The new rule will limit the amount of time miners can spend around silica dust. According to the U.S. Department of Labor, the rule lowers the permissible exposure to 50 micrograms per cubic meter of air for a full 8 hour shift.

It’s up to the mining companies to take corrective actions if the threshold is met.

Silica dust is a known carcinogen and is linked to black lung, an incurable lung disease. It’s different than coal dust, which carries its own dangers.