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[Federal Register: December 17, 1996 (Proposed Rules)]
[Page 66398-66448]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[[pp. 66398-66448]] Health Standards for Occupational Noise Exposure
[[Continued from page 66397]]
[[Page 66398]]
review of Baughn's findings. Sataloff et al. asserted that the
comparison indicated that workers exhibited more hearing loss when
exposed to continuous noise than from exposures to intermittent noise.
Although research showed that the loss caused by intermittent noise
differs substantially from the effects of continuous noise of the same
intensity, Sataloff et al. did not state an opinion as to which
exchange rate is most appropriate.
Hodge and Price (1978), in their review of damage risk criteria,
summarized that the 3-dB exchange rate was proposed to account for
variations in exposure time to both intermittent and continuous noise
and that the 5-dB exchange rate was proposed to account for the
``beneficial effect of recovery'' during quiet periods between such
exposures. They stated, however, that the sound level would need to
fall below 60 dBA to effect recovery. They concluded that neither the
3-dB nor 5-dB exchange rate fits the hearing loss at all frequencies or
under all conditions and there will be controversy in this area for
many years to come.
Cluff (1982), professor of audiology at Arizona State University,
states that:
* * * while equinocivity (the principle embodied in the 5-dB
doubling rate) may be an applicable basis for determining noise dose
for lower levels of noise, its credibility suffers as the level of
the noise increases above 90 dBA. * * * The only justification for
equinocivity, in lieu of equal energy [3-dB exchange rate], is that
on-the-job exposure to noise will probably be intermittent. * * *
Applying the above logic to very high noise levels [sound levels],
intermittent exposure may be claimed for noise levels of 115 dBA,
for instance, only if the duration of each individual exposure is
substantially shorter than the approximately two minute maximum that
would be allowed under equal energy.
Bies and Hansen (1990) developed an equation fitting a 6-dB
exchange rate to the ISO 1999: 1990(E) data, instead of the 3-dB
exchange rate as presented by ISO. Essentially, they showed that the
mathematical solution fitting an equation to the hearing loss data
contained in ISO 1999: 1990(E) is not unique.
Macrae (1991) published an article which refutes Bies and Hansen's
findings. Macrae studied people with a sensorineural hearing loss at
4000 Hz to determine the progression of the loss in relation to
presbycusis. Macrae's data supported ISO 1999 which uses a 3-dB
exchange rate. Macrae believed that Bies and Hansen erred by assuming
that hearing loss, due to presbycusis and noise exposure, was additive
on an antilogarithmic basis at 4000 Hz. Because the progression of
hearing loss at other frequencies was not studied, Macrae could not
reach any definite conclusions as to the progression of hearing loss at
frequencies other than 4000 Hz.
According to the Committee on Hearing, Bioacoustics, and
Biomechanics of the National Research Council (CHABA) (1993), the data
for specifying an exchange rate were not conclusive.
Compared to steady-state noise data, little data exist on the
effect of intermittent or time varying noise exposure. Depending upon
the length of time of the exposure, an exchange rate of between 0-dB
and 8-dB is appropriate. Each of these single number exchange rates is
valid for a limited set of exposure conditions. Therefore, CHABA did
not recommend an exchange rate. Additionally, CHABA concluded that the
maximum sound level for effective quiet is approximately 80 dBA at most
frequencies.
NIOSH (1995) recommends a 3-dB exchange rate based upon the latest
scientific data. This recommendation represents a change in NIOSH's
position on exchange rate from that included in the 1972 Criteria for
Recommended Standard * * * Occupational Exposure to Noise.
NIOSH presents many reasons for this change in position. In their
1972 criteria document, NIOSH based the recommendation for a 5-dB
exchange rate on earlier recommendations of CHABA (Kryter et al.,
1966). CHABA's 1966 recommendations were predicated on three
postulates, which included--
(1) TTS2 (temporary threshold shift measured two minutes after
cessation of the noise exposure) is a valid predictor of permanent
threshold shift (PTS);
(2) equivalent TTS2's obtained from exposures were equally
hazardous; and
(3) TTS2 is a consistent measure of the effects of a single
day's exposure to noise.
Since that time, NIOSH believes that more recent scientific studies
have proven these postulates to be erroneous. Another assumption that
NIOSH found for justifying the 5-dB exchange rate was that
interruptions will be of ``equal length and spacing so that a number of
identical exposure cycles are distributed uniformly throughout the
day.''
Although NIOSH found that intermittent noise exposure is less
harmful than continuous noise exposure, NIOSH has determined that the
beneficial effects of intermittency which allow for recovery from TTS
are not found in industry today. The quiet periods are too loud and too
short to permit recovery of TTS before the next exposure to harmful
noise.
NIOSH cites field studies by Sataloff et al. (1969), Holmgren et
al. (1971), Johansson et al. (1973), and Institut National de Recherche
et de Securite (1978), to show the beneficial effect of intermittency
of noise exposure in mining and forestry. Studies by NIOSH (1976),
NIOSH (1982), Passchier-Vermeer (1973) and Shaw (1985), not supporting
this finding were also cited. NIOSH, however, concludes that ``the
ameliorative effect of intermittency does not support the use of the 5-
dB exchange rate.''
The Shaw study (1985) supports the 3-dB exchange rate based on the
premise that a 3-dB exchange rate better fits the epidemiological data
on the relationship between noise exposure and hearing loss. Shaw also
criticizes the use of the 5-dB exchange rate because it was based upon
the assumption that a permanent threshold shift (PTS) is related
directly to temporary threshold shift (TTS). Shaw believes that no
researcher has adequately demonstrated a relationship between PTS and
TTS. Furthermore, he states that the 5-dB exchange rate does not take
into account variations in the temporal pattern of exposure.
Suter (1983) conducted a comprehensive review of the literature on
exchange rate. She concluded that the 5-dB exchange rate is under-
protective in many situations and that the 3-dB exchange rate is more
firmly supported by the scientific evidence for assessing hearing
impairment as a function of sound level and duration. Suter, however,
stated that:
The situation becomes more complex when noise becomes truly
intermittent, in other words, when there are large differences
between high and low levels, and levels in between occur rarely. The
studies of forestry workers and miners [Sataloff et al. 1969;
Holmgren 1971; Johansson 1973; and Institute National de Recherche
et de Securite 1978] indicate that the frequent periods of quiet
between noise bursts can in some circumstances, ameliorate the
effects of noise exposure.
Regarding the literature review, Suter explained that the
researchers' findings have been refuted by two NIOSH studies of
intermittently exposed coal miners (NIOSH, 1976) and firefighters
(NIOSH, 1982). In addition, the researchers' studies suffer from
various methodological problems such as inadequate characterization of
exposure, sporadic wearing of hearing protectors, small sample size,
etc. Nevertheless, Suter believed that these studies show a valid
trend, in that the intermittency of exposure can offset the effects of
noise exposure, especially in view of
[[Page 66399]]
some of the animal studies (Ward and Turner, 1982). Suter further
stated that:
The logical consequence of such a trend [intermittent noise
exposure being less hazardous than continuous noise exposure] would
be to allow an adjustment to the maximum permissible exposure limit
for outdoor, intermittent noise exposure. This is by contrast to a
5-dB exchange rate, for which there is virtually no scientific
justification * * *.
Suter suggested using a 3-dB exchange rate along with an adjustment
of 2 dB to the PEL for outdoor noise. She stated that ``The exact
amount of such an adjustment should await clarification by further
scientific evidence.''
According to Sliney (1993), chair of the ACGIH Physical Agents TLV
Committee, (ACGIH) revised its exchange rate from 5-dB to 3-dB, on the
basis that the use of a 5-dB exchange rate is not wise for short
exposure periods. The ACGIH stated that allowable durations for high
sound levels which are permitted with a 5-dB exchange rate are
excessive. In addition, ACGIH believed that, with a 3-dB exchange rate,
an upper limit for the TLV was capped by a 140 dBC impulse peak sound
pressure level. Both the 1971 and 1990 versions of the ISO 1999
standard employ the 3-dB exchange rate.
Evans and Ming (1982) studied five groups of employees in noisy
occupations using personal noise dosimeters which integrated sound
levels based on a 3-dB exchange rate. The noise exposures ranged from
80 dBA to 102 dBA. They used a mathematical model developed by Robinson
and Shipton based upon a 3-dB exchange rate for predicting hearing loss
among exposed workers. Evans and Ming stated that the observed noise-
induced hearing loss (NIHL) of workers in the spinning, weaving, and
bottling industries agreed with those predicted by Robinson and
Shipton's model. The hearing loss of workers in the metal-work
industry, however, tended to be greater than those predicted. The
authors believed that the significant amount of impulse noise
contributing to the noise exposures in this industry explained the
difference. Evans and Ming concluded that the use of Robinson and
Shipton's prediction method is valid for predicting the hearing loss
risk for various noise exposures.
As will be displayed later in Tables III-4 and III-5, the 3-dB
exchange rate is also used by many international communities and
selected branches of the U.S. armed services.
Although occupations in the mining industry are typically exposed
to varying sound levels, most miners are continuously exposed to noise
above 80 dBA. Because the majority of exposures are continuously above
80 dBA, little or no time is available to permit ``recovery time'' from
TTS. Thus, miners experience little recovery from the effects of these
noise exposures. ``Recovery time'' is a basic tenet of the current 5-dB
exchange rate; thus, the Agency has concluded the continuous nature of
noise exposure in the mining industry is more realistically
characterized by the 3-dB exchange rate.
Although the Agency has reached this conclusion, and although there
appears to be a growing consensus supporting the use of a 3-dB exchange
rate among the scientific community, international regulators, and the
U.S. armed services, MSHA has chosen to retain a 5-dB exchange rate for
its proposal because there are significant feasibility implications of
adopting a 3-dB rate--both economic and technological.
With respect to economic feasibility, MSHA conducted a study of the
effect of a 3-dB exchange rate on the measured noise exposure of U.S.
metal and nonmetal miners. The mine inspectors collected measurements
during the course of their regular inspections using personal noise
dosimeters which collected data using 5-dB and 3-dB exchange rates
simultaneously. These data are presented in Table III-2.
Table III-2.--M/NM Samples SUP a Exceeding Specified Sound Levels Collected
by MSHA From May 1995 to October 1995
----------------------------------------------------------------------------------------------------------------
5-dB exchange
rate 3-dB exchange rate
---------------------------------------------------
Sound level (in dBA) Number of
Percent of Number of Percent of
samples
samples samples samples
----------------------------------------------------------------------------------------------------------------
90.......................................................... 491
16.5 1483 49.9
85.......................................................... ...........
........... 2543 85.5
----------------------------------------------------------------------------------------------------------------
SUP a Total of 2974 samples. Two of the boxes in the table do not contain
entries. This is to avoid the potential
for making an inappropriate comparison of values. Direct comparison of
TWA8 values determined with different
thresholds is not appropriate if the TWA8 is less than one of the
thresholds. An example may help to
illustrate the point. A miner exposed to a constant sound field of 85 dBA
for 8 hours would be determined to
have a noise dose of 0%, or a TWA8 of 0 dBA, if a 90 dBA threshold is
used: none of the sound would be counted
in the computation. If the exposure was measured using an 80 dBA threshold,
the dose would be 50%, or a TWA8
of 85 dBA. Contrasting the measures taken with the two thresholds would be
inappropriate in such a case.
The measurements in Table III-2 for a 5-dB exchange rate were made
using a 90-dBA threshold while the 3-dB exchange rate data were
obtained without a threshold. To get a better picture of the impact of
moving from a 5-dB exchange rate to a 3-dB exchange rate if, as
proposed, the Agency adopts an 80-dBA threshold, Table III-3 has been
constructed. The data for the 5-dB exchange rate comes from the
Agency's dual-threshold survey for metal and nonmetal mines, presented
in Table II-11. This also allows for the analysis of data at values
below a TWA8 of 90 dBA, something which is not possible with a 90
dBA threshold. The data for the 3-dB exchange rate come from Table III-
2--switching to an 80 dB threshold does not significantly change the 3-
dB readings in Table III-2.
Table III-3.--Metal/Nonmetal Samples Exceeding Specified Sound Levels at
Different Exchange Rates
------------------------------------------------------------------------
5-dB
------------------------------------------------- 3-dB percent
Sound level (in dBA) Percent
------------------------------------------------------------------------
90..................... 26.9 49.9
85..................... 67.6 85.5
------------------------------------------------------------------------
As indicated in Table III-3 the selection of an exchange rate
substantially affects the measured noise
[[Page 66400]]
exposure. The percentage of miners whose noise exposure would exceed a
PEL set at a TWA8 of 90 dBA (or an LEq,8 of 90 dBA in the
case of a 3-dB exchange rate) increases from 26.9% to 49.9% when the
exchange rate changes from 5-dB to 3-dB. Looking at the numbers another
way, as compared with using a 5-dB exchange rate, using a 3-dB exchange
rate would result in the need to utilize engineering or administrative
controls to limit the exposure of twice as many miners. Moreover, the
engineering controls required would be more expensive since it would
take a more stringent control to bring down, to the PEL, exposures that
double every 3-dB. The table also reveals that to switch to a 3-dB
exchange rate and setting the PEL at an Leq,8 of 85 dBA would
increase the percentage of miners whose exposure is out of compliance
with the PEL from 67.6% to 85.5%.
MSHA has not compiled similar data for coal mining, although the
consequences would be similar. Accordingly, MSHA believes that using a
3-dB exchange rate would have significant implications for the U.S.
mining industry.
With respect to technological feasibility, it is extremely
difficult to reduce the noise exposures to a Leq,8 of 90 dBA using
currently available engineering or administrative noise controls or a
combination thereof. For many pieces of existing equipment it is not
practical to apply engineering controls without seriously compromising
the equipment's operational capacity.
Accordingly, as discussed in part IV of this preamble, moving the
industry to a 3-dB exchange rate may be infeasible at this time.
MSHA believes that the determination of an appropriate exchange
rate is one of the more noteworthy issues in the proposed rule.
Accordingly, MSHA requests further comment and data on this issue. In
particular, MSHA notes that the studies supportive of a 5-dB rate are
generally dated, and requests information about any more current study
supporting that exchange rate.
A-weighting, slow-response
Proposed Sec. 62.120(a)(3)(iv) requires that the instruments used
for measuring noise exposures be set for the A-weighting network and
slow-response (exponential time averaging). This is identical to the
existing MSHA regulations for exposures to non-impulse/impact noise.
OSHA also uses the A-weighting network and the slow-response time for
evaluating exposure to noise.
Weighting networks were designed to approximate the response of the
human ear to tones of equal loudness. The human ear does not respond to
all levels of tones in the same way. At low sound pressure levels
(e.g., 50 dB) the ear discriminates against low-frequency and high-
frequency tones. At higher sound pressure levels (e.g., 90 dB), the ear
no longer discriminates against low- and high-frequency tones. Although
the human ear does not discriminate against low-frequency tones at high
sound levels, the low-frequency tones are less damaging to hearing than
mid-frequency tones.
Several weighting networks have been developed to take these
differences into account: known as A, B, and C. Early researchers
suggested using them all in combination: the A-weighting network when
the sound pressure level was less than 55 dB, the B-weighting network
between 55 and 85 dB, and the C-weighting network for sound pressure
levels exceeding 85 dB (Scott, 1957). Since that time, however,
concensus has developed on the use of the A-weighting network.
Response time, also known as a time constant, refers to the speed
at which the instrument responds to a fluctuating noise.
There are five responses defined in ANSI S1.4-1983, ``Specification
for Sound Level Meters''. They are fast, slow, impulse, exponential,
and peak. The quickest response is the peak response and the slowest is
the slow. Originally the slow response (1000 milliseconds) was used to
characterize occupational noise exposure. This response was used since
it was easier to read the needle deflections on a meter in rapidly
fluctuating noise. For this type of noise the needle deflections using
the fast response (125 milliseconds) were too difficult for the human
eye to follow. ANSI S1.25-1991, ``Specification for Personal Noise
Dosimeters'', prescribes only the slow and the fast responses for
personal noise dosimeters. Many of the older, but not obsolete,
personal noise dosimeters only have the slow response. Furthermore, the
slow response was used for characterizing the noise exposure when most
damage risk criteria were developed.
Many commenters suggested that MSHA adopt OSHA's instrumentation
requirements. This would imply that noise is to be measured on the A-
weighting network and the slow response. However, one commenter
suggested that MSHA use the fast response for evaluating noise
exposure, because ``Use of fast response will result in a more accurate
assessment of employee exposure.''
Prior to the adoption of the A-weighting network to evaluate noise
exposure, the scientific community used more complex methods (e.g.,
octave bands and speech interference levels).
ACGIH (1986) reports that:
* * * Botsford demonstrated that A-weighted levels are as
reliable as octave band levels in the prediction of effects on
hearing in 80% of the occupational noises considered, and slightly
more conservative in 16% of the cases. Passchier-Vermeer and Cohen
et al. similarly demonstrated that A-weighted levels provide a
reasonable estimate of the hazard to hearing in most industrial
environments.
The National Safety Council's Book, Fundamentals of Industrial
Hygiene, Fourth Edition (Plog et al., 1995) states that:
The A-weighted sound level measurement has become popular in the
assessment of overall noise hazard because it is thought to provide
a rating of industrial broadband noises that indicates the injurious
effects such noise has on the human ear.
NIOSH (1972) recommended the continued use of the A-weighted sound
level measurement in its criteria document for a recommended standard
on occupational noise exposure. In this criteria document they state:
As a result of its simplicity and accuracy in rating hazard to
hearing, the A-weighted sound level was adopted as the measure for
assessing noise exposure by the American Conference of Governmental
Industrial Hygienist (ACGIH) and by Intersociety Committee
consisting of representatives from the American Academy of
Occupational Medicine, American Academy of Ophthalmology and
Otolaryngology, ACGIH, Industrial Hygiene Association, and the
Industrial Medical Association. A-weighted sound level measurement
was adopted by the U.S. Department of Labor as part of the
Occupational Safety and Health Standards and by the British
Occupational Hygiene Society in its Hygiene Standards for Wide-Band
Noise.
In reviewing the procedures for exposure measurement in regulations
and codes of practice (mandatory or recommended) from the EEC, the ISO,
the international community, and selected branches of the U.S. armed
services (see Tables III-4 and III-5), MSHA found that there is general
agreement among these groups that measurements be taken using the A-
weighting network and most agree to use the slow-response instrument
settings. ISO 1999 (1990) recommends that if sound level meters are
used to measure noise exposure, then the instrument should be set on A-
weighted, fast-response. In Australia, integrating sound level meters
should be
[[Page 66401]]
set to fast-response while other sound level meters should be set to
slow-response.
The scientific community and most regulatory entities around the
world accept the A-weighting network and slow-response time as
appropriate measurement parameters for characterizing noise exposures.
These parameters have been used by the U.S. Department of Labor, since
the adoption of the Walsh-Healey Public Contracts Act noise regulations
of 1969.
Based upon comments and the good correlation between hearing loss
and A-weighted noise exposures, MSHA proposes to continue using A-
weighting and slow-response when determining a miner's noise exposure.
Action Level
Proposed Sec. 62.120(b) establishes an ``action level'' at a
TWA8 of 85 dBA.
The need for an action level reflects two facts: 1) there is a
significant risk of material impairment to miners from a lifetime of
exposure to noise at this level; and 2) the Agency believes it may not
be feasible at this time to lower the PEL to this level, since that
would require that mine operators use all feasible engineering and
administrative controls to reduce noise exposures to this level.
The proposal would require that all miners exposed above the action
level be provided special instruction in the hazards of noise and
protective methods. The training is to be provided annually for as long
as exposure exceeds the action level. (The nature of this instruction,
how it is to be provided, and how it can be coordinated with other
required miner training are subjects discussed in connection with
proposed Sec. 62.130.)
If a miner's exposure exceeds the action level but is below the
PEL, an operator will also be required to enroll a miner whose exposure
exceeds the action level in a hearing conservation program (HCP). While
enrollment in the HCP would require the operator to make annual
audiometric testing available to the miner, miners exposed to noise
below the PEL would have the right to decline taking any annual
audiometric testing. MSHA's proposed testing requirements related to
the action level are consistent with those of the OSHA HCP. The
requirements for such testing are discussed in connection with proposed
Sec. 62.140, audiometric testing program.
MSHA is seeking comments on how to minimize the burden on mine
operators of providing audiometric examinations for those miners with
only a temporary attachment to the mining work force (e.g. summer
employees), while recognizing the importance of detecting and tracking
hearing loss among those who switch jobs.
In addition, the operator must provide properly fitted hearing
protection--before the initial hearing examination, if a significant
threshold shift in hearing acuity is detected, and at any other time
upon miner request. Should it take more than 6 months to provide the
initial hearing examination because of the need to wait for a mobile
test van, or should a significant threshold shift in hearing acuity be
detected, the operator would also be required to ensure that the miner
wears the hearing protection--even if the miner's noise exposure
remains under the PEL. (A discussion of the time frames for audiometric
tests, and the use of mobile test vans, is included in the discussion
of proposed Sec. 62.140, audiometric testing program. The definition of
a significant threshold shift is discussed in connection with proposed
Sec. 62.160, evaluation of audiogram.)
An action level currently exists under OSHA but would be new to the
mining industry. As discussed herein, MSHA proposes to build upon the
requirements which have been used by OSHA while giving due regard to
implementation approaches appropriate to the circumstances of the
mining community.
Comments on Action Level
Several commenters recommended an action level of 85 dBA for
triggering the requirements of an HCP.
Many of those who commented in response to MSHA's ANPRM discussed
hearing protection and audiometric testing. Some of these comments shed
light on the relationship and comparative benefits of these approaches.
Some commenters supported the use of hearing protectors as an
integral part of an HCP, while other commenters recommended that
hearing protectors be supplied even when not required so as to afford
greater protection. Other commenters expressed three common concerns
over the use of hearing protectors--
(1) difficulty with speech communication and the masking of warning
signals (roof talk, backup alarms, etc.), especially for those miners
with a pre-existing hearing loss;
(2) miner acceptance, including comfort; and
(3) personal hygiene.
The latter two issues of miner acceptance and personal hygiene are
discussed in detail in the sections of the preamble entitled Selection
of hearing protectors and Maintenance of hearing protectors,
respectively (in connection with proposed Sec. 62.125).
Several commenters suggested alternatives for dealing with
communication problems associated with the use of hearing protectors by
those with a hearing loss or in the presence of background noise. These
alternatives included use of a ``buddy'' system, visual warnings,
communication headsets, vitro-tactile warning systems, flat-frequency
response hearing protectors, and notch-amplification earmuffs.
Many commenters specifically mentioned the problem of miner
acceptance of hearing protectors. One of these commenters stated: ``* *
* there is anecdotal reporting to suggest that miners resist wearing
hearing protective devices.''
One commenter stated: ``Another [usage] problem may be the use of
muffs with additional safety equipment, e.g. hard hats and safety
glasses, that may be required for use by the miners.'' Other commenters
either had no problems with hearing protectors or felt that any
problems could be overcome with the proper training.
In addition to the comments received in response to MSHA's ANPRM on
this issue, several researchers and organizations have taken a position
in regard to the use of hearing protectors.
Shaw (1985) reviewed much of the same literature as OSHA when the
1983 Hearing Conservation Amendment was prepared. Shaw's study supports
requiring both hearing protectors and an HCP for exposures exceeding 85
dBA.
In Communication in Noisy Environments (Coleman et al., 1984), the
authors state that:
* * * excessive attenuation needs to be minimized and the
frequency response of the protector is of particular importance in
this respect. * * * (S)everal authors * * * suggest that a protector
which passed relatively more low frequencies could increase remote
masking and produce potential communication difficulties for some
members of the population. This effect has been demonstrated to be
of practical significance for coal mining conditions * * * A flat
frequency response for a protector is necessary to counter the
effect.
Michael (1991) recommends that the hearing protector attenuate the
noise with an adequate margin of safety; however, the hearing protector
should not unnecessarily reduce important aural communications. To
accomplish this goal, the hearing protector's attenuation
characteristics should be matched to the noise exposure spectra as
close as possible. This way the hearing protector will minimally change
[[Page 66402]]
the worker's perception of the noise. Michael also points out that
overall noise reduction achieved by a hearing protector can be
substantially influenced by the spectra of the noise.
Chiusano et al. (1995) reported that a communication headset,
without gain limiters, can expose communication workers to hazardous
sound levels. The noise exposures ranged from 79.9 dBA to 103.8 dBA,
with the average exposure being 87.0 dBA. Furthermore, the peak sound
pressure levels ranged from 119.2 dB to 148.8 dB, with the average
being 140.8 dB. Some recommendations presented by the authors to
control the noise exposure were to include peak clipping, bandwidth
limitations, signal compression, computerized gain control, and
improving the signal to noise ratio.
In the CAOHC Manual, Miller (1985) states that many authorities
consider OSHA's requirement on who must wear hearing protectors to be
``unwieldy.'' This manual states further that ``A more practical and
workable approach is to require all workers exposed to levels of 85-dBA
or higher to use PHPD's [personal hearing protection devices]
regardless of whether the audiograms show an STS.''
According to Suter (1986): ``Because hearing loss may occur in
people chronically exposed to levels of 85-dBA and above, it is wise to
use protectors that attenuate to 85-dBA in all cases.''
The U.S. Armed Services, as well as the European Economic Community
and other foreign countries, require the use of hearing protection when
sound levels exceed 85 dBA.
General Discussion of Action Level and Requirements
The Agency has concluded that there is a significant risk of
material impairment to miners from a lifetime of exposure to noise at a
TWA8 of 85 dBA. In mining, the first line of defense against risks
has always been training. Accordingly, the proposal provides for annual
instruction--to enhance awareness of noise risks, operator
requirements, and available controls. This training would be required
for any miner whose exposure is above the action level.
MSHA's requirements for this training, and a discussion of how it
can be coordinated with existing training requirements, are in proposed
Sec. 62.130. As discussed below in connection with that section, MSHA
received many comments in response to its Advance Notice of Proposed
Rulemaking that supported the value of an annual training requirement.
Studies have shown that the effectiveness of a hearing protection
program is highly dependent on the proper use of hearing protectors and
the commitment of both management and employees, and annual training is
critical to reinforce both the knowledge and commitment.
The Agency believes it may not be feasible at this time to require
mine operators to reduce noise exposures to a TWA8 of 85 dBA. A
detailed discussion on this point can be found in Part IV of this
preamble. Thus, for exposures between a TWA8 of 85 dBA (the action
level), and a TWA8 of 90 dBA (the PEL), the available tools to
supplement training are limited to hearing protectors and annual
audiometric examinations.
Hearing protectors offer only limited noise protection. As
discussed in detail in connection with proposed Sec. 62.125, studies
indicate that hearing protectors may provide significantly less than
their rated protection under actual mining conditions. Nevertheless,
MSHA believes that if hearing protection is properly utilized--that is,
if the requirements under proposed Sec. 62.125 are implemented--they
generally can be relied on to provide at least 5 dBA attenuation, and
thus could realistically protect the majority of miners whose noise
exposure falls between the action level and the PEL.
The comments that MSHA received in response to its ANPRM, however,
suggest that ensuring the protectors are properly fitted, maintained
and utilized may continue to prove difficult--even once the proposed
new standards in this regard (see the discussion of proposed
Sec. 62.125) are taken into account. For example:
(1) The mining environment presents hazards which require a miner
to be aware of his/her surroundings. Many underground miners claim that
the use of hearing protectors interferes with their ability to hear
warning signals or roof talk. This interference may be particularly
pronounced among miners who already have a significant degree of
hearing loss, and such miners may justifiably be reluctant to use
hearing protectors;
(2) Hearing protectors (earmuffs and earplugs) are difficult to
keep clean in the mining environment which can lead to irritation or
infection of the ear(s);
(3) Earmuffs are often uncomfortable when worn in hot environments
(e.g., surface mines during periods of extreme heat or some deep
underground mines);
(4) Hearing protectors experience a degradation of attenuation when
moved from their original position. This condition can occur often when
hearing protectors are worn by a miner operating vibrating equipment
(e.g., pneumatic drills, continuous mining machines, mobile equipment),
wearing certain types of personal protective gear (e.g., safety
glasses, hardhats, respirators, welder's hood, etc.), or sweating;
(5) The effectiveness of hearing protectors is highly dependent
upon proper fit and use by the miner. While the amount of protection
afforded by engineering controls can be easily measured, the
attenuation of hearing protectors under actual working conditions can
only be estimated; and
(6) Generally, hearing protectors are not effective in reducing low
frequency noise. As most mining machinery emits predominantly low
frequency noise, the use of hearing protectors may have a negligible
effect in reducing the overall sound level.
To alleviate these problems, both operators and miners must be
committed to working through individual concerns about hearing
protection. MSHA believes that the best way to facilitate this
process--at exposure levels between the action level and the PEL, and
with a few exceptions--is to have operators provide instruction and
make suitable hearing protectors available to miners upon request. If
protectors are requested, they would have to be provided in accordance
with the requirements of Sec. 62.125--i.e. a choice of plug or muff
type, properly fitted, maintained, and replaced under certain
conditions. An operator would generally not, at such exposure levels,
have an obligation to enforce the use of hearing protection. MSHA
believes that the combination of knowledge, availability, and properly
selected, fit and maintained equipment may be the best way to encourage
hearing protector use.
MSHA would require an operator to provide a miner with a hearing
protector while awaiting a baseline audiometric examination; but with
the exception noted below, the operator would not have to enforce the
use of the protector as long as the miner's exposure does not exceed
the PEL.
In two cases, however, MSHA proposes to require operators to
enforce hearing protector use at exposures below the PEL. The first
case would be in the event a miner exposed above the action level has
to wait more than 6 months for a baseline audiometric examination. As
noted in proposed Sec. 62.140, the baseline examination is normally to
take place within 6 months of a determination that a miner is at risk
because his or her exposure exceeds the action level; however, the time
frame can be extended for an additional 6 months if the operator has to
wait for a
[[Page 66403]]
mobile test van. In such cases, the miner is exposed to harm for an
extended period of time without the benefit of audiometric test data,
and MSHA believes it would be appropriate to require protection to be
worn. This is the approach taken under OSHA's noise requirements.
In addition, an operator would be obligated to ensure the miner
uses provided hearing protection when audiometric examinations indicate
a significant threshold shift (STS) in hearing acuity has occurred and
the miner's exposure exceeds the action level. (The evaluation of
audiograms, and the determination of whether or not there is an STS, is
the subject of proposed Sec. 62.160.) MSHA believes that once there is
evidence from the tests that the miner is incurring hearing loss, it is
appropriate to require that hearing protectors be worn as long as
exposure exceeds the action level.
Annual audiometric examinations cost more than providing hearing
protection--but as already recognized by many in the mining industry,
and all the industries which operate under OSHA's requirements, such
examinations provide important information, especially in an
environment in which hearing protector use has the problems noted
previously. The act of enrolling miners in a ``hearing conservation
program'' (HCP) can help emphasize to those individuals that they
should pay more attention to the training and available controls. It
also helps miner representatives, operators, and MSHA focus available
resources on those miners who have actually suffered an STS at lower
noise exposures. While MSHA is not proposing to require operators to
compel miners to take the annual examinations at exposure levels below
the PEL, and expects that many miners may be reluctant to take
examinations out of concern about how the information would be used,
MSHA anticipates that over time the required training would lead to
growing use of such examinations within the mining industry. (MSHA's
preliminary RIA assumes only limited participation at such exposure
levels during the initial years of the rule's implementation.)
Participation in an HCP
MSHA has no standards addressing hearing conservation plans or
programs in its existing metal and nonmetal regulations. However, an
indeterminate number of mines have voluntarily established HCP's. MSHA
estimates that 5% of small mines, and 20% of large mines, have such
programs.
Existing MSHA coal noise standards require mine operators to submit
``* * * a plan for the administration of a continuing, effective
hearing conservation program,'' within 60 days following the issuance
of a notice of violation [citation] for subjecting a miner to a noise
exposure exceeding the PEL. This plan must include provisions for pre-
employment and periodic audiograms. The regulation, however, does not
specify the procedures nor the time frame for obtaining these
audiograms. Additionally, due to coal's policy of considering hearing
protector attenuation in determining compliance with the PEL, few
miners are found overexposed.
OSHA's noise standard requires that all employees exposed above the
action level (TWA8 of 85 dBA) be enrolled in an HCP. OSHA's HCP
requirements include provisions addressing exposure assessment,
training, audiometric testing, hearing protectors, notification, and
recordkeeping.
Several commenters recommended requiring an HCP whenever a miner's
exposure exceeds a TWA8 of 85 dBA, or equivalently a noise dose of
50%.
Under MSHA's proposal, participation in an HCP would be provided by
the mine operator at no cost to the miner. OSHA also specifies that
audiometric testing and hearing protectors be provided at no cost to
the employees. MSHA intends that the audiometric testing be given
during normal working hours (on-site or off-site) and that miners
participating in these activities receive wages for the time spent in
their involvement. If the audiometric testing is provided off-site,
MSHA intends the mine operator to compensate the miners for the
additional costs, such as mileage, meals, and lodging, that they may
incur.
Elements of an HCP
Some of the elements often considered to be part of an HCP are
handled through separate, free-standing requirements under MSHA's
proposal. These include hearing protection and training, and an
employer's obligation to evaluate the noise to which miners are exposed
to determine if specified levels are exceeded. Accordingly, the
proposal uses the term HCP to refer essentially to annual audiometric
testing and required follow up examinations and actions.
Under OSHA's noise standard, the elements of an HCP include:
(1) monitoring employee noise exposure;
(2) wearing hearing protectors;
(3) education and training; and
(4) audiometric testing and medical evaluation.
In its ANPRM, MSHA requested information concerning the elements
which would be appropriate for inclusion in an HCP for mining. MSHA
received numerous comments concerning this issue. Of these, many
supported MSHA's adoption of HCP requirements similar to OSHA's,
including:
* * * Assessment, monitoring, engineering and/or administrative
controls, hearing protective devices, employee education,
audiometric testing, interpretation of audiometric tests and follow-
up, and appropriate record keeping.
Although there was a consensus among commenters on the elements of
an HCP, there was considerable variation in the substantive aspects of
these elements. Commenters ranged from wanting more performance
oriented requirements to wanting more specific requirements with fewer
exceptions than in the existing OSHA rule.
One commenter wanted ``* * * a more stringent program than the
present OSHA HCP * * *''. Another felt that no program should be
implemented until ``* * * sufficient evidence and testing demonstrates
a need for the program to protect the hearing of miners.'' Another
commenter believed that audiograms were a needless expense, but that
hearing protectors should be required for all miners exposed to
hazardous sound levels. Several commenters believed that HCP's were of
no value, stating ``Our experience with HCP's indicates they are wasted
bureaucratic red tape and present no benefit to the employees.''
``Guidelines for the Conduct of an Occupational Hearing
Conservation Program'' (1987) developed by the American Occupational
Medical Association's Noise and Hearing Conservation Committee of the
Council on Scientific Affairs presents the basic elements of an HCP.
They recommend that each program include: (1) measurement of exposure;
(2) engineering controls; (3) use of hearing protectors; (4)
audiometric testing and medical evaluation; (5) education and training;
(6) assessment of program effectiveness; and (7) management support.
MSHA agrees with the majority of the commenters to the ANPRM.
However, as noted, MSHA proposes to require some of these elements
through free-standing requirements. Accordingly, the proposal uses the
term HCP to refer essentially to annual audiometric testing and
required follow up examinations and actions. Overall, the requirements
of MSHA's proposal are generally
[[Page 66404]]
consistent with OSHA's current HCP requirements and with the
requirements of the U.S. armed services and the international
community.
