On April 18, 2024, the U.S. Mine Safety and Health Administration (MSHA) issued its final rule, Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection, to reduce miner exposures to respirable crystalline silica and improve respiratory protection for all airborne hazards.

The final rule lowers the permissible exposure limit (PEL) for respirable crystalline silica to 50 micrograms per cubic meter of air (µg/m³) for a full shift, calculated as an eight-hour time-weighted average (TWA) for all miners. It establishes an action level for respirable crystalline silica at 25 µg/m³ for a full shift, calculated as an eight-hour TWA for all miners. The new rule includes uniform requirements for controlling and monitoring exposures to respirable crystalline silica at coal and metal and nonmetal (MNM) mines and includes medical surveillance requirements for MNM mines, modeled on the existing medical surveillance requirements for coal mines. And the rule updates existing respiratory protection requirements by incorporating by reference a voluntary consensus standard by the American Society of Testing and Materials (ASTM) that reflects the latest advances in respiratory protection technologies and practices – ASTM F3387-19 Standard Practice for Respiratory Protection.

The final rule will take effect on June 17, 2024. Coal mine operators have 12 months to come into compliance with the final rule’s requirements while MNM mine operators have 24 months to come into compliance (including medical surveillance).

NPR reported that the new regulation requires mining companies to monitor the air miners breathe while working, and adjust working conditions when excess silica dust is present. Instances of overexposure must be reported to MSHA, a requirement that was not in a regulation initially proposed last year but was inserted after the news organizations' reporting and complaints from mine safety advocates.

The regulation imposes requirements that have never existed for MNM mines, including a health surveillance program with free periodic exams to detect early stages of silica-caused lung disease. The results of those exams must be reported to the National Institute for Occupational Safety and Health, which has monitored the health of coal miners for decades.

MNM mines will also be required to do more dust sampling. Both that and the medical surveillance program will require extensive and costly additions to the mining process. That could trigger challenges.

The National Mining Association, which represents mine operators, welcomed one key element of the new regulation.

“We fully support the new, lower [silica dust] limits contained in the rule and are committed to working to improve the health and safety of our miners,” Ashley Burke, senior vice president communications told NPR.