Occupational and non-occupational attributable risk of asbestos exposure for malignant pleural mesothelioma

Our plain-English summary of Occupational and non-occupational attributable risk of asbestos exposure for malignant pleural mesothelioma, by A. Lacourt, C. Gramond, P. Rolland, et al (Thorax, 2014).

The study

• Authors: A. Lacourt, C. Gramond, P. Rolland, S. Ducamp, S. Audignon, P. Astoul, S. Chamming's, A. Gilg Soit Ilg, M. Rinaldo, C. Raherison, F. Galateau-Salle, E. Imbernon, J.C. Pairon, M. Goldberg, P. Brochard
• Journal: Thorax
• Published: 2014;69(6):532-9
• Cited by: 109 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To estimate the proportion of pleural mesothelioma cases that can be attributed to asbestos exposure in France including non-occupational exposure.

Methods: A population-based case-control study including 437 incident cases and 874 controls was conducted from 1998 to 2002. Occupational and non-occupational asbestos exposure was assessed retrospectively by two expert hygienists. ORs of pleural mesothelioma for asbestos-exposed subjects compared to non-exposed subjects, and population-attributable risk (ARp) of asbestos exposure were estimated using a conditional logistic regression.

Results: A clear dose-response relationship was observed between occupational asbestos exposure and pleural mesothelioma (OR=4.0 (99% CI 1.9 to 8.3) for men exposed at less than 0.1 f/mL-year vs. 67.0 (99% CI 25.6 to 175.1) for men exposed at more than 10 f/mL-year). The occupational asbestos ARp was 83.1% (99% CI 74.5% to 91.7%) for men and 41.7% (99% CI 25.3% to 58.0%) for women. A higher risk of pleural mesothelioma was observed in subjects non-occupationally exposed to asbestos compared to those never exposed. The non-occupational asbestos ARp for these subjects was 20.0% (99% CI -33.5% to 73.5%) in men and 38.7% (99% CI 8.4% to 69.0%) in women. When considering all kinds of asbestos exposure, ARp was 87.3% (99% CI 78.9% to 95.7%) for men and 64.8% (99% CI 45.4% to 84.3%) for women.

Conclusions: Our study suggests that the overall ARp in women is largely driven by non-occupational asbestos exposure arguing for the strong impact of such exposure in pleural mesothelioma occurrence. Considering the difficulty in assessing domestic or environmental asbestos exposure, this could explain the observed difference in ARp between men and women.

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In plain English

This French case-control study, 1998 to 2002, compared 437 pleural mesothelioma patients (362 men, 75 women) with 874 matched controls. Blinded experts rated work and non-work exposure from questionnaires. Bracketed ranges after odds ratios and percentages are 99% confidence intervals. In men, risk rose with cumulative work exposure: odds ratio 4.0 (1.9 to 8.3) below 0.1 f/mL-years and 67.0 (25.6 to 175.1) above 10 f/mL-years, versus never-exposed men. Work exposure accounted for 83.1% (74.5% to 91.7%) of male and 41.7% (25.3% to 58.0%) of female cases. Among people never exposed at work, non-work exposure accounted for 38.7% (8.4% to 69.0%) of female cases and, based on 9 cases, 20.0% (minus 33.5% to 73.5%) of male cases. All asbestos exposure accounted for 87.3% (78.9% to 95.7%) of male and 64.8% (45.4% to 84.3%) of female cases; sensitivity analyses under stricter definitions gave 22.0% to 52.0% for women. The authors noted domestic and environmental exposure was poorly measured, open to recall bias. They concluded about 35% of female cases remained unattributed to asbestos, perhaps from underestimated non-occupational exposure or other factors.

