Ecotoxicity of herbicide diuron on the earthworm Eisenia fetida: oxidative stress, histopathology, and DNA damage

Diuron is a widely used herbicide worldwide, and its toxic effects on aquatic and amphibious organisms have received extensive concerns. However, little information is available regarding the impacts of diuron on non-target soil organism earthworm. Thus, this work investigated the toxic effects of environmentally relevant concentrations (i.e., 0.05, 0.5, and 5.0 mg/kg soil) of diuron on earthworm Eisenia fetida according to multiple biomarkers including oxidative stress, DNA damage, and histopathology. Results showed that diuron significantly induced the production of reactive oxygen species (ROS) and presented a dose-effect relationship (R-2 > 0.6) during the first 21 days of exposure. On the seventh day, the activity of superoxide dismutase (SOD) in E. fetida exposed to 0.05, 0.5, and 5.0 mg/kg of diuron decreased by 3.3%, 17.8%, and 37.4% with respect to the control, respectively, while the activities of catalase (CAT), peroxidase (POD), and glutathione S-transferase (GST), as well as the content of malondialdehyde (MDA) increased to varying degrees. Diuron resulted in low damage of coelomocyte DNA in E. fetida, while no tissue damage was observed on days 7 and 14. At the end of exposure period (28 d), except for ROS, all other biomarkers in the diuron-treated groups were restored to the control level. Integrated biological response (IBR) showed that ROS and GST are sensitive biomarkers to monitor the potential toxicity effect of diuron on E. fetida. The results of this study provide valuable information for risk assessment of diuron on soil ecosystem health.