A case-control study of asphalt and tar exposure and lung cancer in minorities

Our plain-English summary of A case-control study of asphalt and tar exposure and lung cancer in minorities, by M.D. McClean, K.T. Kelsey, J.D. Sison, et al (American Journal of Industrial Medicine, 2011).

The study

• Authors: M.D. McClean, K.T. Kelsey, J.D. Sison, C.P. Quesenberry, M.R. Wrensch, J.K. Wiencke
• Journal: American Journal of Industrial Medicine
• Published: 2011;54(11):811-8
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: Considerable controversy surrounds the carcinogenic potential of asphalt and tar. Since minority individuals may have had relatively high historical exposures, we investigated asphalt and tar exposure and lung cancer risk among African Americans and Latino Americans.

Methods: We conducted a case-control study of lung cancer among African Americans and Latino Americans in the San Francisco Bay area (422 cases, 894 controls). A questionnaire was used to obtain detailed work histories and exposure information. Self-reported exposure to asphalt and tar as well as other factors (e.g., smoking, automobile exhaust, and asbestos) were evaluated as predictors of lung cancer risk. Potential effect modification by cytochrome P450 (CYP) 1A1 was also explored.

Results: Self-reported duration of exposure to asphalt and tar was associated with a statistically significant excess risk of lung cancer in the overall population (OR: 1.11, 95% CI: 1.01-1.22), evaluating risk per year of exposure. Years of exposure to automobile exhaust (OR: 1.02, 95% CI: 1.00-1.05) and asbestos (OR: 1.04, 95% CI: 1.02-1.06) were also associated with statistically significant elevations in risk. In Latino Americans, the lung cancer risks associated with polycyclic aromatic hydrocarbon-related exposures were consistently higher in the CYP1A1 wild-type subjects as compared to the variant genotype subjects, and the interaction was statistically significant for smoking and the CYP1A1 M2 polymorphism (P-value(interaction) = 0.02).

Conclusions: These data are consistent with the literature suggesting that exposure to asphalt and tar may increase risk of lung cancer. However, it was not possible to separate the effects and asphalt and tar in this study.

Copyright © 2011 Wiley Periodicals, Inc.

In plain English

This case–control study looked at lung cancer among African Americans and Latino Americans in the San Francisco Bay Area. It compared 422 people with lung cancer diagnosed between September 1998 and March 2003 with 894 people without lung cancer. In interviews, participants described each job they had held and whether it involved "asphalt and tar" (asked about as one item), automobile exhaust, or asbestos. Ever having asphalt and tar exposure, reported by 32 cases and 48 controls, was not significantly linked to lung cancer overall (odds ratio 1.2, 95% CI 0.7 to 2.1), but it was among Latino Americans (2.9, 1.0 to 8.5). Overall, each year of asphalt and tar exposure was associated with higher odds of lung cancer (1.11, 1.01 to 1.22). Asbestos, used partly to check the questionnaire, was associated with lung cancer in ever-exposed people (2.2, 1.6 to 3.2) and per year of exposure (1.04, 1.02 to 1.06). The authors concluded that the results fit earlier research suggesting asphalt and tar may raise lung cancer risk. They could not separate asphalt from tar, and they noted possible recall bias.

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: case–control study using logistic regression
• Who was studied: 422 lung cancer cases and 894 controls, all African American or Latino American residents of the San Francisco Bay Area. Cases were newly diagnosed with primary lung cancer between September 1998 and March 2003. There were 276 cases and 580 controls among African Americans, and 146 cases and 314 controls among Latinos.
• Exposure: Self-reported occupational exposure, from lifetime work histories, to 'Asphalt & Tar' as a single item. Automobile exhaust and asbestos were also assessed as co-exposures. Exposure was measured as ever/never and as years of exposure. No asbestos fiber type is specified.
• Main results:
  • 80 subjects (32 cases, 48 controls) reported asphalt and tar exposure. In the overall population, ever exposure was not significantly associated with lung cancer (OR 1.2, 95% CI 0.7 to 2.1, per Table II).
  • Among Latino Americans, ever exposure to asphalt and tar was associated with a statistically significant increase in risk (OR 2.9, 95% CI 1.0 to 8.5). This was not the case among African Americans (OR 0.9, 95% CI 0.5 to 1.8, per Table II).
  • In the overall population, each year of asphalt and tar exposure was associated with a statistically significant elevation in lung cancer risk (OR 1.11, 95% CI 1.01 to 1.22).
  • When analyzed by group, the per-year estimates were similar but not statistically significant: African Americans OR 1.10 (95% CI 0.99 to 1.22), Latino Americans OR 1.16 (95% CI 0.94 to 1.44), per Table III.
  • In the overall population, ever exposure to asbestos was associated with a statistically significant increase in lung cancer risk (OR 2.2, 95% CI 1.6 to 3.2). The finding was similar among African Americans and Latinos. The authors used it as a check on the validity of the self-reported histories.
  • In the overall population, each year of asbestos exposure was associated with a statistically significant increase in lung cancer risk (OR 1.04, 95% CI 1.02 to 1.06). Each year of automobile exhaust exposure also was (OR 1.02, 95% CI 1.00 to 1.05).
  • Ever exposure to automobile exhaust gave slightly elevated risk estimates that were not statistically significant (overall OR 1.5, 95% CI 0.9 to 2.5, per Table II).
  • In Latino Americans, the CYP1A1 M2 gene variant modified the effect of smoking (OR 1.06 vs 1.03 per pack-year; p for interaction 0.02). The corresponding differences for asphalt and tar were in the same direction but not statistically significant. Similar evidence was not seen in African Americans.
• The authors' conclusion: The authors concluded that the results are consistent with the literature suggesting that exposure to asphalt and tar may be associated with an increased risk of lung cancer. They added that the effects of asphalt and tar could not be separated in this study.
• Limitations the authors state:
  • The questionnaire asked about asphalt and tar as a single substance, so risk from asphalt could not be separated from risk from tar.
  • Information on how often and how intensely people were exposed was unavailable. The authors said this likely caused non-differential misclassification, which leads to underestimation of the true risk.
  • Job descriptions were too limited to assess lung cancer risk by industry.
  • Recall bias could not be ruled out, since people with lung cancer may have been more likely than controls to report exposures.

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: Case-Control Study, Lung Cancer, Carcinogenic, P-Value.

Related studies

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• Estimating exposures in the asphalt industry for an international epidemiological cohort study of cancer risk — I. Burstyn, P. Boffetta, et al. (2003)
• Simulation tests to assess occupational exposure to airborne asbestos from artificially weathered asphalt-based roofing products — P. Sheehan, F. Mowat, et al. (2010)
• A review of changes in composition of hot mix asphalt in the United States — D.J. Mundt, K.M. Marano, et al. (2009)
• Parental occupational exposure and risk of childhood central nervous system tumors: a pooled analysis of case-control studies from Germany, France, and the UK — C. Huoi, A. Olsson, et al. (2014)
• Occupational asbestos exposure as a risk factor for laryngeal carcinoma in a population-based case-control study from Germany — H. Ramroth, W. Ahrens, et al. (2011)

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