In response to a rebound in both the number of cases and severity of pneumoconiosis, or black lung disease, U.S. Mine Safety and Health Administration (MSHA) officials have released a final rule on new allowable respirable dust levels for the coal mining industry.

The final rule indicates a 25% reduction in permitted levels of breathable coal dust to 1.5 from 2 milligrams per cubic meter of air. This also halves the standard to 0.5 from 1 for certain mine entries and miners with pneumoconiosis. Dust samples, meanwhile, will now be mandated whenever mines operate at 80% of production—up from 50%; the new level, MSHA officials said, is “more representative of actual working conditions.”

Measurement in terms of readings and averages will also be enhanced—along with thorough on-shift examinations of dust controls and verifiable controls through a written certification. Additionally, immediate action will be required if dust levels are high, MSHA said. Current exposure levels are largely determined via sampling to be increased under the new rule—in particular, near high dust level areas, such as those closest to the production operations.

In an April 24 public hearing in Morgantown, West Virginia, USA, officials said black lung prevalence dipped between the 1970s and 1990s, but voiced concern about current recorded increases of other lung diseases including emphysema and progressive and massive fibrosis.