EPA's IRIS 1,4-dioxane external peer review in 2012 suggested reviewing the histopathology slides from the NCI 1978 dioxane cancer bioassay in mice to ascertain whether non cancer pathology was evident, since, if evident, this would support the evaluation of a regenerative hyperplasia MOA by EPA staff. TERA scientists worked with Dr. Gene McConnell and staff of the NTP to reevaluate these mouse liver slides, and the results were sent to EPA staff in 2013 and published as Dourson et al., 2014. In brief, the reread of the slides showed extensive non cancer pathology, thus supporting the regenerative hyperplasia MOA. However, this evaluation also led to the desire to evaluate the mouse liver slides from a series of Japanese studies on 1,4-dioxane. In the summer of 2014, five US states and TERA scientists requested these full studies from our Japanese colleagues. These studies were received in the fall of 2014, and were then translated and analyzed during the winter of 2015. A report of this translation and a draft analysis was prepared and sent around to requesting states in July of 2015. As described in a second publication by Dourson et al. 2017, the additional information and translations are also supportive of a regenerative hyperplasia MOA.
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Beyond Science and Decisions: From Problem Formulation to Dose-Response Assessment Workshop XIII
Since 2010, the Alliance for Risk Assessment (ARA) has sponsored a workshop series titled Beyond Science & Decisions: From Problem Formulation to Comprehensive Risk Assessment. Building on the ideas of the National Academy of Sciences' (NAS) Science & Decisions: Advancing Risk Assessment (2009), twelve previous workshops brought together over 60 organizations seeking to advance the NAS recommendations.
Over 50 presented case studies have thus far contributed to an expanding compendium of practical, problem-driven approaches for “fit for purpose” risk assessments. As a resource for regulators and scientists, the compendium details key considerations for applying relevant dose-response or exposure assessment methods, whether novel or evolving, and links these methods to specific problems faced by risk assessors and risk managers in a variety of organizations (e.g., local, regional and federal governments, academia, private sector).
Featured Project: The Conundrum of the PFOA Human Half-life
A coalition of interested parties is being formed to explore and possibly resolve the conundrum in human 1/2 life for perfluorooctanote (PFOA), which is reflected in differences in safe doses world-wide of 750-fold (Mikkonen et al., 2020). A recent paper has been submitted that addresses this conundrum in part (Dourson and Gadagbui, 2021). This collaboration started in April of 2021 with nominations to an advisory committee* who will then lead the coalition through a series of virtual and possibly face-to-face meetings, with conclusions expected later this year. Toxicology Excellence for Risk Assessment (www.tera.org) has been designated as the nonprofit organization to support this coalition by the ARA Steering Committee. Because TERA is a 501c3 nonprofit organization, all donations to this effort are tax deductible.