Per- and polyfluoroalkyl ether acids in well water and blood serum from private well users residing by a fluorochemical facility near Fayetteville, North Carolina.

BACKGROUND: A fluorochemical facility near Fayetteville, North Carolina, emitted per- and polyfluoroalkyl ether acids (PFEAs), a subgroup of per- and polyfluoroalkyl substances (PFAS), to air. OBJECTIVE: Analyze PFAS in private wells near the facility and in blood from well users to assess relationships between PFEA levels in water and serum. METHODS: In 2019, we recruited private well users into the GenX Exposure Study and collected well water and blood samples. We targeted 26 PFAS (11 PFEAs) in water and 27 PFAS (9 PFEAs) in serum using liquid chromatography-mass spectrometry. We used regression modeling to explore relationships between water and serum PFAS. For the only PFEA detected frequently in water and serum, Nafion byproduct 2, we used generalized estimating equation (GEE) models to assess well water exposure metrics and then adjusted for covariates that may influence Nafion byproduct 2 serum concentrations. RESULTS: We enrolled 153 participants ages 6 and older (median = 56 years) using 84 private wells. Most wells (74%) had ≥6 detectable PFEAs; median ∑PFEAs was 842 ng/L (interquartile range = 197-1760 ng/L). Low molecular weight PFEAs (PMPA, HFPO-DA [GenX], PEPA, PFO2HxA) were frequently detected in well water, had the highest median concentrations, but were not detectable in serum. Nafion byproduct 2 was detected in 73% of wells (median = 14 ng/L) and 56% of serum samples (median = 0.2 ng/mL). Cumulative dose (well concentration × duration at address) was positively associated with Nafion byproduct 2 serum levels and explained the most variability (10%). In the adjusted model, cumulative dose was associated with higher Nafion byproduct 2 serum levels while time outside the home was associated with lower levels. IMPACT: PFAS are a large class of synthetic, fluorinated chemicals. Fluorochemical facilities are important sources of environmental PFAS contamination globally. The fluorochemical industry is producing derivatives of perfluoroalkyl acids, including per- and polyfluoroalkyl ether acids (PFEAs). PFEAs have been detected in various environmental samples but information on PFEA-exposed populations is limited. While serum biomonitoring is often used for PFAS exposure assessment, serum biomarkers were not good measures of long-term exposure to low molecular weight PFEAs in a private well community. Environmental measurements and other approaches besides serum monitoring will be needed to better characterize PFEA exposure.

Oxidation of Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances by Sulfate and Hydroxyl Radicals: Kinetic Insights from Experiments and Models.

Per- and polyfluoroalkyl substances (PFAS) are widely used anthropogenic chemicals. Because of the strength of the carbon-fluorine bond, PFAS are not destroyed in typical water treatment processes. Sulfate (SO4•-) and hydroxyl (•OH) radicals can oxidize some PFAS, but the behavior of per- and polyfluoroalkyl ether acids (PFEAs) in processes involving SO4•- and •OH is poorly understood. In this study, we determined second-order rate constants (k) describing the oxidation of 18 PFAS, including 15 novel PFEAs, by SO4•- and •OH. Among the studied PFAS, 6:2 fluorotelomer sulfonate reacted most readily with •OH [k•OH = (1.1-1.2) × 107 M-1 s-1], while polyfluoroalkyl ether acids containing an -O-CFH- moiety reacted more slowly [k•OH = (0.5-1.0) × 106 M-1 s-1]. In the presence of SO4•-, polyfluoroalkyl ether acids with an -O-CFH- moiety reacted more rapidly [kSO4•- = (0.89-4.6) × 106 M-1 s-1] than perfluoroalkyl ether carboxylic acids (PFECAs) and a chloro-perfluoro-polyether carboxylic acid (ClPFPECA) [kSO4•- = (0.85-9.5) × 104 M-1 s-1]. For homologous series of perfluoroalkyl carboxylic acids, linear and branched monoether PFECAs, and multiether PFECAs, PFAS chain length had little impact on second-order rate constants. SO4•- reacted with the carboxylic acid headgroup of perfluoroalkyl carboxylic acids and PFECAs. In contrast, for polyfluoroalkyl ether carboxylic and sulfonic acids with an -O-CFH- moiety, the site of SO4•- attack was the -O-CFH- moiety. Perfluoroalkyl ether sulfonic acids were not oxidized by SO4•- and •OH under the conditions evaluated in this study.

