Lung cancer and mesothelioma among male automobile mechanics: a review

Our plain-English summary of Lung cancer and mesothelioma among male automobile mechanics: a review, by F. Laden, M.J. Stampfer, A.M. Walker (Reviews on Environmental Health, 2004).

The study

• Authors: F. Laden, M.J. Stampfer, A.M. Walker
• Journal: Reviews on Environmental Health
• Published: 2004;19(1):39-61
• Type of article: Review
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Extensive, overt asbestos exposure clearly causes lung cancer and mesothelioma. Elevated cancer risk has also been documented for short term or low levels of asbestos exposure. Automobile mechanics are potentially exposed to asbestos through brake repair work. Few studies have specifically examined the risk of lung cancer and mesothelioma associated with exposure to asbestos in brakes, but automobile mechanics are included in many studies of occupation and cancer.

Methods: We critically reviewed all epidemiologic studies of lung cancer and mesothelioma risk among male automobile mechanics identified through a broadly based Medline search and scrutiny of references in primary and review articles. We discuss the studies grouped by study design and control for smoking, the major risk factor for lung cancer.

Results/conclusions: We reviewed all individual analytical studies meeting our criteria, plus all available case series and case reports. When examined in aggregate, the evidence did not support an increase in risk of either lung cancer or mesothelioma among male automobile mechanics occupationally exposed to asbestos from brake repair.

In plain English

This article was a review, not a new study. The authors searched Medline (1966 through August 2003) and reference lists for epidemiologic studies of lung cancer and mesothelioma among male automobile mechanics, who may be exposed to asbestos through brake repair. Of five studies of automobile and bus mechanics, only one (Jarvholm and Brisman) found a statistically significant lung cancer excess (SMR 1.70), and none of the five adjusted for smoking. In a smoking-adjusted New Jersey case-control study, the odds ratio was 1.4 (95% CI 0.84-2.30), not statistically significant. Studies without smoking information had mixed results; one in Washington State reported a significantly elevated proportional mortality ratio (PMR) of 1.15. None of 11 mesothelioma studies reported a significant association with work as an automobile mechanic, though they found more insulation workers among cases. A meta-analysis by Wong gave a combined relative risk of 0.90 (95% CI 0.66-1.23). The authors concluded that, taken together, the evidence indicated no increase in risk of either disease in this group. They noted weak exposure assessment and rare smoking control in many studies.

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: Review of published epidemiologic studies, case series and case reports
• Who was studied: Studies of men identified through Medline searches covering 1966 through August 2003, plus references in primary and review articles. The review was limited to studies of men.
• Exposure: Work as an automobile (or bus) mechanic, with potential low-level exposure to asbestos from repairing friction materials such as brakes. The authors state that brake linings and brake shoes contain chrysotile asbestos.
• Main results:
  • Among five studies focused on automobile and bus mechanics, only the Jarvholm and Brisman study found a significant association with lung cancer (SMR 1.70, p less than 0.01).
  • None of those five mechanic-focused studies adjusted for smoking.
  • In the Gustavsson et al. bus garage study, lung cancer incidence was elevated but not statistically significantly (SIR 1.61; 95% CI 0.94-2.57), with no dose-response association with asbestos exposure.
  • In the smoking-controlled study of U.S. veterans by Blair and colleagues, there was no lung cancer excess for automobile mechanics (SMR 1.03).
  • In the Swedish study by Carstensen and colleagues, after indirect smoking adjustment, the SIR for mechanics and repairmen taken together was 1.07 (95% CI 0.92-1.22).
  • Cohort studies relying only on registries or death certificates had no smoking information, and their results were mixed.
  • In Washington State death surveys (1999 publication), the PMR for lung cancer deaths among automobile mechanics was statistically significantly elevated at 1.15.
  • In the New Jersey case-control study by Schoenberg and colleagues, the smoking-adjusted odds ratio for automobile mechanics was 1.4 (95% CI 0.84-2.30), not statistically significant.
  • The NOMS study reported 18 mesotheliomas among white automobile mechanics (PMR 0.77) and 2 among black mechanics (PMR 1.54).
  • The authors identified 11 studies of mesothelioma and occupation; none reported a significant association with work as an automobile mechanic.
  • Those mesothelioma studies found more insulation workers and others in jobs with overt asbestos exposure among the cases.
  • A 2001 meta-analysis by Wong combining studies of mesothelioma among automobile mechanics gave a combined relative risk of 0.90 (95% CI 0.66-1.23).
  • In a fiber analysis by Roggli and colleagues of 1445 mesothelioma cases, including 51 with some automobile mechanic or brake work, those researchers concluded the tumors were unlikely to be due to exposure to automotive brakes (chrysotile fibers).
• The authors' conclusion: The authors concluded that, examined in aggregate, the studies indicated no increase in risk of either lung cancer or mesothelioma among automobile mechanics.
• Limitations the authors state:
  • In many studies, occupation was based on a one-time report of usual or last occupation.
  • Few studies assessed actual exposure to friction products such as brakes.
  • Exposure misclassification may tend to make relative risk estimates smaller.
  • Studies that did not consider the duration and timing of employment, given the long latency of these diseases, may have biased relative risks.
  • Smoking, the key risk factor for lung cancer, was seldom assessed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Auto mechanics and brake work, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, Asbestos Exposure.

Related studies

• Cumulative asbestos exposure for US automobile mechanics involved in brake repair (circa 1950s-2000) — B.L. Finley, R.O. Richter, et al. (2007)
• Chrysotile asbestos exposure associated with removal of automobile exhaust systems (ca. 1945-1975) by mechanics: results of a simulation study — D.J. Paustenbach, A.K. Madl, et al. (2006)
• Asbestos-related diseases in automobile mechanics — J. Ameille, N. Rosenberg, et al. (2012)
• Mesothelioma in vehicle mechanics: is the risk different for Australians? — M.A. Kelsh, V.A. Craven, et al. (2007)
• A study of airborne chrysotile concentrations associated with handling, unpacking, and repacking boxes of automobile clutch discs — G.C. Jiang, A.K. Madl, et al. (2008)
• Asbestos exposure among transmission mechanics in automotive repair shops — N. Salazar, M.F. Cely-García, et al. (2015)

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