Mark McCowan went from having a clean X-ray to progressive massive fibrosis, or an advanced stage of black lung, within five years. At 47, seven years after his first diagnosis, he needed to pause for breaths as he showed NPR reporters the X-ray of his lung.

He is not alone, as investigated by National Public Radio and the Center for Public Integrity (CPI). After federal regulations were put in place in 1969, 70,000 miners have since died from the condition. Cases of black lung are at their highest level since 1974, and at the worst stage of the disease, cases have tripled since 1980 in a triangular region in the Appalachian mountains. The organizations report that miners have suffered from at best incompetence and at worst fraud, stemming from the mining industry and the government.

Federal limits were put in place in 1969, requiring that dust limits in coal mines were a quarter of their contemporary levels. 40 percent of miners had the disease, but soon after limits were put in place, the number fell by 90 percent. Doctors happily proclaimed that the disease would be eliminated before it was completely understood. But in 1995, tests indicated that, in fact, more cases of black lung appeared, with younger sufferers who had been in coal mines for as few as 10 years.

What happened?

Productivity is one factor. Work weeks became longer, adding about 11 more hours a week, or 600 hours of exposure a year. Production pressure grew with demand. Mining machines became more efficient than ever before; the drills, which cut through quartz and sandstone, release deadly amounts of silica into the air.

The other most prominent factor is weak enforcement by the mining industry and federal regulators. Fraud ran rampant, with mining companies taking dust samples from inside the offices, or hanging dust pumps away from coal air. Loopholes are often heavily exploited, with federal regulations allowing mines to provide samples at 50 percent production. If mine inspectors find too much dust, mines can get a do-over, with particularly egregious samples thrown out.

But while knowledge of the mining industry’s fudging of the facts at times, mine inspectors are not sure how to combat the problem. Joe Main, assistant secretary of labor for mine safety and health, says ultimately that government has to use the data given to it - putting miners in a difficult, often painful situation.