One of the pivotal environmental fate studies supporting pesticide registration is the soil metabolism study designed to determine the route and rate of degradation in soils, to investigate the degradation products formed, and to propose the soil degradation pathway of the pesticides. According to EU regulations, the degradation rate and adsorption parameters of the major degradation products formed from soil metabolism studies are needed as input parameters for environmental exposure assessment. Soil metabolism studies are often conducted with radio-labeled test substances to facilitate the metabolite identification, to quantify the non-extractable bound residues and to confirm the material balances. However, for soil rate of degradation studies, especially for soil degradation products, both radio-labeled and non-labeled test substances have been used in the industry supporting pesticide registration. In this presentation, the pros and cons of conducting studies with cold and radio-labeled test substances are investigated. The degradation half-life (DT<sub>50</sub>) of a compound derived from 4 soils dosed with radio-labeled material and 16 soils dosed with non-labeled material are compared and their impacts on environmental exposure assessment are discussed.

Evaluation of end points derived from soil rate of degradation studies dosed with cold and radio-labeled test substances and their impact on exposure assessment

2019 Fall National Meeting

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