MSHA Proposes New Silica Rule

In brief

The federal Mine Safety and Health Administration (MSHA) released its long-awaited proposed new silica rule on June 30, 2023.

In detail

Crystalline silica is a mineral component that is present at nearly aggregate and metallic mines in the form of quartz. Mining activities can and do generate silica dust, or respirable crystalline silica, which is a known carcinogen. Exposure to respirable crystalline silica over time puts miners at risk of developing silicosis, lung cancer, and non-cancer respiratory diseases.

MSHA’s existing permissible exposure limit (PEL) for silica is 100 µg/m 3 over a full-shift exposure, which is calculated as an eight-hour time weighted average (TWA). The agency now proposes to lower the PEL to 50 µg/m 3 for a full-shift exposure. MSHA also proposes a new action level of 25 µg/m 3 for a full-shift exposure.

The new rule will require all mine operators to perform baseline sampling within 10 months after publication of the final rule to assess existing full-shift respirable crystalline silica exposure levels. Mines at which the baseline sampling are above the proposed action level or proposed PEL are required to conduct additional sampling. Mine operators whose baseline samples show exposure levels above the proposed PEL would be required to take corrective actions until subsequent sampling shows a reduction in exposure at or below the proposed PEL.

MSHA anticipates publishing the proposed rule in the Federal Register within the next week or so, at which time MSHA will begin accepting public comments on the proposed rule.

The proposed rule can be viewed here.