The evaluation of dioxin and dioxin-like contaminants in selected food samples obtained from the Belgian market: comparison of TEQ measurements obtained through the CALUX bioassay with congener specific chemical analyses.

A limited number of different foods were analysed for dioxin-like compounds by the CALUX bioassay which is an in vitro luciferase reporter gene assay measuring chemical activation of the aryl hydrocarbon receptor. Sixty-two milk samples were obtained from a surveillance campaign, 34 meat samples and 34 fishery products were purchased from the Belgian market. Bio-analytical and chemo-analytical dioxin toxicity equivalents (TEQ) values of the same milk samples were compared. Spearman's Rank correlation coefficients of 0.72, 0.67, 0.73 were obtained respectively between CALUX-TEQ and PCDD/F-TEQ, DL-PCB-TEQ and PCDD/F+DL-PCB-TEQ. The bioassay limit of detection was 0.1 pg TEQ from 1 g animal lipid, the limit of quantification was 0.4 pg TEQ. The repeatability of the CALUX bioassay (variability of butter fat samples analysed in the same run) showed a coefficient of variation (CV) of 10%, intra laboratory reproducibility based on independent runs of the same butter fat samples showed more variation (CV of 26% for samples above 2 pg TEQ/g lipid). All milk samples with a chemical TEQ value above the current limit value in Belgium showed an elevated CALUX-TEQ concentration, above 6 pg TEQ/g lipid. No false negative results were obtained. Based on the good correlation between CALUX-TEQ and chemically measured TEQ levels, the CALUX bioassay can be recommended as a screening tool for routine measurement of potentially toxic PHAHs in milk samples. Chemical analyses could then largely be restricted to positive samples, in order to identify the nature and to quantify the concentration of the chemicals that give the positive signal. Meat samples showed lower CALUX-TEQ values per gram lipid compared to fish samples. The fish samples showed a wider range of CALUX-TEQ values than the meat samples.