Occupational exposure to polycyclic aromatic hydrocarbons and lung cancer risk: a multicenter study in Europe

Our plain-English summary of Occupational exposure to polycyclic aromatic hydrocarbons and lung cancer risk: a multicenter study in Europe, by A.C. Olsson, J. Fevotte, T. Fletcher, et al (Occupational and Environmental Medicine, 2010).

The study

• Authors: A.C. Olsson, J. Fevotte, T. Fletcher, A. Cassidy, A. 't Mannetje, D. Zaridze, N. Szeszenia-Dabrowska, P. Rudnai, J. Lissowska, E. Fabianova, D. Mates, V. Bencko, L. Foretova, V. Janout, P. Brennan, P. Boffetta
• Journal: Occupational and Environmental Medicine
• Published: 2010;67(2):98-103
• Cited by: 61 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Lung cancer incidence in Central and Eastern Europe (CEE) is among the highest in the world, and the role of occupational exposures has not been adequately studied in these countries.

Objectives: To investigate the contribution of occupational exposure to polycyclic aromatic hydrocarbons (PAH) to lung cancer in CEE.

Methods: A case-control study was conducted in the Czech Republic, Hungary, Poland, Romania, Russia and Slovakia, as well as the United Kingdom (UK) between 1998 and 2002. Occupational and socio-demographic information was collected through interviews from 2861 newly diagnosed lung cancer cases and 2936 population or hospital controls. Industrial hygiene experts in each country evaluated exposure to 70 occupational agents, whereof 15 mixtures containing PAH. ORs of lung cancer were calculated after adjusting for other occupational exposures and tobacco smoking.

Results: The OR for ever exposure to PAH in the CEE countries was 0.93 (95% CI 0.77 to 1.14). The ORs for the highest category of cumulative exposure, duration of exposure and intensity of exposure were 1.13 (95% CI 0.80 to 1.58), 1.02 (95% CI 0.66 to 1.57) and 1.11 (95% CI 0.60 to 2.05), respectively. The OR for ever PAH exposure in the UK was 1.97 (95% CI 1.16 to 3.35).

Conclusion: Occupational PAH exposure does not appear to substantially contribute to the burden of lung cancer in CEE. The apparently stronger effect observed in the UK may be due to high exposure levels and a joint effect with asbestos.

In plain English

This case-control study examined whether workplace exposure to polycyclic aromatic hydrocarbons (PAH), chemicals formed by incomplete burning, was linked to lung cancer. Between 1998 and 2002, 2852 lung cancer cases and 2923 controls from 16 centres in the Czech Republic, Hungary, Poland, Romania, Russia, Slovakia and the United Kingdom were analysed. Experts who did not know who had cancer judged each person's job exposures. Results were adjusted for smoking and for workplace silica, asbestos and metals. In the Central and Eastern European countries, ever exposure to PAH gave an odds ratio of 0.93 (95% CI 0.77 to 1.14), where 1.0 means no difference. In the UK it was 1.97 (95% CI 1.16 to 3.35). Compared with UK subjects exposed to neither agent, the odds ratios were 4.4 (95% CI 2.17 to 8.94) for both PAH and asbestos, 2.1 (0.99 to 4.27) for PAH only, and 2.3 (1.29 to 4.26) for asbestos only. The authors said their results on a synergistic effect were not statistically significant and need replication. The authors concluded that occupational PAH exposure does not appear to substantially contribute to lung cancer in Central and Eastern Europe.

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: Multicentre case-control study (hospital controls in most centres, population controls in Warsaw and Liverpool) with expert assessment of occupational exposure
• Who was studied: Newly diagnosed lung cancer cases under age 75 and controls from 16 centres in the Czech Republic, Hungary, Poland, Romania, Russia, Slovakia and the UK (Liverpool), 1998 to 2002. 2861 cases and 2936 controls were interviewed. 9 cases and 13 controls lacked complete tobacco data and were excluded, leaving 2852 cases and 2923 controls frequency matched on age and sex.
• Exposure: Occupational PAH exposure, assigned by blinded industrial hygiene experts among 70 agents. It was mostly derived by algorithm from 14 source exposures: soot and fumes from combustion of coal, coke, petroleum oil, wood, asphalt, coal tar and pitch, creosote fumes, diesel emissions, lubricating oil mist, cutting fluids and other mineral oil mist, carbon black dust, and plastics pyrolysis. Exposure was measured as intensity, duration and cumulative exposure (benzo[a]pyrene, mg/m3-years). Asbestos (fiber type not specified), silica and metals were treated as other exposures and adjusted for.
• Main results:
  • Central and Eastern European (CEE) countries: odds ratio for ever PAH exposure 0.93 (95% CI 0.77 to 1.14).
  • CEE countries: odds ratios for the highest category of cumulative exposure 1.13 (95% CI 0.80 to 1.58), of duration (30 or more years) 1.02 (95% CI 0.66 to 1.57), and of intensity 1.11 (95% CI 0.60 to 2.05).
  • UK: odds ratio for ever PAH exposure 1.97 (95% CI 1.16 to 3.35).
  • The difference in PAH effect between the CEE countries and the UK had p equal to 0.002. There was no evidence of heterogeneity within the CEE countries (p equal to 0.73).
  • UK: a linear trend was present for duration of exposure and for cumulative exposure (trend p values 0.004 and 0.01 in Table 3).
  • Asbestos exposure was more common among UK subjects (47% of men, 4% of women) than among CEE subjects (11% of men, 2% of women).
  • UK: risk estimates for PAH did not change when a five-level asbestos variable was added, and the PAH effect was also present in UK subjects unexposed to asbestos.
  • UK, combined exposure, each compared with subjects exposed to neither PAH nor asbestos: odds ratio 4.4 (95% CI 2.17 to 8.94) for PAH plus asbestos, 2.1 (95% CI 0.99 to 4.27) for PAH only, and 2.3 (95% CI 1.29 to 4.26) for asbestos only. In the CEE countries the odds ratio for both exposures was 1.4 (95% CI 0.96 to 2.02).
  • CEE and UK combined: squamous cell carcinoma showed a non-significant association in the highest quartile of cumulative PAH exposure, odds ratio 1.33 (95% CI 0.91 to 1.96). PAH exposure did not seem to influence adenocarcinoma or small cell carcinoma.
  • Odds ratios for PAH exposure decreased by approximately 15% after adjustment for silica and metals.
• The authors' conclusion: The authors concluded that occupational PAH exposure does not appear to substantially contribute to the burden of lung cancer in Central and Eastern Europe. They suggested that the apparently stronger effect in the UK may be due to high exposure levels and a joint effect with asbestos.
• Limitations the authors state:
  • Retrospective exposure assessment is likely subject to some misclassification. Recall of job histories could differ between cases and controls.
  • Differences in PAH exposure prevalence between countries could reflect differences in the quality of exposure assessment.
  • Hospital controls, used in all centres except Warsaw and Liverpool, may not represent the source population.
  • The response rate in the UK (about 45%) was lower than in the CEE countries (about 85%). This could cause selection bias and loss of power.
  • It is difficult to separate the effect of PAH from other occupational lung carcinogens in heavy industry.
  • The results on a synergistic PAH and asbestos effect were not statistically significant and need replication.

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: Occupational Exposure, Lung Cancer, Case-Control Study, Industrial Hygiene, Cumulative Exposure.

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