Size-Dependent Vector Effect of Microplastics on the Bioaccumulation of Polychlorinated Biphenyls in Tilapia: A Tissue-Specific Study

Abstract

Microplastics interact with hydrophobic organic contaminants (HOCs), leading to joint toxic effects on aquatic organisms. This study extensively investigated the tissue-specific accumulation of polychlorinated biphenyls (PCBs) resulting from different sized polystyrene (PS) microplastics in tilapia (Oreochromis mossambicus) using a passive dosing device. A physiologically based toxicokinetic (PBTK) model was applied to evaluate the exchange kinetics and fluxes among the tissues. Moreover, an in vitro simulation experiment was conducted for theoretical validation. The findings demonstrated that the joint effects caused by HOCs and microplastics were influenced by multiple factors such as size and surface properties. The mass transfers of HOCs in specific tissues were closely related to their adsorption capacity and position microplastics can reach. Specifically, although 2 μm microplastics exhibited high adsorption capacity for PCBs, they were retained in the intestines and did not contribute to the PCB bioaccumulation in gills or muscle. While 1 mm microplastics could not be ingested, their vector effects increased the desorption of microplastic-bound PCB-118 in the gill mucus microcosm, thereby facilitating the mass transfer and accumulation of PCB-118 in gills and muscle. This study sheds new light on how the size-dependent vector generated by microplastics affects the tissue-specific accumulation of HOCs in aquatic organisms.

Keywords: Mass transfer kinetics, tissue-specific accumulation, PBTK model, in vivo exposure, in vitro simulation