Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzifurans (PCDFs) comprise a family of chemicals containing 210 specific monochlorinated and polychlorinated congeners. In 1987, USEPA formally adopted an interim procedure for estimating risks associated with complex environmental mixtures containing PCDDs and PCDFs (Bellin and Barnes, 1987). The procedure used a set of toxicity equivalency factors (TEFs) to convert the concentration of congeners into an equivalent concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic of the 210 congeners. The TEFs have been reviewed and updated periodically, the most recent update being USEPA (1989b) and MADEP ( ).
A list of current TEFs is presented in Table 7.2. .
MADEP Derived Toxicity Equivalency factors (TEFs)
|Mono-, Di- and Trichlorinated dibenzo-p-dioxins||0.001|
Other Tetrachlorinated dibenzo-p-dioxins
Other Pentachlorinated dibenzo-p-dioxins
Other Hexachlorinated dibenzo-p-dioxins
Other Heptachlorinated dibenzo-p-dioxins
|Mono-, Di- and Trichlorinated dibenzofurans||0.001|
Other Tetrachlorinated dibenzofurans
Other Pentachlorinated dibenzofurans
Other Hexachlorinated dibenzofurans
Other Heptachlorinated dibenzofurans
|from MADEP (Silverman and Hutcheson, 1991)|