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Incubation in Wastewater Reduces the Multigenerational Effects of Microplastics inDaphnia magna
Summary
Researchers compared the multigenerational toxicity of pristine versus wastewater-aged microplastics on the freshwater organism Daphnia magna. They found that microplastics incubated in wastewater, which sorbed a complex mixture of real-world pollutants, actually showed reduced toxicity compared to pristine particles across multiple generations. The study suggests that environmental aging processes may alter the toxicological profile of microplastics in ways that are not always predictable from laboratory studies with pristine particles.
The aging of microplastics in the environment changes their physicochemical properties. While this may affect their toxicity, comparative data on the effects of aged compared to pristine microplastics are scarce. One of those aging processes is the sorption of chemicals, which has mainly been studied for individual pollutants present in marine ecosystems. To investigate how the sorption of a complex mixture of freshwater pollutants affects the toxicity of microplastics, we incubated irregular polystyrene particles (≤63 μm) in either wastewater or ultrapure water. We exposed Daphnia magna to these aged microplastics and their pristine counterparts (80, 400, 2000, and 10,000 particles mL-1) over four generations using food limitation as an additional, environmentally realistic stressor. Both particle types affect the survival, reproduction, adult and neonate body lengths, and growth. An exposure to pristine microplastics results in the extinction of the third generation of daphnids. In contrast, wastewater-incubated particles induced a lower mortality. The incubation with wastewater does not change the microplastics' size, surface charge, and structure. Consistent with the literature, we assume that the adsorption of dissolved organic matter is a key aging process reducing the toxicity of microplastics. Consequently, toxicity testing using pristine microplastics may overestimate the effects of plastic particles in nature.