Characterization of the Bioavailability of Per- and Polyfluoroalkyl Substances in Farmland Soils and the Factors Impacting Their Translocation to Edible Plant Tissues.

In this study, various crops and farmland soils were collected from the Fen-Wei Plain, China, to investigate the bioavailability of perfluoroalkyl substances (PFAS), their accumulation in edible plant tissues, and the factors impacting their accumulation. PFAS were frequently detected in all of the crops, with total concentrations ranging from 0.61 to 35.8 ng/g. The results of sequential extractions with water, basic methanol, and acidic methanol indicate that water extraction enables to characterize the bioavailability of PFAS in soil to edible plant tissues more accurately, especially for the shorter-chain homologues. The bioavailability of PFAS was remarkably enhanced in the rhizosphere (RS) soil, with the strongest effect observed for leafy vegetables. The water-extracted Σ16PFAS in RS soil was strongly correlated with the content of dissolved organic carbon in the soil. Tannins and lignin, identified as the main components of plant root exudates by Fourier transform-ion cyclotron resonance mass spectrometry, were found to enhance the bioavailability of PFAS significantly. Redundancy analysis provided strong evidence that the lipid and protein contents in edible plant tissues play important roles in the accumulation of short- and long-chain PFAS, respectively. Additionally, the high water demand of these tissues during the growth stage greatly facilitated the translocation of PFAS, particularly for the short-chain homologues and perfluorooctanoic acid.

Occurrence of short- and ultra-short chain PFAS in drinking water from Flanders (Belgium) and implications for human exposure.

SHORT: and ultra-short chain perfluoroalkyl substances (S- and US-PFAS) are alternatives for the long-chain PFAS which have been more regulated over time. They are highly mobile in the environment and can easily reach drinking water sources which can become an important human exposure route. Furthermore, there have been growing concerns about the presence of PFAS in Flanders. Because of this, human exposure to S- and US-PFAS through Flemish drinking water was evaluated in this study. For this purpose, the presence of 2 S-PFAS (PFBS and PFBA) and 5 US-PFAS (PFPrS, PFEtS, TFMS, PFPrA and TFA) was investigated in 47 tap water samples, collected from different Flemish provinces, and 16 bottled waters purchased in Flanders. Out of the 7 target PFAS, 4 (PFBA, PFBS, PFPrS and PFEtS) were detected at concentrations above LOQ in tap water. In bottled water, only TFMS was present above its LOQ. PFAS concentrations in all analyzed water samples ranged from <0.7 to 7.3 ng/L for PFBS, <0.03-15.0 ng/L for TFMS and <0.9-12.0 ng/L for PFBA. PFPrS was only detected once above its LOQ, at 0.6 ng/L. No value could be reported for PFPrA due to high procedural blanks resulting in a high LOQ, nor for TFA due to high matrix effect. No significant differences in PFAS concentrations were seen in tap water among different drinking water companies, provinces, nor between the two types of analyzed bottled water (natural mineral water vs spring water). The use of a commercial carbon filter significantly reduced the median concentrations of the studied compounds in tap water. Finally, it was estimated that the presence of S- and US-PFAS in Flemish drinking water does not pose an immediate threat to human health, as concentrations were at least two orders of magnitude below the available guidance values.

An in-depth examination of Per- and Polyfluoroalkyl (PFAS) effects on transporters, with emphasis on the ABC superfamily: A critical review.

