable to wear respirators.
Additionally, the new final rule deletes Sec. 57.5060(e), prohibiting
respiratory protection as a method of compliance with the DPM rule, and
Sec. 57.5060(f), prohibiting the use of administrative controls for
compliance with the 2001 final rule.
The new final rule does not give preference to engineering controls
over administrative controls. MSHA will require all feasible controls,
of both types if necessary, to be implemented to reduce a miner's
exposure to DPM. Employee rotation, however, is not permitted as an
administrative control under this standard. Under the new final rule,
mine operators have a choice of which control method they will use
first. MSHA intended for mine operators to have the flexibility to
choose to start with engineering or administrative controls, or a
combination of both, for the control method that best suits their
MSHA, however, believes that engineering controls should be
included in the first tier of any control method for protecting miners
against exposure to airborne contaminants. Engineering controls provide
a permanent method of modifying the exposure source, or they modify the
environment of the exposed miner. As a result, they decrease the
miner's exposure to hazardous levels of DPM. Moreover, engineering
controls are more consistent and reliable protection for miners. The
effectiveness of engineering controls can be readily determined and
assessed. Routine maintenance of engineering controls provides greater
In the 2001 final rule, MSHA uniquely defined administrative
controls as ``worker rotation.'' MSHA historically has considered other
types of controls, besides worker rotation, to be administrative
controls, including work practice controls which MSHA permits under
this new final rule.
Work practice controls are changes in the manner work tasks are
performed in order to reduce or eliminate a hazard. MSHA strongly believes that
these types of administrative controls do not compromise miners' health
and safety and do not reduce the level of protection provided miners
under the existing final rule. Moreover, mine operators should be given
the flexibility to choose to start with either engineering or
administrative controls, or a combination of both, for the control
method best suited for their mines. Some examples of work practice
controls include: Minimizing engine idling; limiting number of diesel-
powered equipment operating in an area; reducing or limiting engine
horsepower; hauling upgrade in exhaust drifts rather than in intake;
and limiting the number of persons working in high exposure areas.
MSHA's regulatory scheme for its hierarchy of controls is based on
its current enforcement policy for its airborne contaminants which are
included in MSHA's M/NM air quality standards (30 CFR 56/
57.5001-.5006). Under these standards, MSHA requires mine operators to
abate a citation for an overexposure to airborne contaminants by using
feasible engineering and administrative controls to reduce the miner's
exposure to the contaminant's exposure limit. Respiratory protection is
required to supplement feasible controls that do not reduce a miner's
exposure to the permissible level. The air quality standards do not
contain a requirement for mine operators to develop written
administrative control procedures, nor does MSHA's enforcement policy
require a written respiratory protection program. (See MSHA Program
Policy Manual, Volume IV, Parts 56 and 57, Subpart D, Sec. Sec. .5001
and .5005, August 30, 1990).
Some commenters opposed changing the control method from that of
the 2001 final rule, while others supported removing the prohibition on
administrative controls and respirators in order to have greater
compliance flexibility. MSHA agrees that operators should be afforded
greater flexibility of compliance where such modifications to the DPM
standard do not compromise or lower miners' health protection from that
provided under the 2001 final rule. Additionally, miners should be
afforded the added protection of respirators when engineering and
administrative controls are not feasible, cannot reduce DPM exposures
to within permissible limits, or cannot achieve significant reduction
in DPM levels.
MSHA evaluated the potential consequences of relying on the
hierarchy of controls in the final rule. MSHA also examined different
control methods but abandoned them since they were less protective than
those in the 2001 final rule. These approaches included allowing
rotation of miners, and respiratory protection upon application to the
Secretary of Labor. MSHA also examined giving preference for
engineering controls as a first resort with a lesser role for
administrative controls, including work practices. Though some of these
approaches would save money for the mining industry, MSHA found that
they either could be less protective or, in some cases, too restrictive
for the mining industry in complying with the DPM rule. There is also
insufficient scientific evidence in the rulemaking record to justify
some of these changes for controlling exposure to a potential human
carcinogen. For example, allowing worker rotation would increase the
number of persons exposed to a potential carcinogen and thereby
increase the number of individuals at risk.
Commenters suggested that MSHA lacks legal justification for its
hierarchy of controls and reliance on other MSHA rules does not justify
this approach. Many commenters believe that MSHA should allow mine
operators to use respiratory protection on an equal footing with
engineering and administrative controls. In fact, some commenters
believe that respiratory protection is an engineering control. MSHA
disagrees. MSHA believes that it has adopted an approach that is
supported by the best available evidence and sustains the standard
industrial hygiene practice to rely first upon engineering and
administrative controls to reduce a person's exposure to hazardous
Throughout this rulemaking, MSHA has asked the mining community for
their views on the appropriate role for administrative controls, and
whether it would be necessary for MSHA to require written
administrative procedures. In response to the 2003 NPRM, the mining
industry strongly objected to written administrative procedures.
Commenters stated that such a requirement would increase compliance
costs and reduce efficiency and personnel availability. Organized labor
recommended that MSHA require operators to have written administrative
control strategies and post them on the mine's bulletin board.
MSHA's M/NM air quality standards do not require that
administrative controls be in writing. However, written administrative
controls are required under MSHA's more recently promulgated noise
standard at 30 CFR part 62. Although the 2001 final rule specifically
prohibits the use of administrative controls, it does not prohibit
other types of work practices which MSHA considers to be administrative
controls. The 2001 final rule does not include a requirement that mine
operators develop a written work practice control strategy when using
such controls to achieve compliance with the PEL, however, MSHA
recommends it as a good industrial hygiene practice. MSHA is relying
upon its current experience under the air quality standards that do not
include written administrative control procedures. Thus far, the lack
of these written procedures has not hindered MSHA's effective
enforcement of its air quality standards. Where possible, MSHA is
avoiding additional paperwork burdens under the final DPM rule.
MSHA also proposed to prohibit rotation of miners as an
administrative control to comply with the final DPM rule. Most
commenters requested that job rotation be allowed because it is a low
cost control method and it increases management flexibility to achieve
compliance. These commenters, however, offered no scientific evidence
in support of their position. Organized labor and some other commenters
opposed allowing worker rotation. They stated that rotation may reduce
the risk to an individual miner, but it will not necessarily reduce the
overall risk to the population of miners; also, depending on the shape
of the dose response curve, it may actually increase the population
risk, resulting in more cancer overall.
As stated earlier, the 2001 risk assessment upon which this rule is
based classifies DPM as a probable human carcinogen. The majority of
scientific data for regulating exposures to carcinogens supports that
job rotation is an unacceptable method for controlling exposure to both
known and probable human carcinogens because it increases the number of
persons exposed. Recent OSHA chemical-specific regulations for both
known human carcinogens and probable human carcinogens prohibit job
rotation as a means of compliance. Examples include the OSHA standards
for asbestos, butadiene, and ethylene oxide, which are known human
carcinogens (based on the CDC National Toxicology Program (NTP) Report
on Carcinogens for 2002 (Report on Carcinogens, Tenth Edition; U.S.
Department of Health and Human Services, Public Health Service,
National Toxicology Program, December 2002.)), and OSHA standards for
methylenedianiline at 29 CFR Sec. 1910.1050 and methylene chloride,
(29 CFR Sec. 1910.1052), which are reasonably anticipated to be human
carcinogens (based on the same NTP report). DPM also appears on the NTP listing
of chemicals that are reasonably anticipated to be human carcinogens.
Therefore, based on the scientific data in the DPM rulemaking record,
final Sec. 57.5060(e) retains the prohibition on the rotation of miners as an
administrative control used for compliance with this the DPM rule.
Engineering controls are intended to refer to controls that remove
the DPM hazard by applying such methods as modification, substitution,
isolation, enclosure, and ventilation. MSHA would consider a control to
be effective in reducing DPM exposure if credible scientific or
engineering studies conclude that a control will achieve a significant
reduction in exposure. Additionally, MSHA will consider a control to be
effective if MSHA finds that similar diesel equipment operating under
similar conditions has demonstrated that the equipment is capable of
significantly reducing exposures. These significant reductions may be
achieved either by a single control, or in combination with other
controls, and in either laboratory or field trials. MSHA believes that
a 25% or greater reduction in DPM exposure is significant. MSHA
discusses this issue in more detail in the Feasibility section of this
MSHA considers certain traditional methods for control of exposure
to airborne contaminants to be technologically feasible for controlling
exposures to DPM, such as improved ventilation (main and/or auxiliary)
and enclosed cabs with filtered breathing air. Improving ventilation
may involve upgrading main fans, use of booster fans, and use of
auxiliary fans that may or may not be connected to flexible or rigid
ventilation duct, as well as installation of ventilation control
structures such as air walls, stoppings, brattices, doors, and
regulators. At most mines, cabs with filtered breathing air are
technologically feasible for many newer model trucks, loaders, scalers,
drills, and other similar equipment. However, use of enclosed cabs with
filtered breathing air may not be feasible as a retrofit to certain
older equipment or where the function performed by miners using a
particular piece of equipment is inconsistent with any type of cab
(e.g., loading blastholes from a powder truck, installing utilities
from a scissors-lift truck) or where the height of the mine roof is
insufficient for cab clearance. Other examples of effective DPM
engineering controls that MSHA would consider to be technologically
feasible include: DPM exhaust filters; certain alternative fuels; fuel
blends; fuel additives; fuel pre-treatment devices; and replacement of
older, high-emission engines with modern, low-emission engines.