MSHA reviewed HCPs in effect at a variety of organizations. The
HCPs consist mainly of monitoring employee noise exposure, controlling
the noise, training employees, and conducting audiometric testing. The
Agency believes that when engineering and administrative controls are
not able to reduce a miner's exposure to within the PEL, annual
audiometric testing and medical evaluation would enable mine operators
and miners to take proper precautions to identify early hearing loss
and thereby prevent further deterioration of hearing. This is discussed
in more detail in those sections of the preamble reviewing the proposed
HCP requirements (proposed Sec. 62.140 et. seq.).
Effectiveness of HCP's
Although many commenters to MSHA's ANPRM stated that an HCP is
needed, only a few commenters specifically addressed the effectiveness
of an HCP.
One commenter referenced a study (ANSI, 1990; Royster and Royster,
1988) which indicated that the HCP at five out of 17 companies, or less
than 30%, could be considered effective/adequate. This inadequacy,
however, could be attributed to a lack of commitment by the companies
in carrying out all of the necessary components of the HCP. This study
found that, for the HCP to be successful, it is critical that a single
individual have control over the program and its implementation.
Furthermore, management must make a commitment to ensure that the
program is fully implemented.
Another commenter, representing nonmetal mining companies,
indicated that its members have not experienced large numbers of claims
for hearing loss and this may be a reflection of program effectiveness.
In addition to the above comments, MSHA reviewed several studies
regarding the effectiveness of HCP's. Villeneuve and Caza (1986)
reported on the HCP for a Canadian mining company. Under this HCP,
miners undergo audiometric evaluations, receive training, and wear
hearing protectors. After ten years, the incidence of workers'
compensation claims for hearing loss has diminished.
After obtaining audiometric data from three Ontario employers who
had HCP's, Abel and Haythornthwaite (1984) investigated the progression
of NIHL. Workers for the first employer (public utility) had their
maximum hearing loss between 2000 and 6000 Hz. Further, 78% of the
workers who reported never wearing their hearing protectors experienced
25 dB of hearing loss at 4000 Hz. For those workers who wore their
hearing protectors at least half of the time, 38% had the same degree
of hearing loss.
At the second employer (mining company) about half the drillers
incurred a hearing loss of 1 dB per year or more at 4000 Hz. Motorman
chute blasters incurred an average change of hearing of a little over 1
dB per year. This compares to a hearing loss of 0.5 dB per year for the
control group. Further, in subjects who were over 50 years of age,
100%, 88% and 38% of the drillers, the motorman chute blasters, and the
controls respectively had a hearing loss that exceeded 25 dB at 4000
Hz.
Finally, workers at a foundry and steel mill showed a 0.13 dB per
year hearing loss at 1000 Hz and 1.3 dB per year at 4000 Hz. Their
hearing loss was similar to the miners.
Abel (1986) reported on the progression of NIHL among three groups
of workers, including miners. All noise-exposed workers had exposures
exceeding 85 dBA and were enrolled in an HCP. One requirement of the
HCP was mandatory use of hearing protectors. At 4000 Hz, the noise-
exposed workers lost their hearing acuity at 1.5 dB per year compared
to 0.5 dB per year for the control group, who were office workers.
Despite mandatory use of hearing protectors, most workers in the
Abel study admitted to wearing their hearing protectors less than 50%
of the time. Further, many modified their hearing protectors to provide
greater comfort. Many of the modifications had a deleterious effect on
the attenuation.
Gosztonyi (1975) reported on his evaluation of an HCP at a large
manufacturing plant. The study covered a 5-year period (1969-1974)
shortly after the passage of the Walsh-Healey Public Contracts Act
noise regulations. The study covered 213 employees with a median age of
43 years. The workers were divided into three groups based on their
noise exposure. These were: (1) 71 office workers exposed to sound
levels of 50 to 70 dBA; (2) 71 workers in the machine shop exposed to
sound levels of 80 to 85 dBA; and (3) 71 workers (wearing hearing
protectors) in the chipping and grinding areas of the iron and steel
foundry exposed to sound levels of 100 to 110 dBA. Gosztonyi found
that, over a 5-year period, the hearing loss incurred by workers in
group (3) were no greater than the losses exhibited by the other groups
at each frequency, regardless of the baseline hearing thresholds. He
concluded that an HCP (consisting of periodic noise exposure
assessments, annual audiometric testing, and the mandatory use of
hearing protectors) instituted when noise exposures exceed a hearing
conservation criterion of approximately 90 dBA adequately protects the
hearing of noise-exposed workers.
Pell and Dear (1989) reported the following:
Two longitudinal studies of changes in hearing threshold levels
and one study of the prevalence of hearing impairment in noise
exposed and non-exposed workers have clearly indicated that DuPont's
hearing conservation program has been effective in preventing
occupationally noise-induced hearing loss [NIHL].
Several reports on the effectiveness of DuPont's HCP have been
published. DuPont's HCP requires the wearing of hearing protectors in
high noise areas, audiometric testing, and monitoring of noise
exposure. In the first study Pell (1972) showed, via a retrospective
study, that the hearing of workers was being protected. The hearing
levels of workers in high noise areas were compared to the hearing
levels of workers in quieter areas (below approximately 90 dBA). Both
groups of workers had comparable hearing levels at frequencies between
500 and 2000 Hz. At higher frequencies the median hearing level of
quieter area workers was slightly better than the median hearing level
of high noise area workers. Although the differences were statistically
significant, the author believed that the small differences lacked
practical importance. Moreover, the difference was much less than the
hearing loss which occurred due to presbycusis and other non-
occupational factors. Comparing the results to a study published by
Nixon and Glorig (1961) on unprotected workers, Pell concluded that the
DuPont workers experienced much less hearing loss.
Later, Pell (1973) published the initial results of a 5-year
longitudinal study on the same workers. The sound level to which
workers were exposed in the quiet areas could approach 90 dBA, but most
exposures were between 50 and 70 dBA. The workers in the highest noise
areas were required to wear hearing protectors and most of the workers
in the moderate noise areas chose to wear hearing protectors. A
comparison of workers' hearing levels at 3000, 4000, and 6000 Hz
revealed that there was no increased hearing loss among workers who
wore hearing protectors in high noise areas versus the workers in the
quiet areas. The researcher concluded that:
[[Page 66405]]
The analysis of changes in hearing threshold levels over a 5-
year period has clearly indicated that persons who work in areas
where noise levels (sound levels) exceeded 90 dBA showed hearing
losses that were no greater than those experienced by persons who
worked in areas where the noise levels (sound levels) were less than
90 dBA. It is evident, therefore, that a hearing conservation
program in which the hearing conservation criterion is approximately
90 dBA can successfully protect the hearing of noise-exposed
workers.
Pell believed that his study confirmed the earlier conclusion that
DuPont's HCP was effective in preventing occupational hearing loss.
Pell emphasized, however, that this study cannot reveal the effects of
these sound levels on hearing acuity but is intended only to evaluate
the effectiveness of the HCP. The third study is a continuation of the
second study. In this study, Pell and Dear (1988) evaluated the
effectiveness of DuPont's HCP over 20 years. However, the study did not
involve the same workers over the entire time frame for many reasons.
Furthermore, the researchers divided the workers into three categories:
workers exposed to noise under 85 dBA; between 85 to 94 dBA; and 95 dBA
or higher. The mean differences, over a 3-year period between workers
in noisy (over 85 dBA and wearing hearing protectors) and quiet areas,
were small. Evaluating the prevalence of hearing impairment using the
AAO-HNS 1979 definition showed that the high noise areas had slightly
higher prevalence rates of hearing impairment. After adjusting for
presbycusis, only 7.1% of the workers in the high noise areas developed
a hearing impairment. Pell and Dear concluded that presbycusis was by
far the major factor in developing a hearing impairment. Furthermore,
independent clinical evaluations of the non-presbycusis cases revealed
that socioeconomic factors, (e.g., differences in off-the-job noise
exposures and otological disease), may account for much of the excess
hearing impairment of the noise-exposed workers. Pell and Dear
attributed the effectiveness of DuPont's HCP to educating the workers
to the hazards of noise, hearing protector fitting, and supervision.
Because of these components, DuPont workers received greater noise
reduction from foam earplugs than did workers in other industries. Pell
and Dear believe that effective use of hearing protectors is the
overwhelming factor in approaching avoidance of problem hearing loss.
In addition, Pell and Dear believe that employees exposed above 90 dBA
are better protected by using appropriate hearing protectors rather
than implementing engineering controls to reduce the noise to 89 dBA or
even 84 dBA.
Savell and Toothman (1987) studied the HCP at a factory. The
workers whose time-weighted average noise exposures ranged from 86 to
103 dBA were required to wear hearing protectors as a condition of
employment which was strictly enforced. These workers were employed
between 8 and 12 years. Only the employees with more than 25 months off
the job during the course of the study were excluded in order to obtain
a large sample (265 workers). The group mean hearing levels from the
latest audiograms were compared to the initial audiograms. Savell and
Toothman did not find any significant change in hearing acuity over the
course of the study. Therefore, they concluded that mandatory use of
hearing protectors in an HCP can protect the hearing acuity of workers.
Bruhl and Ivarsson (1994) conducted a longitudinal study of the HCP
at an automobile stamping plant over a 15-year period. The researchers
evaluated workers' hearing levels over the frequency range of 2000 to
8000 Hz. Workers' hearing levels were compared to the hearing levels of
a ``highly screened'' non-noise exposed male population. For sheet
metal workers, the HCP reduced the noise-induced permanent threshold
shift. Bruhl and Ivarsson concluded that the HCP, which included
effective use of hearing protectors and reduction of sound levels, can
eliminate occupational NIHL.
Franks et al. (1989) examined the hearing conservation records of a
large printing company with multiple facilities. They examined the
records for factors associated with the development of an STS. Franks
et al. indicated that ``* * * statistically significant factors
associated with Standard Threshold Shift [STS] were from medical and
non-occupational noise exposure histories, and not occupational noise
exposure.'' In other words, the HCP was effective since the hearing
loss developed by the workers was from non-occupational exposures.
Moretz (1990), reporting on the work of the ANSI S12.12 working
group, stated that ``A pilot analysis of industry's audiometric data
found that fewer than 20 percent of the programs [HCP's] are
effective.'' Moretz further reported that Alice Suter, a member of this
ANSI working group, had stated that ``the actual percentage of
companies with effective programs is probably even lower * * *,''
because the ANSI working group had looked at data from relatively large
companies. Suter thought that smaller companies are less likely to have
the resources necessary to operate an effective HCP.
The National Institutes of Health (NIH), in its Consensus Statement
on Noise and Hearing Loss (1990), states that ``many existing hearing
conservation programs remain ineffective due to poor organization and
inadequately trained program staff.''
Although evidence indicates that a properly supervised and operated
HCP can provide effective protection, in many instances, HCP's have
failed due to the lack of necessary supervision and adherence to proper
procedures and principles. Furthermore, the studies which showed HCP's
to be effective were mainly of short term durations (five years or
less). There is a lack of evidence that long term HCP's protect the
hearing acuity of workers. Pell and Dear's 20 year study (1988) was in
actuality two shorter longitudinal studies covering a five-year period
at the beginning of the study and a three-year period at the end. In
both of these shorter studies the hearing level of the participants did
not change at a rate different from the non-noise exposed controls.
The two other long-term studies, Bruhl and Ivarsson (1994) and
Bruhl et al. (1994) demonstrated that HCP's were effective in reducing
noise-induced permanent threshold shift. At the plant both engineering
noise control and hearing protectors were utilized to reduce worker's
exposure to noise. Therefore, these studies indicate engineering noise
control is a necessary component of an effective long-term HCP.
Rink (1996) studied the hearing loss of workers enrolled in HCPs.
Between 1991 and 1995 nearly 590,000 audiograms were given. During the
years the percentage of STSs decreased each year--from 4.69% to 1.22%.
Further, Rink reported that about 50% of the STS consistent with noise
exposure were persistent (confirmed STSs). The remainder were not
permanent. Rink concluded that aggressively adhering to and enforcing
the hearing conservation policies proposed by OSHA in 1983 can reduce
and effectively control NIHL.
Many of the above studies indicate that an HCP can be effective in
preventing hearing loss, but only if management and workers strictly
adhere to its requirements. Several of these studies also concluded
that engineering controls were a necessary part of an effective HCP.
This is not inconsistent with MSHA's conclusions about the
[[Page 66406]]
importance of commitment by both operators and miners.
Evaluation of HCP Effectiveness
MSHA has not included a methodology or a requirement for mine
operators to test the effectiveness of their HCP's. Currently, both
MSHA's Coal and OSHA's noise standards require an effective HCP, but do
not specify a procedure for evaluating the effectiveness of the
program. Further, Metal and Nonmetal's noise standard has no
requirement for an HCP.
In its ANPRM, MSHA also requested information concerning
appropriate methods or requirements for evaluating the effectiveness of
HCP's. One commenter felt that evaluation criteria are unnecessary and
that the HCP is effective if exposures are reduced. Another commenter
stated that uniform evaluation criteria have not been adopted. Another
suggested that NIOSH be given the task of evaluating the effectiveness
of HCP's for the mining industry.
A number of commenters believed that it was essential for MSHA to
address procedures for evaluating the effectiveness of HCP's. Several
of these commenters suggested that MSHA monitor the activities of the
ANSI S12.12 Working Group for Evaluation of HCP's and consider using
the guidelines established by this group, once they were finalized.
ANSI has published a draft standard, ANSI S12.13-1991 Audiometric
Database Analysis (ADBA), which describes techniques for evaluating the
effectiveness of the HCP's.
Adera et al. (1993) studied the effect of using ADBA to determine
the effectiveness of a utility company's HCP which had 2,317
participants. The hearing acuity of the utility workers was compared to
the hearing acuity of tobacco company employees (control population).
The tobacco company employees were one of the control populations used
in developing the draft ANSI standard S12.13-1991. The control
population's noise exposure was approximately 87 dBA and they wore
hearing protectors consistently. While the ADBA method deemed the HCP
acceptable, epidemiological techniques showed the workers to be at risk
of developing a hearing loss. The age-adjusted risk of developing a
hearing loss was 2.3 times that of the control population.
Simpson, Stewart, and Hecksel (1992) studied HCP's at 28 small
companies representing 2,183 employees of which 865 qualified for ANSI
analysis. The researchers concluded that companies with less than 100
employees may have difficulty in meeting ANSI S12.13-1991 data
requirements for more than two consecutive years of data analyses due
to employee turnover and absenteeism. Sample sizes smaller than 30
employees are likely to be more sensitive to outlier scores. Smaller
sample sizes were also more likely to be rated marginal or unacceptable
due to biasing effects of sample size. For 1990, the percent of STS's
ranged from 0% to 3.8% at the individual plants. The rate of STS's
across all 28 plants was 1.5%.
Simpson, Stewart and Kaltenbach (1994) investigated early
indicators of HCP performance. A total of 27,047 employees (3,245
controls and 23,802 subjects) in 21 HCP's were included in the study.
The rate of STS in the control groups ranged from 2.5 to 5.7% while the
exposed groups had a rate between 4.6 and 28%. Comparing the incidence
of STS's with ANSI S12.13-1991 indicators, the researchers concluded
that the incidence of STS's was as good as the ANSI test criteria as an
early indicator of the effectiveness of an HCP from the first two
audiograms.
NIOSH (1995) recommended a simple method of determining the
effectiveness of an HCP. According to NIOSH, if less than 5% (1 out of
20) of the noise-exposed workers enrolled in an HCP incur an
occupationally-induced STS, the HCP is deemed effective. According to
NIOSH, this method should be used to continually monitor the results of
audiometric testing to indicate the effectiveness of the HCP before
many individuals incur permanent shifts in hearing acuity.
While MSHA recognizes that the ADBA technique may be promising, the
Agency is concerned that it may not be practical for the majority of
mine operators. The ADBA technique may not be applied reliably to
populations of fewer than 30 individuals and about 90% of the 15,000
mines under MSHA's jurisdiction employ less than 30 miners. Even if
every miner was placed in an HCP, regardless of noise exposure, less
than 10% of the mines could consider using the ANSI draft ADBA
procedures to evaluate their HCP. ADBA analysis also may not be
appropriate if the workforce being analyzed is not stable, exhibiting a
high turnover rate. MSHA has determined that this may be the case for
many small mines which operate seasonally, are portable, or change
geographic locations. Currently, the annual turnover rate in mining
ranges from 2% in large coal mines to 11% in small metal and nonmetal
mines.
In addition, ADBA requires several years of data before the
analysis can be conducted. Consequently, ADBA cannot be used to
immediately determine the effectiveness of an HCP unless audiograms
were collected prior to the effective date of the rule.
Finally, existing procedures for conducting ADBA call for the use
of audiograms taken without observing a quiet period. Both OSHA's
existing standard and this proposal require a 14-hour quiet period
before conducting a baseline audiogram. These standards, however, do
not address a quiet period for annual audiograms, leaving the choice to
the employer or the mine operator. Consequently, where a quiet period
is used, those audiograms could not be used in conducting ADBA.
MSHA also is concerned that the statistical methods employed by
ADBA require the use of a computer, which many small mine operators may
not have. Consequently, many mine operators may need to employ outside
consultants to conduct this analysis. Because the ADBA techniques are
relatively new, a sufficient number of consultants, who fully
understand and can utilize this analytical technique, may not be
available. Despite the problems with ADBA analysis for the mining
industry, MSHA recognizes that it may be a valuable tool for
identifying and correcting problems in an HCP before an STS occurs.
MSHA does not wish to discourage mine operators from using this
technique.
The analysis of an HCP's effectiveness can be as simple as
comparing a current audiogram with prior audiograms. This simple
approach, however, can be extremely time consuming and may not identify
trends among miners.
Further, international communities and selected branches of the
U.S. armed services require the effectiveness of the HCP's to be
evaluated even though they do not include specific methods for the
evaluation.
MSHA, however, is not specifying a methodology to determine the
effectiveness of an HCP for several reasons. First, there is not a
consensus among researchers and commenters as to a method even though a
draft ANSI standard (ADBA) has been published on this issue. Secondly,
the techniques for evaluating the effectiveness of an HCP that have
been developed are not appropriate to an HCP with few participants.
MSHA estimates that most HCP's in the mining industry would not have a
sufficient number of participants to be tested. Further, MSHA contends
that there are few consultants and fewer mine operators with the
expertise to evaluate the effectiveness of an HCP.
MSHA requests specific suggestions on practical methods which could
be used in the mining industry, particularly among small mine
[[Page 66407]]
operators, to evaluate the effectiveness of HCP's. MSHA also requests
comments on NIOSH's above stated recommendations.
Temporary or Seasonal Miners
The proposal would not provide any exemption from the requirements
to provide audiometric examinations for temporary or seasonal miners.
OSHA has no such explicit requirement. Moreover to create such an
exemption would mean that workers who change jobs--within a single
industry, or between industries--might end up never having a check on
hearing loss even if working in very noisy conditions.
The proposal does include certain provisions that might in practice
exclude some miners from examinations otherwise required. A mine
operator has up to 6 months to conduct a baseline audiogram--up to 12
months if a mobile van is used. Thus in practice, the operator's
obligation to provide examinations does not extend to those miners who
leave employment before this time and who do not subsequently return to
work for the same operator. Many summer employees might fall into this
category.
MSHA solicits further comment on this issue.
Permissible Exposure Level (PEL)
Proposed Sec. 62.120(c) provides as follows:
No miner shall be exposed to noise in excess of a TWA8 of
90 dBA (PEL) during any workshift, or equivalently a dose of 100%.
(1) If a miner's noise exposure exceeds the PEL, the operator
shall, in addition to taking the actions required under paragraph
(b) of this section, use all feasible engineering and administrative
controls to reduce the miner's noise exposure to the PEL. When
administrative controls are used to reduce a miner's exposure, the
operator shall post these procedures on the mine bulletin board and
provide a copy to affected miners.
(2) If a miner's noise exposure exceeds the PEL despite the use
of the controls required by paragraph (c)(1) of this section, the
operator shall take the actions required by this paragraph for that
miner.
(i) The operator shall use the controls required by paragraph
(c)(1) of this section to reduce the miner's noise exposure to as
low a level as is feasible.
(ii) The operator shall ensure that a miner whose exposure
exceeds the PEL takes the hearing examinations offered through
enrollment in the hearing conservation program.
(iii) The operator shall provide hearing protection to a miner
whose exposure exceeds the PEL and shall ensure the use thereof. The
hearing protection shall be provided and used in accordance with the
requirements of Sec. 62.125.
This paragraph would establish the permissible exposure limit (PEL)
to noise for a miner as a TWA8 of 90 dBA during any workshift.
(This is also referred to as a dose measurement of 100%; the action
level TWA8 of 85 dBA is half this dose of noise.)
The PEL is a time-weighted average sound level to which a miner may
be exposed that establishes the maximum dose of noise permitted. Under
the proposal, this is established as a TWA8 of 90 dBA--the same as
at present. TWA8 refers to a time-weighted-8-hour average, a term
defined in proposed Sec. 62.110. The exposure needed to reach the PEL
varies by sound level and time. For example, the PEL would be reached
as a result of exposure to a sound level of 90 dBA for 8 hours, but
also reached by exposure to a sound level of 95 dBA for only 4 hours or
92 dBA for 6.1 hours.
The Agency considered proposing a different PEL. As noted in part
II of the preamble, MSHA has concluded that there is a significant risk
of material impairment from noise exposures at or above a TWA8 of
85 dBA. MSHA considered setting the PEL at this level, but as discussed
in part IV of this preamble believes that this may not be feasible at
this time for the mining industry. Accordingly, the Agency is proposing
to keep the PEL at a TWA8 of 90 dBA--the level in effect for the
mining industry and under OSHA. The PEL is a dose twice that which
would be received at the level at which there is a significant risk of
material impairment.
While the PEL would not change, the actions required if noise
exposure exceeds the PEL would in many cases be different from those
currently required.
Under the proposal, a hierarchy of controls is established for all
mines. Mine operators must first utilize all feasible engineering and
administrative controls to reduce sound levels to the PEL. This
approach is more consistent with MSHA's existing noise standards for
metal and nonmetal mines than for coal mines. Under the current metal
and nonmetal regulations, mine operators have to utilize either
engineering or administrative controls to reduce noise to the PEL or as
close thereto as feasible. In the coal industry, MSHA inspectors do not
cite for noise without first deducting the attenuating value of hearing
protectors being worn by the miners subjected to excessive exposures of
noise. In practice, this means personal protective equipment is in most
cases accepted as a substitute for engineering and administrative
controls.
As under the present standards, the proposal would require a mine
operator to use only such engineering controls as are technologically
feasible, and to use only such engineering and administrative controls
as are economically feasible for that mine operator.
Moreover, the proposed rule spells out explicit requirements that
will supplement these controls in those cases in which the Agency
concurs with a mine operator that the use of all feasible engineering
and administrative controls cannot reduce noise to the PEL. All sectors
of the mining industry will, in such cases, have to provide all miners
exposed above the PEL with a properly fitting hearing protector, ensure
the miners use those protectors, and ensure that miners take their
annual hearing examinations.
Existing Standards
MSHA's existing metal and nonmetal noise standards require the use
of feasible engineering and administrative controls when a miner's
noise exposure exceeds the PEL. Hearing protectors are also required if
the exposure cannot be reduced to within the PEL. The existing metal
and nonmetal standards do not, however, require the mine operator to
post the procedures for any administrative controls used, to conduct
specific training, or to enroll miners in hearing conservation
programs.
MSHA's existing noise practices for coal mines are significantly
different from those for metal and nonmetal mines. The difference stems
from the circumstances under which the Agency is authorized to issue
citations. In metal and nonmetal mines, a citation is issued based
exclusively on the exposure measurement--when MSHA measures an exposure
at a TWA8 of 90 dBA. But in coal mines, a citation is not issued
in such a case if the miners are wearing hearing protection judged to
be appropriate. The appropriateness is based on the EPA noise reduction
rating minus 7 dB; in practice, most hearing protectors have ratings
which meet this official test for many coal mine exposures.
Accordingly, citations are seldom issued.
When coal mine operators do receive a citation for a miner's noise
exposure exceeding the PEL, they are required to promptly institute
administrative and/or engineering controls to assure compliance.
Additionally, within 60 days of receiving a citation, coal mine
operators are required to submit to MSHA a plan for the administration
of a continuing, effective hearing conservation program, including
provisions for--
(1) Reducing environmental noise levels;
[[Page 66408]]
(2) Making personal ear protective devices available to miners;
(3) Conducting pre-placement and periodic audiograms; and,
(4) Instituting engineering and administrative controls to ensure
compliance with the standard (underground only).
With regard to MSHA's existing noise standard, the Federal Mine
Safety and Health Review Commission (Commission) has addressed the
issue of what MSHA must consider, when determining what is a feasible
noise control for enforcement purposes, at a particular mine. According
to the Commission, a control is considered feasible when: (1) the
control reduces exposure, (2) the control is economically achievable,
and (3) the control is technologically achievable. See Secretary of
Labor v. Callanan Industries, Inc., 5 FMSHRC 1900 (1983), and Secretary
of Labor v. A. H. Smith, 6 FMSHRC 199 (1984).
In determining technological feasibility of a regulation, the
Commission has ruled that a control is deemed achievable 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 noise source. The control does not have to be ``off-the-
shelf''; but, it must have a realistic basis in present technical
capabilities.
In determining economic feasibility, 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 its use to achieve those results. The
Commission has expressly stated that cost-benefit analysis is
unnecessary in order to determine whether a noise control is required.
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
exposure. Todilto Exploration and Development Corporation v. Secretary
of Labor, 5 FMSHRC 1894 (1983). No guidance has been provided by the
Commission as to what level of reduction is considered significant.
However, the Commission has accepted the Agency's determination that a
3 dBA reduction is significant.
MSHA has interpreted the ``expected benefits'' to be the amount of
noise reduction achievable by the control. MSHA generally considers a
reduction of 3 dBA or more to be a significant reduction of the sound
level because it represents at least a 50% reduction in sound energy.
Consequently, a control that achieves relatively little noise reduction
at a high cost could be viewed as not meeting the Commission's test of
economic feasibility.
Consistent with the case law, MSHA considers three factors in
determining whether engineering controls are feasible at a particular
mine: first, the nature and extent of the overexposure; second, the
demonstrated effectiveness of available technology; and third, whether
the committed resources are wholly out of proportion to the expected
results. Before a violation of these requirements of the standard could
be found, MSHA would have to determine that a worker has been
overexposed; that administrative or engineering controls are feasible;
and that the mine operator failed to install or maintain such controls.
(See also the discussion of enforcement policy in the last of the
Questions and Answers in part I.)
OSHA's PEL is a TWA8 of 90 dBA, computed using a 90 dBA
threshold. The standard requires the use of feasible engineering or
administrative controls when a citation for exceeding the PEL is
issued. Under OSHA policy (CPL 2.45A CH-12), however, if an effective
HCP is in place, no STS has been detected, and adequate hearing
protectors are utilized, no citation will be issued for noise exposures
up to a TWA8 of 100 dBA if the costs to implement the HCP are less
than those of engineering or administrative controls. In determining
the appropriateness of hearing protection for this purpose, OSHA
reduces the EPA rating by 7; but it then further reduces effectiveness
by halving the result of that calculation. (A more detailed discussion
of hearing protector derating approaches can be found in the section on
Hearing Protector Effectiveness, part of the discussion of proposed
Sec. 62.125.)
Comments and Studies on PEL
Several commenters to MSHA's ANPRM recommended a PEL of 85 dBA. One
of these stated the following:
The current PEL provides inadequate protection for miner's
hearing. The 90 dB(A) PEL is excessive and permits noise exposure
that will result in significant hearing loss among exposed miners.
Specifically, 21 to 29% of workers exposed to 90 dBA for 40 years
will suffer material impairment of hearing. Material impairment of
hearing, defined by OSHA in this case, is 25 dBA or more loss for
the frequencies 1, 2, and 3 kHz. Based on this risk of damage, OSHA
adopted a hearing conservation program that is required when noise
exposure reaches 85 dBA TWA.
Another of these commenters recommended a PEL of 85 dBA with an 80
dBA action level. This commenter stated that:
Both OSHA and the National Institute for Occupational Safety and
Health (NIOSH) have recommended a PEL of 85 dBA. This level seems to
be an appropriate PEL for mining as well, since the numbers of
miners with hearing loss continues to be a problem. Obviously a more
conservative approach would be to utilize 80 dBA as the action level
to trigger the implementation provisions of an HCP. Although more
costly, the benefits for prevention of NIHL would certainly be
substantial.
Many commenters on this issue, however, believe that MSHA's current
PEL of 90 dBA should be retained and that it is adequate to protect
miners. One commenter referenced Bartsch (see Related Studies in the
III. Nature of the Hazard section of this preamble) as supporting
evidence for retaining the PEL of 90 dBA. Three commenters cited lack
of compensable noise-induced hearing loss (NIHL) cases among miners in
their geographical area as a positive indication that the current PEL
is adequate and they questioned the benefit of reducing the PEL to 85
dBA. These commenters also stated that about 20% of the miners in their
area were exposed to average sound levels above 85 dBA, but under 90
dBA.
In addition to the comments received in response to its ANPRM, MSHA
also reviewed numerous studies and standards relating to the
establishment of a PEL.
The Physical Agents Threshold Limit Value Committee of American
Conference of Governmental Industrial Hygienists (ACGIH) (1993) has
adopted a Threshold Limit Value (TLV) of 85 dBA Leq,8. The
committee believed that there was a clear consensus that an 85 dBA TLV
was valid and needed to protect the hearing acuity of workers at the
higher audiometric frequencies of 3000 and 4000 Hz.
Stekelenburg (1982) suggests that 80 dBA be the acceptable level
for noise exposure over a 40 year work history. Moreover, the
researcher suggests that extra precautions are necessary for sensitive
individuals and that these people need to be identified during the
first five years of exposure to noise.
Embleton (1994) summarized the occupational noise regulations
(pertaining to: PEL, exchange rate, and the upper limit for noise
exposure) from 17 countries and selected branches of the U.S. armed
services. His summary table (absent the recommendations in his report)
is reproduced below as Table III-4.
[[Page 66409]]
Table III-4.--Some Features of
Legislation Tabulated for Various Countries*
--------------------------------------------------------------------------------------------------------------------------------------------------------
Limit for
LAeq 8-hour exposure
engineering or Limit for monitoring
Country (jurisdiction) rate Exchange rate
administrative hearing Upper limit for sound level
controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
Australia (varies by state).. 85 dB................ 3 dB.......... 85
dBA.......... 85 dBA............... 140 dB lin, peak.
Brazil....................... 85 dB................ 5 dB.......... 90 dBA,
no 85 dBA............... 130 dB peak.
exposure >115
dBA if
no
protection.
Canada:
(Federal)................ 87 dB................ 3 dB.......... 87
dB........... 84 dBA............... 140 dB peak.
(ON, QU, NB)............. 90 dB................ 5 dB.......... 90
dBA.......... 85 dBA (a)...........
(AB, NS, NF)............. 85 dB................ 5 dB.......... 85
dBA..........
(BC)..................... 90 dB................ 3 dB.......... 90
dBA..........
China........................ 70-90................ 3 dB..........
................ ..................... 115 dBA.
Finland...................... 85 dB................ 3 dB.......... 85
dB...........
France (b)................... 85 dB................ 3 dB.......... 90 dBA
or 140 dB 85 dBA............... 135 dB peak.
peak.
Germany (b), (c)............. 85 dB................ 3 dB.......... 90
dBA.......... 85 dBA............... 140 dB peak.
Hungary...................... 85 dB................ 3 dB.......... 90
dBA.......... ..................... 125 dBA or 140 dB peak.
Israel....................... 85 dB 5 dB........... ..............
................ 115 dBA or 140 dB
peak..
Italy........................ 85 dB................ 3 dB.......... 90
dB........... 85 dB................ 140 dB peak.
Netherlands.................. 80 dB................ 3 dB.......... 85
dB........... 140 dB peak..........
New Zealand.................. 85 dB................ 3 dB.......... 85 dBA
+3 dB 115 dBA slow or 140
exchange rate. dB peak..
Norway....................... 85 dB................ 3 dB..........
................ 80 dBA............... 110 dBA.
Spain........................ 85 dB................ 3 dB.......... 90
dBA.......... 80 dBA............... 140 dB peak.
Sweden....................... 85 dB................ 3 dB.......... 90
dBA.......... 80 dBA............... 115 dBA or 140 dBC.
United Kingdom............... 85 dB................ 3 dB.......... 90
dBA.......... 85 dBA............... 140 dB peak.
USA (d)...................... 90 dB (TWA8)......... 5 dB.......... 90
dBA but no 85 dBA............... 115 dBA or 140 dB peak.
exposure >115
dBA.
USA Army and Air Force)...... 84 dB................ 3 dB..........
................ 85 dBA............... 140 dB peak.
--------------------------------------------------------------------------------------------------------------------------------------------------------
*Embleton (1994).
Information for countries not represented by Member Societies participating in
the Working Party is taken from Ref. 15.
(a) A more complex situation is simplified to fit this tabulation.
(b) These countries require the noise declaration of machinery, the use of the
quietest machinery where reasonably possible, and reduced reflection of
noise in the building, regardless of sound or exposure levels.
(c) The noise exposure consists of LAeq and adjustments for tonal
character and impulsiveness.
(d) TWA is Time Weighted Average. The regulations in the U.S. are unusually
complex because different thresholds are used to compute levels to initiate
hearing programs (85 dBA), noise exposure monitoring (80 dBA), and noise
reduction measures (90 dBA), each using a 5-dB exchange rate.
Embleton included recommendations based upon current practice taken
from the various jurisdictions:
----------------------------------------------------------------------------------------------------------------
Limit for engineering
LAeq 8-hour ex- Exchange rate or administrative
Limit for monitoring Upper limit for
posure rate controls
hearing sound level
----------------------------------------------------------------------------------------------------------------
85 dBA............... 3 dBA................ Use quietest machines On hiring
and at 140 dB peak.
and room absorption
intervals thereafter.
in workplaces.
----------------------------------------------------------------------------------------------------------------
He stated that:
The primary goal of this report and its recommendations is to
reduce the risk of long term hearing damage and expose people to a
practical minimum. . . . Each feature recommended had been
considered to be practicable by at least one national jurisdiction
and there may be some experience of its usefulness. Much current
legislation was enacted several years ago, before the more recent
scientific evidence was available and before it was integrated into
current understanding of this complex scientific topic.
The U.S. armed services and possibly some international communities
do not go through a public rulemaking process in establishing their
respective noise regulations. Nevertheless, MSHA has included these
sources to show that a consensus exists on noise legislation. Table
III-5 lists information similar to that included in Table III-4 for
several additional entities. Furthermore, there was a discrepancy found
in Table III-4 as per the information provided for the U.S. armed
services. The corrected information is included in Table III-5
(compiled by MSHA).
Table III-5.--Features of Noise
Exposure Criteria for Additional Entities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Limit for
LAeq 8- hour
exgineering or Limit for
Country or jurisdiction exposure rate Exchange rate
administrative monitoring hearing Upper limit for sound level
controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
American Conference of 85 dBA............. 3-dB..............
.................... 85 dBA............. 140 dBC peak.
Governmental Industrial
Hygienists (ACGIH).
[[Page 66410]]
European Economic Community (EEC). 85 dBA............. 3-dB..............
90 dBA.............. 85 dBA............. 140 dB peak.
South Africa...................... 85 dBA............. 3-dB..............
85 dBA.............. 85 dBA............. 115 dBA or 150 dB.
U.S. Air Force.................... 85 dBA............. 3-dB..............
85 dBA.............. 85 dBA............. 115 dBA or 140 dB.
U.S. Army......................... 85 dBA............. 3-dB..............
85 dBA.............. 85 dBA............. 140 dB.
U.S. Navy......................... 84 dBA............. 4-dB..............
84 dBA.............. 84 dBA............. 140 dB.
State of Western Australia........ 90 dBA............. 3-dB..............