Per- and polyfluoroalkyl (PFAS) substances are a type of chemical compound unique for their multiple carbon-fluorine bonds, imbuing them with strength and environmental permanence. While legacy substances have been phased out due to human health risks, short-chain and alternative PFAS remain omnipresent. However, a detailed explanation for the pathways through which PFAS interact on a cellular and molecular level is still largely unknown, and the human health effects remain mechanistically unexplained. Of particular interest when focusing on this topic are the interactions between these exogenous chemicals and plasma and membrane proteins. Such proteins include serum albumin which can transport PFAS throughout the body, solute carrier proteins (SLC) and ATP binding cassette (ABC) transporters which are able to move PFAS into and out of cells, and proteins and nuclear receptors which interact with PFAS intracellularly. ABC transporters as a family have little available human data despite being responsible for the export of endogenous substances and drugs throughout the body. The multifactorial regulation of these crucial transporters is affected directly and indirectly by PFAS. Changes, which can include alterations to membrane transport activity and differences in protein expression, vary greatly depending on the specific PFAS and protein of interest. Together, the myriad of changes caused by understudied PFAS exposure to a class of understudied proteins crucial to cellular function and drug treatments has not been fully explored regarding human health and presents room for further exploration. This critical work aims to provide a novel framework of existing human data on PFAS and ABC transporters, allowing for future advancement and investigation into human transporter activity, mechanisms of regulation, and interactions with emerging contaminants.

Fast analysis of short-chain and ultra-short-chain fluorinated organics in water by on-line extraction coupled to HPLC-HRMS.

A rapid on-line solid-phase extraction liquid chromatography high-resolution mass spectrometry (on-line SPE-LC-HRMS) method was developed to analyze 11 ultra-short and short-chain PFAS in surface water. Analytical optimization involved screening 7 chromatographic columns and 5 on-line SPE columns, as well as evaluating SPE loading conditions, filters, sample acidification, chromatographic mobile phases, and SPE loading mobile phases. The optimized method was then applied to 44 river water samples collected in Eastern Canada, including sites near airports with fire-training areas. Among the 11 targeted PFAS, the most frequently detected were trifluoroacetic acid (TFA, 4.6-220 ng/L), perfluorobutanoic acid (PFBA, 0.85-33 ng/L), perfluoropentanoic acid (PFPeA, 1.2-2100 ng/L), trifluoromethane sulfonic acid (TMS, 0.01-4.3 ng/L), and perfluorobutane sulfonic acid (PFBS, 0.07-450 ng/L). Levels of C3-C5 perfluoroalkyl carboxylic acids (PFCAs), C2-C4 perfluoroalkyl sulfonates (PFSAs) and n:3 polyfluoroalkyl acids (n = 2,3; n:3 acids) were significantly higher in water bodies near fire-training area sites compared with rivers in urban areas. In contrast, TFA, TMS, and 1:3 acid were not significantly elevated, likely reflecting atmospheric deposition or other diffuse sources for these compounds. Nontarget and suspect screening analysis revealed an abundance of other ultra-short and short-chain PFAS in AFFF-impacted water bodies. Perfluoroalkyl sulfonamides (FASA, C2, C3, and C5), perfluoroalkyl sulfonamide propanoic acids (FASA-PrA, C1-C2) and n:3 acids (n = 1, 4, and 5) were detected for the first time in environmental surface waters.

Groundwater solutes influence the adsorption of short-chain perfluoroalkyl acids (PFAA) to colloidal activated carbon and impact performance for in situ groundwater remediation.

Subsurface injection of colloidal activated carbon (CAC) is an in situ remediation strategy for perfluoroalkyl acids (PFAA), but the influence of groundwater solutes on longevity is uncertain, particularly for short-chain PFAA. We quantify the impact of inorganic anions, dissolved organic matter (DOM), and stabilizing polymer on PFAA adsorption to a commercial CAC. Surface characterization supported PFAA chain-length dependent adsorption results and mechanisms are provided. Inorganic anions decreased adsorption for short-chain PFAA (<7 perfluorinated carbons) due to competitive effects, while long-chain PFAA (≥ 7 perfluorinated carbons) were less impacted. DOM decreased adsorption of all PFAA in a chain-length dependent manner. High DOM concentrations (10 mg/L, ∼5 mg OC/L) decreased PFOA adsorption by a factor of 2, PFPeA by one order of magnitude, and completely hindered PFBA adsorption. High MW DOM has less impact on short-chain PFAA than low MW DOM, possibly due to differences in the ability to access CAC micropores. Low DOM concentrations (1 mg/L, ∼0.5 mg OC/L) did not impact adsorption. CMC (90 kDa average MW) had negligible impact on PFAA adsorption likely due to minimal CAC surface coverage. Longevity modeling demonstrated that groundwater solutes limit the capacity for PFAA in a CAC barrier, particularly for short-chain PFAA.

