Conducting groundwater monitoring studies in Europe for pesticide active substances and their metabolites in the context of Regulation (EC) 1107/2009

Groundwater monitoring is recommended as a higher-tier option in the regulatory groundwater assessment of crop protection products in the European Union. However, to date little guidance has been provided on the study designs. The SETAC EMAG-Pest GW group (a mixture of regulatory, academic, and industry scientists) was created in 2015 to establish scientific recommendations for conducting such studies. This report provides recommendations for study designs and study procedures made by the Society of Environmental Toxicology and Chemistry (SETAC) Environmental Monitoring Advisory Group on Pesticides (EMAG-Pest). Because of the need to assess the vulnerability to leaching in both site selection and extrapolating study results, information on assessing vulnerability to leaching is also a major topic in this report. The design of groundwater monitoring studies must consider to which groundwater the groundwater quality standard is applicable and the associated spatial and temporal aspects of its application, the objective of the study, the properties of the active substance and its metabolites, and site characteristics. This limits the applicability of standardised study designs. The effect of the choice of groundwater to which the water quality guideline is applied on study design is illustrated and examples of actual study designs are presented.