Mesothelioma in vehicle mechanics: is the risk different for Australians?

Our plain-English summary of Mesothelioma in vehicle mechanics: is the risk different for Australians?, by M.A. Kelsh, V.A. Craven, M.J. Teta, et al (Occupational Medicine, 2007).

The study

• Authors: M.A. Kelsh, V.A. Craven, M.J. Teta, F.S. Mowat, M. Goodman
• Journal: Occupational Medicine
• Published: 2007;57(8):581-9
• Type of article: Review
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The question of whether vehicle mechanics have an increased risk of mesothelioma has important public health implications. Calculations of relative risk using case reports from the Australian Mesothelioma Registry (AMR) indicate increased risks; however, this contrasts with the results of 19 epidemiologic studies that have found no association.

Aim: To evaluate potential explanations for the discrepancy of findings from epidemiologic studies and AMR reports.

Methods: We evaluated three hypotheses as possible explanations for the inconsistency between the AMR-based calculations and the findings from published epidemiologic studies: (i) differences in exposure characteristics of Australian vehicle mechanics versus vehicle mechanics in North America and Europe, (ii) limitations of the AMR data and (iii) errors in the risk calculations based on AMR data. We reviewed available exposure information specific to Australian vehicle mechanics and AMR data, obtained from the Australian National Occupational Health and Safety Commission, for this evaluation.

Results: We did not identify differences in workplace exposures, processes or fibre type among Australian vehicle mechanics compared to vehicle mechanics in other countries. Our analysis of primary AMR data identified several errors in exposure classification and in the assumptions used to calculate relative risk.

Conclusions: Discrepancies between epidemiologic studies and AMR-based calculations cannot be explained by differences in exposure. These discrepancies are most likely attributable to inadequate occupational information and classification in the AMR from 1986 forward and to erroneous assumptions used to derive relative risk estimates for mesothelioma among Australian vehicle mechanics.

In plain English

This study asked why calculations from the Australian Mesothelioma Registry (AMR) suggested higher mesothelioma risk for vehicle mechanics, when 19 epidemiologic studies had found no association. They reviewed exposure information on Australian vehicle mechanics. They examined registry records for 78 mesothelioma cases recorded for 1986 to 2001 under brake linings made or repaired. They did not identify differences in workplace exposures, processes or fibre type versus mechanics elsewhere. Chrysotile was used in Australian brakes; the authors judged an unconfirmed report of crocidolite use in Western Australian brakes to be unlikely. Of the 78 cases, 48 could possibly be motor mechanics and 38 were definite motor mechanics. Of these 38, 18 had no other recorded asbestos exposure, and 15 of those 18 had only one or two jobs recorded. A World Trade Organization calculation had used 58 such cases; the authors also questioned its population and background-rate assumptions. The authors concluded the discrepancy most likely reflected inadequate registry occupational information and erroneous risk assumptions. They stated their analysis did not estimate actual risk and that earlier exposure data were lacking.

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 exposure literature combined with a record review of Australian Mesothelioma Registry case forms, testing three possible explanations for a discrepancy in findings
• Who was studied: 78 mesothelioma cases in the Australian Mesothelioma Registry category of brake linings made or repaired, 1986 to 2001 (59 with exposure only to brakes, 19 with other asbestos exposures), obtained as de-identified records from Australia's National Occupational Health and Safety Commission
• Exposure: Asbestos exposure during brake work by vehicle mechanics. Chrysotile asbestos was used in brake disc pads, brake linings and brake blocks. An unconfirmed report of crocidolite use in Western Australian brakes was judged unlikely by the authors.
• Main results:
  • The authors did not identify differences in workplace exposures, processes or fibre type between Australian vehicle mechanics and vehicle mechanics in other countries
  • The authors found no published data confirming an earlier statement that crocidolite was used in brakes in Western Australia, and considered such use unlikely
  • Of the 78 registry cases, 48 could be considered possible motor mechanics. The remaining 30 were not professional vehicle mechanics, worked near mechanics, worked in brake manufacturing, or were wives of mechanics.
  • Of the 48 possible mechanics, 38 were definite motor mechanics, and 18 of those 38 had no other recorded asbestos exposure
  • Of the 18 definite mechanics with no other recorded exposure, 15 had only one or two jobs recorded
  • Of the 38 definite motor mechanics, 20 had other occupational asbestos exposures
  • A World Trade Organization panellist had counted 58 cases of brake mechanics with no other asbestos exposure; the authors found that no more than 18 potentially fit that definition
  • The authors stated that the World Trade Organization calculation assumed a 1:2 ratio of current to ever motor mechanics, whereas a US estimate was 1:5
  • The authors stated that the background mesothelioma rate used in the World Trade Organization calculation was likely too low for Australia
• The authors' conclusion: The authors concluded that the discrepancy cannot be explained by differences in exposure. They judged it most likely due to inadequate occupational information and classification in the registry from 1986 onward, and to erroneous assumptions used to derive relative risk estimates for Australian vehicle mechanics.
• Limitations the authors state:
  • Exposure data were lacking for earlier time periods
  • The analysis was not an attempt to estimate the actual mesothelioma risk among vehicle mechanics
  • There was no formal data collection, and there were no data to enumerate the population at risk
  • Classifying registry cases was difficult because the records contained little information

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Relative Risk.

Related studies

• Lung function and exposure to asbestos among vehicle mechanics — M. Dahlqvist, R. Alexandersson, et al. (1992)
• Exposure to asbestos during brake maintenance of automotive vehicles by different methods — T. Kauppinen, K. Korhonen (1987)
• Cumulative asbestos exposure for US automobile mechanics involved in brake repair (circa 1950s-2000) — B.L. Finley, R.O. Richter, et al. (2007)
• Mesothelioma and lung cancer among motor vehicle mechanics: a meta-analysis — M. Goodman, M.J. Teta, et al. (2004)
• Response to Kay Teschke. Re: Mesothelioma among Motor Vehicle Mechanics: An Updated Review and Meta-analysis — D.H. Garabrant, D.D. Alexander, et al. (2016)
• Mesothelioma among Motor Vehicle Mechanics: An Updated Review and Meta-analysis — D.H. Garabrant, D.D. Alexander, et al. (2016)

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