Mixtures of legacy and replacement perfluorosulphonic acids (PFSAs) demonstrate ratio-, concentration- and endpoint-dependent synergistic interactions in vitro.

The extensive use of poly- and per-fluoroalkyl substances (PFASs) has les to their widespread presence in the environment, raising concerns about potential toxicity. While certain PFASs of concern have been phased-out or banned, new PFASs continue to be produced. Two such substances are perfluoroethylcyclohexane sulphonate (PFECHS) and perfluorobutane sulphamide (FBSA), replacements of perfluoroctanesulphonic acid (PFOS) that have recently been detected in multiple environmental media around the globe. Despite PFASs generally occurring in the environment as mixtures, few data are available outlining the effects of PFAS mixtures. Therefore, this research investigated the interaction potential of binary and ternary mixtures of emerging and legacy PFASs. The immortalized rainbow trout gill cell line (RTgill-W1) was chosen as the experimental model to investigate two apical endpoints: cytotoxicity and phospholipidosis. RTgill-W1 cells were exposed for 24 h to each compound to obtain endpoint-specific effect concentrations (LCx; ECx). These values were then applied to formulate mixture predictions following the Loewes Additivity and Steel and Peckham methods. Based on cytotoxicity, relative potencies of individual compounds were: PFOS > PFECHS > FSBA. PFOS and PFECHS had nearly identical effects on phospholipidosis, while FSBA did not have any effects. Most mixtures had a synergistic effect on cytotoxicity, but the effect was both dose- and ratio-dependent. PFOS and PFECHS were additive at lower concentrations (LC10) and synergistic at higher concentrations (LC50; 3:1, 1:1, and 1:3). PFECHS and FSBA mixtures were synergistic at all doses and ratios (3:1, 1:1, 1:3), while FBSA and PFOS were mainly synergistic at higher concentrations and at ratios favouring PFOS (1:1, 1:3). Tertiary combinations were mainly synergistic. For phospholipidosis, mixtures were strictly additive. These results are strongly suggestive of synergism between emerging PFAS replacements and highlight that independent apical mechanisms of different PFASs could combine to induce unexpected toxicity. Considering that emerging replacements are continuing to increase in concentration in the environment, such mixture scenarios are also likely to continue to increase in probability.

Occurrence and toxicity mechanisms of perfluorobutanoic acid (PFBA) and perfluorobutane sulfonic acid (PFBS) in fish.

Perfluorobutanoic acid (PFBA) and perfluorobutane sulfonic acid (PFBS) are short-chain perfluoroalkyl substances (PFAS) ubiquitous in the environment. Here we review data on the presence and toxicity mechanisms of PFBA and PFBS in fish. We aimed to (1) synthesize data on physiological systems perturbed by PFBA or PFBS; (2) determine whether toxicity studies use concentrations reported in aquatic ecosystems and fish tissues; (3) conduct a computational toxicity assessment to elucidate putative mechanisms of PFBA and PFBS-induced toxicity. PFBA and PFBS are reported in the low ng/L in aquatic systems, and both substances are present in tissues of several fish including carp, bass, tilapia, and drum species. Evidence supports toxicity effects on several organ systems, including the cardiac, immune, hepatic, and reproductive system. Multigenerational effects in fish have also been documented for these smaller chain PFAS. To further elucidate mechanisms of reproductive impairment, we conducted in silico molecular docking to evaluate chemical interactions with several fish estrogen receptors, specifically zebrafish, fathead minnow, and Atlantic salmon. PFBS showed higher binding affinity for fish estrogen receptors relative to PFBA. Computational analysis also pointed to effects on lipids "Adipocyte Hypertrophy and Hyperplasia", "Lipogenesis Regulation in Adipocyte", and estrogen-related processes. Based on our review, most data for PFBA and PFBS are gathered for concentrations outside environmental relevance, limiting our understanding of their environment impacts. At the time of this review, there is relatively more toxicity data available for PFBS relative to PFBA in fish. This review synthesizes data on environmental levels and toxicology endpoints for PFBA and PFBS in fish to guide future investigations and endpoint assessments.