MSHA asked for comments on the appropriate role for respiratory
protection in controlling DPM exposure. Although commenters disagree on
the types of restrictions that MSHA should place on their use, most
commenters indicated that respirators with some restriction on their
use should be permitted as a means of compliance with the DPM limits.
Some commenters believe MSHA DPM regulations should conform verbatim to
the current respirator requirements in MSHA's air quality standards at
30 CFR 57.5005. Other commenters felt that the only change MSHA should
make to the existing requirements for respirator use in 30 CFR 57.5005,
would be to add requirements for filters. Comments were received from
those who believe that PPE such as respiratory protection may be far
more effective in protecting miners from suspected DPM health effects
than any available and feasible engineering control technology.
Other commenters suggested MSHA model its respirator program after
OSHA's generic standard for respiratory protection at 29 CFR 1910.134.
One commenter said that routine use of respirators for any normal
production job or activity should be allowed only under a special
extension and only for the final exposure limit, or where controls are
in the process of being installed. They and other commenters also said
that respirators are hard to tolerate under the best of conditions, and
that a 10-minute break should be allowed every two hours, so the miner
can remove the respirator in clean air. Another commenter requested
that respirators not be used for the purpose of determining compliance.
Some of the objections to the use of respirators that were given by
commenters are: Respirators leak, interfere with communication,
increase the work of breathing, and are stressful; instead of creating
one system to protect all workers, use of respirators creates one
system per worker, each of which needs maintenance; some workers cannot
wear respirators for a variety of reasons; and routine use of
respirators breeds carelessness.
MSHA agrees that respiratory protection does not provide comparable
protection to that of engineering and administrative controls.
Therefore, the new final rule only requires respiratory protection as a
supplement to feasible engineering and administrative controls. When
controls do not reduce a miner's DPM exposure to the limit, controls
are infeasible, or controls do not produce significant reductions in
DPM exposures, then controls must be used to reduce the miner's
exposure to as low a level as feasible and be supplemented with
respiratory protection in accordance with 30 CFR 57.5005(a), (b), and
30 CFR 57.5060(d)(1) and (d)(2).
Based on observations and experience in underground M/NM mines,
MSHA continues to believe that feasible engineering and administrative
controls exist to adequately address most overexposures to the interim
DPM limit. However, MSHA is not persuaded that all DPM overexposures
can be eliminated through implementation of feasible engineering and
administrative controls alone. Extra protective measures such as those
afforded by respiratory protection must be taken to protect miners in
such circumstances. Therefore, MSHA's final Sec. 57.5060(d) conforms
to the current respirator requirements in MSHA's air quality standards
in Sec. 57.5005, with the addition that the types of filters
appropriate for protection from DPM are specified.
Type of Respiratory Protection
In the 2003 NPRM, MSHA proposed that filters for air purifying
respirators, used to comply with the DPM limits, be certified in
accordance with 30 CFR part 11 as a high efficiency particulate air
(HEPA) filter; certified per 42 CFR part 84 as 99.97% efficient; or,
certified by NIOSH for DPM. Additionally, the 2003 NPRM would have
required that non-powered, negative-pressure, air purifying,
particulate-filter respirators use an R-or P-series filter or any
filter certified by NIOSH for DPM. It also specified that R-series
filters not be used for longer than one work shift.
MSHA requested comments on the type of respirators that would be
suitable for protection against DPM. Some commenters suggested that
various commercially available respirators, including those with
filtering facepieces, were suitable for protection against particles
smaller than DPM, and would therefore be suitable for DPM as well.
NIOSH recommended that respirators used for protection against DPM have
an R-100 or P-100 certification per 42 CFR part 84. NIOSH also
recommended against using N-rated respirators since diesel exhaust
contains oil, and aerosols containing oil can degrade the performance
of N-rated filters.
As some commenters suggested, MSHA is adhering to the provisions
for respiratory protection afforded in accordance with Sec. 57.5005(a)
and (b). However, Sec. 57.5005(a) requires that respirators approved
by NIOSH under 42 CFR part 84 which are applicable and suitable for the purpose
intended be furnished and miners use the protective equipment in
accordance with training and instruction. Currently, there is no non-
powered, negative-pressure, air purifying, particulate-filter
respirator certified by NIOSH as appropriate for protection from DPM.
In order to protect miners from DPM exposure, MSHA is adopting the
NIOSH recommendation that respirators be NIOSH certified per 42 CFR
part 84 as a high-efficiency particulate air (HEPA) filter, certified
per 30 CFR part 11 as 99.97% efficient, or certified by NIOSH for DPM.
MSHA is technology-forcing in its rulemaking, and therefore, addressed
the likelihood that a respirator may be approved in the future by NIOSH
for DPM. MSHA is also adopting the NIOSH recommendation that filters
used in non-powered, negative-pressure, air purifying respirators be
either R- or P-series.
In MSHA PPL No. P03-IV-1, effective August 8, 2003, MSHA addressed
the question of whether a powered air-purifying respirator (PAPR) could
provide suitable respiratory protection from DPM. MSHA stated, ``Yes,
if the PAPR is equipped with filters that meet one of the following
Certified by NIOSH under 30 CFR part 11 as high efficiency
particulate air (HEPA) filter;
Certified by NIOSH under 42 CFR part 84 as 99.97%
Certified by NIOSH for DPM.''
This holds true for compliance with final Sec. 57.5060, and MSHA's
position will be reiterated in MSHA's compliance guide for the new
final rule. MSHA believes that most workers who are medically unable to
use a negative pressure respirator will be able to use a PAPR, which
offers considerably less breathing resistance than a negative pressure
respirator. Employees who cannot use a negative pressure respirator
could be provided with a less physiologically burdensome respirator
that will enable them to continue in their jobs protected against DPM
NIOSH also recommended that combination filters capable of removing
both particulates and organic vapor be specified, since organic vapors
and gases can be adsorbed onto DPM. MSHA, however, does not have data
substantiating that a DPM overexposure would necessarily indicate an
associated overexposure to organic vapors. Therefore, the final rule
does not require respirators to be certified for organic vapor. If
simultaneous sampling for DPM and organic vapors indicate overexposure
to both contaminants, any subsequent citation(s) relating to the
overexposures would require that respirators be used and equipped with
a filter or combination of filters rated for both DPM and organic
Based on the above comments and discussion, MSHA's final rule on
the interim limit requires that when respirators are used for
compliance with the DPM limits, that air purifying respirators be
equipped with either:
(i) Filters certified by NIOSH under 30 CFR part 11 as a high
efficiency particulate air (HEPA) filter;
(ii) Filters certified by NIOSH under 42 CFR part 84 as 99.97%
(iii) Filters certified by NIOSH for DPM.
Additionally, when non-powered, negative-pressure, air purifying,
particulate-filter respirators are used for compliance, the final rule
requires the use of an R- or P-series filter, or any filter certified
by NIOSH for DPM, and that an R-series filter not be used for longer
than one work shift.
Written Respiratory Protection Program. The 2003 NPRM recommended
that when respirators were used for compliance with the DPM limits,
their use be in accordance with MSHA Air Quality Standard, Sec.
57.5005(a), (b), and Sec. 57.5060(d)(1) and (d)(2). Section 57.5005(b)
incorporates by reference, ANSI Z88.2-1969, ``American National
Standards Practices for Respiratory Protection.'' ANSI 1969 contains
numerous recommended practices for the appropriate selection, use, and
maintenance of respirators. Included among these is a recommendation
that written standard operating procedures governing the selection and
use of respirators be established. MSHA's enforcement policy on its air
quality standards has focused on several of the key recommendations in
ANSI 1969, including fit testing, maintenance, and cleaning of
respirators. MSHA's policy, however, is silent regarding the ANSI
recommendation on written standard operating procedures. Accordingly,
under the 2003 NPRM, a written respirator program would not have been
In MSHA's 2003 NPRM, it asked the mining community to submit
further information for justifying a written respiratory protection
program, including cost data, benefits to miners' health, and projected
One commenter stated that it was wrong to create a respiratory
protection requirement that treats exposure to DPM differently than
other gaseous substances requiring the use of such protective means.
Another commenter stated that proposing changes to MSHA's respirator
standard creates multiple technical, scientific, medical, and economic
issues that must be closely examined from the perspective of MSHA's
statutory mandates. This commenter suggested that given the vast number
of issues involved, it would be inappropriate to consider respirator
standard changes in an ``expedited'' rulemaking limited to the DPM
standard. Other commenters also suggested that MSHA address any
additional respiratory protection requirements in a separate, generic
rulemaking applicable to all contaminants. Some commenters opposed a
written program because they believe the rule already carries too heavy
a paperwork burden.
Commenters supporting a requirement for a written respirator
program suggested that it is an essential element of a respiratory
protection plan and that MSHA's requirements for respiratory protection
should be modeled after OSHA's requirements in 29 CFR 1910.134.
MSHA agrees with commenters who believe that the final respiratory
protection provisions should be consistent with the current air quality
requirements. Therefore, MSHA has decided not to require that
respiratory protection programs be in writing in this final rule.
Medical Evaluation and Miner Transfer. The 2003 NPRM did not
include provisions addressing the medical evaluation of respirator
wearers or the transfer of miners unable to wear respirators due to
medical and psychological conditions. MSHA, however, asked for further
information from the public as to whether the final rule should include
requirements for medical examination and transfer. Commenters were
asked to submit cost implications of such a program.
In MSHA's 2003 NPRM, it discussed this issue at length and asked
commenters to provide their views for consideration in the final rule.
