Biological and toxicological effects of non-dioxin-like PCBs

Background Polychlorinated biphenyls (PCBs) are a group of 209 congeners with similar basic structure, but differing in the number of chlorines and chlorination pattern. They are potent, persistent and accumulative, and abundantly present in food and the environment. A group of 12 congeners has a dioxin-like planar structure and toxicological properties similar to dioxins and are therefore called dioxin-like PCBs (DL-PCBs). Their risk assessment is included in that of other DL compounds. The rest of the PCBs, with nonplanar structure due to chlorine substitution at ortho position, have a different toxicological profile with possibly several different mechanisms. They are referred to as nondioxin-like PCBs (NDL-PCBs), and their toxic effects have been, so far, poorly characterized because of contamination of several used NDL-PCBs batches with very potent DL impurities (EFSA, 2005: http://www.efsa.europa.eu/de/ scdocs/doc/284.pdf). The aim of the ATHON (Assessing the Toxicity and Hazard of Non-dioxin-like PCBs Present in Food) project was to provide missing critical health hazard information, to clarify biological mechanisms underlying the various types of toxicity of NDL-PCBs and to evaluate these data from the risk assessment point-ofview.