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Assessing the Toxicity and Hazard of Non-dioxin-like PCBs present in food

Final Report Summary - ATHON (Assessing the Toxicity and Hazard of Non-dioxin-like PCBs present in food)

The European Commission has pointed out the need to improve the health and well-being of European citizens through a higher quality of their food, including improved control of food contaminants. PCBs are prevalent contaminants in fatty food of animal origin such as meat, certain fish and dairy products. Non-dioxin-like (NDL) polychlorinated biphenyls (PCBs) are poorly characterised from a toxicological point of view, and to date, no health based guidance values for human exposure have been established. Since NDL-PCBs constitute a major part of the PCBs found in food and human tissues, it has become an urgent matter to advance the understanding of their toxicity.

The topic has recently been discussed in several organisations, which provide advice to the regulators and neurobehavioural, reproductive and developmental toxicity, liver toxicity and tumour promotion have been pointed out to be of particular concern. ATHON addressed all of these effects, as well as indicators for immunotoxicity, endocrine disturbances, and NDL-PCB metabolism.

Following the EFSA recommendation of generating more information on toxicological effects of NDL-PCBs with regard to human health, the qualitative findings of ATHON, in summary, show that NDL-PCBs of high purity cause a partly different pattern of effects as compared to the effects observed for DL PCBs.
Studies in ATHON have clearly shown that NDL PCBs have endocrine system modulating properties with effects on several hormonal systems including the thyroid, steroid and retinoid systems. Several neurotoxicity modes of action influencing cognitive impairment and motor disorders have been confirmed both in vivo and in vitro. Exposure to NDL-PCBs during development induced long-lasting behavioural alterations.

The findings in vivo that NDL-PCBs perturb neurotransmitter transport and signalling pathways essential for neuronal differentiation, growth and function are also supported by in vitro studies. Sex differences in effects after exposure to NDL-PCBs have been observed for multiple end-points including endocrine disruption, gene expression profiles, induction of hepatic enzyme activities, and changes in bone geometry. The results also indicate that specific aspects of NDL-PCB toxicity can be assigned to the in vivo formation of PCB-metabolites.

The results generated within the project clearly show that NDL-PCBs are not a homogenous group of compounds and several classification approaches have been applied including in vitro based QSAR models, toxicokinetics and differential gene expression in vivo. Access to ATHON tissue level and toxicokinetic data will allow for further detailed quantitative estimations, e.g. margin of exposure data, for multiple effect parameters and multiple NDL PCB congeners. Thus, taken together qualitative as well as quantitative results from ATHON will be of direct importance for regulatory agencies in their health risk and safety assessment work.