In its 24-page report, the GAO said key scientific studies support MSHA's conclusion that tightening the dust limit would reduce miners' risk of getting black lung: "Our evaluation of the reports MSHA used to support its proposal and the key scientific studies on which the reports were based shows that they support the conclusion that lowering the PEL [permissible exposure limit] from 2.0 mg/m3 to 1.0 mg/m3 would reduce miners’ risk of disease. The reports and key studies concluded that miners’ cumulative exposure to coal mine dust at the current PEL over their working lives places them at an increased risk of developing progressive massive fibrosis, and decreased lung function, among other adverse health outcomes. . . . To mitigate the limitations and biases in the data, the researchers took reasonable steps, such as using multiple x-ray specialists to reduce the risk of misclassifying disease and making adjustments to coal mine dust samples where bias was suspected.
The report also says "Researchers used appropriate analytical methods to conclude that lowering the existing PEL would decrease miners’ risk of developing black lung disease. For example, in addition to taking steps to precisely estimate a miner’s cumulative exposure, the researchers accounted for several factors in their analyses—such as the age of the miners, the carbon content of the coal (coal rank), and other factors known to be associated with the disease—to better estimate the effect of cumulative exposure to coal-mine dust."
Completion of the GAO report frees MSHA to finalize the rule, but agency officials last week offered no timeline for when they would do so, reports Ken Ward Jr. of The Charleston Gazette. Read the report here.