Interim Procedures for Estimating Risks Associated with Exposures to Mixtures of Chlorinated Dibenzo-P-Dioxins and-Dibenzofurans (CDDs and CDFs) and 1989 Update

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As part of its effort to address risks posed by chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans (CDDs and CDFs) in the environment, EPA has adopted an interim procedure, based on dioxin toxicity equivalence factors (TEFs), for estimating the hazard and dose-response of complex mixtures containing CDDs and CDFs in addition to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The TEF procedure, and the scientific data upon which it is based, are the subject of the report. The document describes the recommended interim procedure for generating the TCDD equivalence of complex mixtures of CDDs and CDFs, based on congener or homologue-specific data, and for using such information in assessing risk. EPA initially adopted the TEF procedure in a 1987 version of this document (EPA/625/3-87/012). Part I of this document is the 1987 version and Part II is an updated version that adopts 1989 international NATO/CCMS TEF values.

This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.