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: Population-based case-control study with individually matched controls, analysed by conditional logistic regression. Population-attributable risks were estimated.
• Who was studied: 437 incident cases of pleural mesothelioma (362 men, 75 women) identified through the French National Mesothelioma Surveillance Program (PNSM), 1998 to 2002, and alive at interview. 874 general-population controls (724 men, 150 women) were matched for sex, age (within 5 years) and district of residence. Participation rates were 61.1% for cases and 20.8% for controls.
• Exposure: Lifetime asbestos exposure was assessed retrospectively by two experts (an industrial hygienist and an occupational physician) from questionnaires.
• Occupational exposure: each job held 6 months or more was rated for probability, frequency, intensity and route of exposure, and combined into a cumulative exposure index in f/mL-years.
• Non-occupational exposure:
  • domestic: do-it-yourself work such as home improvements and brake and clutch repairs;
  • para-occupational: asbestos-contaminated clothes of relatives;
  • environmental: self-reported living near an industrial source of asbestos.
• Exposures less than 20 years before diagnosis were not counted.
• Fiber type was not assessed for individual subjects.
• Main results:
  • Men: the odds ratio for pleural mesothelioma, compared with never-exposed men, was 4.0 (99% CI 1.9 to 8.3) at less than 0.1 f/mL-years of occupational exposure and 67.0 (99% CI 25.6 to 175.1) above 10 f/mL-years.
  • Men: a dose-response relationship was observed for all occupational exposure parameters.
  • Women ever occupationally exposed: odds ratio 12.0 (99% CI 3.5 to 41.7) compared with never-exposed women.
  • Occupational asbestos population-attributable risk: 83.1% (99% CI 74.5% to 91.7%) in men and 41.7% (25.3% to 58.0%) in women. The text labels the women's interval 95%, while Table 4 and the abstract give 99%.
  • Subjects never occupationally exposed (9 male cases and 18 controls; 36 female cases and 72 controls), non-occupationally exposed versus never exposed: odds ratio 2.4 (99% CI 0.2 to 26.7) in men and 4.3 (99% CI 1.2 to 15.1) in women.
  • Non-occupational asbestos population-attributable risk among subjects never occupationally exposed: 20.0% (99% CI −33.5% to 73.5%) in men and 38.7% (99% CI 8.4% to 69.0%) in women.
  • All asbestos exposure (occupational and/or non-occupational) versus none: odds ratio 13.0 (99% CI 6.2 to 27.5) in men and 8.0 (99% CI 2.9 to 21.8) in women.
  • Overall asbestos population-attributable risk: 87.3% (99% CI 78.9% to 95.7%) in men and 64.8% (99% CI 45.4% to 84.3%) in women.
  • Men, four sensitivity analyses that reclassified possible and/or very-low-intensity exposure as unexposed: the overall attributable risk was 68.6%, 85.9%, 86.0% and 68.6%.
  • Women, the same four sensitivity analyses: the overall attributable risk was 26.7% (99% CI 12.0 to 41.3), 47.4% (99% CI 30.0 to 65.0), 52.0% (99% CI 34.1 to 69.8) and 22.0% (99% CI 8.0 to 36.0), compared with the main estimate of 64.8%.
• The authors' conclusion: The authors concluded that, after accounting for non-occupational exposure, approximately 35% of female cases were still not attributable to asbestos exposure. They suggested the overall attributable risk could be underestimated because domestic and environmental exposures are hard to identify, and that other factors are also possible explanations.
• Limitations the authors state:
  • The major limitation was the retrospective assessment of exposure.
  • The assessment of domestic and environmental exposure had poor reliability and was highly subject to recall bias.
  • Environmental exposure was based only on self-reported proximity to an industrial source. This may have underestimated such exposure and therefore the non-occupational and overall attributable risks.
  • Recall bias could instead have overestimated the non-occupational and overall attributable risks.
  • More blue-collar workers were among refusing controls, possibly leading to underestimation of occupational exposure among controls.
  • Only cases alive at interview were included. Cases who died before interview seemed less occupationally exposed.
  • Results may not be generalisable to other countries, such as developing countries.

Topics

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

Medical terms in this study, explained in our Lexicon: Attributable Risk, Asbestos Exposure, Pleural Mesothelioma, Non-Occupational Exposure, Case-Control Study, Dose-response relationship.

Related studies

• Attributable risk in men in two French case-control studies on mesothelioma and asbestos — A. Lacourt, P. Rolland, et al. (2010)
• Occupations and industries in France at high risk for pleural mesothelioma: A population-based case-control study (1998-2002) — P. Rolland, C. Gramond, et al. (2010)
• Temporal patterns of occupational asbestos exposure and risk of pleural mesothelioma — A. Lacourt, K. Leffondré, et al. (2012)
• Co-exposure to refractory ceramic fibres and asbestos and risk of pleural mesothelioma — A. Lacourt, M. Rinaldo, et al. (2014)
• Pleural mesothelioma and occupational coexposure to asbestos, mineral wool, and silica — A. Lacourt, C. Gramond, et al. (2013)
• Compensation of pleural mesothelioma in France: data from the French National Mesothelioma Surveillance Programme — S. Chamming's, B. Clin, et al. (2013)

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