John Wiley & Sons, Ltd.

Co‐exposure of ZnO nanoparticles and UV radiation to Daphnia magna and Danio rerio: Combined effects rather than protection

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The application of nanoparticles (NPs) in consumer products has been increasing over the past few years. Their release to the environment is likely to happen at any stage of production or usage of NPs‐containing products. Zinc oxide nanoparticles (ZnO‐NP) are among the most used NPs in the market due to its intrinsic properties, such as UV absorption. The aim of this study was to assess the combined effects of ZnO‐NP and UV radiation (UVR) on two freshwater species: Daphnia magna and Danio rerio. The initial hypothesis was that the presence of ZnO‐NP in the aquatic media would decrease the damaging effects of UVR for both species. The endpoints assessed for Daphnia magna were immobilisation, feeding inhibition and reproduction output, whereas for Danio rerio, egg development was studied during 96h and mortality, hatching delay and abnormal development were the endpoints recorded. Combined exposures were designed based on the single toxicity of both stressors and analyzed based on the Independent Action (IA) concept and exploring possible deviations for synergism/antagonism (SA), dose level (DL) and dose ratio (DR). Combined exposures with Daphnia magna induced synergism on reproduction, decreasing the number of neonates produced more than expected based on both stressors individual toxicity. Single exposures of Danio rerio embryos to both stressors induced negative effects. The combined exposures caused a dose‐ratio deviation pattern on mortality and hatching, with a synergism observed when ZnO‐NP was the dominant stressor, changing to antagonism when UVR dominated the combined exposure. Therefore and regarding the results attained, studying ZnO toxicity under laboratory conditions may underestimate the risks, considering the potential interaction on effects when combined with UVR. This article is protected by copyright. All rights reserved

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