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Microplastic and nanoplastic particles exert distinct effects on the toxicity and action mechanisms of CuO nanoparticles in Daphnia magna
Summary
Tiny plastic particles floating in water can make copper-based nanoparticles—used in many consumer and agricultural products—significantly more toxic to aquatic life, according to a study on water fleas. The smallest plastic particles (nanoplastics) actually caused more harm than the larger microplastics by disrupting how copper is absorbed and processed in the body, even though microplastics led to more copper buildup overall. This matters because plastics and metal nanoparticles increasingly end up together in our waterways, suggesting their combined effects on ecosystems—and potentially human health through the food chain—could be worse than scientists previously est
Abstract As the use of products incorporating plastics and metal-based nanoparticles (NPs) continues to rise, their co-existence in aquatic environments is becoming increasingly common. This raises the potential for interactions between the two, which may in turn influence the behavior, bioavailability, and toxicity of metal-based NPs. In this study, we explored how polystyrene microplastics (PS-MPs) and polystyrene nanoplastics (PS-NPs) affect the toxicity and action mechanisms of copper oxide nanoparticles (CuO-NPs) in Daphnia magna. Our results demonstrated that both PS-NPs and PS-MPs significantly enhanced the toxicity of CuO-NPs to D. magna, reducing the LC50 values from 4.007 mg L−1 (in the absence of PS-MPs/NPs) to 3.156 mg L−1 and 1.727 mg L−1, respectively. In addition, both PS-NPs and PS-MPs increased Cu-accumulation in D. magna upon the CuO-NPs exposure. Specifically, under 0.1 mg L−1 CuO-NPs exposure, PS-NPs and PS-MPs elevated Cu contents in D. magna by 34% and 127%, respectively, while under 1 mg L−1 CuO-NPs exposure, the increases were 51% and 254%. Mechanistically, the co-exposure to CuO-NPs and PS-NPs disrupted copper absorption, ion homeostasis, and autophagic processes in D. magna, whereas PS-MPs exacerbated CuO-NP toxicity primarily by interfering with oxidative phosphorylation pathways. The results underscore an elevated ecological risk posed by the co-occurrence of micro/nanoplastics and metal-based NPs in aquatic environments.