Defense responses in earthworms (Eisenia fetida) exposed to low-density polyethylene microplastics in soils

The potential threats of microplastics to global health are a new problem. However, little is known about the influence of microplastics on soil organisms. Here, we investigated the effects of low-density polyethylene (LDPE, < 400 μm) on earthworms (Eisenia fetida) under different concentrations (0.1, 0.25, 0.5, 1.0, 1.5 g/kg dry) with three replicates in artificial soil. Results showed that surface damage of earthworms was observed at the concentration of 1.5 g/kg LDPE after exposure 28 days. The microplastics were ingested in a dose-response manner. Smaller sizes of LDPE microplastics were found in the casts of E. fetida, and approximately 30% of the microplastics egested (size < 100 μm) were increased compared with initial microplastics in the soil. The catalase activity and malondialdehyde content increased significantly at the concentration of 1.0 g/kg LDPE after exposure 28 days, and acetylcholine esterase was significantly stimulated at concentrations of 1.5 and 1.0 g/kg LDPE on days 21 and 28, respectively. The results of this study demonstrate the potential risk of LDPE microplastics to E. fetida and may provide a reference for the impact of microplastics on terrestrial creatures.