A multiyear investigation by NPR and the PBS program Frontline found that Smith and Kelly are part of a tragic and recently discovered outbreak of the advanced stage of black lung disease, known as complicated black lung or progressive massive fibrosis. A federal monitoring program reported just 99 cases of advanced black lung disease nationwide from 2011-2016. But NPR identified more than 2,000 coal miners suffering from the disease in the same time frame, and in just five Appalachian states.And now, an NPR/Frontline analysis of federal regulatory data — decades of information recorded by dust-collection monitors placed where coal miners work — has revealed a tragic failure to recognize and respond to clear signs of danger.For decades, government regulators had evidence of excessive and toxic mine dust exposures, the kind that can cause PMF, as they were happening. They knew that miners like Kelly and Smith were likely to become sick and die. They were urged to take specific and direct action to stop it. But they didn't."We failed," said Celeste Monforton, a former mine safety regulator in the Clinton administration who reviewed the NPR/Frontline findings.