OECD Series on Adverse Outcome Pathways

An Adverse Outcome Pathway (AOP) describes a logical sequence of causally linked events at different levels of biological organisation, which follows exposure to a stressor and leads to an adverse health effect in humans or wildlife. AOPs are the central element of a toxicological knowledge framework, promoted by member countries through OECD, built to support chemical risk assessment based on mechanistic reasoning. These AOPs are available in the AOP-Wiki, an interactive and virtual encyclopaedia for AOP development. Following their development and review, the endorsed AOPs are published in the OECD Series on Adverse Outcome Pathways. As scientific knowledge progresses, the publication of an AOP in this series does not preclude regular updates or new contributions to a given AOP. While the AOP-Wiki is a dynamic tool, only impactful changes to the AOP will be reflected in subsequent updates of the published AOP.


Users' Handbook supplement to the Guidance Document for developing and assessing Adverse Outcome Pathways

This document is a supplement to the Guidance Document for developing and assessing Adverse Outcome Pathways (AOPs). It provides focused and practical instructions for both AOP developers and reviewers and is intended to assist in identifying, organising and evaluating critical information on key events (KEs) as well as linkages between KEs within the AOP (i.e. AOP development). It also provides explicit guidance on how to assess the weight of evidence (WoE) supporting the overall AOP and its relevance for life stage, sex and taxonomy (i.e. AOP evaluation). This handbook is not intended to provide a review or summary of the literature informing the AOP concept. Instead, it focuses on practical aspects of AOP development and assessment. It has been developed by a subgroup of the OECD Extended Advisory Group for Molecular Screening and Toxicogenomics (EAGMST).


Keywords: AOP assessment, handbook, AOP development, weight of evidence
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