Moreover, MSHA included in this discussion its statutory authority to
promulgate, where appropriate, medical surveillance and transfer of
miner requirements to prevent miners from being exposed to health
hazards. The Mine Act provision addressing this issue is Section
101(a)(7) which states, in pertinent part:
Where appropriate, such mandatory standard shall also prescribe
suitable protective equipment and control or technological
procedures to be used in connection with such hazards and shall
provide for monitoring or measuring miner exposure at such locations
and intervals, and in such manner so as to assure the maximum protection
of miners. In addition, where appropriate, any such mandatory standard shall
prescribe the type and frequency of medical examinations or other tests which
shall be made available, by the operator at his cost, to miners exposed to such
hazards in order to most effectively determine whether the health of such miners is
adversely affected by such exposure. Where appropriate, the
mandatory standard shall provide that where a determination is made
that a miner may suffer material impairment of health or functional
capacity by reason of exposure to the hazard covered by such
mandatory standard, that miner shall be removed from such exposure
and reassigned. Any miner transferred as a result of such exposure
shall continue to receive compensation for such work at no less than
the regular rate of pay for miners in the classification such miner
held immediately prior to his transfer. In the event of the transfer
of a miner pursuant to the preceding sentence, increases in wages of
the transferred miner shall be based upon the new work
Currently, MSHA standards do not require medical transfer of M/NM
miners. Existing standards at 30 CFR 56/57.5005(b) for control of
miners' exposures to airborne contaminants require that mine operators
establish a respiratory protection program consistent with the ANSI
Z88.2-1969 ``American National Standard for Respiratory Protection''
which includes medical determinations for potential respirator wearers.
However, MSHA's air quality enforcement policy for M/NM mines is silent
regarding this recommendation. ANSI Z88.2-1969 also does not include
any recommendations regarding the transfer of persons unable to wear a
OSHA acknowledges within its current standards addressing
respiratory protection at 29 CFR 1910.134(e) that use of a respirator
may place a physiological burden on workers while using them. OSHA
requires employers to provide medical evaluations before an employee is
fit tested or required to use respiratory protection. Employers are
required to have a physician or other licensed health care professional
have the worker complete a questionnaire, or in the alternative,
conduct an initial medical examination in order to make the
determination. If the worker has a positive response to certain
specified questions, the employer must provide a follow-up medical
examination. The questionnaire is contained in the body of the OSHA
rule. The preamble to the OSHA final rule states:
Specific medical conditions can compromise an employee's ability
to tolerate the physiological burdens imposed by respirator use,
thereby placing the employee at increased risk of illness, injury,
and even death (Exs. 64-363, 64-427). These medical conditions
include cardiovascular and respiratory diseases (e.g., a history of
high blood pressure, angina, heart attack, cardiac arrhythmias,
stroke, asthma, chronic bronchitis, emphysema), reduced pulmonary
function caused by other factors (e.g., smoking or prior exposure to
respiratory hazards), neurological or musculoskeletal disorders
(e.g., ringing in the ears, epilepsy, lower back pain), and impaired
sensory function (e.g., a perforated ear drum, reduced olfactory
function). Psychological conditions, such as claustrophobia, can
also impair the effective use of respirators by employees and may
also cause, independent of physiological burdens, significant
elevations in heart rate, blood pressure, and respiratory rate that
can jeopardize the health of employees who are at high risk for
cardiopulmonary disease (Ex. 22-14). One commenter (Ex. 54-429)
emphasized the importance of evaluating claustrophobia and severe
anxiety, noting that these conditions are often detected during
respirator training. (See 63 FR 1152, at 330, 01/08/1998)
NIOSH, in its response to MSHA's proposed DPM rule, recommended
that ``mine operators be required to have a written respiratory
protection program, analogous to that required by OSHA for general
industry in 29 CFR 1910.134 Respiratory Protection, that is work-site
specific and includes administration by a trained program
administrator, respirator selection criteria, worker training, a
program to determine that the workers are medically able to use
respiratory protective equipment, and provisions for regular evaluation
of the program's effectiveness.''
Organized labor and industry were divided on this issue. In
general, industry commenters oppose any additions to the respiratory
protection requirements for compliance with the current air quality
standards. Some commenters also suggested that MSHA address any
additional respiratory protection requirements in a separate rulemaking
applicable to all airborne contaminants. Organized labor strongly
emphasized in their comments that to protect miners' jobs, the final
rule must contain requirements for an effective respiratory protection
program, including a written program, medical evaluation of respirator
wearers, and transfer of miners unable to wear respirators. Some
commenters stated that their respiratory protection programs already
provide for medical examination of miners before they are required to
wear respiratory protection. One commenter stated that in an
underground mine, transfer of employees to areas free of diesel exhaust
would be extremely difficult.
MSHA believes that it is feasible for mine operators to achieve
compliance with the interim limit by using effective engineering and
administrative controls in most circumstances. As a result, MSHA
projects that there will be very few instances where miners will be
required to wear respirators for long-term compliance. Further, mine
operators have several alternatives in respirator selection. They can
choose either positive- or negative-pressure respirators, or powered or
non-powered air purifying respirators. Those few miners who have a
medical condition that would prevent them from wearing a negative-
pressure respirator could be provided with and could normally wear a
powered air purifying respirator. MSHA believes that it would be a rare
occurrence to encounter a miner who could not wear any type of
respirator due to a medical condition.
Whereas MSHA agrees that there is sound evidence establishing that
some persons may have difficulty wearing respirators and should be
prohibited from wearing these devices, MSHA finds that many mine
operators have voluntarily established programs to medically evaluate
miners' ability to wear respirators. One document in the rulemaking
record that supports this position was developed by the Bureau of Labor
Statistics of the Department of Labor and the National Institute for
Occupational Safety and Health. These two agencies issued a recent
joint survey report entitled ``Respirator Usage in Private Sector
Firms, 2001.'' This publication summarizes the results of a
questionnaire mailed to over 40,000 general industry and mining
companies. The survey found that 64% (2,246) of the estimated 3,493
mining companies that used respirators during the 12 months prior to
the survey assess employees' medical fitness to wear respirators. The
survey also found that 61% (2,138) of these mining companies have
written procedures and schedules for maintaining respirators. The 3,493
mining companies, however, included establishments that extract oil and
Although the Mine Act requires, where appropriate, that MSHA
standards prescribe the type and frequency of medical examinations to
determine whether the health of miners is adversely affected by
exposure to hazards, it does not mandate medical examinations to
determine a miner's ability to wear PPE for protection from those
Based on the above, MSHA believes a requirement for medical
evaluation of respirator wearers, and transfer of miners unable to wear
respirators is inappropriate for this rulemaking. Such requirements
would have minimal application, particularly considering the extent to
which mine operators are voluntarily implementing such provisions
and the limited long term use of respirators envisioned under the interim rule.
Application To Use Respirators Section 57.5060(d) of the 2001 final rule
permits miners engaged in specific activities involving inspection, maintenance, or repair
activities to work in concentrations of DPM that exceed the interim and
final limits, to use respiratory protection with advance approval from
the Secretary. In MSHA's 2003 NPRM, it proposed several changes to its
requirements on respiratory protection, including deleting the
requirement that mine operators apply in writing to the Secretary for
approval to use respiratory protection.
Although some commenters recommended requiring approval by the
Secretary before respiratory protection should be permitted as a means
of compliance with the applicable DPM limit, MSHA was not persuaded
that such a step would be necessary, and the final Sec. 57.5060(d)
does not include this recommendation. Respiratory protection functions
as a supplemental control. Operators must have ready access to
respirators when they must be used to supplement protection provided by
controls. When a mine operator is issued a citation under Sec.
57.5060(d) for a miner's exposure exceeding the applicable DPM limit,
and the mine operator intends to use respiratory protection as an
interim control measure, MSHA will make certain that a respiratory
protection program is established and appropriate respirators are used
in accordance with Sec. 57.5005(a), (b) and Sec. 57.5060(d)(1) and
(d)(2) concerning filter selection for air-purifying respirators.
Accordingly, the requirement to apply in writing to the Secretary for
approval to use respiratory protection can be deleted from the existing
rule without reducing protection to the miners.
D. Section 57.5061 Compliance Determination
(1) Section 57.5061(a)
Under existing 57.5061(a), the Secretary determines compliance with
``an applicable limit on the concentration of [DPM] pursuant to Sec.
57.5060.'' MSHA only proposed conforming changes to Sec. 57.5061(a).
As proposed, final Sec. 57.5061(a) deletes the term ``concentration
limit'' and replaces it with the term ``DPM limit'' to reflect a
permissible exposure limit in Sec. 57.5060(a) and a concentration
limit in existing Sec. 57.5060(b). MSHA did not receive comments
specific to this conforming change. MSHA did not propose changes to the
single sample compliance determination but received comments from
industry on this issue. Those comments are beyond the scope of this
rulemaking and not included in this preamble discussion.
(2) Section 57.5061(b)
Compliance determinations under existing Sec. 57.5061(b) are based
on TC measurements. As in the 2003 NPRM, final Sec. 57.5061(b)
reflects that compliance determinations will be based on EC
measurements instead of TC. This change conforms to the proposed change
in the interim limit in Sec. 57.5060(a). Copies of the NIOSH 5040
Analytical Method can be obtained at http://www.cdc.gov/niosh or it can be obtained by contacting MSHA's Pittsburgh Safety and the Health
Technology Center, P.O. Box 18233, Cochrans Mill Road, Pittsburgh, PA
15236. As a result, the address in the existing rule is removed from
the regulatory language.
MSHA did not receive comments on this conforming change.
