In 2016, the Organization for Economic Cooperation and Development’s (OECD) Working Party on Manufactured Nanomaterials (WPMN) included the Advancing Adverse Outcome Pathway (AOP) Development for Nanomaterial Risk Assessment and Categorization (NanoAOP) project in its program of work.  The objective of the project is to contribute to the future development and application of AOPs for manufactured nanomaterial regulatory decision making by following the principles established by the OECD Extended Advisory Group on Molecular Screening and Toxicogenomics (EAGMST).  OECD has published three reports presenting the outcomes of the project:

• Advancing Adverse Outcome Pathway (AOP) Development for Nanomaterial Risk Assessment and Categorisation Part 1: Final Project Report and Recommendations with Methodology to Prioritise Key Events (KEs) Relevant for Manufactured Nanomaterials:  The report reviews the scope of the project, its development, and summary of the main conclusions.  The report includes a methodology to identify, analyze, and evaluate existing nanotoxicology literature with the objective to prioritize key events relevant for manufactured nanomaterials;

• Advancing Adverse Outcome Pathway (AOP) Development for Nanomaterial Risk Assessment and Categorisation Part 2: Case Study on Tissue Injury:  This report presents a case study focused on a specific key event in the inflammation pathway to analyze the empirical evidence and contribute to the development of a knowledge base to inform AOP development and assessment for manufactured nanomaterials; and

• Advancing Adverse Outcome Pathway (AOP) Development for Nanomaterial Risk Assessment and Categorisation Part 3: Workshop Report and Recommendations:  The report from the OECD workshop Advancing AOP Development for Nanomaterial Risk Assessment and Categorization, which was organized in collaboration with the European Union (EU) Horizon 2020 projects SmartNanoTox and Physiologically Anchored Tools for Realistic nanOmateriaL hazard aSsessment (PATROLS).  At the workshop, stakeholders had an opportunity to provide feedback on the methodology proposed, as well as on the case study, and to reach consensus on areas that could be further explored in the short, medium, and long term.