Microplastics in Feed Affect the Toxicokinetics of Persistent Halogenated Pollutants in Atlantic Salmon

Abstract

Microplastics (MPs) act as carriers of persistent organic pollutants (POPs) and this combination may affect their behaviour in fish. In Atlantic salmon (Salmo salar), the toxicokinetics of 14 persistent chlorinated, brominated, and perfluorinated contaminants in combination with MPs were therefore investigated in a feeding trial, in which the fish received diets with contaminants sorbed to MP 2% LD-PE 125-250 µm, as clean MP  feed:contaminated feed (1:1), or as a contaminated feed without MPs. The diet with contaminants sorbed to MPs showed higher accumulations of lipophilic contaminants compared to the other two diets. The depuration of the contaminants showed for several of the contaminants significantly lower eliminations from salmon fillets for the diet with the inclusion of 2% MP with absorbed contaminants compared to the diet with the same contaminant concentrations in the absence of MPs. The bioavailability of lipophilic contaminants in salmon fed the diet with contaminants sorbed to MP was not reduced but rather enhanced, despite POPs having a high affinity for MPs, which passed through the intestinal tract without crossing to the circulatory system. This finding indicates that MPs in the trial acted as a vector for the transfer of sorbed POPs to salmon. The lipid-soluble chlorinated and brominated POPs had high assimilation efficiencies from feed to salmon fillets (41-89%), and their respective toxicokinetic parameters per diet correlated with the hydrophobicity of the contaminants. The PFOA, PFNA and PFOS had low assimilation efficiencies (≤11%), which can be explained by faster eliminations, (t½11-39 days) compared to other POPs as well as a lower proportion distributed to the fillet, compared to e.g. the liver.

Keywords: salmon, PCB, BFR, PFAS, microplastic