Congener-specific transfer modelling of dioxins and dioxin-like PCBs in free-ranging cattle grazing in the Dutch floodplains

Cattle grazing in the Dutch floodplains are exposed to polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) and dioxin-like PCBs (dl-PCBs) through the consumption of grass and adhering soil. This can lead to elevated dioxin and dl-PCB levels in meat fat. To manage this contamination issue, the kinetics of these compounds in cattle need to be better understood. This study describes the development and application of a physiologically based kinetic (PBK) model to predict dioxin and dl-PCB levels in muscle fat of ‘Rode Geus’ cattle based on measured levels in grass and soil. Calibration of the model was performed separately for each congener, using measured dioxin and dl-PCB levels in various tissues of 14 animals. Model validation performed using dioxin and dl-PCB samples of 14 other cattle, showed that PBK model predictions were on average a factor 2.4 higher than the measured dioxin and dl-PCB TEQ levels in fat. Despite this difference, the model may still be particularly useful to better understand the relation between environmental dioxin and dl-PCB levels and those in cattle. The model is publicly available with a user-friendly interface on www.feedfoodtransfer.nl and may provide relevant insights for risk assessment and risk management.荷兰洪泛区放牧的肉牛通过采食牧草与附着土壤，接触多氯二苯并对二噁英、多氯二苯并呋喃（polychlorinated dibenzo-p-dioxins and dibenzofurans，简称二噁英）以及类二噁英多氯联苯（dioxin-like PCBs，dl-PCBs）。该暴露途径可导致肉牛脂肪中二噁英与dl-PCBs含量升高。为管控此类污染问题，需更深入明晰此类化合物在牛体内的药代动力学行为。本研究开发并应用了生理药代动力学（physiologically based kinetic，PBK）模型，可基于牧草与土壤中的实测浓度，预测“Rode Geus”肉牛肌肉脂肪中的二噁英与dl-PCBs含量。本研究针对每种同系物分别开展模型校准，校准数据取自14头肉牛各组织中的二噁英与dl-PCBs实测浓度。利用另外14头肉牛的二噁英与dl-PCBs样本进行模型验证，结果显示，PBK模型的预测值平均较脂肪中二噁英与dl-PCBs的毒性当量（TEQ）实测值高出2.4倍。尽管存在此偏差，该模型仍可用于更清晰地阐明环境中二噁英与dl-PCBs含量与牛体内对应污染物含量之间的关联。该模型已通过www.feedfoodtransfer.nl平台公开，搭载友好的用户交互界面，可为风险评估与风险管理提供有价值的参考依据。