Implementing Normal Operating Range Concepts for Pesticide Environmental Risk Assessments: Insights, Challenges, and...

The Normal Operating Range (NOR) is defined as the natural variability observed in the properties of organisms, their populations and communities, driven by various biological and environmental factors. Although still in the exploration phase within pesticide environmental risk assessment (ERA) frameworks, NOR concepts present an opportunity to provide ecological context to effect assessments and support the operationalization of specific protection goals. Discussions from an expert workshop explored possibilities for NOR derivation and applicability across organism groups, highlighting potential benefits and key challenges. While recent efforts suggest NOR-based approaches could enhance decision making in pesticide ERA, key challenges remain, including defining fit-for-purpose effect thresholds, ensuring approach consistency across ecological contexts, and addressing data limitations. Establishing NORs in regulatory practice will require stakeholder collaborations for improved data accessibility, standardized statistical methodologies, and a clear framework for integrating natural variability into decision making processes. Ecological modelling could support identifying sources of variability, helping contextualize observed effects and inform risk characterization based on regulatory thresholds. A harmonized approach that integrates empirical data and transparent statistical and computational methodologies will be essential for the successful implementation of NOR concepts in pesticide ERA.