UNIT RISK ESTIMATES FOR AIRBORNE ARSENIC EXPOSURE - AN UPDATED VIEW BASED ON RECENT DATA FROM 2 COPPER SMELTER COHORTS

The current unit risk for airborne arsenic, 4.29 X 10(-3), was establi shed by the EPA in 1984. Using updated results from a cohort mortality study on Tacoma smelter workers and recent findings from a cohort stu dy of 3619 Swedish smelter workers, new unit risk estimates were devel oped for the respective cohorts. Methods were analogous to those used by the EPA in 1984, and all estimates were derived under an absolute r isk model. A new unit risk 1.28 X 10(-3), was estimated for the Tacoma smelter cohort which was a factor of 5 less than the EPA's earlier es timate, and a direct result of radically revised exposure estimates. A unit risk of 0.89 x 10(-3) was estimated from the Swedish study. Pool ing these new unit risk estimates with the EPA's earlier estimates fro m the Montana smelter cohort yielded a composite unit risk of 1.43 X 1 0(-3). Based on this estimate, the present unit risk may overestimate the effects of airborne arsenic by a factor of 3. A need to update the unit risk for airborne arsenic and the collateral IRIS database is ev ident from the results, (c) 1994 Academic Press Inc.