Respirable Crystalline Silica


  • Posted on Jun 3, 2024

MSHA Final Rule

Occupational exposures to respirable crystalline silica (also known as silica dust
or quartz dust) cause adverse health effects, including silicosis (acute silicosis,
accelerated silicosis, simple chronic silicosis, progressive massive fibrosis),
nonmalignant respiratory diseases (e.g., emphysema and chronic bronchitis),
lung cancer, and kidney disease. Each of these effects is chronic, irreversible,
and potentially disabling or fatal.

On April 18, 2024, 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/m 3 ) for a full shift, calculated as an 8-
    hour time-weighted average (TWA) for all miners;
  • Establishes an action level for respirable crystalline silica at 25 µg/m 3  for a full
    shift, calculated as an 8-hour TWA for all miners;
  • Includes uniform requirements for controlling and monitoring exposures to
    respirable crystalline silica at coal and metal and nonmetal (MNM) mines;
  • Includes medical surveillance requirements for MNM mines, modeled on the
    existing medical surveillance requirements for coal mines; and
  • 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 took 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).

Final Rule as published in the Federal Register on April 18, 2024.

Final Rule on public inspection posted by Federal Register on April 16, 2024.