Coal workers' pneumoconiosis is a preventable occupational disorder of the 
respiratory system resulting from exposure to and retention of respirable coal 
dust. It exists in two distinguishable forms: simple, which is seldom if ever 
disabling, and complicated, also known as progressive massive fibrosis (PMF), 
which is sometimes totally disabling and is associated with a high mortality 
rate. The disease affects a small proportion of active U.S. miners, and only a 
very small number develop PMF. In its more advanced stages, the disorder is 
characterized by shortness of breath. Scientific criteria for diagnosis are well 
established but are not followed in the U.S. because of Federal law and 
regulation. However, an acceptable scheme for classification of chest 
radiographs exists. Black lung benefits payable to miners, their survivors and 
dependents are approaching $2 billion annually, and regulations concerning 
eligibility for such benefits are intentionally slanted to make it possible for 
claimants to receive benefits in a manner not consistent with regulations 
governing similar payments to other occupationally employed persons or in 
accordance with established medical criteria.