Improving environmental risk assessment of pesticides: the need for advanced spray drift models in EU regulatory framework Exploring modelling approaches for spray drift deposition for upward and sideways spraying for use in off‐crop exposure assessm

Abstract EU Regulation 1107/2009 aims at ensuring that pesticides do not pose unacceptable risks to humans, animals, or the environment. As non‐target organisms can be adversely affected by pesticide use, their protection is pivotal. Therefore, EU Regulation 1107/2009 requires that the risks to non‐target organisms are determined when assessing a pesticide application for the authorisation of a plant protection product. Off‐target drift is a major exposure route for non‐target organisms living in the field‐adjacent habitats. Spray drift deposition values currently used in the EU regulatory environmental exposure assessment rely on data from outdated experiments conducted in Germany, which may not fully represent various meteorological and crop conditions across Europe. Modelling can be an alternative to experiment‐based spray drift curves. However, for EU regulatory purposes, a ready‐to‐use model that predicts spray drift depositions for upward and sideways sprayed crops is currently not available. Recently, the statistical model SPEXUS has been developed for predicting spray drift deposition from upward and sideways spraying in Dutch apple orchards. The model is based on a wide range of experimental drift deposits that reflect conditions in the Netherlands but can be adapted for other fruit crops and other climate zones by using appropriate relationships based on crop development stage and local weather conditions. The broader validity of the model was tested by comparing the results of SPEXUS with data obtained from EU datasets. In addition, the currently used German Ganzelmeier‐Rautmann deposition curves were compared to the same EU datasets. The results showed that the Ganzelmeier‐Rautmann curves both underestimated and overestimated the spray drift deposits. However, overestimation — considered a conservative approach from a regulatory perspective — was the most frequently observed outcome. As a result, it seems most practical, for now, to continue using the Ganzelmeier‐Rautmann spray drift curves for upward and sideways sprayed crops. However, advanced models like SPEXUS offer advantages by accounting for variable weather conditions, application techniques and crop types and structures. The recommendation is to extend SPEXUS to other crops and cultivation techniques across Europe. This would require a wide range of spray drift data from different European climate zones, cropping systems and a variety of spray drift techniques. To obtain these data to refine, expand and validate the model it is advised to engage with agricultural research institutes and universities across the EU that are involved in spray drift research.