Mortality of auto mechanics. A ten-year follow-up

Our plain-English summary of Mortality of auto mechanics. A ten-year follow-up, by E.S. Hansen (Scandinavian Journal of Work, Environment & Health, 1989).

The study

• Author: E.S. Hansen
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1989;15(1):43-6
• Cited by: 55 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002565).

Abstract

This study was set up to investigate whether work in car repair workshops is associated with an increased risk of ischemic heart disease and specific malignant neoplasms. For this purpose, a cohort of auto mechanics has been followed through 10 years with regard to cause-specific mortality. Comparisons were made with another cohort of skilled male workers who were not exposed to asbestos or petrochemical substances. The auto mechanics' mortality was increased for ischemic heart disease [standardized mortality ratio (SMR) 121, 95% confidence interval (95% CI) 102-145], other cardiovascular diseases (SMR 112, 95% CI 82-150), cancer (SMR 115, 95% CI 97-136), other diseases (SMR 119, 95% CI 94-149), and external causes (SMR 131, 95% CI 113-153). For specific cancer sites, increases were seen for pancreatic cancer, urinary cancer outside the bladder, and pleural mesothelioma.

In plain English

In this Danish cohort study, the author used the 9 November 1970 census to identify 21,800 employed auto mechanics and 51,747 men in other skilled trades, mainly carpenters and electricians, all aged 15 to 74. The author then compared their deaths through 8 November 1980. The comparison trades were described as free from work exposure to asbestos, petrochemical products and paint pigments. Auto mechanics had 21% more deaths than expected. Standardized mortality ratios (SMR; 100 means no excess) were raised for ischemic heart disease (121, 95% CI 102 to 145), external causes (131, 95% CI 113 to 153) and pancreatic cancer (17 deaths, 219, 95% CI 128 to 351). The author cautioned that the comparison group may have been too small for reliable statistics on this rare cancer. Among the auto mechanics there was a single death from pleural mesothelioma, and lung cancer was not increased. The author concluded that this single case indicated that asbestos exposure during brake-lining replacement had not been negligible. The author called the study rather insensitive and said cancer sites other than lung and pancreas had too few deaths to state or rule out an increased risk.

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: Historical cohort study comparing cause-specific mortality of an exposed group (auto mechanics) with an unexposed group of other skilled workers over ten years of follow-up
• Who was studied: Danish men aged 15 to 74 who were skilled workers or apprentices and were employed on the day of the 9 November 1970 national census. There were 21,800 auto mechanics and 51,747 comparison workers (carpenters 45%, electricians 32%, instrument makers 13%, with the rest of the list cut off in the text). They were followed until 8 November 1980, death or emigration. Auto mechanics contributed 192 300 person-years and the comparison group 481 642.
• Exposure: Work as an auto mechanic or as a mechanic at a car-repair workshop, defined by job title on census day. The comparison group was skilled men in other trades described as free from occupational exposure to petrochemical products, asbestos and paint pigments. The asbestos fiber type is not specified.
• Main results:
  • Auto mechanics, all causes: deaths exceeded the expected number by 21% (583 observed deaths, SMR 121, 95% CI 112-131)
  • Auto mechanics, ischemic heart disease: SMR 121, 95% CI 102-145 (132 observed deaths)
  • Auto mechanics, all cancer: SMR 115, 95% CI 97-136 (148 observed deaths). Other diseases: SMR 119, 95% CI 94-149.
  • Auto mechanics, other cardiovascular diseases: SMR 112, 95% CI 82-150
  • Auto mechanics, external causes: SMR 131, 95% CI 113-153 (175 observed deaths)
  • Auto mechanics, pancreatic cancer: 17 observed deaths versus 7.8 expected, SMR 219, 95% CI 128-351
  • Auto mechanics, pleural mesothelioma: a single observed death. The scrambled table does not reliably show an SMR for the pleura row.
  • Auto mechanics, cancer of urinary organs other than the bladder: 8 observed deaths, SMR 174, 95% CI 75-343
  • Auto mechanics, bronchus and lung cancer: not increased (41 observed deaths versus 40.7 expected, SMR 101, 95% CI 72-137)
• The authors' conclusion: The author concluded that the single case of pleural mesothelioma indicated that asbestos exposure during replacement of brake linings had not been negligible. The author considered it remarkable that lung cancer mortality was not increased, and suggested auto mechanics may have smoked less than the comparison group.
• Limitations the authors state:
  • Some members of the comparison group may have been exposed at work to other agents linked to increased mortality, which could have masked a risk for auto mechanics
  • The study was rather insensitive: only occupationally active, and therefore healthy, workers were enrolled, and follow-up was rather short
  • Exposure was defined crudely, by occupation and industry on a single day, which dilutes the exposure contrast; some effects may have gone undetected
  • Life-style habits may have differed between the compared groups
  • For pancreatic cancer, a rare disease, the comparison group may have been too small to assume its death rates were free of random variation, so the statistical evaluation should be viewed with reservations
  • For cancer sites other than lung and pancreatic cancer, the numbers of deaths were too small to state or rule out an increased risk

Topics

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

Medical terms in this study, explained in our Lexicon: Neoplasm, standardized mortality ratio (SMR), confidence interval, Pleural Mesothelioma.

Related studies

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• Warning auto mechanics about asbestos hazards — J. LaDou (2004)
• Abdominal pain and bloating in an auto mechanic — L. Neshatian, M. Halland, et al. (2014)
• Lung function predicts mortality: 10-year follow-up after lung cancer screening among asbestos-exposed workers — T. Vehmas, P. Pallasaho, et al. (2013)
• Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up — D.F. Merlo, M. Bruzzone, et al. (2018)
• French cohort of the uranium processing workers: mortality pattern after 30-year follow-up — I. Guseva Canu, E. Cardis, et al. (2010)

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