Fungal biodegradation of a phenylurea herbicide, diuron: structure and toxicity of metabolites

Microbial degradation, organic synthesis and ecotoxicology were used to inv estigate the fate of diuron after spreading on soils. Quantitative biodegra dation assays were performed with fungal strains, showing that diuron was d egraded but not entirely mineralized. The modifications observed consisted in demethylation of the terminal nitrogen atom. The identified metabolites were synthesized in sufficient amounts to confirm their structures and dete rmine their non-target toxicity using four biotests. The two metabolites ex hibited higher effects than parent diuron. This limited biodegradability an d potential aquatic toxicity suggest that diuron is of higher environmental concern than previously recognized. (C) 2000 Society of Chemical Industry.