An AOP is an analytical construct that describes a sequential chain of causally linked events at different levels of biological organisation that lead to an adverse health or ecotoxicological effect (see figure below). AOPs are the central element of a toxicological knowledge framework being built to support chemical risk assessment based on mechanistic reasoning.
Adverse Outcome Pathways
The OECD has been helping countries to make better use of increased knowledge of how chemicals induce adverse effects in humans and wildlife, through Adverse Outcome Pathways (AOPs).
Key links
Adverse Outcome Pathways
Schematic representation of the AOP illustrated with reference to a number of pathways
AOP development programme
The Advisory Group on Emerging Science in Chemicals Assessment (ESCA) oversees the essential elements of the AOP Programme. This group works towards the development of AOPs with the support of and in close collaboration with the AOP-KB Coordination Group and of the Society for the Advancement of AOPs (SAAOP). The latter serves as the primary interface between the OECD ESCA and the broader AOP community of practice.
- General Guidance on AOP is provided in the Guidance Document on Developing and Assessing Adverse Outcome Pathways
- A new online version of the Developers' Handbook is available from the AOP Wiki. It provides practical guidance and should be followed for developing an AOP in the AOP-Wiki platform.
- AOP-relevant projects can be proposed by scientists from OECD member countries for review by ESCA. Complete the form to submit an AOP project proposal. The AOP-Wiki is regularly updated to provide the OECD status of each AOP.
- The Guidance Document for the scientific review of Adverse Outcome Pathways provides OECD standards for the scientific review of an AOP in the AOP Wiki.
- The AOP-Wiki also provides AOP-related training resources, i.e. online training and training events.
Co-operation on scientific review and AOP publication
The OECD is developing co-operation with scientific journals for the review and publication of AOPs.
This co-operation is formalised in the signature of a Memorandum of Understanding (MOU), conditions of which are summarised here.
Scientific journal signatories take part in the scientific review of AOPs relevant to their field of expertise, with the view to achieve the following common objectives:
- increase the rate of AOP scientific reviews
- offer the opportunity for journals to get more submissions for scientific articles
- enable a double recognition through AOP publications in the scientific literature and at the OECD
The following journals have already signed an MOU with the OECD:
- Environmental Toxicology and Chemistry (ET&C), a journal published by the Society of Environmental Toxicology and Chemistry (SETAC)
- AOP Pathways and Predictions: Virtual issue - Environmental and Molecular Mutagenesis (EMM), the journal of the Environmental Mutagenesis and Genomics Society
- Alternatives to Animal Experimentation (ALTEX)
- Cancers, a journal published by MDPI
AOP knowledge base and tools
The OECD's AOP Knowledge Base, continuously developed and refined, consists of a suite of web-based tools which aims to bring together knowledge and evidence pertaining to how chemicals induce adverse effects on humans and/or ecosystems, therefore providing a focal point for AOP development and dissemination.
eAOP Portal
The eAOP Portal is the main entry point of the AOP Knowledge Base. The Portal enables search by keywords in AOP titles and key events in the AOP Wiki. It houses the status of all AOPs in the OECD Work Plan and the official copy of OECD endorsed AOPs.
AOP Wiki
The AOP Wiki is the primary user interface for all AOPs developed as part of the OECD AOP Development Programme and provides a system that organises, via crowd-sourcing, the available knowledge and published research into a description of individual pathways, using a user-friendly Wiki interface. Information on AOP is collected in a qualitative and narrative way.
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