title: Lung cancer mortality in a Dutch cohort of asphalt workers: evaluation of possible confounding by smoking.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division Environmental and Occupational Health, Utrecht University, Utrecht, The Netherlands.
authors.forename: Mariëtte
authors.initials: M
authors.lastname: Hooiveld
authors.forename: Ton
authors.initials: T
authors.lastname: Spee
authors.forename: Igor
authors.initials: I
authors.lastname: Burstyn
authors.forename: Hans
authors.initials: H
authors.lastname: Kromhout
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
mesh_terms: D000328:Adult; D002423:Cause of Death; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D019570:Inhalation Exposure; D008175:Lung Neoplasms / Q000401:mortality*; D009426:Netherlands; D009784:Occupational Diseases / Q000401:mortality*; D016273:Occupational Exposure; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*