Formatted Title
Risk Assessment of PFAS Chemicals and Implications for Risk Management
Background/Objectives
Knowledge regarding the toxicity and regulatory landscape surrounding per- and polyfluoroalkyl substances (PFAS) is evolving rapidly, with significant implications for the screening and risk characterization of contaminated sites. As a result, the evaluation of human health risks associated with potential exposure to PFAS is challenging because the selection of chemicals of potential concern (COPCs) and risk characterization results can vary based on the regulatory framework. A Superfund site that required a human health risk assessment (HHRA) of PFAS chemicals detected in groundwater highlighted these complexities. This risk assessment challenge was further explored through the context of other state programs.
Approach/Activities
We completed an HHRA for a Superfund site, evaluating the potential risks associated with PFAS chemicals detected in groundwater beneath a residential community. COPC selection was based on the lower of the state groundwater quality standards and the U.S. Environmental Protection Agency (EPA) regional screening levels. Several PFAS were selected as COPCs based on state standards. When characterizing the risk associated with exposure to PFAS chemicals in groundwater, however, the toxicity hierarchy required by EPA to be used in Superfund HHRAs resulted in toxicity criteria different than the basis of the state standards. This example highlighted the current complicated regulatory setting encountered when evaluating PFAS chemicals in HHRAs and how it can affect risk characterization. To explore the impact of varying state PFAS standards on risk characterization, we also demonstrated how groundwater standards and toxicity criteria in other states can alter the risk characterization results using the same set of concentration data.
Results/Lessons Learned
The results of our analysis showed that risk conclusions can vary from no further action to additional evaluation and/or mitigation needed to address risk results that exceed human health benchmarks. Our analysis demonstrates the challenges faced by risk assessors and stakeholders due to the rapidly evolving PFAS regulatory setting and how a thorough evaluation of the uncertainties associated with this shifting landscape is key to informing risk management decisions. This is especially important for stakeholders that may have sites in multiple states and, despite similar levels of contamination, may have very different risk characterization results and risk management decisions from state to state.