These documents describe EPA's updated approach for evaluating the human health risks from exposures to environmental media containing dioxin-like compounds (DLCs). Dioxin and DLCs are structurally and toxicologically related halogenated aromatic hydrocarbons. Traditionally, the Toxic Equivalency Factor (TEF) Methodology, a component mixture method, has been used to evaluate human health risks posed by these mixtures.

EPA recommends the use of the consensus TEF values for 2,3,7,8-tetrachlorodibenzo-p-dioxin and DLCs published in 2005 by the World Health Organization. The U.S. EPA recommends these TEFs be used for all effects mediated through aryl hydrocarbon receptor binding by the DLCs including cancer and non-cancer effects. Using information that summarizes the range of relative toxicities of the DLCs, the U.S. EPA suggests that conduct of a sensitivity analysis be considered to illustrate the impact the TEFs have on the predicted risk.

• Recommended Toxicity Equivalency Factors (TEFs) for Human Health Risk Assessments of Dioxin and Dioxin-Like Compounds: External Review Draft (PDF)(29 pp, 246 K, September 1, 2009)
• Recommended Toxicity Equivalence Factors (TEFs) for Human Health Risk Assessments of 2,3,7,8-Tetrachlorodibenzo-p-dioxin and Dioxin-Like Compounds (PDF)(38 pp, 652 K, December 2010, 100-R-10-005)