With the improvement of working conditions in asbestos industries and the recognition that asbestos exposure is widespread, the asbestos controversy has shifted in the 1980s to the general environment. To assess lung cancer risks due to environmental asbestos exposure, risks in past asbestos workers have been extrapolated linearly to exposures 100,000 times smaller than historical occupational levels. Despite their enormous health and economic impact, such risk assessments have not been validated to this day. / This is the first study to compare the risk of lung cancer in a population non-occupationally exposed to asbestos with those predicted by the U.S. Environmental Protection Agency's (EPA) exposure-effect model. The study was carried out among the female population of Quebec's two chrysotile-mining agglomerations, where asbestos pollution has been visible commonly from 1882 to 1975. Six small exposure studies were conducted. These studies were synthesized by a panel of 5 international experts to estimate the historical levels of asbestos in the three main mining towns as well as the asbestos pollution brought home on the clothes of workers. These estimates were combined with a survey of lifetime neighbourhood and household exposures of female residents to assess the cumulative exposure of the females aged 30+ who resided in the mining agglomerations between 1970 and 1989. The average was 35 continuous fiber-years/mL. On the basis of the equivalent occupational exposure, the EPA model predicted a lung cancer relative risk of 2.47. Mortality of the female population of the asbestos-mining agglomerations aged 30+ was compared over the 1970-1989 period to that of 60 comparable agglomerations of Quebec. The lung cancer SMR was 0.99 (95%CI: 0.78-1.26) and the SPMR was 1.10 (95%CI: 0.88-1.38). Although the EPA model predicted 105 excess lung cancer deaths based on SMRs, none were observed in this population; based on SPMRs, an excess of 95 excess deaths was predicted, but only 6.5 observed. The EPA risk assessment on asbestos greatly overestimated the risk of lung cancer attributed to environmental asbestos exposure in this population.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41994 |
| Date | January 1996 |
| Creators | Camus, Michel, 1951- |
| Contributors | Siemiatycki, Jack (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Epidemiology and Biostatistics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001558986, proquestno: NQ29901, Theses scanned by UMI/ProQuest. |
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