Asbestosis, the lung disease caused by inhaling asbestos, was first recognised in 1907. The reports were so disturbing that 11 years later, the Prudential Insurance Company in New York refused to issue life policies on asbestos workers. Animal research began in 1925 but much of the early experimentation proved contradictory. For instance, during the 1930s, one group of scientists wrongly classified the chrysotile, amosite and crocidolite forms of asbestos as harmless on the basis of animal tests. (1) Others found that chrysotile caused lung damage in guinea pigs but not rabbits.(2)
In 1931 and again in 1951, experimenters reported that the injuries caused by asbestos start to heal when the animals are removed from the dusty atmosphere.(2) This is contrary to human experience where asbestosis progresses even when workers are no longer exposed. Only later were researchers able to mimic this aspect of the disease in animals.(3)
The fact that asbestos could harm the lungs was serious enough but doctors soon discovered a more alarming threat - cancer. The first reports of an association between asbestos and lung cancer came from America, England and Germany during the 1930s following examination of people who had died with asbestosis. But attempts to induce cancer in animals repeatedly failed and despite further evidence from exposed workers, the carcinogenic action of asbestos was doubted until the 1960s.(4,5) Only then were researchers able to mimic the disease in animals.
Prior to this "...a large literature on experimental studies has failed to furnish any definate evidence for induction of malignant tumours in animals exposed to various varieties and preparations of asbestos by inhalation or intratracheal injection."(6)
1) Reported in L.U.Gardner, Journal of the American Medical Association, 1938, November 19, 1925-1936.
2) J.C.Wagner, British Journal of Industrial Medicine, 1963, vol.20, 1 - 12
3) J.C.Wagner et al, British Journal of Cancer, 1974, vol.29, 252-269.
4) P.E.Enterline in Epidemiology & Health Risk Assessment, Ed. L.Gordis (Oxford University Press, 1988)
5) P.E.Enterline, American Review of Respiratory Diseases, 1978, vol.118, 975-978.
6) W.E.Smith et al, Annals of the New York Academy of Sciences, 1965, vol.l32, 456-488.
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