A Standard Operating Procedure (SOP) for calculation of degradation kinetics and the determination of a representative half-life was developed and was used in a one-year pilot study in EPA's Office of Pesticide Programs . The SOP is a supplement to the already completed NAFTA guidance titled, �Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media�. The guidance specifies the conditions under which a first-order model can be used to represent pesticide degradation data in exposure assessments and provides a procedure to determine a representative rate when the data deviate from a first-order model. The models used to describe degradation kinetics are the single first order (SFO), the indeterminate order rate equation (IORE), and double first order in parallel (DFOP) models.  As part of the one-year evaluation, the following classes of datasets were identified as needing further analysis: 1) an IORE parameter 'N' of less than 1, 2) a DFOP model that did not converge or gave a negative DT50 value, 3) a DFOP parameter 'F' not between 0 and 1, 4) a SFO DT50 not selected as the representative model input value for an abiotic study, or 5) a DT50 not observed during the study. As a result of the evaluation, changes to the SOP are recommended to improve analysis of the degradation data.

Standard operating procedure for calculating degradation kinetics in EPA's Office of Pesticide Programs

248th National Meeting (2014)

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