The presence of toxic chemicals in the environment necessitates precise guidelines regarding exposure limits. An EU project has completed a significant study on a group of chemicals commonly invading food chains.
A vast range of chemicals are toxic to living organisms. Of these, the polychlorinated biphenyls (PCBs) are particularly worrying. Due to their presence in the food chain and the fact that they accumulate in fat tissue, they are common food contaminants. Some PCBs are considered to be dioxin-like. Much research has been done on dioxins, also a group of chlorinated organic molecules that are usually toxic.
Non-dioxin like PCBs (NDL-PCBs) have however been less well studied to date despite the fact that they represent the majority of PCBs present in food and human tissue. Consequently, harmful effects of this group are more difficult to track and there is a lack of health-based guidance values for human exposure due to ignorance regarding their toxicity and mode of action.
The 'Assessing the toxicity and hazard of non-dioxin-like PCBs present in food' (ATHON) project completed major research to fill in the gaps so that advice on neurobehavioural, reproductive and developmental toxicity, liver toxicity and tumour promotion can be documented and provided to health officials and regulators. ATHON also investigated indicators for immunotoxicity, endocrine disturbances and NDL-PCB metabolism.
Data from the ATHON study showed unequivocally that the effects and mode of action of different NDL-PCBs are not the same. Overall, in vivo and in vitro studies showed an impact on neuronal differentiation, growth and function. Endocrine modulating effects also came to light with effects on several hormonal systems including the thyroid, steroid and retinoid systems. Cognitive effects from exposure during development included long-lasting behavioural alterations.
ATHON scientists applied several classification approaches including quantitative structure activity relationships (QSAR) models, toxicokinetics and differential gene expression in vivo. Further studies can use ATHON data to define exposure margins and, in a world where exposure is rarely limited to one toxin, multiple effect parameters.
Assessing exposure limits to toxins for health and safety at work requires a wealth of data. ATHON scientists have provided a very substantial base for use by regulatory agencies to formulate toxicity thresholds and guidelines for maximum levels of exposure to NDL-PCBs.