Selecting a pesticide leaching indicator for integration into a decision support system at farm scale

The recent EU agricultural policy emphasises enhancing the sustainability of farming by promoting organic practices and the responsible management of chemical inputs such as pesticides. In this context, it is essential to provide farmers with reliable pesticide risk indicators that can be integrated into decision support systems, enabling them to identify optimal pest management strategies, minimise environmental impact, and monitor progress in improving farm-level sustainability. This paper outlines our approach to selecting the most appropriate pesticide risk indicator for assessing the potential leachability of pesticides into groundwater. For 46 active substances, we initially retrieved relevant data from the European Food Safety Authority (EFSA) Conclusions documents, including Predicted Environmental Concentrations in groundwater (PECgw). These values, considered of high quality, serve as reference points in the EU environmental risk assessment procedures for pesticide authorisation. We then compared these PECgw values with results obtained from two indicators and a metamodel selected from the literature: the Groundwater Ubiquity Score (GUS) index, the Attenuation Factor (AF) index, and the metamodel used by the European Medicines Agency for the authorisation of veterinary pharmaceuticals. The analysis revealed that while all three methods generally aligned well with the PECgw values reported in the EFSA documents, the AF index demonstrated the highest predictive capability. Furthermore, the AF index was more consistent with criteria such as ease of application and applicability across various geographical contexts. Therefore, the AF index was identified as the optimal choice for integration into decision support systems.