The study purports that the system for monitoring miners’ dust exposure allows companies to cheat or exploit loopholes. CPI and NPR state that from 2000 to 2011, the Mine Safety and Health Administration (MSHA) received more than 53,000 valid samples showing an underground miner had been exposed to more dust than was allowed, yet the agency issued just under 2,400 violations. This may be attributable, in part, to rules that allow samples to be averaged, potentially masking some miners’ high exposures.

CPI’s analysis of databases maintained by MSHA found that miners have been breathing too much dust for years, but MSHA has issued relatively few violations and routinely allowed companies extra time to fix problems. CPI concludes that even when companies get caught, they have little to fear. Procedures allow companies to “take and submit five of their own dust samples to prove compliance, and the MSHA citation is expunged. The agency has routinely given companies extra time to fix cited dust problems, granting extensions in 57% of cases between 2000 and 2011.”

CPI reports that miners have been exposed for years to excessive amounts of toxic silica dust, generated as continuous miners and longwall machines cut through rock. Their research suggests that in each of the past 25 years, the average valid silica sample exceeded MSHA’s allowed limits.

“The current rules have been in effect for decades,” said MSHA Chief Joe Main. “They do not adequately protect miners from disease and are in need of reform. That is why MSHA has proposed several changes to overhaul the current standards and reduce miners’ exposure to unhealthy dust.”

MSHA proposed a rule in 2010 that would cut the overall limit for dust in half and require companies to use continuous personal dust monitors, which would provide real-time measurements. The current pumps have to be sent to a lab, where analysis can take weeks.

Under the proposed new rule, the samples would be weighted to account for shifts longer than eight hours, and companies could be cited for a single sample over the limit—rather than an average of five—or a weekly accumulation of exposure above a certain limit.