Pleural mesothelioma and occupational coexposure to asbestos, mineral wool, and silica

Our plain-English summary of Pleural mesothelioma and occupational coexposure to asbestos, mineral wool, and silica, by A. Lacourt, C. Gramond, S. Audignon, et al (American Journal of Respiratory and Critical Care Medicine, 2013).

The study

• Authors: A. Lacourt, C. Gramond, S. Audignon, S. Ducamp, J. Févotte, A.G. Soit Ilg, M. Goldberg, E. Imbernon, P. Brochard
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 2013;187(9):977-82
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rationale: Occupational coexposure to asbestos and other fibers or particles could modify the carcinogenicity of asbestos with regard to pleural mesothelioma.

Objectives: To estimate associations between pleural mesothelioma and occupational mineral wool and silica exposure and to study the impact of occupational coexposure on the risk of pleural mesothelioma.

Methods: A total of 1,199 male cases and 2,379 control subjects were included in a French pooled case-control study. Complete job histories were collected, and occupational exposure to asbestos, mineral wool (MW), and silica were assessed by three French job exposure matrices. Unconditional logistic regression models adjusted for age, birth date, and occupational asbestos exposure were used to estimate odds ratios (OR) and 95% confidence intervals (CIs).

Measurements And Main Results: A significant association between mesothelioma and MW exposure was observed after adjustment for occupational asbestos exposure. OR for subjects exposed to less than 0.01 fibers·ml(-1)·yr(-1) was 1.6 (95% CI, 1.2-2.1) and increased to 2.5 (95% CI, 1.8-3.4) for subjects exposed to more than 0.32 fibers·ml(-1)·yr(-1). All ORs for silica exposure were around the null. Coexposure to either asbestos and MW or asbestos and silica seemed to increase the risk of pleural mesothelioma. ORs were 17.6 (95% CI, 11.8-26.2) and 9.8 (95% CI, 4.2-23.2) for subjects exposed to both asbestos and MW and for subjects exposed to both asbestos and silica, respectively, compared with 4.3 (95% CI, 1.9-9.8) for occupational asbestos exposure alone.

Conclusions: Our results are in favor of an increased risk of pleural mesothelioma for subjects exposed to both asbestos and MW or asbestos and silica.

In plain English

This French case-control study examined whether work exposure to mineral wool or crystalline silica, alone or combined with asbestos, was linked to pleural mesothelioma in men. It pooled 1,199 male cases, identified between 1987 and 2006, with 2,379 male control subjects drawn from population samples. Job histories were collected by interview, and exposures were estimated with job exposure matrices. After adjustment for asbestos and silica, men ever exposed to mineral wool had an odds ratio of 1.8 (95% CI 1.5–2.3) compared with unexposed men. Odds ratios for silica were not significant and around the null. The comparison group for the next figures was men exposed to none of the three substances. Among men whose cumulative asbestos exposure index was above 10 fibers/ml-years, the odds ratio was 4.3 (1.9–9.8) with asbestos alone, 17.6 (11.8–26.2) with asbestos and mineral wool, and 9.8 (4.2–23.2) with asbestos and silica. The authors noted that the three exposures were highly correlated and that job exposure matrices misclassify exposure. They concluded that mineral wool seemed associated with pleural mesothelioma and that coexposure seemed to raise risk compared with asbestos alone.

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: Pooled case-control study (cases from an earlier hospital-based case-control study and from the French National Mesothelioma Surveillance Program; controls from population-based samples)
• Who was studied: 1,199 male pleural mesothelioma cases and 2,379 male control subjects in France. Cases came from a case-control study run January 1987 to December 1996 and from the national surveillance program, January 1998 to December 2006. Controls were frequency matched on sex and 5-year birth group. All subjects were alive and interviewed.
• Exposure: Occupational exposure to asbestos (fiber type not specified), mineral wool and crystalline silica, estimated from complete job histories using three French job exposure matrices. Exposure was expressed as highest probability of exposure, total duration in years, and a cumulative index of exposure (fibers/ml-years for asbestos and mineral wool; mg/m3-years for silica).
• Main results:
  • Men ever exposed to mineral wool, compared with never exposed: OR 1.8 (95% CI, 1.5–2.3). The model was adjusted for asbestos and silica cumulative exposure.
  • Mineral wool dose-response, compared with never exposed: men with a cumulative index below 0.01 fibers/ml-years had OR 1.6 (95% CI, 1.2–2.1). Men above 0.32 fibers/ml-years had OR 2.5 (95% CI, 1.8–3.4).
  • For silica exposure, adjusted for asbestos and mineral wool, all ORs were not significant and around the null (ever vs never exposed OR 1.0, 95% CI 0.8–1.2).
  • Subgroup analysis, compared with men exposed to none of the three substances:
• asbestos only: OR 2.5 (95% CI 2.0–3.3)
• asbestos and mineral wool but not silica: OR 8.4 (6.4–10.9)
• asbestos and silica but not mineral wool: OR 4.5 (3.0–6.6)
• all three: OR 8.3 (6.3–10.9)
  • Among men with asbestos cumulative exposure above 10 fibers/ml-years, compared with men exposed to none of the three substances:
• asbestos only: OR 4.3 (95% CI, 1.9–9.8)
• asbestos and mineral wool: OR 17.6 (95% CI, 11.8–26.2)
• asbestos and silica: OR 9.8 (95% CI, 4.2–23.2)
• all three: OR 10.0 (95% CI, 7.2–14.0)
  • Men exposed to silica only (11 cases, 21 controls) had OR 4.6 (95% CI, 1.9–11.2) versus men with none of the exposures. The authors judged this more likely due to exposure misclassification and random error.
  • In the adjusted analysis, no significant interactions were observed between asbestos and mineral wool cumulative exposures, or between asbestos and silica cumulative exposures.
• The authors' conclusion: The authors concluded that occupational mineral wool exposure seemed to be associated with pleural mesothelioma. They also concluded that coexposure to asbestos, mineral wool and/or silica seemed to increase the risk compared with asbestos exposure only, which led them to hypothesize that coexposure particles may modify the carcinogenicity of asbestos.
• Limitations the authors state:
  • Asbestos, mineral wool and silica exposures were highly correlated. Only 11 subjects were exposed to mineral wool only and 32 to silica only, which can inflate standard errors and lead to wrong inference.
  • Job exposure matrices assess exposure retrospectively at the job level. They create many nondifferential misclassifications, and these may have been correlated across the three matrices, biasing results toward or away from the null.
  • Residual confounding by asbestos in the mineral wool analyses cannot be excluded.
  • The silica results were hardly interpretable, and the study was not sufficient to argue a possible effect of silica on pleural mesothelioma.
  • The representativeness of the control subjects, who were pooled from two different sources, is less certain than that of the cases.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Case-Control Study, Occupational Exposure, Asbestos Exposure, Odds Ratio, confidence interval, Mesothelioma.

Related studies

• Risk of lung cancer associated with occupational exposure to mineral wools: updating knowledge from a french population-based case-control study, the ICARE study — F. Guida, S. Paget-Bailly, et al. (2013)
• Reply: No indication that mineral wool causes mesothelioma — A. Lacourt (2013)
• No indication that mineral wool causes mesothelioma — J.P. Bonde (2013)
• Mortality among a cohort of US man-made mineral fiber workers: 1985 follow-up — G.M. Marsh, P.E. Enterline, et al. (1990)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• 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)

Browse more research in American Journal of Respiratory and Critical Care Medicine, or return to medical research.