(3) Section 57.5061(c)
Under existing Sec. 57.5061(c), the Secretary determined the
appropriate sampling strategy for conducting compliance sampling
utilizing personal sampling, occupational sampling, or area sampling,
based on the circumstances of a particular exposure. MSHA proposed that
Sec. 57.5061(c) specify that only personal sampling would be utilized
for compliance determinations. The final rule adopts this change which
does not alter compliance requirements for mine operators.
MSHA believes that, since it has adopted EC as the surrogate for
DPM, personal sampling alone will result in an accurate determination
of miner exposure to DPM. Section 57.5060(a) establishes a DPM limit
that specifically relates to the exposure of miners to DPM. Since the
limit relates to the exposure of miners, the appropriate sampling
method to determine compliance is personal sampling. In this respect,
the sampling method for compliance determination with this rule is
consistent with MSHA's longstanding practice of utilizing personal
sampling to determine compliance with exposure limits for other
airborne contaminants in the M/NM sector.
MSHA anticipates several benefits of standardizing personal
sampling as the compliance sampling method. MSHA expects that mine
operators and miners are already familiar with personal sampling, since
MSHA utilizes it routinely when compliance sampling for noise, dust,
and other airborne contaminants. Utilizing personal sampling eliminates
possible disputes that could have arisen over whether an area sample
was obtained ``where miners normally work or travel.'' Mine operators
who choose to conduct environmental monitoring for DPM under Sec.
57.5071 using MSHA's compliance sampling method will not need to
anticipate which sampling method MSHA would most likely have selected
(personal, area, or occupational) based on the circumstances of a
particular exposure. Personal sampling avoids situations where area
sampling is intended to capture the exposure of a particular miner for
the full work shift even if that miner moves to a new location during
the shift. Personal sampling for EC avoids the problem of determining
compliance for an equipment operator who is a smoker and who works
inside an enclosed cab. The measurement of DPM using EC as the
surrogate is not affected by ETS. Under the existing rule, this miner
could not be sampled inside the cab due to interference from tobacco
smoke, and area sampling outside the cab would not indicate that
miner's DPM exposure or the impact of the environmental cab.
Most industry and labor commenters supported personal sampling. A
few commenters, however, were opposed to the elimination of area and
occupational sampling for compliance determination. Two commenters
suggested that relying on personal sampling alone would enable a mine
operator to influence the sampling result to the mine operator's
advantage by re-assigning a miner being sampled to an area with lower
DPM levels. MSHA believes that although a mine operator may attempt to
defeat compliance sampling by re-assigning the miner being sampled,
MSHA's existing enforcement authority is adequate to ensure a valid and
representative sample can nonetheless be obtained. If the miner being
sampled for DPM is re-assigned to a different workplace with lower DPM
levels, or the miner's DPM exposure is deliberately manipulated by some
other means, such as by withdrawing a ``dirty'' piece of equipment from
the area where the miner is working, the inspector has the authority to
investigate the circumstances, and invalidate the sample if the
inspector determines that the miner's workday was not representative.
Other commenters supported the retention of area and occupational
sampling to give inspectors flexibility and to avoid sample tampering.
While MSHA is sensitive to these issues, it believes it has the authority
to address them in existing enforcement procedures.
One commenter suggested that exposure be defined for this
regulation as ``the exposure that would occur if the employee were not
using respiratory protective equipment.'' MSHA agrees with this
position but believes that it is unnecessary to be this specific in the
regulation. MSHA's longstanding practice for assessing exposure to an
airborne contaminant is to not give credit for respiratory protection
in determining a worker's exposure. MSHA, however, does encourage
workers to use respiratory protection.
MSHA believes that the use of EC as the DPM surrogate allows the
exclusive use of personal sampling to establish compliance with the DPM
limit. MSHA believes that this consistency in sampling strategy
outweighs concerns of commenters.
E. Section 57.5062 DPM Control Plan
Existing Sec. 57.5062 requires mine operators to establish a DPM
control plan, or modify the plan, upon receiving a citation for an
overexposure to the concentration limit in Sec. 57.5060. A single
citation triggers the plan. A violation of the plan is citable without
consideration of the current DPM concentration level. The operator must
demonstrate that the new or modified plan will be effective in
controlling the DPM concentration to the limit. The existing rule also
sets forth a number of other specific details about the plan, including
a description of controls that the operator will use to maintain the
DPM concentration; a list of diesel-powered units maintained by the
mine operator; information about each unit's emission control device;
demonstration of the plan's effectiveness; verification sampling;
retention of a copy of the control plan at the mine site for the
duration of the plan plus one year; and a plan duration of three years
from the date of the violation requiring establishment of the plan. By
notice of July 18, 2002, MSHA stayed the effectiveness of this standard
pending completion of this rulemaking (67 FR 47296).
In accordance with the DPM settlement agreement, MSHA agreed to
publish a notice of proposed rulemaking to revise current Sec.
57.5062. The settlement agreement, however, did not specify how MSHA
should revise this section. In its 2003 NPRM, MSHA proposed provisions
to modify and simplify the plan requirements, including deleting the
requirement for operators to demonstrate plan effectiveness by
MSHA's rationale for requiring a DPM control plan was derived from
the rule's initial approach to setting control requirements. MSHA
recognized that every mine covered by this rule had unique conditions
and circumstances that affect DPM exposures such as the number and
sizes of diesel-powered engines, idling duration and frequency,
emission controls, diesel maintenance practices, and ventilation. MSHA
was also interested in developing uniform DPM control requirements that
would be effective in protecting miners' health and practical for the
mining industry to implement. MSHA acknowledges that there are numerous
approaches in accomplishing this objective.
In the existing rule, the control plan would only have to include a
description of the controls the operator would use to maintain the
concentration of DPM to the applicable limit, a list of diesel-powered
units maintained by the mine operator, information about any units
emission control device, and the parameters of any other methods used
to control the concentration of DPM. Operators could also consolidate
the DPM control plan with ventilation plan.
In proposed Sec. 57.5062, MSHA would require an operator to
establish a written control plan, or modify an existing control plan,
if it will take the mine operator more than 90 calendar days from the
date of a citation to achieve compliance. A single violation of the PEL
would continue to be the basis for triggering the requirement for a
control plan. The control plan would remain in effect for a one-year
period following termination of the citation. Mine operators would also
be required to include in the plan a description of the controls that
will be used to reduce the miners' exposures to the PEL.
Although MSHA proposed to retain the control plan, MSHA clearly
alerted the mining community of the possibility that it would delete
the control plan in the final rule. MSHA raised concerns with
justifying the need for a control plan requirement in light of the
other proposed revisions to the DPM rule, including MSHA's traditional
hierarchy of controls for exposure-based standards. MSHA also currently
maintains an inventory of the diesel-powered equipment in each mine.
Consequently, MSHA asked the mining community for its views on this
alternative approach in light of the other proposed changes to the DPM
standard. MSHA received a number of comments on this issue.
Some commenters were in favor of retaining the control plan
provisions and stated that MSHA had provided no evidence indicating
that control plans are infeasible. Several other commenters who oppose
deleting the control plan requirement stated that planning is essential
for any complex activity, and that mine operators have spent a great
deal of time and money in this rulemaking, arguing that the control of
DPM is exceedingly complex. They felt it was hard to understand how
mine operators could simultaneously argue that control plans are
Other commenters favored deleting existing Sec. 57.5062 because
the hierarchy of controls would ensure that operators employ all
reasonable means to maintain allowable levels of DPM. Some of these
commenters stated that if compliance cannot be achieved through
engineering and administrative controls, they were required to use
respiratory protection, and the end result would be that miners are
protected from overexposure. They stated that a mine operator would get
a citation if miners are not protected, and during the abatement period
the operator must comply with DPM requirements addressing maintenance,
after-treatment controls, low sulfur fuel, proper idling practices and
Commenters opposed to retention of the control plan provisions felt
that a control plan would add nothing to miner health, and create a
paperwork burden. They stated the enforcement process provides all the
documentation necessary for compliance. They also believe that the
requirement for a control plan is a disproportionate response to a
single overexposure. MSHA initially intended to apply a concentration
limit that would result in controlling DPM in the underground mine
environment. Since MSHA has changed the compliance approach from a
concentration limit to a personal exposure limit, the control plan
would have to address each miner's overexposure, rather than reducing
MSHA agrees with commenters who believe that the control plan is
unjustifiable in the final rule. Moreover, the DPM rulemaking record
contains little, if any, rationalization in support of retaining this
provision. The hierarchy of controls in the final rule ensures that
operators employ all means to maintain allowable exposure levels of
DPM. MSHA is, therefore, deleting existing Sec. 57.5062, DPM control
plan. MSHA can monitor an operator's good faith efforts and obtain
supporting documentation during regular inspections. Operators may
choose to control DPM emissions by filtering the diesel-powered
equipment; installing cleaner-burning engines; increasing ventilation;
improving fleet management; utilizing administrative controls; or using a variety of
other readily available controls, all without consulting with, or
seeking approval from MSHA.
MSHA also agrees with those commenters that expressed concerns
about the increase in paperwork requirements. In promulgating standards
for the mining industry, MSHA takes considerable initiative to avoid
placing an unreasonable burden upon mine operators, especially small
mine operators. It was never MSHA's intent to have unnecessary
duplication of effort in obtaining compliance under the DPM rule.
The existing rule also contained a requirement in Sec. 57.5062(c)
that the operator must demonstrate plan effectiveness by monitoring.
