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.