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Expanding on Successful Concepts, Models, and Organization
Citation:
Teeguarden, J., C. Tan, S. Edwards, J. Leonard, K. Anderson, R. Corley, M. Kile, S. Massey Simonich, D. Stone, R. Tanguay, K. Waters, S. Harper, AND D. Williams. Expanding on Successful Concepts, Models, and Organization. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 50(17):8921–8922, (2016).
Impact/Purpose:
This short article is a response to comments by Dr. Natalie von Goetz on a pervious published paper. It clarifies the definition of the Aggregate Exposure Pathway, which is an organizational framework developed by researchers at the EPA, Pacific Northwest National Laboratory, and Oregon State University.
Description:
If the goal of the AEP framework was to replace existing exposure models or databases for organizing exposure data with a concept, we would share Dr. von Göetz concerns. Instead, the outcome we promote is broader use of an organizational framework for exposure science. The framework would support improved generation, organization, and interpretation of data as well as modeling and prediction, not replacement of models. The field of toxicology has seen the benefits of wide use of one or more organizational frameworks (e.g., mode and mechanism of action, adverse outcome pathway). These frameworks influence how experiments are designed, data are collected, curated, stored and interpreted and ultimately how data are used in risk assessment. Exposure science is poised to similarly benefit from broader use of a parallel organizational framework, which Dr. von Göetz correctly points out, is currently used in the exposure modeling community. In our view, the concepts used so effectively in the exposure modeling community, expanded upon in the AEP framework, could see wider adoption by the field as a whole. The value of such a framework was recognized by the National Academy of Sciences.1Replacement of models, databases, or any application with the AEP framework was not proposed in our article. The positive role such a framework might have in enabling and advancing “general activities such as data acquisition, organization…,” and exposure modeling was discussed in some detail.Like Dr. von Göetz, we recognized the challenges associated with acceptance of the terminology, definitions, and structure proposed in the paper. To address these challenges, an expert workshop was held in May, 2016 to consider and revise the “basic elements” outlined in the paper. The attendees produced revisions to the terminology (e.g., key events) that align with terminology currently in use in the field. We were also careful in our paper to acknowledge a point raised by Dr. von Göetz that AEP implies aggregation, providing these clarifications: “The simplest form of an AEP represents a single source and a single pathway and may more commonly be referred to as an exposure pathway,”; and “An aggregate exposure pathway may represent multiple sources and transfer through single pathways to the TSE, single sources and transfer through multiple pathways to the TSE, or any combination of these.” This clarification addresses the concern that the AEP term is not accurate or logical, and further expands upon the word “aggregate” in a broader context. Our use of AEP is consistent with the definition for “aggregate exposure”, which refers to the combined exposures to a single chemical across multiple routes and pathways.2 The AEP framework embraces existing methods for collection, prediction, organization, and interpretation human and ecological exposure data cited by Dr. von Göetz. We remain hopeful that the outcome is wider use across the exposure science community, further development of the kind of infrastructure and models Dr. von Göetz discusses, and ultimately, continual improvements in the collection, organization, and application of exposure information, rather than a step backward. DISCLAIMER: The U.S. Environmental Protection Agency has provided administrative review and has approved for publication. The views expressed in this paper are those of the authors and do not necessarily reflect the views of the U.S. Environmental Protection Agency.
