Assessing the population relevance of endocrine disrupting effects for non-target vertebrates exposed to plant protection products.

The European Commission intends to protect vertebrate wildlife populations by regulating Plant Protection Product (PPP) active substances that have endocrine disrupting properties with a hazard-based approach. In this paper we consider how the Commission's hazard-based Regulation and accompanying Guidance can be operationalised to ensure that a technically robust process is used to distinguish between substances with adverse population level effects and those for which it can be demonstrated that adverse effects observed (typically in the laboratory) do not translate into adverse effects at the population level. Our approach is to use population models within the adverse outcome pathway framework to link the non-linear relationship between adverse effects at the individual and population levels in the following way: (1) Use Specific Protection Goals for focal wildlife populations within an ecosystem services framework; (2) Model the effects of changes in population-related inputs on focal species populations using individual-based population models to determine thresholds between negligible and non-negligible (i.e. adverse) population level effects; (3) Compare these thresholds with the relevant endpoints from laboratory toxicity tests to determine whether they are likely to be exceeded at hazard-based limits or the Maximum Tolerated Dose/Concentration from the experimental studies. If the population threshold is not exceeded then the substance should not be classified as an endocrine disruptor with population-relevant adversity unless there are other lines of evidence within a weight of evidence approach to challenge this. We believe this approach is scientifically robust whilst still addressing the political and legal requirement for a hazard-based assessment. This article is protected by copyright. All rights reserved.