The effect of age on the relative risk of lung cancer mortality in a cohort of chromium production workers

Background: Hexavalent chromium has been found to increase the risk of lung cancer in occupational studies. It has been suggested that the relative risk of lung cancer may vary by age. Methods: The cohort examined is the Baltimore cohort of chromium production workers. The effect of age on the lung cancer risk from hexavalent chromium exposure was examined using a conditional Poisson regression modeling approach of Richardson and Langholz (R&L) and Cox models with interaction terms of age and cumulative hexavalent chromium exposure. Results: The inclusion of multiple age groups in the R&L approach suggests the existence of an age effect that is also supported by a Cox proportional hazard analysis. The hazard ratio in Cox models with age-cumulative exposure interaction terms was significantly elevated for the youngest age group and significantly decreased for the oldest age group. Conclusions: Our analyses are consistent with the observation that younger chromium production workers have a greater lung cancer risk than older workers.