AOPs (adverse outcome pathways) delineate the documented, plausible, and testable processes by which a chemical induces molecular perturbations (Molecular Initiating Events) and the associated biological responses that describe how the molecular perturbations cause effects at the subcellular, cellular, tissue, organ, whole animal, and population levels of observation.
Source: T.W. Schutz (OECD), What is the Adverse Outcome Pathway (AOP) concept?

An adverse outcome pathway (AOP) is the sequence of events from the chemical structure of a target chemical or group of similar chemicals through the molecular initiating event to an in vivo outcome of interest. Each AOP represents the existing knowledge concerning the linkage(s) between a molecular initiating event, intermediate events and an adverse outcome at the individual or population level.
Source: OECD, The Adverse Outcome Pathway for Skin Sensitisation Initiated by Covalent Binding to Proteins - Part 1: Scientific Evidence - Series on Testing and Assessment No.168, 2012, page 18.


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