The U.S. Environmental Protection Agency (EPA) has prepared this Health Effects Support Document to assist in determining whether to establish a National Primary Drinking Water Regulation (NPDWR) for aldrin and dieldrin. Case study reports of human exposures and laboratory studies with animals demonstrate that oral exposure to both of these compounds can cause various adverse systemic, neurological, reproductive/developmental, immunological, and genotoxic effects. Although multiple bioassays have established aldrin and dieldrin as hepatocarcinogenic in several strains of mice, they are apparently not carcinogenic in rats, and several large epidemiology studies have failed to associate convincingly exposure to them with cancer in humans. While some of these effects occur only at moderate-to-high doses, others have been observed at doses lower than 0.1 mg/kg bw/day. Nonetheless, the relatively infrequent occurrences of aldrin/dieldrin at very low concentrations indicated by monitoring data, coupled with the fact that they are no longer manufactured or used in this country, indicate that aldrin/dieldrin concentrations of concern are unlikely to be found in public water systems. EPA will present a determination and further analysis in the Federal Register Notice covering the Contaminant Candidate List decisions.

"February 2003." "EPA 822-R-03-001." "This document was prepared under U.S. EPA Contract No. 68-C-01-002, Work Assignment No. B-11, with Sciences International, Alexandria, VA ..."--Acknowledgements. Includes bibliographical references.