Adsorption of per- and polyfluoroalkyl substances (PFAS) from water with porous organic polymers.

Per- and polyfluoroalkyl substances (PFAS) are man-made environmental contaminants causing increasing global concern due to their adverse effect on environmental and human health. Conventional treatment methods are ineffective in removing short-chain PFAS because they are persistent and recalcitrant to treatment. This study evaluated the performance of a structurally-tunable and chemically-stable porous organic polymer (POP) for PFAS removal under realistic environmental conditions. The POP demonstrated an exceptionally high removal efficiency (>95%) within 15 min when the initial PFAS concentration was approximately 400 ng/L. The adsorption of PFAS on the POP was not significantly affected by changes in solution pH within the range of 5-9. The common co-contaminants in water competed with short-chain PFAS for active sites during the adsorption process following the order of natural organic matter (NOM), long-chain PFAS, and Cl-. The Freundlich-type model could predict the multicomponent interactions well with a R2 value above 0.91. The spent POP was effectively regenerated using a mixture of the 10% NaCl and 30% methanol solution and the PFAS removal maintained at 90% through five adsorption and desorption cycles. The characteristics of the designed POP make it a highly promising and stable absorbent. It enables fast and effective removal of short-chain PFAS.

Elevated Levels of Ultrashort- and Short-Chain Perfluoroalkyl Acids in US Homes and People.

Per- and polyfluoroalkyl substances (PFAS) make up a large group of fluorinated organic compounds extensively used in consumer products and industrial applications. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), the two perfluoroalkyl acids (PFAAs) with 8 carbons in their structure, have been phased out on a global scale because of their high environmental persistence and toxicity. As a result, shorter-chain PFAAs with less than 8 carbons in their structure are being used as their replacements and are now widely detected in the environment, raising concerns about their effects on human health. In this study, 47 PFAAs and their precursors were measured in paired samples of dust and drinking water collected from residential homes in Indiana, United States, and in blood and urine samples collected from the residents of these homes. Ultrashort- (with 2 or 3 carbons [C2-C3]) and short-chain (with 4-7 carbons [C4-C7]) PFAAs were the most abundant in all four matrices and constituted on average 69-100% of the total PFAA concentrations. Specifically, trifluoroacetic acid (TFA, C2) and perfluoropropanoic acid (PFPrA, C3) were the predominant PFAAs in most of the samples. Significant positive correlations (n = 81; r = 0.23-0.42; p < 0.05) were found between TFA, perfluorobutanoic acid (PFBA, C4), and perfluoroheptanoic acid (PFHpA, C7) concentrations in dust or water and those in serum, suggesting dust ingestion and/or drinking water consumption as important exposure pathways for these compounds. This study demonstrates that ultrashort- and short-chain PFAAs are now abundant in the indoor environment and in humans and warrants further research on potential adverse health effects of these exposures.

Effects of short-chain per- and polyfluoroalkyl substances (PFAS) on toxicologically relevant gene expression profiles in a liver-on-a-chip model.