Removal and destruction of perfluoroalkyl ether carboxylic acids (PFECAs) in an anion exchange resin and electrochemical oxidation treatment train.

Perfluoroalkyl ether carboxylic acids (PFECAs) are a group of emerging recalcitrant contaminants that are being developed to replace legacy per- and polyfluoroalkyl substances (PFAS) in industrial applications and that are generated as by-products in fluoropolymer manufacturing. Here, we report on the removal and destruction of four structurally different PFECAs using an integrated anion exchange resin (AER) and electrochemical oxidation (ECO) treatment train. Results from this work illustrated that (1) flow-through columns packed with PFAS-selective AERs are highly effective for the removal of PFECAs and (2) PFECA affinity is strongly correlated with their hydrophobic features. Regeneration of the spent resin columns revealed that high percentage (e.g., 80%) of organic cosolvent is necessary for achieving 60-100% PFECA release, and regeneration efficiency was higher for a macroporous resin than a gel-type resin. Treatment of spent regenerants showed (1) >99.99% methanol removal was achieved by distillation, (2) >99.999% conversion of the four studied PFECAs was achieved during the ECO treatment of the still bottoms after 24 hours with an energy per order of magnitude of PFECA removal (EE/O) <1.03 kWh/m3 of total groundwater treated, and (3) >85% of the organic fluorine was recovered as inorganic fluoride. Trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), and perfluoro-2-methoxyacetic acid (PFMOAA) were confirmed via high-resolution mass spectrometry as transformation products (TPs) in the treated still bottoms, and two distinctive degradation schemes and four reaction pathways are proposed for the four PFECAs. Lastly, dissolved organic matter (DOM) inhibited uptake, regeneration, and oxidation of PFECAs throughout the treatment train, suggesting pretreatment steps targeting DOM removal can enhance the system's treatment efficiency. Results from this work provide guidelines for developing effective separation-concentration-destruction treatment trains and meaningful insights for achieving PFECA destruction in impacted aquatic systems.

Extraction and Matrix Cleanup Method for Analyzing Novel Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances in Fruits and Vegetables.

Per- and polyfluoroalkyl ether acids (PFEAs) are a subclass of per- and polyfluoroalkyl substances (PFAS) that are detected with increasing frequency in environmental matrices. Diet can be an important route of PFEA exposure, but the presence of PFEAs in food is poorly understood. Extraction methods for food samples exist for traditionally studied PFAS, but their suitability for PFEAs and other novel PFAS remains unknown. In this study, an extraction and matrix cleanup method was developed to quantify 45 PFAS, including 13 PFEAs, 3 perfluoroalkane sulfonamides, and 6 fluorotelomer carboxylic acids in 10 types of fruits and vegetables. Homogenized samples were extracted with basic methanol, and resulting extracts were diluted with water and cleaned up using solid-phase extraction with weak anion-exchange cartridges. The method was validated by performing spike-recovery experiments at spike levels of 1 ng/g in all 10 matrices and 0.1 ng/g in 2 matrices. For PFAS without a corresponding isotopically labeled internal standard (IS), adopting an IS with a similar chromatographic retention time generated the most accurate recoveries. Dependent upon the matrix, recoveries of 38-44 PFAS (including 10-13 PFEAs) fell within 50-150% for samples spiked at 1 ng/g. Recoveries of 40 and 38 PFAS in blueberries and corn, respectively, fell within 50-150% for samples spiked at 0.1 ng/g. Method quantification limits (MQLs) of PFAS in pure solvents were determined as the lowest calibration level with an accuracy between 70 and 130%. To compensate for matrix effects, a matrix factor was applied on the basis of the analyte response in different matrices relative to the pure solvent. The MQLs of 45 PFAS (including 13 PFEAs) in 10 matrices ranged from 0.025 to 0.25 ng/g. Overall, this method is capable of sensitively quantifying 45 PFAS in many fruits and vegetables.

