Degradation products of a phenylurea herbicide, diuron: Synthesis, ecotoxicity, and biotransformation

The degradation products of diuron (photoproducts and metabolites), already described in the literature, were synthesized in order to carry out furthe r investigations. Their ecotoxicity was determined using the standardized M icrotox (R) test, and most of the derivatives presented a nontarget toxicit y higher than that of diuron. Therefore, the biotransformation of these com pounds was tested with four fungal strains and a bacterial strain, which we re known to be efficient for diuron transformation. With the exception of t he 3,4-dichlorophenylurea, all the degradation products underwent other tra nsformations with most of the strains tested, but no mineralization was obs erved. For many of them, the biodegradation compound for which the toxicity was important was 3,4-dichlorophenylurea. This study underlines the import ance of knowing the nature of the degradation products, which has to be kep t in mind while analyzing natural water samples or soil samples.