Influence of polystyrene microplastics on bioconcentration and metabolism of 2-ethylhexyl diphenyl phosphate in common carp (Cyprinus carpio)

The synergistic effects of microplastics (MPs) and co-existing pollutants, particularly their impact on aquatic organisms, is an emerging concern. The influence of MPs on the bioconcentration and biotransformation of organophosphate flame retardants (OPFRs) in organisms remains poorly understood. This study investigated the impact of polystyrene microplastics (PS-MPs) on the bioconcentration and metabolism of 2-ethylhexyl diphenyl phosphate (EHDPHP), a specific OPFR, in common carp. Results indicated that the adsorption kinetics of PS-MPs on EHDPHP conformed to the pseudo-second-order kinetic model (R > 0.961), indicating a high adsorption capacity. Both the linear model (R = 0.995) and Freundlich model (R = 0.996) described effectively the adsorption isotherms. Compared with EHDPHP exposure alone, the presence of PS-MPs potentially reduced the bioconcentration of EHDPHP in fish tissues without significantly altering its distribution. Notably, the bioconcentration factors (BCFs) and half-life (t) of EHDPHP were elevated in fish. Furthermore, 14 metabolites, primarily formed through hydroxylation metabolism, were identified, suggesting that PS-MPs may amplify EHDPHP's hydroxylation process. These results offer critical insights into the environmental behavior and risk assessments of MPs and OPFRs, underscoring the need for comprehensive ecological studies in this area.