What is a Toxic Equivalent (WHO-TEQ)?

Dioxins and dioxin-like PCBs are chemicals with different degrees of dioxin-like toxicity. The use of Toxic Equivalency Factors (TEFs) allows concentrations of the less toxic compounds to be expressed as an overall equivalent concentration of the most toxic dioxin, 2,3,7,8-TCDD. These toxicity-weighted concentrations are then summed to give a single concentration expressed as a Toxic Equivalent (TEQ). The system of TEFs used in the UK and a number of other countries is that set by the World Health Organization (WHO), and the resulting overall concentrations are referred to as WHO-TEQs.