The impact of precursors on aquatic exposure assessment for PFAS: Insights from bioaccumulation modeling

Abstract

Risk assessment for per-and polyfluoroalkyl substances (PFAS) is complicated by the fact that PFAS include several thousand compounds. While new analytical methods have increased the number that can be identified in environmental samples, a significant fraction of them remain uncharacterized. Perfluorooctane sulfonate (PFOS) is the PFAS compound of primary interest when evaluating risks to humans and wildlife due to consumption of aquatic organisms. The exposure assessment for PFOS is complicated by the presence of PFOS precursors and their transformation, which can occur both in the environment and within organisms. Thus, the PFOS to which wildlife or people are exposed may consist of PFOS that was discharged directly into the environment and/or other PFOS precursors that were transformed into PFOS. This means that exposure assessment and the development of remedial strategies may depend on the relative concentrations and properties not only of PFOS, but also of other PFAS that are transformed into PFOS. A bioaccumulation model was developed to explore these issues.The model embeds toxicokinetic and bioenergetic components within a larger food web calculation that accounts for uptake from both food and water, as well as predator/prey interactions. Multiple chemicals are modeled, including parent/daughter reactions. A series of illustrative simulations explores how chemical properties can influence exposure assessment and remedial decision-making.

Strategic resources for assessing PFAS ecological risks at AFFF sites

“…For example, Tornabene et al (2021) has focused on evaluating the toxicity of PFOS and PFOA on nine lesser studied amphibians. Similarly, efforts are underway to understand the relative importance of PFAS not currently quantified using standard methods by using bioaccumulation modeling to consider the impact of PFAS precursors (Glaser et al, 2021). As these data gaps are addressed and more lessons learned are gleaned from site‐specific ERAs at PFAS sites, it is envisioned that additional documents and resources will follow those highlighted in this review.…”

Field-Based Distribution and Bioaccumulation Factors for Cyclic and Aliphatic Per- and Polyfluoroalkyl Substances (PFASs) in an Urban Sedentary Waterbird Population

“…In contrast, urban environments can be more concentrated with PFASs, so the relationship between environmental contamination and body burden can be more accurately measured. The addition of advanced models of bioaccumulation that incorporate degradation of precursors, , coupled with using residential species with limited ranges in urban environments (with greater levels of PFAS contamination) provides a more robust evaluation of the transport and bioaccumulation pathways of PFASs.…”

A worldwide evaluation of trophic magnification of per‐ and polyfluoroalkyl substances in aquatic ecosystems

“…Although TOP assay, total fluorine (TF), and extractable organic fluorine (EOF) do not substitute for TMF measurements of the individual PFAS, those additional approaches can give a broad perspective of the unknown PFAS concentrations in the food web and provide complementary information for biomagnification studies. To date, using a TOP assay has revealed significant precursor concentrations in a wide variety of environmental samples (Glaser et al, 2021; Göckener et al, 2021; Ruyle et al, 2021), where TF and EOF can provide information on the quantity of precursor PFAS present in biota and their environments (Loi et al, 2011; Spaan et al, 2020). New analytical techniques can improve TMF investigations because they can reduce the LOD and increase the number of analyzed compounds.…”