Novel Fluoroalkylated Surfactants in Soils Following Firefighting Foam Deployment During the Lac-Mégantic Railway Accident

A review of the occurrence and microbial transformation of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF)-impacted environments

Aqueous film-forming foams (AFFFs) have been extensively used for extinguishing hydrocarbon-fuel fires at military sites, airports, and fire-training areas. Despite being a significant source of per- and polyfluoroalkyl substances (PFAS), our understanding of PFAS occurrence in AFFF formulations and AFFF-impacted environments is limited, as is the impact of microbial transformation on the environment fate of AFFF-derived PFAS. This literature review compiles PFAS concentrations in electrochemical fluorination (ECF)- and fluorotelomer (FT)-based AFFFs and provides an overview of PFAS occurrence in AFFF-impacted environments. Our analysis reveals that AFFF use is a predominant point source of PFAS contamination, including primary precursors (polyfluoroalkyl substances as AFFF components), secondary precursors (polyfluoroalkyl transformation products of primary precursors), and perfluoroalkyl acids (PFAAs). Moreover, there are discrepancies between PFAS concentration profiles in AFFFs and those measured in AFFF-impacted media. For example, primary precursors constitute 52.6 % and 99.5 % of PFAS mass in ECF- and FT-based AFFFs, respectively, whereas they represent only 0.7 % total mass in AFFF-impacted groundwater. Conversely, secondary precursors, which constitute <1 % of PFAS in AFFFs, represent 4.0-27.8 % of PFAS in AFFF-impacted environments. The observed differences in PFAS levels between AFFFs and environmental samples are likely due to in-situ biotransformation processes. Biotransformation rates and pathways reported for AFFF-derived primary and secondary precursors varied among different classes of precursors, consistent with the PFAS occurrence in AFFF-impacted environments. For example, readily biodegradable primary precursors, N-dimethyl ammonio propyl perfluoroalkane sulfonamide (AmPr-FASA) and n:2 fluorotelomer thioether amido sulfonate (n:2 FtTAoS), were rarely detected in AFFF-impacted environments. In contrast, key secondary precursors, perfluoroalkane sulfonamides (FASAs) and n:2 fluorotelomer sulfonate (n:2 FTS), were widely detected, which was attributed to their resistance to biotransformation. Key knowledge gaps and future research priorities are presented to better understand the occurrence, fate, and transport of AFFF-derived PFAS in the environment and to design more effective remediation strategies.

Commercial compost amendments inhibit the bioavailability and plant uptake of per- and polyfluoroalkyl substances in soil-porewater-lettuce systems

Compost is widely used in agriculture as fertilizer while providing a practical option for solid municipal waste disposal. However, compost may also contain per- and polyfluoroalkyl substances (PFAS), potentially impacting soils and leading to PFAS entry into food chains and ultimately human exposure risks via dietary intake. This study examined how compost affects the bioavailability and uptake of eight PFAS (two ethers, three fluorotelomer sulfonates, and three perfluorosulfonates) by lettuce (Lactuca sativa) grown in commercial organic compost-amended, PFAS spiked soils. After 50 days of greenhouse experiment, PFAS uptake by lettuce decreased (by up to 90.5 %) with the increasing compost amendment ratios (0-20 %, w/w), consistent with their decreased porewater concentrations (by 30.7-86.3 %) in compost-amended soils. Decreased bioavailability of PFAS was evidenced by the increased in-situ soil-porewater distribution coefficients (Kd) (by factors of 1.5-7.0) with increasing compost additions. Significant negative (or positive) correlations (R2 ≥ 0.55) were observed between plant bioaccumulation (or Kd) and soil organic carbon content, suggesting that compost amendment inhibited plant uptake of PFAS mainly by increasing soil organic carbon and enhancing PFAS sorption. However, short-chain PFAS alternatives (e.g., perfluoro-2-methoxyacetic acid (PFMOAA)) were effectively translocated to shoots with translocation factors > 2.9, increasing their risks of contamination in leafy vegetables. Our findings underscore the necessity for comprehensive risk assessment of compost-borne PFAS when using commercial compost products in agricultural lands.

A novel montmorillonite clay-cetylpyridinium chloride material for reducing PFAS leachability and bioavailability from soils

Soils contaminated by per- and polyfluoroalkyl substances (PFAS) present a significant threat to both ecological and human health. Extensive research efforts are currently underway to develop effective strategies for immobilizing these chemicals in soils. In this study, calcium montmorillonite was modified with cetylpyridinium chloride (CPC-CM) to enhance its electrostatic and hydrophobic interactions with PFAS. CPC-CM exhibited high adsorption for perfluorooctanoate acid (PFOA), perfluorooctane sulfonate (PFOS) and 8:2 fluorotelomer sulfonic acids (8:2 FTSA) across initial concentrations of 50-1000 μg/L, outperforming both the parent CM and L-carnitine modified CM. Soil leaching tests demonstrated the superior immobilization capabilities of the CPC-CM, maintaining an average PFAS leaching rate below 7% after 120-day incubation. In the context of human exposure scenarios, the in vitro bioaccessibility and in vivo bioavailability of PFAS in soils were measured by gastrointestinal extraction and mouse assay. CPC-CM treatment effectively reduced the bioaccessibility (by up to 84%) and bioavailability (by up to 76%) of PFAS in soils. Furthermore, the safety and efficacy of CPC-CM were evaluated using enteric microorganisms of mice. CPC-CM treatment mitigated PFAS-induced changes in the abundance of Bacteroidetes and Firmicutes, thereby reducing PFAS-induced health risks for humans. Overall, CPC-CM synthesized in this study demonstrated superior adsorption performance and application safety, offering a highly promising approach for remediating PFAS-contaminated soil.

