Insulation, asbestos, smoking habits, and lung cancer cell types

Our plain-English summary of Insulation, asbestos, smoking habits, and lung cancer cell types, by J.E. Muscat, S.D. Stellman, E.L. Wynder (American Journal of Industrial Medicine, 1995).

The study

• Authors: J.E. Muscat, S.D. Stellman, E.L. Wynder
• Journal: American Journal of Industrial Medicine
• Published: 1995;27(2):257-69
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The association between occupational exposure to asbestos and histological type of lung cancer was analyzed in a multicenter hospital-based case-control study (2,871 male cases and 5,240 male controls) conducted from 1981-1991. Twenty-two percent of cases and 18% of controls were employed in asbestos-related occupations for at least 1 year. Most of these asbestos jobs were in the construction field. The odds ratio (OR) among current smokers was 1.0 [95% confidence intervals (CI) 0.9 to 1.3]; for ex-smokers, the OR was 1.4 (95% CI 1.1 to 1.6). In contrast, 10% of cases and 5% of controls self-reported that they were chronically exposed to asbestos for at least 1 year. Self-reported asbestos exposure was significantly related to all lung cancer cell types among smokers and ex-smokers, although a trend in the ORs with duration of self-reported exposure was not found for current smokers. Among 48 cases and 52 controls reporting distinct exposure to building insulation, the OR was 2.2 (95% CI 1.2 to 4.3) for current smokers, and 1.8 (95% CI 0.9 to 3.6) for ex-smokers, compared to subjects who were not exposed to building insulation and asbestos. A nonsignificant association with self-reported exposure to asbestos was observed for a small number of never smokers (eight of 83 nonsmoking cases, OR = 2.0, 95% CI 0.9 to 4.6). When examining these results and their causal implications, possible misclassification and reporting biases need to be considered.

In plain English

This hospital-based case-control study compared 2,871 men with lung cancer and 5,240 male hospital controls interviewed 1981 to 1991. Exposure measures were jobs likely to involve asbestos (mostly construction trades and mechanics), self-reported asbestos dust at work, and, from 1986, self-reported building insulation exposure. 22% of cases and 18% of controls held asbestos-related jobs. The odds ratio (OR) was 1.0 (95% CI 0.9 to 1.3) for current smokers and 1.3 (1.1 to 1.6) for ex-smokers. Self-reported asbestos dust exposure was linked to higher odds of lung cancer (all cell types combined): ORs 1.5 (1.1 to 2.1) and 2.5 (1.5 to 4.1) for current smokers in the earlier and later periods, and 1.9 (1.3 to 2.8) and 2.2 (1.4 to 3.5) for ex-smokers. Current smokers showed no significant trend with years exposed. For building insulation, ORs were 2.2 (1.2 to 4.3) in current smokers and 1.8 (0.9 to 3.6) in ex-smokers. Never smokers' OR for self-reported exposure, based on eight cases, was 2.0 (0.9 to 4.3), not statistically significant. The authors said recall bias and misclassification need consideration.