90 dBA.............. ................... 140 dB.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Because the information contained in Tables III-4 and III-5 does
not include every jurisdiction, MSHA solicits additional information on
features of noise legislation for comparison purposes.
Hierarchy of Controls
The proposal would require mine operators to use all feasible
engineering or administrative controls or a combination of these
controls to reduce a miner's daily noise exposure to the PEL. If these
controls do not reduce the exposure to the PEL, then they shall be used
to reduce the exposure as low as feasible. The proposal does not place
preference on the use of engineering controls over administrative
controls; but all feasible controls of both types must be implemented
to reduce noise exposure to the PEL or as close thereto as is possible
when all feasible controls are utilized.
MSHA's proposed requirements for either feasible engineering or
administrative controls or a combination of these controls are closer
to MSHA's existing noise standards for metal and nonmetal mines than to
the standards for coal mines.
In metal and nonmetal mines, engineering or administrative controls
are required to the extent feasible when exposures exceed a TWA8
of 90 dBA. Current metal and nonmetal enforcement requirements equate
engineering and administrative controls and do not accept hearing
protectors in lieu of such controls. Mine operators in these
industries, which have a significant percentage of small employers,
generally opt to use engineering controls over administrative controls,
citing practical difficulties with the implementation of the latter.
Administrative controls reduce exposure by limiting the amount of time
that a miner is exposed to noise, through such actions as rotation of
miners to areas having lower sound levels, rescheduling of tasks, and
modifying work activities.
The hierarchy of noise control for coal mines is significantly
different. In determining whether the mine operator is in violation of
the PEL, MSHA deducts from noise exposure measurements the corrected
attenuation of hearing protectors being worn by the miners. Given
normal conditions in these mines, when hearing protectors are being
worn, no citation is issued.
OSHA's standard requires the use of feasible engineering or
administrative controls. As discussed above, however, current OSHA
policy allows employers to rely on a combination of other controls--
enrollment in an HCP, no STS, and adequate hearing protectors (measured
in accordance with specifications adjusted for the purpose of the
policy)--up to a noise exposure of 100 dBA, provided that the cost is
less than that of the engineering and/or administrative controls.
A number of commenters responding to MSHA's ANPRM, specifically
supported the primacy of engineering controls. One commenter supported
the primacy of engineering controls citing anecdotal evidence that
miners resist wearing hearing protectors. Another commenter stated that
engineering controls for mining are far more available than commonly
thought.
Several commenters stated that administrative controls can be
effective but are often impractical. One commenter stated that
administrative controls are effective but are of limited use at small
operations because there are not enough people to rotate through the
various jobs. Another commenter stated that although the use of
administrative controls may lower the exposure of an individual miner
such controls have the disadvantage of increasing overall exposure to a
larger population. A third commenter stated that administrative
controls should be the least preferred control method.
A significant number of commenters specifically requested that MSHA
allow the use of hearing protectors in lieu of engineering or
administrative controls, as long as the hearing protector provided
adequate attenuation. These commenters believed that hearing protectors
were equally as effective as engineering and administrative controls.
Many commenters recommended that MSHA allow the mine operator a
choice or combination of controls, including the use of an HCP. Several
commenters stated the following:
There is no logical reason to handcuff operators by limiting
flexibility and freedom of choice in selecting the most appropriate
method of noise protection for the particular application;
providing, of course, the method is effective.
For some reason HPD's (hearing protection devices) have been
regulated to be a third class behind administrative, and engineering
controls. It is our experience the HPD's provide more effective,
less costly, and more reliable protection than engineering or
administrative controls in many circumstances. The employee
acceptance is also good to excellent. Therefore the discrimination
against HPD's should be removed in any future regulations.
Dear (1987) contends that employers can manage the risk of hearing
impairment by encouraging all employees to participate in the HCP and
that an HCP can be as effective, in many cases, as the use of other,
more costly controls. He believes that some workers are better served
by wearing hearing protectors than reducing the noise via engineering
controls to the PEL. He contends that removing the hearing protectors
when the sound levels are reduced to 90 dBA [by engineering controls]
would expose workers to at least 90 dBA; whereas, use of hearing
protectors would reduce exposures much lower. Dear cites studies
conducted by DuPont on their employees to show the effectiveness of
hearing protectors. Employees in the DuPont HCP, which includes hearing
protectors and begins at approximately 90 dBA, had not developed
hearing impairment during the study period.
Pell and Dear (1988) believe that employees exposed above 90 dBA
are better protected by using appropriate hearing protectors, rather
than implementing engineering controls to
[[Page 66411]]
reduce the noise to 89 dBA or even 84 dBA.
Berger (1983) states the following regarding engineering controls
versus hearing protectors:
When one compares engineering noise controls to HPDs [hearing
protectors], it must be remembered that the same types of problems
which afflict HPD performance in the RW [real world], will tend to
reduce the effectiveness of noise control measures as well. For
example, one of the most commonly used treatments is an enclosure.
If it is not well fitted, or left partially ajar, or circumvented by
an inconvenienced employee, or its gaskets and seals age,
deteriorate, or break in any way, then its performance will be
degraded in a manner similar to that which has been observed for
poorly fitted and misused HPDs. When noise control is achieved by
improved adjustments and lubrication, there must be a trained and
dedicated employee to monitor the maintenance schedule, just as
employees must care for and maintain their HPDs. In fact most
engineering noise control procedures, except for some source noise
control accomplished through equipment redesign, require maintenance
and periodic adjustment or replacement to continue functioning
properly. And except for enclosures, noise reductions of 10 dB or
more are often difficult to achieve and maintain. Thus HPDs remain
one of the most important protective methods for a hearing
conservationist to consider, and can provide an effective adjunct to
engineering noise controls in the majority of industrial noise
environments.
Nilsson et al. (1977) studied hearing loss in shipbuilding workers.
The workers were divided into two groups. In the first group, the
workers were exposed to 94 dBA with 95% of the workers using hearing
protectors. In the second group, the workers were exposed to 88 dBA and
90% of them wore hearing protectors. Both groups were subjected to
impulse noise up to 135 dB. Despite the fact that the vast majority of
the workers in both groups wore hearing protectors, cases of noise-
induced hearing loss (NIHL) were common. The mean pure tone audiograms
showed the typical noise dip at 4000 Hz. For increased exposure
durations, the amount of NIHL increased. Workers exposed to 94 dBA
exhibited more hearing loss than those exposed to 88 dBA. Nilsson
concluded that 58.1% of all of the workers had some degree of hearing
impairment, and only 1.8% was caused by factors other than noise after
excluding hearing loss due to heredity, skull injury, or ear disease.
According to Nilsson et al., the hearing protectors should have
attenuated the noise by at least 13 dBA. This study concluded that
reliance on hearing protectors alone is not sufficient to protect the
hearing acuity of the workers.
NIOSH's position regarding the hierarchy of controls is stated in
their December 16, 1994 comments to MSHA (NIOSH 1994). According to
NIOSH there are three elements of an effective hierarchy of controls.
They are--
1. Prevent or contain hazardous workplace emissions at their
source;
2. Remove the emissions from the pathway between the source and the
worker; and
3. Control the exposure of the worker with barriers between the
worker and the hazardous work environment.
NIOSH further states that the essential characteristics of specific
control solutions are--
1. The levels of protection afforded workers must be reliable,
consistent, and adequate;
2. The efficacy of the protection for each individual worker must
be determinable during use throughout the lifespan of the system;
3. The solution must minimize dependence on human intervention for
its efficacy so as to increase its reliability; and
4. The solution must consider all routes of entry into worker's
bodies and should not exacerbate existing health or safety problems or
create additional problems of its own.
NIOSH (1988), in its publication entitled ``Proposed National
Strategy for the Prevention of Noise-Induced Hearing Loss''
(Publication No. 89-135), encouraged OSHA to rescind its policy of
accepting HCP's in lieu of either feasible engineering and/or
administrative controls and states:
It is extremely foolhardy to regard hearing protection as a
preferred way to limit noise exposures because most employees obtain
only half the sound attenuation possible from hearing protectors.
Even with training, some workers fail to obtain maximum benefit from
these protectors because they have difficulty adjusting them
properly, or they refuse to wear them because they fear such devices
will impair their ability to perform their jobs properly or hear
warning signals. If, however, noise is reduced by engineering and/or
administrative controls, the limitations of hearing protectors are
of less concern.
In the report, ``Preventing Illness and Injury in the Workplace,''
the Office of Technology Assessment (1985) found that health
professionals rank engineering controls as the priority means of
controlling exposure, followed by administrative controls, with
personal protective equipment as a last resort.
The National Hearing Conservation Association (NHCA) in a letter
from their President, Susan Cooper Megerson (1994), to Joseph Dear,
Assistant Secretary of Labor for Occupational Safety and Health, urged
OSHA to rescind its policy of accepting an HCP in lieu of engineering
noise controls for exposures up to 100 dBA. NHCA contends that feasible
engineering controls should be the preferred method of controlling the
noise. Further, NHCA states that ``Most hearing protectors, as they are
worn in the field, do not provide sufficient attenuation to bring
workers' exposures from 100 dB(A) to safe noise levels.''
Suter (1994) in a letter to Sue Andrei of OSHA's Policy Directorate
urged OSHA to rescind its policy of accepting an HCP in lieu of
engineering and/or administrative controls for exposures up to 100 dBA.
Suter contends that most HCPs are ineffective due to hearing protectors
providing only a fraction of their laboratory attenuation. Further,
Suter urges OSHA to re-emphasize engineering noise controls.
MSHA understands that the two letters to OSHA were sent in response
to an OSHA request for comment on how to design a priority scheme for
OSHA standards. No responses were issued, and the priority scheme is
still pending. MSHA has also reviewed a recent letter to the EPA from
the American Industrial Hygiene Association questioning the rating
system used to label hearing protectors with attenuation values; this
is discussed above in the section on Hearing protector effectiveness
(in connection with proposed 62.125).
In summary, commenters and researchers on this issue were divided
as to whether engineering/administrative controls should have primacy
over the use of hearing protectors or an HCP. Most of the international
community, U.S. armed services, and NIOSH, however, discourage the use
of hearing protectors and an HCP as the primary means of control and
accept their use only when engineering and administrative controls
failed to achieve a significant reduction in the worker's exposure.
Administrative controls reduce exposure by limiting the amount of
time that a miner is exposed to noise, through such actions as rotation
of miners to areas having lower sound levels, rescheduling of tasks,
and modifying work activities. Many mine operators have demonstrated
that administrative controls can be as effective and less costly than
the installation of engineering controls. However, the use of
administrative controls may be limited by labor/management agreements,
limitations on the number of qualified miners capable of handling a
specific task, or difficulty in ensuring that miners adhere to the
[[Page 66412]]
administrative controls. Additionally, administrative controls have the
potential draw back of exposing multiple workers to high sound levels
for designated time periods. Because the effectiveness of
administrative controls is based on adherence to these strict time
periods, mine operators may find it difficult to verify compliance with
the administrative procedures.
Although there are some disadvantages to using administrative
controls, the Agency has determined that in certain circumstances they
can be as effective as engineering controls. MSHA, therefore, believes
that the mine operator should have the option to choose which method of
control to use--provided that all feasible controls must be utilized if
needed to reduce sound levels to or below the PEL. This would give mine
operators maximum flexibility when considering the intricacies of their
operation in complying with the regulation. Administrative controls,
utilized properly, spread the risk over a larger population although at
a lower risk to each individual.
A related type of control would be the transfer of miners to other
assignments. The Mine Safety and Health Act provides for the Agency to
prescribe such an approach in certain cases. MSHA considered proposals
to do so in cases in which an STS is detected. Discussion of this topic
is covered by the section of the preamble that reviews proposed
Sec. 62.180.
Based upon its review of the available evidence, MSHA concludes
that a reduction of a miner's risk of material impairment due to
occupational NIHL noise can best be achieved through the use of all
feasible engineering or administrative controls or a combination
thereof. The use of engineering controls inherently provides the most
consistent and reliable protection because such controls do not depend
upon individual human performance or intervention to function. MSHA's
proposal would, however, allow mine operators to use either engineering
or administrative controls. This would provide the mine operator with
the flexibility to select the most appropriate control for the
situation. These methods would be given clear primacy over personal
protective controls. While MSHA is aware that NIOSH is seeking to
develop an approach that would more accurately derate hearing
protectors in actual workplace use, the prospects for this remain
uncertain; moreover, the issues associated with the consistency and
reliability of personal protective equipment use would remain.
Engineering Noise Controls for Mining Equipment
Engineering noise controls reduce exposure by modifying the noise
source, noise path or the receiver's environment thereby decreasing the
miner's exposure to harmful sound levels. Examples of these three types
of engineering controls are exhaust mufflers, barriers, and
environmental cabs, respectively. Exposures may also be controlled by
substituting quieter mining equipment. For example, a diamond wire saw
can be substituted for a conventional hand-held channel burner in the
dimension stone industry.
MSHA has listed feasible engineering controls for the major
classifications of equipment used in metal and nonmetal mines in its
Program Policy Manual, Volume IV. The engineering controls referenced
in this manual have been evaluated by MSHA Technical Support and proven
feasible and effective in the mining industry. This document is
currently used by MSHA inspectors and others to assist in determining
if engineering controls are feasible. Following are some examples of
the feasible controls covered in that manual.
1. Acoustically treated cabs. For mining equipment such as haul
trucks, front-end-loaders, bulldozers, track drills, and underground
jumbo drills, acoustically treated cabs are among the most effective
noise controls. Such cabs are widely available, from the original
equipment manufacturer and the manufacturers of retrofit cabs, for
machines manufactured within the past 20 years. The noise reduction of
factory installed acoustically treated cabs is generally more effective
than that of retrofit cabs. According to some manufacturers, sound
levels at the mine operator's position inside factory cabs are often
below 90 dBA and in some cases below 85 dBA.
Occasionally, underground mining conditions are such that full-
sized surface haulage equipment can be used. Where this is possible,
such equipment can be equipped with a cab as described above.
Additionally, some manufacturers offer cabs for lower profile
underground mining equipment such as scoop-trams, shuttle cars, and
haul trucks. The use of cabs on such underground mobile haulage
equipment generally is feasible provided it does not create a safety
hazard due to impaired visibility.
The former USBOM has published two how-to manuals entitled
``Bulldozer Noise Controls'' (1980), and ``Front-End Loader Noise
Controls'' (1981) that describe in great detail how to install a
retrofit cab and install acoustical materials.
2. Barrier shields. For some equipment, generally over 20 years
old, an environmental cab may not be available from the original
equipment manufacturer or from manufacturers of retrofit cabs. In such
cases, a partial barrier with selective placement of acoustical
material can generally be installed at nominal cost to block the noise
reaching the equipment operator. These techniques are also demonstrated
in ``Bulldozer Noise Controls'' (1980).
Barrier shields and partial enclosures can also be used on track
drills where full cabs are not feasible. Such shields and enclosures
can be either free standing or attached to the drill. Typically,
however, they are not as effective as cabs and usually do not reduce
the miner's noise exposure to within MSHA's current 90 dBA PEL. This
barrier can be constructed at minimal cost from used conveyor belting.
3. Exhaust mufflers. In addition to an environmental cab or barrier
shield, diesel powered equipment can be equipped with an effective
exhaust muffler. The end of the muffler's exhaust pipe should be
located as far away from the equipment operator as possible, and the
exhaust directed away from the operator. For underground mining
equipment, exhaust mufflers are generally not needed where water
scrubbers are used. A water scrubber offers some noise reduction and
the addition of an exhaust muffler may create excessive back pressure
or interfere with the proper functioning of the scrubber. However,
exhaust mufflers can be installed on underground equipment where
catalytic converters are used.
Exhaust mufflers can also be installed on pneumatically powered
equipment. For example, exhaust mufflers are offered by the
manufacturers of almost every jackleg drill, chipping hammer, and jack
hammer. In the few cases where such exhaust mufflers are not available
from the factory, they can be easily constructed by the mine operator.
MSHA has a videotape available showing the construction of such an
exhaust muffler for a jackleg drill. This muffler can be constructed at
minimal cost from a section of rubber motorcycle tire.
4. Acoustical materials. Various types of acoustical materials can
be strategically used to block, absorb, and/or dampen sound. Generally
such materials are installed on the inside walls of equipment cabs or
operator compartments and in control rooms and booths. For example:
barrier and
[[Page 66413]]
absorptive materials can be used to reduce noise emanating from the
engine and transmission compartments; and acoustic material can be
applied to the firewall between the employee and transmission
compartment. Noise reduction varies depending upon the specific
application. Care must be taken to use acoustical materials that will
not create a fire hazard.
5. Control rooms and booths. Acoustically treated control rooms and
booths are frequently used in mills, processing plants, or at portable
operations, to protect miners from noise created by crushing,
screening, or processing equipment. Such control rooms and booths
typically are successful in reducing exposures of employees working in
them to below 85 dBA.
6. Substitution of equipment. In a few cases, where sound levels
are particularly severe, and neither retrofit nor factory controls are
available, the equipment may need to be replaced with a quieter type.
For example, hand-held channel burners had been used for many years to
cut granite in dimension stone quarries. These were basically small jet
engines on a pole, fueled by diesel fuel and compressed air. The pole
was held by the channel burner operator and the flame was directed
against the granite. The intense heat caused the granite to spall and
by moving the flame back and forth a channel could be created. Sound
levels typically exceeded 120 dBA at the operator's ear.
Several years ago, alternative and quieter methods of cutting the
granite were developed. These included replacing the channel burner
with either a diamond wire saw, hydraulic or pneumatic slot drill, or
water jet. Dimension stone operators were notified by MSHA of the
availability of these alternatives and given time to phase out the use
of diesel-fueled, hand-held burners and replace them with one of the
quieter alternatives. MSHA also has a videotape describing these
various alternatives.
7. New equipment design. Using the channel burners as an example, a
new design of channel burner was engineered which automated the
process. The hand-held channel burners can be replaced with automated
channel burners using liquid oxygen. The automated design does not
require the operator to be near the channel burner, thereby using
distance to attenuate the noise.
In addition to the noise controls described in MSHA's Program
Policy Manual, Volume IV, a number of other documents are available
describing effective noise controls for coal, metal and nonmetal
mines--controls for underground equipment and controls for surface
equipment.
The MSHA document entitled, ``Summary of Noise Controls for Mining
Machinery,'' (Maraccini et al., 1986) provides case histories of
effective noise controls installed on specific makes and models of
mining equipment. The case histories describe the controls used, their
cost, and the amount of noise reduction achieved. MSHA believes that
the controls utilized in these specific cases can be extended to other
pieces of mining equipment.
Furthermore, the former USBOM, which has been responsible for
conducting research leading to improved equipment and methods for
controlling safety and health hazards in mining, published a handbook
entitled, ``Mining Machinery Noise Control Guidelines, 1983.''
(Bartholomae and Parker, 1983) This handbook describes engineering
noise controls for coal, metal and nonmetal mining equipment. The
former USBOM also published numerous documents describing noise
controls for mining machinery. Many of these research reports are
listed in the USBOM publication IC9004, ``The Bureau of Mines Noise-
Control Research Program--A 10-Year Review.'' (Aljoe et al., 1985) Part
V of this preamble contains a list of USBOM publications dealing with
particular types of equipment.
In particular, these include noise control methods for coal cutting
equipment, longwall equipment, conveyors, and diesel equipment.
Underground coal mining equipment may require some unique noise
controls. However, for coal cutting machines such as continuous miners
and longwall shears, the use of remote control is the single most
significant noise control. The installation of noise dampening
materials and enclosure of motors and gear cases can be used to aid in
controlling noise of coal transporting equipment such as conveyors and
belt systems. Diesel equipment used underground can use controls
similar to those used on surface equipment. Mufflers, sound controlled
cabs, and barriers will provide much of the needed noise control for
this type of equipment.
Finally, while MSHA is not making any assumptions about the
development of new technologies, it would be interested to learn of any
processes under development that could further assist mine operators in
controlling noise. For example, the former USBOM (Burks and
Bartholomae, 1992) has developed a variable speed chain conveyor which
can be used to reduce the noise exposure of continuous miner operators
and loading machine operators in particular. An empty conveyor is
noisier than a full one because the coal covering the conveyor inhibits
the radiation of noise. The variable speed chain conveyor only operates
when necessary to convey coal. To date the manufacturers of mining
machines have apparently not adopted this technology, despite the fact
that it has the added benefits of reduced dust emissions, reduced power
consumption, and reduced maintenance costs.
Although most of the USBOM noise control documents are not
specifically discussed in this section, MSHA has reviewed them. The
reviewed documents are listed in the references and are available to
the mining community. For additional information on USBOM noise control
projects contact: Mr. Edward D. Thimons, U.S. Department of Energy,
Pittsburgh Research Center, P.O. 18070, Pittsburgh, PA 15236, (412)
892-6683, Fax (412) 892-4259.
Posting of Administrative Control Procedures
The proposal would require that the mine operator post a copy of
any administrative controls in effect on the mine bulletin board, and
provide affected miners with a copy. As required by Section 109 of the
Mine Act, a mine operator must have a bulletin board. Documents
containing pertinent mine information are required to be posted by
various mandatory standards (e.g., training plan, emergency
communication numbers, MSHA citations, etc.). This is an ideal place to
require the administrative procedures to be posted, since most miners
are familiar with its location and the importance of documents placed
on it.
The existing MSHA coal noise regulations do not require written
administrative controls, unless these controls are part of a hearing
conservation plan. Further, if written, the administrative controls are
not required to be posted. However, the affected miner would be
informed of the administrative procedures as part of his/her required
part 48 training. Neither MSHA's current metal and nonmetal nor OSHA's
noise regulations require that administrative controls, if used, be in
writing and posted.
MSHA did not receive any comments on this issue.
MSHA has concluded that it is important that administrative
controls be posted, since miners must actively comply for the controls
to be effective. Posting would facilitate informing miners of work
practices necessary for
[[Page 66414]]
reducing their noise exposures, especially when temporarily assigned to
a different job. Since the administrative controls must be in writing
to be posted on the mine bulletin board, MSHA believes that providing
the affected miners with copies would not be a significant burden as
compared to other possible methods of notification and is likely to be
more much more effective in ensuring miners are on notice of their
obligation to comply.
Supplementary Controls
Under proposed Sec. 62.120(b), any miner exposed above the action
level will receive special training in noise protection, and be
enrolled in a hearing conservation program in which annual audiometric
tests are offered. Any miner exposed above that level is to receive
hearing protection upon request, as is any miner who incurs an STS or
who is waiting for a baseline audiogram. The operator must ensure
hearing protection is worn, however, in only two cases: if there is an
STS, and if it will take more than 6 months to get the baseline
audiogram because of the need to wait for a mobile test van.
Under proposed Sec. 62.120(c), if exposures exceed the PEL, and
cannot be feasibly reduced to the PEL through the use of all feasible
engineering and administrative controls, a few additional requirements
would be applicable. All miners so exposed must be provided hearing
protection, and required to use the hearing protection. In addition,
the operator would be required to ensure that miners take the scheduled
audiometric examinations.
The circumstances under which hearing protection must be worn are
discussed more fully in connection with proposed Sec. 62.125.
MSHA is proposing that mine operators require miners enrolled in an
HCP to participate in audiometric testing once exposures exceed the
PEL. This is not the case under OSHA; however, MSHA believes this
approach is warranted in the mining industry.
The information generated by these tests can serve as triggers for
both the mine operator and the Agency to investigate more thoroughly
the implementation of noise controls. If an employee incurs a standard
threshold shift, at the very least a hearing protector needs to be
provided or changed. The audiological information can provide useful
clues to the noise causing the problem, and point to an undetected
failure of various controls: engineering controls, administrative
controls, or the failure to properly fit, maintain or utilize hearing
protectors. If an employee incurs a reportable hearing loss, it is an
indication that despite regular MSHA inspections, some serious problem
has not been detected or resolved and a more thorough analysis is
probably required. If the required audiological examinations are not
taken, standard threshold shifts and cases of reportable hearing loss
will go unreported.
In addition, the Agency wants to ensure that miners are aware of
the severity of any hearing loss; in a mining environment, this
knowledge could have implications for the safety of the miner and the
safety of others. Miners who do not recognize that they have a hearing
problem--and hearing loss occurs gradually and is often hard for
individuals to accept--may be less willing than those who have been
advised they have a problem to pay attention to the problem. The
proposed regulation provides for annual training, but a notification of
a detectable change in hearing acuity would certainly help to focus
attention.
The Agency is concerned that unless such participation is
mandatory, the cost of the examinations, however limited, might create
an incentive for mine operators to encourage miners to waive the
examinations. Concern about the implications of health examinations on
their job security may likewise discourage miners from taking
examinations. The voluntary X-ray surveillance program currently
offered to coal miners has a poor record of participation. This is not
an unusual situation in the mining industry, where retention of good,
well-paying jobs is a priority for most workers.
Finally, it should be noted that audiometric testing is not an
invasive procedure. No damaging radiation is involved, nor is there any
penetration with a needle or other device.
Comments on this provision are specifically solicited. In
particular, experience from companies in which such examinations are
mandated would be welcome. The Agency recognizes there may be concern
on the part of some miners that if mine operators are provided with
audiometric information, it could lead to the discharge of miners who
are developing hearing loss problems so as to minimize potential
workers' compensation claims.
Dual Hearing Protection
Proposed Sec. 62.120(d) would require that, in addition to the
controls required for noise exposure that exceed the PEL, a mine
operator provide dual hearing protectors to a miner whose noise
exposure exceeds a TWA8 of 105 dBA during any workshift, a dose of
800% of the PEL. The mine operator must also ensure that they are worn.
An earplug type protector would be worn under an earmuff type
protector.
Currently, neither MSHA nor OSHA specifically mandate the use of
dual hearing protection. In practice, however, existing rules require
dual hearing protection under some circumstances.
Under current Coal and Metal and Nonmetal noise policy, dual
hearing protection would be required whenever the attenuation of a
single hearing protector does not reduce the miner's noise exposure to
within the PEL.
Also, due to MSHA's current procedures for determining the
attenuation of hearing protectors (discussed under Hearing protector
effectiveness of this preamble), dual hearing protection would almost
always be required when miners are exposed to sound levels above 112
dBA. As discussed below, the attenuation provided by dual hearing
protectors is less than the sum of their individual attenuations. MSHA
policy currently specifies that 6 dB be added to the attenuation of the
hearing protector having the higher attenuation.
OSHA requires that ``adequate'' hearing protection be provided to
and worn by workers. Employers would thus have to utilize dual hearing
protection in some cases to get the needed attenuation. However, no
specific dose level triggering dual hearing protection level has been
established by OSHA.
No commenter addressed the exposure above which dual hearing
protection would be required. One commenter suggested that MSHA
consider dual hearing protection to provide 5 dB more attenuation than
the hearing protector with the higher attenuation. Another commenter,
disagreed with current MSHA Metal and Nonmetal policy and believed that
more than 6 dBA credit should be given above the attenuation of the
higher component (earplug or earmuff) when dual hearing protectors are
worn. This commenter did not, however, specify how much credit should
be given.
Research has demonstrated that dual hearing protection affords the
wearer greater attenuation than either earplugs or earmuffs alone.
Berger in EARLOG 13 (1984) has shown that the use of dual hearing
protectors provides greater attenuation. The attenuation of the dual
hearing protection is at least 5 dB greater than the attenuation of
either hearing protector alone. This attenuation, however, is much less
than the sum of the individual Noise Reduction Rating (NRR) values and
is dependent on the frequency. Dual hearing protectors are especially
important for noise which is dominated
[[Page 66415]]
by low to middle frequency sounds. The performance of dual hearing
protectors is not influenced greatly by the selection of the earmuff;
however, the selection of the earplug has a strong influence on the
attenuation below 2000 Hz. For noises which are dominated by sounds
above 2000 Hz, the attenuation of dual hearing protectors is limited by
flanking bone conduction paths to the inner ear. Berger recommends dual
hearing protectors whenever the TWA8 exceeds 105 dBA.
Michael (1991) believes that, because of complex coupling factors,
the attenuation from wearing both earplugs and earmuffs cannot be
predicted accurately. If the attenuation of the earplug and earmuff is
about the same at a given frequency, then the resultant attenuation
should be 3 to 6 dB greater than the higher of the two individual
attenuations. However, if one attenuation is much greater than the
other, then the resultant attenuation will be slightly more than the
higher attenuation.
Nixon and Berger (1991) report that earplugs, worn in combination
with earmuffs or helmets, typically provided more attenuation than
either hearing protector alone. The gain, in attenuation at individual
frequencies, varies between 0 to 15 dB. At or above 2000 Hz, the
attenuation of the combination is limited by bone conduction to
approximately 40 to 50 dB. Below 2000 Hz, the selection of the earplug
is critical for increasing the attenuation. There is little change in
the attenuation of different types of earmuffs at frequencies below
2000 Hz.
Bertrand and Zeiden (1993) determined that miners exposed to sound
levels of 118 dBA were afforded protection consistent with a sound
level of 98 dBA by the use of earmuffs. The earmuff had an NRR of 24
dB. Consequently, the earmuff alone could not provide attenuation
sufficient to protect the miner's hearing acuity.
Research has clearly demonstrated that dual hearing protection
provides greater attenuation than either hearing protector alone.
Further, the U.S. armed services require dual hearing protection for
workers exposed to high sound levels. MSHA concurs that the additional
attenuation afforded by the use of dual hearing protection is necessary
to protect miners who are exposed to high sound levels. Furthermore,
MSHA has concluded that a TWA8 of 105 dBA (800%) is a prudent
level above which dual hearing protection should be required. This
level of noise exposure can quickly damage the hearing acuity of the
exposed miner.
Dose Ceiling
Although the statement of the PEL in Sec. 62.120(c) is absolute
that no miner shall be exposed to noise above a TWA8 of 90 dBA,
the remainder of that paragraph and paragraph (d) deal with situations
where in fact miners are going to be exposed to noise in excess of the
PEL for some period of time--due to the economic feasibility of
administrative and engineering controls for a particular mine operator,
or due to the technological feasibility of engineering controls as to a
particular operation. The seriousness of this situation for miners is
indicated by the fact that MSHA is proposing that dual hearing
protectors be required at a TWA8 of 105 dBA: a noise dose of 800%.
The Agency is interested in comments on whether there is some noise
dose which should be established as an absolute dose ceiling by the
regulation, regardless of the implications for a particular mine
operator or operation. The circumstances in which this might pose a
problem for the mining industry appear to be very limited. While coal
inspection data over the years have indicated some exposures over 800%,
MSHA believes these are anomolies for which well-known controls are
available. If there are problems, they are likely to be in the metal
and nonmetal sector.
On the one hand, the dual-survey data indicate that using the 80
dBA threshold level, only about one-quarter of one percent (0.28%) of
metal and non-metal exposures exceed a noise dose of 800%. The data
indicate, however, that there remain a few specific job categories in
the metal and nonmetal sector which experience a significant problem
with noise exposures of this dimension, as indicated in Table III-6.
The sample size is provided to illustrate that in some cases, the
percentages are based on limited data.
Table III-6: Metal/Nonmetal Job Categories in Which More Than 1% of
Recorded Exposures Are Over a TWA8 of 105 dBA (800% of PEL)
------------------------------------------------------------------------
No. > No. of Percent
Code Job category 105 sample > 105
------------------------------------------------------------------------
134............ Jet-piercing channel 5 9 56
operator.
234............ Jet-piercing drill 1 3 33
operator.
058............ Drift miner.............. 15 55 27
057............ Stope miner.............. 9 39 23
534............ Jackleg or stopper drill 7 31 23
operator.
434............ Churn drill operator..... 1 7 14
334............ Wagon drill operator..... 3 30 10
034............ Diamond drill operator... 3 46 7
046............ Rock or roof bolter...... 2 38 5
734............ Rotary (pneumatic) drill 20 478 4
operator.
634............ Rotary (electric or 11 544 2
hydraulic) drill
operator.
934............ Jumbo percussion drill 2 111 2
operator.
399............ Dimension stone cutter 3 301 1
and polisher; rock sawer.
------------------------------------------------------------------------
Notes: Miscellaneous job categories where less than 1% of recorded
exposures exceeded TWA8 of 105 dBA are not displayed. Numbers are for
four year period, 1991-1994.
The job descriptions do not necessarily indicate the equipment in
use; for example, the stope miners and drift miners may well have been
using the same equipment as the jackleg drill operators. Based on the
Agency's experience, there are only a few pieces of equipment used in
mining for which no control other than multiple hearing protectors is
currently available.
The data illustrate that many exposures at this level are
preventable. Even with the jackleg drills more than 75% of the
exposures were controlled to less than a TWA8 of 105 dBA. The data
base from which the above information was drawn found nine bulldozer
operators and three truck drivers
[[Page 66416]]
exposed to noise above 800% of the PEL; and while these constituted
only a small fraction of the samples of those job categories, 0.7% and
0.05% respectively, the Agency is disturbed to find any such samples at
all given that the metal and nonmetal industry has for some years been
operating under a requirement to use engineering and administrative
controls to bring sound levels down to the PEL or as close thereto as
is feasible.
Accordingly, MSHA requests comment on whether there should be an
absolute dose ceiling, regardless of the economic feasibility of
control by an individual mine operator, and what that should be. MSHA
also requests comment on whether such a dose ceiling should be
technology forcing--i.e. apply regardless of the technological
feasibility of currently available controls.
Ceiling Level
Proposed Sec. 62.120(e) would retain MSHA's current 115 dBA ceiling
level for continuous and intermittent noise. The 115 dBA ceiling level
is intended to protect individuals from high sound levels which last
longer than those typically characterized by impulse/impact noise.
The 115 dBA ceiling level originated out of the Walsh-Healey Public
Contracts Act which formed the basis of current Department of Labor
noise regulations. OSHA, in its 1974 proposed noise standard (39 FR
37775), specified that the 115 dBA limit was a maximum steady state
sound level which was not to be exceeded regardless of the time-
weighted average dose computation.
In its ANPRM, MSHA did not specifically request comments on the 115
dBA ceiling limit. One commenter, however, presented a view on the 115
dBA level. This commenter stated that ``Few professionals would allow a
worker to remain unprotected while exposed to 115 dBA for 15 minutes.''
MSHA's review of available literature found a diversity of opinions
on the choice of a ceiling level for exposures to continuous and
intermittent noise.
At the 93rd Meeting of the Acoustical Society of America, Johnson
and Schori (1977) reported that 115 dBA for 15 minutes may be grossly
under protective, while an upper limit of 115 dBA, regardless of the
time of the exposure, is unduly restrictive. For example, they found
significant temporary threshold shift from exposure to 115 dBA for only
2.7 minutes. On the other hand, they found virtually no such shift from
exposure to 130 dBA for 10 seconds and minimal shift (median of 2 dB)
when exposed to 120 dBA for 40 seconds--although MSHA would point out
it knows of no mining tasks taking such a limited time. In any event,
this shows that the ceiling limit is dependent upon both time and
intensity.
Cluff (1984) stated that ``The selection of 115 dBA for 15 minutes
is arbitrary and represents several contradictions.'' He agreed with
Johnson, however, that exposures to 115 dBA for 15 minutes is
dangerous. Cluff stated that ``this danger is magnified by extending
the 5 dB rule to 130 dBA'' and suggested that a 3-dB or 4-dB exchange
rate may have merit as a solution.
Others discussed different ceiling limits to prevent temporary
threshold shift which may lead to a permanent NIHL. The U.S. Army's
Technical Memorandum 13-67, ``Criteria for Assessing Hearing Damage
Risk from Impulse-Noise Exposure'' (Coles, 1967) stated that:
It has been customary in steady-state noise DRC [damage risk
criteria] * * * to include an upper limit of about 135 dB for
unprotected noise exposure for any duration, however short. In most
cases it is understood by implication only, rather than by direct
statement, that this restriction is not intended to apply to impulse
noise * * *
The technical memorandum, however, stated further that:
The relationship between TTS [temporary threshold shift]
resulting from a single noise exposure and permanent threshold shift
(PTS) to be expected from habitual exposure is not known with
certainty even for steady-state noise.
