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.
Adult Cause of Death