This testimony presented information concerning the existence of asbestos (1332214) related diseases among American workers. Concern over asbestos exposure became extremely important because of the vast numbers of workers in contact with the substance and also because the diseases produced through this contact, such as asbestosis, mesothelioma and lung cancer, were so very serious. While physical differences between the two broad classes of asbestos (amphiboles and serpentines) have been recognized, evidence suggested that both forms were carcinogenic. Workers were exposed during mining, milling, and transporting the mineral and while manufacturing and working with products. Studies which underscored the widespread problem were conducted by NIOSH and other Health, Education, and Welfare supported groups in the 1960s and 1970s. Epidemiological studies identified asbestosis, a relentlessly progressive lung disease caused by inhalation of asbestos fibers, lung cancer in which the association with asbestos was first suspected in the United States in 1935, and mesothelioma, a cancer rarely found except in individuals with a history of asbestos exposure. Asbestos was the subject of the first criteria document developed by NIOSH. Future projects in the area of asbestos control and exposure prevention were listed.