Environmental risk assessment of pesticide mixtures under regulation 1107/2009/EC: a regulatory review by the German Federal Environment Agency (UBA)

This paper does review and reflect on the state of implementation of mixture risk assessment in the guidance documents for environmental risk assessment of plant protection products under regulation 1107/2009/EC. In the past years and still on-going, the specific guidance documents for the relevant assessment areas (birds and mammals, aquatic organism, bees and wild pollinators, non-target terrestrial arthropods, soil organism, non-target terrestrial plants) have been under revision. This revision process—being led by the European Food Safety Agency (EFSA)—has substantially brought forward the consideration of the state of the science in mixture hazard and risk assessment in the recently updated guidance documents and proposals for new guidance, respectively. The application of component-based approaches is now advocated as essential new methodology; these do allow for calculating the expectable joint toxicity from toxicity data available for individual mixture components, with the reference concept of concentration addition suggested as reasonable default (tier 1) assumption within tiered approaches for mixture risk assessment. Further elements newly proposed—although differing in the degree considered in the distinct assessment areas—include the counter-checking of measured and calculated mixture toxicity as well as the identification of “drivers” of mixture toxicity/risk. The German Federal Environment Agency (UBA) does acknowledge the progress made in implementation of mixture risk assessment during the past years and is generally committed to the recently updated EFSA guidance documents and proposals for future guidance documents, respectively.