Former coal miner Ray Marcum, 83, talks about black lung disease with his eldest son, Thomas. Marcum and all three of his sons have black lung.

Ray Marcum (center) with his three sons, Thomas, standing, James, left, and Donald, right. All four men have black lung.

Dr. Donald Rasmussen, 84, is a pulmonologist in Beckley. He figures he's tested 40,000 coal miners in the last 50 years.

An unidentified coal miner is tested for black lung in a mobile clinic run by the National Institute for Occupational Safety and Health (NIOSH) in Norton, Va.

Mark McCowan, 47, was diagnosed with black lung seven years ago. Within five years, the disease advanced to progressive massive fibrosis, the worst stage of black lung.

Mark McCowan, 47, was diagnosed with black lung seven years ago. Within five years, the disease advanced to progressive massive fibrosis, the worst stage of black lung.