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Exposure-response relationship between lung cancer and polycyclic aromatic hydrocarbons (PAHs): estimates from a large aluminium smelter cohort.
  1. Ben G Armstrong (ben.armstrong{at}
  1. London School of Hygiene & Tropical Medicine, United Kingdom
    1. Graham Gibbs (ggibbs{at}
    1. Safety Health Environment International Consultants Corp and Department of Medicine, Univ of Alberta, Canada


      Objectives: To estimate the exposure-response function associating polycyclic aromatic hydrocarbons (PAH) exposure and lung cancer, with consideration of smoking.

      Methods: Mortality, occupational exposure and smoking histories were ascertained for a cohort of 16,431 persons (15703 men and 728 women) who had worked in one of four aluminium smelters in Quebec from 1950-1999. A variety of exposure-response functions were fitted to the cohort data using generalised relative risk models.

      Results: In 677 lung cancer cases there was a clear trend of increasing risk with increasing cumulative exposure to PAH. A linear model predicted a relative risk of 1.35 (95%CI 1.22-1.51) at 100 ug/m 3-BaP-years , but there was a significant departure from linearity in the direction of decreasing slope with increasing exposures. Among the models tried, the best fitting were a two-knot cubic spline and a power curve (RR=(1+bx)p), the latter predicting a relative risk of 2.68 at 100 ug/m 3-BaP-years. Additive models and multiplicative models for combining risks from occupational PAH and smoking fitted almost equally well, with a slight advantage to the additive.

      Conclusion: Despite the large cohort with long follow-up, the shape of the exposure-response function and the mode of combination of risks due to occupational PAH and smoking remains uncertain. If a linear exposure-response function is assumed, the estimated slope is broadly in line with the estimate from a previous follow-up of the same cohort, and somewhat higher than the average found in a recent meta-analysis of lung cancer studies.

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