Mix-Tool: An Edge-of-Field Approach to Predict Pesticide Mixtures of Concern in Surface Water From Agricultural Crops

Nowadays, current regulation on the authorization of Plant Protection Products (PPPs) in the EU is limited to the evaluation of ecological risks for single active substances (a.s.) they contain. However, plant protection treatments in agriculture often consist of PPPs already containing more than one a.s.; moreover, each cropped field receives multiple applications per year leading to complex pesticide mixtures in the environment. Different transport processes lead to a multitude of heterogeneous and potentially toxic substances that, for example, may reach water bodies, and act simultaneously on natural freshwater ecosystems. In this context, the development of methodologies and tools to manage risks of pesticides mixtures is imperative to improve the current ecological risk assessment procedures and to avoid further deterioration of ecological quality of natural resources. This paper suggests new procedures for identifying pesticide mixtures of potential concern released from agricultural crops in surface water. The approach follows the EU regulatory context for the authorization of PPPs in the market (edge-of field risk assessment) and requires the use of FOCUS models (step 3 and 4) for calculating the concentrations in surface water of mixture components on a daily basis. Moreover, it uses the Concentration Addition models to calculate the toxic potency of the pesticide mixtures released by a treated crop. In order to implement this procedure, we developed a simple Microsoft-Excel-based tool. We also considered two case studies (maize and apple tree), representative of Italian agricultural scenarios for annual and perennial crops. Moreover, we compared results with three-years monitoring data of surface water bodies of Lombardia region (Northern Italy) where the two crops are largely present.