During the 20th century, there has been much debate over the actual cause of pneumoconiosis, a lung disease suffered by coal miners because of their occupation. For many years, scientists believed that inhalation of coal dust was "completely innocuous" and that any respiratory disease arose from the silica that sometimes contaminated the coal.(1) In bituminous coal pits, where there is little exposure to silica, mining was not considered dangerous and consequently few observational studies were carried out in the US between 1900 and 1960. As a result, there was almost no information on the amount of coal workers' pneumoconiosis until the Public Health Service conducted studies in 1962/63.(1)
The idea that coal dust was harmless originated primarily from the vivisection laboratory. According to an editorial in the British Medical Journal,(2) scientists who believed silica to be the responsible contaminant, “take their strongest stand on the fact that animal experiments... have with few exceptions shown that pure coal dust produces no fibrogenic reaction.” Fibrosis is the formation of scar tissue and a clear sign of damage to the lung. In fact, the experimental evidence exonerated pure coal dust and pointed to silica as the cause of respiratory disease.(3)
However, the animal data were contradicted by the discovery that men who worked with pure coal dust or carbon alone, also developed pneumoconiosis.(1,2) Such evidence shows that coal dust can cause lung disease even in the absence of silica. The experimental results were further undermined when coal dust, collected at a coal face where pneumoconiosis among miners was high, proved innocuous to laboratory rats!(2)
1 ) W.K.C.Morgan in Occupational Lung Diseases, Eds. W.K.C.Morgan & A.Seaton (Saunders, 1982).
2) British Medical Journal, 1953, January 17,144-146.
3) L.U.Gardner, Journal of the American Medical Association, 1938, November 19, 1925-1936; Chronic Pulmonary Disease in South Wales III Experimental Studies, Medical Research Council Special Report Series No.250 (HMSO, 1945).
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