Lung cancer risk in male workers occupationally exposed to diesel motor emissions in Germany

Our plain-English summary of Lung cancer risk in male workers occupationally exposed to diesel motor emissions in Germany, by I. Brüske-Hohlfeld, M. Möhner, W. Ahrens, et al (American Journal of Industrial Medicine, 1999).

The study

• Authors: I. Brüske-Hohlfeld, M. Möhner, W. Ahrens, H. Pohlabeln, J. Heinrich, M. Kreuzer, K.H. Jöckel, H.E. Wichmann
• Journal: American Journal of Industrial Medicine
• Published: 1999;36(4):405-14
• Cited by: 58 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Although in several epidemiological studies exposure to diesel motor emissions (DME) shows an elevated lung cancer risk, it is still controversial whether DME is a human carcinogen.

Methods: In a pooled analysis of two case-control studies on lung cancer in Germany a total of 3498 male cases with histologically or cytologically ascertained lung cancer and 3541 male population controls were included. Information about lifelong occupational and smoking history was obtained by questionnaire. Drivers of lorries, buses, taxies, diesel locomotives and forklift trucks, bulldozers, graders, excavators, and tractors, were considered as exposed to DME and their cumulative exposure was estimated. All odds ratios were adjusted for smoking and asbestos exposure.

Results: The evaluation of lung cancer risk for all jobs with DME-exposure combined showed an odds ratio of OR=1.43 (95%-CI: 1.23-1.67). Most pronounced was the increase in lung cancer risk in heavy equipment operators (OR=2. 31 95%-CI: 1.44-3.70). The risk of tractor drivers increased with length of employment and reached statistical significance for exposures longer than 30 years (OR=6.81, 95%-CI: 1.17-39.51). The group of professional drivers (e.g., trucks, buses, and taxies), showed an increased risk only in West Germany (OR=1.44, 95%-CI: 1. 18-1.76), but not in East Germany (OR=0.83, 95%-CI: 0.60-1.14). DME-exposure in other traffic related jobs (e.g., diesel engine locomotive drivers, switchmen, forklift operators) was associated with an odds ratio of OR=1.53 (95%-CI: 1.04-2.24).

Conclusions: The study provides further evidence that occupational exposure to diesel motor emissions is associated with an increased lung cancer risk.

Copyright 1999 Wiley-Liss, Inc.

In plain English

The authors pooled two German case-control studies of lung cancer. They analyzed 3,498 men with lung cancer and 3,541 male population controls, interviewed about lifelong jobs and smoking. Men with at least six months in four job groups (professional drivers, other traffic-related jobs, heavy equipment operators, full-time tractor drivers) were classed as diesel-exposed using written task descriptions; professional drivers were all counted except those doing mainly desk work. Results were adjusted for smoking and asbestos exposure. Compared with never-exposed men, the 1,146 exposed men had an odds ratio of 1.43 (95% confidence interval 1.23 to 1.67). Heavy equipment operators had the highest odds ratio, 2.31 (1.44 to 3.70). Professional drivers had a raised odds ratio in West Germany (1.44, 1.18 to 1.76) but not East Germany (0.83, 0.60 to 1.14). Tractor drivers overall showed no clear increase (1.29, 0.78 to 2.14), but those exposed over 30 years had 6.81 (1.17 to 39.51). The authors noted exposure was judged only from job information. They concluded that the study adds evidence that occupational diesel exhaust exposure is associated with increased lung cancer 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: Pooled analysis of two population-based case-control studies
• Who was studied: 3,498 men with cytologically or histologically confirmed lung cancer and 3,541 male population controls. They came from the BIPS study (1988 to 1993; Bremen and surroundings, Frankfurt/Main area) and the GSF radon study (1990 to 1996; regions of West and East Germany).
• Exposure: Diesel motor emissions. Men had to have worked at least 6 months in one of four job groups: professional drivers (trucks, buses, taxis); other traffic-related jobs (switchmen, diesel locomotive drivers, diesel forklift drivers); operators of bulldozers, graders and excavators; and full-time farm tractor drivers. Written job task descriptions were used to decide who was actually exposed; for example, electrical forklift drivers were excluded. All professional drivers were considered exposed, through surrounding traffic as well as their own vehicle, except those with mainly desk work in a shipping department. Asbestos exposure was assessed with job-specific questionnaires and used for adjustment.
• Main results:
  • 1,146 men (716 cases, 430 controls) had ever been occupationally exposed to diesel motor emissions.
  • Ever-exposed men were compared with never-exposed men. For all diesel-exposed jobs combined, the odds ratio adjusted for smoking and asbestos was 1.43 (95% CI 1.23 to 1.67). The crude odds ratio was 1.91 and the smoking-adjusted odds ratio was 1.46.
  • By duration of exposure, the fully adjusted odds ratio rose up to the more-than-10-to-20-years category (1.84, 95% CI 1.34 to 2.52) and decreased after that.
  • Across all diesel-exposed jobs, the fully adjusted odds ratio was 1.60 (95% CI 1.33 to 1.92) in West Germany and 1.07 (95% CI 0.81 to 1.42) in East Germany.
  • Professional drivers (534 cases, 337 controls) had an adjusted odds ratio of 1.25 (95% CI 1.05 to 1.47) overall. The figure was 1.44 (95% CI 1.18 to 1.76) in West Germany and 0.83 (95% CI 0.60 to 1.14) in East Germany.
  • Men in other traffic-related jobs (99 cases, 60 controls) had an adjusted odds ratio of 1.53 (95% CI 1.04 to 2.24). The increase became statistically significant with 10 or more years of exposure.
  • Heavy equipment operators (81 cases, 32 controls) had the highest adjusted odds ratio, 2.31 (95% CI 1.44 to 3.70).
  • Tractor drivers (52 cases, 36 controls) showed no increased overall risk after adjustment (odds ratio 1.29, 95% CI 0.78 to 2.14). Risk rose with duration of employment, with an odds ratio of 6.81 (95% CI 1.17 to 39.51) for more than 30 years of exposure.
  • Additionally adjusting for social status lowered the odds ratio for ever-exposed men from 1.43 to 1.26.
• The authors' conclusion: The authors concluded that the study provides further evidence that occupational exposure to diesel motor emissions is associated with an increased lung cancer risk.
• Limitations the authors state:
  • Exposure assessment was limited: exposure was defined by working in a job where diesel engines were used. The authors said this likely causes non-differential misclassification, biasing odds ratios toward one.
  • The only quantitative measure of exposure was cumulative time spent in a diesel-exposed job.
  • Controls in the GSF study had a low response rate (41 percent), and people from the lower social class were underrepresented among GSF controls.
  • The authors noted that adjusting for socio-economic status may lead to over-adjustment and artificially reduce occupational risk estimates.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Meta-Analysis, Cumulative Exposure, Odds Ratio, Asbestos Exposure, Statistical Significance, Occupational Exposure.

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