Dose-response implications of the University of Alabama study of lymphohematopoietic cancer among workers exposed to 1,3-butadiene and styrene in thesynthetic rubber industry

New quantitative cancer risk estimates for exposure to 1,3-butadiene are pr esented. These estimates are based on the most recent human epidemiologic d ata developed by Drs Delzell and Macaluso and their colleagues at the Unive rsity of Alabama at Birmingham. The implications of Poisson regression anal yses of the relative rate for leukemia are explored using their updated dos e estimates and lymphohematopoietic cancer data. The Poisson regression mod el in these analyses has the same form as in the U.S. Environmental Protect ion Agency (EPA)'s draft risk assessment of 1,3-butadiene [U.S. Environment al Protection Agency, Health Risk Assessment of 1,3-Butadiene - External Re view Draft, National Center for Environmental Assessment, Office of Researc h and Development, 63 Fed. Reg. 7167 (February 12, 1998) Publication NCEA-W -0267, Washington, 1998]. Consistent with the proposed cancer risk assessme nt guidelines of the EPA and the EPA's draft risk assessment, the explorati on includes the maximum likelihood estimate of the 'effective concentration ' (EC01) corresponding to an extra risk of leukemia of 0.01 (1%) from a lif etime continuous exposure to 1,3-butadiene based on a linear dose-response model and the cumulative 1,3-butadiene dose metric (ppm-years). The incorpo ration of the most recent exposure estimates results in a 2.5-fold decrease in the estimates of leukemia risks computed by EPA. In addition, three cha nges proposed by the American Chemistry Council (formerly the Chemical Manu facturers Association) to the EPA's Science Advisory Board (SAB) for EPA's draft risk assessment of 1,3-butadiene are incorporated into the calculatio n. This results in approximately an additional fivefold decrease in the ris k estimates of leukemia. The leukemia cancer risk estimates in the EPA's dr aft risk assessment of 1,3-butadiene decrease by approximately a factor of 13-fold when the updated epidemiologic data and the alternative numbers pro posed by industry to the SAB are both incorporated. Specifically, the maxim um likelihood estimate of the EC01 increases from EPA's 1.2 ppm to 2.8 ppm on the basis of the updated epidemiologic data and increases further to 15. 1 ppm when the CMA's proposed changes are also incorporated. (C) 2001 Elsev ier Science Ireland Ltd. All rights reserved.