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<p>The differences sometimes observed between established screening and confirmatory analytical methods for dioxins and PCBs in food will be investigated, to examine whether ‘false positive’ signals in bioassays are due to a contribution from Ah receptor-binding ligands other than dioxins (eg related emerging contaminants) and may in fact better reflect the total dioxin-like toxicity in the sample.</p>
<p>The project uses expertise of two of the foremost laboratories in this field – RIKILT, which has extensive experience of about a decade of using bio-analytical methods such as CALUX, and Fera, which is at the leading edge of emerging contaminant research and is the National Reference Laboratory for dioxins. The project will draw on expertise from both organisations to understand the differences that sometimes arise between methodologies with different scientific approaches.</p>
<p>About 100 food samples will be measured for total dioxin-like activity, in duplicate, using established CALUX (and/or other bioassay techniques), in a range of samples considered likely to contain the highest levels of contamination with respect to these compounds (eg fish liver, oily fish, sheep, bovine and porcine liver and carcass meat, brown crab meat, duck eggs). Known dioxin-like compounds will be measured, and they will be quantified and compared with the total activity found from the bioassay measurements. Samples for which there is significant unaccounted activity will be further investigated to detect and identify the compounds responsible.</p>
<p>The outcome of the study, including the methodology used and discussion of the findings, will be published in a peer-reviewed journal.</p>
<p>Background: Bioassay methods for measuring dioxins, based on aryl hydrocarbon (Ah) receptor-binding, have been available for some time. However, there have been reports that high results, for example in soil samples collected near waste sites, cannot be fully explained by the presence of chlorinated dioxins, furans and biphenyls. These are well characterised and have been widely measured and reported in food but there is increasing knowledge of brominated and mixed halogenated dioxins and biphenyls, as well as other classes of compounds, known or predicted to possess dioxin-like activity, for example polychlorinated naphthalenes and halogenated PAHs. In the Committee of Toxicity’s (COT) December 2006 opinion on the revised World Health Organization toxicity equivalent factors (WHO-TEFs) for chlorinated dibenzodioxins/furans and dioxin-like polychlorinated biphenyls (PCBs), the COT referred to the need to investigate other dioxin-like chemicals.</p>