Although MSHA has deleted the control plan requirements in this final
rule, MSHA believes that monitoring to verify the effectiveness of DPM
controls is adequately addressed under Sec. 57.5071, which requires
mine operators to monitor in order to determine, under conditions that
can be reasonably anticipated in the mine, whether DPM exposures exceed
the applicable limits specified in Sec. 57.5060. These requirements
provide an effective alternative to the existing requirement in Sec.
57.5062(c) for operators to demonstrate plan effectiveness by
monitoring. Further, MSHA will conduct additional compliance sampling
whenever MSHA suspects that miners' exposures to DPM are not being
maintained to the PEL.
Although a control plan might serve to deter repeat overexposures,
MSHA can utilize existing enforcement tools to accomplish this purpose.
For example, MSHA often asks operators to provide a control strategy to
justify extending citations. MSHA also documents action taken by the
operator to comply when terminating a citation. Further, repeat
overexposures can be cited with a higher degree of negligence that
typically require a higher penalty assessment. Failure to correct
overexposure conditions in a timely manner could also be addressed
through existing mechanisms such as Section 104(b) of the Mine Act that
includes sanctions currently employed for failure to abate violations.
F. Section 57.5075 Diesel Particulate Records
Existing Sec. 57.5075(a) summarizes the recordkeeping requirements
of the DPM standards contained in Sec. Sec. 57.5060 through 57.5071.
As proposed, MSHA has renumbered the Diesel Particulate Recordkeeping
Requirements table and added the recordkeeping requirement established
in existing Sec. 57.5071(c) for records of corrective actions taken.
This notation was inadvertently omitted from the table in the 2001
MSHA also proposed that the record of corrective action be retained
``until the citation is terminated.'' MSHA has changed this retention
period in the final rule to ``Until the corrective action is
As proposed, MSHA also has deleted the table entry for existing
Sec. 57.5060(d), ``approved plan for miners to perform inspection,
maintenance or repair activities in areas exceeding the concentration
limit,'' as the corresponding provision of the rule was deleted.
MSHA also deleted, as proposed, records relating to Sec.
57.5062(c), ``compliance plan verification sample results.''
Finally, the final rule eliminates the additional recordkeeping
requirements relating to control plans pursuant to Sec. 57.5062 since
this final rule deletes the existing requirements for such plans.
Of the comments received on the general subject of recordkeeping,
only two were directed at the proposed changes to the recordkeeping
requirements. Of the comments that were relevant to the scope of this
rulemaking, most of the comments expressed concern about the
recordkeeping burden required by Sec. 57.5062(a) as related to control
plans. As noted above, the control plan requirement has been removed
from the final rule.
One of the two comments that addressed proposed changes to the
recordkeeping requirements identified possible errors in the Diesel
Particulate Recordkeeping Requirements table in Sec. 57.5075(a)
(Recordkeeping Requirements table). The commenter noted that the
existing rule requires that a record of applications approved for
extensions of time to comply with the exposure limits must be retained
one year beyond the duration of the extension. The commenter stated
that this requirement did not reflect MSHA's intent as stated in the
preamble to the existing rule to retain this record for the duration of
the extension. MSHA agrees that the recordkeeping requirement listed in
the existing rule was in error. MSHA proposed to correct this error in
the 2003 NPRM and has adopted the change in this rule. The final rule
clarifies that the required retention time for this record is for the
duration of the extension.
This commenter also noted that the retention time for evidence of
corrective action taken as a result of a mine operator's environmental
monitoring per Sec. 57.5071(c) was listed in Table 57.5075(a) in the
2003 NPRM as, ``Until the citation is terminated.'' MSHA agrees that
this table entry is in error, as a citation would not be issued on the
basis of an operator's environmental monitoring. MSHA has corrected the
table entry in the final rule to read ``Until the corrective action is
The other comment relating to proposed changes in recordkeeping
requirements expressed the general concern that the information
collection provisions of the rule are not necessary for MSHA to perform
its functions. The commenter suggested reducing the paperwork burden by
relying on current testing for gaseous emissions and deleting the final
DPM limit from the rule.
MSHA believes that each record specified in Sec. 57.5075 relates
to information that MSHA must have access to in order to determine that
the mine operator is complying with the corresponding provisions of the
X. Distribution Table
Old section New section
57.5060(f).......................... 57.5060(d) and (e)
XI. Regulatory Impact Analysis
This part of the preamble reviews several impact analyses which
MSHA is required to provide in connection with its final rulemakings.
The full text of these analyses can be found at MSHA's Regulatory
Economic Analysis (REA) Web page which is available from MSHA at http://www.msha.gov/REGSINFO.HTM
A. Costs and Benefits: Executive Order 12866 Regulatory Planning and
Review and Regulatory Flexibility Act
Executive Order 12866, as amended by Executive Order 13258,
requires that regulatory agencies assess both the costs and benefits of
regulations. The final rule will result in estimated net cost savings
(negative costs) for underground M/NM mine operators of $3,634 per
year. This represents an average yearly savings of $20 per mine for the
177 underground metal/non-metal mines that will be affected by this
final rule. Of these 177 mines, 66 have fewer than 20 workers; 107 have
20 to 500 workers; and 4 have more than 500 workers. For a complete
breakdown of the compliance costs and savings of the final rule, see
Chapter IV of the REA associated with this rulemaking.
The amended provisions in this final rule will increase flexibility
of compliance with the existing final rule, but continue to reduce
significant health risks to underground miners. Benefits of the
existing final rule are those discussed by MSHA in the REA for the
January 19, 2001 final rule and include reductions in lung cancers. In
the long run, as the mining population turns over, MSHA estimates that
a minimum of 8.5 lung cancer deaths will be avoided per year. Other
benefits noted in the 2001 REA were reductions in the risk of death
from cardiovascular, cardiopulmonary, or respiratory causes and
reductions in the risk of sensory irritation and respiratory symptoms.
B. Regulatory Flexibility Act (RFA) and Small Business Regulatory
Enforcement Fairness Act (SBREFA)
The Regulatory Flexibility Act (RFA) requires regulatory agencies
to consider a rule's economic impact on small entities. Under the RFA,
MSHA must use the Small Business Administration's (SBA's) criterion for
a small entity in determining a rule's economic impact unless, after
consultation with the SBA Office of Advocacy, MSHA establishes an
alternative definition for a small mine operator and publishes that
definition in the Federal Register for notice and comment. For the
mining industry, SBA defines ``small'' as a mine operator with 500 or
fewer employees. Traditionally, MSHA has also looked at the impacts of
its final rules on a subset of mines with 500 or fewer employees--
those with fewer than 20 employees, which the mining community refers
to as ``small mines.'' These small mines differ from larger mines not
only in the number of employees, but also, among other things, in
economies of scale in material produced, in the type and amount of
production equipment, and in supply inventory. Therefore, their costs
of complying with MSHA rules and the impact of MSHA rules on them would
also tend to be different. It is for this reason that ``small mines,''
as traditionally defined by the mining community, are of special
concern to MSHA.
Therefore, MSHA's analysis complies with the legal requirements of
the RFA for an analysis of the impacts on ``small entities'' while
continuing MSHA's traditional look at ``small mines.'' Using SBA's
definition of a small mine operator, the estimated yearly net
compliance cost savings of this final rule on small underground M/NM
mine operators is approximately $3,675. These estimated yearly net
compliance cost savings compare with estimated annual revenues of
approximately $2.35 billion for small underground M/NM mine operators
with 500 or fewer employees. Using MSHA's definition of a small mine
operator, the estimated yearly net compliance cost savings of this
final rule on small underground M/NM mine operators is approximately
$4,795. These estimated yearly net compliance cost savings compare with
estimated annual revenues of approximately $0.14 billion for small
underground M/NM mine operators with 20 or fewer employees.
MSHA concludes that the final DPM rule would not have a significant
economic impact on a substantial number of small entities that are
covered by this rulemaking. MSHA has determined that this is the case
both for mines affected by this rulemaking with fewer than 20 employees
and for mines affected by this rulemaking with 500 or fewer employees.
MSHA has certified these findings to the SBA. The factual basis for
this certification is discussed in Chapter V of the REA associated with
C. Paperwork Reduction Act (PRA)
This final rule contains changes to information collection
requirements in various provisions. Most of these paperwork
requirements were previously approved by OMB as part of OMB Control
Number 1219-0135. The information collection requirements are
summarized below and explained in detail in the REA that accompanies
the rule. The REA includes the estimated costs and assumptions for the
paperwork requirements related to this final rule. A copy of the REA is
available on our Web site at http://www.msha.gov/regsinfo.htm and can
also be obtained in hard copy from MSHA. These information collection
requirements have been submitted to OMB for review under 44 U.S.C.
3504(h) of the Paperwork Reduction Act of 1995, as amended. Respondents
are not required to respond to any collection of information unless it
displays a current valid OMB control number.
As a result of this rule, mine operators will obtain burden hour
and cost savings for the first two years that the rule is in effect. In
the third year that the rule is in effect, mine operators will incur a
net increase in burden hours and costs. For every year thereafter,
burden hours and costs will be the same as in the third year.
In the first year of the rule, mine operators will incur burden
hour savings of approximately 274 hours. These savings will result from
mine operators (1) not having to apply for approval from the Secretary
to work in concentrations of DPM exceeding the applicable limit under
Sec. 57.5060(d) of the 2001 final rule and maintaining the conditions
of the approval during the period that the interim concentration limit
is in effect; and (2) not having to write a DPM Control Plan under
In the second year of the rule, mine operators' burden savings
increase to about 961 hours. These savings will result from mine
operators (1) not having to apply for approval from the Secretary to
work in concentrations of DPM exceeding the applicable limit under
Sec. 57.5060(d) of the 2001 final rule and maintaining the conditions
of the approval during the period that the final concentration limit is
in effect; and (2) not having to write a DPM Control Plan under Sec.
