Insights into the chronic toxicity and mechanisms of fluorine-containing pesticides on earthworms

Fluorine-containing pesticides are widely applied in agriculture, yet their chronic ecotoxic effects on soil organisms remain understudied. This study evaluated the toxicity of three pesticides on Eisenia fetida through a 56-day soil exposure at gradient concentrations (fluxapyroxad:C1:62.5,C2:250, C3:1000 mg a.i./kg dry soil; fluopyram: C4:15.6, C5:62.5, C6:250 mg a.i./kg dry soil; bixafen: C7:125, C8:500, C9:1000 mg a.i./kg dry soil). Biomarkers of oxidative stress (ROS, MDA),antioxidant enzymes (SOD, CAT, GST), DNA damage (8-OHdG), mitochondrial function (SDH), and histopathology were assessed periodically. The results indicated that there was no significant difference in growth and reproduction between the low concentration groups and the control group(P > 0.05), while higher doses lead to weight loss (up to 40 % inhibition) and reduced offspring, likely due to energy depletion and reproductive organ damage. ROS and MDA increased dose- and time-dependently, with antioxidant enzymes showing initial activation followed by suppression, indicating antioxidant system failure. DNA damage (8-OHdG) escalated with concentration, linked to ROS overproduction. SDH activity declined significantly at high doses, reflecting mitochondrial dysfunction. Histopathology revealed epidermal shedding, intestinal damage, and seminal vesicle disorganization under high-exposure conditions. Integrated biomarker response (IBR) analysis confirmed dose-time-dependent toxicity, with maximal ecological risk in high-concentration groups. These findings highlight the mechanisms of fluorine-containing pesticide toxicity in earthworms, emphasizing their potential to disrupt soil ecosystems. This study provides critical data for ecological risk assessments of agrochemicals.