Genotoxic, mutagenic and behavioral effects of flumioxazin, s-metolachlor, and their mixture: a multilevel ecotoxicological assessment using Eisenia fetida

Abstract

Flumioxazin and S-metolachlor are herbicides commonly used in soybean cultivation, often applied together or found concurrently in the environment due to their persistence. This study aimed to assess the toxicity of Flumioxazin, S-metolachlor, and their commercial mixture (Apresa®) on Eisenia fetida, an earthworm species used as a terrestrial bioindicator. Organisms were exposed for 7 and 14 days to different concentrations of the herbicides: Flumioxazin (half dose: 113.4 mg/350 g of soil; field dose: 226.8 mg; double dose: 453.6 mg), S-metolachlor (0.25, 340.2, and 680.4 mg/350 g of soil), and commercial mixture (113.4, 226.8, and 453.6 mg/350 g of soil). Lethality parameters (survival and biomass), behavioral responses (avoidance), and genotoxic effects (comet assay and micronucleus test) were evaluated. None of the tested herbicide concentrations caused significant mortality. No significant differences were detected in biomass across treatments. However, significant avoidance was noted at the field and double doses of S-metolachlor, as well as at all concentrations of the commercial mixture. The comet assay revealed DNA damage at field doses of Flumioxazine and S-metolachlor, as well as at field and double doses for the mixture. The micronucleus test indicated mutagenic effects at the lowest dose of Flumioxazin, at the field and double doses of S-metolachlor, and at both the half and double doses of the commercial mixture. These results suggest that herbicides, individually and in combination, pose genotoxic risks even at low concentrations, with the mixture potentially enhancing the observed effects compared to single compounds. The study underscores the importance of reassessing herbicide application strategies to safeguard soil organisms and environmental health.