Short-chain per- and polyfluoroalkyl substances (PFAS) are highly stable and widely used environmental contaminants that pose potential health risks to humans. Aggregating reliable mechanistic information for safety assessments necessitates physiologically relevant high-throughput screening approaches. Here, we demonstrated the utility of a liver-on-a-chip model to investigate the effects of five short-chain PFAS at low (1 nM) and high (1 µM) concentrations on toxicologically-relevant gene expression profiles using the QuantiGene® Plex Assay. We found that the short-chain PFAS tested in this study modulated the expression of ABCG2, a gene encoding for the breast cancer resistance protein (BCRP), with marked and significant upregulation (up to 4-fold) observed for all but one of the short-chain PFAS tested. PFBS and HFPO-DA repressed SLCO1B3 expression, a gene that encodes for an essential liver-specific organic anion transporter. High concentrations of PFBS, PFHxA, and PFHxS upregulated the expression of genes encCYP1A1,CYP2B6 and CYP2C19 with the same treatments resulting in the repression of the expression of the gene encoding CYP1A2. This dysregulation could have consequences for the clearance of endogenous compounds and xenobiotics. However, we acknowledge that increased expression of genes encoding for transporters and biotransformation enzymes may or may not indicate changes to their protein expression or activity. Overall, our study provides important insights into the effects of short-chain PFAS on liver function and their potential implications for human health. The use of the liver-on-a-chip model in combination with the QuantiGene® Plex Assay may be a valuable tool for future high-throughput screening and gene expression profiling in toxicology studies.

Coexisting ions and long-chain per- and polyfluoroalkyl substances (PFAS) inhibit the adsorption of short-chain PFAS by granular activated carbon.

We assessed the competitive adsorption between long-chain and short-chain PFAS and the impact of coexisting ions to understand the mechanisms leading to the early breakthrough of short-chain PFAS from granular activated carbon (GAC) filters. Three pairs of short-chain and long-chain PFAS representing different functional groups were studied using GAC (Filtrasorb 400) in batch systems. In bisolute systems, the presence of long-chain PFAS decreased the adsorption of short-chain PFAS by 30-50% compared to their single solute adsorption capacity (0.22-0.31 mmol/g). In contrast to the partial decrease observed in bisolute systems, the addition of long-chain PFAS to GAC pre-equilibrated with short-chain PFAS completely desorbed all short-chain PFAS from GAC. This suggested that the outermost adsorption sites on GAC were preferentially occupied by short-chain PFAS in the absence of competition but were prone to displacement by long-chain PFAS. The presence of inorganic/organic ions inhibited the adsorption of short-chain PFAS (up to 60%) but had little to no impact on long-chain PFAS, with the inhibitory trend inversely correlated with Kow values. Study results indicated that the displacement of short-chain PFAS by long-chain PFAS and charge neutralization are important mechanisms contributing to the early breakthrough of short-chain PFAS from GAC systems.

Dataset of surveyed PFAS in water, sediment, and soil of Fountain Creek Watershed, Colorado, USA.

Per- and polyfluoroalkyl substances (PFAS) are widespread and highly persistent organic chemicals with adverse health effects. The US Environmental Protection Agency has issued health advisory limits of 70 ng/L for aqueous concentrations of PFOA + PFOS. In the Colorado Springs, Colorado (USA), metro area, the Widefield Aquifer (groundwater) and Fountain Creek Watershed (surface water) have been contaminated by PFAS from aqueous film-forming foams. Here we present the concentrations of selected linear and branched isomers of legacy PFAS found in surface water (n = 95), soil (n = 83), and sediment (n = 34) samples collected from several creeks of the Fountain Creek Watershed. Collected samples were prepared for high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) analysis via liquid/liquid extraction and/or solid phase extraction (SPE). This dataset includes the geographic locations of sampled creeks, LC/MS/MS instrumental conditions, method verification data including percent recovery to assess method accuracy and background contamination of PFAS in laboratory reagents and supplies, and determined concentrations of PFAS in water, soil, and sediment samples. These locations were surveyed monthly for a full year and provide a rich dataset to assess influence of sampling location, temporal variability in concentration, and overall contaminant persistence.

Enhanced adsorption of short-chain perfluorobutanoic acid by functionalized periodic mesoporous organosilica: Performance and mechanisms.

