Document 3e1dwJnm2b4VQjoqyxKz33LMx

4 /4. .u. .m iIII US OF tSnVSTMM. llliAl.TII /.( *(; C.WCEK and cxjxwurc Co asbestos lias been evident was lint |wis-iUr in trace 1.1.1 iif these for since the report in 1935 by Lynch and Smith (lie whole |ieriud. but 5771 of lltc remaining of a case in which lung cancer and asbes- 5958 were found to Ire still living in 1935 tosis were both present. As additional cases or later. Of the 187 known dead, cancer in which die two diseases coexisted were uf the lung was considered in have Uyii rc]>ortcd, a eausal association ap)tears to reasonably proved in 9 and to tic strongly liave been gradually aecejitcil by many suggested ih 3. authors, although some' workers considered The members of the cohort were studio! the correlation to be inconclusive. The pres with respect to age, length of employment, ent study was undertaken in an effort to de termine whether a causal relationship did. in fact, exist between vx|isure to asbestos a weighted average of their exposure, and their smoking habits. It was found that 4673 were smokers within the definition of and cancer of the lung. that term as used in this study. Thirty-four Since most earlier studies had Itcen 1 per cent of die cohort were more than 45 limited to enumerating the lung cancers venrs of age, amt thirty per cent had been found in certain selected samples, such as employed for longer than 20 years. Thirty cases coming to autopsy or death certificates per cent had a weighted expnrure which in which asbestosis was mentioned, it was placed them in the category of highest ex apparent that they could not fulfill the re posure. quirements of an epidemiological and sta tistical approach to the problem. The present study was, therefore, designed to meet the requirements of this method. After a preliminary survey to explore the availability of reliable information, data were gathered an workers in the asbestos mines in Quebec, based on their medical records. A cohort was defined as a group of aslieslos miners liaviug at least live years of exposure and who were in ihe industry in 1950. Data relative to their characteristics The mortality rate for lung enneur, computed on the basis of nine "proved'' deaths among the cohort was 25.3 per 100.000. When the three "suspected" cases were added, the "tolal" rate for the cohort rose to 33.8. The im|xirtaiice_of the suspected but unproved cases in determining the,e ` rates has been reiterated because it is likelv llmt such cases would ura lie included in the statistics for the gener.il imputation and because they Influence the results so mark edly. were collected and .their status at the cud of a six-year period of observation was de termined. In the case of those who had died, an exhaustive search of death certif icates and insurance records was carried out in order to determine as nearly as possible According to the findings in this .study, the mortality rate from lung cancer does not appear to increase with length of exjiosure or with degree of cxjmsurc. a fact which presents strong evidence against the carcinogenicity of asbestos. the exact cause of death. Mortality rates Comparison of the experience among the from lung cancer for the general population asbestos miners with tliat of various seg of the Province of Quebec and its various ments of the unexposed, comparable popu counties and for the Dominion of Canada, lation shows that the observed number of as well as the United States were calculated deaths aiming the miners is not significantly from statistics collected in the appropriate greater than the exacted number. The rate places. Comjorisons of the rates obtained for proved cases among the asbestos miners for asbestos workers and for the other popu (25.3 tier 100.0001 compares well with Uie lation groups were made according to ac rate of 22.5 |icr 100.000 for the rest of the cepted statistical methods. Province, ami 20.8 per 100.000 for aduli Records were obtained on fiOOl persons males throughout the Dniniuinn of Cniunlj. who fulfilled tile criteria uf the cohort. It It also compares satisfactorily with rates 6$0 I "id. I', /line, 19JJ nf 37.2. 25.3. and 2 sources for aduli m Filially, in this n: would appear (ha; i III |KT.MIIS CX|HIM-. worse with res|vt of the iuicX]Hiscd The counties sc producing areas, i: uiost of the asbesi most identical inert: tight counties wide Province, and are I remainder of the P" than the rate for M Since -I9-JJ3 there which the dingnosi* the lung may be c proved. Approxima were associated with died in the rveugniz least one-third had posure (Category 1 On the basis oi . complete and relnbh conclude that the : Province of Quebec icamlv higher death iliaii dn comparable : ;'Opul.lll<m. Furthcnnore, the cancer in the areas c ids opeialiiiiis is cem: widely scattered thru OucUc and is Imviized areas within lh<. REFEZ l. Abfch. Escobar, i Review of 200 Casts, .f 20:375-J7< l Sept) 19ic 2 Allen. M. L.: Bm. poaipil wiilt Pncv^Hu Cases. ,1. IihIhsi. f U X Cartier, 1*.; A C% yi Asi*csii>ts, ArA r jv49. 4. AmlcrMui.. C. S. a ;iul CarcitM4iin of the f (March) PM.H. 5. !Ullrr; K. \V.: A Aclmschr. *5:407~hV * Jrt/itn--Trutm .-3 fr-'--sjrB S-