ObjectiveThe goal of this study was to evaluate the degradation of fenpropathrin in soil and its effects on earthworms, as well as to establish a foundation for a full environmental risk assessment of fenpropathrin.MethodHigh performance liquid chromatography was used to identify the bioaccumulation of fenpropathrin and the major metabolite, 3-phenoxybenzoic acid, then soil exposure tests were used to assess the toxicity of fenpropathrin to earthworms.Result(1) Fenpropathrin decomposed four times more quickly in unsterilized soil than in sterilized soil and more quickly in alkaline soil than in acidic soil, suggesting that microorganisms and pH were the main factors affecting the degradation rate of fenpropathrin in soil. Moreover, during the decomposition process, the synthesis of its primary metabolite, 3-phenoxybenzoic acid, was discovered. (2) Fenpropathrin content in earthworms increased, then dropped, with a maximum bioconcentration factor of 0.3.(3) The subacute toxicity data showed that after 14 d exposure to high doses (5 mg·kg^-1) of fenpropathrin, the protein content in earthworms was significantly reduced (P < 0.05). Also, the cytochrome P450 (CYP450), carboxylesterase (CarE), glutathione-S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activities and malondialdehyde (MDA) content were significantly increased (P < 0.05) after 14 d of fenpropathrin exposure, and there was a dosage effect.ConclusionThe rate of fenpropathrin degradation in soil was strongly linked with soil characteristics, and fenpropathrin residues in soil could cause subacute toxic effects in earthworms. These findings help in a thorough evaluation of the ecotoxicity and environmental behavior of fenpropathrin in soil, as well as a more solid foundation for pyrethroid pesticide risk assessment.