Congeners

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Congeners: chemicals derived from the same parent compound. PCBs, PCDDs and PCDFs are all mixtures of closely related compounds which are derivatives of biphenyl, dibenzo-p-dioxin and dibenzofuran, respectively. Various number of hydrogen atoms in these parent compounds have been replaced with chlorine atoms, producing 209 possible PCBs, 75 possible PCDDs and 135 possible PCDFs. Derivatives in each group are called congeners in relation to other members of the same group. 17 PCDD/F congeners (7 PCDDs and 10 PCDFs) have "lateral" chlorines in positions 2,3,7 and 8, and are commonly measured and summed up by using TEq concept. Similarly PCB-TEqs are used for "dioxin-like" non-ortho or mono-ortho PCB congeners (see Ortho-PCBs).