OBSERVATIONS ON THE DOSE-RESPONSE CURVE FOR ARSENIC EXPOSURE AND LUNG-CANCER

Occupational studies in three countries have related quantitative esti mates of arsenic exposure to lung cancer risks. Mine exposures in Chin a appear to incur a higher relative risk than arsenic exposures elsewh ere. All of the studies with quantitative data are consistent with a s upralinear dose-response relationship. Two studies are also consistent with a linear relationship over an elevated background risk of lung c ancer among arsenic-exposed workers. Neither toxicokinetic mechanisms nor confounding from age, smoking, or other workplace carcinogens that differ by exposure level appear likely to explain this curvilinearity . Plausible explanations include (i) synergism (with smoking) which va ries in magnitude according to the level of arsenic exposure, (ii) lon g-term survivorship in higher exposure jobs among the healthier, less susceptible individuals, (iii) exposure estimate errors that were more prominent at higher exposure levels as a result of past industrial hy giene sampling or worker protection practices.