Evaluation of the Effects of Nano-Metal Oxide (Nano-SiO2, Nano-HfO2, Nano-CeO2, Nano-Ta2O5)

Nano-metal oxides (NMO) are the most commonly used nanomaterials in the manufacturing field, as well as in medicine, textiles, agriculture, and personal care. Because of their toxic potentials, they can accumulate in various environments and cause negative effects. The evaluation of toxicity risk is a critical issue. Four separate NMOs (nano-SiO2, nano-HfO2, nano-CeO2, nano-Ta2O5) were investigated in this study to see whether they had any toxic effects on specific species (Vibrio fischeri – bioluminescence bacteria, Chlorella – algae, Daphnia magna – Crustacea).The EC50 values were determined from the inhibitions of NMOs versus exposure period and were agreed as values affecting/inhibiting 50% of the species (30 min, 48 h and 72 h). A bioluminescent marine bacterium, Vibrio fischeri, was used in the Microtox assay to assess the toxicity of these NMOs. The most toxic NMO to Vibrio fischeri was nano-Ta2O5, which had the lowest EC50 value (31.457 mg/l). The reduction in growth of Chlorella sp. exposed to NMOs was used to assess the algae growth inhibition test.Chlorella sp. is highly susceptible to all NMOs (EC50= 7.35 mg/l; nano-HfO2 EC50= 2,94 mg/l; nano-SiO2 EC50= 1.4 mg/l; nano-Ta2O5 EC50= 2.4 mg/l) due to the algal cells' simple entrapment of NMOs, resulting in high inhibitions. Acute toxicity tests were carried out on Daphnia magna for 48 hours with rising NMO concentrations. Nano-SiO2 is the most toxic NMO to D. magna, with the lowest EC50 value (10.01 mg/l) after 48 hours of exposure.

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