Levels and trends of PCDD/Fs and DL-PCBs in Polish animal feeds, 2004-2017.

Feed control is essential for the safety of animal-origin food. It is estimated that more than 80% of human exposure to dioxins and related compounds comes from the consumption of animal-origin food, and farm animals are exposed to dioxins mainly through the feed. A monitoring programme for dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs)) and dioxin-like polychlorinated biphenyls (DL-PCBs) was conducted in the Polish feed market between 2004 and 2017. Using two complementary ISO 17025-accredited analytical methods (bioassay and high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS)), 2919 samples of plant, animal and minerals origin were analysed. The total number of samples exceeding the maximum limit (ML) was 52, which is 1.8% of all tested samples. They all contained PCDD/Fs in concentrations over the ML, and in 16 samples the limit for the sum of PCDD/F/DL-PCBs was also exceeded. The highest dioxins level was found in feedstuffs derived from Baltic fish; the fish oil was followed by fish meal. Low-chlorinated furans (2.3,7,8 TCDF, 2,3,4,7,8-PCDF and 1,2,3,7,8-PeCDF) were dominant and these congeners accounted for the toxicity expressed in WHO toxic equivalents (WHO-TEQ). In this category, 155 out of the 498 samples (32%) exceeded the action threshold (AT) for PCDD/Fs and in 10 samples (2.0%) for DL-PCBs. Non-compliant fish meals were found in 34 (5.6%) of the tested samples, in 0.7% of compound feeds, and in 1.5% of plant-origin materials. Seven dried plant-derived materials contained PCDD/F level above ML, including alfalfa, maize, apple, basil and beet pulp pellets containing molasses. The dry vegetable materials were mostly contaminated by the 2,3,7,8-furans, the congeners arising from a faulty drying process. No significant time trend can be seen. From the obtained results, it can be concluded that concentrations of PCDD/Fs and DL-PCBs in Polish feed materials were sufficiently low to ensure low concentrations in animal-derived products.