John Wiley & Sons, Ltd.

Zinc oxide nanoparticles toxicity to Daphnia magna: Size dependent effects and dissolution

As the production of zinc oxide nanoparticles (ZnO‐NPs) and other metal oxides is exponentially increasing, it is important to investigate potential environmental and health impacts of such nanoparticles.Nanoparticles properties may change in different water media (e.g., size, dissolution rate) and their characterization is essential to derive conclusions towards toxicity results.Therefore, an aquatic model organism, Daphnia magna, was used to investigate the effect of ZnO‐NPs with 2 different particle size (30 nm and 80–100 nm) and then compare these effects with ZnO micro‐sized particles (> 200 nm) and the ionic counterpart (in the form of ZnCl2) on immobilisation, feeding inhibition and reproduction endpoints. The 48‐h LC50 values for immobilisation ranged between 0.76 mg Zn.L−1 for the ionic zinc and 1.32 mg Zn.L−1 for ZnO‐NPs of 80–100 nm. For the chronic exposures, the reproduction output was impaired similarly amongst zinc exposures, and possibly mainly driven by the zinc ionic form. The concentrations used showed a total dissolution after 48‐h. On the other hand, feeding activity was more affected by the 30 nm ZnO‐NPs than by the ionic zinc, showing that the particulate form was also playing an important role in the feeding inhibition of Daphnia magna. Dissolution and particles' size in the daphnia test media showed to be essential to derive conclusions on toxicity. Therefore they can possibly be considered critical for evaluating nanoparticles toxicity and fate. Environ Toxicol Chem © 2013 SETAC

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