The U.S. Mine Safety and Health Administration (MSHA) has published the proposed silica rule to amend existing standards. The proposal is available at MSHA’s website.

MSHA writes that the proposal will “amend its existing standards to better protect miners against occupational exposure to respirable crystalline silica, a carcinogenic hazard, and to improve respiratory protection for all airborne hazards.”

“MSHA has preliminarily determined that under the Agency’s existing standards, miners at metal and nonmetal mines and coal mines face a risk of material impairment of health or functional capacity from exposure to respirable crystalline silica.”

The proposal will 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 eight-hour time-weighted average for all miners.

Other requirements to protect miner health, such as exposure sampling, corrective actions to be taken when miner exposure exceeds the permissible exposure limit, and medical surveillance for metal and nonmetal miners. Furthermore, the proposal would replace existing requirements for respiratory protection and incorporate by reference ASTM F3387-19 Standard Practice for Respiratory Protection. The proposed uniform approach to respirable crystalline silica occupational exposure and improved respiratory protection for all airborne hazards would significantly improve health protections for all miners and lower the risk of material impairment of health or functional capacity.

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.