This project will address an improved understanding of the ecological toxicity and risk of per- and polyfluoroalkyl substances (PFAS) associated with avian species. PFAS ecological risks to avian species are likely to drive key investigation and remediation decisions at aqueous film-foaming foam (AFFF)-impacted sites. Avian exposures to PFAS in diet items and through incidental soil or sediment ingestion can be evaluated using ecological food web modeling used in traditional ecological risk assessment (ERA). The use of traditional food web exposure modeling allows risk assessors to estimate exposures to avian receptors, especially in the early stages of investigations when data are limited to measurements of PFAS in abiotic samples (e.g., soil, sediment, water). The project team has successfully developed avian PFAS ERA models for SERDP under previous projects (ER18-1614 and ER18-1653). The tools developed under these projects have received positive feedback from regulators and risk assessors. It is believed that a comprehensive validation of the modeling tools, now possible due to the wealth of AFFF site data that has emerged in the past 2-3 years, would further bolster stakeholder confidence in and adoption of the models for application at AFFF sites. This effort supports the objective to validate modeling tools for defining avian exposures to allow comparisons to established avian toxicity reference values (TRV). Evaluating the accuracy of the food web models will enable site managers and technical specialists to conduct ERAs at sites impacted by AFFF with additional confidence, enabling evaluation of the direct risks to aquatic and terrestrial avian species exposed to PFAS in water, sediment, and soil.

This food web model validation process will be accomplished by evaluating accuracy of the models developed previously (ER18-1614 and ER18-1653) by compiling PFAS data from field studies at PFAS-impacted sites, selecting sites with datasets that are appropriate, high quality, and include paired data for PFAS in abiotic media (surface water and sediment at aquatic sites, soil at terrestrial sites) and biotic data for the food web (invertebrates, fish, plants). At these selected sites, the abiotic data (e.g., concentrations in soil, sediment, and/or water) will be used to calculate model-predicted concentrations of PFAS in the food web (i.e., concentrations in plants, invertebrates, fish, etc.). Predicted concentrations of PFAS in biota will be compared to the available site-specific measurements measured concentrations of PFAS in biota to provide a quantitative assessment of model accuracy. Model performance will be determined by the factor difference between modeled predictions compare to measured concentrations.

The primary expected benefit of this project is to provide risk assessment experts with additional confidence in the existing SERDP-supported ERA PFAS models through validation and demonstration of the food web models. This encourages more widespread use of the models by site managers, technical specialists, and regulatory stakeholders to better understand risk to avian wildlife at AFFF sites. Overall, increased use of the modeling will help improve or avoid resource-intensive investigations of PFAS in site biota, and excessive and costly remediation options based on unnecessarily conservative assumptions of PFAS risks at AFFF sites. The expected data produced in this project will be validated food web models for PFAS, which incorporate exposure point concentrations in soil, sediment and water, and uptake factors or regressions for predicting exposure concentrations in wildlife that can be compared to available avian TRVs to determine potential risk. These models will be directly applicable for site-specific ecological risk assessments for avian species at AFFF sites.