Comparative Impacts of Conventional and Biodegradable Microplastics on Boscalid Behavior and Toxicity in Soil–Earthworm System

The widespread environmental presence of microplastics has led to their increasing co-occurrence with pesticides in agricultural soils, which raises concerns about their potential combined effects on pollutant behavior and toxicity. In this study, we investigated the environmental fate of boscalid and its toxicity to earthworms under co-exposure with two types of microplastics. Both polyethylene microplastics (PE) and polylactic acid microplastics (PLA) significantly enhanced boscalid retention in soil and delayed its degradation. Co-exposure impaired intestinal barrier function, promoted boscalid bioaccumulation, and triggered more severe oxidative stress and metabolic disturbances in earthworms. Notably, differences were observed between PE and PLA in their effects on boscalid behavior and earthworm responses. Our study suggests that microplastics may influence the ecological risk of boscalid through potential carrier effects and biological interface interactions and indicates mechanistic differences between conventional and biodegradable microplastics in modulating pesticide toxicity. These findings offer new insights into the environmental risk assessment of combined pollution.