Mine Safety and Health Administration
Contact: Katherine Snyder
Phone: (703) 235-1452
May 15, 1996
MSHA Alerts Underground Coal Mining Community On Silica Hazard
The Mine Safety and Health Administration (MSHA) has begun a special program to encourage adoption of improved techniques to control crystalline silica dust exposure in underground coal mines, Assistant Secretary of Labor for Mine Safety and Health Davitt McAteer announced. Mines where substantial quantities of quartz-bearing rock must be mined through or drilled during the mining process are the most likely to have high concentrations of quartz in respirable dust.
"Crystalline silica or quartz dust is an especially hazardous component of respirable coal mine dust," McAteer said. "Overexposure can result in silicosis, a lung disease which in severe cases can be fatal. We have begun working with underground coal mine operators and miners to determine how successful their current methods to control silica dust are and to encourage adoption of the latest control techniques. Our agency also will be working to increase the awareness of the health risk from silica exposure by educating both miners and mine operators."
MSHA health specialists will visit selected underground coal mines over the next four to five months to discuss the silica hazard with miners and mine operators, take special samples, analyze the quartz dust control techniques in use, and assist mine operators in trying new control methods. The program will concentrate on mines that are likely to exhibit significant quartz concentrations in respirable dust due to their geologic features and mining methods.
Mine operators who are participating in the MSHA program will be encouraged to try innovative methods to control quartz dust. MSHA will help mine operators evaluate new control measures. If a particular method is tried but fails to achieve results at a given mine, the mine operator in this program will not be penalized for the failure but will be encouraged to continue experimenting until an effective combination of techniques for that mine is identified, McAteer emphasized. Mine operators who have not been contacted by MSHA, but are interested in participating in this program, should contact the MSHA district office which has jurisdiction over the mine.
"All of us in the mining community need to work together on the problem of reducing silica exposure," McAteer said.
The special quartz dust control program being conducted this year supplements MSHA's regular, ongoing program of respirable dust sampling by coal mine operators and MSHA inspectors to determine compliance with respirable dust standards. Currently, all coal mines are required to keep miners' respirable dust exposure levels at or below 2 milligrams per cubic meter of air. In the case of a mine with high levels of silica-containing dust, a standard below 2 milligrams per cubic meter is established to protect miners from overexposure to quartz.
Improved methods to control silica dust can include changing the size of the bits that cut coal and rock, locating water sprays where they will be more effective, and using different filters in machine-mounted air scrubbers. For instance, a recent study by J.F. Colinet and others, of the U.S. Bureau of Mines, "Laboratory Evaluation of Quartz Dust Capture of Irrigated-Filter Collection Systems for Continuous Miners," identified a synthetic filter medium that may more thoroughly remove quartz from the mine air than most other filters currently used in U.S. coal mines.
This synthetic filter medium is currently being evaluated by MSHA in several coal mines. In addition, several mines are exploring the use of a new wet roof drilling technique, utilizing less than 1 gallon of water per hole drilled, which results in the control of nearly all dust generated. The use of a specific water spray located under the boom of a continuous miner has been shown to reduce quartz dust concentrations.
According to a study by MSHA personnel T.F. Tomb, A.J. Gero and J. Kogut published last December in the Journal of Applied Occupational and Environmental Hygiene, a substantial number of samples taken by MSHA in coal mines during recent years show quartz exposures in excess of 100 micrograms per cubic meter, the level at which current MSHA standards are intended to limit coal miners' quartz exposure. In addition, over the period 1985 through 1992, the article reported an increase in the quartz percentage to which coal miners in certain occupations were found to be exposed. Operators of continuous mining machines, cutting machines and roof bolting machines, along with these employees' helpers, are the underground coal mine employees most frequently exposed to excessive quartz dust.
McAteer said that MSHA has learned of several severe cases of silicosis among underground coal miners in recent years. "We are urging all coal mine operators and miners to take this hazard with the utmost seriousness.
"We know of one underground coal miner who died from silicosis while awaiting a lung transplant," McAteer said. "Another underground coal miner has been diagnosed with silicosis in his 40's. It is critical to make sure such tragedies do not recur." Last year, MSHA launched a special program focusing on silica exposure among drillers at surface coal mines after the National Institute for Occupational Safety and Health (NIOSH) discovered a number of cases of silicosis among surface coal mine employees in Pennsylvania. In 1994, the agency also issued a rule to require effective dust controls on drills.
In addition, Secretary of Labor Robert B. Reich last January appointed a nine-member advisory committee to make recommendations on the elimination of black lung disease and silicosis among coal miners.