Fate of Per- and Polyfluoroalkyl Ether Acids in the Total Oxidizable Precursor Assay and Implications for the Analysis of Impacted Water.

Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. The PFAS class includes almost 5000 registered compounds, but analytical methods are lacking for most PFASs. The total oxidizable precursor (TOP) assay was developed to indirectly quantify unknown PFASs that are precursors to commonly measured perfluoroalkyl acids. To understand the behavior of recently identified per- and polyfluoroalkyl ether acids (PFEAs), including fluorinated replacements and manufacturing byproducts, we determined the fate of 15 PFEAs in the TOP assay. Ten perfluoroalkyl ether acids and a chlorinated polyfluoroalkyl ether acid (F-53B) were stable in the TOP assay and represent terminal products that are likely as persistent as historically used PFASs. Adding perfluoroalkyl ether acids and F-53B to the target analyte list for the TOP assay is recommended to capture a higher percentage of the total PFAS concentration in environmental samples. In contrast, polyfluoroalkyl ether acids with a -O-CFH- moiety were oxidized, typically to products that could not be identified by liquid chromatography and high-resolution mass spectrometry. Application of the TOP assay in its proposed enhanced form revealed high levels of PFEAs, the presence of precursors that form perfluoroalkyl carboxylic acids, and the absence of precursors that form PFEAs in surface water impacted by PFAS-containing wastewater discharges.

Environmental Comparison of Biochar and Activated Carbon for Tertiary Wastewater Treatment.

Micropollutants in wastewater present environmental and human health challenges. Powdered activated carbon (PAC) can effectively remove organic micropollutants, but PAC production is energy intensive and expensive. Biochar adsorbents can cost less and sequester carbon; however, net benefits depend on biochar production conditions and treatment capabilities. Here, life cycle assessment was used to compare 10 environmental impacts from the production and use of wood biochar, biosolids biochar, and coal-derived PAC to remove sulfamethoxazole from wastewater. Moderate capacity wood biochar had environmental benefits in four categories (smog, global warming, respiratory effects, noncarcinogenics) linked to energy recovery and carbon sequestration, and environmental impacts worse than PAC in two categories (eutrophication, carcinogenics). Low capacity wood biochar had even larger benefits for global warming, respiratory effects, and noncarcinogenics, but exhibited worse impacts than PAC in five categories due to larger biochar dose requirements to reach the treatment objective. Biosolids biochar had the worst relative environmental performance due to energy use for biosolids drying and the need for supplemental adsorbent. Overall, moderate capacity wood biochar is an environmentally superior alternative to coal-based PAC for micropollutant removal from wastewater, and its use can offset a wastewater facility's carbon footprint.

Determination of 1,4-Dioxane in the Cape Fear River Watershed by Heated Purge-and-Trap Preconcentration and Gas Chromatography-Mass Spectrometry.

