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Exposure–response relationship between lung cancer and polycyclic aromatic hydrocarbons (PAHs)
  1. B G Armstrong1,
  2. G Gibbs2,3
  1. 1
    London School of Hygiene and Tropical Medicine, London, UK
  2. 2
    Safety Health Environmental International Consultants, Devon, Alberta, Canada
  3. 3
    Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
  1. Correspondence to Ben G Armstrong, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK; ben.armstrong{at}lshtm.ac.uk

Abstract

Objectives: To estimate the exposure–response function associating polycyclic aromatic hydrocarbon (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 (15 703 men and 728 women) who had worked in one of four aluminium smelters in Quebec from 1950 to 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 measured as benzo(a)pyrene (BaP). A linear model predicted a relative risk of 1.35 (95% CI 1.22 to 1.51) at 100 μg/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 μg/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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Footnotes

  • See Commentary, p 716

  • Funding This research was carried out with the financial support and full co-operation of Alcan aluminium smelters.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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