In the third year of the rule, mine operators will incur a net
increase of about 368 burden hours. This increased burden occurs
because mine operators will no longer experience the savings from not
having to apply for approval from the Secretary to work in
concentrations of DPM exceeding the applicable limit under Sec.
57.5060(d) of the 2001 final rule and maintaining the conditions of the
approval during the period that the final concentration limit would be
in effect; and will incur an increase in burden associated with
requesting special extensions of the final concentration limit under
Mine operators incur a net increase in paperwork burden costs of
$12,250 per year. This net increase is composed of an annualized cost
increase of $24,181 per year from changes to Sec. 57.5060(c); an
annualized cost decrease of $6,394 per year from changes to Sec.
57.5060(d); and an annualized cost decrease of $5,537 per year from
changes to Sec. 57.5062.
In comparison with the 2003 NPRM, this final rule revises two
provisions (Sec. Sec. 57.5060(c) and 57.5062) in a manner that reduces
the burden hours and associated costs. These reductions in burden hours
and associated cost savings relative to the 2003 NPRM are incorporated
into the calculations of the previous paragraphs, which compare the
final rule with the existing rule.
Sections 57.5071 and 57.5075 both involve information collection
activities. Section 57.5071 triggers notice requirements when
environmental monitoring indicates that the DPM limit has been
exceeded. The paperwork burden for this provision has not changed from
the former requirements. Section 57.5075 summarizes in chart form the
recordkeeping requirements of the rule. The paperwork burden has only
changed for three of the provisions listed, Sec. Sec. 57.5060(c),
57.5060(d), and 57.5062. These provisions are discussed more fully
above and in the REA.
MSHA received several comments regarding information collection.
Some commenters stated that the paperwork requirements for developing a
control plan were too burdensome, and others stated that they were
justified. MSHA has removed the requirement for control plans due to
the establishment of the hierarchy of controls for meeting the interim
PEL. Removal of the control plan requirement is discussed at length
under the section-by-section discussion for Sec. 57.5062.
Some commenters stated that all information collection activities
associated with the rule including DPM sampling and analysis mandates,
the plan provisions, the posting requirements, and all of the required
records are unnecessary because MSHA can perform its job without such
requirements as demonstrated by the existence of standards that control
other diesel exhaust components. MSHA disagrees. Although MSHA has
deleted certain information collection requirements in this final rule,
it considers those included to be necessary to determine whether mine
operators are in compliance with the rule.
D. The Unfunded Mandates Reform Act of 1995
This final rule does not include any Federal mandate that may
result in increased expenditures by State, local, or tribal
governments; nor does it increase private sector expenditures by more
than $100 million annually; nor does it significantly or uniquely
affect small governments. Accordingly, the Unfunded Mandates Reform Act
of 1995 (2 U.S.C. 1501 et seq.) requires no further agency action or
E. National Environmental Policy Act
MSHA has reviewed this final rule in accordance with the
requirements of the National Environmental Policy Act (NEPA) of 1969
(42 U.S.C. 4321 et seq.), the regulations of the Council on
Environmental Quality (40 U.S.C. 1500), and the Department of Labor's
NEPA procedures (29 CFR part 11).
This final rule has no significant impact on air, water, or soil
quality; plant or animal life; the use of land; or other aspects on the
human environment. MSHA solicited public comment concerning the
accuracy and completeness of this environmental assessment when this
rule was first proposed, and received no comments relevant to this
environmental assessment. MSHA finds, therefore, that the final rule
has no significant impact on the human environment. Accordingly, MSHA
has not provided an environmental impact statement.
F. The Treasury and General Government Appropriations Act of 1999:
Assessment of Federal Regulations and Policies on Families
This final rule has no affect on family well-being or stability,
marital commitment, parental rights or authority, or income or poverty
of families and children. Accordingly, Section 654 of the Treasury and
General Government Appropriations Act of 1999 (5 U.S.C. 601 note)
requires no further agency action, analysis, or assessment.
G. Executive Order 12630: Government Actions and Interference With
Constitutionally Protected Property Rights
This final rule does not implement a policy with takings
implications. Accordingly, Executive Order 12630, Governmental Actions
and Interference with Constitutionally Protected Property Rights,
requires no further agency action or analysis.
H. Executive Order 12988: Civil Justice Reform
This final rule was written to provide a clear legal standard for
affected conduct, and was carefully reviewed to eliminate drafting
errors and ambiguities, so as to minimize litigation and undue burden
on the Federal court system. Accordingly, this final rule meets the
applicable standards provided in Section 3 of Executive Order 12988,
Civil Justice Reform.
I. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks
This final rule has no adverse impact on children. Accordingly,
Executive Order 13045, Protection of Children from Environmental Health
Risks and Safety Risks, as amended by Executive Orders 13229 and 13296,
requires no further agency action or analysis.
J. Executive Order 13132: Federalism
This final rule does not have ``federalism implications,'' because
it does not ``have substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government.'' Accordingly, Executive Order 13132, Federalism, requires
no further agency action or analysis.
K. Executive Order 13175: Consultation and Coordination With Indian
This final rule does not have ``tribal implications,'' because it
does not ``have substantial direct effects on one or more Indian
tribes, on the relationship between the Federal government and Indian
tribes, or on the distribution of power and responsibilities between
the Federal government and Indian tribes.'' Accordingly, Executive
Order 13175, Consultation and Coordination with Indian Tribal
Governments, requires no further agency action or analysis.
L. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
Regulation of the M/NM sector of the mining industry has no
significant impact on the supply, distribution, or use of energy. This
final rule is not a ``significant energy action,'' because it is not
``likely to have a significant adverse effect on the supply,
distribution or use of energy'' * * * (including a shortfall in supply,
price increases, and increased use of foreign supplies).'' Accordingly,
Executive Order 13211, Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use, requires no
further agency action or analysis.
M. Executive Order 13272: Proper Consideration of Small Entities in
MSHA has thoroughly reviewed this final rule to assess and take
appropriate account of its potential impact on small businesses, small
governmental jurisdictions, and small organizations. As discussed in
Chapter V of the REA, MSHA has determined and certified that this final
rule will not have a significant economic impact on a substantial
number of small entities. MSHA solicited public comment concerning the
accuracy and completeness of this potential impact when the rule was
first proposed. The agency took appropriate account of comments
received relevant to the rule's potential impact on small entities.
Accordingly, Executive Order 13272, Proper Consideration of Small Entities in Agency Rulemaking,
requires no further agency action or analysis.
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Chase, Gerald. ``Characterizations of Lung Cancer in Cohort Studies
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2004, May 6.
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(2001) and 66 FR 35521 (2001).
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MSHA, Pittsburgh Safety and Health Technology Center, Reports:
Barrick Goldstrike Mines, Inc., Elko, Nevada, Sampling for Diesel
Particulate Interferences, November 16, 1999; dated March 15, 2000.
Black River Mine, Carmeuse Lime and Stone, Inc., Butler, Kentucky,
PS&HTC-DD-03-316, Diesel Particulate Concentrations from DPM Study,
March 18 and 19, 2003, April 8 and 9, 2003, and April 29 and 30,
2003; dated August 15, 2003.
Black River Mine, Carmeuse Lime and Stone, Inc., Butler, Pendleton
County, Kentucky, PS&HTC-DD-04-420, Diesel Particulate Matter
Compliance Assistance Studies, March 16-18, 2004, April 13 and 14,
2004, and May 25 and 26, 2004; dated July 14, 2004.
Blue Rapids Mine, Blue Rapids, Kansas, Georgia-Pacific Gypsum
Corporation, Diesel Particulate Compliance Assistance Visit,
September 10, 2003; dated December 2, 2003.
Burning Springs Mine, Martin Marietta Materials Inc., Wood County,
West Virginia, Dust Compliance Assistance Visit to Evaluate Effects
of Diesel Equipment Modification, July 29 and 30, 2003 and October 7
and 8, 2003; dated March 23, 2004.
Clover Bottom Mine, M.A. Walker, LLC, Clover Bottom, Kentucky, July
8, 2003; dated August 15, 2003.
Durham Mine, Martin Marietta Aggregates, Inc., Marion County, Iowa,
PS&HTC-DD-04-423, Diesel Particulate Concentrations from Diesel
Particulate Matter Studies, April 6 and 7, 2004 and May 25 and 26,
2004; dated August 19, 2004.
Fletcher Mine, The Doe Run Company, Viburnum, Missouri, Compliance
Assistance Visit, July 8, 2003; dated September 4, 2003.
Georgetown Mine, Nally and Gibson, Georgetown, Kentucky, Compliance
Assistance Visit, May 7, 2003; dated August 15, 2003.
Governeur Talc Company, Inc., No. 4 Mine, Lewis County, New York,
Diesel Particulate Compliance Assistance Survey, June 18, 2003;
dated July 3, 2003.
Greens Creek Mine, Kennecott Minerals, Juneau, Alaska, January 22-
30, 2003; dated June 17, 2003.
Greer Limestone Mine, Greer Limestone Company, Monongalia County,
WV, Diesel Particulate Compliance Assistance Survey, September 16,
2003; dated December 2, 2003.
Hampton Corners Mine, American Rock Salt Company LLC, Livingston
County, New York, Diesel Particulate Compliance Assistance Survey,
March 23 and 24, 2004; dated May 14, 2004.
