To better assess the risk of microplastics (MPs) as a vector for contaminants, it is essential to understand the relative importance of MPs compared to other pathways for chemical transfer as well as the consequences of co-exposure. In this study, we exposed Japanese medaka (Oryzias latipes) to anthracene (ANT, 0.1 mg/L) in the presence or absence of pristine polyethylene MPs (PE-MPs, 106 beads/L), to quantify the vector effect of PE-MPs on ANT accumulation. Under the ANT-MPs co-exposure conditions, PE-MPs rapidly accumulated in the gastrointestinal tract of the medaka during a 14-day uptake phase, with an average bioconcentration factor of 171.4 L/kg. The PE-MPs could absorb and accumulate approximately 70 % of the ANT from the water sample. The PE-MPs changed the pharmacokinetic profile of ANT in medaka by decreasing both the uptake and depuration rate constants. The one compartment with first-order elimination model estimated that the amounts of ANT in the water phase and absorbed by PE-MPs (i.e., a vector effect) contributed about 67 % and 33 % of the ANT accumulation in medaka, respectively. At the end of the uptake (exposure) phase, however, the presence of PE-MPs did not significantly alter the final ANT concentrations in the fish body or alter the behavioral impacts of ANT. Thus, PE-MPs ingestion may act as a vector to concentrate and transfer ANT to medaka, but the presence of these particles may have limited adverse effects on fish under co-exposure systems of the type used in this study.
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