Diesel exhaust and coal mine dust: lung cancer risk in occupational settings

Our plain-English summary of Diesel exhaust and coal mine dust: lung cancer risk in occupational settings, by B. Hoffmann, K.H. Jöckel (Annals of the New York Academy of Sciences, 2006).

The study

• Authors: B. Hoffmann, K.H. Jöckel
• Journal: Annals of the New York Academy of Sciences
• Published: 2006;1076:253-65
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Conflicting evidence on the carcinogenicity of diesel exhaust (DE) and coal mine dust in occupational settings exist. Exposure measurement in most studies is inferred on the basis of job classifications and may lead to misclassification. Confounding behavioral factors (i.e., smoking) and occupational risk factors (exposure to asbestos, arsenic, radon) need to be considered. We evaluated the epidemiological evidence and current findings of the carcinogenicity of DE and coal mine dust in occupational settings. Pertaining literature was identified through Medline search and recent review articles. Strengths and limitations of recent approaches are discussed. Many epidemiological studies have addressed the question of carcinogenicity in workers exposed to DE, and most showed a low-to-medium increase in the risk of bronchial carcinoma. The pooled relative risk (RR) estimates lie between 1.33 and 1.47, and a consistent rise in risk across various job categories and study designs point to a causal relationship. Data on the carcinogenicity of coal mine dust are less consistent and the potential for confounding by unmeasured risk factors (arsenic, radon, DE) are higher. While silica as one of its components has been evaluated as carcinogenic, there is inadequate evidence for the carcinogenicity of pure coal dust according to the International Agency for Research on Cancer (IARC). There is sufficient evidence for a causal relationship between DE and lung cancer in occupational settings. The evidence for coal mine dust is less convincing, but individual studies show an increase in risk of lung cancer in exposed workers.

In plain English

This article reviewed published research, found through Medline and recent reviews, on whether workplace exposure to diesel exhaust and coal mine dust raises lung cancer risk. Asbestos appeared only as an exposure studies had to account for. Two earlier meta-analyses of diesel exhaust had found pooled relative risks of 1.33 (95% confidence interval 1.24 to 1.44) and 1.47 (1.29 to 1.67). In a pooled German case–control study, the odds ratio for all diesel-exposed jobs fell from 1.91 to 1.43 (95% CI 1.23 to 1.67) after adjusting for smoking and asbestos. A U.S. railroad study found a relative risk of 1.40 (95% CI 1.30 to 1.51) for jobs operating diesel-powered trains. Most cohort studies of coal miners showed death rates below national rates, which the authors linked to the healthy worker effect. The coal case–control studies all showed an elevated risk. The authors concluded that recent studies had strengthened the causal evidence for diesel exhaust, but that the responsible part of the coal mine dust mixture could not be identified. They noted that almost all studies lacked personal exposure measurements.

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 epidemiological studies, with supporting animal and laboratory evidence. The literature was identified through a Medline search and recent review articles. No new data were collected.
• Who was studied: Published studies of workers exposed to diesel exhaust (such as railroad workers, truck and bus drivers, garage workers and heavy equipment operators) and of coal miners, including six case–control studies on coal mining or coal dust exposure
• Exposure: Occupational diesel exhaust and coal mine dust. Smoking, asbestos and other particles or carcinogens were discussed as confounding exposures that studies needed to adjust for.
• Main results:
  • Two earlier meta-analyses of diesel exhaust and lung cancer found pooled relative risks of 1.33 (95% CI: 1.24–1.44; Bhatia et al.) and 1.47 (95% CI: 1.29–1.67; Lipsett and Campleman)
  • In a pooled analysis of two German case–control studies, the crude odds ratio for lung cancer for all diesel-exposed jobs combined was 1.91. After adjustment for smoking and asbestos exposure it fell to 1.43 (95% CI: 1.23–1.67).
  • In the same German pooled study, heavy equipment operators showed the highest increase in risk (OR 2.31)
  • The most recent analysis of U.S. railroad workers found a relative risk of 1.40 (95% CI: 1.30–1.51) for workers in jobs associated with operating trains powered by diesel engines
  • In most cohort mortality studies of coal miners, death rates (including from lung cancer) were lower than national rates. The authors attributed this to the healthy worker effect.
  • All six case–control studies on coal mining or coal dust exposure showed an elevated lung cancer risk, and three indicated a positive exposure–response relationship
• The authors' conclusion: The authors concluded that recent studies had strengthened the causal evidence linking occupational diesel exhaust exposure to lung cancer. For coal mine dust, they concluded that an increased risk was consistently seen in case–control studies, but the responsible constituent could not be determined.
• Limitations the authors state:
  • The authors noted that almost all of the reviewed studies lacked personal exposure measurements
  • The authors noted that cohort studies often do not adjust for confounding exposures such as smoking and asbestos
  • For coal mine dust, the authors stated that it is not possible to determine which constituent of the mixture is responsible

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, Confounding, Carcinoma, Relative Risk, Carcinogenic, IARC.

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