Enantioselective residues and toxicity effects of the chiral triazole fungicide hexaconazole in earthworms (Eisenia fetida).

The enantioselective toxic effect and environmental behavior of chiral pesticides have attracted increasing research attention. In this study, the enantioselective toxicity and residues of hexaconazole (HEX) in earthworms (Eisenia fetida) were investigated. In the present study, significant enantioselective degradation characteristics were observed in artificial soil with the R-enantiomer preferentially degrading (p < 0.05); however, no significant enantioselective bioaccumulation was observed in the earthworms (p > 0.05). The acute toxicity of S-(+)-HEX was higher than that of R-(-)-HEX in earthworms, with 48-h LC values of 8.62 and 22.35 μg/cm, respectively. At 25 mg/kg, enantiospecific induction of oxidative stress was observed in earthworms; moreover, S-(+)-HEX had a greater influence on the contents of malonaldehyde, cytochrome P450, and 8-hydroxy-2-deoxyguanosine than R-(-)-HEX. These results were consistent with those of the enrichment analysis of differentially expressed genes. The transcriptome sequencing results showed that S-(+)-HEX had a more significant influence on steroid biosynthesis, arachidonic acid metabolism, and cell cycle processes than R-(-)-HEX, leading to abnormal biological function activities. These results indicate that S-(+)-HEX may pose a higher risk to soil organisms than R-(-)-HEX. This study suggests that the environmental risk of chiral pesticides to nontarget organisms should be assessed at the enantiomeric level.