Predicting the environmental fate and ecotoxicological and toxicological effects of pesticide transformation products

Following the application of pesticides during normal agricultural practice these compounds can degrade to form transformation products. When assessing the risks posed by pesticides it is important to include any additional risks posed by these compounds. Current guidance within the EU suggests that data requirements for transformation products during the risk assessment do not necessarily need to be addressed with experimental studies but alternative techniques can be explored and used. Therefore the aim of this research was to investigate and develop pragmatic approaches for assessing the fate and effects of transformation products in the absence of experimentally determined data. Approaches designed to provide information on the physico-chemical properties, environmental parameters, ecotoxicology and toxicology of pesticide transformation products are explored and evaluated, and recommendations made on how to obtain the most appropriate estimates of these factors. Hydrophobicity, dissociation constant, soil sorption, daphnid aquatic ecotoxicology and rat oral lethality can all be estimated with confidence. Moreover, approaches were developed to I) indicate whether a transformation product may exhibit pesticidal activity and subsequently estimate its acute aquatic ecotoxicity in the absence of experimental data, 2) combine well known techniques and experimental data to obtain estimates of transformation product mutagenicity with limited risk of obtaining false negatives and 3) prioritise transformation products of most concern to drinking water supplies and its consumers. Overall, recommendations are made throughout this thesis on appropriate approaches and methods for generating estimates of transformation product properties, ecotoxicity and toxicity for use in risk assessment and prioritisation frameworks.