Hampton Corners Mine, Martin Marietta Materials, Inc., Livingston
County, New York, PS&HTC-DD-04-422, Environmental Diesel Particulate
Matter Investigation, March 23 and 24, 2004.
Independence Mine, Rocca Processing, LLC, Independence, Missouri,
Diesel Particulate Compliance Assistance Survey, June 25, 2003;
dated July 3, 2003.
Inland Quarries, AmeriCold Logistics, LLC, Kansas City, Kansas,
Diesel Particulate Compliance Assistance Survey, July 17, 2003;
dated August 15, 2003.
Jefferson County Stone Mine, Rogers Group, Inc., Jefferson County,
Kentucky, DPM Compliance Assistance Visit, December 12, 2002; dated
March 10, 2003.
Jefferson County Stone Mine, Rogers Group, Inc., Jefferson County,
Kentucky, PS&HTC-DD-03-312, Dust Compliance Assistance Visit to
evaluate effects of Diesel Equipment Modification, January 28-30,
2003 and June 9 and 10, 2003; dated September 4, 2003.
Kaylor No. 3 Mine, Brady's Bend Corporation, Armstrong County,
Pennsylvania, Diesel Particulate Compliance Assistance Survey,
September 25, 2003; dated October 20, 2003.
Kerford Limestone Mine, Kerford Limestone Company, Weeping Water,
Nebraska, Diesel Particulate Compliance Assistance Survey, September
10, 2003; dated October 20, 2003.
Lyons Salt Mine, Lyons Salt Company, Lyons, Kansas, Diesel
Particulate Compliance Assistance Visit, September 9, 2003; dated
November 3, 2003.
M&M Lime Company, Inc. Mine, Worthington, Armstrong County,
Pennsylvania, Diesel Particulate Compliance Assistance Survey, June
18, 2003; dated July 3, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky,
PS&HTC-DD-03-308, Diesel Particulate Concentrations from Diesel
Particulate Matter Studies, December 10-12, 2002, January 7-9, 2003,
and February 4-6, 2003; dated August 29, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky,
PS&HTC-DD-03-311, Diesel Particulate Concentrations from Diesel
Particulate Matter Studies, February 4-6, 2003 and April 1-3, 2003;
dated August 29, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky,
PS&HTC-DD-04-416, Diesel Particulate Concentrations from Diesel
Particulate Matter Studies, January 6 and 7, 2004, and February 2
and 3, 2004; dated April 2, 2004.
Oldham County Stone Mine, Rogers Group, Inc., Oldham County,
Kentucky, DPM Compliance Assistance Visit, November 20 and 21, 2002;
dated February 10, 2003.
Randolph Mine, Hunt Midwest Mining, Inc., Diesel Particulate
Compliance Assistance Survey, July 18, 2003; dated August 15, 2003.
Rock Springs Mine, Liter's Quarry, Inc., Diesel Particulate
Compliance Assistance Survey, July 9, 2003; dated August 15, 2003.
Stamper Mine, Hunt Midwest Mining, Inc., Platte County, Missouri,
Diesel Particulate Compliance Assistance Survey, July 15, 2003;
dated August 15, 2003.
Stillwater Mine, Stillwater Mining Company, Nye, Montana, PS&HTC 33-
04-428, Diesel Particulate Matter Compliance Assistance, June 7-17,
2004; dated August 6, 2004.
Stone Creek Brick Company Mine, Marsh A C JR Company, Stone Creek,
Ohio, PS&HTC-DD-03-320, Diesel Particulate Compliance Assistance
Visit, May 21, 2003; dated August 15, 2003.
Stone Creek Brick Company Mine, Marsh A C JR Company, Stone Creek,
Ohio, PS&HTC-DD-03-322, Diesel Particulate Concentrations from
Diesel Particulate Matter Studies, June 10 and 11, 2003 and July 29-
30, 2003; dated August 29, 2003.
Sweetwater Mine, The Doe Run Company, Viburnum, Missouri, Diesel
Particulate Compliance Assistance Visit, July 9, 2003; dated
September 4, 2003.
Table Rock 1 Mine, Table Rock Asphalt Construction Company,
Inc., Taney County, Missouri, Diesel Particulate
Compliance Assistance Visit, November 18, 2003; dated February 18,
Table Rock 3 Mine, Table Rock Asphalt Construction Company,
Inc., Stone County, Missouri, Diesel Particulate Compliance
Assistance Visit, November 19, 2003; dated February 18, 2004.
Weeping Water Mine, Martin Marietta Aggregates, Diesel Compliance
Assistance Survey, September 9, 2003; dated October 14, 2003.
Winfield Lime and Stone Company, Inc., Cabot, Butler County,
Pennsylvania, Diesel Particulate Compliance Assistance Survey, June
19, 2003; dated July 3, 2003.
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(This file was finalized after the publication of this rule.
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MSHA. Side Protocol of 31-Mine Study to Test Efficiency of SKC DPM
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in Underground Metal and Nonmetal Mines,'' June 3, 2002.
NIOSH, ``Diesel Emissions and Control Technologies in Underground
Metal and Nonmetal Mines,'' Edited notes prepared by Lewis Wade from
workshops (February 27, 2003 Cincinnati, Ohio and March 4, 2003 Salt
Lake City, Utah).
NIOSH, The Effectiveness of Selected Technologies in Controlling
Diesel Emissions in an Underground Mine--Isolated Zone Study at
Stillwater Mining Company's Nye Mine, (Phase I Final Report), DHHS
NIOSH, An Evaluation of the Effects of Diesel Particulate Filter
Systems on Air Quality and Personal Exposures of Miners at
Stillwater Mine Case Study: Production Zone, (Phase II), DHHS
NIOSH Analytical Method 5040, Elemental Carbon, December 14, 1994.
Copies of the NIOSH 5040 Analytical Method can be obtained at
http://www.cdc.gov/niosh or they can be obtained by contacting MSHA's
Pittsburgh Safety and the Health Technology Center, P.O. Box 18233,
Cochrans Mill Road, Pittsburgh, PA 15236.
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List of Subjects in 30 CFR Part 57
Diesel particulate matter, Metal and Nonmetal, Mine Safety and
Health, Underground mines.
Accordingly, chapter I of title 30 of the Code of Federal Regulations
is amended as follows:
PART 57--SAFETY AND HEALTH STANDARDS--UNDERGROUND METAL AND
1. The authority citation for part 57 continues to read as follows:
Authority: 30 U.S.C. 811 and 813.
Sec. 57.5062 [Removed]
2. Section 57.5062 is removed.
3. Also, in part 57:
A. Sections 57.5060, 57.5061, 57.5071, and 57.5075 are revised; and
B. Sections 57.5065, 57.5066, 57.5067, and 57.5070 are republished
The text reads as follows:
Sec. 57.5060 Limit on exposure to diesel particulate matter.
(a) A miner's personal exposure to diesel particulate matter (DPM)
in an underground mine must not exceed an average eight-hour equivalent
full shift airborne concentration of 308 micrograms of elemental carbon
per cubic meter of air (308EC g/m\3\). [This interim
permissible exposure limit (PEL) remains in effect until the final DPM
exposure limit becomes effective. When the final DPM exposure limit
becomes effective, MSHA will publish a document in the Federal
(b) After January 19, 2006, any mine operator covered by this part
must limit the concentration of diesel particulate matter to which
miners are exposed in underground areas of a mine by restricting the
average eight-hour equivalent full shift airborne concentration of
total carbon, where miners normally work or travel, to 160 micrograms
per cubic meter of air (160TC [mu]g/m\3\). (c)(1) If a mine requires
additional time to come into compliance with the final DPM limit
established in Sec. 57.5060 (b) due to technological or economic
constraints, the operator of the mine may file an application with the
District Manager for a special extension.
(2) The mine operator must certify on the application that the
operator has posted one copy of the application at the mine site for at
least 30 days prior to the date of application, and has provided
another copy to the authorized representative of miners.
(3) No approval of a special extension shall exceed a period of one
year from the date of approval. Mine operators may file for additional
special extensions provided each extension does not exceed a period of
one year. An application must include the following information:
(i) A statement that diesel-powered equipment was used in the mine
prior to October 29, 1998;
(ii) Documentation supporting that controls are technologically or
economically infeasible at this time to reduce the miner's exposure to
the final DPM limit.
(iii) The most recent DPM monitoring results.
(iv) The actions the operator will take during the extension to
minimize exposure of miners to DPM.
(4) A mine operator must comply with the terms of any approved
application for a special extension, post a copy of the approved
application for a special extension at the mine site for the duration
of the special extension period, and provide a copy of the approved
application to the authorized representative of miners.
(d) The mine operator must install, use, and maintain feasible
engineering and administrative controls to reduce a miner's exposure to
or below the DPM limit established in this section. When controls do
not reduce a miner's DPM exposure to the limit, controls are
infeasible, or controls do not produce significant reductions in DPM
exposures, controls must be used to reduce the miner's exposure to as
low a level as feasible and must be supplemented with respiratory
protection in accordance with Sec. 57.5005(a), (b), and paragraphs
(d)(1) and (d)(2) of this section.
(1) Air purifying respirators must be equipped with the following:
(i) Filters certified by NIOSH under 30 CFR part 11 (appearing in
the July 1, 1994 edition of 30 CFR, parts 1 to 199) as a high
efficiency particulate air (HEPA) filter;
(ii) Filters certified by NIOSH under 42 CFR part 84 as 99.97%
(iii) Filters certified by NIOSH for DPM.
