Multi-cascade physiologically based kinetic (PBK) matrix model: Simulating chemical bioaccumulation across food webs

In modern ecosystems, many substances that biomagnify within food webs adversely affect organisms and ecological systems. To facilitate high-throughput screening of contemporary chemicals, we developed a multi-cascade physiologically-based kinetic (PBK) matrix model to simulate bioaccumulation and biomagnification along food chains. The model's validity is supported by the mean model bias (MB) values, which fall within the acceptable range when compared with measured biomagnification factors (BMFs) reported in the literature. Analyzing 3,074 organic chemicals, we estimated their biotransfer factors (BTFs)-the steady-state ratio of chemical concentrations in primary consumer tissues to those in their feed-and their BMFs-the steady-state ratio of chemical concentrations in predators to their prey. Our results reveal consistent BTF trends across different tissues within the same species for a given chemical. Chemicals with moderate lipophilicity and low diffusivity tend to be retained longer in organisms, leading to higher BMFs. Notably, mammals appear particularly sensitive to persistent organic pollutants, while birds and ectothermic species do not exhibit clear patterns. Overall, the study highlights that animal physiological parameters and chemical physicochemical properties are more critical in determining bioaccumulation and potential toxicity than an organism's trophic position. Future research should refine key physiological parameters, such as hepatic metabolic rate constants, account for life-stage variations, and evaluate multiple exposure pathways to further enhance model accuracy and real-world applicability.