Black lung disease more common among miners than reported

Lung disease is a well-known deadly consequence of working in the coal industry. But a new NPR study finds miners are suffering from the most advanced form of the disease at a rate ten times higher than the government has reported. Hari Sreenivasan speaks with NPR's Howard Berkes about the causes of this late-stage lung disease, possibilities for treatment and why it's been direly underestimated.