In Acoustic Parameters of Hazardous Noise Exposures, however,
Henderson (1990) discussed a critical level above which damage by
acoustic trauma begins. He stated that:
At levels above 120 dB SPL [sound pressure level] the cochlea
begins to be damaged by direct mechanical destruction, i.e., the
organ of Corti can be lifted off the basilar membrane, tight-cell
junctions can be ripped apart, and the tympanic membrane can be
ruptured. The level at which mechanical damage occurs has been
called the ``critical level,'' but it is important to recognize that
there is not a critical level but rather a transition point that is
related to the spectrum and temporal pattern of the exposure.
CHABA (1993) believed that single exposure to sound levels above
140 dBA can permanently damage hearing. Furthermore, the threshold for
pain is dependent upon the frequency of the noise. This threshold lies
between 135 and 140 dB.
Ward (1990) stated that:
* * * a ``critical exposure'' for production of immediate severe
loss, presumably associated with structural failure in the cochlea
rather than with metabolic fatigue, is dependent not on the energy
in the exposure (p SUP 2t) but on a different quantity given by
integrating the fourth power of the pressure over time. * * * The
best estimate for the critical exposure in man is around 10 SUP 11
Pa SUP 4-sec for a median value, although individual differences in
susceptibility and vulnerability mean that the range will be very
great.
NIOSH (1995) recommends that the 115 dBA ceiling limit be retained.
Citing recent medical research, NIOSH believes that the critical level
is between 115 and 120 dBA. Above the critical level, immediate
structural damage to the ear occurs. This structural damage causes a
loss of hearing acuity.
ACGIH (1994) recommended that exposures to occupational noise
should not be permitted above 139 dBA. Further, for sound levels equal
to or exceeding 103 dBA, ACGIH believes that the exposure be ``limited
by the noise source--not by administrative control.''
As illustrated by the above discussed studies, there is no
consensus among the scientific community as to a sound level above
which permanent damage occurs (regardless of the duration of exposure).
However, many researchers believe the critical level is slightly above
115 dBA and is time dependent with an allowable duration of less than
15 minutes.
International communities and selected branches of the U.S. armed
services specify a ceiling level; however, there is no agreement among
these groups either.
There are relatively few noise sources in the mining industry that
produce sound levels exceeding 115 dBA (e.g., unmuffled pneumatic rock
drills and hand-held channel burners). However, these sources often
operate during most of the work shift with resulting full-shift noise
exposure considerably over the PEL. Currently, MSHA surveys these noise
sources by taking spot readings with Type 2 sound level meters rather
than conducting full-shift sampling with a personal noise dosimeter.
The requirements for Type 2 sound level meters are in ANSI S1.4-1983,
``Specification for Sound Level Meters.'' MSHA intends to continue
sampling these sources using a sound level meter.
Even though this proposal has retained the 115 dBA ceiling level
for noise exposure, sound levels above 115 dBA are to be included in
the determination of the noise dose. The Agency has determined that it
is important to include sound levels above 115 dBA in the noise dose so
that the miner's noise exposure is accurately assessed. By having an
accurate assessment, the mine operator will be
[[Page 66417]]
able to provide hearing protectors with maximum attenuation and take
steps to ensure that the hearing protectors are effectively fitted and
properly worn.
MSHA believes that exposure to sound levels exceeding 115 dBA,
regardless of duration, may potentially result in acute hearing loss
among susceptible individuals. Although there is a lack of scientific
consensus on the exact time of safe exposure, the majority believe that
15 minutes is hazardous. Accordingly, MSHA believes retention of the
current ceiling is warranted. The Agency, however, welcomes additional
comment on this issue.
Exposure Determination by Operators
Proposed Sec. 62.120(f)(1) would require mine operators to
establish a system of monitoring which effectively evaluates each
miner's noise exposure. This will ensure that mine operators have the
means to determine whether a miner's exposure exceeds any of the
limitations established by this section, as well as to assess the
effectiveness of noise controls. The proposed rule is performance
oriented in that the regularity and methodology used to make this
evaluation are not specified. Specific requirements for periodic
monitoring by qualified persons now applicable to the coal sector would
be revoked.
Under the approach proposed, mine operators may design a monitoring
program suitable for each specific mine site. Mine operators would be
expected to utilize survey methods and instrumentation which are
scientifically valid and based on sound industrial hygiene practice.
Although calibration requirements are not specifically mandated in
the proposal, good industrial hygiene practice dictates that any
instrumentation used for determining a worker's occupational exposure
to a contaminant, in this case noise, be calibrated. The calibration
program should be composed of three phases--type testing of
instruments, laboratory calibration of the instruments, and field
calibration. Seiler and Giardino (1996) discussed the importance of
each of these classes of calibrations.
Briefly, type testing is an exhaustive testing of a model of
instrument to ascertain that it complies with a standard, such as the
ANSI standard for personal noise dosimeters. Laboratory calibration is
an extensive calibration that ascertains that an individual instrument
meets factory specifications. Finally, field calibration is a brief
procedure conducted before and after a survey to ascertain that an
instrument is operating properly.
The mine operator has the responsibility of accurately determining
a miner's noise exposure. In order to do this properly the type of
instrumentation needs to be considered. In the cramped quarters of an
underground mine and on mobile mining equipment, it may not be possible
to accurately evaluate a miner's noise exposure without endangering the
technician if a sound level meter is used. Other occupations cannot be
sampled with a sound level meter because the most exposed ear is not
accessible to the technician. For the above occupations, a personal
noise dosimeter would need to be used. An analysis of noise exposures
collected from 1986 through 1992 by the MSHA coal inspectorate revealed
that 21.8% of the occupations could only be sampled using personal
noise dosimeters. These occupations comprised nearly 60% of the surveys
conducted by the inspectors.
A program would be expected to evaluate noise exposure in adequate
detail to enable the mine operator to reasonably determine which miners
work in areas requiring the institution of the controls that may be
required. Sufficient evidence of a noise monitoring program must be
available during mine inspections to permit the evaluation by MSHA of
the program's effectiveness. The Agency will also take its own surveys
of noise exposure during inspections to ascertain miner exposure and to
evaluate the effectiveness of the mine operator's monitoring program.
MSHA believes that this proposal affirms a mine operator's
obligation to take the action needed to determine whether or not a
miner is in compliance with the exposure limitation requirements of the
proposed regulation. At the same time, it allows mine operators maximum
flexibility for determining a miner's noise exposure.
MSHA believes that mine operators have a number of incentives to
monitor sound levels on a regular basis to ensure they can:
(1) Avoid the costs associated with needlessly including or
retaining a miner in an HCP or providing special noise training;
(2) Assess the effectiveness or need for either engineering or
administrative controls or a combination of these controls to meet the
TWA8 of 90 dBA;
(3) Document the miner's exposure for workers' compensation
purposes;
(4) Provide information to health professionals evaluating miners'
health and audiograms; and
(5) Avoid citations and penalties during the regular Agency
inspections in the mining industry for failure to comply with the
standard's requirements.
The results of operator monitoring will not be sent to MSHA, nor
will monitoring results be used to determine compliance with the
applicable noise standard. Mine operators are, however, under an
obligation to take certain actions based upon any noise measurements
they conduct. Proposed Sec. 62.120 requires mine operators to take
specific corrective action when a miner's noise exposure exceeds the
various limitations set forth in the section. It also requires that
miners be notified whenever a mine operator determines that their noise
exposure exceeds the action level.
The requirements of proposed Sec. 62.120(a), as to how noise is to
be measured for the purposes of this proposal, would need to be
followed by mine operators in their monitoring. These requirements
include: disregarding the attenuation of any hearing protector worn by
the miner, integrating all sound levels from 80 dBA to at least 130 dBA
during a miner's full workshift, using a 90 dBA criterion level and a
5-dB exchange rate, and using an A-weighting and slow-response
instrument setting. Mine operators would, of course, be free to take
any additional measurements that they deem appropriate: for example,
taking peak-response readings to measure any impact/impulse noise.
MSHA current coal noise standards (30 CFR Secs. 70.500/71.800)
require mine operators to monitor each miner's noise exposure twice a
year and certify the results to MSHA. These standards also specify when
and how to sample, who is qualified to sample, and reporting
requirements.
MSHA's noise standards (30 CFR Secs. 56/57.5050) for metal and
nonmetal mines do not contain any operator sampling requirements,
although they do require that mine operators maintain exposures in
compliance with the PEL. In order to do this effectively, many metal
and nonmetal mine operators conduct their own monitoring.
OSHA's noise standard requires employers to implement a monitoring
program when information indicates that any employee's noise exposure
may equal or exceed the action level (TWA8 of 85 dBA). OSHA allows
employers to use representative personal or area sampling; however, in
areas with significant variations in sound level or high worker
mobility, the employer would have to show that area sampling produces
results equivalent to personal sampling. OSHA also requires the
[[Page 66418]]
employer to repeat the monitoring in specific situations.
MSHA's ANPRM solicited comments on the frequency of monitoring, the
sampling strategy, and the use of the information obtained. The ANPRM
also asked whether specification-oriented or performance-oriented
requirements would be more appropriate. At that time, the Agency
solicited comments based on the premise that the proposed rule would
include a detailed monitoring requirement and the commenters responded
accordingly. However, since MSHA has decided not to propose detailed
monitoring requirements, the Agency has not addressed specific issues
regarding area versus personal monitoring, instrumentation
specifications, calibration requirements, or other related monitoring
issues.
Many commenters preferred performance-oriented standards, similar
to OSHA's, that would allow mine operator discretion in when and how to
sample. One of these commenters stated:
The goal of the monitoring effort should not be simply to
collect noise exposure data, but rather to accomplish the goal of
eliminating job-related noise induced hearing loss. With this goal
in mind, the operator would need to have collected noise exposure
information on the jobs that he had reason to believe were above the
85 dBA action level. This information would be necessary to identify
those workers that should be included in the HCP as well as areas
and equipment where noise controls are needed.
If the operator does not choose to monitor for noise, he should
have an alternate plan that accomplished the same goal: i.e.,
includes all non-office workers in the HCP regardless of noise
exposure, perform a sound level survey to identify mandatory hearing
protection areas and equipment, etc. It is recommended that MSHA
adopt the logic outlined in the OSHA noise standard, 29 CFR
1910.95(d) (1), (2) and (3).
Conversely, two commenters recommended a specification-oriented
rule. One of these recommended personal monitoring on an annual basis
and the other simply recommended personal or area monitoring.
Finally, two commenters had a different view on monitoring. They
recommended that MSHA, rather than the mine operator, conduct all
monitoring for the purpose of this proposed standard. In response to
these commenters, the Agency would point out that it is the
responsibility of mine operators to ensure the safety and health of
their miners. MSHA sampling programs are to audit the mine operators to
ensure the protection of miners. Moreover, MSHA does not have the
resources to sample every miner annually. Metal and Nonmetal has
specific health sampling guidelines which require periodic sampling of
selected mining occupations. MSHA currently conducts over 20,000 full-
shift noise exposure surveys in the mining industry annually. Although
MSHA intends to continue measuring the noise exposure of miners in
order to determine compliance, it can only sample a small percentage of
the exposed mining population annually. Mine operators are responsible
for knowing at all times when their employees exceed applicable limits
so that appropriate action can be taken.
The Agency, however, is willing to share its sampling results and
analyses of these results with the mining industry. Mine operators who
do not conduct their own monitoring could use the MSHA data along with
information from equipment manufacturers to estimate a miner's noise
exposure. This could be beneficial to all mine operators, particularly
small mine operators with limited resources. If, however, as a result
of this proposal, MSHA changes the threshold, prior sampling conducted
by the Agency may not provide an accurate indication of whether a
miner's noise exposure exceeds the new standard.
Although a mine operator could use prior MSHA sampling results, and
information from equipment manufacturers, such use would not relieve
the mine operator of responsibility to appropriately determine a
miner's noise exposure. Therefore, it would behoove mine operators to
determine a miner's noise exposure by methods comparable to those which
would be used by MSHA, as outlined in Sec. 62.120(a).
Although numerous commenters and organizations supported the need
for monitoring, most favored a performance-oriented approach and did
not specify a procedure to be followed. MSHA agrees. The Agency
believes that the focus of the noise standard should be on preventing
NIHL and reducing miners' noise exposures and that it would be
counterproductive to specify detailed monitoring requirements or
procedures. Also, the Agency does not want to stifle improvements in
monitoring technology or methodology.
Moreover, the Agency believes that the current specification-
oriented coal operator monitoring produces results that in fact are not
representative of miners' noise exposure. For example, in FY 1994, coal
mine operators conducted approximately 180,000 noise surveys (two per
miner) and found 36 miners to be overexposed (their exposures exceeded
132%). However, MSHA does not know the extent to which mine operators
may be including credit for the wearing of hearing protection in the
determination of the miner's exposure. Conversely, MSHA conducted 6,339
surveys in coal mines and found 857 exposures exceeding the 132%.
However, only 62 of these surveys resulted in a violation due to credit
being given for use of hearing protection. This indicates that despite
having specification-oriented monitoring requirements, current operator
sampling in coal mines may not be providing results consistent with
those found by MSHA.
For monitoring compliance with this proposal, the Agency intends to
use validated scientific methodology. Current MSHA sampling procedures
and policies are listed in MSHA's Program Policy Manual and its Coal,
and Metal and Nonmetal, Health Inspection Procedures Handbooks. Copies
of these documents are available for review and copying in MSHA
offices. MSHA's sampling procedures, however, would be modified to be
consistent with Sec. 62.120(a) of this proposal once the rule is
finalized.
Currently, MSHA bases its noise exposure compliance determinations
on personal full-shift sampling with a personal noise dosimeter. The
calibration of the personal noise dosimeters is checked before and
after each survey. Additionally, annual laboratory calibration is
conducted to assure measurement accuracy. The personal noise
dosimeter's microphone is positioned on the top of the miner's
shoulder, midway between the neck and the end of the shoulder, with the
microphone diaphragm pointing in a vertical upward direction. The
microphone is placed on the shoulder that is normally between the
principal noise source and the miner's ear. Sampling is conducted while
the miner performs his/her normal duties.
In the development of this proposal, MSHA also reviewed the noise
monitoring programs of the U.S. Armed Services and other jurisdictions.
Although MSHA has described its current noise sampling procedures,
the Agency may decide to modify or change these procedures based upon
new or improved sampling methods, instrumentation, or technology.
Employee Notification
Proposed Sec. 62.120(f)(2) would require that within 15 calendar
days of determining that a miner's exposure exceeds the action level,
the permissible exposure level, the dual hearing protection level, or
the ceiling level established by this section, the mine
[[Page 66419]]
operator notify the miner in writing of the overexposure and the
corrective action being taken. If the miner's exposure has not changed
from one of these levels to another, and the miner has been notified of
his exposure at that level within the past year, no notification needs
to be provided; if the level has changed, or there has been no
notification in the past year, notification is to be provided. The
proposal specifically states that these notifications are triggered by
exposure evaluations conducted either by the operator or by an MSHA
inspector.
At the present time, MSHA does not require notification, though it
is implied in those cases in which a coal miner is enrolled in an HCP
for having exceeded the PEL. OSHA's standard requires that employees be
notified in writing of monitoring results that exceed the action level
within 21 days of the monitoring.
The proposed requirement is consistent with Section 103(c) of the
Mine Act. Section 103(c) of the Mine Act states in pertinent part that:
Each operator shall promptly notify any miner who has been or is
being exposed to * * * harmful physical agents * * * at levels which
exceed those prescribed by an applicable mandatory health or safety
standard promulgated under section 101 * * * and shall inform the
miner who is being thus exposed of the corrective action being
taken.
Many commenters supported miner notification of all sampling
results and stated that such is current company policy. Several of
these commenters recommended that the specific method of notification
be left to the discretion of the mine operator. One commenter
specifically stated that through notification, ``the employee could
help facilitate a solution to the problem and be more committed to
following safety procedures.'' This commenter also stated that
``requiring written notification is not effective when dealing with
persons who cannot read or do not have the background to understand the
meaning of the notification's contents.''
A mining association commented ``* * * that miners should be made
aware when their exposure exceeds allowable limits * * *'' and that ``*
* * employees should have knowledge of their exposure and any
subsequent hearing loss. * * *'' This association suggested, however,
that notification ``* * * be in the form of entry into the HCP. * * *''
Several other commenters recommended that MSHA's requirements be the
same as OSHA's.
After reviewing the comments and the regulations from the U.S.
Armed Forces and international organizations, MSHA concludes that
notification should be provided for exposure at any level defined in
the proposed regulation. At the action level, there is a significant
risk of material impairment (as discussed in part II of this preamble).
Notification will be needed at this level because under the proposal,
if the noise exceeds that level, the mine operator would be required to
take protective action (hearing protectors and enrollment in an HCP).
Notification at this level would explain to the miners the reason why
it is necessary for them to wear their hearing protectors. Moreover,
since the harm occurs at this level, notification is required under
Sec. 103(c) of the 1977 Mine Act. Notification at the permissible
exposure level and dual hearing protection level--exposures
respectively 2 and 16 times the dose at the action level--is necessary
to ensure the miner understands the rationale for added protection and
the actions being taken by the mine operator to lower noise exposures.
The same is true for any exposures exceeding the ceiling level.
MSHA believes there is no need to notify a miner of every exposure
determination, as long as the miner is cognizant of the general level
of his or her exposure--so that the miner pays attention to noise
exposure and noise abatement efforts (including the use of properly
fitted and maintained hearing protectors). If an exposure measurement
for a miner demonstrates a change in that miner's situation--e.g., from
below the PEL to over the PEL, or from over the PEL to above the dual-
hearing protector level--the miners should be made aware of this fact.
Moreover, even if the miner's situation has not changed, the miner
should be reminded of his or her overexposure when it is measured if
notification has not been made recently. MSHA welcomes comment on the
proper balance to strike between the need for notification and
nonproductive paperwork.
MSHA has concluded that the notification should be in writing. This
would ensure that the miner does not misconstrue the measured level nor
the actions being taken.
Warning Signs
The proposed rule has no provision for requiring the posting of
warning signs. While MSHA acknowledges the value of posting warning
signs, the process is inherently complicated in the ever changing
mining environment, and MSHA believes the training requirements it is
proposing should ensure miners are apprised of noise hazards to which
they may be exposed.
Section 101(a)(7) of the Mine Act requires that health or safety
standards promulgated by MSHA:
* * * prescribe the use of labels or other appropriate forms of
warning as are necessary to insure that miners are apprised of all
hazards to which they are exposed, * * *
Existing MSHA noise standards do not exercise this authority with
respect to noise, and do not require the posting of warning signs.
When OSHA promulgated its Hearing Conservation Amendment, it did
not include a requirement for warning signs. OSHA stated in the
preamble to the final rule, that the use of warning signs to warn
employees about noise hazards in high noise areas should be left to the
discretion of the employer. In so doing, OSHA stated that noise is more
readily discernible than other harmful physical agents and therefore a
specific warning sign requirement may not be necessary to protect
employees, and that in certain circumstances such signs might confuse
rather than serve a useful educational purpose. OSHA also recognized
that the employer is more familiar with the workplace environment and
will be in a better position to determine if the posting of signs in a
given situation will aid in the success of the company's HCP. Further,
OSHA stated that other methods, such as training, may be more
appropriate for apprising employees of the hazards of noise.
In its ANPRM, MSHA asked whether it should require warning signs in
areas exceeding a specified sound level, and what this sound level
should be. Numerous commenters specifically addressed the issue of
warning signs and were about equally divided over whether such a
requirement is necessary. Those commenters supporting the use of
warning signs varied considerably on criteria for their use. For
example, one commenter indicated that warning signs should only be
posted in areas where an immediate threat of injury exists, such as
areas with impact noise above 140 dB or constant noise above 115 dBA.
Other commenters said that warning signs should only be required on
non-mobile equipment, or in areas where the use of hearing protectors
is mandatory.
Among those commenters that did not support the use of warning
signs, several stated that MSHA's standard should be performance-
oriented and allow the mine operator to decide how to warn its
employees, such as through training, safety meetings, notification of
exposure results, etc. One commenter
[[Page 66420]]
stated that in the mining environment it would be difficult to
illuminate signs to the point they could be read and understood, and
that they would be difficult to maintain in most mining situations.
This commenter also believed that the nature of certain mining
operations does not lend itself to the use of signs because the work
area is constantly changing. Another commenter agreed, stating that
warning signs would be difficult to keep current in mobile operations.
Warning signs could provide an indication to miners that they are
entering an area where the wearing of hearing protectors is required.
Some mine operators have voluntarily placed warning signs in high noise
areas such as preparation facilities and on surface mobile equipment.
MSHA believes, due to the dynamic nature of mining (advancing
underground faces, changing quarry perimeters, a mobile workforce,
etc.), that a requirement for the installation of fixed warning signs
may be difficult to implement. Warning signs may also be inappropriate
where miners do not work a fixed period of time in the area covered by
the sign. For example, a miner in an area with a 90 dBA sound level for
less than four hours, with no significant noise exposure for the rest
of the day, would not be required to wear hearing protectors under
MSHA's proposal, whereas a miner who spends more than four hours in
that area would.
After careful analysis of the literature and review of regulatory
requirements from international communities and the U.S. Armed
Services, MSHA believes that training may be a more appropriate vehicle
to inform workers of the hazards of noise to their hearing. Further,
the Agency believes that the posting of warning signs for noise should
be optional and left to the discretion of the mine operator. The
proposed rule would require initial and annual training for all miners
exposed above the action level as discussed under Sec. 62.130 Training
of this preamble.
Though MSHA is not proposing to require warning signs for noise, it
expects that many mine operators will voluntarily post such signs to
indicate to miners locations where hearing protectors must be worn. If,
however, mine operators choose to use administrative controls to reduce
a miner's noise exposure, the proposal would require that the affected
miner be informed of the administrative procedures and that such
controls be posted on the mine bulletin board. Such procedures may
provide notification of sound levels in specific work locations.
Section 62.125 Hearing Protectors.
Whenever hearing protectors are required to be provided by the
proposed regulations, they must be provided in accordance with the
requirements of this section.
The miner is to have a choice from at least one earplug type and
muff type protector; and, in the event dual hearing protection is
required, a choice of one of each. The mine operator is to ensure that
in those cases when hearing protection is required to be worn, it is
worn by miners exposed to sound levels required to be integrated into
the miner's dose measurement: i.e., sound levels above 80 dBA. The
hearing protector is to be fitted and maintained in accordance with the
manufacturer's instructions. Hearing protectors and necessary
replacements are to be provided by the mine operator at no cost to the
miner. Finally, should the hearing protector cause or aggravate a
medical pathology of the ear, the miner is to be allowed to select a
different hearing protector from among those offered by the mine
operator.
Selection of Hearing Protector
The proposal requires that if hearing protectors are required to be
provided to miners for any reasons, the mine operator shall provide a
choice of one earplug type and one muff type, and ensure proper fit.
Earmuffs include both active and passive; earplugs include disposable
earplugs, pre-molded earplugs, custom-molded earplugs, and canal caps.
The proposal also requires that the training in hearing protection
specified in proposed Sec. 62.130(a) be received at least once before
the miner has to make a choice: to ensure the miner understands the
choices available.
While these requirements are limited, they will help to
significantly encourage hearing protector use and effectiveness. The
proposal does not seek to constrain mine operator selection of
protectors. As noted herein, hearing protectors come in a wide variety,
for different purposes, and with different attenuation values. MSHA
believes that mine operators have an incentive to provide a wide
variety of types to encourage safe and effective use.
MSHA's existing noise standards require mine operators to provide
adequate hearing protectors, but do not specify that a variety of
hearing protectors be offered. OSHA's noise standard requires that
employees be given the opportunity to select from a variety of suitable
hearing protectors provided by the employer; however, the variety is
not defined. OSHA states in the 1981 preamble to its Hearing
Conservation Amendment (46 FR 4152) that ``The company must make a
concerted effort to find the right protector for each worker-one that
offers the appropriate amount of attenuation, is accepted in terms of
comfort, and is used by the employee.''
In its ANPRM, MSHA asked whether mine operators should be required
to make available a selection of hearing protectors. Almost all of the
commenters on this issue were in favor of this provision. Some
specifically recommended that the mine operator provide a choice of at
least three different models, including at least one earmuff and one
earplug. One commenter suggested that the selection should include at
least six models. Most commenters indicated that the need to provide a
variety of hearing protectors is more related to fitting and comfort
than on the labeled attenuation per se.
One commenter recommended against providing a variety of hearing
protectors, stating that ``It is the responsibility of the mine
operator to evaluate the various noise exposures, and to select the
appropriate HPDs [hearing protectors].'' The commenter maintained that
the mine operator should only have to provide an alternative hearing
protector when the individual has a specific condition which precludes
the use of the selected hearing protector.
Several commenters addressed the need to allow the miner to choose
a hearing protector that is comfortable. One commenter stated that:
The most effective hearing protector is one that is worn and
worn properly. If the hearing protector is not comfortable or the
employee cannot wear a certain type of plug or muff, then the
hearing protector will not be worn and the HCP will not be
effective.
Another commenter maintained that ``* * * the principal usage problem
with HPD's is that because of discomfort, interference with necessary
communication, and interference with normal work routines, many HPD's
are not worn.'' While another commenter stated:
The performance of hearing protectors in the field (including
the manners in which they are used, not used, or misused by workers
in situations in which HPDs are needed, but are uncomfortable,
unsafe, or otherwise inconvenient) is frequently inferior to their
performance when tested in idealized laboratory conditions and there
are substantial variations among individual susceptibilities to
noise-induced hearing loss [NIHL].
The National Hearing Conservation Association's Task Force on
Hearing Protector Effectiveness (Royster, 1995)
[[Page 66421]]
recommends that the employer consider many criteria when selecting the
variety of hearing protectors from which workers are to choose. The
most important criterion for choosing a hearing protector is ``the
ability of a wearer to achieve a comfortable noise-blocking seal which
can be maintained during all noise exposures.'' Other criteria include
hearing protector's noise reduction, wearer's daily noise exposure,
variations in sound level during a work shift, user preference,
communication needs, hearing acuity of the wearer, compatibility with
other safety equipment, wearer's physical limitations, and climate and
working conditions. Physical limitations (missing fingers, arthritis,
limited hand strength) may restrict users from properly inserting
compressible foam earplugs in their ears.
Berger (1986) stated that comfort must be considered when selecting
hearing protectors. If the laboratory attenuation of a hearing
protector is very high, but it is uncomfortable to wear, the actual in-
use attenuation may be reduced or even nonexistent. Conversely, a
comfortable hearing protector with less attenuation may be worn
consistently, thereby providing greater effective protection.
In EARLOG 8, Berger (1981) asserted that an employee should have
two weeks to try out an adequate hearing protector and select another
one if the original selection does not perform satisfactorily.
In the report, Communication in Noisy Environments (Coleman et al.,
1984), the authors stated that:
Although acceptability is in part governed by the comfort of the
devices, there are other factors such as concern with hygiene,
belief in (real or presumed) communication difficulties, and social
constraints which can influence the extent to which workers will use
the protection provided. * * * Sweetland (1981) found concern about
communication difficulties to be a major factor in mine workers
acceptance of protectors.
The authors further stated that:
In general, ear inserts [earplugs] appear less attractive than
circumaural protectors [earmuffs] for mining conditions. A helmet
mounted circumaural protector is to be preferred on grounds of
comfort, ease of fitting and removal, reliability of attenuation,
and acceptability in terms of hygiene; whereas ear inserts of the
compressible foam type may produce marginally less interference with
communication and they will impair localization less, they are
likely to be more comfortable in hot and humid conditions.
Pfeiffer (1992) suggested that greater care be exercised when
selecting hearing protectors for workers experiencing hearing loss.
Pfeiffer stated that it is important not to overprotect the worker
which can cause difficulty in communicating. If this happens, the
worker will be reluctant to wear the hearing protector.
MSHA recognizes that local mine conditions such as dust,
temperature, and humidity can cause one type of hearing protector to be
more suitable than another. For example, under normal mining
conditions, some miners may experience problems with earmuffs because
of a buildup of perspiration under the seals.
Based on such factors and on comments received in response to the
ANPRM, MSHA concluded that the minimum selection appropriate to offer
miners with normal hearing consists of at least one type of earmuff and
one type of earplug. MSHA expects that each hearing protector in the
selection would provide adequate attenuation. Further, a consensus of
the U.S. armed services and international communities agrees that
workers should choose from a selection of several hearing protectors.
If miners are allowed to choose from a selection of hearing
protectors, particularly if given appropriate training as is required
under this proposal, they will be more apt to wear and care for them in
such a manner as to obtain the maximum amount of protection. Providing
miners with a choice from a selection of hearing protectors will foster
greater acceptance and use. Further, MSHA recognizes that a trial
period may be necessary for the miner to determine if using the
selected hearing protector for a prolonged period causes significant
discomfort. If significant discomfort occurs, MSHA encourages the mine
operator to allow the miner an opportunity to select an alternate
hearing protector. Selection of an alternative hearing protector is
mandatory under the proposal if required by a medical condition.
There are several factors which the affected miner needs to
consider before choosing a hearing protector from the selection
offered, and which miners will learn about through the training
specified under proposed Sec. 62.130(a). These factors include--
(1) Hearing protectors must fit properly to provide the estimated
amount of protection;
(2) People have all shapes and sizes of ear canals, and fitting
commonly used earplugs to an unusually shaped ear canal may be
uncomfortable or harmful to the individual. For those earplugs which
need to be fitted to the size of the ear canal, all available sizes of
that earplug should be available for fitting and use. Some employees
may need a different size for each ear when their ear canals are of a
different size or configuration; and
(3) Hearing impaired miners may need special hearing protectors
which provide adequate attenuation, yet permit auditory reception.
With regard to the latter, MSHA is not at this time proposing that
any special type of hearing protector be provided, nor any type of
protector be excluded, for those miners who are already hearing
impaired. However, MSHA will endeavor to ensure operators understand
that special care should be taken in providing a hearing protector for
the safety of a miner with a significant hearing loss. Most earplugs
and earmuffs attenuate sound unequally across all frequencies and are
most effective at attenuating high frequency sounds. Hearing loss due
to noise and aging reaches its peak at the higher audiometric
frequencies. Because of these factors, a miner wearing a hearing
protector, without specific accommodation for any significant hearing
loss, would hear distorted auditory signals which would significantly
hamper communication. A miner, with a significant hearing loss and
wearing hearing protectors, could be placed in a hazardous situation
because he/she could not hear or comprehend an audible warning.
Although some commenters have recommended the use of communication
type hearing protectors for hearing impaired miners, MSHA will caution
mine operators against their use in very high noise areas because the
sound level produced under the cup may be hazardous. Some manufacturers
of communication type hearing protectors, however, have placed limiters
in the electronics to protect against the speaker in the cup producing
hazardous sound levels.
Even though some researchers have indicated that using a hearing
protector may cause communication problems for an impaired miner,
commenters have presented many practical ways of resolving this
problem. Consequently, MSHA chose not to propose specific requirements
regarding hearing protectors for impaired miners to allow the mine
operators maximum flexibility.
MSHA solicits comments on whether mine operators should be required
to provide an additional type of hearing protector, such as flat
response, level dependent or active noise control earmuff, for miners
with a hearing impairment, or whether any type of protector should be
explicitly excluded for such miners.
[[Page 66422]]
Hearing Protector Effectiveness
MSHA received many comments on the attenuation, or effectiveness,
of hearing protectors. The issue arises in a number of contexts,
including what role a hearing protector's attenuating characteristics
should play in the selection of the most appropriate hearing protector
in those cases requiring hearing protection.
While MSHA recognizes the importance of proper selection, MSHA has
decided not to incorporate specific procedures into its proposal on
rating the effectiveness of hearing protectors. Based on the
information presented herein, MSHA has concluded there is not presently
a generally acceptable method of predicting hearing protector
attenuation in the field. Moreover, MSHA has determined that there are
other factors which are equally or more important than a hearing
protector's attenuation for ensuring that a miner is protected from
NIHL. These factors include: (1) comfort, (2) training, (3) fit, (4)
maintenance, and (5) consistent use.
Nevertheless, MSHA realizes the merits of having a valid
methodology for determining the attenuation of hearing protectors--for
a variety of reasons, including facilitation of the selection of the
most appropriate hearing protector when selection and use is required.
The Agency, therefore, solicits comments on a scientifically based, yet
practical, method for determining the effectiveness of hearing
protectors as used under mining conditions. In addition, comments on
field estimates of hearing protector attenuation, especially the NIOSH
(1995) derating scheme, are encouraged.
Current MSHA regulations do not explicitly address this issue. MSHA
policy, however, specifies a procedure for calculating a hearing
protector's effective attenuation based upon the Noise Reduction Rating
(NRR) provided by the manufacturer. Manufacturers currently determine
an NRR for each hearing protector from laboratory testing in accordance
with EPA regulations (40 CFR Sec. 211.206 and Sec. 211.207). The NRR is
intended to provide an estimate of the noise reduction achievable under
optimal conditions and was designed to be used with C-weighted sound
levels. Because MSHA measures noise exposure with A-weighting instead
of C-weighting, it adjusts the NRR by subtracting 7 dB. As reported by
Maraccini (1987), this 7-dB adjustment accounts for the average
difference between the C-weighted and A-weighted sound levels in
mining.
OSHA's standard does specify the hearing protector attenuation
required. Under OSHA's standard, attenuation must be sufficient to
reduce an employee's noise exposure to a TWA8 of 90 dBA; except
that if the worker is experiencing an STS, then the hearing protector
must reduce the noise exposure to a TWA8 of 85 dBA. Employers are
required to use one of four methods to determine the noise exposure
beneath the hearing protector. These methods are NRR and NIOSH methods
1, 2, or 3 as described in the ``List of Personal Hearing Protectors
and Attenuation Data,'' HEW Publication No. 76-120, NIOSH 1975, pp. 21-
37. The NRR is the most convenient method to use and is a
simplification of NIOSH method 2. In addition, when the NRR is to be
used with A-weighted sound levels, OSHA requires that 7 dB be
subtracted from the NRR.
As noted in connection with the discussion of proposed
Sec. 62.120(c), where an employer wishes to take advantage of OSHA's
policy of not citing overexposures when, among other factors, adequate
hearing protection is being used, a more stringent method of
determining the effectiveness of hearing protectors is used by OSHA. In
evaluating hearing protector effectiveness in this context, OSHA also
subtracts 7 dB from the hearing protector's stated NRR to adjust for
the difference in weighting systems, but further derates the NRR by
50%. All types of hearing protectors are treated the same way. The
derating is done to account for the significant reductions, which
various researchers have found, in hearing protector attenuation under
industrial conditions when compared to laboratory conditions.
One commenter to MSHA's ANPRM indicated that laboratory protocols
have been developed and are being tested which may be more
representative of the actual field performance of hearing protectors,
but noted that validated and agreed upon standardized procedures are
still some years away. This commenter stated:
The real-world attenuation data which form the basis for our
criteria are taken from Berger's summary (1983) of 10 field studies,
utilizing 1551 employees, wearing seven different types of earplugs
and greater than nine different types of earmuffs, in over 50
different industries, and his more recent paper (Berger, 1988) which
discusses additional current studies. Although the data can be
separated by plugs and muffs, the variability within the plug
category is such that some of the better attenuating earplugs
overlap with the earmuffs. Therefore, for a general regulatory
guideline, the data averaged across all HPDs and employee subjects
is taken from the two papers. This results in an NRR84 of
approximately 10 dB (i.e., the NRR computed with a one-standard
deviation correction which estimates the protection at the 84th
percentile).
