Potential impact on food safety and food security from persistent organic pollutants in top soil improvers on Mediterranean pasture

The organic carbon of biosolids from civil wastewater treatment plants binds persistent organic pollutants (POPs), such as polychlorodibenzo -dioxins and -furans (PCDD/Fs), dioxin and non-dioxin -like polychlorobiphenyls (DL and NDL-PCBs), polybrominated diphenyl ethers (PBDEs), and perfluorooctane sulfonic acid (PFOS). The use of such biosolids, derived digestates and composts as top soil improvers (TSIs) may transfer POPs into the food chain. Weevaluated the potential carry-over ofmain bioavailable congeners from amended soil-to-milk of extensive farmed sheep. Such estimates were compared with regulatory limits (food security) and human intakes (food safety). The prediction model was based on farming practices, flocks soil intake, POPs toxicokinetics, and dairy products intake in children, of the Mediterranean area. TSI contamination ranged between 0.20-113 ngWHO-TEQ/kg dry matter for PCDD/Fs and DL-PCBs (N=56), 3.40-616 μg/kg forS6 NDL-PCBs (N=38), 0.06-17.2 and 0.12- 22.3 μg/kg for BDE no. 47 and no. 99, 0.872-89.50 μg/kg for PFOS (N=27). For a 360 g/head/day soil intake of a sheep with an average milk yield of 2.0 kg at 6.5% of fat percentage, estimated soil quality standards supporting milk safety and security were 0.75 and 4.0 ngWHO TEQ/kg for PCDD/Fs and DL-PCBs, and 3.75 and 29.2 μg/kg for S6 NDL-PCBs, respectively. The possibility to use low-contaminated TSIs to maximize agriculture benefits and if the case, to progressively mitigate highly contaminated soils is discussed.