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Thi Environment Asbestos An Occupational and Environmental Health Hazard t has been known for some 45 I years that excessive exposure to asbestos fibers in the work place could result in a specific type of pneumoconiosis known as asbesio- sis. A thousandfold increase in out put of asbestos during the past 60 years and more recent evidence that it is perhaps our most important oc cupational carcinogen has resulted in a worldwide focus of the scientific community upon this problem. There are four major types of as bestos: amosite, chrysotile, croddo- lite, and anthophyllite, each with different physical properties, chemi cal composition, and commercial ap plications. Approximately 95% of the asbestos used in the United States has been chrysotile. While there is evidence that all types of "The devil's icicles." asbestos are not equally hazardous, more knowledge is needed to deter mine relative toxicities of different fibers or attached impurities in pro ducing asbestosis, cancer, or meso thelioma. There is ample evidence that ex posure to asbestos causes a definite increase in the incidence of asbestosis and of cancer of the lung. Epi demiological studies have indicated that the incidence of bronchogenic carcinoma among asbestos and in sulation workers exposed during the World War H era is about seven or eight times that expected. The ex tent of the exposure is not well de fined. Selikoff etal (JAMA 204:104, 1968) estimated from a study of 370 workers that asbestos workers who smoke have about 92 times the risk of dying of bronchogenic carcinoma as men who neither work with as bestos nor smoke cigarettes. Within the last eight years there has been increasing evidence for an association between both work aud environmental exposures to asbestos and diffuse pleural and peritoneal mesothelioma. There is strong evi dence that individuals with light to heavy exposure to crocddolite, amo site, or mixtures of amosite and chrysotile have a greatly increased incidence of this rare disease. Since treatment for the asbestos diseases leaves much to be desired, The Figure reproduced from Oregon Health Bulletin. (-47:2 [Feb] 1969). every effort should be made to de crease exposures to safe levels. The the American Conference of Gov ernmental Industrial Hygienists is five fibers (length > 5/a) per milli liter of air, in the work place. This is subject to revision with better definition of hazard. Every effort should be made, to minimize expo sure through improved working con ditions; through medical supervi sion of workers, including health education; and by substitution of less-toxic materials where, possible. Enclosure ventilation and respira tory protective devices should keep exposures as near zero as possible. ' In the differential diagnosis of as bestos disease, a very detailed occu pational and residential history for the whole life of the individual is necessary. The earliest and most re liable symptom of asbestosis is shortness of breath. The earliest de tectable change is in pulmonary function as indicated by lowered vital capacity and exchange rate for carbon dioxide and oxygen. All as bestos workers should have x-ray films of the chest and pulmonary function tests as part of complete preplacement and annual health in ventories. Asbestos workers should not smoke cigarettes and with the early development of asbestosis should either be encouraged to change to other work or exposures should be extremely low. Work men's compensation laws for each state should be carefully checked to make sure that disability from as bestos disease receives adequate at tention, and physician*; should bear in mind the long latent period which may occur in this disease. The latent period for asbestosis may be only a few years when exposure is great, while for mesothelioma the period is said to be as great as 40 years. W. D. Norwood, MD AMA Council on Occupational Health JAMA Aug 17, 1970 * Vol 213, No 7 The Environment 1249 r--