Assessment of the environmental properties and effects of pesticide degradation products

摘要

When released into the environment, pesticides may be degraded by plants, micro-organisms and chemical processes. Under EU Directive 91/414/EEC the environmental impact of relevant transformation products needs to be assessed. Currently the only approach for assessing the potential risk of a transformation product is to perform a series of experimental investigations. This is a drain on resources. This study is therefore being performed to 1) explore relationships between parent and metabolite toxicity that can be used to identify potentially relevant metabolites in the future; and 2) assess the use of quantitative structure-activity relationships for predicting metabolite toxicity. A large dataset has been compiled containing information on the ecotoxicity of a range of pesticide metabolites and their parent compounds. The dataset has been used to explore relationships between parent and metabolite ecotoxicity and to test quantitative structure-activity relationship (QSAR) techniques. Results obtained to date indicate that, in general, metabolites are of similar or lower toxicity than the parent compounds. A small proportion of metabolites were more toxic. These differences in toxicity could be explained by an enhancement in the uptake of the metabolite compared to the parent (due to changes in hydrophobicity or dissociation constant) or the presence of pesticidal activity in a metabolite. For a large proportion of substances, predictions of ecotoxicity using a QSAR for daphnids were similar toexperimentally-derived data. There were however a large number of substances where toxicity predictions were unreliable.