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An international cohort of asphalt workers was assembled to study cancer risk after bitumen exposure. This article describes the combination of the exposure assessment with the exposure-response for a quantitative risk assessment for lung cancer mortality within the Dutch component of the study. We identified a retrospective cohort of 3,709 workers with at least one season of employment. Semi-quantitative exposure to bitumen fume was estimated by a job-exposure matrix. Exposure-response relations were fitted by Poisson regression, and excess lifetime risks through age 75 were calculated by a life table method. Working lifetime cumulative exposure to bitumen fume was calculated under different scenarios, representing past and future exposures. For workers with exposures accumulated in the past, excess risks for lung cancer varied from 7.8 to 14.3%. Calculations for future exposures resulted in considerably lower excess risks ranging from 0.6 to 2.6%. The calculated excess risks for lung cancer mortality after working lifetime exposure to bitumen fume depend strongly on when exposure was experienced and to some extent on the exposure-response model chosen, while confounding by smoking cannot be ruled out. Nevertheless, the excess lifetime risk for lung cancer in this Dutch cohort of asphalt workers is above benchmark risks as applied by the Dutch Health Council. Current exposure levels have decreased this risk considerably, but further exposure control may be required.

Background Using data from a Dutch cohort of workers in road construction and asphalt mixing companies, this article describes possible confounding of the association between exposure to bitumen fume and lung cancer mortality by smoking. Methods A retrospective cohort of 3,714 workers with at least one season of employment was identified. Semi‐quantitative exposure to bitumen fume was assessed by a job‐exposure matrix. Information on smoking habits was available for a sub‐cohort of 1,138 workers, who underwent medical examinations by the occupational health services in the past. Results Smoking habits differed between occupational title groups and there was a positive association between cumulative exposure and smoking. Internal analyses using the non‐exposed subjects as reference category, showed a positive association between semi‐quantitative bitumen fume exposure and lung cancer risk. After adjusting for differences in smoking habits, all relative risks were reduced, but a weak positive association could still be observed. Conclusion Confounding by smoking on the association between exposure to bitumen fume and lung cancer mortality is possible, although the positive trend (not statistically significant) for lung cancer mortality remained. Only a nested case‐control study may allow proper treatment of potential (residual) confounding by smoking in this population. Am. J. Ind. Med. 43:79–87, 2003. © 2003 Wiley‐Liss, Inc.

Background An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses. Methods In a multi‐country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953–2000. Exposures to bitumen fume, coal tar, 4–6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job‐exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated. Results The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99–1.18) was comparable to that of non‐exposed workers (SMR 1.05, 95% CI 0.92–1.19). In a sub‐cohort of bitumen‐exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02–1.48). The analysis based on the semi‐quantitative, matrix‐based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose‐response was suggested for average level of exposure, applying a 15‐year lag, which was marginally reduced after adjustment for co‐exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm. Conclusions The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck. Am. J. Ind. Med. 43:28–39, 2003. © 2003 Wiley‐Liss, Inc.

Background Inhalation of bitumen fumes is potentially carcinogenic to humans. Methods We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow‐up during 1953–2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers. Results The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90–0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04–1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89–1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89–1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers. Conclusions European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out. Am. J. Ind. Med. 43:18–27, 2003. © 2003 Wiley‐Liss, Inc.

Background We compared performance of different exposure assessment approaches in a cohort study of cancer risk among European asphalt workers. Methods Three bitumen fume exposure indices (duration of exposure (years), average exposure (mg/m3) and cumulative exposure (mg/m3*years)) and two latency models (with and without a 15 year lag) were considered for an association between lung cancer mortality and bitumen fume. Results There was no association between lung cancer risk and either duration or cumulative exposure. However, there was the suggestion of an increase in lung cancer risk accompanying rise in average exposure. Only models with average bitumen fume exposure (with or without lag) improved model fit, albeit to the same extent. Conclusions Constructing quantitative indices of exposure intensity was justified because they produced the greatest improvement in fit of models that explored possible relationship between bitumen fume exposure and lung cancer risk. The identified associations require further investigation. Am. J. Ind. Med. 43:40–48, 2003. © 2003 Wiley‐Liss, Inc.