Removal of short-chain per- and polyfluoroalkyl substances (PFAS) represents a unique challenge in comparison to the long-chain homologs. In this study, a series of functionalized periodic mesoporous organosilica (PMO) materials with tunable molar ratio of fluoroalkyl to amine functional groups were developed and used as platform adsorbents to investigate the adsorption behavior of short-chain PFAS, with a focus on perfluorobutanoic acid (PFBA). Modification with fluoroalkyl group substantially enhanced the adsorption affinity of PFBA with the functionalized PMO materials. Adsorption free energy analysis suggested that although electrostatic interactions were more predominant in PFBA adsorption, modification of PMOs with increased fluoroalkyl group loadings increased the non-electrostatic interactions with PFBA, resulting in more favorable PFBA adsorption. The optimal functionalized PMO showed fast PFBA adsorption kinetics, excellent PFBA removal efficiency in various water chemistry conditions, and can be regenerated and reused for numerous cycles with methanol/water mixture containing 500-mM NH3·H2O as regenerant. Furthermore, the optimal functionalized PMO showed robust performance for the removal of PFAS mixtures under complex natural water matrix. Results of this study suggested the important role of non-electrostatic interactions in enhancing the removal of short-chain PFAS and can provide mechanistic insights into guiding the design of improved adsorbents for PFAS removal.

Comprehensive target analysis and TOP assay of per- and polyfluoroalkyl substances (PFAS) in wild boar livers indicate contamination hot-spots in the environment.

The suitability of wild boar liver as a bioindicator of per- and polyfluoroalkyl substances (PFAS) in the terrestrial environment was investigated. Samples from 50 animals in three different areas associated with (1) contaminated paper sludges distributed on arable land (PS), (2) industrial emissions of PFAS (IE) and (3) background contamination (BC) were analyzed for 66 PFAS, including legacy PFAS, novel substitutes and precursors of perfluoroalkyl acids (PFAAs). Additionally, the Total Oxidizable Precursor (TOP) assay was performed to determine the formation potential of PFAAs from precursors. In total, 31 PFAS were detected with site-specific contamination profiles. PFAS concentrations in livers from area PS and IE (567 and 944 µg kg-1 wet weight, respectively) were multiple times higher than from area BC (120 µg kg-1). The dominating PFAS were the legacy compounds perfluorooctane sulfonic acid (PFOS) in areas PS and BC (426 and 82 µg kg-1, respectively) and perfluorooctanoic acid (PFOA) in area IE (650 µg kg-1). In area IE, the compounds 4,8-dioxa-3H-perfluorononanoic acid (DONA) and hexafluoropropylene oxide dimer acid (HFPO-DA) - which are used as substitutes for PFOA - were determined at 15 and 0.29 µg kg-1, respectively. The formation potential of PFAAs was highest in area PS, but generally lower than the contamination with PFAAs. The pattern of perfluoroalkyl carboxylic acids (PFCAs) in wild boar liver reflects the contamination of the local soil at the two hot-spot areas IE and PS. This first comparison of PFAS contamination between wild boars and soil suggests that wild boar livers are suitable bioindicators for PFAS contamination in the terrestrial environment. Moreover, in terrestrial samples from area IE, legacy PFAS were found to be retained for a longer period as compared to riverine samples (suspended particulate matter and chub filet).

The use of in vitro methods in assessing human health risks associated with short-chain perfluoroalkyl and polyfluoroalkyl substances (PFAS).

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a large class of industrial chemicals with a ubiquitous and persistent presence in the environment. Of the thousands of PFAS used by consumers and industry, very few have been thoroughly characterized for potential adverse effects. This is especially true for the novel short-chain (C < 8) alternatives that replaced legacy PFAS. Perfluoroalkyl and polyfluoroalkyl substances have revealed inconsistencies in the toxicokinetics predicted by animal models and empirical findings in humans. To adequately assess the possible health effects of short-chain PFAS, there is a need for robust aggregated data sets on the mechanistic underpinnings and physiochemical properties of these alternatives. Acquiring relevant data on the health effects of short-chain PFAS can be achieved through high-throughput methods supported by in vitro human cell-based models. This review briefly summarizes some of the toxicity data obtained using human cells in vitro, discusses the advantages and limitations of cell-based models, and provides insights on potential solutions to challenges presented with the use of these methods for use in safety assessments.

