2.6. Toxic equivalent factor (TEF) scheme and toxic equivalency (TEQ) methodology
Toxic equivalency factors (TEFs) are being developed to assess the potency of
polyhalogenated aromatic hydrocarbons, including polychlorinated dibenzo-pdioxins
(PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs).
Toxic equivalency factors (TEFs) are essentially weighting factors by which the toxicity
of a congener is compared to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin
(TCDD). In this way, concentrations of individual PCB congeners are multiplied by
their TEFs and the results summed to give a toxicity value expressed in TCDD toxic
equivalents (TEQs) through the following equation: