This project will develop an approach that aids the Department of Defense (DoD) in assessing ecological risks from per- and polyfluoroalkyl substances (PFAS) to threatened and endangered (T&E) species at aqueous film-forming foam (AFFF) impacted sites. Evaluation of exposure pathways for T&E species has been identified as a critical research need for DoD, as the current lack of guidance on how to quantitatively evaluate such risks prevents defensible, risk-based decision making at the hundreds of AFFF-impacted sites currently under assessment. The lack of clear and concrete guidance leaves site management strategies with only excessive and costly remediation options based on unnecessarily conservative assumptions.

This project is separated into two Phases. The objective of Phase 1 was to produce guidance to provide DoD project managers with: 1) a strategic overview of state-of-the-practice for the ecological risk assessment at AFFF sites; and 2) specific guidance on state-of-the-science approaches to quantitatively assess and manage PFAS risks. It was expected that site managers and technical specialists would directly apply the guidance to enable scientifically sound risk-based management to proceed at specific AFFF sites.

To support communication of the white paper guidance, the key technical objectives for Phase 2 will be to:

  1. promote the availability of the guidance via short overview presentations,
  2. develop a hands-on, Microsoft ExcelTM -based PFAS ERA Model Tool that risk assessors can customize and use for evaluating site-specific risks to representative T&E receptors; and,
  3. provide hands-on, in-person training sessions on the guidance and PFAS ERA Model Tool, one of which will be recorded and hosted online for on-demand training purposes via YouTube.



Technical Approach

Current project efforts under Phase 2 are focused on raising awareness and transitioning the guidance to key end-users (site remedial project managers and technical support), as well as the development of customizable tools that will quantitatively model the approaches and information included in the guidance. The former will be accomplished through a series of presentations and webinars that will provide a high-level overview of the technical principles covered in the guidance, while the transition to key end-users will be accomplished through a series of PFAS ERA training workshops targeted towards ecological risk assessors.

The PFAS training workshop series will include a more in-depth overview of the guidance, combined with an interactive demonstration of one of the quantitative modeling tools (i.e., ERA Model Tools) that are being developed to support quantitative application of the guidance. These will include separate aquatic and terrestrial ERA Model Tools, each of which will allow ecological risk assessors to enter site-specific data (e.g., concentrations of PFAS in abiotic and biotic environmental compartments), to evaluate potential risks to ecological receptors using exposure factors for site-relevant wildlife species of interest and available toxicological information for common PFAS. Model outputs will consist of an evaluation of the potential for direct effects to aquatic or terrestrial communities and model-predicted concentrations in food webs and wildlife diet items. Both the aquatic and terrestrial model tools will also feature tables that provide ERA effects characterization (i.e., hazard quotients) and other useful information to facilitate ERA-based decision making at PFAS-impacted sites, with a focus on pragmatic approaches for AFFF-impacted sites that host T&E species.


The primary objectives of the white paper guidance “Guidance for Assessing the Ecological Risks of PFAS to Threatened and Endangered Species at Aqueous Film-Forming Foam Impacted Sites” developed in Phase 1 of the project were twofold. The first was to provide a brief strategic overview of the state-of-the-practice for the ecological risk assessment at DoD AFFF sites, and the second (targeted primarily at ecological risk practitioners) was to identify the key species likely to drive risk-based approaches at AFFF sites and provide a state-of-the-science compendium on key recommended quantitative ecological risk modeling tools and parameters for assessing T&E PFAS risks and formulating risk management approaches. Collectively, the guidance presents recommendations for key approaches and quantitative information for assessing PFAS risks to T&E species and consists principally of the following elements:

  1. identification of key representative wildlife T&E receptor types likely to drive risks at most AFFF sites;
  2. sources and examples of exposure factor information for these species;
  3. PFAS exposure modeling parameters (bioaccumulation, biomagnification, etc.);
  4. a detailed examination of wildlife PFAS No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect Level (LOAEL) Toxicity Reference Values (TRVs) currently available and under development; and
  5. available approaches and quantitative effect benchmark levels in water for evaluating risk to T&E aquatic life such as benthic invertebrates, fish, and amphibians.

As toxicity information for wildlife and aquatic life is limited to only a few PFAS, specific guidance regarding the assessment and uncertainty of other commonly encountered PFAS at AFFF sites, as well as PFAS precursors, was also provided from the perspective of the available technical information and the various evolving DoD branch policies. The guidance concludes with recommendations for site-specific sampling needs for AFFF sites and also general research needs for improving assessment and investigation approaches.


The primary expected benefit of this project is to enable DoD site managers to assess and manage ecological risks to T&E species from PFAS so that site-specific, risk-based management can proceed at the hundreds of AFFF sites currently under or preparing for evaluation. In addition to providing a state-of-the-science review on available technical information and approaches to support DoD-specific goals, the guidance will highlight key research needs that will further improve the assessment and management of PFASs. Additionally, promoting awareness of the guidance and encouraging use of the guidance across a broader range of audiences will help standardize ERA approaches across AFFF-impacted sites by providing a clear framework for making risk-based decisions. (Project Completion - 2021)