Asian Basic and Applied Research Journal

Nano-metal oxides (NMO) are the most used nanomaterials in the industrial sectors as well as in the medicine, in the textile and in the agricultural and in the personal care areas. They can be accumulated in different environment and cause adverse effect due to their toxic potentials. The risk assessment on toxicity is very important issue. In this study, four different NMOs (nano-SiO₂, nano-HfO₂, nano-CeO₂, nano-Ta₂O₅) were investigated to detect their toxic effects on certain organisms (Vibrio fischeri – bioluminescence bacteria, Chlorella – Algae, Daphnia magna – Crustacea. The values affecting/inhibiting the 50% of the organisms were accepted as EC₅₀ values and these values were calculated from the inhibitions of NMOs versus exposure time (30 min, 48 h and 72 h). In the Microtox assay, a bioluminescent marine bacterium, Vibrio fischeri, was used to evaluate the toxicity of these NMOs. The most toxic NMO was nano-Ta₂O₅ to Vibrio fischeri because of the lowest EC₅₀ value (31.457 mg/l). Algae growth inhibition test was evaluated as the reduction of growth of Chlorella sp. exposed to NMOs. Chlorella sp. is very sensitive to all NMOs (nano-CeO₂ EC₅₀= 7.35 mg/l; nano-HfO₂ EC₅₀= 2,94 mg/l; nano-SiO₂ EC₅₀= 1.4 mg/l and nano-Ta₂O₅ EC₅₀= 2.4 mg/l) due to easily entrapping of NMOs by the algal cells resulting in high inhibitions. Acute toxicity assays with Daphnia magna were conducted for 48 h with increasing NMOs concentrations. The most toxic NMO is nano-SiO₂ to D. magna due to the lowest EC₅₀ value (10.01 mg/l) after 48 h exposure.