High time to Update Statistical Guidance in Ecotoxicology-A Workshop Synthesis on the Revision of OECD Document No.54.

OECD document No. 54 provides assistance on the statistical analysis of ecotoxicity data to ensure scientifically robust and globally harmonized evaluations of biotests across various regions and regulatory sectors. However, some of the recommended methodologies are outdated due to significant advances in statistical techniques and regulatory requirements. In addition, practitioners have been calling for a more user-friendly structure, aiming to facilitate data analysis for users without extensive statistical expertise. To address these concerns, a research project was initiated by the German Environment Agency with the aim to update OECD No. 54. As part of this project, a dedicated workshop was convened to gather expert perspectives from different sectors (incl. academic, industry and regulators) on revision needs of OECD No. 54 aiming to better reflect current scientific and regulatory standards. Key debates of the workshop included restructuring the document to improve user accessibility, clarifying terminology, addressing methodological gaps such as assessment approaches for ordinal and count data, and incorporating state-of-the-art modelling approaches for time-dependent toxicity assessment. In addition, the integration of modern statistical practices in hypothesis testing and the provision of clearer guidance on model selection for dose-response analyses were identified as crucial needs for updating OECD No. 54. This synthesis captures the workshop's contributions and recommendations, outlining a roadmap for the revision of OECD No. 54, and highlights the ongoing collaboration with an ISO working group to ensure consistency of standards across regulatory frameworks.