ORIGINAL ARTICLE

Bladder cancer incidence and exposure to polycyclic aromatic hydrocarbons among asphalt pavers

Igor Burstyn^1,2,3, Hans Kromhout², Christoffer Johansen⁴, Sverre Langard⁵, Timo Kauppinen⁶, Judith Shaham⁷, Gilles Ferro¹, Paolo Boffetta¹

¹ International Agency for Research on Cancer, Lyon, France
² Division of Occupational and Environmental Health, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands
³ Community and Occupational Medicine Program, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
⁴ Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
⁵ Centre for Occupational and Environmental Medicine, Rikshospitalet University Hospital, Oslo, Norway
⁶ Finnish Institute of Occupational Health, Helsinki, Finland
⁷ School of Public Health, Tel Aviv University, Israel

Correspondence to:
Dr I Burstyn
The University of Alberta, 13-103E Clinical Sciences Building, Edmonton, Alberta, T6G 2G3, Canada; iburstyn{at}ualberta.ca

Objectives: To investigate the association between exposures to polycyclic aromatic hydrocarbons (PAH) that arises during asphalt paving, and risk of bladder cancer.

Methods: 7298 men included in the historical cohort were first employed between 1913 and 1999 in companies applying asphalt in Denmark, Norway, Finland and Israel. The minimal duration of employment for inclusion in the cohort was two seasons of work. Occupational histories were extracted from personnel files. A follow-up for cancer incidence was conducted through national cancer registries. The authors estimated exposures to benzo(a)pyrene as a marker for 4–6 ring PAH. Exposures were reconstructed by using information about changes in asphalt paving technology in each company over time, the modelled relation between production characteristics and exposure levels, and job histories. Relative risks and associated 95% confidence intervals were estimated using Poisson regression.

Results: 48 bladder cancers among asphalt paving workers were detected; of these, 39 cases were exposed at least 15 years before the diagnosis. Cumulative exposure to PAH was not associated with the incidence of bladder cancer. The association with average exposure became stronger when 15-year lag was considered, revealing a twofold increase in relative bladder cancer risk in the two higher exposure categories. There was an indication of exposure-response association with lagged averaged exposure. Risk estimates were adjusted for age, country, duration of employment and calendar period, did not show heterogeneity among countries and did not materially change when re-estimated after excluding non-primary cancers from follow-up. Previously conducted sensitivity analysis indicates that confounding by cigarette smoking is an unlikely explanation for the observed exposure-response trends.

Conclusions: The authors were unable to control for all possible sources of confounding and bias. The results do not allow conclusion on the presence or absence of a causal link between exposures to PAH and risk of bladder cancer among asphalt workers.

Abbreviations: PAH, polycyclic aromatic hydrocarbons

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