Asbestos is a fibrous mineral silicate, occurring in numerous forms, of which amosite [Fe₅Mg₂(Si₈O₂₂)(OH)₂] has been shown to cause mesothelioma, squamous cell carcinoma and adenocarcinoma of the lung after long exposure times. This substance has been listed by the Environmental Protection Agency (EPA). Lung cancer is most likely to occur in those individuals who are exposed to high air-borne doses of asbestos and who also smoke. The pathogenic potential of asbestos appears to be related to its aspect ratio (lengthto-diameter ratio), size (particles less than 2 micrometers in length are the most hazardous), and to its surface reactivity.

Asbestos exposure causes thickening of and calcified plaques on the lining of the chest cavity. When inhaled it forms "asbestos bodies" in the lungs, yellowish-brown particles created by reactions between the fibers and lung tissue. This disease was first described by W. E. Cooke in 1921 and given...