Occupational exposure to asbestos and man-made vitreous fibers, and risk of lung cancer: evidence from two case-control studies in Montreal, Canada

Our plain-English summary of Occupational exposure to asbestos and man-made vitreous fibers, and risk of lung cancer: evidence from two case-control studies in Montreal, Canada, by J. Pintos, M.E. Parent, M.C. Rousseau, et al (Journal of Occupational and Environmental Medicine, 2008).

The study

• Authors: J. Pintos, M.E. Parent, M.C. Rousseau, B.W. Case, J. Siemiatycki
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2008;50(11):1273-81
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To examine the effects of occupational asbestos and man-made vitreous fibers (MMVF) on the risk of lung cancer in two population-based case-control studies entailing exposure at lower levels than in historic cohort studies.

Methodology: Study I (1979 to 1986) comprised 857 cases and 1066 population and cancer controls. Study II (1996 to 2001) comprised 858 cases and 1295 population controls. A detailed job history was obtained to evaluate lifetime occupational exposure to 294 agents, including asbestos and MMVF.

Results: We found increased risks for substantial exposure to asbestos (odds ratio = 1.78; 95% confidence interval: 0.94 to 3.36). The corresponding odds ratio for substantial exposure to MMVF was 1.10 (95% confidence interval: 0.37 to 3.22).

Discussion: Low and moderate levels of exposure to asbestos, as encountered in this population, were associated with some excess risk of lung cancer. Results for MMVF were inconclusive.

In plain English

This article reported on two population-based case-control studies of lung cancer in the Montreal area, one run from 1979 to 1986 and one from 1996 to 2001. Results were given for men only. Experts reviewed each man's lifetime job history to judge his exposure to two things: asbestos (all fiber types combined, with all exposed men assumed to have had chrysotile) and man-made vitreous fibers (MMVF), meaning glass fibers and mineral wool. "Substantial" exposure meant medium or high concentrations, for more than 5% of the workweek, for 5 years or more. With both studies pooled, substantial asbestos exposure was associated with lung cancer (odds ratio 1.90; 95% confidence interval 1.11 to 3.24). For substantial exposure lasting more than 20 years, the odds ratio was 2.98 (1.28 to 6.96). In the later study alone, no odds ratio reached statistical significance. Results for MMVF were imprecise and gave no evidence either for or against an association. The authors concluded that asbestos exposure across many jobs, at levels lower than in historical cohorts, was associated with a small increase in lung cancer risk. They noted that exposure could not be measured in fiber concentrations.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Two population-based case-control studies, analysed separately and pooled
• Who was studied: Men with lung cancer and controls in the Montreal area, Canada. Study I (1979 to 1986) had 857 lung cancer cases. Its controls were 533 population controls and 1349 patients with other cancers; a combined control group of the 533 population controls plus a random 533 of the cancer controls was used. Study II (1996 to 2001) identified 858 eligible male cases and 1024 eligible male controls, of whom 86% and 70% took part (Table 1 lists 741 cases and 899 controls). Women were excluded from the analyses because their exposure was rare.
• Exposure: Occupational exposure judged by chemists and industrial hygienists from detailed job histories, for two groups of fibers: asbestos (all fiber types combined; all exposed men assumed exposed to chrysotile, with a subset judged also likely exposed to amphiboles) and MMVF (glass fibers and mineral wool fibers combined). Substantial exposure meant medium or high concentration, more than 5% of the workweek, for 5 years or more.
• Main results:
  • Study I: substantial asbestos exposure was associated with increased lung cancer risk (OR 2.25; 95% CI 1.09 to 4.65); there was no such association for MMVF.
  • Study I: for substantial asbestos exposure lasting more than 20 years, the OR was 3.90 (95% CI 1.24 to 12.25).
  • Study II: ORs were slightly lower than in Study I, and none reached statistical significance.
  • Pooled studies: substantial asbestos exposure was associated with lung cancer (OR 1.90; 95% CI 1.11 to 3.24).
  • Pooled studies: for substantial asbestos exposure lasting more than 20 years, the OR was 2.98 (95% CI 1.28 to 6.96).
  • Men judged exposed to amphibole asbestos had OR estimates similar to those for any type of asbestos. The authors interpreted this with caution because fiber type was hard to identify.
  • Pooled analysis separating men exposed to asbestos only, MMVF only, or both: substantial exposure gave borderline significant ORs of around 1.70 (Table 5 shows 1.78, 95% CI 0.94 to 3.36, for substantial exposure to asbestos only).
  • Results for MMVF were imprecise and gave no evidence either for or against a positive association.
  • The combined effect of smoking and asbestos was less than multiplicative, but the confidence limits were wide enough to fit both additive and multiplicative models.
• The authors' conclusion: The authors concluded that asbestos exposure across a wide variety of occupations, at levels lower than in historical cohorts, was associated with a small increase in lung cancer risk.
• Limitations the authors state:
  • Exposure was estimated after the fact, so some men were misclassified. The authors judged this likely to be the same for cases and controls, which would weaken any true association.
  • The authors had limited ability to separate men exposed to chrysotile from men exposed to amphibole fibers.
  • Exposure levels could not be expressed as actual fiber concentrations.
  • Limited statistical power prevented analyses by histological type of cancer, precise estimates of interaction with smoking, and analyses of individual MMVF subtypes.
  • Because the exposure eras of the two studies overlapped, comparing them could not show how risks changed over time.
  • There were very few lung cancer cases among non-smokers, so the smoking-asbestos estimates were imprecise.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Vitreous, Lung Cancer, Odds Ratio, confidence interval.

Related studies

• Risk of mesothelioma and occupational exposure to asbestos and man-made vitreous fibers: evidence from two case-control studies in Montreal, Canada — J. Pintos, M.E. Parent, et al. (2009)
• Lung cancer and exposure to man-made vitreous fibers: results from a pooled case-control study in Germany — H. Pohlabeln, K.H. Jöckel, et al. (2000)
• Occupational exposure to asbestos and man-made vitreous fibres and risk of lung cancer: a multicentre case-control study in Europe — R. Carel, A.C. Olsson, et al. (2007)
• Man-made vitreous fibers and risk of respiratory system cancer: a review of the epidemiologic evidence — I.M. Lee, C.H. Hennekens, et al. (1995)
• Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study — J.L. Marchand, D. Luce, et al. (2000)
• Asbestos and man-made vitreous fibers as risk factors for diffuse malignant mesothelioma: results from a German hospital-based case-control study — K. Rödelsperger, K.H. Jöckel, et al. (2001)

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