Toxic equivalent
Toxic equivalent factor (TEF) expresses the toxicity of dioxins, furans and PCBs in terms of the most toxic form of dioxin, 2,3,7,8-TCDD. The toxicity of the individual congeners may vary by orders of magnitude.
With the TEFs, the toxicity of a mixture of dioxins and dioxin-like compounds can be expressed in a single number - the toxic equivalent, TEQ. It is a single figure resulting from the product of the concentration and individual TEF values of each congener.
The TEQ concept has been developed to facilitate risk assessment and regulatory control.
At present two systems are in operation the International Toxic Equivalents for dioxins and furans only, represented as I-TEQDF and the World Health Organisation scheme, represented as WHO-TEQDFP, which includes PCBs. The two systems do not conflict in their assessments.
See also
Sources
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