PFAS have unique physicochemical properties. Some PFAS are highly stable and unreactive, while retaining the ability to repel both water and oil and reduce surface tension lower than many other surfactants. The stability of many PFAS is attributed to their chemical structure, particularly the carbon-fluorine bond.
PFAS, including prefluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), are undergoing regulatory scrutiny. Scientists are studying the data regarding these chemicals in an attempt to make assessments for health advisories, use and disposal practices, and remediation decisions. Legal and regulatory attention is anticipated to continue in the near and long term.
Gradient has extensive experience in evaluating the potential for PFAS accumulation in humans and ecosystems, source identification, fate and transport in the environment, potential toxicity and risk assessment, and remedial decision-making. Gradient also has a thorough understanding of the historical state of knowledge of PFAS, including exposure and toxicity, fate and transport, analytical chemistry, and ecological effects.
Publications:
Clyde, P; Zic, K; Rice, J. 2023. “Domestic Wastewater as a Nonpoint Source of PFAS Contamination in the US.” Presented at SETAC North America 44th Annual Meeting, Louisville, KY.
Tuit, C; Calder, B; Ritter, E. 2023. “The Challenges of Finding and Mitigating PFAS in Supply Chain.” Presented at the 2023 Society for Chemical Hazard Communication Annual Meeting, Arlington, VA.
Yeh, A; Kerper, L; Prueitt, P; Beck, B. 2023. “Considerations in Evaluating Dermal Absorption of Per-and Polyfluoroalkyl Substances (PFAS).” Presented at the 2023 Annual Meeting of the Society of Toxicology, Nashville, TN.
Campbell, J; Clewell, H; Cox, T; Dourson, M; Ethridge, S; Forsberg, N; Gadagbui, B; Hamade, A; Naidu, R; Pechacek, N; Peixe, TS; Prueitt, R; Rachamalla, M; Rhomberg, L; Smith, J; Verma, N. 2022. “The conundrum of the PFOA human half-life: An international collaboration.” Regul. Toxicol. Pharmacol. 132:105185. doi: 10.1016/j.yrtph.2022.105185.
Boomhower, SR; Kerper, LE; Chien, J; Beck, BD. 2020. “A Comparison of PFAS Serum Concentrations in the General Population to Points of Departure Used in Regulatory Guidance.” Presented at the 2020 Annual Society of Toxicology (SOT) Meeting, virtual.
Pizzurro, DM; Seeley, M; Kerper, LE; Beck, BD. 2019. “Interspecies differences in perfluoroalkyl substances (PFAS) toxicokinetics and application to health-based criteria.” Regul. Toxicol. Pharmacol.
Lemay, JC; Slagowski, NL; Kerper, LE; Sharma, M. 2019. “Occurrence, Distribution, and Bioaccumulation of Per- and Polyfluoroalkyl Substances (PFAS) in Minnesotan Freshwater Environments.” Presented at Battelle’s 10th International Conference on Remediation and Management of Contaminated Sediments, New Orleans, LA.
In the News:
EPA Proposes Extension TSCA PFAS Reporting Deadlines – September 6, 2024
California Department of Toxic Substances Control Releases Draft 2024-2026 Safer Consumer Products Work Plan – June 11, 2024
Project Examples:
Comments on Proposed PFAS Standards in Groundwater. Gradient provided written and oral testimony on behalf of a client to a state pollution control board regarding proposed amendments to groundwater quality standards by the state’s environmental protection agency for six different PFAS. We commented on the agency’s methodology for selecting toxicity values for each of the six PFAS.
PFAS Fate and Transport Assessment at a Municipal Solid Waste Landfill. To support an administrative hearing regarding a landfill expansion permit, Gradient evaluated potential impacts to groundwater and surface water quality near the landfill. We compared chemical concentrations in landfill leachate, groundwater monitoring wells, and nearby surface water with regulatory benchmarks. We used multiple lines of evidence, including an evaluation of the effectiveness of the landfill liner system and temporal evolution of PFAS concentrations in leachate, to estimate the scale of potential surface water impacts if the landfill was expanded.
PFAS Source Evaluation and Forensics. Gradient conducted site research and evaluated the composition and extent of PFAS present at multiple locations throughout the US. Our evaluation included a review of PFAS source characteristics, and fate and transport of PFAS from industrial facilities, landfills, and fire training areas to soil, groundwater, surface water, and sediment. Gradient also evaluated PFAS synthesis process chemistry, compounds associated with specific processes (e.g., ECF and telomerization), and changes in chemical characteristics due to environmental mechanisms to forensically draw conclusions regarding the sources of PFAS being observed in environmental samples.
PFAS State of Knowledge. Gradient researched the scientific state of knowledge and history of PFAS analytical chemistry method development for environmental and biological matrices, ecotoxicity, and bioaccumulation. We developed historical timelines and documented the growth in the scientific knowledge on the basis of a review of the scientific literature, public disclosures, and technical reports. These reviews were critical in understanding data quality standards relevant for different analytical methods, matrices, and time periods, as well as the scientific evolution of PFAS ecotoxicity and bioaccumulation characterization.
Testing and Validating PFAS Product Contents. Gradient provided technical support for PFAS product and testing, risk assessment, and regulatory compliance for multiple products. We developed sampling and analysis plans, selected testing laboratories, validated analytical results, and interpreted these results.
Assessment of Human Health Risks from Alleged PFAS in Oil and Gas Operations. Gradient evaluated allegations of PFAS use in hydraulic fracturing of unconventional natural gas wells and potential health risks. We assessed the evidence behind claims of PFAS presence in these activities, evaluated the potential for releases to occur, and characterized the transport and fate of released materials in the context of existing regulations. We also evaluated the epidemiology and experimental animal data on various health outcomes and assessed the consistency of research findings and their relevance to human health risk assessment.
