摘要：
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.
