title: Adverse outcome pathways: a conceptual framework to support ecotoxicology research and risk assessment.
abstract: Ecological risk assessors face increasing demands to assess more chemicals, with greater speed and accuracy, and to do so using fewer resources and experimental animals. New approaches in biological and computational sciences may be able to generate mechanistic information that could help in meeting these challenges. However, to use mechanistic data to support chemical assessments, there is a need for effective translation of this information into endpoints meaningful to ecological risk-effects on survival, development, and reproduction in individual organisms and, by extension, impacts on populations. Here we discuss a framework designed for this purpose, the adverse outcome pathway (AOP). An AOP is a conceptual construct that portrays existing knowledge concerning the linkage between a direct molecular initiating event and an adverse outcome at a biological level of organization relevant to risk assessment. The practical utility of AOPs for ecological risk assessment of chemicals is illustrated using five case examples. The examples demonstrate how the AOP concept can focus toxicity testing in terms of species and endpoint selection, enhance across-chemical extrapolation, and support prediction of mixture effects. The examples also show how AOPs facilitate use of molecular or biochemical endpoints (sometimes referred to as biomarkers) for forecasting chemical impacts on individuals and populations. In the concluding sections of the paper, we discuss how AOPs can help to guide research that supports chemical risk assessments and advocate for the incorporation of this approach into a broader systems biology framework.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804, USA. ankley.gerald@epa.gov
authors.forename: Gerald T
authors.initials: GT
authors.lastname: Ankley
authors.forename: Richard S
authors.initials: RS
authors.lastname: Bennett
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Erickson
authors.forename: Dale J
authors.initials: DJ
authors.lastname: Hoff
authors.forename: Michael W
authors.initials: MW
authors.lastname: Hornung
authors.forename: Rodney D
authors.initials: RD
authors.lastname: Johnson
authors.forename: David R
authors.initials: DR
authors.lastname: Mount
authors.forename: John W
authors.initials: JW
authors.lastname: Nichols
authors.forename: Christine L
authors.initials: CL
authors.lastname: Russom
authors.forename: Patricia K
authors.initials: PK
authors.lastname: Schmieder
authors.forename: Jose A
authors.initials: JA
authors.lastname: Serrrano
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Tietge
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Villeneuve
mesh_terms: D000818:Animals; D017484:Dermatitis, Phototoxic; D054750:Ecotoxicology; D006801:Humans; D018336:Receptors, Aryl Hydrocarbon / Q000187:drug effects; D011960:Receptors, Estrogen / Q000187:drug effects; D012106:Research; D018570:Risk Assessment; D053608:Stupor / Q000139:chemically induced; D049490:Systems Biology; D014818:Vitellogenesis / Q000187:drug effects
chemical_list: D018336:Receptors, Aryl Hydrocarbon; D011960:Receptors, Estrogen