Recent U.S. Environmental Protection Agency data show that 1,4-dioxane is frequently detected in U.S. drinking water derived from both groundwater and surface water. 1,4-Dioxane is a likely human carcinogen, and an excess 10(-6) cancer risk is associated with a drinking water concentration of 0.35 µg/L. To support 1,4-dioxane occurrence investigations, source identification and exposure assessment, a rapid and sensitive analytical method capable of quantifying 1,4-dioxane over a wide concentration range in a broad spectrum of aqueous matrices was developed. The fully automated method is based on heated purge-and-trap preconcentration and gas chromatography/mass spectrometry with selected-ion storage and has a reporting limit of 0.15 µg/L. Quantification of 1,4-dioxane was accomplished by isotope dilution using mass-labeled 1,4-dioxane-d8 as internal standard. Matrix spikes yielded recoveries of 86-115% in drinking water, groundwater, surface water, and wastewater treatment plant (WWTP) effluent. Also, 1,3-dioxane can be distinguished from 1,4-dioxane. The method was applied to investigate 1,4-dioxane occurrence and sources in the Cape Fear River watershed of North Carolina. 1,4-Dioxane concentrations ranged from <0.15 µg/L in nonimpacted surface water to 436 µg/L downstream of a WWTP discharge. In WWTP effluent, 1,4-dioxane concentrations varied widely, with a range of 1.3-2.7 µg/L in one community and 105-1,405 µg/L in another. Discharges from three municipal WWTPs were primarily responsible for elevated 1,4-dioxane concentrations in the Cape Fear River watershed.

Transport and release of chemicals from plastics to the environment and to wildlife.

Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2'-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g(-1) to microg g(-1). Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub microg l(-1) to mg l(-1) and were correlated with the level of economic development.

Predicting adsorption isotherms for aqueous organic micropollutants from activated carbon and pollutant properties.

A method based on the Polanyi-Dubinin-Manes (PDM) model is presented to predict adsorption isotherms of aqueous organic contaminants on activated carbons. It was assumed that trace organic compound adsorption from aqueous solution is primarily controlled by nonspecific dispersive interactions while water adsorption is controlled by specific interactions with oxygen-containing functional groups on the activated carbon surface. Coefficients describing the affinity of water for the activated carbon surface were derived from aqueous-phase methyl tertiary-butyl ether (MTBE) and trichloroethene (TCE) adsorption isotherm data that were collected with 12 well-characterized activated carbons. Over the range of oxygen contents covered by the adsorbents (approximately 0.8-10 mmol O/g dry, ash-free activated carbon), a linear relationship between water affinity coefficients and adsorbent oxygen content was obtained. Incorporating water affinity coefficients calculated from the developed relationship into the PDM model, isotherm predictions resulted that agreed well with experimental data for three adsorbents and two adsorbates [tetrachloroethene (PCE), cis-1,2-dichloroethene (DCE)] that were not used to calibrate the model.

Effects of activated carbon characteristics on the simultaneous adsorption of aqueous organic micropollutants and natural organic matter.

The overall objective of this research was to determine the effects of physical and chemical activated carbon characteristics on the simultaneous adsorption of trace organic contaminants and natural organic matter (NOM). A matrix of 12 activated carbon fibers (ACFs) with three activation levels and four surface chemistry levels (acid-washed, oxidized, hydrogen-treated, and ammonia-treated) was studied to systematically evaluate pore structure and surface chemistry phenomena. Also, three commercially available granular activated carbons (GACs) were tested. The relatively hydrophilic fuel additive methyl tertiary-butyl ether (MTBE) and the relatively hydrophobic solvent trichloroethene (TCE) served as micropollutant probes. A comparison of adsorption isotherm data collected in the presence and absence of NOM showed that percent reductions of single-solute TCE and MTBE adsorption capacities that resulted from the presence of co-adsorbing NOM were not strongly affected by the chemical characteristics of activated carbons. However, hydrophobic carbons were more effective adsorbents for both TCE and MTBE than hydrophilic carbons because enhanced water adsorption on the latter interfered with the adsorption of micropollutants from solutions containing NOM. With respect to pore structure, activated carbons should exhibit a large volume of micropores with widths that are about 1.5 times the kinetic diameter of the target adsorbate. Furthermore, an effective adsorbent should possess a micropore size distribution that extends to widths that are approximately twice the kinetic diameter of the target adsorbate to prevent pore blockage/constriction as a result of NOM adsorption.