Biologic Implications from an Epidemiologic Study of Chromate Production Workers

This analysis of an epidemiologic study of chromate production workers evaluates several variables related to the biologic understanding of chromate-induced lung cancer. Age at hire was found to be negatively associated with lung cancer risk. Reducing exposure was found to have benefits that extended into older age, and the benefits were greater when the reduction began at an earlier age. The same cumulative exposure over a short period of time (30 days) had more effect than if the exposure occurred over 10 years. The greater carcinogenic effect among those exposed at an early working age is consistent with an ability to more efficiently reduce hexavalent chromium intracellularly at younger ages. The greater effect at younger ages may also explain why short-term cumulative hexavalent chromium exposure was found to have more effect than the equivalent cumulative exposure spread over a longer term. The SMR for lung cancer was highest in the decade following cessation of exposure and may reflect the extremely irritating nature of hexavalent chromium.