Lung function and exposure to asbestos among vehicle mechanics

Our plain-English summary of Lung function and exposure to asbestos among vehicle mechanics, by M. Dahlqvist, R. Alexandersson, G. Hedenstierna (American Journal of Industrial Medicine, 1992).

The study

• Authors: M. Dahlqvist, R. Alexandersson, G. Hedenstierna
• Journal: American Journal of Industrial Medicine
• Published: 1992;22(1):59-68
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Vehicle mechanics (n = 99) exposed to asbestos (annual median value 0.08 f/ml), and local controls (n = 83) not occupationally exposed to asbestos were studied with regard to symptoms and pulmonary function. The inclusion criteria to participate in this study was an age of at least 40 years with no known exposure to lung irritating agents, and for the exposed subjects, more than 15 years occupational exposure to asbestos with at least 20 years from the first exposure. The subjects were studied during identical conditions by means of dynamic and static spirometry, single breath wash-out with nitrogen (N2) and carbon monoxide (CO). The median for cumulative exposure of asbestos during the entire work life among the studied mechanics was 2.3 f*y/ml. The mechanics had reduced transfer factor (TLCO), after adjustment for age, height, and smoking category. A significant dose-response relationship was noted between the cumulative exposure of asbestos and CV%. The findings suggest a slight influence of small airways and alveoli. The evaluation of the prognostic significance of this requires a longitudinal study.

In plain English

This Swedish study compared symptoms and lung function in 99 asbestos-exposed vehicle mechanics with 83 local controls without occupational asbestos exposure. Everyone was at least 40 years old. The mechanics had more than 15 years of exposure, beginning at least 20 years earlier (median 29 years). Their median annual exposure was 0.08 fibers/ml; median cumulative dose was 2.3 fiber-years/ml. Breathlessness on exertion (22% versus 14%, p = .25) and chest oppression (8% versus 2%, p = .18) were slightly more common in the mechanics. Chronic bronchitis affected 2% of both groups. After adjusting for age, height and smoking, the mechanics on average had a lower transfer factor, a measure of lung gas exchange. The authors found no dose-response link between asbestos dose and transfer factor. Higher cumulative asbestos dose correlated with higher CV%, closing volume as a percentage of vital capacity, a small-airways test. After adjusting for age, height, smoking and asbestos, years of diesel exhaust exposure correlated with no lung function measure. The authors judged the differences slight and called for a longitudinal study of their prognostic significance.

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: Comparison of asbestos-exposed vehicle mechanics with unexposed controls, examined at the same time with the same lung function tests, symptom interviews and estimated cumulative exposure
• Who was studied: Mechanics in Sweden drawn from the 'Motor Health' register: 259 eligible, 101 approved, 2 excluded for health disorders, leaving 99. Controls were people whose last job title was white collar worker or bus driver: 315 interviewed, 89 approved, 6 excluded, leaving 83. All were at least 40 years old with no exposure to lung-irritating agents. Mean age was 49 for the exposed and 53 for the unexposed. The study dates are not given.
• Exposure: Occupational asbestos exposure as vehicle mechanics. Inclusion required more than 15 years of exposure, with at least 20 years since first exposure. Median exposure time was 29 years (interquartile range 25-32). Half of the mechanics (50 of 99) had also worked in truck and bus workshops with diesel exhaust exposure.
• Main results:
  • For the exposed mechanics, the annual median asbestos fiber concentration measured by phase contrast light microscope was 0.08 f/ml (interquartile range 0.06-0.11).
  • The median cumulative asbestos dose among the mechanics was 2.3 f*y/ml (interquartile range 1.5-3.6). It was calculated for 95 of the 99 mechanics.
  • Exertional dyspnea was reported by 22% of exposed and 14% of unexposed subjects (p = .25). Chest oppression was reported by 8% of exposed and 2% of unexposed subjects (p = .18).
  • Chronic bronchitis prevalence was 2% in both the exposed and unexposed groups.
  • Exposed mechanics had, on average, a lower transfer factor (TLco) than unexposed subjects after adjustment for age, height, smoking category, packyears and time since stopping smoking.
  • The authors found no dose-response relationship between asbestos exposure and decrease in transfer factor.
  • Among the mechanics, the natural logarithm of cumulative asbestos dose was significantly correlated with CV% (closing volume as a percent of vital capacity) after controlling for age, height, smoking category and diesel exhaust exposure. The figure plotting CV% against cumulative dose reports r = 0.22, p < .05.
  • Among the mechanics, years of exposure to diesel exhaust did not correlate with any lung function variable after controlling for age, height, smoking category and asbestos exposure. The text does not discuss unadjusted correlations for diesel exposure.
• The authors' conclusion: The authors concluded that the differences in lung function between exposed and unexposed subjects were slight and should not markedly limit the mechanics' physical work capacity in daily life. They wrote that the findings suggest a slight influence on the small airways and alveoli.
• Limitations the authors state:
  • Mechanics who had left their jobs because of lung disease were not included, so the authors considered the results in the exposed group underestimated rather than overestimated.
  • Possible confounding exposures in the workplaces included isocyanates, welding fumes and diesel exhaust.
  • Counting by phase contrast light microscope includes only fibers longer than 5 micrometers, which underestimates the total asbestos fiber count in the dust.
  • The prognostic significance of the findings could not be assessed and requires a longitudinal study.

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: Occupational Exposure, Spirometry, Cumulative Exposure, Dose-response relationship, Alveoli.

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• Asbestos-related diseases in automobile mechanics — J. Ameille, N. Rosenberg, et al. (2012)
• Thinking about Occupation-Response and Exposure-Response Relationships: Vehicle Mechanics, Chrysotile, and Mesothelioma — K. Teschke (2016)
• Mesothelioma among car mechanics? — H.J. Woitowitz, K. Rödelsperger (1994)
• Exposure to asbestos during brake maintenance of automotive vehicles by different methods — T. Kauppinen, K. Korhonen (1987)
• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)

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