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MSHA Proposes New Silica Exposure Limits for Miners

This month, the Mine Safety and Health Administration (MSHA) issued proposed rules to establish a more protective exposure standard for miners’ exposure to silica dust. The MSHA is proposing to set the permissible exposure limit of respirable crystalline silica at 50 micrograms per cubic meter of air (µg/m3) for a full shift of exposure, calculated as an eight-hour time-weighted average, for all miners. Additionally, the MSHA is proposing an action level limit of 25 µg/m3 that triggers additional testing and monitoring requirements. The MSHA proposal includes other policies to protect miners’ health, including sampling and reporting requirements, corrective actions when exposure limits are exceeded, and medical monitoring.

The MSHA’s proposed action will bring the silica standard for miners in line with the existing OSHA silica exposure standards for all other industries.

“The MSHA finally issued policy reduce miner exposure to dangerous silica dust,” says Alison Lee, MD, MS, chair of the ATS Environmental Health Policy Committee. “The recent rise in black lung and other respiratory diseases in miners is wholly preventable and largely driven by exposure to silica dust.

“While I am glad that the MSHA is proposing a more protective exposure standard, it is important that the proposed rule also include effective monitoring, reporting, and intervention requirements, as well as ongoing inspections to ensure effective implementation of the proposed silica standard.”

Last Reviewed: September 2023