Since the NRR is meant to be subtracted from the C-weighted
sound level, and the regulation is formulated in terms of A-weighted
levels, an indicator of representative C-A values for the mining
industry is then required. The 100 NIOSH noises (NIOSH, 1975) which
have often been taken to be representative of general industry have
median C-A of about 2 dB, and 90% have C-As of <6.5 dB. However, mining noises may exhibit greater low-frequency energy. For example the data in Kogut (1990) which represent 17 different types of equipment in the metal/nonmetal mining industry (coal excluded), show a mean C-A of 6.7 dB, but the Kogut values are not a statistically representative sample of the mining industry. For our purposes we will average the two estimates and presume a median C-A for mining of 5 dB. With an NRR for 84% of the users of 10 dB, and C-A value for typical mining noises of 5 dB, the credit for HPD attenuation for most of the users in the typical mining noises is 10-5="5" dB. Adding this value of 5 dB to the PEL of 90 dBA sets the second cutoff level of 95 dBA. This commenter also stated that NRR's do not provide a good indication of either relative or absolute field performance; thus, ``there is no good way to accurately derate existing lab data to predict field performance.'' In The NIOSH Compendium of Hearing Protection Devices (1994) several sets of laboratory measured attenuations, besides the NRR, are listed. These data were obtained using different standardized methods. NIOSH presents examples of using each method to estimate the sound level beneath the hearing protector. In addition, NIOSH presents physical features (i.e., number of flanges, composition, compatibility with other personal safety equipment, etc.) of the hearing protectors. NIOSH (1995) recommends a derating scheme based upon the type of hearing protector. NIOSH acknowledges that hearing protector wearers do not attain the laboratory attenuation in industrial situations. Accordingly, they recommend that to ascertain the effectiveness of a hearing protector in workplace use, the NRR for an earmuff, formable earplugs, and all other earplugs would be derated by 25%, 50%, and 70%, respectively. The National Hearing Conservation Association's Task Force on Hearing Protector Effectiveness (Royster, 1995) recommends that the EPA's NRR for hearing protector attenuation be replaced with a new NRR(SF), which the researchers felt more realistically reflects the field performance of hearing protectors. The NRR(SF)'s are determined by laboratory testing for hearing protector attenuation after the [[Page 66423]] subject fits the hearing protector to his/her head. This differs from the EPA's NRR value which is determined after the researcher fits the hearing protector to the subject. Regardless of the method used, the amount of attenuation provided by a hearing protector will vary among the individual subjects resulting in a range of attenuation values. The Task Force stresses that it is not possible to predict the field attenuation of a given hearing protector for an individual; it concluded, however, that the NRR(SF) would be a more realistic estimate. In addition, small differences (less than 3 dB) in the NRR or NRR(SF) are not believed to be of practical consequence. The Task Force recommends continued audiometric testing whenever hearing protectors are used. MSHA notes that the American Industrial Hygiene Association (AIHA, 1995) recently sent the EPA a letter requesting that the EPA revise its rule on noise labeling requirements for hearing protectors. The reasons cited for requesting a revision of EPA's NRR rating system included-- (1) the current method of rating hearing protectors overestimates the actual workplace protection from 140 to almost 2000 percent; (2) the inability to predict absolute levels of protection from labeled values; (3) the labeled values are a poor predictor of relative performance of one hearing protector versus another; (4) there are no provisions for retesting the hearing protectors on a recurring basis; and (5) there is no requirement for quality assessment or accreditation of the test laboratory. Michael (1991) believed that the simplification needed to obtain a single number rating (NRR) caused it to be inaccurate. Instead of the NRR, the researcher recommended using the spectra of the noise in conjunction with the attenuation characteristics to select the most appropriate hearing protector. This is even more important when the wearer has sensorineural hearing loss. Many field studies on the attenuation of hearing protectors have been conducted in the mining industry by Giardino and Durkt (1996), Kogut and Goff (1994), Giardino and Durkt (1994), Bertrand and Zeiden (1993), Durkt (1993), Goff et. al. (1986), Durkt and Marraccini (1986), Goff and Blank (1984), and Savich (1979). With the exception of Bertrand and Zeiden (1993), these researchers reported that hearing protectors provided much less attenuation than that measured in the laboratory. Some researchers tested new earmuffs while others tested old earmuffs. In many instances attenuation was minimal and highly variable. These studies indicate that hearing protector attenuation cannot be reliably predicted under actual use conditions and is substantially less than that indicated by the NRR from the manufacturer. Bertrand and Zeiden (1993) determined the effectiveness of hearing protectors by measuring the hearing level of miners exposed to sound levels exceeding 115 dBA. These researchers found that although the hearing protectors provided less attenuation, the difference was not significant. For example, miners exposed to 118 dBA had hearing levels consistent with exposure to 98 dBA. Therefore, the hearing protector whose NRR was 24 provided 20 dBA of attenuation. Durkt (1993) studied the effectiveness of 11 models of new earmuffs using miniature microphones inside and outside the cups. At surface mines, 107 tests were conducted on operators of equipment, including bulldozers, front-end-loaders, and overburden drills. Durkt concluded that the effectiveness of the earmuff was related to the noise spectrum. Moreover, the measured noise reduction was much less than the NRR when the noise spectrum contained significant amounts of low frequency noise. Most diesel-powered equipment generate noise which is primarily in the low frequency range. Kogut and Goff (1994) studied the effectiveness of earmuffs being used in both surface and underground mines. A total of 540 tests were conducted on miners wearing their normal earmuffs. The procedure was similar, but not identical, to the procedure used by Durkt (1993). Like Durkt, the researchers concluded the noise reduction afforded by earmuffs was related to the spectrum of the noise. According to the researchers, ``The earmuffs' effectiveness in reducing noise exhibited great variability and frequently fell far short of the NRR.'' Furthermore, a simple method of reliably predicting the effectiveness of earmuffs eluded the researchers. A complex method was developed for predicting the effectiveness of earmuffs; however, it lacks practicality. Giardino and Durkt (1996) and Giardino and Durkt (1994) expanded on the previous two discussed studies. A total of 1,265 tests were performed on 545 different machines (20 different machine types). According to the researchers, earmuffs provided minimal noise reduction for the operators of equipment powered by internal combustion engines. The researchers concluded that the NRR was a poor predictor of earmuff performance under actual mining conditions. Furthermore, they reported that the NRR is not a good indicator for comparing different models of earmuffs. Numerous research studies performed in other industries by Pfeiffer (1992), Hempstock and Hill (1990), Green et al. (1989), Behar (1985), Lempert and Edwards (1983), Crawford and Nozza (1981), and Regan (1975) indicate that hearing protector effectiveness is substantially less than the NRR value indicated by the manufacturer. Furthermore, Regan (1975) found that earmuff type protectors yield the most attenuation and custom molded earplugs the least. Behar (1985) found that the measured NRR, in industrial situations, averaged 14.9 dB lower and reached 25 dB lower than the manufacturer's nominal value. Green et al. (1989) reported workers, who were using earplugs, were receiving one-third to one-half of the laboratory based NRR value and workers enrolled in an effective HCP obtain greater attenuation from their hearing protectors. Crawford and Nozza (1981) reported that the average attenuations of the earplugs were typically 50% of the manufacturer's values, except for user-molded earplugs whose field attenuation was near the laboratory values. Lempert and Edwards (1983) reported, ``In the majority of cases, workers received less than one-half of the potential attenuation of the earplugs'' and concluded, ``Regardless of the type of earplug used by a particular plant, a large portion of the workers received little or no attenuation.'' Hempstock and Hill (1990) reported that the workplace performance of earmuffs more closely approximated the laboratory performance than earplugs. For both earmuffs and earplugs, the measured workplace attenuations were lower and the standard deviations higher than those measured in the laboratory. The researchers attributed these results to the ease of fitting an earmuff compared to fitting an earplug. Their study revealed that the degradation was dependent upon the model of hearing protector and even differed between sites. Another result was that safety glasses substantially degraded the performance of earmuffs. Workers wearing safety glasses received approximately one-half of the laboratory attenuation. However, the researchers did not find that headband tension was a factor in the attenuation of earmuffs. Royster et al. (1996) found that the wearing of safety glasses reduced the attenuation of earmuffs by about 5 dB at all frequencies. Pfeiffer (1992) reported on studies of hearing protector effectiveness in [[Page 66424]] German industry. According to Pfeiffer earplugs provided between 10 and 15 dB less attenuation and earmuffs about 6 dB less in industry than in the laboratory. As part of the study, used muffs, which were not obviously defective (e.g., missing liners, headbands stretched out of shape, cushions missing or broken), were tested against new ones. The older earmuffs provided significantly less attenuation than new ones. The degradation of attenuation was dependent upon the model and frequency tested and exceeded 7 dB for some frequencies. Abel and Rokas (1986) reported that the attenuation of earplugs decreases as a function of wearing time and that head and jaw movement hastened the decrease. At Noise-Con 81, Berger (1981) also concluded that the performance of hearing protectors decreased as a function of wearing time. Kasden and D'Aniello (1976, 1978) found that the custom molded earplugs retained their attenuation after three hours of use during normal activity; however, typical earplug performance degraded over the three hours of use. Krutt and Mazor (1980) reported that the attenuation of mineral down earplugs decreased over a three-hour wearing period. These researchers did not observe any degradation of the attenuation of expandable foam earplugs. Cluff (1989) investigated the effect of jaw movement on the attenuation provided by earplugs and, determined the change in attenuation was dependent on type of earplug. The self-expanding viscose foam earplugs retained more of their attenuation than multi-flanged or glass-fiber earplugs. Casali and Grenell (1989) tested the effect of activity on the attenuation provided by an earmuff and found that only at 125 Hz was there a significant degradation in attenuation. Furthermore, the attenuation of an earmuff was highly dependent upon the fit. Royster and Royster (1990) report that the noise reduction rating (NRR) cannot be used to determine, or rank order, the real world attenuation of hearing protectors. Two individuals, using the same model of hearing protector, can obtain vastly different levels of attenuation. Royster and Royster stated that ``Products that are more goof-proof (earmuffs and foam earplugs) provided higher real-world attenuation than other HPDs.'' Casali and Park (1992) reported that the noise attenuation at 500 or 1000 Hz showed a high correlation with the total noise attenuation of hearing protectors. Therefore, the researchers believe that models can be developed to predict the total attenuation of hearing protectors based upon the measured attenuation at a single frequency. This would eliminate the need to derate the NRR so that it accurately reflects the field attenuation. The prediction method, they believe, will provide information on the adequacy of the worn hearing protector and can be used in objectively fitting the hearing protector. Berger (1992) reported on the progress of the ANSI Working Group S12/WG11, ``Field Effectiveness and Physical Characteristics of Hearing Protectors'', on developing or identifying laboratory and/or field procedure(s) which yield useful estimates of field performance of hearing protectors. The Working Group was established to address the clearly demonstrable divergence between laboratory and field attenuations of hearing protectors. Berger also summarized the results of 16 studies involving over 2,600 subjects on the field attenuation of hearing protectors. Earplug attenuation averaged about 25% of the published U.S. laboratory attenuations (range 6 to 52%) and earmuff attenuations averaged about 60% of the laboratory attenuations (range 33 to 74%). Royster et al (1996) reported on the progress of the American National Standards Institute Working Group (S12/WG11) charged with developing a laboratory methodology of rating hearing protectors which reflects the attenuation obtained by workers. Hearing protector attenuation measured using this methodology reflects the attenuation achieved by workers in a well managed hearing conservation program. The Working Group has developed a methodology and is in the process of drafting an ANSI standard around it. However, it will be some time before the standard is adopted. Even if the standard is adopted, there will be some legal ramifications, as the EPA would have to append their regulations to adopt this standard as the method for rating hearing protectors. As part of the testing of the methodology, the researchers found that the instructions which manufacturers include with their hearing protectors may be inadequate. Some of the test subjects could not properly don the earplug, from simply reading the manufacturer's instructions. As demonstrated above, many researchers have developed standardized methods of measuring the attenuation of hearing protectors in a laboratory setting. In addition, many researchers have compared the results of laboratory attenuations to estimated or measured field attenuations. However, based on a review of the major studies, MSHA notes that researchers have yet to develop standardized tests for measuring the field attenuation of hearing protectors. MSHA is cognizant of the potential for increased use of diesel equipment in mines in coming years. Diesel engine noise, a common mining noise control problem, is predominantly low frequency noise. In this regard, the Agency notes that hearing protectors are generally more effective in reducing high frequency noise than low frequency noise. Thus, noise from diesel engines contains the frequencies where hearing protectors are least able to attenuate the noise. The consequence is that hearing protectors poorly protect workers from excessive noise exposure when the source of the noise is a diesel engine. Some special hearing protectors, notably flat response hearing protectors, attenuate the sound across all frequencies the same. In developing a flat response hearing protector, the manufacturer degraded the attenuation at the high frequency instead of enhancing the low frequency attenuation. MSHA has concluded that at this time there is not a consensus among the scientific community as to a reliable method of predicting the actual attenuation received from hearing protectors in the mining environment. Additionally, experience indicates that miners do not receive the full attenuation measured in the laboratory (NRR). Research data indicate that many workers receive only a small fraction of the NRR. Therefore, the Agency has determined that one cannot rely solely on the EPA's NRR value. Because of the lack of an acceptable method of predicting hearing protector attenuation in the field, MSHA chose not to include a method for determining the adequacy of hearing protectors in the proposed noise regulations. It should be noted that in order to ensure hearing protection devices have undergone testing to ensure quality, MSHA is proposing that the definition of ``hearing protector'' permit only devices having a ``scientifically accepted indicator of noise reduction value.'' The Agency solicits comments as to alternatives to the NRR that could be used in this regard. Wearing of Hearing Protectors Proposed Sec. 62.120 would require that hearing protectors must be worn in certain cases: if noise exceeds the action level and a baseline audiogram has not taken place within 6 months after the exposure is determined; if an STS has been detected; and whenever a miner is [[Page 66425]] exposed to noise levels above the PEL. In such cases, proposed Sec. 62.125 would provide that the hearing protectors must be worn when the miner is ``exposed to sound levels which are required to be integrated into a miner's noise exposure measurement.'' This means that if a miner is required to wear hearing protectors, those protectors must be worn when that miner is exposed to sound levels above 80 dBA; sounds above that level have been demonstrated to be harmful, while such a demonstration has not been made for sound levels less than 80 dBA. MSHA recognizes that mine operators may want to develop particular policies on exactly when hearing protectors can be removed, and sees no need to delimit how this might be done. This practical approach, when taken together with the proposed requirements for employee training about hearing protectors and ensuring selection and proper fit of hearing protectors should facilitate the appropriate use of hearing protectors. Both MSHA's and OSHA's existing standards require that hearing protectors be worn when the employee's noise dose exceeds permissible levels. Neither standard, however, specifies a sound level below which workers could remove their hearing protectors. Although MSHA received general comments on levels above which hearing protectors should be worn, MSHA did not receive any specific comments addressing wearing practices or under what conditions it would be safe to remove a hearing protector. As has been emphasized, hearing protectors are only effective if they are worn. Chart NR1 illustrates that the amount of attenuation provided is highly dependent upon the duration a hearing protector is worn. BILLING CODE 4510-43-P See [GRAPHIC][TIFF
OMITTED]
TP17DE96.008
Chart NR1 demonstrates that if a hearing protector with an NRR of
29 dB is worn only half the time, the wearer will effectively obtain
only about 5 dB of attenuation. Thus, it is critical for mine operators
to ensure that the hearing protectors provided are worn. An NRR of 29
dB is among the highest NRR values reported by hearing protector
manufacturers.
Although MSHA did not ask a specific question in its ANPRM on
monitoring effective usage of hearing protectors, several commenters
recommended that MSHA require mine operators to supervise the proper
wearing of hearing protectors.
Despite mandatory use of hearing protectors, most workers in the
Abel (1986) study admitted to wearing their hearing protectors less
than 50% of the time. Further, many modified their hearing protectors
to provide greater comfort. Many of the modifications had a deleterious
effect on the attenuation.
In EARLOG 8, Berger (1981) contends that persons, who are more
prone to otitis externa (infections), would need to be monitored more
closely for failure to wear their hearing protectors. Persons with a
medical pathology of the ear are more likely to resist wearing a
hearing protector because of pain or extreme discomfort associated with
its use.
Based on the comments received and MSHA's experience, one critical
factor impacting on miner use is their concern that wearing hearing
protectors can, under some circumstances, create serious safety risks.
Apart from the information previously noted in connection with the
discussion of the proper selection of a hearing protector by miners
already suffering hearing loss, there is the issue whether hearing
protectors diminish the ability of even miners with good hearing to
hear ``roof talk.'' Prout et al. (1973) stated that:
Personal ear protectors do not generally prevent a miner from
hearing and analyzing roof talk when the noise level [sound level]
is sufficiently high as to require the use of ear protectors.
However, the ability to interpret roof warning signals is degraded
by the use of ear protectors in quiet. Consequently, ear protectors
should be removed when the noisy machines are shut down.
MSHA is reviewing its own records for further information on the
effect of hearing protectors on safety, and welcomes further
information from commenters. Of course, MSHA recognizes that failure to
wear hearing protectors may accomplish nothing in some cases. For
example, if some surface haulage fatal accidents result because high
sound levels from mining machinery mask the backup alarms, taking off
hearing protectors is not going to make the working environment any
safer. Indeed it is more likely that the miner would suffer a temporary
threshold shift which would make it
[[Page 66426]]
even more likely the backup alarm was missed.
MSHA's review of the literature and codes revealed that the U.S.
armed services and many international communities have specified sound
levels above which hearing protectors must be worn.
MSHA believes proposing specific trigger levels for hearing
protectors in specific circumstances would be burdensome and require
mine operators to conduct a comprehensive survey on each piece of
equipment. A more practical approach would be for mine operators to
ensure through their policies that hearing protectors are worn whenever
noise producing equipment is operating in the miner's work area, and
permit miners to remove their hearing protectors in areas with low
sound levels (below 80 dBA). This would minimize the miner's feeling of
isolation and communication difficulties caused by the wearing of
hearing protectors in such areas. As previously presented, most
researchers have indicated that sound levels below 80 dBA are not
hazardous.
The Agency, however, requests additional comment on this issue,
and, as noted above, on the specific issue of whether hearing
protection can be a safety hazard.
Fitting of Hearing Protectors
The proposal would require that mine operators ensure that hearing
protectors be fitted in accordance with manufacturer's instructions.
MSHA's existing noise standards do not address requirements for
fitting hearing protectors. OSHA's existing standards require that
employers ensure proper initial fitting and supervise the correct use
of all hearing protectors.
Many commenters on this issue recommended fitting.
Most of these specified use of the manufacturer's instructions for
fitting. A few of these specifically recommended that miners be fitted
by individuals trained in the fitting of hearing protectors. Other
commenters did not recommend fitting per se, but recommended that mine
operators provide a variety of types and sizes of hearing protectors to
ensure proper fit.
Several commenters indicated that some types of hearing protectors
do not require fitting. One commenter recommended use of Audiometric
Data Base Analysis (ADBA) to determine hearing protector effectiveness.
Other than ADBA, this commenter believed that there was insufficient
data at this time to recommend a criterion for proper fitting.
In EARLOG 17, Berger (1985) recommends that ``Prior to issuing HPDs
the fitter should visually examine the external ear to identify any
medical or anatomical conditions which might interfere with or be
aggravated by the use of the protector in question.''
In Communication in Noisy Environments, Coleman et al. (1984)
stated:
If a protector cannot be removed or fitted easily and quickly,
it may be either left on when not needed, possibly impairing
communication * * * or not fitted when needed, reducing the
protection from noise exposure. Ease of fitting is therefore a
desirable attribute for coal mining conditions.
Sweetland (1981) found that circumaural protectors were removed
and replaced more often than earplugs in mining conditions, which
could be taken as an indication that the former devices were easier
to fit and use. * * * Factors, such as the time required to hold a
compressible foam plug in position for it to achieve its design
performance, and the procedure required to fit inserts correctly,
which involves reaching around the back of the head to grasp the
earlobe, can reduce their acceptability for mining conditions.
At Noise-Con 81, Berger (1981) reported that the attenuation was
greater when noise was used to help in the fitting of hearing
protectors although the variability was not significantly greater.
Carter and Upfold (1993) investigated methods of determining the
attenuation provided by foam earplugs. Both an earmuff with an earphone
and a cushion with an earphone gave results comparable to the standard
laboratory method and could be used to estimate the group attenuation
of foam earplugs. However, the results of the measured attenuation for
individuals were not as good as that for the group. The researchers,
therefore, concluded that neither method with earmuffs or cushions
could be used to determine the attenuation provided by a foam earplug
to an individual, although the methods could be used to check the
effectiveness of fitting and training of a group.
Merry et al. (1992) reported that subjects obtained greater
attenuation from earplugs if an experimenter directs the fitting using
the subject's response to noise when compared to subjects simply
reading the manufacturer's instructions and inserting their own
earplugs.
Chung et al. (1983) reported that the major factor affecting the
earmuff performance was the fit which is dependent upon headband
tension. Adequate tension is necessary for good attenuation. However,
high headband tension generally caused discomfort. The same occurred
when the earmuff seal was cracked. However, no effect of the age of the
earmuffs was observed. Chung et al. concluded that training and proper
fitting can increase the effectiveness of earmuffs, thus protecting
workers from incurring noise-induced hearing loss (NIHL).
Phoon and Lee (1993) studied workers who developed NIHL in
Singapore. For 103 of 156 earplug users (66%) who developed NIHL, there
was a mismatch between the earplug and the size of both ear canals. In
13.5% of these workers, the mismatch occurred in one ear.
Royster et al. (1996) reported the manufacturer's instructions were
not always adequate in describing the procedures for donning a hearing
protector. Several subjects improperly inserted earplugs during a
laboratory experiment of hearing protector attenuation. The
inappropriately inserted earplugs would be considered improperly fitted
hearing protectors.
ANSI S3.19-1974, ``Method for the Measurement of Real-Ear
Protection of Hearing Protectors and Physical Attenuation of
Earmuffs'', recommends that 60 to 70 dB white noise be used when the
subject fits a hearing protector. White noise has essentially a random
spectrum with equal energy per unit frequency bandwidth over a
specified bandwidth.
As described above, researchers have identified several techniques
for both subjectively and objectively evaluating the fit of hearing
protectors. While many of the techniques show promise, there is no
consensus as to which method is best. Most techniques are applicable to
a specific type of hearing protector and are not practical for use by
many mine operators. These techniques are discussed further under the
Hearing Protector Effectiveness section of this preamble.
MSHA also considered the use of ADBA (Audiometric Data Base
Analysis) to determine the effectiveness of hearing protectors in lieu
of subjective fitting requirements. Since ADBA does not provide
immediate feedback as to the fit of a hearing protector, MSHA has
concluded that ADBA is inappropriate for determining the fit of a
hearing protector. ADBA analysis requires multiple subjects, not an
individual, before a conclusion of adequacy is determined. Besides ADBA
determines the adequacy of the HCP (protecting the hearing acuity of a
group of workers), not the adequacy of protecting an individual.
Moreover, MSHA believes that ADBA is not practical for most mining
operations as discussed under the Evaluation of HCP effectiveness
section of this preamble. Furthermore, ADBA requires several audiograms
which are conducted on an
[[Page 66427]]
annual basis. In the interim, the hearing acuity of a miner could be
irreversibly damaged.
As supported by the researchers and many commenters, MSHA agrees
that proper fitting is necessary to ensure optimal effectiveness of
hearing protectors and that it should not be left solely up to the
individual miner to determine if the hearing protector fits properly.
Further, MSHA is concerned that some manufacturer's instructions are
not adequate to ensure the proper fitting of a hearing protector.
Although comfortable hearing protectors should be provided, MSHA is
also concerned that some miners may choose hearing protectors that are
too loose or otherwise improperly fit, and consequently not achieve
adequate noise reduction.
In light of the wide variety of hearing protectors available, the
broad range of subjective fitting procedures, and the lack of consensus
on an objective fitting method, MSHA concluded that the manufacturer's
instructions are the best criteria for fitting. MSHA encourages
commenters to provide information on any standardized methods of
testing the fit of hearing protectors.
Maintenance of Hearing Protectors
MSHA's proposal would also require mine operators to ensure that
hearing protectors are maintained in accordance with manufacturer's
instructions. Neither MSHA's nor OSHA's existing noise standards
address requirements for maintaining hearing protectors.
MSHA recognizes that it is difficult to keep hearing protectors
clean in the mining environment. Using contaminated hearing protectors,
however, may contribute to a medical pathology of the ear. Once the
skin has been abraded or inflamed, it is easier for microorganisms
normally found in the ear to invade the skin. When hearing protectors
are implicated as the cause of inflammation of the external ear canal
(otitis externa), often the hearing protector is contaminated with an
irritating or abrasive substance. This situation can be corrected with
proper cleaning of the hearing protector before use.
MSHA's proposal is designed to ensure that miners not develop
medical problems while they are attempting to protect themselves from
the hazard of noise. If an earplug cannot be adequately cleaned, then
the mine operator would have to replace it.
In addition to providing guidance on the fitting of hearing
protectors, manufacturers also provide instructions on the proper care
and cleaning of their hearing protectors. Many recommend soap, warm
water, and careful rinsing. Solvents and disinfectants generally are
discouraged as cleaning agents because they can cause skin irritation
and some can damage the hearing protector. In most cases, the proper
insertion technique for earplugs would just be a matter of applying
common sense, i.e., cleaning the hands before rolling and/or inserting
earplugs.
Several commenters addressed hygiene problems when the hearing
protectors become dirty. One of these commenters stated that miners
would need to clean their permanent hearing protector daily and that
irritation due to sweating and skin contact with the hearing protector
can be a problem associated with its use.
In EARLOG 5, Berger (1980) states that permanent [non-disposable]
hearing protectors should be replaced between two and 12 times per
year. The constant wearing of hearing protectors causes them to lose
their effectiveness. For example, headbands on earmuffs can lose their
compression ability; the soft seals surrounding the ear cup on earmuffs
can become inflexible; and plastic earplugs can develop cracks, can
shrink, or can lose their elasticity.
As referenced in EARLOG 17 (Berger, 1985), Forshaw and Cruchley
studied the effects of washing the hearing protectors worn by long-
range patrol aircraft crews. The crews were divided into three groups:
one group wore pre-molded earplugs; the second group wore foam earplugs
washed after each use; and the third group wore foam earplugs which
were washed weekly. Examinations by medical officers revealed no fungal
or clinically significant bacterial infections among the three groups.
MSHA also reviewed standards from the U.S. Armed Forces and the
international community on the topic of hearing protector maintenance.
The consensus of the standards was that damaged or deteriorated hearing
protectors must be replaced.
Miners have also been known to alter the hearing protection
provided to make them more comfortable. Such alterations have included
cutting off the end of earplugs or stretching out the head-band on
earmuffs. These alterations can significantly decrease the hearing
protector's attenuation.
Hearing protectors can also be damaged from exposure to heat, cold,
ozone, chemicals, or dirt. Such conditions are common in the mining
industry, and mine operators must periodically check the hearing
protectors provided and replace them when damage is found.
Hearing Protectors Provided at No Cost to Miner
The proposal would also require the mine operator to provide
necessary replacements at no cost. This is intended to ensure that the
mine operator repairs or replaces a miner's hearing protector when it
becomes damaged or deteriorated to the point that the required
protection is compromised.
MSHA believes that it is essential for mine operators to replace
worn-out or damaged hearing protectors in order to maintain their
effectiveness. This is in agreement with the international community
and the U.S. armed services. Damaged or deteriorated hearing protectors
do not provide their designed optimum amount of protection. Further,
MSHA believes that the manufacturer's instructions are the best source
of information as to the proper procedures for maintaining a particular
protector.
MSHA's existing noise standards do not specifically address the
replacement of hearing protectors. OSHA's noise standards simply
require that hearing protectors be replaced as necessary.
MSHA received no direct comments to its ANPRM on the issue of mine
operators supplying commercially available hearing protectors at no
cost to the miner. However, several commenters supported adopting
requirements similar to OSHA's which includes provisions for providing
hearing protectors at no cost to the worker.
Replacement of hearing protectors would be based on the
manufacturer's instructions, upon finding any deterioration that could
adversely affect the hearing protectors attenuation, or upon a need for
the miner to choose a different hearing protector due to a medical
pathology caused or aggravated by the initial hearing protector
provided (see following section which discusses medical pathology). For
example, manufacturers of disposable earplugs may state in their
instructions that they should be replaced after each use.
Replacement of Hearing Protector Due to Medical Pathology
MSHA's proposal would also require the mine operator to provide an
individual miner with a different, more acceptable, type of hearing
protector when presented with evidence of a medical pathology (e.g.,
otitis externa or contact dermatitis). The definition of ``medical
pathology'' is intended to be broad enough to cover injuries. If, for
example, a miner would suffer a burn in the ear canal which would
preclude the wearing of earplugs, an employee who
[[Page 66428]]
elected earplugs should have the opportunity to now select a muff.
MSHA does not intend to require that the evidence of a medical
pathology be a diagnosis by a physician specialist--nor to require mine
operator action without any evidence whatsoever. The goal here is a
practical one: exchange the hearing protector if there appears to be a
medical problem. A preliminary diagnosis of medical pathology by a
family physician or nurse should be accepted by an employer for the
purposes of this requirement.
In EARLOG 17, Berger (1985) discusses some predisposing factors for
otitis externa. These include allergy to chemicals or hair dyes and
sprays; dermatitis; chronic draining middle ear infections; excessive
cerumen (ear wax); and systemic conditions which lower the body
resistance, such as anemia, vitamin deficiencies, diabetes, and
endocrine disorders. Disposable hearing protectors may be warranted for
those individuals prone to infections. The researcher reported that the
prevalence of otitis externa is approximately 2% in both users and
nonusers of hearing protectors. He stated that:
Although hearing protection devices should not be worn in the
presence of some preexisting ear canal pathologies, and care must be
exercised regarding selection and use under certain environmental
conditions, regular wearing of HPDs does not normally increase the
likelihood of contracting otitis externa.
Furthermore, Royster and Royster in EARLOG 17 (Berger, 1985)
reported on a situation in which underground miners in a warm and humid
environment were experiencing otitis externa. Switching from a pre-
molded vinyl earplug to a foam earplug decreased the incidence of this
condition.
Although documented cases of hearing protectors causing infections
in the ear canal or on the skin surrounding the ear are not prevalent,
MSHA is aware of at least one reported case of an ear infection in the
mining industry specifically attributed to the use of hearing
protectors.
MSHA's existing noise standards do not specifically address the
replacement of hearing protectors. OSHA's noise standards simply
require that hearing protectors be replaced as necessary.
Based upon the research and several international standards, MSHA
believes that hearing protectors need to be replaced whenever a medical
pathology is present. Such replacements would also be at no cost to the
miner.
Section 62.130 Training
Summary
Proposed Sec. 62.130 would provide the specifications for
instruction and certification of training required by the proposed
rule. Proposed Sec. 62.120 requires such training for all miners
exposed above the action level, and annually thereafter if still
exposed above that level. Proposed Sec. 62.180 requires retraining for
every miner who incurs an STS.
Miners would receive instruction in the value of hearing
protectors, selection and fitting of protectors, and proper use of such
protectors. Miners would also receive instruction as to the operation
of an operator's hearing program and in the mine operator's noise
control efforts. There are no special qualifications for instructors,
nor any specifications on the hours of instruction. Training is
required to be provided without cost to the miner. The mine operator
would be required to certify the completion of any training required by
this part, and maintain the most recent certification for a miner at
the mine site for as long as the miner is required to use hearing
protectors or be enrolled in an HCP, and at least 6 months thereafter.
MSHA considered whether the requirements of part 48, ``Training and
Retraining of Miners,'' were adequate to ensure the training required
under this part. The requirements of part 48 specify the initial and
annual retraining of all miners in a list of subjects, many specified
in the law itself (section 115 of the Mine Safety and Health Act). The
importance of this training is emphasized by statutory requirements for
the submittal of training plans, on the specification of the hours to
be devoted to the training, and on the qualifications of instructors.
Training is required on noise, but it is in general terms, covering the
purpose of taking exposure measurements and on any health control plan
in effect at the mine. Mine operators may provide additional training,
but the topics that need to be covered often make this impracticable
within the prescribed time limits.
After considering the available information about the importance
and prevalence of training requirements, and based upon its experience
in implementing the requirements of part 48, MSHA has determined that
the requirements of part 48 do not provide adequate noise training for
those miners for whom exposure is clearly a problem. Part 48 training
is neither comprehensive enough to provide such miners with the level
of education needed for the proper use of hearing protection devices,
nor, in the case of noisy mines, detailed enough on methods to reduce
sound levels.
Nevertheless, MSHA believes compliance with this proposal can in
many cases be fulfilled at the same time as scheduled part 48 training.
The Agency does not believe special language in proposed part 62 is
required to permit this action under part 48, but welcomes comment in
this regard. Mine operators who can do so are free to fulfill their
training requirements under Sec. 62.120 by covering the topics in
initial and annual part 48 training, and so certify on the separate
form required by this part. If incorporated into part 48, mine
operators would, however, be required to submit a revised training plan
to the local district office for approval. Some mine operators may not
have room in their part 48 plans, however, to be able to incorporate
these topics. Moreover, some training required under the proposal will
clearly not fit within a regular schedule: e.g., the training required
by Sec. 62.180 whenever a standard threshold shift in hearing acuity is
detected.
MSHA has endeavored to make the training requirements as simple as
possible. If conducted separate from part 48, there are no
specifications on trainer qualifications, no minimal training time, nor
any training plans. If however the training is incorporated into part
48, then all applicable part 48 requirements will have to be met.
Background
Training requirements are a mainstay of mine safety and health.
Although MSHA has no training requirements in its existing noise
regulations, the general training requirements set forth in part 48
require basic training as to the purpose of taking noise measurements,
and in any health (noise) control plans that are in effect at the mine.
Numerous commenters responding to MSHA's ANPRM, expressed
considerable support for miner training on noise and its effects and
believed that it is an essential element of any effective HCP. Many of
these commenters specifically supported annual refresher training.
Commenters differed, however, in their opinions as to how training
could best be accomplished. Several commenters recommended that MSHA
incorporate any training requirements related to this standard into
MSHA's existing training requirements under 30 CFR part 48--Training
and Retraining of Miners. A few commenters believed that the training
requirements in MSHA's part 48 were adequate and that no additional
instruction was needed.
[[Page 66429]]
One commenter suggests that the initial training class be limited
to less than 10 individuals (Berger, 1988; Royster and Royster, 1985).
Although training may best be accomplished in small groups, MSHA's
proposal would not limit the size of any training classes.
There is considerable precedent for requiring training as part of
noise control programs.
OSHA's noise standard has training requirements which are similar
to those in MSHA's proposed noise standard with a few exceptions. These
exceptions are discussed later in this section.
In OSHA's 1981 preamble (46 FR 4157), Morrill stresses the
importance of worker education in overcoming workers objections to
wearing hearing protectors. This document quotes a Dr. Maas as saying
that, ``Supervisors must sell employees on the need and value of
hearing protection devices. When employees understand what the
protective measure is for, it will be accepted because the employee
realizes it is for his own good.'' A number of comments to OSHA's
Hearing Conservation Amendment (46 FR 4157) indicated that workers are
reluctant to appear weak or ridiculous as a result of wearing hearing
protectors. Suter (1986) states, ``Workers who understand the mechanism
of hearing and how it is lost will be more motivated to protect
themselves.'' Other researchers concur with this opinion (Wright,
(1980) and Royster et al., (1982)).
