Evaluating plant residue decline data with KinGUII and TREC: results from case studies involving also non-SFO kinetic models

Background Foliage residue decline data are used to refine the risk assessment for herbivorous birds and mammals foraging in fields treated with plant protection products. For evaluation, current EFSA guidance has a clear focus on single-first order (SFO) kinetic models. However, other kinetic models are well established in other areas of environmental risk evaluations (e.g., soil residue assessment), and easy-to-use calculation tools have become available now. We provide case studies with 6 fungicides how such evaluations can be conducted with two of these tools (KinGUII and TREC) that have been developed by Bayer. Results SFO kinetics provided the best fits only for 13 of 36 residue decline studies conducted in a standardized design under field conditions. Biphasic models (double first order in parallel, hockey stick) were often superior and sometimes more conservative for risk assessment. The additional effort is manageable when using software such as KinGUII and TREC, and appears justified by the more reliable outcome of the evaluations. Conclusions Further research would be useful to better assess the extent to which non-SFO better fits foliage residue decline, but our study suggests that it may be a significant proportion. Therefore, we encourage the use of biphasic models in the regulatory risk assessment for herbivorous birds and mammals, in the ongoing revision of the European Food Safety Authority (EFSA) guidance document from 2009.