MSHA has published the proposed silica rule on their website. Among other things, MSHA proposes to set the permissible exposure limit of respirable crystalline silica at 50 micrograms per cubic meter of air (µg/m3) for a full shift exposure, calculated as an 8-hour time-weighted average for all miners.

Once the rule is published a 45-day comment period will start. MSHA will hold three public meetings: one at headquarters in Arlington, one in Denver, and one that will be virtual. MSHA will then analyze the comments and prepare a final rule. 

The proposal is over 400 pages long, however, key provisions include:

  • Lowering of the Permissible Exposure Limit (PEL) from 100 µg/m3 to 50 µg/m3
  • Exposure sampling
  • Medical surveillance
  • Mine operators will be required to install, use, and maintain feasible engineering and administrative controls to keep each miner’s exposure to respirable crystalline silica at or below the PEL
  • Rotation of miners to keep each miner’s exposure below the PEL will be prohibited
  • The use of respiratory protection equipment would not be accepted as a method of compliance
  • The adoption of a “Table 1” similar to OSHA’s silica standard for construction, was not included in MSHA’s proposed rule
  • MSHA has proposed to incorporate by reference ASTM F3387-19, “Standard Practice for Respiratory Protection,” which allows for the use of respirators in limited situations, on a temporary basis to supplement engineering and administrative controls

Interested in joining a group of mine operators for a call about submitting comments to MSHA? Please email Husch Blackwell’s Beth Callaghan for more information.