The effect of TiO2NPs on cloransulam-methyl toxicity to earthworm (Eisenia fetida).

Cloransulam-methyl is a new herbicide and has broad application prospect. However, the effect of cloransulam-methyl on earthworm have yet to be clarified. As more and more titanium dioxide nanoparticles (TiO2NPs) enter the soil, cloransulam-methyl and TiO2NPs have a risk of co-exposure, but the effect of TiO2NPs on cloransulam-methyl toxicity is unknown. In the study, the ecotoxicity of cloransulam-methyl (0.1, 1 mg kg-1) on earthworm and the effect of TiO2NPs (10 mg kg-1) on cloransulam-methyl toxicity was investigated after exposure for 28 and 56 d. Exposure tests showed cloransulam-methyl and cloransulam-methyl + TiO2NPs promoted the accumulation of reactive oxygen species, malondialdehyde and 8-hydroxydeoxyguanosine, increased the activities of superoxide dismutase and catalase, resulted in lipid peroxidation and DNA damage. Besides, the results at the genetic level showed cloransulam-methyl and cloransulam-methyl + TiO2NPs altered the expression of physiologically-related genes, which demonstrated that cloransulam-methyl and cloransulam-methyl + TiO2NPs induced oxidative stress and cell apoptosis, and disturbed the normal reproduction in earthworm. The results of comprehensive toxicity comparison indicated cloransulam-methyl and TiO2NPs co-exposure has higher toxicity compared to cloransulam single exposure. Our results suggest that TiO2NPs can enhance the toxicity of cloransulam-methyl on Eisenia fetida in terms of oxidative stress, cell apoptosis and reproduction aspects. Based on above studies, it is of great importance for evaluating the risk of cloransulam-methyl co-exposure with TiO2NPs in soil.