Conference Agenda

For ~40 years, a fluorochemical facility in North Carolina discharged perfluoroalkyl ether acids (PFEAs), a poorly understood subgroup of fluorochemicals, to air and water. Those discharges contaminated surface water used for drinking by >280,000 people and >4,000 private wells.

We enrolled people from two impacted communities into the GenX Exposure Study: 344 people served by a municipal water treatment plant (~80 miles downriver) and 153 private well users living within four miles of the facility. We analyzed drinking water and serum for 11 PFEAs using high resolution mass spectrometry. We are evaluating relationships between water and serum PFEA concentrations.

Municipal water historically contained ~130,000 ng/L ∑PFEAs whereas wells had, on average, ~1,100 ng/L ∑PFEAs (n=84 wells). PFMOAA, a three-carbon monoether, was dominant in municipal water (~110,000 ng/L; 85% of ∑PFEAs); PMPA, a four-carbon monoether, was dominant in well water (~430 ng/L average; 40% of ∑PFEAs). Low molecular weight PFEAs frequently detected in water were not detectable in participants’ serum despite documented exposure; other biomonitoring methods will be necessary for exposure characterization. However, Nafion byproduct 2, a seven-carbon diether historically present at ~100 ng/L in municipal water and frequently detected in wells (73% detection, median=14 ng/L, range=non-detect–165 ng/L), was detectable in serum. Nafion byproduct 2 serum levels in municipal water users were higher and less variable (99% detection, median=3.2 ng/mL; coefficient of variation [CV]=0.69) than in well users (56%, median=0.2 ng/mL; CV=2.7), illustrating variable PFEA exposures in the private well community but more uniform exposure in the municipal water community.

Per- and polyfluoroalkyl substances (PFAS) are toxic, persistent, and hardly removed by traditional wastewater treatment approaches. Although industrial emission is a major source of PFAS in raw wastewater, input from households represents an unavoidable “baseline”. PFAS composition and concentration in domestic wastewater, and how they come about are not well understood. In this ongoing study, we are assessing the contribution of households within the sewershed of a wastewater treatment plant (WWTP) to the WWTP’s raw wastewater PFAS loading. The assessment is performed by measuring PFAS in (1) flow-based composite wastewater samples collected from residential sub-sewersheds, and (2) black and grey water generated in households (to identify the major sources of PFAS in residential wastewater). Results obtained so far reveals that total PFAS in domestic wastewater is < 100 ng/L and is dominated by carboxylates (average carboxylates to sulfonates ratio = 3.22). Tap water could account for more than 10% of the PFAS in domestic wastewater. Although there is variation in the daily total PFAS concentration, the composition of PFAS in domestic wastewater is mostly steady. Long-chain carboxylates, perfluorododecanoic acid and perfluorotridecanoic acid, are the main PFAS observed in grey water while short chain carboxylates, perfluorobutanoic acid and perfluoropentanoic acid, are dominant in urine. The outcome of this study will help WWTPs predict their influent baseline PFAS concentration and composition, and guide policy-makers and scientists/engineers on how to address this baseline PFAS at the source.

The North Carolina Department of Environmental Quality’s (NCDEQ) mission is to provide science-based environmental stewardship for the health and property of all North Carolinians. Since 2017, the Department has been dealing with Chemours contamination and the impact on surrounding communities. We have learned from this site that the fate and transport of PFAS is it is rarely a single departmental or media issue. In order to understand what our PFAS universe looks like, we developed a master list of PFAS industries and their associated NAICS and SIC codes by conducting a thorough review of reports, regulatory databases (i.e., EPA), and Federal Registry. This effort generated a working list of 387 industries across 23 different sectors. These industries were crosswalked with existing permits in the Divisions of Air, Water Resources, and Waste Management. This analysis yielded 3,674 unique facilities suspected to be associated with PFAS. When we looked further into these data, we found 130 facilities that held permits in both air, water, and waste divisions. NCDEQ took these 130 facilities and grouped them by industry type and conducted a survey of which industries should be prioritized by getting feedback across the divisions using a top-down and bottom-up approach. The framework that NCDEQ has developed and is currently executing will be able to help other stakeholders apply this same thinking and strengthen the expertise and understanding of PFAS needed to tackle this issue for years to come.

Over 61.1 million m³yr^-1 of leachate is generated in the US, and may contain per- and polyfluoroalkyl substances (PFAS) that pose a risk to human health and the environment. We assessed occurrence of PFAS in landfill leachate and sorption and diffusion of PFAS in flexible membrane liner (FML) and clay liner materials. Four field collected leachates (A-D) were prepared using a previously published micro liquid-liquid extraction method and the total oxidizable precursors assay. Samples were analyzed using targeted analysis and high resolution mass spectrometry with suspect screening. Perfluoroalkyl carboxylates (C4-C10), C4-C8 perfluoroalkyl sulfonates, 6:2 fluorotelomer sulfonate, and 5:3 fluorotelomer carboxylates were present in all leachates, consistent with reports in prior studies. Four perfluoroalkyl ethers were detected in Leachate C that, to our knowledge, have never been previously detected in leachate. Sorption of PFAS to polypropylene (PP) and linear low density polyethylene modified with ethylene vinyl alcohol (LLDPE) up to 1000 ng/L was linear and increased with increasing chain length, and sorption to PP was greater than LLDPE. Sorption to bentonite was low for the majority of PFAS evaluated. Preliminary evaluation of sorption to bentonite modified with Fluorosorb^TM yielded sorption coefficients an order of magnitude or more higher than bentonite. Side-by-side diffusion cells testing diffusion across FMLs and clay liners have been conducted with field-collected leachate. Effective diffusion coefficients (D_eff; m²/s) in bentonite ranged from 3.0 x 10^-12 to 8.9 x 10^-11 and correspond with PFAS molecular weight. Evaluation of diffusion across FMLs and clay modified with Fluorosorb^TM is ongoing

Poly- and perfluoroalkyl substances (PFAS) have been extensively applied for commercial and industrial purposes, which has resulted in their ubiquitous presence in worldwide natural and engineered environments. PFAS have been demonstrated to be persistent and bioaccumulative, and harmful to both humans and ecosystem health. To remove PFAS effectively and efficiently from the environment, a clay-based adsorbent was synthesized via the modification of montmorillonite by a cationic surfactant cetyltrimethyl ammonium chloride (CTAC). Through the co-exposure adsorption tests with organic dyes and PFAS mixtures in aqueous solutions, the optimal ratio of CTAC to cation exchange capacity (CEC) was identified. The optimal modified clay exhibited drastically improved adsorption performance, achieving 100% removal efficiency of the PFAS mixture consisting of nine short- and long-chain PFAAs, GenX, and three precursors at the initial concentrations of parts per billion (ppb) level. Additionally, the modified clay outperformed other commercial adsorbents with respect to adsorption performance. The adsorption kinetic data of all PFAS, which were well described by the pseudo-second order model, suggested an expeditious adsorption process and an adsorption behavior dependent on the initial concentration and carbon chain length. Among the three examined adsorption isotherms, the Sips model combining Langmuir and Freundlich models showed the best fitting correlation, indicating multiple interactions might be involved in the adsorption process. This hypothesis was supported by characterization showing that the modified clay possessed physicochemical properties favorable for electrostatic interactions and hydrophobic interactions. Furthermore, the modified clay was demonstrated to be effective for stabilization of PFAS precursors in sewage sludge.