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: Multicenter hospital-based case-control study, part of a larger case-control study of tobacco-related cancers
• Who was studied: 2,871 men with newly diagnosed lung cancer and 5,240 male hospital controls with conditions unrelated to tobacco, interviewed 1981 to 1991 in nine hospitals in New York, Michigan, Illinois and Pennsylvania. Cases with tumors arising from the pleura were excluded.
• Exposure: Employment for at least 1 year in occupations judged likely to involve asbestos (mainly construction trades, carpenters, plumbers/pipe fitters, electricians, welders, building maintenance, automobile and other mechanics). Also self-reported exposure to asbestos dust on the job for at least 8 hours a week for 1 or more years, and, in the later questionnaire, self-reported exposure to building insulation. Fiber types were not recorded.
• Main results:
  • 22% of cases and 18% of controls worked in asbestos-related occupations. Among current smokers there was no association with lung cancer (OR 1.0, 95% CI 0.9 to 1.3).
  • Among former smokers, asbestos-related employment showed a small, significant increase (OR 1.3, 95% CI 1.1 to 1.6). The authors attributed this largely to 19 cases and 9 controls who were sheet metal workers (OR 4.5, CI 2.1 to 9.3) and 14 cases and 7 controls who were equipment mechanics (OR 2.3, CI 1.1 to 4.6).
  • Over 10% of cases and 5% of controls self-reported occupational asbestos dust exposure. For current smokers the OR for all lung cancer cell types was 1.5 (95% CI 1.1 to 2.1) in the earlier period and 2.5 (95% CI 1.5 to 4.1) in the later period. The trend with duration of self-reported exposure was not significant.
  • For ex-smokers, self-reported asbestos exposure gave an OR for all lung cell types of 1.9 (95% CI 1.3 to 2.8) for 1981 to 1985 and 2.2 (95% CI 1.4 to 3.5) for 1986 to 1991.
  • Self-reported asbestos exposure was associated with an increased risk for all lung cancer cell types, both central and peripheral tumors.
  • This applies to men who both worked in asbestos occupations and reported asbestos exposure (1986 to 1990 only), compared with men who had neither. The OR for all lung cell types was 2.1 (95% CI 1.1 to 3.9) for current smokers and 2.4 (95% CI 1.4 to 4.2) for ex-smokers.
  • 48 of 1,121 cases (4%) and 52 of 2,093 controls (2%) interviewed after 1985 reported distinct exposure to building insulation for at least 1 year. Compared with men exposed to neither insulation nor asbestos, the OR was 2.2 (95% CI 1.2 to 4.3) for current smokers and 1.8 (95% CI 0.9 to 3.6) for ex-smokers.
  • Among never smokers, self-reported asbestos exposure was associated with an elevated but not statistically significant OR of 2.0 (95% CI 0.9 to 4.3), based on eight exposed nonsmoking cases.
• The authors' conclusion: The authors concluded that their self-reported insulation and asbestos exposure data suggest asbestos also increases lung cancer risk among smokers in jobs such as general construction, welding and automobile mechanics. They added that possible misclassification and reporting biases need to be considered when judging causal implications.
• Limitations the authors state:
  • Self-reported asbestos exposure may be affected by recall or 'wish' bias: cases may prefer to attribute their illness to an unavoidable exposure rather than to smoking.
  • The authors calculated a hypothetical case. If 40 of the 336 cases in asbestos jobs had reported exposure that never occurred, case and control exposure percentages would be equal. Jobs such as general construction and carpentry would then not appear to increase smokers' risk.
  • The study had no information on exposure intensity, fiber type, fiber shape or exposure regimen. Job titles alone may be an inadequate measure of exposure.
  • The significant findings for a few specific job titles might be chance results of multiple comparisons.
  • There was only one shipyard worker and no asbestos miners or millers among the subjects.
  • Some asbestos-related jobs involve other lung carcinogens, such as smoke for firefighters and nickel and chromium for welders.
  • The never-smoker result rests on small numbers. It could be substantially biased if even a few smokers were misclassified as nonsmokers, and other carcinogens may have caused these cancers.

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: Habit, Lung Cancer, Occupational Exposure, Case-Control Study, Odds Ratio, confidence interval, Asbestos Exposure, Recall Bias.

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• Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking — R. Lilis, I.J. Selikoff, et al. (1986)
• Association of cigarette smoking and asbestos exposure with location and histology of lung cancer — B.W. Lee, J.C. Wain, et al. (1998)
• Alcohol, smoking, and occupational factors in cancer of the larynx: a case-control study — W. Ahrens, K.H. Jöckel, et al. (1991)
• The joint effect of asbestos exposure, tobacco smoking and alcohol drinking on laryngeal cancer risk: evidence from the French population-based case-control study, ICARE — G. Menvielle, A. Fayossé, et al. (2016)

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