(2) Non-powered, negative-pressure, air purifying, particulate-
filter respirators shall use an R- or P-series filter or any filter
certified by NIOSH for DPM. An R-series filter shall not be used for
longer than one work shift.
(e) Rotation of miners shall not be considered an acceptable
administrative control used for compliance with the DPM standard.
Sec. 57.5061 Compliance determinations.
(a) MSHA will use a single sample collected and analyzed by the
Secretary in accordance with the requirements of this section as an
adequate basis for a determination of noncompliance with the DPM limit.
(b) The Secretary will collect samples of DPM by using a respirable
dust sampler equipped with a submicrometer impactor and analyze the
samples for the amount of elemental carbon using the method described
in NIOSH Analytical Method 5040, except that the Secretary also may use
any methods of collection and analysis subsequently determined by NIOSH
to provide equal or improved accuracy for the measurement of DPM.
(c) The Secretary will use full-shift personal sampling for
Sec. 57.5065 Fueling practices.
(a) Diesel fuel used to power equipment in underground areas must
not have a sulfur content greater than 0.05 percent. The operator must
retain purchase records that demonstrate compliance with this requirement for one year after the date of purchase.
(b) The operator must only use fuel additives registered by the
U.S. Environmental Protection Agency in diesel powered equipment
operated in underground areas.
Sec. 57.5066 Maintenance standards.
(a) Any diesel powered equipment operated at any time in
underground areas must meet the following maintenance standards:
(1) The operator must maintain any approved engine in approved
(2) The operator must maintain the emission related components of
any non-approved engine to manufacturer specifications; and
(3) The operator must maintain any emission or particulate control
device installed on the equipment in effective operating condition.
(b)(1) A mine operator must authorize each miner operating diesel-
powered equipment underground to affix a visible and dated tag to the
equipment when the miner notes evidence that the equipment may require
maintenance in order to comply with the maintenance standards of
paragraph (a) of this section. The term evidence means visible smoke or
odor that is unusual for that piece of equipment under normal operating
procedures, or obvious or visible defects in the exhaust emissions
control system or in the engine affecting emissions.
(2) A mine operator must ensure that any equipment tagged pursuant
to this section is promptly examined by a person authorized to maintain
diesel equipment, and that the affixed tag not be removed until the
examination has been completed. The term promptly means before the end
of the next shift during which a qualified mechanic is scheduled to
(3) A mine operator must retain a log of any equipment tagged
pursuant to this section. The log must include the date the equipment
is tagged, the date the equipment is examined, the name of the person
examining the equipment, and any action taken as a result of the
examination. The operator must retain the information in the log for
one year after the date the tagged equipment was examined.
(c) Persons authorized by a mine operator to maintain diesel
equipment covered by paragraph (a) of this section must be qualified,
by virtue of training or experience, to ensure that the maintenance
standards of paragraph (a) of this section are observed. An operator
must retain appropriate evidence of the competence of any person to
perform specific maintenance tasks in compliance with those standards
for one year after the date of any maintenance, and upon request must
provide the documentation to the authorized representative of the
Sec. 57.5067 Engines.
(a) Any diesel engine introduced into an underground area of a mine
covered by this part after July 5, 2001, other than an engine in an
ambulance or fire fighting equipment which is utilized in accordance
with mine fire fighting and evacuation plans, must either:
(1) Have affixed a plate evidencing approval of the engine pursuant
to subpart E of part 7 of this title or pursuant to part 36 of this
(2) Meet or exceed the applicable particulate matter emission
requirements of the Environmental Protection Administration listed in
Table 57.5067-1, as follows:
EPA requirement EPA category PM limit
40 CFR 86.094-8(a)(1)(i)(A)(2)...... light duty vehicle.... 0.1 g/mile.
40 CFR 86.094-9(a)(1)(i)(A)(2)...... light duty truck...... 0.1 g/mile.
40 CFR 86.094-11(a)(1)(iv)(B)....... heavy duty highway 0.1 g/bhp-hr.
40 CFR 89.112(a).................... nonroad (tier, power varies by power range:
tier 1 kW< 8 (hp< 11)... 1.0 g/kW-hr (0.75 g/bhp-hr).
tier 1 8< =kW< 19 0.80 g/kW-hr (0.60 g/bhp-hr).
(11< =hp< 25).
tier 1 0.80 g/kW-hr (0.60 g/bhp-hr).
19< =kW< 37(25< =hp< 50).
tier 2 0.40 g/kW-hr (0.30 g/bhp-hr).
37< =kW< 75(50< =hp< 100).
tier 2 0.30 g/kW-hr (0.22 g/bhp-hr).
75< =kW< 130(100< =hp< 17
tier 1 0.54 g/kW-hr (0.40 g/bhp-hr).
130< =kW< 225(175< =hp< 3
tier 1 0.54 g/kW-hr (0.40 g/bhp-hr).
225< =kW< 450(300< =hp< 6
tier 1 0.54 g/kW-hr (0.40 g/bhp-hr).
450< =kW< 560(600< =hp< 7
tier 1 0.54 g/kW-hr (0.40 g/bhp-hr).
``g'' means grams.
``hp'' means horsepower.
``g/bhp-hr'' means grams/brake horsepower-hour.
``kW'' means kilowatt.
``g/kW-hr'' means grams/kilowatt-hour.
(b) For purposes of paragraph (a):
(1) The term ``introduced'' means any engine added to the
underground inventory of engines of the mine in question, including:
(i) An engine in newly purchased equipment;
(ii) An engine in used equipment brought into the mine; and
(iii) A replacement engine that has a different serial number than
the engine it is replacing; but
(2) The term ``introduced'' does not include engines that were
previously part of the mine inventory and rebuilt.
(3) The term ``introduced'' does not include the transfer of
engines or equipment from the inventory of one underground mine to
another underground mine operated by the same mine operator.
Sec. 57.5070 Miner training.
(a) Mine operators must provide annual training to all miners at a
mine covered by this part who can reasonably be expected to be exposed
to diesel emissions on that property. The training must include--
(1) The health risks associated with exposure to diesel particulate
(2) The methods used in the mine to control diesel particulate
(3) Identification of the personnel responsible for maintaining
those controls; and
(4) Actions miners must take to ensure the controls operate as
(b) An operator must retain a record at the mine site of the
training required by this section for one year after completion of the
Sec. 57.5071 Exposure monitoring.
(a) Mine operators must monitor as often as necessary to
effectively determine, under conditions that can be reasonably
anticipated in the mine, whether the average personal full-shift
airborne exposure to DPM exceeds the DPM limit specified in Sec.
(b) The mine operator must provide affected miners and their
representatives with an opportunity to observe exposure monitoring
required by this section. Mine operators must give prior notice to
affected miners and their representatives of the date and time of
(c) If any monitoring performed under this section indicates that a
miner's exposure to diesel particulate matter exceeds the DPM limit
specified in Sec. 57.5060, the operator must promptly post notice of
the corrective action being taken on the mine bulletin board, initiate
corrective action by the next work shift, and promptly complete such
(d)(1) The results of monitoring for diesel particulate matter,
including any results received by a mine operator from sampling
performed by the Secretary, must be posted on the mine bulletin board
within 15 days of receipt and must remain posted for 30 days. The
operator must provide a copy of the results to the authorized
representative of miners.
(2) The mine operator must retain for five years (from the date of
sampling), the results of any samples the operator collected as a
result of monitoring under this section, and information about the
sampling method used for obtaining the samples.
Sec. 57.5075(a) Diesel particulate records.
(a) Table 57.5075(a), ``Diesel Particulate Recordkeeping
Requirements,'' lists the records the operator must retain pursuant to
Sec. Sec. 57.5060 through 57.5071, and the duration for which
particular records must be retained.
Table 57.5075(a).--Diesel Particulate Recordkeeping Requirements
Record Section reference Retention time
1. Approved application for Sec. 57.5060(c)..... Duration of
extension of time to comply extension.
with exposure limits.
2. Purchase records noting Sec. 57.5065(a)..... 1 year beyond
sulfur content of diesel fuel. date of
3. Maintenance log............ Sec. 57.5066(b)..... 1 year after
4. Evidence of competence to Sec. 57.5066(c)..... 1 year after
perform maintenance. date
5. Annual training provided to Sec. 57.5070(b)..... 1 year beyond
potentially exposed miners. date training
6. Record of corrective action Sec. 57.5071(c)..... Until the
7. Sampling method used to Sec. 57.5071(d)..... 5 years from
effectively evaluate a sample date.
miner's personal exposure,
and sample results.
(b)(1) Any record listed in this section which is required to be
retained at the mine site may, notwithstanding such requirement, be
retained elsewhere if the mine operator can immediately access the
record from the mine site by electronic transmission.
(2) Upon request from an authorized representative of the Secretary
of Labor, the Secretary of Health and Human Services, or from the
authorized representative of miners, mine operators must promptly
provide access to any record listed in the table in this section.
(3) An operator must provide access to a miner, former miner, or,
with the miner's or former miner's written consent, a personal
representative of a miner, to any record required to be maintained
pursuant to Sec. 57.5071 to the extent the information pertains to the
miner or former miner. The operator must provide the first copy of a
requested record at no cost, and any additional copies at reasonable
(4) Whenever an operator ceases to do business, that operator must
transfer all records required to be maintained by this part, or a copy
thereof, to any successor operator who must maintain them for the
Dated: May 23, 2005.
David G. Dye,
Acting Assistant Secretary for Mine Safety and Health.
[FR Doc. 05-10681 Filed 6-3-05; 8:45 am]
BILLING CODE 4510-43-U