Absorption and elimination of per and poly-fluoroalkyl substances substitutes in salmonid species after pre-fertilization exposure.

Due to their relatively large production and few restrictions on uses, novel substitutes for historically used per and poly-fluoroalkyl substances (PFAS) are being used and accumulating in the environment. However, due to a lack of information on their toxicological properties their hazards and risks are hard to estimate. Before fertilization, oocytes of two salmonid species, Arctic Char (Salvelinus alpinus) and Rainbow Trout (Oncorhynchus mykiss), were exposed to three PFAS substances used as substitutes for traditional PFAS, PFBA, PFBS or GenX or two archetypical, historically used, longer-chain PFAS, PFOA and PFOS. Exposed oocytes were subsequently fertilized, incubated and were sampled during several developmental stages, until swim-up. All five PFAS were accumulated into egg yolks with similar absorption rates, and their concentrations in egg yolks were less than respective concentrations in/on egg chorions. Rapid elimination of the five PFAS was observed during the first 3 days after fertilization. Thereafter, amounts of PFOS and PFOA were stable until swim-up, while PFBA, PFBS and GenX were further eliminated during development from one month after the fertilization to swim-up. In these two salmonid species, PFBA, PFBS and GenX were eliminated faster than were PFOS or PFOA.

Effect of granular activated carbon and other porous materials on thermal decomposition of per- and polyfluoroalkyl substances: Mechanisms and implications for water purification.

Thermal treatment is routinely used to reactivate the spent granular activated carbon (GAC) from water purification facilities. It is also an integral part of sewage sludge treatment and municipal solid waste management. This study presents a detailed investigation of the fate of per- and polyfluoroalkyl substances (PFAS) and one PFAS alternative (GenX) in thermal processes, focusing on the effect of GAC. We demonstrate that the thermolysis of perfluoroalkyl carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), and GenX can occur at temperatures of 150‒200 °C. Three temperature zones were discovered for PFOA, including a stable and nonvolatile zone (≤90 °C), a phase-transfer and thermal decomposition zone (90‒400 °C), and a fast decomposition zone (≥400 °C). The thermal decomposition began with the homolysis of a C‒C bond next to the carboxyl group of PFCAs, which formed unstable perfluoroalkyl radicals. Dual decomposition pathways seem to exist. The addition of a highly porous adsorbent, such as GAC or a copolymer resin, compressed the intermediate sublimation zone of PFCAs, changed their thermal decomposition pathways, and increased the decomposition rate constant by up to 150-fold at 250 °C. The results indicate that the observed thermal decomposition acceleration was linked to the adsorption of gas-phase PFCA molecules on GAC. The presence of non-activated charcoals/biochars with a low affinity for PFOA did not accelerate its thermal decomposition, suggesting that the π electron-rich, polyaromatic surface of charcoal/GAC played an insignificant role compared to the adsorbent's porosity. Overall, the results indicate that (1) substantial decomposition of PFCAs and GenX during conventional thermal GAC/sludge/waste treatment is very likely, and (2) the presence or addition of GAC or other highly porous materials can accelerate thermal PFAS decomposition and alter decomposition pathways.

A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants.

