A temperature-dependent three-compartment toxicokinetic model for assessing bioavailability of microplastic-associated pollutants

Microplastics (MPs) enhance pollutant bioaccessibility by transporting them into organisms. Global warming promotes pollutant desorption from MPs in ectotherms while reducing MPs' adsorption capacity for pollutants in water; nevertheless, its net impact on the bioavailability of MP-associated pollutants remains poorly understood. To address this, this study selected four common MPs preloaded with pollutants and investigated their toxicokinetics using an in vitro fish intestinal epithelial model. Experimental data were employed to refine conventional models, identify key kinetic and thermodynamic parameters, and subsequently develop a temperature-dependent three-compartment toxicokinetic model. The results demonstrate that the in vivo translocation of MP-associated pollutants is predominantly governed by their direct transfer from MPs to cells, a process whose temperature dependence is regulated by the activation energy for transport. The integrated metric φ× ε, combining the environmental adsorption coefficient of pollutants on MPs (φ) with their transfer efficiency within organisms (ε), establishes a unified bioavailability standard that effectively eliminates interference from environmental concentration variations and metabolic processes. Application of this metric revealed that temperature elevation significantly enhanced pollutant bioavailability, suggesting that global warming may exacerbate associated ecological risks. This study provides an innovative framework for identifying high-risk MP-associated pollutants and supports developing sustainable manufacturing strategies in a warming climate.