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May 1st, 2024
In July of 2023, the Mine Safety and Health Administration (MSHA) proposed new limits for occupational exposure to respirable crystalline silica, or silica dust, which is created by coal mining and other industrial operations and poses serious risks for those exposed to it. According to MSHA, silica dust is a recognized cause of silicosis, emphysema, chronic bronchitis, lung cancer, and kidney disease.
Previously, MSHA did not have a separate exposure limit for respirable crystalline silica for coal mines, only standards for quartz (a common form of silica), and for all respirable dust. After an extensive period during which the agency received public comments on its proposed rule, earlier this month, MSHA adopted a final rule that implemented a permissible exposure limit for respirable crystalline silica of 50 micrograms per cubic meter (µg/m3) as an eight-hour time-weighted average or TWA. This means that a miner may not be exposed to more than an average of 50 µg/m3 over an eight-hour period. MSHA’s new silica exposure limit tracks the Occupational Safety and Health Administration’s limit already in place for other industries.
The cornerstone of the basis for MSHA’s rule was the expected health benefit of reduced exposure. Consistent with the estimates in its proposed rule, MSHA’s evaluation indicated that the new exposure limit will reduce the risk of illness from silica exposures by 41.9%. The agency further found that the new limit will reduce miners’ risk of dying from silicosis by 17.6%, and the risk of death from lung cancer would fall even more sharply by 19%.
Against these remarkable benefits to the health of miners, MSHA weighed the cost to the mining industry of complying with the rule. In response to comments from the mining industry regarding the cost of compliance, MSHA estimated that about 90% of mines will be able to meet the new exposure limit without incurring added expenses for exposure control. Even so, in acknowledgment of the industry’s comments, MSHA increased its estimate of mines that would incur exposure control costs and nevertheless found that the annualized benefits of its new silica exposure rule exceeded the costs by a staggering $156.6 million.
The new rule also includes requirements for exposure monitoring and medical surveillance of employees, as well as an action level of 25 µg/m3, at which periodic sampling is required until exposures drop below the action level. Finally, the rule replaces MSHA’s respiratory protection requirements with the American Society of Testing and Materials’ consensus standards, which the agency described as “reflecting the latest advances in respiratory protection and practices.”
MSHA’s new silica rule becomes effective June 17, 2024, and mine operators have between 12 and 24 months to become compliant. The benefits of the rule in improved worker health and lives saved speak for themselves. The agency’s rule represents an advance in the protection of worker health and safety, but the rule itself and the time-consuming process involved in establishing it illustrate that workplace safety requires constant attention to hazards and control.
