1. Molecule structures and characteristics

Dioxin, furan and polychlorinated biphenyl molecules are formed by two aromatic rings, bridged or not by oxygens, and substituted by chlorines or bromines, the number of which can vary from 1 to 8 (table 1 ). Depending on the position and number of chlorines, there are therefore different congeners: 75 dioxins (PCDDs or PBDDs), 135 furans (PCDFs or PBDFs), 1,550 PBCDDs, 3,050 PBCDFs and 209 polychlorinated biphenyls (PCBs), whose toxicity varies widely depending on their molecular structure. If only chlorinated compounds are considered, 29 of them (7 PCDDs, 10 PCDFs and 12 dioxin-type PCBs) are estimated to be toxic. To estimate PCDD/F toxicity, compound weighting factors (I-TEF: International Toxicity Equilavent Factor) are applied, as shown in Table 2 . Two references...