MSHA Final Rule to Lower Miners’ Exposure to Respirable Crystalline Silica and Improve Respiratory Protection

The Mine Safety and Health Administration (MSHA) has issued a final rule that reduces silica dust exposure and expands protection for miners’ health in the workplace. This final rule is estimated to prevent thousands of silica-related illnesses, including over a thousand deaths of miners and contractors.

MSHA requires initial exposure evaluations on employees and contractors who may be exposed above the new Action Level. Historical data cannot be used for this purpose. If exposure levels are above the Action Level, mine operators and contractors must comply with the details of the new MSHA silica standard.

Contractors at mine sites are required to adhere to this final rule.

What is changing?

The permissible exposure limit of respirable crystalline is lowered to 50 micrograms per cubic meter of air for a full-shift exposure, over an 8-hour time-weighted average. MSHA has also adopted an Action Level of 25 micrograms per cubic meter.  Where these limits are exceeded, actions must be taken by mine operators and contractors who work at mine sites.

In addition to lowering the permissible exposure limit of respirable crystalline silica, the final rule expands the responsibilities of mine operators and contractors. New requirements include:

  • Mandatory initial dust sampling
  • Periodic dust sampling is required if exposure levels are above Action Level
  • Using engineering controls to prevent overexposure to silica dust
  • Regular written evaluations of operations, regardless of changes to processes or equipment
  • Establishing medical surveillance programs to provide health examinations at no cost to workers for metal/nonmetal mines
  • Updating respiratory protection practices to comply with ASTM F3387-19

When exposed to respirable crystalline silica, miners risk developing silicosis, lung cancer, progressive massive fibrosis, and more. These severe health hazards are irreversible and can result in death. Thankfully with proper safety procedures and practices, these illnesses are preventable.

When do these changes take place?

On June 17, 2024, the new regulation goes into effect. This applies to coal and metal/nonmetal mines and includes contractors, portable mines, and seasonal operations. Compliance deadlines are April 14, 2025, for coal mine operators and April 18, 2026, for metal/nonmetal operators.

What is the next step?

At Circle Safety, our highly trained health and safety professionals can assist with industrial hygiene and safety services like exposure monitoring, jobsite and desktop audits, written programs like Medical Surveillance and Respiratory Protection, respirator fit testing and training, and more. At Circle Safety, we are dedicated to helping your company protect your workers and prevent costly fines. Contact us today to .


For more information, please visit You can also read the new rule in full at Federal Register :: Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection.

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