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

Abstract

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.