Ecological Risk Assessment (ERA) models that are based on laboratory-derived toxicity reference values (TRVs) often indicate risks to small mammal populations, even at sites with concentrations of per- and polyfluoroalkyl substances (PFAS) that are consistent with background. The objective of this project is to evaluate whether adverse ecological effects occur in wild, small mammals at environmental concentrations that are considered protective. Field work will be performed where PFAS concentrations in soil are high relative to ecological screening levels and thus where adverse effects to small terrestrial mammals are predicted. Data generated will provide a critical evaluation of ecological risk modeling approaches used in site-specific PFAS ERAs.

The technology being evaluated in this project is the suitability of PFAS terrestrial food web modeling. Food web models are routinely used in Tier 1 and Tier 2 ERAs; however, PFAS-specific model assumptions and parameters have only been recently developed. Key uncertainties regarding the accuracy of PFAS food web models have been hypothesized, and testing and validation of PFAS food web modeling would be useful. 

The approach used to evaluate PFAS terrestrial food web modeling in this project will involve conducting field surveys to evaluate the ecological health of wild populations, which are occasionally conducted in the latter stages of the Tier 2 ERAs. Field surveys will be used to assess the health of a small mammal population at PFAS-impacted sites where site-specific doses predicted with food web models exceed TRVs currently used in PFAS investigations. Comparing the field-observed, population-level health to the modelled risk estimates will allow for a critical evaluation of the accuracy of the approaches that are typically used in site-specific PFAS ERAs. This work will also demonstrate to end users how to best apply PFAS food web modeling.

Evaluating dietary TRVs will provide a basis for refining ecological risk modeling for terrestrial receptors exposed to PFAS. Via a critical evaluation of existing approaches, the demonstration can identify refinements needed for TRVs and ERA approaches to more accurately estimate ecological risk. This validation effort will facilitate the use of modeling, which could lower costs associated with remedial actions. The successful execution of this effort will yield data essential for the development of advanced technologies aimed at enhancing ongoing remediation efforts at PFAS-impacted sites, thereby providing crucial safeguards for warfighters and installation communities. (Anticipated Project Completion - 2029)