Evaluation of Cerium-oxide (CeO2) nanoparticle toxicity to freshwater midge Chironomus riparius (Diptera, Chironomidae) – potential biomarkers

Abstract

The toxicity of Cerium-oxide nanoparticles (nano-CeO2) on the freshwater midge Chironomus riparius, Meigen, 1804 was assessed by observing several biomarkers, from molecular to the ecological level. Experiments were designed using measured concentrations of nano-CeO2 in the sediment, according to the OECD guidelines for testing of chemicals, in the laboratory setup. The full characterization of the CeO2 nanoparticles was made and the concentrations of 2.5, 25, 250 and 2500 mg of nano-CeO2 per kg of sediment were tested. Following parameters were investigated: nano-CeO2 intake by the larvae, oxidative stress parameters, in vivo genotoxic effect, geometric morphometry changes and life trait parameters (developmental time, emergence, mortality and survival rate). The Spearman rho test showed that the increase of nano-CeO2 content in the chironomid larvae was highly correlated (rho=0.73, p<0.01) with the increase of nano-CeO2 in the sediments. At the lower biological level, toxicity was detected through significant (p < 0.05) DNA damage in the midges exposed to higher nano-CeO2 levels (tested by one-way ANOVA). The toxicity was not detected at the developmental level, causing no observable effects on life traits. In addition, investigated oxidative stress parameters showed no significant differences between the treatments. There is a need for further investigation in order to understand causal relationships between molecular and higher-level responses to nano-CeO2 exposure. Nevertheless, obtained results indicate that C. riparius could be used as bioindicator, providing valuable information for nano-CeO2 risk assessment in freshwaters.