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Health and Environmental Effects Research

ORD Framework on Adverse Outcome Pathways To Be Used by OECD To Improve Chemical Safety Assessments

As articulated in the National Academy of Sciences (2007) report, Toxicity Testing in the 21st Century: A Vision and a Strategy, advances in molecular biology (e.g., genomics) offer a path forward for reducing several uncertainties in chemical risk assessment. A major shortcoming of the current testing paradigm supporting regulatory decisionmaking for chemicals is that it relies almost solely on resource-intensive in vivo testing. A direct consequence of this is that relatively little is known concerning the potential toxicology risks of the great majority of chemicals in commerce or in the environment because they never have been tested adequately. To address this deficiency, there has been a movement to make greater use of molecular, biochemical, or histological data generated from in vitro assays (including high-throughput systems) and pathway-specific short-term in vivo tests. A critical challenge to using this type of mechanistic information, however, is to translate it to outcomes relevant to risk assessment and risk management objectives (i.e., protection of individuals or populations).

ORD NHEERL scientists have made key scientific and leadership contributions to the development of a conceptual framework called "Adverse Outcome Pathways" (AOPs) that provides a scientific approach to linking mechanistic information to responses considered relevant to risk assessment and management. First described in a 2010 paper, the concept builds on a long history of using pathway-based approaches in toxicology and is gaining wide recognition in both regulatory and scientific circles. For example, based on recommendations from an EPA Scientific Advisory Panel review this past summer, the Office of Pesticide Programs’ Office of Chemical Safety and Pollution Prevention is beginning to utilize the AOP model to help support pesticide assessments. Subsequently, the AOP framework also played an important role as an organizing principle in the recent Chemical Safety for Sustainability planning process.

It appears now that the Organisation for Economic Co-operation and Development (OECD) intends to use the AOP concept to help frame and address some of the challenges encountered with developing harmonized chemical risk assessments for both ecological and human health effects.

This is an example of the type of scientific leadership that ORD is providing nationally and internationally as it continues to advance and influence evolving approaches in chemical risk assessment for the 21st century. Too, this work supports the ORD Administrator’s Priorities of Assuring the Safety of Chemicals and Protecting America’s Waters.

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