"Black lung is a legal term for a preventable, occupational lung disease. It is more formally known as coal workers' pneumoconiosis (CWP), and is caused by prolonged exposure to coal dust. Once coal dust is inhaled into the body it cannot be removed or discharged. It progressively builds up in the lungs and can lead to inflammation, fibrosis, even necrosis. There are two forms of the disease: "simple CWP" and "complicated CWP" (or progressive massive fibrosis)."