The data now seem to clearly refute certain old ideas about asbestos, including the notions that lung cancer cannot occur without obvious interstitial fibrosis on chest film, that chrysotile does not cause lung cancer and that there is no real interaction between smoking and asbestos exposure except among insulation workers. As a consequence of these old beliefs, claims from smokers who were exposed to asbestos and developed lung cancer have been denied for years by workers' compensation boards, often on the grounds that smoking represented the greater risk. However, a smoker exposed to asbestos is more than twice as likely as a smoker who was not exposed to asbestos to die of lung cancer (whether there is a synergistic effect at that level of exposure or not), a conclusion supported by the totality of the literature and individual studies of chrysotile-exposed workers in which the data have been so analyzed.1 Thus, if one looked at a population of smoking asbestos workers who developed lung cancer and compared them only with unexposed smokers who developed the disease, one would conclude that occupational exposure was the cause of more than half of the cases; this is the presumptive criterion for an occupational disease. A strong case could be made that the risk conferred by exposure to asbestos for a smoking worker should be compared with the background risk for other smokers, not nonsmokers. By that standard, many claims now denied would be accepted.
Asbestos is an example of a health problem concerning which attitudes are changing, although I could as easily use asbestos as an example of how slow they are to change. In developing countries, chrysotile is no longer being defended as harmless. Instead, it is being defended as having an acceptable cost/risk ratio: asbestos will be handled with exquisite care by well-trained workers in the production of cement pipe that will provide clean water, which will save innumerable lives. Excuse me if I, and the rest of the world, do not buy this argument. The time has come for Canada to accept the inevitable global ban on exports of asbestos.2
Signature
Tee L. Guidotti
Department of Public Health Sciences University of Alberta Edmonton, Alta.
References
- 1.Zhu HL, Wang ZM. Studies of occupational lung cancer in asbestos factories in China. Br J Ind Med 1993;50:1039-42. [DOI] [PMC free article] [PubMed]
- 2.LaDou J, Landrigan P, Bailar JC III, Foa V, Frank A, on behalf of the Collegium Ramazzini. A call for an international ban on asbestos [editorial]. CMAJ 2001;164(4):489-90. [PMC free article] [PubMed]