CAOHC (Miller, 1985) states the following regarding the need for
training as part of an effective program (HCP):
A critical component of the OHC [Occupational Hearing
Conservation] program is the employee education program (EEP). In
many respects, the EEP is the most important aspect of the OHC
program since it is designed to increase the auditory consciousness
of the employee regarding the hazardous effects of noise exposure
and by so doing to get him to use effective forms of PHPD's
[personal hearing protective devices] conscientiously and
consistently. Such use of PHPD's will actually protect the worker's
hearing, while the other aspects of the program, important as they
are, will not do so. No amount of noise monitoring or audiometric
testing, for example, will protect hearing.
MSHA also reviewed the training requirements set forth in
international standards and those of the U.S. Armed Services. The
consensus was that training was necessary; however, the training
interval was not always specified.
Training About Hearing Protector Selection and Use
Section 62.130(a) specifically provides that the training is to
include instruction in--
(1) the effects of noise on hearing;
(2) the purpose and value of wearing hearing protectors;
(3) the advantages and disadvantages of the hearing protectors to
be offered;
(4) the care, fitting, and use of the hearing protector worn by the
miner;
(5) the general requirements of the regulation;
(6) the operator's and miner's respective tasks in maintaining mine
noise controls; and
(7) the purpose and value of audiometric testing and a summary of
the procedures.
OSHA requires annual training on the same elements except it does
not require training on the requirements of its noise standard. It is
MSHA's view, however, that some training on the requirements of the
standard is necessary in order for employees to understand the role
hearing protection plays in a broader protection scheme.
Purpose, Advantages, and Disadvantages of Hearing Protectors Offered
Instruction on this topic would help the miner make an informed
choice as to which hearing protector to use. This basic instruction
would be initially required when the mine operator first determines the
miner's noise exposure exceeds the action level. Moreover, pursuant to
proposed Sec. 62.125, this instruction must be provided at least once
before the miner must make a selection of a hearing protector.
Furthermore, it would need to be repeated annually thereafter, because
hearing protectors should be replaced periodically.
MSHA anticipates the training would address specific advantages and
disadvantages of earmuffs, earplugs, and canal caps as they relate to
the needs of the miner and the specific conditions at the mine. For
example, an electrician who opts to use an earmuff must understand the
need to use one with dielectric properties to minimize the chance of
incurring an electrical shock when working around energized equipment.
An over-the-head earmuff is unsuited for those miners required to wear
hardhats: the earmuff would interfere with the wearing of the hardhat
as the hardhat could not be placed over the headband. In addition, the
mine operator should discuss the specific advantages and disadvantages
of any special hearing protectors offered such as active noise
reduction, level-dependent, flat-response, and notch-amplification
hearing protectors, or a communication headset. For example, a miner
with a sensorineural hearing loss in the higher frequencies may require
a different type of hearing protector than a miner with a conductive
hearing loss across all frequencies. Accommodating the hearing loss may
require a level-dependent, active noise reduction, or notch-
amplification hearing protector to improve the miner's ability to
communicate and hear warning signals in a noisy environment. All miners
need to understand the relative advantages and disadvantages of
earmuffs and earplugs as they are not at all obvious: hence, the
necessity for training.
Some advantages of earmuffs (circumaural hearing protectors)
include: they are easily donned and removed by the miner when working
in intermittent noise; they offer protection against dust in the ear
canal; they are not easily misplaced or lost; they fit people with
unusually shaped ear canals; and they can be worn over earplugs. Berger
in EARLOG 3 (1980), and Coleman et al. (1984) reported that one major
disadvantage of earmuffs is that they hinder a miner's ability to
localize the direction of sounds. If the miner's safety depends on the
ability to localize sounds, then this disadvantage would preclude the
use of earmuffs. Other potential disadvantages of earmuffs include:
discomfort; headache; a feeling of claustrophobia; excessive warmth and
perspiration under the muff seal; and skin irritation. Earmuffs may
present problems if the miner wears safety glasses or earrings.
Eyeglass temples reduce the attenuation afforded by earmuffs.
In EARLOG 19, Berger (1988) states that the use of eyeglasses with
an earmuff can break the seal of the earmuff and cause a loss of
attenuation of up to 6 dB depending on the frequency of the noise.
Royster et al. (1996) tested the effect of wearing two different
safety glasses on the attenuation of an earmuff. The researchers found
that the attenuation was reduced by about 5 dB across all frequencies.
Barham et al. (1989) investigated the effects of safety glasses and
hair on the effectiveness of earmuffs. The wearing of safety glasses
decreased the noise reduction up to 4 dB depending upon the frequency.
The glasses had slender and flexible wire-reinforced side frames so
that the side frames would fit close to the head. Not only did the
safety glasses decrease the average noise reduction, they also reduced
the variability (standard deviation) of the
[[Page 66430]]
noise reduction realized among the individuals. The type of hair and
its length influenced the noise reduction provided by earmuffs.
Individuals with short hair realized up to 5 dB more protection,
depending upon the frequency, than individuals with long or curly hair
and beards.
Michael (1991) asserts that glasses with plastic temples may cause
a loss of attenuation from 1 to 8 dB, due to breaking the seal of the
earmuff. In some cases, this loss can be substantially reduced if
small, close fitting wire temples are employed.
Nixon and Berger (1991) report that temples of eyeglasses reduce
the efficacy of earmuffs normally by 3 to 7 dB provided the cushions of
the earmuffs are in good shape. This effect varies among earmuffs and
it also depends upon the style and fit of the eyeglasses. To minimize
the effect of wearing eyeglasses, the temples should be as thin as
possible and fit close to the side of the head.
Savich (1979) measured the noise attenuation of earmuffs. Because
of long hair and safety glasses, the earmuffs provided less attenuation
than expected based upon laboratory tests. Furthermore, head size has a
significant influence on the attenuation because of different clamping
forces. Increased clamping force increases the attenuation.
Some advantages of earplugs include: they are cooler, if the miner
has to work in a hot, humid environment; they are more easily worn with
safety glasses, hardhats, and other personal safety equipment (e.g.,
air-purifying or welding helmets); and they fit miners who have
extremely large external ears. One disadvantage of an earplug is that
inserting it into the ear canal could present a personal hygiene
problem if the miner removes and reinserts it several times during the
day. A miner who is susceptible to ear infections or secretes
significant amounts of ear wax may be better suited for using earmuffs.
As noted earlier in this section, training is critical to miner
cooperation. MSHA has concluded, after reviewing the scientific
literature, U.S. Armed Forces regulations, and standards from the
international community, that requiring the mine operator to instruct
each miner required to wear hearing protectors on the purpose,
advantages, and disadvantages of the choices available will facilitate
hearing protector use and effectiveness.
Care, Fitting, and Use of the Hearing Protector Selected
In response to MSHA's ANPRM, many commenters supported the need to
train employees on the proper fitting, care, and use of hearing
protectors.
Merry et al. (1992) studied the effect of fitting instructions on
the resulting attenuations of earplugs. Novice subjects were given
earplugs. The difference in their hearing thresholds between the
unoccluded and occluded conditions was the attenuation of the earplug.
The subjects obtained greater attenuation whenever the experimenter
assisted the subject in fitting the earplug than when the subject
merely read the manufacturer's instructions before donning the earplug.
Furthermore, the researchers noted that the attenuations obtained by
the subject when just the manufacturer's instructions were read is
comparable to the attenuations measured under industrial conditions.
Casali and Lam (1986) reported that the proper design and
presentation of user insertion/donning instructions are critical to the
amount of attenuation afforded by hearing protectors. They found that
in some cases, the magnitude of protection afforded by the use of
earplugs exhibited greater than a twofold increase when training ranged
from no instruction to detailed and model instruction. Their study also
showed that the attenuations afforded by earmuffs and earcaps were not
as influenced by the level of instruction as were earplugs. Casali and
Lam concluded that any instruction technique provided an improvement in
attenuation over no instruction at all. However, they found no
statistically significant differences among the type of instruction
used. They also stated that regardless of the insertion/application
instruction type selected, it is imperative that workers be retrained
periodically in hearing protector insertion practices, hearing
protector sizing, and hearing protector care to maintain optimal
hearing conservation.
Royster et al. (1996) had novice users of hearing protectors don
the protectors after reading the manufacturer's instructions. Since
some users failed to properly don the hearing protectors, the
researchers concluded that the instructions provided by the
manufacturer were not always adequate. Consequently, additional
instruction should be provided to assure the proper donning of hearing
protectors.
Barham et al. (1989) reported that the noise reduction achieved by
an earmuff improved by approximately 4 dB for a group and up to 6 dB
for an individual following instruction on its use. Not only did the
attenuation increase but also the standard deviation (a measure of
variability) decreased. Therefore, instruction significantly improved
the noise reduction achieved by the wearer of an earmuff.
Park and Casali (1991) studied the effects of two levels (minimal
and detailed) of instruction on the measured attenuation obtained by
regular hearing protector users. The users were tested using different
hearing protectors from the ones they normally wore. The amount of
noise attenuation increased and the standard deviations decreased when
the investigators presented the instructions and demonstrated the
proper manner to don and doff hearing protectors as compared to the
employees simply reading the instructions. The efficiency of earplugs
was found to be highly sensitive to the degree of instruction while
earmuffs and canal caps were not.
MSHA believes that training is critical to the effective use of
hearing protectors, and that miners must be shown how to use, fit, and
care for their hearing protectors if they are to be effective. Further,
the instructions should be repeated at yearly intervals to maintain
effectiveness. Simply instructing the miner to read manufacturer's
directions on the hearing protector container would not be adequate.
MSHA is concerned that some manufacturer's instructions are inadequate
for the proper fitting of hearing protectors. The effectiveness of
hearing protectors can be highly dependent on how they fit the
individual wearer. Not all people will achieve the same degree of fit
or effectiveness from the same hearing protector.
Training About Hearing Conservation Program and Operator Noise Controls
OSHA's noise standard has similar training requirements with the
exception that they do not require training on the respective
responsibilities of the employer and employee in maintaining controls.
MSHA has determined that training miners enrolled in an HCP on the
respective responsibilities of mine operator and miner is necessary to
obtain maximum effectiveness from an HCP. Miner cooperation and support
is required, for example, to ensure:
(1) The hearing protector provided fits properly each time it is
donned;
(2) The hearing protector is worn whenever the miner is exposed to
hazardous sound levels;
(3) Exposure to high sound levels is avoided for at least 14 hours
before taking the baseline audiogram;
(4) Participation in the audiometric testing;
(5) Cooperation with any administrative control(s) instituted by
the mine operator; and
[[Page 66431]]
(6) Use and maintenance of the engineering noise controls provided
by the mine operator.
MSHA believes that a miner's understanding and motivation would be
enhanced by conducting initial and annual training in these areas. The
rationale for retraining miners who suffer an STS is discussed in
connection with Sec. 62.180, Follow-up corrective measures when STS
detected.
MSHA believes that a miner must also be trained to understand the
audiometric tests. This will enable miners to understand their own
results and determine the effect of wearing hearing protectors.
Effectiveness. MSHA has endeavored to make the training
requirements as simple as possible. If conducted separate from part 48,
there are no specifications on trainer qualifications, no minimal
training time, nor any training plans. If however the training is
incorporated into part 48, then all applicable part 48 requirements
will have to be met.
While this approach reduces the burden on those mine operators who
cannot incorporate part or all of the noise training into part 48
training, it also means that certain safeguards in effect for part 48
training will not be directly applicable to that noise training not
provided during part 48 training. There would be no review of a noise
training plan, for example, to ensure that the instruction is adequate
or that the training is to be given in the language spoken by most of
the miners. Comments on this point are solicited.
The Agency believes it can ensure the noise requirements have been
fulfilled by checking with exposed miners to ensure that the required
training elements have been covered and that the certifications are
valid.
Certification. Section 62.130(b) of the proposal would require
that, upon completion of any training required under this part, the
mine operator certify the date and type of training (initial or annual)
given each miner. The certification would be signed by the person
conducting the training.
It is standard practice in the mining industry to require
certification of training, as a way of facilitating compliance.
Training received under part 48 must be certified. The certification
form used for part 48 does not have a separate line on which to
indicate that the training required under the proposed noise standard
has been completed; moreover, this would not be suitable in any event
for noise training given independently of part 48 training as may often
be the case.
MSHA believes that it is important to record the type and date of
any training conducted under its proposed noise regulations. A written
record, together with miner interviews, provide the Agency necessary
checks to ensure the training is provided as required with only a
minimal burden.
An optional approach on which MSHA would welcome comment is to
simply require that a mine operator must, upon request, give an MSHA
inspector copies of all materials related to the employer's noise
training program. This is the approach taken by OSHA.
Retention. Section 62.130(b) of MSHA's proposal would require the
mine operator to retain the most recent certification at the mine site
for as long as the miner is exposed to noise above the level which
initiated the training and for at least six months thereafter.
MSHA has a retention requirement for part 48 training. Part 48
training records are to be retained for two years for currently
employed miners or for 60 days after the termination of employment.
OSHA has no retention requirement for training records.
The Agency believes it is important to retain training records in
order to verify that the required training has been provided, as with
the certification requirements. The retention requirement is short and
not burdensome: only the most recent record must be retained, and then
only until the miner's exposure drops beneath the level which initiated
the training (or 6 months after cessation if employment should that
come before the exposure level has dropped).
Section 62.140 Audiometric Testing Program
This section of the proposal would establish basic procedures for
the audiometric testing program in which those miners enrolled in a
hearing conservation program (HCP) will participate. It includes
provisions for: qualifications of personnel performing the audiograms,
baseline audiograms, annual audiograms, and supplemental baseline
audiograms.
MSHA is seeking explicit comment on a number of points. What
follows is a brief summary of some key features of this section of the
proposal.
With respect to qualifications of personnel, MSHA would require
that an ``audiologist'' be certified by the American Speech-Language-
Hearing Association or licensed by a state board of examiners.
``Qualified technicians'' would be required to have been certified by
the Council for Accreditation in Occupational Hearing Conservation
(CAOHC) or another recognized organization offering equivalent
certification. CAOHC or equivalent certification would assure that the
technicians are qualified. MSHA is not proposing to require
qualifications for physicians.
It is critical to obtain a baseline audiogram before exposure to
hazardous noise. If this is not possible, then the baseline is to be
obtained as soon as is reasonably possible. Due to remote locations and
intermittent operations of many mines, MSHA determined that allowing
six months (or 12 months if a mobile test van is used) for obtaining
the baseline audiogram was reasonable. The 12 month period would allow
mine operators to schedule many baseline and annual audiograms
simultaneously, and thus, substantially reduce the cost when mobile
test vans are used. Pursuant to proposed Sec. 62.120(b), miners would
be provided hearing protection until such time as the baseline
audiogram is conducted; and in the event the miner has to wait for more
than 6 months to get a baseline audiogram because a mobile test van is
used, the operator would be required to ensure the use of hearing
protection.
MSHA has also determined that a 14-hour quiet period should precede
the baseline audiogram to ensure a valid result: hearing protectors
will not be considered a substitute for a quiet period under the
proposal, and miners are to be notified of the importance of compliance
with the quiet period.
MSHA has concluded that audiograms need to be provided annually for
miners enrolled in an HCP. MSHA is not proposing to require this quiet
period for annual audiograms, though it may be in the mine operator's
interest to do so.
Background
Under existing standards for coal mines, MSHA requires pre-
employment and periodic audiograms at those mines under a hearing
conservation plan, but includes no specific procedures or time frames
for obtaining these audiograms. Moreover, at present, less than 1% of
the coal miners are covered by a hearing conservation plan. MSHA
currently does not have any requirements addressing audiometric testing
for metal and nonmetal mines.
OSHA's noise standard also contains requirements for qualifications
of personnel and for baseline, annual, and supplemental baseline
audiograms. The limited number of differences between the OSHA standard
and the MSHA proposal are noted in the discussion that follows.
[[Page 66432]]
Qualifications of Personnel
Section 62.140(a) of MSHA's proposal would require that audiometric
tests be conducted by a physician, an audiologist, or a qualified
technician who is under the direction or supervision of a physician or
an audiologist.
MSHA would require that an ``audiologist'' be certified by the
American Speech-Language-Hearing Association or licensed by a state
board of examiners. ``Qualified technicians'' would be required to have
been certified by the Council for Accreditation and Occupational
Hearing Conservation (CAOHC) or another recognized organization
offering equivalent certification.
OSHA's noise standard requires that--
Audiometric tests shall be performed by a licensed or certified
audiologist, otolaryngologist, or other physician, or by a
technician who is certified by the Council of Accreditation for
Occupational Hearing Conservation, or who has satisfactorily
demonstrated competence in administering audiometric examinations,
obtaining valid audiograms, and properly using, maintaining and
checking calibration and proper functioning of the audiometers being
used. A technician who operated microprocessor audiometers does not
need to be certified. A technician who performs audiometric tests
must be responsible to an audiologist, otolaryngologist or
physician.
MSHA received comments that specifically addressed the
qualifications of persons conducting audiometric tests. Some commenters
were concerned that physicians may not have the specific knowledge
necessary to conduct audiometric testing. One of these commenters
stated that:
* * * many physicians are not well versed in problems of
audition, especially occupational noise induced hearing loss [NIHL].
If physicians are to be included in the list of acceptable
supervisors, they should be limited to ``qualified occupational
physicians,'' or perhaps ``qualified occupational physicians with
audiological experience.''
Other commenters recognized that technicians need specific
training, but disagreed as to whether formal certification was
necessary. Many commenters specifically stated that MSHA should require
CAOHC certification as the minimum acceptable criteria for training of
audiometric technicians.
Many commenters specifically recommended or implied that MSHA treat
technicians who operate microprocessor audiometers the same as
technicians who operate other types of audiometers. One stated that:
The use of a microprocessor audiometer does not guarantee a
valid, reliable audiogram, nor does it obviate the need for the
technician to be familiar with the important interpersonal and
procedural details of administering an audiogram and providing
feedback to the employees.
Other commenters, however, stated that persons who operate
microprocessors do not need to be certified, but it was unclear whether
they thought that training and demonstration of competency would be
necessary for such technicians. Finally one commenter wanted ``maximum
flexibility in audiometric testing.''
One commenter on this issue stated that:
* * * We do not believe that there are other qualified medical
personnel [other than an audiologist or physician] who understand
the principles of interpreting an audiogram appropriately.
The U.S. Army (1991), Air Force (1991), and Navy (1994) regulations
require that a physician, audiologist or technician conduct the
audiometric tests. The audiometric technician must be CAOHC certified
or certified through military medical training and be under the
supervision of a physician or audiologist.
MSHA believes that it is unnecessary to specify that physicians be
``licensed'' or ``qualified.'' All states require physicians to be
licensed. MSHA is concerned, however, that licensing does not imply
qualification to conduct audiometric testing, evaluate audiograms, and
supervise technicians in these areas. The Agency expects physicians to
exercise professional judgement when evaluating their own
qualifications to conduct audiometric testing. In addition, the medical
profession enforces a high degree of accountability and ethical
standards. Nevertheless, further comment is requested on this issue.
MSHA believes that certification or licensing of audiologists is
essential to an effective HCP. Properly trained and certified
audiologists would be qualified to conduct audiometric testing,
evaluate audiograms, and supervise technicians. Unlike physicians, MSHA
believes that certification or licensing presupposes that the
audiologist would be qualified to conduct audiometric testing.
With respect to qualified technicians, MSHA considered the comments
on this topic filed in response to the ANPRM and concluded that
qualified technicians need to be certified by CAOHC or by an
organization offering equivalent training. CAOHC or equivalent
certification would assure that the technicians are qualified. While
MSHA recognizes that the OSHA standard allows physicians discretion to
judge the qualifications of technicians, MSHA believes requiring
certification is not restrictive and best ensures quality control. MSHA
would also require CAOHC or equivalent certification for technicians
who operate microprocessor audiometers. The Agency concludes that
requiring CAOHC or equivalent certification would not be overly
burdensome on the mining industry.
NIOSH commented on OSHA's proposed rule, and again on MSHA's ANPRM,
that there may not be enough CAOHC courses offered in a given year, or
in a wide enough geographical area, to require that all technicians be
CAOHC certified. OSHA's preamble (46 FR 4128) in 1981 indicated that,
at that time, there were about 6,700 CAOHC certified technicians and
700 course directors. Since 1981, however, the number of CAOHC course
directors has decreased to about 400, but the number of certified
technicians has increased to about 14,000. Although this number of
certified technicians may be sufficient to conduct the required
audiograms in the mining industry, MSHA believes that promulgation of
this rule will result in even more individuals seeking certification.
In addition to CAOHC certification for audiometric technicians, MSHA
would also accept training by any other recognized organization
offering equivalent certification. MSHA requests information on any
other nationally recognized program for the certification of persons to
conduct audiometric tests.
MSHA also considered the ``qualifications of personnel''
requirements from U.S. Armed Forces codes and international standards.
The consensus was that the technician needed to be trained in
conducting audiometric testing.
Although the proposal would not require that the audiologist or
physician be present when the technician conducts the audiometric test,
MSHA would require that they directly supervise the technician to
ensure strict adherence to testing procedures and measurement
parameters.
Baseline Audiogram
Section 62.140(b) of MSHA's proposal would require that, within six
months of a miner's enrollment in an HCP, the miner shall be offered a
valid baseline audiogram of the miner's hearing acuity against which
subsequent annual audiograms can be compared. This would include miners
with temporary layoffs, such as those miners employed at seasonal
operations. However, the proposal would allow up to 12 months
[[Page 66433]]
to obtain a baseline audiogram when a mobile test van is used.
Under existing standards for coal mines, MSHA does not specifically
address a time frame for offering a baseline audiogram for those miners
under a hearing conservation plan. MSHA has no requirements for
baseline audiograms in its current metal and nonmetal noise regulation.
This proposal is consistent with OSHA's noise regulation.
The proposal would allow mine operators to use existing audiograms
as the baseline, provided that they meet the testing requirements of
this part. OSHA also accepts existing audiograms as a baseline because,
in most cases, accepting old baseline audiograms is more protective for
the employee. OSHA reasoned that:
* * * old baselines will allow the true extent of the hearing
loss over the years to be evaluated. Obtaining a new baseline
audiogram after many years of noise exposure might be less
protective since the new audiogram might show higher thresholds and
the true extent of future losses would appear smaller than when
compared with the original baseline.
All commenters, addressing the issue of audiograms recognized the
need to establish a baseline. The commenters varied, however, on the
time needed to establish this baseline, i.e., from 30 days up to one
year from the first exposure to noise. One stated that ``* * * the
first annual or periodic audiogram should be allowed to be considered
as the baseline or pre-employment audiogram.'' Most of the commenters,
who specified a time frame for completing the baseline audiogram,
agreed with OSHA's position of allowing up to six months. Only one
comment was received, on the 1-year time allowed, for audiometric
testing with mobile test vans. This commenter was concerned that miners
might be exposed to noise, in the interim period, until the test van
was available and recommended ``that the employees utilize hearing
protection from the time they are enrolled in an HCP.''
NIOSH (1995) recommended that the baseline audiogram be conducted
within 30 days of enrollment in an HCP, even if a mobile test van is
used. NIOSH believes it is unacceptable to wait up to six months for a
baseline audiogram, because exposure to high sound levels for a
relatively short period of time can adversely affect the hearing acuity
of susceptible individuals.
MSHA has also taken into consideration requirements of the U.S.
Armed Forces and the international community with respect to baseline
audiograms. Many in the international community and the U.S. armed
services agree that the baseline audiogram is of primary importance.
MSHA has determined that the baseline audiogram is essential,
because it is the reference against which subsequent audiograms are to
be compared. The comparison will be used to determine the extent of
hearing loss. If the baseline audiometric test is not conducted
properly, it will not reflect the miner's true hearing thresholds and
any changes between baseline and subsequent tests may be masked.
Further, existing audiograms may be used as the baseline, if they meet
the testing requirements of this part. The use of pre-existing
audiograms would be more protective for the affected miner and less
burdensome on the mine operator.
Because of the baseline audiogram's importance, it is critical to
obtain one before exposure to hazardous noise. If this is not possible,
then the baseline is to be obtained as soon as is reasonably possible.
Due to remote locations and intermittent operations of many mines, MSHA
determined that allowing six months (or 12 months if a mobile test van
is used) for obtaining the baseline audiogram was reasonable. The 12
month period would allow mine operators to schedule many baseline and
annual audiograms simultaneously, and thus, substantially reduce the
cost when mobile test vans are used.
It should be noted that the provisions of Sec. 62.120 of MSHA's
proposal would require mine operators to ensure that all miners
enrolled in a hearing conservation program be provided hearing
protectors until they receive a baseline audiogram; and require the
operator to ensure the protection is used if the need to wait for a
mobile test van delays the initial audiogram past 6 months.
MSHA solicits additional comments on the appropriate time frame for
obtaining audiograms, especially in remote mining areas.
14-hour Quiet Period
Section 62.140(b)(2) of the proposal would require that the mine
operator ensure that the affected miner is not exposed to workplace
noise for at least a 14-hour period immediately prior to receiving the
baseline audiogram.
MSHA has no existing requirement in this area. The proposal is
similar to OSHA's noise standard except that, as discussed below, OSHA
permits the use of hearing protectors in lieu of removal from workplace
noise.
The 14-hour quiet period is intended to provide a miner's hearing
with sufficient rest to allow recovery from any temporary threshold
shift (TTS) caused by pre-test noise exposure. If the baseline
audiogram is skewed by TTS, subsequent comparisons to annual audiograms
would not provide accurate indications of the extent of damage incurred
during the time span between the baseline and subsequent tests.
There were numerous comments concerning the time frame for a quiet
period. Of these, most suggested that the 14 hours mandated in OSHA's
noise standard was sufficient to minimize any TTS. Others recommended
different time frames for the quiet period. One stated that ``* * *
there are sufficient human data in the literature to establish that a
14-hour quiet period is too short.'' Several commented that:
A suitable quiet period of 24 hours prior to the performance of
audiometric testing would be preferred. However, a 16-hour quiet
period would often meet the needs of most operations, being the
amount of time normally between the end of one days work and
starting time for the next.
One thought that eight hours was enough. Another commented that a quiet
period should be allowed but not required for the initial test.
Further, this commenter stated that 24 hours should be required for
confirmation testing.
Fodor and Oleinick (1986) in their paper on workers' compensation
reported that one researcher found full recovery from ``physiological
fatigue'' in 16 hours, with recovery from ``pathological fatigue''
taking longer. This researcher reported that the initial recovery seems
to be a logarithmic function of time and the longer recovery period is
a linear function. Most researchers, however, report complete recovery
from TTS taking no longer than 16 hours provided the TTS did not exceed
40 dB. On the other hand, some states require that a worker be away
from noise exposure for six months before evaluating hearing loss for
workers' compensation purposes.
MSHA concludes, after reviewing the scientific literature and the
standards of various jurisdictions, that the length of time required to
obtain full recovery from TTS depends upon the magnitude of the sound
pressure level, the length of exposure, the frequencies affected, the
person's age, and the person's susceptibility to hearing damage.
Because the mine operator has no control over the non-occupational
noise exposure of a miner, MSHA decided against limiting non-
occupational noise to a specified sound level during the quiet period;
however, as noted below, MSHA is requiring that the mine operator
notify employees of the need to avoid high levels of noise during the
14-hour period preceding the test, which it
[[Page 66434]]
hopes will limit non-occupational noise exposure. With the exception of
the EEC (15 minute quiet period), the consensus of the international
community and the U.S. armed services is that there should be a quiet
period of at least 14 hours. MSHA decided that a 14-hour quiet period
would be the most appropriate alternative and is consistent with OSHA's
requirements, comments to the ANPRM, and its review of available
literature. A quiet period longer than 14 hours could place an undue
burden on mine operators as the miner may have to stay away from work
to comply with the quiet period if the miner works a slightly extended
shift; many work shifts exceed 8 hours especially when a lunch period
is taken into account.
Use of Hearing Protectors for 14-hour Quiet Periods
Section 62.140(b)(2) of the proposed standard would also prohibit
the use of hearing protectors as a substitute for the 14-hour quiet
period. As noted previously, OSHA currently does allow hearing
protectors to be used during the required 14-hour quiet period.
When it first promulgated its Hearing Conservation Amendment in
1981, OSHA did not permit the substitution of hearing protectors for
the 14-hour quiet period. This decision generated much discussion among
commenters believing that it was unnecessarily restrictive. Even
professional audiologists strongly disagreed on this issue. One
commenter suggested that if the hearing protector reduced the level of
sound energy reaching the ear to 80 dBA or less, this would effectively
reduce the amount of baseline contamination to less than the usual
amount of audiometric measurement error. Commenters also cited problems
such as additional overtime wages, disruptions of work schedules, and
non-occupational noise exposure.
In 1983, OSHA revised its Hearing Conservation Amendment to allow
the use of hearing protectors as an alternative for the 14-hour quiet
period prior to the baseline audiogram. OSHA concurred with the large
number of commenters who testified that the use of hearing protectors
may provide sufficient attenuation to prevent noise-induced TTS from
contaminating baseline audiograms.
MSHA received many comments addressing this issue. Several of these
stated that hearing protectors should not be substituted for the quiet
period. Their general consensus can be summarized by one commenter who
stated that:
* * * the use of HPDs cannot be relied upon to reduce the noise
in all cases to a level suitable to be considered quiet for the
purpose of establishing baseline audiograms, especially if
individual variations in susceptibility to noise induced hearing
loss are considered.
Other commenters believed that the use of hearing protectors should be
allowed because they prevent TTS. One such commenter wanted a
qualification stating that:
* * * in many instances it may simply not be practical or
possible to test everyone for their baselines as they come to the
workshift, and thus reliance on HPDs for the 14-hr. noise-free
period is required. Thus MSHA should allow use of HPDs in lieu of
the 14 hrs., but with the following stipulation:
* * * no more than five days prior to the test, 1) the employees
whose hearing is to be evaluated receive refresher training in the
use of their protectors, and 2) the condition of the hearing
protector(s) the employee is to wear is checked and found
satisfactory. Any employee whose TWA exceeds 100 dBA shall be
required to wear an earplug together with an earmuff * * *
Some researchers, Shaw (1985) and Suter (1983), contend that sound
levels must be below 72 dBA to be considered ``effective quiet.''
Schwetz et al. (1980) found that a sound level below 85 dBA is needed
for recovery of TTS. Individuals with TTS recovered their normal
hearing quicker when exposed to 75 dBA sound level rather than 85 dBA.
The NIOSH Criteria Document (1972) recommends a sound pressure level of
65 dB as ``effective quiet'' based on work by Schmidek et al (1972).
Hodge and Price (1978) concluded that the level would have to fall
below 60 dBA to be effective quiet and not contribute to the
development of a TTS.
MSHA's proposal differs from OSHA's standard, in that it would not
allow hearing protectors to be substituted for the 14-hour quiet period
prior to the baseline audiogram. Although MSHA recognizes that its
decision may pose some scheduling problems for mine operators, it
should be emphasized that the quiet period is required only for the
baseline audiogram. Mine operators, however, may choose to employ it
for the annual audiograms.
MSHA has determined that the problems associated with the use of
individual hearing protectors are too great to guarantee an accurate
baseline measurement. Data indicate that in order to provide effective
quiet, the sound levels encountered during the quiet period would need
to be below 80 dBA. MSHA is particularly concerned with the ability of
hearing protectors to attenuate noise to such low levels in order to
prevent contamination of the baseline. Even at 80 dBA, some researchers
concluded that this level may be inadequate for the most susceptible
individuals. Moreover, the typical sound levels in mining are higher
than those experienced in general industry; therefore, hearing
protectors would need to attenuate the noise to a greater degree.
Although MSHA contends that hearing protectors can provide some
protection to miners whose exposures do not exceed the PEL, MSHA has
concluded that engineering and administrative controls provide much
more effective protection. MSHA's concerns with the ability of hearing
protectors to provide adequate attenuation are addressed in connection
with the requirements of proposed Sec. 62.120(b), under the heading of
Hearing protector effectiveness.
Notification to Avoid High Sound Levels
Section 62.140(b)(3) of the proposal would require mine operators
to notify miners to avoid high levels of non-occupational noise during
the 14-hour period before taking the baseline audiogram. This
requirement is the same as OSHA's noise standard.
In the 1983 preamble to its Hearing Conservation Amendment (48 FR
9757), OSHA emphasizes that, even if workers received this information
in training classes, such notification would aid memory and, thus,
provide additional support to the goal of obtaining a valid baseline
audiogram. OSHA concludes its discussion of this issue as follows:
Although employers are not responsible for employee noise
exposures sustained away from the workplace, the likelihood of non-
occupational noise exposure contaminating the baseline audiogram can
be substantially reduced by counseling workers of the need to avoid
such exposures in the period before their baseline test. Therefore,
this requirement is necessary and appropriate for the implementation
of a successful hearing conservation program.
Only a few commenters offered an opinion on this specific issue in
response to MSHA's ANPRM. These commenters agreed that workers need to
be advised to avoid non-occupational noise exposure prior to taking the
baseline audiogram.
MSHA believes that it is appropriate for operators to notify miners
of the importance of avoiding high noise areas in order to obtain valid
baseline audiograms. The proposed requirement is consistent with OSHA's
noise standard and the limited commenter responses.
Annual Audiogram
Section 62.140(c) of MSHA's proposal requires that, after
establishing a baseline, the miner to be offered a new
[[Page 66435]]
audiogram once every 12 months as long as the miner remains in the HCP.
Existing MSHA standards require coal mine operators to submit a
hearing conservation plan, which includes conducting periodic
audiograms, for each miner exposed to noise in excess of the PEL.
Because the use of hearing protectors is considered to provide
compliance with the PEL in this industry, few receive audiograms.
Moreover, there are no standards requiring audiograms for metal and
nonmetal workers.
OSHA requires, after the baseline audiogram has been obtained, an
annual audiogram for each employee exposed at or above its action level
to identify changes in hearing acuity, so that the use of hearing
protectors can be prescribed or other follow-up measures initiated
before hearing loss progresses. The preamble to OSHA's hearing
conservation amendment (46 FR 4143) states:
OSHA has chosen to retain the annual audiometric test
requirement because of the potential seriousness of the hearing
damage that can occur within a 2-year period. For employees exposed
to high levels of noise, a 2-year period between audiograms might
allow too much hearing loss to occur before identifying the loss and
taking remedial steps.
In response to its ANPRM, MSHA received numerous comments that
specifically addressed periodic audiograms. Many of these supported
annual testing and a few recommended a different time period. These
latter commenters suggested the following alternative time periods:
once or twice a year, depending on the intensity of the exposure; every
other year; and based upon need.
MSHA concludes that the determination of an STS in the one-year
period between required audiograms is meaningful for detecting the type
of problems for which HCP enrollment is the purpose. Detection of an
STS triggers several important actions under the proposal. Retraining
of the miner would be required. If the miner is enrolled in the HCP as
a result of noise exposure above the action level, but the miner's
noise exposure is below the PEL, detection of an STS would require the
provision of a hearing protector--which a miner at that exposure level
would otherwise not be required to utilize. If the miner was already
using a hearing protector, it would have to be replaced. Detection of
an STS would also require reevaluation of the engineering and
administrative controls being used. Waiting two years or more between
periodic audiograms could allow excessive hearing damage to miners.
MSHA also recognizes that some miners may be more susceptible to
hearing damage from noise exposure, and a few may be exposed to high
sound levels, such that annual audiometric testing may not be frequent
enough to prevent an STS.
In light of the comments to MSHA's ANPRM, the Agency's review of
the literature and pertinent governmental regulations, and OSHA's
existing requirements, MSHA has tentatively concluded that annual
audiometric testing is both necessary and appropriate. Annual
audiometric testing is an integral part of a comprehensive HCP.
Supplemental Baseline
Section 62.140(d) of MSHA's proposal would require the mine
operator to establish a ``supplemental audiogram'' when: (1) the STS
revealed by the annual audiogram is persistent, or (2) the hearing
threshold shown in the annual audiogram indicates significant
improvement over the baseline audiogram.
