Polychlorinated biphenyls – toxicity and risks

Polychlorinated biphenyls (PCBs) are synthetic organochlorine compounds differing by their physico-chemical and toxicological properties and tend to bioaccumulate and biomagnificate in the environment and within the food chain. Consequently, humans may be exposed through contaminated drinking water and food, mainly fish, meat and dairy products. Production and usage of PCBs are restricted according to legislation and preventive measures in most of EU countries. In the Republic of Croatia the risk is still present due to military activities during the Patriotic War (1991-1995) when the industrial, electric power and other facilities were largely damaged resulting in leakage of PCBs. Therefore, it is necessary to develop and implement further strategies for identifying contaminated sites and for their remediation in an environmentally sound manner. Additionally, there is a need for safe disposal of PCBs sources including stepwise monitoring of persistent organic pollutants (POPs) level in accordance with Croatian national plan for implementation of the Stockholm Convention. So far, numerous researches indicate a variety of adverse effects of PCBs on human health, such as immunotoxicity, neurotoxicity and genotoxicity. Many of these compounds are potential endocrine disrupters causing reproductive dysfunctions. Toxic properties and potencies of PCB congeners generally depend upon the presence of chlorine atom in ortho position, whereas planar non-ortho- and mono-ortho-substituted PCB congeners are considered to be more toxic. Structural similarities between planar congeners and dioxins explain their mechanism of action mediated through the aryl hydrocarbon receptor (AhR), while non-planar PCBs appear to be weak antagonists of AhR. Some of PCBs' toxic effects are not resulting from the AhR activation, e.g. ortho-substituted PCBs can cause toxicity by other mechanisms. Influence of PCBs on human health and on health of certain members of the populations exposed within the ecosystem still remains the subject of research in medicine, environmental and food toxicology