Mesothelioma among brake mechanics: an expanded analysis of a case-control study

Our plain-English summary of Mesothelioma among brake mechanics: an expanded analysis of a case-control study, by P.A. Hessel, M.J. Teta, M. Goodman, et al (Risk Analysis, 2004).

The study

• Authors: P.A. Hessel, M.J. Teta, M. Goodman, E. Lau
• Journal: Risk Analysis
• Published: 2004;24(3):547-52
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The U.S. Environmental Protection Agency has begun discussions to consider its assessment of asbestos toxicity related to mineral form and fiber size. Brake workers are typically exposed to short chrysotile fibers. To explore the mesothelioma risk among brake workers, considering other occupational exposures to asbestos, data from a study that was published previously were obtained and the analysis was extended. The National Cancer Institute provided data from a case-control study of mesothelioma. Because many participants with a history of brake work also had employment in other asbestos-related occupations, mesothelioma cases and controls were compared for a history of brake work, controlling for employment in eight occupations with potential asbestos exposure. A stratified analysis was also performed excluding those with any of the eight occupations. Possible interactions between brake work and other occupational exposures related to risk of mesothelioma were also examined. The odds ratio (OR) for employment in brake installation or repair was 0.71 (95% CI: 0.30-1.60) when controlled for insulation or shipbuilding. When a history of employment in any of the eight occupations with potential asbestos exposure was controlled, the OR was 0.82 (95% CI: 0.36-1.80). ORs did not increase with increasing duration of brake work. Exclusion of those with any of the eight exposures resulted in an OR of 0.62 (95% CI: 0.01-4.71) for occupational brake work. There was no evidence of an interaction between brake work and other occupational exposures. These latter analyses were based on small numbers of exposed cases. The results are consistent with the existing literature indicating that brake work does not increase the risk of mesothelioma and adds to the evidence that fiber type and size are important determinants of mesothelioma risk.

In plain English

This study reanalyzed data from an earlier U.S. case-control study of mesothelioma by Spirtas and colleagues. Cases were diagnosed from 1975 to 1980 through two cancer registries and 39 Veterans Administration hospitals. Work and asbestos exposure histories came from interviews with next of kin. The main analyses included white males with reliable work histories. The authors compared cases and controls for brake work while accounting for eight other activities with potential asbestos exposure. Shipbuilding and insulation were associated with mesothelioma. For brake work done as a job, the odds ratio was 0.71 (95% CI 0.30 to 1.60) after accounting for shipbuilding or insulation and 0.82 (0.36 to 1.80) after accounting for all eight activities. Odds ratios did not rise with longer brake work. Among people with none of the eight activities, the odds ratio for job-related brake work was 0.62 (0.01 to 4.71); only one case and nine controls in that group had done such work. The authors concluded that the results are consistent with literature indicating brake work does not increase mesothelioma risk. They noted that brake worker numbers were small.

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: Reanalysis of data from a previously published case-control study of mesothelioma (Spirtas et al.), in which work and exposure histories came from interviews with next of kin; unmatched analysis using logistic regression controlling for age
• Who was studied: Mesothelioma cases diagnosed 1975 to 1980 from the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New York City) and 39 Veterans Administration hospitals, plus deceased controls. Of 203 cases and 521 controls, the main analyses used 147 cases and 358 controls: white males with highly or generally reliable work histories and a nonmissing answer on brake work.
• Exposure: Brake lining installation or repair, as reported by next of kin. It was classed as occupational (done as part of a job, or both on the job and on own time) or nonoccupational (on own time only). Eight other activities with potential asbestos exposure were also considered, including shipbuilding/shipyard work and insulation. Fiber exposure was not measured in this study.
• Main results:
  • In the model including all terms, occupational brake work had an odds ratio of 0.74 (95% CI 0.35 to 1.54) for mesothelioma, and nonoccupational brake work had 0.83 (95% CI 0.43 to 1.59).
  • In the same model, shipbuilding had an odds ratio of 6.04 (95% CI 3.74 to 9.75) and insulation 3.38 (95% CI 2.20 to 5.17).
  • For occupational brake work controlled for shipbuilding or insulation, the odds ratio was 0.71 (95% CI 0.30 to 1.60).
  • For occupational brake work controlled for any of the eight activities with potential asbestos exposure, the odds ratio was 0.82 (95% CI 0.36 to 1.80).
  • The analysis by duration of brake work showed no suggestion of increasing mesothelioma risk with longer employment in brake work.
  • Among participants with none of the eight activities, the odds ratio for occupational brake work was 0.62 (95% CI 0.01 to 4.71). It was based on one exposed case and nine exposed controls, meaning those who had done occupational brake work.
  • Analyses of interactions showed no patterns suggesting that brake work enhanced the risk associated with other asbestos exposures. These data were not presented.
  • Age-adjusted odds ratios for insulators were 4.14 (95% CI 2.55 to 6.77) without a history of brake work and 1.74 (95% CI 0.69 to 4.46) with a history of brake work (occupational or nonoccupational).
  • Age-adjusted odds ratios for shipbuilders were 5.16 (95% CI 2.94 to 9.23) without a history of brake work and 4.36 (95% CI 1.36 to 14.8) with a history of brake work.
• The authors' conclusion: The authors concluded that the results are consistent with existing literature indicating that brake work does not increase the risk of mesothelioma. They wrote that the results add to evidence that fiber type and size are important determinants of mesothelioma risk.
• Limitations the authors state:
  • The numbers of brake workers were relatively small, especially in the analyses that excluded people with other potential asbestos exposures.
  • In the stratified analysis, only one case and nine controls with occupational brake work had none of the other jobs involving asbestos exposure.
  • The original study excluded from the control group people who died of cancer and respiratory disease. If those diseases were linked to asbestos exposure in this population, risk estimates for occupations with asbestos exposure may have been overestimated.
  • The article notes that the original study's authors recognized that next of kin may have failed to recall all opportunities for asbestos exposure, especially in the distant past.

Topics

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

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

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• Re: Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — D.J. Paustenbach, B.L. Finley, et al. (2006)
• Cumulative asbestos exposure for US automobile mechanics involved in brake repair (circa 1950s-2000) — B.L. Finley, R.O. Richter, et al. (2007)
• Brake mechanics, asbestos, and disease risk — M. Huncharek (1990)

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