These proposed requirements are similar to those in OSHA's noise
standard except for the terminology.
In response to its ANPRM, MSHA received numerous comments on
circumstances in which it was not appropriate to use the original
baseline audiogram. Many commenters were in favor of revising the
baseline if an STS was persistent. One stressed the need for clear
guidelines for baseline revision to avoid the use of a variety of
creative methods which could result in different STS totals. Other
commenters were in favor of revising the baseline if the annual
audiogram showed an improvement in hearing. Another recommended
revising the baseline only if the improvement was consistent for at
least two or three consecutive tests. A final commenter wanted the
baseline revised only if there was a testing error.
MSHA believes, after reviewing these comments and standards of the
U.S. Armed Forces, that revising the baseline after an STS has been
identified would prevent this same STS from being identified
repeatedly. The annual audiogram on which the STS is identified would
then become the ``supplemental baseline audiogram.'' This supplemental
baseline would be used for comparison with future annual audiograms to
identify a second STS. The ``baseline audiogram'' would continue to be
used to quantify the total hearing loss in determining whether the loss
constitutes a ``reportable hearing loss''. To avoid confusion in the
mining industry, MSHA is proposing the term ``supplemental baseline''
rather than the term ``revised baseline'' used under OSHA. Since all
audiograms are to be retained as part of the audiometric test record
(see Sec. 62.150(c)), supplementation of the baseline audiogram would
not permit the destruction of the original baseline audiogram.
MSHA would also require supplementation of the baseline if the
annual audiogram shows significant improvement in hearing level because
this would more closely resemble the miner's actual hearing acuity
prior to being exposed to occupational noise. In this case,
supplementation of the baseline would be more protective because it
would allow more accurate evaluation of the true extent of future
hearing loss. Therefore, when a baseline is revised due to an
improvement of hearing acuity, this supplemental baseline would be
considered as the original baseline for determining when an STS occurs
and for quantifying the total hearing loss for reportablility under
part 50. The latter is reflected in the definition of reportable
hearing loss.
Section 62.150 Audiometric Test Procedures
MSHA proposes not to include specific procedural requirements for
conducting audiometric tests, calibrating audiometers, and qualifying
audiometric test rooms. Instead, MSHA proposes a performance-oriented
requirement that audiometric testing be conducted in accordance with
scientifically validated procedures. MSHA would specify the test
frequencies, but would allow the physician or the audiologist to use
professional judgment in choosing the appropriate testing procedure(s)
and require certification of the scientific validity of the procedures.
While this approach may require somewhat more in the way of
paperwork requirements, MSHA believes this is far preferable to the
alternative of a detailed specification standard, which could stifle
technology and impede improvements in methodology.
The proposal would also specify what records must be maintained,
and for how long, at the mine site. The proposed items included in the
audiometric test record--name, job classification, audiograms and
certifications as to the procedures used to take them, any exposure
determinations, and the results of any follow-up examinations--would
provide information essential for evaluating a miner's audiogram, among
other purposes.
[[Page 66436]]
The records are to be retained for at least six months beyond the
duration of the miner's employment. The six month retention period at
the mine site would assure that the audiometric test records of miners
who have short periods of unemployment are not destroyed and are
available for use by the mine operator to conduct further evaluations
upon the miner's return. In practice, MSHA believes that many mine
operators will keep miner's audiograms long after the miner's
employment ceases, for use if the miner should file a subsequent
workers' compensation claim for hearing loss.
Currently MSHA's metal and nonmetal noise standards do not contain
audiometric testing provisions. While Coal's noise standard requires
audiometric testing, it does not specify how it is to be conducted.
MSHA's proposal differs from OSHA's noise standard which contains
detailed procedures in 29 CFR Sec. 1910.95(h) and the associated
Appendices C, D, and E.
Several commenters generally supported MSHA's adoption of
audiometric testing requirements that are the same as OSHA's. A number
of commenters made specific recommendations regarding various aspects
of conducting audiograms including audiometric test instruments,
calibration procedures, and audiometric test rooms. Since MSHA has
decided not to specify audiometric test requirements in the proposed
rule, a discussion of the comments on specific procedures is not
included (except in the section which follows, Test procedures).
ANSI has several standards which impact the audiometric test
procedure. ANSI S3.21-1978 ``Methods for Manual Pure-Tone Threshold
Audiometry'' provides detailed procedures for conducting audiometric
tests. ANSI S3.1-1991 ``Criteria for Maximum Ambient Noise Levels for
Audiometric Test Rooms'' provides a criteria for the maximum background
sound pressure levels neccessary in order to obtain a valid audiogram.
ANSI S3.6-1996 ``Specifications for Audiommeters'' provides design
criteria for various classes of audiometers.
After reviewing comments, the scientific literature and several
governmental standards, MSHA chose not to include detailed, highly
technical procedures and criteria for conducting audiometric testing in
the proposal. Instead MSHA chose a performance-oriented approach by
proposing to require that audiometric testing procedures be governed by
scientifically validated methods. Because the person responsible for
conducting the tests is a physician, audiologist, or qualified
technician, he/she should be familiar with scientifically validated
procedures. MSHA would allow the physician or the audiologist to use
professional judgement in choosing the appropriate testing
procedure(s).
Moreover, audiometer manufacturers provide recommendations on
audiometer use and calibration (both laboratory and field). Because the
manufacturers are aware of the intricacies of their instruments, they
would be the most qualified to issue recommendations on the use and
calibration of their audiometers. By following manufacturer's
recommendations accurate audiometric testing is assured without MSHA
mandating detailed calibration specifications.
By not specifying a single test procedure, MSHA would permit the
use of any scientifically validated procedure. If a new, possibly more
accurate procedure would be validated, the medical professional could
readily adopt its use. If, however, current procedures were adopted in
the rule, an amendment would be needed to permit the use of any new
procedure.
Even though MSHA found no single comprehensive criteria for
audiometric testing, save OSHA's, there are criteria which deal with
various aspects of testing. For example, ANSI has standards on
background sound pressure levels for audiometric testing, methods for
pure tone audiometry, and for specifications for audiometers. MSHA
expects that most audiograms would be conducted using OSHA's
requirements, since many physicians and audiologists are familiar with
those regulations. Further, many texts and CAOHC training courses
discuss OSHA's audiometric testing procedures and criteria. Although
MSHA has not proposed detailed specifications in its standard, the
Agency contemplates publication of nonmandatory guidelines describing
what it believes to be the latest scientific procedures for conducting
audiometric tests.
MSHA, realizing that performance-oriented standards for audiometric
testing may be controversial, solicits comments on this approach, and
continues to solicit comments on the audiometric test procedures,
permissible background sound pressure levels, and calibration
requirements for audiometers.
Test Frequencies
The proposal would require that audiometric tests be pure tone, air
conduction, hearing threshold examinations, with test frequencies at
500, 1000, 2000, 3000, 4000, and 6000 Hz. The proposal also specifies
that these examinations be taken separately for each ear at the given
test frequencies. In response to MSHA's ANPRM, no commenters
specifically addressed audiometric test frequencies. Several, however,
generally supported MSHA's adoption of audiometric testing requirements
that are the same as OSHA's. MSHA's proposal would be consistent with
OSHA's requirements with respect to testing frequencies, as well as
consistent with the NIOSH criteria document (1972).
Although none of the commenters directly addressed audiometric test
procedures, several stated that MSHA should adopt or follow the OSHA
Hearing Conservation Amendment.
As noted in part II of this preamble, noise-induced hearing loss is
a permanent sensorineural condition that cannot be improved medically.
It is characterized by a declining sensitivity to high frequency
sounds. This loss usually appears first and is most severe at the 4000
Hz frequency. The ``4000 Hz notch'' in the audiogram is typical of
NIHL. Continued exposure causes the loss to include other audiometric
test frequencies, with 500 Hz being the least affected. While 500,
1000, and 6000 Hz are not included in the definition of STS, MSHA, like
OSHA, believes that these test frequencies contribute to a more
complete audiometric profile and are helpful in assessing the validity
of the audiogram as a whole. Furthermore, the inclusion of 500 and 1000
Hz makes it easier for an audiologist or physician to differentiate
conductive hearing loss from NIHL, and the inclusion of 6000 Hz would
better differentiate between presbycusis and NIHL.
Certification
Section 62.150(b) of MSHA's proposal would require that mine
operators obtain a certification, from whomever conducts audiometric
tests under this part, that such tests were conducted according to a
scientifically validated procedure.
OSHA's current noise standard does not require such certification.
OSHA has specific audiological test procedures, allowable background
sound pressure levels in audiometric test rooms, and audiometer
calibration requirements. MSHA's metal and nonmetal noise standards do
not contain audiometric testing provisions. While Coal's noise standard
requires audiometric testing, it does not specify how it is to be
conducted.
MSHA did not address this issue of certification in its ANPRM and,
therefore, no comments were received.
[[Page 66437]]
MSHA's proposal would relieve the mine operator from specifying the
audiological test procedure and criteria. The mine operator would rely
on the professional judgement of the physician or audiologist to select
the appropriate tests and criteria. Certification would not be accepted
from a qualified technician; pursuant to the proposed provisions in
Sec. 62.140, qualified technicians are to perform their work under the
supervision of a physician or audiologist. MSHA believes that it is
necessary for the physician or audiologist to certify that the
audiological tests were conducted in accordance with a scientifically
validated procedure. In most cases, the mine operator does not have
sufficient medical knowledge to determine if the tests were properly
conducted and must rely on the judgement of a physician or audiologist.
The certification will stand as evidence that the audiological tests
were conducted in accordance with the requirements for a scientifically
validated procedure.
Audiometric Test Recordkeeping and Retention
Section 62.150(c) of MSHA's proposal would require that mine
operators maintain a record of each required audiometric test. This
record would contain--
(1) the name and job classification of the miner tested
(2) a copy of the miner's audiogram(s) (original baseline, annual,
and supplemental baseline);
(3) certification(s) that the tests were conducted using
scientifically validated procedures;
(4) any exposure determination for the miner; and
(5) the results of any follow-up examination(s).
This information would not have to be written on the actual
audiogram as long as it was kept with the audiogram. The audiometric
test records would be required to be maintained at the mine site for
the duration of the affected miner's employment plus at least six
months.
Although not defined in this proposal, by the term ``duration of
employment'' MSHA means the period of time between the date of a
miner's initial hiring and the date on which the miner is released,
quits, retires, or dies. There must be a lapse of at least six months
beyond formal termination of employment before a mine operator could
destroy the audiometric test records. Moreover, it is MSHA's intent
that a layoff, strike, lockout, furlough, period of leave (both paid
and unpaid), or other temporary break in service would not be
considered as a formal termination of employment, even if it exceeds
six months.
MSHA's existing standards have no requirements in this area. OSHA's
noise standard requires that employers maintain a record of the
audiometric test results and maintain these records for the duration of
employment.
Since the publication of the noise standard, OSHA promulgated 29
CFR 1910.20 Access to employee medical records. This standard applies
to all medical records required to be kept pursuant to OSHA standards--
noise records are treated in the same way as carcinogen records. Under
1910.20, OSHA requires that medical records for each employee be
maintained for at least the duration of employment plus (30) years,
with the exception of employees who have worked for less than (1) year
for the employer. The medical records for these employees need not be
retained beyond the term of employment if they are provided to the
employee upon termination. Further this standard requires that exposure
records be maintained for at least 30 years.
Additionally, OSHA's noise standard requires that the audiometric
test record include--
(1) name and job classification of the employees;
(2) date of the audiogram;
(3) examiner's name;
(4) date of the last acoustic or exhaustive calibration of the
audiometer; and
(5) employee's most recent noise exposure assessment.
Additionally, employers are required to maintain an accurate record
of background sound pressure levels in audiometric test rooms. OSHA's
noise standard has no requirement to maintain these records at the
employer's work site.
MSHA received a number of comments specifically addressing time
frames for maintaining audiometric test records. One commenter
recommended that they be maintained for 30 years. Two commenters
recommended that such records be retained for the duration of the
miner's employment plus 30 years. Most of the commenters on this issue
recommended that MSHA require that audiometric test results be kept for
the duration of employment.
MSHA also reviewed the audiometric test recordkeeping and retention
requirements from the U.S. Armed Forces and various other countries.
Generally, the audiometric test record is to be maintained for at least
the duration of employment.
MSHA considered allowing mine operators to keep the audiometric
test record at a location other than the mine site. The Agency
concluded, however, that this alternative was impractical because it
could delay MSHA's access to such records. Furthermore, it would be
burdensome for mine operators to copy and mail the records or send a
fax of these records to the Agency.
MSHA believes that this record should be retained for at least six
months beyond the duration of the miner's employment. The risk of harm
stops with the cessation of employment; keeping the records an
additional 6 months would assure that a miner's audiometric test
records are not destroyed and are available for use by the mine
operator to conduct further evaluations should a miner return within
that time period. In practice, MSHA believes that many mine operators
will keep miner's audiograms long after the miner's employment ceases,
for use if the miner should file a subsequent workers' compensation
claim for hearing loss. In some states, the worker has many years
following employment to file such a claim.
The proposed items included in the audiometric test record would
provide essential information to MSHA and to the health professional
for evaluating a miner's audiogram. The information is also necessary
for identifying the audiograms, evaluating whether the audiometric
tests have been conducted properly, and for determining whether the
results are valid. Further, the information is critical for the
evaluator in determining whether an identified hearing loss was not
work related or aggravated by occupational noise exposure.
Section 62.160 Evaluation of Audiograms
MSHA's proposal would require that the mine operator inform the
person evaluating the audiogram of the requirements of this part and
provide them with copies of the miner's audiometric test records. The
mine operator would be responsible for having a physician, audiologist,
or qualified technician determine if an audiogram is valid and if a
standard threshold shift (STS) or reportable hearing loss has
occurred--in which case certain actions are required pursuant to
Sec. 62.180 and Sec. 62.190. Time frames and privacy protection are
part of the proposal, as is a requirement for a prompt retest if an
audiogram is invalid.
STS is defined in this proposal, as in OSHA's standard, as a change
in a worker's hearing acuity for the worse,
[[Page 66438]]
relative to that worker's baseline audiogram, of an average of 10 dB or
more at 2000, 3000, and 4000 Hz in either ear. If the STS is determined
to be permanent, a supplemental baseline is established pursuant to
Sec. 62.140 and this becomes the baseline for determining any future
STS. This definition is sufficiently restrictive to locate meaningful
shifts in hearing, yet not so stringent as to create unnecessary
follow-up procedures; the averaging of hearing levels at adjacent
frequencies will reduce the effect of testing errors at single
frequencies.
The proposal would permit but not require mine operators to adjust
audiometric test results by applying a correction for presbycusis
before determining whether an STS or reportable hearing loss has
occurred, and it includes tables for this purpose. Presbycusis is the
progressive loss of hearing acuity associated with the aging process.
The proposed adjustment for presbycusis is optional; however, if a mine
operator uses this approach, it must be applied uniformly to both the
baseline and annual audiograms in accordance with the procedures and
values listed in the proposed standard. Although this is the position
taken in the proposal, MSHA notes that the latest NIOSH advice on this
topic has advised against the use of presbycusis correction factors.
Moreover, the Agency is concerned about locking-in specific presbycusis
adjustment tables. MSHA, therefore, requests additional comments on
whether to use presbycusis corrections for audiograms and, if so, how
to provide for such adjustment in a regulatory context.
MSHA's existing noise standards do not address the evaluation of
audiograms. MSHA's proposed requirements would be similar to those in
OSHA's noise standard; the few differences are noted below.
Information Provided to Reviewer
Section 62.160(a)(1) of MSHA's proposal would require that the mine
operator inform the person evaluating the audiogram of the requirements
of this part and provide the evaluator with copies of the miner's
audiometric test records. OSHA requires employers to provide the
persons evaluating audiograms with a copy of the requirements of its
standard, copies of the employee's baseline and most recent audiometric
test records, background sound pressure levels in the audiometric test
room, and a record of audiometer calibration.
In its ANPRM, MSHA did not address what information the mine
operator should provide to the person evaluating audiograms. The
commenters, therefore, did not address this issue specifically. In
discussing related topics, some commenters recommended that MSHA adopt
OSHA's requirements on this issue.
Recently, research has implicated exposure to chemicals as
aggravating hearing loss, Fetcher (1995), Morata (1989, 1993, 1995).
MSHA requests comments as to how to address various aspects of this
possible relationship. For example, could exposure to chemicals cause
an invalid audiogram? What information should reviewers have about
chemical exposure? Any research results on this topic would be welcome.
MSHA believes that providing certain information is necessary for
physicians and audiologists to evaluate the accuracy and validity of
miners' audiograms. For example, the evaluator would need to know the
procedure for determining an STS, the criteria for retest or medical
follow-up, presbycusis correction procedures, and recordkeeping
requirements.
Review of audiogram. Under Sec. 62.160(a)(2) of this proposal, the
mine operator would be responsible for having a physician, audiologist,
or qualified technician determine if an audiogram is valid and if an
STS or reportable hearing loss has occurred. MSHA's proposal is
consistent with the present OSHA noise standard.
Of the many commenters on this specific issue, most believed that
professional review was necessary. One of these said that ``MSHA should
require an audiologist or physician to evaluate audiograms that show
standard threshold shifts [STS] or other unusual changes''.
A few commenters felt that professional review was unnecessary.
These commenters indicated that the person conducting the audiogram
could inform the employee of the results, and explain the significance
of these results, so that the employee could make any decisions
regarding further testing or evaluation.
The U.S. Armed Services and the international community vary on the
medical expertise required to review audiograms.
MSHA believes that audiograms need to be reviewed for validity; as
noted below, if audiograms are not valid, the proposal would require a
retest. Examples of questionable audiograms are audiograms that show:
large unilateral differences in hearing thresholds between the two
ears; unusual frequency patterns that are not typical of NIHL;
thresholds that are not repeatable; or an unusually large hearing loss
over a yearly period. MSHA maintains that the review of audiograms is
an integral part of an audiometric testing program.
Qualifications for Audiogram Reviewers
Under Sec. 62.160(a)(2) of this proposal, a mine operator would be
required to have a physician, audiologist or a qualified technician who
would be under the supervision of a physician or audiologist evaluate
audiograms to determine their validity and whether an STS or reportable
hearing loss has occurred. The qualifications of these individuals to
conduct this evaluation are discussed under Sec. 62.140 Qualifications
of personnel along with the comments received on this issue.
Standard Threshold Shift (STS)
This proposal would require the evaluator to determine whether a
miner has incurred an STS in his/her hearing. STS is defined in this
proposal as a change in a worker's hearing threshold relative to that
worker's baseline audiogram of an average of 10 dB or more at 2000,
3000, and 4000 Hz in either ear. This requires that hearing loss be
calculated by subtracting the current hearing levels from those on the
baseline audiogram at 2000, 3000, and 4000 Hz; when the hearing losses
at each frequency are averaged (added up and divided by three); if the
average loss in either ear has reached 10 dB, it constitutes an STS. If
the STS is determined to be permanent, a supplemental baseline is
established pursuant to Sec. 62.140 and this becomes the baseline for
determining any future STS. The definitions of ``baseline audiogram'',
``supplemental baseline audiogram'', and ``standard threshold shift''
are discussed in detail in connection with proposed Sec. 62.110.
OSHA defines an STS in essentially the same way, requiring that
employees' annual audiograms be compared to their baseline audiogram to
determine if the annual audiogram is valid and if an STS has developed.
Of the numerous comments addressing the issue of STS in response to
MSHA's ANPRM, many endorsed OSHA's definition of STS. One commenter
stated that:
The Standard Threshold Shift (STS) concept is the basic
foundation of a hearing conservation program and is the best
indicator of early noise-induced hearing loss [NIHL]. It enables
those conducting the audiometric examinations to have the needed
``red flag'' to indicate when additional testing or evaluation is
needed. It also enables the effectiveness of the employer's hearing
conservation program to be evaluated and monitored. The criteria
must be sensitive enough to identify meaningful changes in hearing
but must not be so sensitive as to
[[Page 66439]]
pick up spurious shifts or ``false-positives.'' * * * Identifying a
standard threshold shift therefore means that the shift value must
be outside the range of audiometric error ( 5 dB) and
serious enough to warrant prompt attention.* * * The averaging of
shifts over adjacent frequencies minimizes normal test error, and
random errors will tend to cancel each other out. * * *
In considering the frequencies to be used, it is noted that 4000
Hz is generally considered to be affected by noise the earliest and
most severely. The 2000 and 3000 Hz frequencies are very important
in understanding speech and should also be included in the
definition of STS.
For the above-mentioned reasons, as well as simplifying the
process in facilities which have operations under both MSHA and OSHA
jurisdiction, we recommend MSHA adopt an average shift of 10 dB or
more at 2000, 3000, and 4000 Hz, relative to the baseline audiogram.
* * *
Of those commenters who did not endorse OSHA's STS criteria, one
stated that OSHA's STS definition was ``* * * not stringent enough and
the worker hearing loss has progressed too far with this shift to be a
reliable preventive measure.'' Another stated--
* * * the suggested criteria [OSHA's STS definition] provides no
benefit but additional testing, specialist costs, reporting,
administrative costs, and potential MSHA punitive fines. * * *
The STS concept is misguided. A significant percentage * * * of
people will have changes take place in their hearing which would
qualify as an STS without any exposure to occupational noise.
Royster (1992) proposes a definition of STS that is different from
OSHA's. In her definition, 15 dB of hearing loss (relative to the
baseline) must occur at any audiometric test frequency from 500 to 6000
Hz on two sequential audiograms, before the STS is established. The 15
dB of hearing loss which occurs on two sequential audiograms identifies
the largest number of true positives (permanent threshold shifts) and
the least number of false positives (temporary threshold shifts
mistakenly identified as permanent threshold shifts).
NIOSH (1995) recommends that the criteria for an STS be a 15 dB
decrease in hearing acuity at any one of the audiometric test
frequencies from 500 to 6000 Hz on two sequential audiograms. The shift
in hearing acuity must be in the same ear. The second audiogram would
be administered as soon as reasonable. NIOSH believes this criteria is
sufficiently stringent to detect beginning hearing loss, yet won't
include workers whose hearing acuity is simply showing normal
variability. If the 15 dB change is found, an immediate retest should
be conducted and followed by a confirmation test within 30 days. The
confirmation test should be preceded by 14 hours of quiet.
This draft criteria for STS differs from the criteria recommended
by NIOSH in their 1972 criteria document. NIOSH's previous criteria
defined STS as a change of 10 dB or more at 500, 1000, 2000 or 3000 Hz;
or 15 dB or more at 4000 or 6000 Hz.
There are some instances where large shifts in hearing level occur
at higher test frequencies (4000 and 6000 Hz) with little or no change
in hearing level at the middle frequencies. While large shifts are
uncommon, they may occur in noise-sensitive individuals, especially in
the early stages of NIHL. Correctly identifying significant threshold
shifts is particularly important for workers who have already begun to
lose their hearing. The proposed definition of STS would identify
individuals suffering shifts as large as 30 dB at 4000 Hz with no
shifts at the lower frequencies (30 plus 0 plus 0 divided by 3 equals
10, an STS). This permits the early identification of individuals at
risk, so that corrective measures could be taken.
MSHA's proposed definition of STS is sufficiently restrictive to
locate meaningful shifts in hearing, yet not so stringent as to create
unnecessary follow-up procedures. The averaging of hearing levels at
adjacent frequencies will reduce the effect of testing errors at single
frequencies. The occurrence of an STS is serious enough to warrant
prompt attention because it may be a precursor to material impairment
of hearing. It is important to note that MSHA does not equate STS with
material impairment caused by NIHL.
MSHA believes, after considering the relevant factors and reviewing
current U.S. military and international standards, that the proposed
definition of STS is the most appropriate and consistent with the
purposes of its hearing conservation standard. The proposed definition
of STS--
(1) is adequately supported in OSHA's record for its Hearing
Conservation Amendment;
(2) is the criteria recommended or accepted by most commenters to
MSHA's ANPRM;
(3) results in a high degree of accuracy in identifying workers for
follow-up;
(4) concentrates on those frequencies that are the earliest or the
most severely affected by noise; and
(5) is a recognized and relatively simple approach.
Because NIOSH revised its recommendation for the criteria of an
STS, MSHA requests comments on NIOSH's new criteria. Furthermore, any
data on the advisability of using either the MSHA proposed criteria of
STS or NIOSH's criteria of STS would be welcomed.
Reportable Hearing Loss
The proposal would require the evaluator to determine if there has
been a ``reportable hearing loss''. See the discussion of ``Reporting
noise-induced hearing loss (NIHL)'' under Sec. 62.190 Notification of
results.
Instruction to Medical Professional
Section 62.160(a)(3) of the proposal would require the mine
operator to instruct the physician or audiologist not to reveal to the
mine operator any specific findings or diagnoses unrelated to the
miner's exposure to noise or the wearing of hearing protectors without
the written consent of the miner. Currently, neither MSHA nor OSHA have
such a provision in their noise standards; OSHA does have such
provisions in air quality standards like benzene and lead.
The topic of instructions to medical professionals was not raised
in the ANPRM. Therefore, no comments on this issue were received.
MSHA believes that this requirement is necessary to safeguard the
privacy of individuals. The mine operator does not need to be informed
of medical conditions unrelated to occupational noise exposure. MSHA's
rationale is that if the mine operator had confidential medical
information, the mine operator could use it to justify an adverse
action against the miner.
30-Day Requirement
According to Sec. 62.160(a)(4) of MSHA's proposal, the mine
operator would have 30 days to obtain the audiometric results and the
interpretation of the results from the person evaluating the audiogram.
OSHA does not specify a time period for evaluating audiograms.
MSHA's ANPRM did not address the issue of time frame for evaluating
audiograms. A few commenters, however, expressed concern with the
length of time that some service providers take to report results to
the employer. One stated that:
Service providers have taken undue advantage of a perceived
`grace period' in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. * * * the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Notification of STS, including the optional retest of STS-
affected employees, should be completed within a 30-day period
following testing. OSHA's time limit of 21 days following
notification to the employer creates a loophole which makes the
employee wait all too long for feedback regarding STS.
[[Page 66440]]
The other commenter stated that:
In reality, from the time the hearing test is sent to an
audiologist or physician to review, it is reviewed, recommendations
made, it is returned to the plant personnel and the plant has 21
days to notify the employee, the total process often stretches into
a 45-60 day time frame.
MSHA believes that a 30-day limit to evaluate audiograms is
reasonable and necessary to prevent undue delays in the evaluation of
the audiogram and notification to the miner of the results. Under
proposed Sec. 62.190, a miner would have to be notified within 10
working days of audiogram results obtained by the mine operator, as
discussed in connection with that section; accordingly, the net result
of these provisions is a maximum delay of approximately 44 days from
the date of audiometric testing to the notification of the miner. If a
retest was conducted, which, as discussed below must be done within 30
days of receiving a determination that the original test was invalid,
this delay in notification could be as long as 104 days. If the miner's
employment ceases during this delay period, the mine operator would be
required to provide the miner with a copy of the audiometric test
records as required by Sec. 62.200(c), including the results of all
testing, as soon as the record is complete. MSHA welcomes comments on
this issue.
Audiometric Retest
Section 62.160(b)(1) of the proposal would require a mine operator
to conduct a retest, if the audiogram was judged to be invalid, within
30 calendar days of receiving this information--provided, however, that
the 30-day time frame is stayed until any medical pathology resulting
in the invalid audiogram has improved to the point that a valid
audiogram may be obtained. In addition, Sec. 62.160(b)(2) of the
proposal would allow a mine operator to obtain one retest within 30
days after an STS or reportable hearing loss is found, and to
substitute the retest audiogram for the annual audiogram. The latter
retest is not mandatory.
OSHA also permits a retest within 30 days to confirm an STS, but
does not specifically require a retest if the audiogram is judged to be
invalid.
Many commenters supported OSHA's retest provision as written, while
others supported it with qualifications. One commenter believed that a
60-day period was appropriate. Another believed that a 30-day
limitation to both retest and notify was appropriate because:
Service providers have taken undue advantage of a perceived
grace period in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. By the time audiometric tests are
administered, entered into a computer, returned to an employer, and
then finally returned to the employee, the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Other commenters stated different views. One commenter stated that:
* * * most programs involve the use of testing vans that cannot
easily make a return trip in 30 days because of scheduling limits.
It would also be extremely expensive to make a return trip to
confirm a single STS. If an employee is found to have a significant
hearing loss, he should be required to wear hearing protectors in
all noise environments of 85 dBA or greater. If the next scheduled
audiogram also shows the hearing loss, then the loss should be
considered confirmed.
Another commenter stated that:
* * * an employee with a change in hearing could be immediately
counseled, refitted [i.e., hearing protectors], educated, notified
and return to his job. This would be more cost-effective than
bringing him back prior to the shift to get a hearing test showing
there is no STS.
MSHA believes, after considering comments and reviewing U.S. armed
forces and international standards, that the retest provisions are
necessary to assure that valid audiograms are provided in a timely
fashion. The retest should be conducted within a reasonable time, and
30 days is believed to be adequate, with the caveat that this time
frame does not begin to run until any medical pathology causing a
validity problem has improved to the point that a valid audiogram can
be obtained. MSHA recognizes that in such cases it will not be possible
to wait for a mobile van; but MSHA believes that in the limited number
of cases where a retest is required, it is appropriate and necessary to
send the miner to the nearest available facility for such a test.
The provision to obtain an optional retest if an STS is detected is
desirable. This would permit the mine operator to substantiate that an
STS had occurred, thus confirming permanent hearing loss. By detecting
only permanent hearing loss, the mine operator would have better
information on which to base administrative, technical, and financial
decisions relative to retraining the miner, permitting the miner to
select a different or additional hearing protector, and reviewing the
effectiveness of the noise controls.
Use of Age Correction (Presbycusis Factors)
Section 62.160(c) of the proposal would permit mine operators to
adjust audiometric test results by applying a correction for
presbycusis before determining whether an STS or reportable hearing
loss has occurred. Presbycusis is the progressive loss of hearing
acuity associated with the aging process. This adjustment for
presbycusis is optional; however, if it is used, it must be applied
uniformly to both the baseline and annual audiograms in accordance with
the procedures and values listed in Sec. 62.160(c) (1) through (4).
OSHA's noise standard also permits the use of presbycusis
correction factors. MSHA's proposal would be essentially the same as
OSHA's Appendix F: Calculations and Application of Age Corrections to
Audiograms. Both MSHA's proposal and OSHA's Appendix F adopt the
procedures and age correction tables used by NIOSH in its criteria
document (1972).
Commenters to OSHA's Hearing Conservation Amendment (48 FR 9763)
suggested that the use of such presbycusis factors also would account
for those cases of NIHL that arise from causes other than occupational
noise exposure. In the preamble to its Hearing Conservation Amendment
(48 FR 9763), OSHA states that:
* * * these correction factors will aid in distinguishing between
occupationally induced and age-induced hearing loss. This is
particularly important because the pattern of hearing loss due to
aging closely resembles that of noise-induced hearing loss [NIHL]. *
* * Therefore, although * * * the use of a correction factor may
complicate calculation procedures and cause some errors, * * *
professional supervision of the hearing conservation program will
ensure that audiometric technicians understand how to use the age
correction chart * * *
Most commenters who addressed this issue in MSHA's ANPRM, contend
that the use of presbycusis correction factors is appropriate. Many of
these commenters supported MSHA's use of the same criteria as in OSHA's
Appendix F. Other commenters recommended age corrections different than
those used by OSHA. One commenter suggested that MSHA use the ISO
1999.2 (1989) standard. Another one suggested that, because the NIOSH
criteria is almost 20 years old, ``The criteria used should be the most
recent and [accepted] data.''
Several commenters believed that applying presbycusis factors would
reduce unnecessary recordkeeping and follow-up procedures. One stated
that:
Many audiometric computer programs used for processing data have
this correction calculation built in the software. To change to some
other criteria or to remove this factor will result in the
modification of numerous systems and a need to switch back and
forth,
[[Page 66441]]
depending on whether the operator is OSHA or MSHA regulated.
Another of these suggested that MSHA require the use of such correction
factors, rather than allow their use to be optional, because such
optional use could result in discrepancies in results among audiometric
testing services.
A few commenters suggested that it would be better not to adjust
audiometric test results for presbycusis. They maintained that the
place to claim credit for presbycusis is in determining workers'
compensation and not in the institution of an HCP. These commenters
believed that not everyone who ages loses their hearing to the same
degree, and that the use of presbycusis corrections might mask changes
for older adults who have previously had good hearing.
Finally, one commenter recommended that MSHA seek medical advice
from national sources to determine what the medical community
recognizes as changes occurring from aging.
In contrast to NIOSH's presentation of one set of presbycusis data,
the ISO Document ISO 1999:1990(E) (1990) gives a dual set of values for
the non-industrial noise exposed population. These data are offered in
two tables. One table represents a highly screened, otologically normal
population, i.e., persons in a normal state of health, free from all
signs and symptoms of ear disease and obstructing wax in the ear
canals, and having no history of undue exposure to noise. The second
table represents an unscreened population from an industrialized
country. The ISO states that the choice of using the screened or
unscreened data base depends on what question is to be answered. It
states:
For example, if the amount of compensation that could be due to
a population of noise-exposed workers is to be estimated, and
otological irregularities and non-occupational noise exposure are
not considered in compensation cases, unscreened populations will
form the more appropriate data bases.
The ISO further states, however, that its standard ``* * * is based on
statistical data and therefore shall not be used to predict or assess
the hearing impairment or hearing handicap of individual persons.'' The
ISO data would be more difficult to use than NIOSH data because its
interpretation would require a higher level of statistical and
mathematical expertise.
NIOSH (1995) now recommends that audiograms not be corrected for
presbycusis. NIOSH believes that it is inappropriate to apply
presbycusis correction factors from a population to an individual.
Furthermore, there are no data to confirm that a 50 year old in 1995
will incur the same hearing loss due to aging that a 50 year old did in
1970. If the worker's audiogram is to be corrected for presbycusis,
then the hearing loss of a non-occupational noise exposed group with
the same demographic characteristics as the worker should be used.
However, these kinds of data are not complete nor are they readily
available.
The following is an example of the use of presbycusis correction
factors as proposed in MSHA's noise standard--
(a) Determine from Tables 62-3 or 62-4 the age correction values
for the miner by--
(1) Finding the age at which the baseline audiogram (or
supplementary baseline audiogram if appropriate) was taken and
recording the corresponding values of age correction at 2000 Hz through
4000 Hz; and
(2) Finding the age at which the most recent audiogram was taken
and recording the corresponding values of age correction at 2000 Hz
through 4000 Hz.
(b) Subtract the value found in step (1) from the value found in
step (2). The differences calculated represent that portion of the
change in hearing that may be due to aging.
(c) Subtract the value found in step (b) from the hearing threshold
level found in the annual audiogram to obtain the adjusted annual
audiogram hearing threshold level.
(d) Subtract the hearing threshold in the baseline audiogram (or
supplemental baseline audiogram as appropriate) from the adjusted
annual audiogram hearing threshold level to obtain the age-corrected
threshold shift.
Example: A miner is a 32-year-old male. The audiometric history in
decibels is shown below for his right ear. A threshold shift of 10 dB
at 2000 and 3000 Hz and 20 dB at 4000 Hz exists between the audiograms
taken at ages 27 and 32. A retest audiogram has confirmed this shift.
------------------------------------------------------------------------
Audiometric test
frequency (Hz)
Miner's age -----------------------
2000 3000 4000
------------------------------------------------------------------------
26............................................. 5 5 10
*27............................................. 0 0 5
28............................................. 0 0 10
29............................................. 0 5 15
30............................................. 5 10 20
31............................................. 10 20 15
+32............................................. 10 10 25
------------------------------------------------------------------------
An asterisk (*) has been used to identify the supplemental baseline
audiogram and a plus (+) the most recent audiogram. The annual
audiogram taken at age 27 becomes a supplemental baseline audiogram
(and is used in calculating hearing loss) because it shows a
significant improvement over the baseline audiogram taken at age 26.