Poly- and perfluoroalkyl substances (PFAS) comprise more than 4,000 anthropogenically manufactured compounds with widescale consumer and industrial applications. This critical review compiles the latest information on the worldwide distribution of PFAS and evaluates their fate in wastewater treatment plants (WWTPs). A large proportion (>30%) of monitoring studies in WWTPs were conducted in China, followed by Europe (30%) and North America (16%), whereas information is generally lacking for other parts of the world, including most of the developing countries. Short and long-chain perfluoroalkyl acids (PFAAs) were widely detected in both the influents (up to 1,000 ng/L) and effluents (15 to >1,500 ng/L) of WWTPs. To date, limited data is available regarding levels of PFAS precursors and ultra-short chain PFAS in WWTPs. Most WWTPs exhibited low removal efficiencies for PFAS, and many studies reported an increase in the levels of PFAAs after wastewater treatment. The analysis of the fate of various classes of PFAS at different wastewater treatment stages (aerobic and/aerobic biodegradation, photodegradation, and chemical degradation) revealed biodegradation as the primary mechanism responsible for the transformation of PFAS precursors to PFAAs in WWTPs. Remediation studies at full scale and laboratory scale suggest advanced processes such as adsorption using ion exchange resins, electrochemical degradation, and nanofiltration are more effective in removing PFAS (~95-100%) than conventional processes. However, the applicability of such treatments for real-world WWTPs faces significant challenges due to the scaling-up requirements, mass-transfer limitations, and management of treatment by-products and wastes. Combining more than one technique for effective removal of PFAS, while addressing limitations of the individual treatments, could be beneficial. Considering environmental concentrations of PFAS, cost-effectiveness, and ease of operation, nanofiltration followed by adsorption using wood-derived biochar and/or activated carbons could be a viable option if introduced to conventional treatment systems. However, the large-scale applicability of the same needs to be further verified.

Per- and Polyfluoroalkyl Substances (PFAS) in Breast Milk: Concerning Trends for Current-Use PFAS.

This is the first study in the last 15 years to analyze per- and polyfluoroalkyl substances (PFAS) in breast milk collected from mothers (n = 50) in the United States, and our findings indicate that both legacy and current-use PFAS now contaminate breast milk, exposing nursing infants. Breast milk was analyzed for 39 PFAS, including 9 short-chain and 30 long-chain compounds, and 16 of these PFAS were detected in 4-100% of the samples. The ∑PFAS concentration in breast milk ranged from 52.0 to 1850 pg/mL with a median concentration of 121 pg/mL. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the most abundant PFAS in these samples (medians 30.4 and 13.9 pg/mL, respectively). Two short-chain PFAS, including perfluoro-n-hexanoic acid (PFHxA, C6) and perfluoro-n-heptanoic acid (PFHpA, C7), were detected in most of the samples with median concentrations of 9.69 and 6.10 pg/mL, respectively. Analysis of the available breast milk PFAS data from around the world over the period of 1996-2019 showed that while the levels of the phased-out PFOS and PFOA have been declining with halving times of 8.1 and 17 years, respectively, the detection frequencies of current-use short-chain PFAS have been increasing with a doubling time of 4.1 years.

PFAS removal by ion exchange resins: A review.

Per- and poly-fluoroalkyl substances (PFAS) represent a large family of anthropogenic organic compounds with a wide range of industrial and commercial applications. PFAS have become a global concern due to their toxicity and bio-accumulative properties. PFAS species have been ubiquitously detected in natural waters, wastewaters, sludge, and aquatic and terrestrial species which are anionic, zwitterionic and neutral. The ion exchange (IX) process for PFAS removal is an efficient technology for the remediation of PFAS-laden surface, ground and effluent wastewaters. This approach is more effective towards eliminating emerging short-chain PFAS which are not removed by carbon-based adsorption processes. This article presents a state-of-the-art review of PFAS removal from water via IX process. The evaluation and comparison of various IX resins in terms of kinetics and isotherms is presented. Literature data indicates that IX isotherm uptake capacity for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) can range up to 5 mmol/g on commercially available IX resins such as IRA 958 and IRA 67. The mechanism involved in the PFAS uptake process, such as diffusion, electrostatic interactions and hydrophobic effects are discussed. The effects of the eluent variability on the regeneration efficacy are also highlighted and the effect of single-use vs reuse for newly developed PFAS-specific IX resins are also examined based on the reviewed literature.