Dissipation, Bioconcentration and Dietary Risk Assessment of Thiamethoxam and its Metabolites in Agaricus bisporus and Substrates Under Different Application Methods

Summary

This research examined the safety of using a common insecticide (thiamethoxam) in mushroom farming. The study found that applying the pesticide to compost rather than surface soil is safer and leads to fewer residues in mushrooms. The levels found were well below safety limits for human consumption. Impacts on everyday life: – Helps ensure commercially grown mushrooms are safe to eat – Provides guidance for mushroom farmers on safer pesticide application methods – Contributes to food safety monitoring and standards – Supports sustainable agricultural practices – Helps maintain affordable mushroom production while managing pests

Background

Agaricus bisporus is one of the most popular cultivated mushrooms worldwide, with China being the largest producer and exporter. While the mushroom has important nutritional and pharmaceutical benefits, pest control during cultivation is a major challenge. Thiamethoxam (TMX) is a second-generation neonicotinoid insecticide widely used for controlling sciarids, but its safety regarding metabolites and residues requires careful assessment.

Objective

To systematically explore how thiamethoxam (TMX) dissipates and metabolizes in mushrooms and different substrates, and provide guidelines for safe application. Specific aims included: 1) Developing a QuEChERS method for analyzing TMX and its metabolites in A. bisporus ecosystem; 2) Understanding dissipation, metabolism and bioaccumulation characteristics in compost/casing soil systems; 3) Comparing dietary risks between different application methods.

Results

TMX dissipation half-lives were shorter in compost (19.74-28.87 days) compared to casing soil (33.54-42.59 days). Clothianidin was the dominant metabolite in both substrates. When applied to casing soil, only parent TMX was detected in fruiting bodies with low bioconcentration factors (0.0003-0.0009). No residues were detected in fruiting bodies when TMX was applied to compost. Both chronic and acute dietary risk assessments showed acceptable safety levels.

Conclusion

The application of TMX in compost showed faster degradation and was safer than application in casing soil for A. bisporus cultivation. Dietary risk assessments indicated that TMX application at dosages under 50 mg/kg in either substrate poses no significant risks to consumers. The study provides scientific evidence for safe TMX application in mushroom cultivation.
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