Steps (a) and (b). Find the age correction values (in dB) at age 27
and age 32 in Table 62-3. The difference, shown below, represents the
amount of hearing loss that may be attributed to aging in the time
period between the baseline audiogram and the most recent audiogram.
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Age 32.......................................... 5 7 10
Age 27.......................................... 4 6 7
Difference...................................... 1 1 3
------------------------------------------------------------------------
Step (c). Subtract the difference determined in step (b) from the
hearing levels in the most recent audiogram. In this example, the
adjusted hearing threshold levels are as follows:
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Age 32.......................................... 10 10 25
Correction...................................... 1 1 3
Adjusted........................................ 9 9 22
------------------------------------------------------------------------
Step (d). Subtract the hearing threshold level in the baseline
audiogram from the adjusted annual audiogram hearing threshold to
obtain the age-corrected threshold shift.
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Adjusted........................................ 9 9 22
Baseline........................................ 0 0 5
Shift........................................... 9 9 17
------------------------------------------------------------------------
The average threshold shift at 2000, 3000, and 4000 Hz without age
correction is (10+10+20)/3=13.3 dB. The average age-corrected threshold
shift at 2000, 3000, and 4000 Hz is (9+9+17)/3=11.7 dB. This shift is
an STS because it exceeds 10 dB, but it is not, as yet, a reportable
hearing loss (25 dB). Intervention at this point should prevent further
loss and subsequent impairment.
MSHA agrees that not all individuals are affected by presbycusis to
the same degree. Additionally, studies have
[[Page 66442]]
shown that individuals in environments free from noise exposure display
little evidence of presbycusis. MSHA is concerned that the use of
presbycusis corrections may allow some miners to incur excess work-
related hearing loss. For example, some miners may not have off-the-job
noise exposure and may not have a decrement in their hearing due to
aging at the levels specified in the presbycusis correction table.
Nevertheless, MSHA maintains that at this time, allowing the adjustment
of audiometric test results for presbycusis is both reasonable and
appropriate. In industrial audiometry, this correction is often used to
determine occupational NIHL by adjusting the measured hearing level to
compensate for the normal loss of hearing due to aging. This is
particularly important because the pattern of hearing loss due to aging
resembles that of NIHL. The use of age corrections will help the mine
operator judge how well the HCP is working. Such adjustments are
consistent with current scientific practice, OSHA's standard, and the
recommendations of the majority of the commenters to MSHA's ANPRM.
MSHA selected the NIOSH presbycusis data so that all mine operators
who correct audiograms for aging will be using the same data. Though
there may be slight variations at individual frequencies, the NIOSH
presbycusis values are similar to those of other well known presbycusis
data bases, such as the U.S. Public Health Service data, those used by
Robinson and Burns, and those of Passchier-Vermeer. The NIOSH data are
for a highly screened population which excluded individuals with any
significant noise exposure on-the-job, off-the-job, or during military
service. Using a single set of presbycusis values will standardize the
process of determining STS nationwide. If MSHA allowed mine operators
to select their own presbycusis values, there could be major
nonuniformity in determining STS's and reportable hearing losses.
Nevertheless, the Agency is concerned about locking-in particular
presbycusis adjustment tables, and requests additional comments on how
to provide for a presbycusis adjustment in a regulatory context.
In conclusion, MSHA believes that, at this time, scientific data
and the consensus of commenters support allowing the use of the
presbycusis correction factors presented in Tables 62-3 and 62-4.
Although this is the position taken in the proposal, MSHA notes that
the latest NIOSH advice on this topic has advised against the use of
presbycusis correction factors. MSHA, therefore, requests additional
comments on whether to use presbycusis corrections for audiograms.
Section 62.170 Follow-up Evaluation When Audiogram Invalid
This section of the proposal provides that when a valid audiogram
cannot be obtained due to a suspected medical pathology of the ear, and
the physician or audiologist evaluating the audiogram believes that the
problem was caused or aggravated by the miner's exposure to noise or
the wearing of hearing protectors, a miner must be referred for a
clinical audiological or otological evaluation as appropriate at mine
operator expense.
This section also provides that if the physician or audiologist
concludes that the suspected medical pathology of the ear which
prevents obtaining a valid audiogram is unrelated to the miner's
exposure to noise or the wearing of hearing protectors, the miner be
advised of the need for an otological evaluation; but in such cases, no
financial obligation would be imposed on mine operators.
Finally, this section would require the mine operator to instruct
the physician or audiologist not to reveal to the mine operator any
specific findings or diagnoses unrelated to the miner's exposure to
noise or the wearing of hearing protectors without the written consent
of the miner.
OSHA's noise standard has similar follow-up requirements, except
for the nondisclosure provision. MSHA's current noise standards have no
follow-up evaluation provisions.
In response to MSHA's ANPRM, many commenters supported OSHA's or
similar requirements for referring employees to a physician for a
medical follow-up. A few commenters, however, stated that ``MSHA need
not include criteria for directing miners for further medical follow-up
nor require a physician, audiologist, or other qualified medical
personnel to evaluate the audiograms.''
Another commenter stated the following regarding who should pay for
these follow-up evaluations:
* * * I have a standard recommendation when working with
companies that they pay for all initial medical evaluations in order
to determine disposition. I think it is as important to them to have
documentation that an employee has a medical problem just as [when]
he has an occupational one.
The decision as to which type of evaluation, clinical audiological
evaluation or otological, is appropriate will depend upon the
circumstances. Standards from the international community and the U.S.
Armed Forces vary to some degree regarding certain elements, such as
the extent of follow-up examinations. A clinical audiological
evaluation is generally more comprehensive, intensive, and accurate
than the routine audiometric testing conducted for HCP purposes. For
example, such testing may be warranted if an unusually large threshold
shift occurs in one year given relatively low noise exposures. An
otological evaluation, on the other hand, is a medical procedure
conducted by a physician specialist (e.g., otolaryngologist) to
identify a medical pathology of the ear. Audiometric testing can imply
the existence of such a medical pathology. For example, a hearing loss
in only one ear can indicate the existence of an acoustic neuroma (type
of tumor) at an early stage. Such discovery could be potentially life
saving. Another more common reason for an otological examination would
be for the removal of impacted ear wax (cerumen) which reduces hearing
acuity and can be aggravated by the use of insert-type hearing
protectors.
Making the determinations under this section would not require a
diagnosis by a physician specialist confirming a medical pathology. The
proposal is intended to allow the audiologist or physician authorized
to review the audiograms to make a determination as to whether a
follow-up examination is appropriate--and who pays for it. Accordingly,
the word ``suspected'' precedes the words ``medical pathology'' in this
section.
If the person evaluating the audiogram believes that the suspected
medical pathology is related to occupational noise exposure or to the
wearing of hearing protectors, the proposal would require the mine
operator to pay for the miner's follow-up medical evaluations. MSHA
believes that the mine operator has the primary responsibility for
work-related medical problems. On the other hand, if the person
evaluating the audiogram determines that the suspected medical
pathology is not related to the wearing of hearing protectors, then the
proposal would require the mine operator to instruct the medical
professional to inform the miner of the need for medical follow-up, but
would not require the mine operator to pay for it or to be informed of
the findings. In such cases, therefore, the follow-up otological
examination would be at the miner's expense. Although MSHA agrees that
taking action to keep miners healthy would be beneficial to the mine
operator, the Agency contends that it would be inappropriate to require
mine
[[Page 66443]]
operators to pay for non-work-related medical problems.
MSHA also does not believe that it would be appropriate for mine
operators to be informed of medical findings that are unrelated to the
miner's occupational noise exposure or to the wearing of hearing
protectors. If a mine operator would want this information, the
proposal would permit the release of this information only upon the
written consent of the miner. MSHA has included this provision out of
concern for the privacy rights of the miner. A related provision is
considered in somewhat more detail in the discussion of proposed
Sec. 62.160.
Section 62.180 Follow-Up Corrective Measures When STS Detected
MSHA's proposal would require that, unless a physician or
audiologist determines that an STS is neither work-related nor
aggravated by occupational noise exposure, mine operators would have 30
calendar days after the finding of an STS to--
(1) Retrain the miner in accordance with Sec. 62.130;
(2) Provide the miner with the opportunity to select a hearing
protector, or a different hearing protector if the miner has previously
selected one, from the selection offered under Sec. 62.125; and
(3) Review the effectiveness of any engineering and administrative
controls to identify and correct any deficiencies. In addition,
pursuant to proposed Sec. 62.120(b), an operator would be required to
ensure that a miner who has incurred an STS wears provided hearing
protection.
A hearing loss of 10 dB from a miner's prior hearing level is of
enough significance to warrant intervention by a mine operator, unless
it is determined the loss is not work-related. If the controls in place
are effective--including the training--this loss should not be
occurring. It should be noted that the retraining required is to take
place within 30 days after the finding of the STS, and thus it is
unlikely mine operators can satisfy this requirement through their part
48 training programs.
MSHA's proposal does not include a provision for transferring a
miner who incurs repeated STS's or a reportable hearing loss. A miner
transfer program would be complex to administer, and would probably not
be feasible in the metal and nonmetal sector. This sector consists
largely of smaller mines which may be unable to rotate workers to other
assignments on a long-term basis.
Most commenters on this issue suggested that MSHA adopt OSHA's
requirements. One of these commenters, however, disagreed with OSHA's
allowance for discontinued use of hearing protectors when an STS was
found to be temporary. The remaining two commenters recommended that
the mine operator only be required to retrain the miner in the use and
fit of the hearing protector.
OSHA's noise standard requires that the work-relatedness of an STS
be determined only by a physician. Employees, who have a work-related
STS and are not using hearing protectors, must be fitted with hearing
protectors, be trained in their use and care, and be required to use
them. Employees who have an STS and are using hearing protectors must
be refitted, be retrained, and be provided with hearing protectors
offering greater attenuation when necessary. OSHA does not stipulate a
time frame for conducting follow-up procedures.
MSHA believes that audiologists have sufficient training and
medical expertise to determine the work-relatedness of an STS, and that
it would be needlessly restrictive to limit this determination to a
physician as in OSHA's standard.
MSHA, however, like OSHA would not permit technicians to make this
determination. MSHA believes that while qualified to conduct and
evaluate audiograms under the supervision of a physician or
audiologist, technicians do not have the necessary training nor medical
expertise to determine if an STS is work related. MSHA has determined
that it is necessary to have a physician or audiologist determine the
possible work relatedness of any STS. For example, the physician may
determine that a miner's STS resulted from: a bad cold or sinus
condition; taking certain medication, such as heavy doses of aspirin;
or an acoustic neuroma (type of tumor). Careful diagnosis may, on the
other hand, reveal that the STS is work related and caused by improper
fit of the hearing protector.
MSHA, after reviewing comments and related regulations, believes
that the proposed corrective measures are adequate and necessary to
prevent further deterioration of the miner's hearing acuity after an
STS has been determined. MSHA believes that the 30 day requirement for
retraining, selection of a hearing protector or different hearing
protector, and evaluation of noise controls is reasonable.
Retraining
If a miner has an STS, Sec. 62.180(a) of this proposal would
require that the miner be retrained in accordance with Sec. 62.130, and
a record kept of such training.
The specific training elements contained in Sec. 62.130 are
discussed in the provisions of this preamble describing those
respective sections, including the required certification thereof. Such
retraining could be conducted in conjunction with the annual refresher
training, under 30 CFR part 48, but only if the latter is so approved
and scheduled to be completed within 30 days of the finding of an STS.
If the annual refresher training is not conducted within 30 days, the
retraining for miners with an STS would have to be conducted
separately. It would not be permissible to wait until the next annual
refresher training.
Provide Opportunity To Select a Hearing Protector or Different Hearing
Protector
In the mining industry, miners are typically exposed to high sound
levels and some of the miners may be more susceptible to hearing loss
from the noise exposures than others. Consequently, if a miner is
diagnosed with an STS, then he or she must be given the opportunity to
select a hearing protector or different hearing protector.
Section 62.180(b) of this proposal directs the mine operator to
afford the miner the opportunity to select adequate hearing protection
from those offered by the mine operator under Sec. 62.125. While that
section of the proposal only requires the mine operator to offer one
type of ear plug and one type of ear muff, MSHA presumes that most mine
operators will offer a range of each. Pursuant to Sec. 62.120(b), the
operator is required to ensure that a miner with an STS wears the
hearing protector.
The choice of hearing protectors from this selection will be based
on the miner's personal preference. The benefits of allowing the miner
to select his/her hearing protector are discussed under Sec. 62.125
Selection of hearing protector. MSHA believes that even though a miner
may select a protector with a noise reduction rating lower than that
which might be selected by a mine operator in such cases, factors such
as comfort are more critical in ensuring that the miner will fully
utilize this critical piece of personal protective equipment. Moreover,
as discussed in the section on Hearing protector effectiveness, MSHA
has concluded that there is no standardized objective method to
determine whether an additional or different hearing protector would
provide the miner with greater protection. MSHA requests further
comment on this issue.
[[Page 66444]]
Review Effectiveness of Controls
Upon the finding of an STS, MSHA would require, under
Sec. 62.180(c) of the proposal, the mine operator to review the
effectiveness of any engineering and administrative controls. The mine
operator would need to correct any deficiencies. The implementation and
maintenance of either engineering or administrative controls or a
combination of such controls above the PEL is the primary method for
reducing a miner's noise exposure and, thus, reducing the risk of
hearing loss. OSHA's current noise regulation does not require a review
of the effectiveness of engineering and administrative controls when an
STS is found.
The inadequacy of engineering or administrative controls or a
combination of such controls may well be the contributing factor in the
development of a miner's STS. Thus, the proposal would require the mine
operator to review the effectiveness of controls and update or modify
them, as necessary and feasible, to reduce the miner's noise exposure.
Miner Transfer
The Federal Mine Safety and Health Act of 1977 (30 U.S.C. 811)
requires health standards to include, as appropriate, provisions for
removing a miner from hazardous exposure where that miner may suffer
material impairment of health or functional capacity. MSHA has decided
not to include such a provision in its proposal.
MSHA's current noise standards do not contain such a transfer
provision. Nor does the OSHA noise standard have such a requirement.
In its ANPRM, MSHA requested comments regarding the need for a
transfer provision in the proposed rule for a miner with a diagnosed
occupational hearing loss. In response, many commenters stated that a
miner transfer provision is not appropriate. Some of the concerns
expressed by the commenters included: the negotiation of disability
accommodation sections in labor contracts; problems with rate retention
and seniority provisions in existing contracts; the contribution of
non-occupational noise exposure to the hearing loss; uncertainty as to
the etiology of the hearing loss; and the impracticality in small
operations. However, several commenters disagreed, indicating that the
transfer of a miner is appropriate when other efforts to halt the
progression of the hearing loss have failed. They added that the safety
of a miner with a hearing loss would be jeopardized, due to the
inability to hear warning signals and/or understand verbal instructions
in the noisy environment (a hazard to other miners as well).
Several of the U.S. Armed Forces, and some other countries, allow
for removal or transfer of employees from noisy areas.
Although MSHA would encourage mine operators to transfer miners who
have incurred a hearing impairment, MSHA believes that a miner transfer
provision would not be feasible, at the vast majority of small mining
operations, because of limited personnel and non-noise exposed
occupations. At larger mines transfer may be feasible; however, MSHA
believes that the obligation to utilize all feasible administrative (as
well as engineering controls) would reduce miner exposure time to
harmful noise in much the same way as a transfer provision but without
unwarranted complexity.
Section 62.190 Notification of Results; Reporting Requirements
This section of the proposal would require that miners be notified
of audiometric test findings, and that the Agency be notified of any
instances of ``reportable hearing loss.''
The proposal would require the mine operator, within 10 working
days of receiving the results of an audiogram, or the results of a
follow-up evaluation pursuant to Sec. 62.170(a)--those follow-ups on
which the mine operator would receive results--to notify the miner in
writing of the results and interpretations, including any finding that
an STS or reportable hearing loss has occured. The notification would
include an explanation of the need and reasons for any further testing
or evaluation that may be required.
MSHA believes that informing miners of the results of their
audiometric tests in a timely manner is critical to the success of an
HCP. Immediate feedback upon completion of the testing provides the
greatest benefit.
The proposal would require mine operators to inform MSHA of any
reportable hearing loss, unless the physician or audiologist has
determined the loss is neither work-related nor aggravated by
occupational noise exposure. This essentially restates for noise the
requirements of 30 CFR part 50, but with an explicit definition of
reportable hearing loss for the first time. Having a uniform definition
will ease reporting burdens on mine operators while promoting the
development of an improved data base on hearing loss in the mining
community.
The proposal would define a reportable hearing loss as a change in
hearing acuity for the worse relative to the miner's baseline audiogram
of an average of 25 dB or more at 2000, 3000, and 4000 Hz in either
ear. Should an annual audiogram actually indicate an improvement in
hearing at any time, this audiogram would, pursuant to Sec. 62.140,
become the baseline for purposes of determining whether a reportable
hearing loss has occurred. As noted herein, MSHA is seeking comment on
whether part 50 should collect information on harm on less dramatic
shifts in hearing acuity, and how reporting should be accomplished in
cases in which an operator lacks audiometric data.
Notification of the Miner
Section 62.190(a) of MSHA's proposal would require that within 10
working days of receiving the results of an audiogram or follow-up
evaluation, the mine operator shall notify the miner in writing of--
(1) the results and interpretation of an audiometric test,
including any finding of an STS or a reportable hearing loss; and
(2) if applicable, the need and reasons for any further testing or
evaluation.
MSHA has no current requirements in this area. The proposed time
frame is consistent with the time frame for notification to the Agency,
under part 50, of cases of reportable hearing loss. MSHA's proposal
would differ from OSHA's standard in this regard and in several other
respects: the miner would be informed of the need and reason for
further medical evaluations, and the miner would be informed of the
finding of a reportable hearing loss. Moreover, OSHA's requirement does
not specify how long, following the annual audiogram, an employer can
take to make this determination.
All commenters on this issue favored notifying the employee of the
results of audiometric testing and follow-up examinations. They
differed, however, as to the time to be allotted for such notification
and the requirements of such notification.
Many commenters endorsed OSHA's requirements. One commenter agreed
that written notification be provided within 21 days, the same as OSHA,
but recommended that such notice be provided for all audiometric test
results. This commenter stated:
It is our policy to notify all employees of the results of their
audiometric tests in writing. An appropriate time frame would be 21
days from the time the employee's facility is made aware of the
results. If the time frame for notification is 21 days from the time
of the actual test, many problems may arise. If a mobile testing
service is utilized, the results may not be sent in for analysis for
at least
[[Page 66445]]
a week. Our audiological staff reviews all of our audiograms in-
house rather than relying on outside services for analysis. Some of
our testing services microfilm the tests or analyze them separately
which means that a delay of a few weeks may occur. The purpose
should be that the employee receive results in a timely enough
fashion so that they are meaningful.
One commenter recommended that written notification be provided to
the miner within 30 days of determining a confirmed STS. Another
commenter recommended that miners be notified of an STS, including any
optional retest, within 30 days of the testing. This commenter stated
that:
Service providers have taken undue advantage of a perceived
grace period in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. By the time audiometric tests are
administered, entered into a computer, returned to an employer, and
then finally returned to the employee, the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Notification of STS, including the optional retest of STS-
affected employees, should be completed within a 30-day period
following testing. OSHA's time limit of 21 days following
notification to the employer creates a loophole which makes the
employee wait all too long for feedback regarding STS.
Other commenters recommended notifying miners of the results of their
audiometric tests, but did not specify a time frame.
The U.S. Armed Forces regulations, and standards of some members of
the international community, vary on the time frame for notification.
The time frame in MSHA's proposal is shorter than the time frame
for notification in OSHA's standard, but is consistent with MSHA's
requirement that the Agency be notified of reportable hearing losses
within 10 working days. MSHA's proposal would also differ from OSHA's
standard in that the miner would be informed of the need and reason for
further medical evaluations; and the miner would be informed of the
finding of a reportable hearing loss. In addition, pursuant to
Sec. 62.170(b), MSHA's proposal would require the mine operator to
instruct the physician to notify the miner of the need for an
otological examination based upon a medical pathology of the ear that
is unrelated to the affected miner's noise exposure or the wearing of
hearing protectors. MSHA believes that miners have a right to know the
results of any medical tests conducted on them.
MSHA believes that it is appropriate to require written
notification. Under proposed Sec. 62.200, the miner would in any event
have access to all required records under this part upon written
request. Providing the notices in writing would ensure there are no
misunderstandings on the part of miners as to the severity of the
problem.
MSHA believes that informing miners of the results of their
audiometric tests in a timely manner is critical to the success of an
HCP. Immediate feedback upon completion of the testing provides the
greatest benefit. Generally, the employee shows the most interest and
concern regarding the effects of noise on his/her hearing immediately
following testing. Providing the results several weeks or months later
may have less of an impact. In many cases, however, it may not be
feasible or practical to inform miners immediately of the results of
their audiometric tests. The proposal, consequently, would allow mine
operators up to 10 working days to inform the miner (the same time
period as provided under part 50 for notification of MSHA of cases of
reportable hearing loss). Because the proposal would allow up to 30
calendar days to evaluate audiograms, it could be as long as 44 days
following testing before the miner is informed of the results. In the
case of an audiometric retest, it could be as long as 104 days before
the miner is informed of the results of the retest. MSHA believes that
it is necessary to specify a maximum time frame for informing miners of
the audiometric test results in order to prevent undue delays.
Reporting Noise-Induced Hearing Loss (NIHL)
Section 62.190(b) of this proposal would require the mine operator
to report hearing loss under 30 CFR part 50, if the results of an
audiogram or follow-up evaluation indicate that a miner has incurred a
``reportable hearing loss.'' This section is designed to refine, in
light of this proposal, MSHA's existing reporting requirements for
injuries and illnesses in 30 CFR part 50, so as to ease reporting
burdens on employers while promoting the development of an improved
data base on hearing loss in the mining community.
The current reporting requirements provide that mine operators
report a hearing loss whenever a physician determines that it is work
related, or whenever an award of compensation is made. NIHL is
specifically listed among the examples of occupational illnesses to be
reported when it is work related. The proposal would establish the
reporting definition for this purpose: but the report would only be
required under part 50 if the hearing loss is suspected to be work
related.
OSHA does not have reporting requirements: i.e., a level which
triggers notification to the agency so that it can intervene. It does,
however, have recording requirements for noise, so that information is
gathered about NIHL and is available to employers, employees, and
agency personnel. In June 1991, OSHA issued its current policy (1991)
for reporting NIHL (on the OSHA Form 200). This policy requires
employers to record a work-related shift in hearing of 25 dB or more in
either ear from the original baseline audiogram averaged over 2000,
3000, and 4000 Hz. The recording criteria use identical evaluation
frequencies as required for determining an STS. The policy allows a
correction for presbycusis when determining reportability. In January
1996, OSHA published a proposal to revise agency recordkeeping
standards. Under the proposal's mandatory Appendix B, the recording
requirement would drop to a work-related shift in hearing of 15 dB or
more in either ear. OSHA notes it is proposing this change to ensure
the recording of any STS (a 10 dB shift under OSHA's standard), with
some allowance made for instrumentation variance.
In its ANPRM, MSHA discussed the problems that the Agency is
experiencing with its existing reporting requirements. Of the
commenters addressing this issue, many recommended that MSHA require
reporting of a 10-dB average loss in either ear at 2000, 3000, and 4000
Hz (the OSHA STS criteria). One commenter favored reporting any job-
related loss and another stated that the criteria of reporting an STS
was too high because ``* * * the worker['s] hearing loss has progressed
too far with this shift to be a reliable preventative measure.'' Other
commenters stated that the STS criteria represent a slight change in
hearing and is not meaningful for reporting purposes. Two commenters
recommended that the criteria for reporting be that used for defining
impairment (the AAO-HNS 1979 criteria).
Some hearing conservation associations have opposed OSHA's current
policy, arguing that employers should record the NIHL when the employee
incurs an STS. Driscoll and Morrill (1987) presented the position of
the American Industrial Hygiene Association (AIHA) in a paper entitled
``A Position Paper on a Recommended Criterion for Recording
Occupational Hearing Loss on OSHA Form 200''. AIHA concluded that ``a
confirmed STS which results from workplace noise exposure is considered
an appropriate
[[Page 66446]]
measure for surveillance or recordkeeping purposes.''
The National Hearing Conservation Association (NHCA) in a letter
from their President, Susan Cooper Megerson (1994), to Joseph Dear,
Assistant Secretary of Labor for Occupational Safety and Health, urged
OSHA to require the recording of an occupational hearing loss when an
STS was confirmed. NHCA contends that recording hearing loss after it
reaches an average of 25 dB or more at 2000, 3000, and 4000 Hz is
``dangerously underprotective and not technically well founded.''
Suter (1994) in a letter to Sue Andrei of OSHA's Policy Directorate
urged OSHA to adopt a policy of recording persistent occupational
hearing loss at an STS instead of at an average of 25 dB or more at
2000, 3000, and 4000 Hz.
MSHA's proposal would define a ``reportable hearing loss'' as a
change in hearing threshold relative to the miner's original baseline
audiogram of an average of 25 dB or more in either ear at 2000, 3000,
and 4000 Hz. If a physician determines that the hearing loss is neither
work-related nor aggravated by occupational noise exposure, then it
would not be considered a reportable illness under part 50. As
discussed in connection with proposed Sec. 62.140, if an audiological
exam showed a significant improvement in hearing acuity, the original
baseline would be supplemented to reflect this: a correction which
would then affect the reportability of hearing loss. Furthermore, as
noted in the discussion of proposed Sec. 62.160, the proposal would
allow the correction of audiograms for presbycusis when determining the
reportability of shifts in hearing threshold levels.
In selecting its reporting criteria, MSHA took into account that a
loss of this magnitude is one that diminishes quality of life and the
ability to understand speech in noisy environments. MSHA's reporting
criteria, although not impairment per se, represent a substantial loss
which would provide a reliable indication of the effectiveness of
MSHA's rule and enforcement programs. Moreover, the calculation would
be the same as that used to determine an STS and, thus, not an extra
burden. The use of other criteria, such as the AAO-HNS 1979 criteria
for impairment, would require an additional set of calculations at
different frequencies.
MSHA is concerned, however, that reporting only losses of 25 dB may
not provide MSHA a full picture of hearing loss in the mining industry.
A loss of 25 dB is used by many states as a basis for making disability
awards. Some have recommended that any STS (10 dB loss) should be
captured in a hearing loss data base. OSHA, which currently requires
any 25 dB loss to be captured in an employer's log, has proposed to
capture any 15 dB loss. MSHA accordingly solicits comment on this
point.
An important goal of the proposal is to clarify the level of
hearing loss which is reportable. MSHA believes that its current
reporting requirements are vague; consequently, cases of NIHL are
inconsistently reported or not reported. Some mine operators have
reported even a small loss, while others only reported when a miner
received an award of compensation. In other cases, mine operators have
not reported when an award of compensation was granted because the
miners had retired. Inconsistent reporting also results because worker
compensation regulations vary from state to state, i.e., the same
hearing loss would be compensable and thus reportable in some states
and not in others. For these reasons, current hearing loss data
reported to MSHA under part 50 cannot be used to accurately
characterize either the prevalence or the degree of hearing loss in the
mining industry.
Reporting at a specified level, as required by the proposal, would
eliminate reliance on workers' compensation awards as a criteria for
defining NIHL to be reported. Nevertheless, part 50 would still require
that awards of compensation be reported in those cases when the loss
had not been previously reported. Two general examples of such cases
are (1) if the miner had incurred the loss before the current mine
operator conducted the baseline or pre-employment audiogram and
subsequent testing did not measure a reportable loss, and (2) if the
miner had not been in an HCP or had not received an audiometric test
while employed by the operator.
In this regard, MSHA would like comment on how to define
``reportable'' hearing loss for those operators who do not have
audiometric test data. Not all mine operators will be required to
obtain audiometric test data under the proposed rule; thus, such
operators may not be able to use a definition of reportable hearing
loss defined in this manner. MSHA also requests specific suggestions on
how to capture data on work-related NIHL: (1) that is not discovered
until after the miner's employment is terminated; and (2) that the
miner had accumulated from work with several employers.
MSHA does not expect mine operators to report the same reportable
hearing loss each year that a miner works at the mine. The next
reportable hearing loss would not be reported until the miner incurs
another 25 dB shift (50 dB shift from the original baseline). MSHA does
intend for each ear to be treated independently in terms of a
reportable event, unless the reportable loss occurs in both ears during
a particular year. (For example, 28.7 dB, left ear, 25.9 dB, right ear,
not corrected for presbycusis.) Although not specifically required in
its proposal, MSHA anticipates that mine operators would indicate when
reporting to MSHA--
(1) the actual average hearing loss;
(2) in which ear(s) the loss occurred; and
(3) whether the audiograms were corrected for presbycusis. (For
example, 28.7 dB, left ear, corrected for presbycusis.)
Section 62.200 Access to Records
Authorized representatives of the Secretaries of Labor and Health
and Human Services would have immediate access to all records required
under this part.
Moreover under the proposal, a miner or former miner, or his/her
designated representative with written consent, would have access to
all the records that the mine operator is required to maintain under
this part for that individual miner or former miner. Also, the miners'
representative is in all cases to have access, for miners they
represent, to noise training records and notices required under
Sec. 62.120(f) to be given to miners exposed to noise above various
levels.
The mine operator would have 15 days from receipt of a written
request to provide such access. The proposal would define ``access'' as
the right to examine and copy records. The first copy of any record
requested by a person is to be provided without cost to that person,
and any additional copies requested by that person are to be provided
at reasonable cost.
Upon termination of employment, mine operators would be required to
provide a miner without cost an actual copy of all his/her own records
(those required under this part).
MSHA has no uniform records access provision that address these
issues--though the Agency and NIOSH do have statutory rights to access.
The provisions proposed here are similar to those in other health
standards proposed in recent years by the Agency.
Section 103(c) of the Mine Act states that:
[[Page 66447]]
The Secretary, in cooperation with the Secretary of Health,
Education, and Welfare, [now Health and Human Services] shall issue
regulations requiring operators to maintain accurate records of
employee exposures to potentially toxic materials or harmful
physical agents which are required to be monitored or measured under
any applicable mandatory health or safety standard promulgated under
this Act. Such regulations shall provide miners or their
representatives with an opportunity to observe such monitoring or
measuring, and to have access to the records thereof. Such
regulations shall also make appropriate provisions for each miner or
former miner to have access to such records as will indicate his own
exposure to toxic materials or harmful physical agents.
OSHA's requirements for access to records incorporate its standards
for ``Access to Employee Exposure and Medical Records'' [29 CFR
Sec. 1910.20(a)-(e) and (g)-(i)]. OSHA's requirements and MSHA's
proposal are essentially the same.
All of the commenters addressing this issue favored providing
affected miners with reasonable access to required records. Most of
these commenters also recommended that the request for access to
records be in writing.
The Agency agrees, after reviewing comments and related
regulations, that access to noise records by both employees and the
government is essential, and does not believe the costs of providing
such access will be significant. As noted by OSHA, in its preamble to
its proposed Hearing Conservation Amendment (46 FR 4161)--
Such access will serve to educate employees as to the state of
their hearing and the effectiveness of the program, and will
encourage their conscientious participation in it. The information
in the records will be invaluable to the Assistant Secretary in the
enforcement of the amendment and will be useful in research into the
effects of occupational noise exposure. The Director of NIOSH will
also be primarily interested in the records for research purposes.
MSHA also agrees that requests from miners, miner's designated
representatives, and miner's representatives be in writing. This
requirement would benefit both the miners and mine operators by
protecting them in matters of dispute regarding the date on which the
request was submitted. MSHA's access to records requirements would not
preclude the mine operators from requiring the requester to sign a
receipt after receiving the records. In addition, the definition of
miner's ``designated representative'' specifies that such person have
written authorization to request records for each miner or former miner
represented. Because requested records may contain personal, private
information, MSHA intends that the miner's designated representative
would present such authorization to the mine operator when requesting
records on behalf of a miner or former miner.
According to the proposal the mine operator would have 15 days to
provide the miner, former miner, or miner's designated representative
access to the requested records. MSHA believes that it is reasonable to
require the mine operator to provide access because the proposal would
require the records to be maintained at the mine site.
The mine operator has some choice as to how to provide records
requested by an employee or representative. The mine operator could
provide a copy, make available mechanical copying facilities, or loan
the record to the requester for a reasonable time to enable a copy to
be made. The proposal provides that if a copy is requested, however, it
shall be provided, and the first copy shall be at no cost. If a copy of
the record had been provided previously without cost, the proposal
would allow the mine operator to charge reasonable, non-discriminatory
administrative costs for providing an additional copy of the record.
The mine operator, however, could not charge for the first copy of new
information which subsequently had been added to the record.
MSHA believes that its proposed requirements for access to records
are both reasonable and necessary to meet its mandate under the Mine
Act. MSHA would welcome comments on what actions are required, if any,
to facilitate the maintenance of records in electronic form by those
mine operators who desire to do so, while ensuring access in accordance
with these proposed requirements.
Section 62.210 Transfer of Records
The proposed standard would require mine operators to transfer all
records (or a copy thereof) required by this part to any successor mine
operator. The successor mine operator would be required to receive
these records and maintain them for the period required. Additionally,
the successor mine operator would be required to use the baseline
audiogram obtained from the original mine operator (or supplemental
baseline audiogram as appropriate) for determining an STS and
reportable hearing loss.
MSHA's existing noise standards do not address the transfer of
records, nor does MSHA have general standards on this point. The
provisions proposed here are similar to those in other health standards
proposed in recent years by the Agency. OSHA's standard requires
transfer of records and, in addition, incorporates by reference
transfer provisions found in its ``Access to Employee Exposure and
Medical Records'' standards (29 CFR 1910.20 (h)). MSHA's proposal
regarding the transfer of records is essentially the same as in OSHA's
regulations.
MSHA's ANPRM did not address the transfer of records and no
comments were received on this subject. MSHA considered OSHA's
requirements and believes that they are both reasonable and necessary
to ensure that records are maintained for the required periods of time
when a mine operator ceases to do business.
Requiring successor mine operators to use the prior baseline
audiogram will provide the miners with a greater degree of protection
by assuring that an STS or reportable hearing loss is based on the
original or supplemental baseline taken under the original mine
operator, instead of based on a new baseline. Generally if a new
baseline would be established by a successor mine operator, the miner
would need to lose additional hearing acuity before the corrective
action triggered by the occurrence of an STS is implemented or a
hearing loss is required to be reported.
IV. Feasibility
MSHA has tentatively concluded that it is feasible for the mining
industry to take the actions specified in the proposed rule. MSHA has
also tentatively concluded that at this time, it may not be feasible
for the mining industry to comply with two changes that would otherwise
be warranted to further reduce the risk of impairment from occupational
NIHL--reducing the PEL to a TWA8 of 85 dBA, and reducing the
exchange rate from 5-dB to 3-dB.
As background, this part begins with a review of the pertinent
legal requirements for setting health standards under the Mine Act and
an economic profile of the mining industry.
Pertinent Legal Requirements
Section 101(a)(6)(A) of the Mine Act requires the Secretary to set
standards which most adequately assure, on the basis of the best
available evidence, that no miner will suffer material impairment of
health over his/ her working lifetime. In addition, the Mine Act
requires that the Secretary, when promulgating mandatory standards
pertaining to toxic materials or harmful physical agents, consider
other factors, such as the latest scientific data in the field, the
feasibility of the standard and experience gained under the Act and
other health and safety laws. Thus, the
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