Toxicokinetics and Toxicodynamics of Nanoplastics in Daphnia magna are Polymer-Type Dependent

Diverse polymer types of nanoplastics (NPs) pose significant ecological risks in aquatic ecosystems. However, current research has largely centered on polystyrene NPs (PS NPs), which constitute only a minor portion of total NPs in freshwater environments. In this study, we applied a toxicokinetic-toxicodynamic (TK-TD) modeling framework to comparatively assess the accumulation, elimination, and toxicity of four polymer types of NPs (PS, polyvinyl chloride [PVC], poly(methyl methacrylate) [PMMA], and polycarbonate [PC]; all ∼ 80 nm) in Daphnia magna. Aggregation-induced-emission fluorogen labeling enabled precise tracking of NPs. Our findings revealed clear polymer-type-dependent differences: D. magna accumulated and eliminated PMMA and PC NPs more efficiently than PS and PVC NPs. Toxicity followed the order: PS > PVC > PMMA > PC. Transcriptomic analyses indicated that NPs disrupt nutrient digestion, oxidative stress responses, and nervous system function. Using TK-TD modeling, we further predicted the time-dependent median lethal concentrations (LC50) and no-effect concentrations (NEC) for the NPs. The 48-h LC50 values for PS, PVC, PMMA, and PC NPs were 15.0, 43.1, 66.5, and 389.7 mg L–1, respectively, while the corresponding NECs were 4.5, 7.0, 13.5, and 60.0 mg L–1. Our study provides a comprehensive ecological risk assessment of NPs from different polymer types, offering quantitative thresholds to inform the development of polymer-specific water quality criteria for NPs in aquatic environments.