Environmental management cycles for chemicals and climate change, EMC4 : A new conceptual framework contextualizing climate and chemical risk assessment and management

The environmental management cycles for chemicals and climate change (EMC4 ) is a suggested conceptual framework for integrating climate change aspects into chemical risk management. The interaction of climate change and chemical risk brings together complex systems that are imperfectly understood by science. Making management decisions in this context is therefore difficult and often exacerbated by a lack of data. The consequences of poor decision-making can be significant for both environmental and human health. This article reflects on the ways in which existing chemicals management systems consider climate change and proposes the EMC4 conceptual framework, which is a tool for decision-makers operating at different spatial scales. Also presented are key questions raised by the tool to help the decision-maker identify chemical risks from climate change, management options, and, importantly, the different types of actors that are instrumental in managing that risk. Case studies showing decision-making at different spatial scales are also presented highlighting the conceptual framework's applicability to multiple scales. The United Nations Environment Programme's development of an intergovernmental Science Policy Panel on Chemicals and Waste has presented an opportunity to promote and generate research highlighting the impacts of chemicals and climate change interlinkages. Integr Environ Assess Manag 2024;20:433-453. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Stability and Biotransformation of 6:2 Fluorotelomer Sulfonic Acid, Sulfonamide Amine Oxide, and Sulfonamide Alkylbetaine in Aerobic Sludge

The 6:2 fluorotelomer sulfonamide (6:2 FTSAm)-based compounds signify a prominent group of per- and polyfluoroalkyl substances (PFAS) widely used in contemporary aqueous film-forming foam (AFFF) formulations. Despite their widespread presence, the biotransformation behavior of these compounds in wastewater treatment plants remains uncertain. This study investigated the biotransformation of 6:2 FTSAm-based amine oxide (6:2 FTNO), alkylbetaine (6:2 FTAB), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA) in aerobic sludge over a 100-day incubation period. The biotransformation of 6:2 fluorotelomer sulfonamide alkylamine (6:2 FTAA), a primary intermediate product of 6:2 FTNO, was indirectly assessed. Their stability was ranked based on the estimated half-lives (t1/2): 6:2 FTAB (no obvious products were detected) ≫ 6:2 FTSA (t1/2 ≈28.8 days) > 6:2 FTAA (t1/2 ≈11.5 days) > 6:2 FTNO (t1/2 ≈1.2 days). Seven transformation products of 6:2 FTSA and 15 products of 6:2 FTNO were identified through nontarget and suspect screening using high-resolution mass spectrometry. The transformation pathways of 6:2 FTNO and 6:2 FTSA in aerobic sludge were proposed. Interestingly, 6:2 FTSAm was hardly hydrolyzed to 6:2 FTSA and further biotransformed to perfluoroalkyl carboxylic acids (PFCAs). Furthermore, the novel pathways for the generation of perfluoroheptanoic acid (PFHpA) from 6:2 FTSA were revealed.

Combustion of high-calorific industrial waste in conventional brick kilns: An emerging source of PFAS emissions to agricultural soils

The brick kilns in the South Asian region are widely documented to partially combust high-calorific waste components of synthetic-industrial origin, which contain hazardous constituents, including per- and polyfluoroalkyl substances (PFAS). Correspondingly, these establishments are necessarily built on agricultural land to easily acquire clay by excavating soil horizons, thus making cultivation soils vulnerable to PFAS contaminations. In this pioneering study, the occurrence, distribution profile, traceability and human health risk exposure to forty-four legacy and novel PFAS homologues, including two ultrashort-chain (C2-C3) PFAS, were investigated in agricultural soils around thirty-two conventional brick kilns across three districts of Pakistan. ⅀44PFAS concentrations ranged from 14.3 to 465 ng/g (median: 28.2 ng/g), which were 2 to 70 folds higher than those in background soils, and slightly higher than those reported in agricultural soils in the global literature. The highest occurrence was observed for PFAS alternatives, i.e., 6:2 fluorotelomer sulfonate (6:2 FTSA) (40 %) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (4.5 %). A significant positive correlation (p < 0.01) was observed among the concentrations of short-chain perfluoroalkyl acids (C4-C7) and novel PFOS substitutes, implying their origin from common sources. Furthermore, ultrashort-chain and short-chain perfluorocarboxylic acids (PFCA) (89 %) and perfluorosulfonic acids (PFSA) (63 %) dominated over long-chain's PFCA (11 %) and PFSA (37 %), respectively. The estimated daily intake to children exposed in surrounding inhabited communities, at 95th percentile concentrations was found to be approaching the European tolerable daily intake limit of 0.63 ng/kg bw/day. Therefore, the brick manufacturing industry is identified as a novel source of PFAS in the adjacent environment and for residents. This suggests the need for further investigations to elucidate the origin of emerging contaminants in the waste streams of the region to safeguard ecological integrity.

Nontarget Identification of Novel Per- and Polyfluoroalkyl Substances (PFAS) in Soils from an Oil Refinery in Southwestern China: A Combined Approach with TOP Assay

Oil refinery activity can be an emission source of perfluoroalkyl and polyfluoroalkyl substances (PFAS) to the environment, while the contamination profiles in soils remain unknown. This study investigated 44 target PFAS in soil samples collected from an oil refinery in Southeastern China, identified novel PFAS, and characterized their behaviors by assessing their changes before and after employing advanced oxidation using a combination of nontarget analysis and a total oxidizable precursor (TOP) assay. Thirty-four target PFAS were detected in soil samples. Trifluoroacetic acid (TFA) and hexafluoropropylene oxide dimer acid (HFPO-DA) were the dominant PFAS. Twenty-three novel PFAS of 14 classes were identified, including 8 precursors, 11 products, and 4 stable PFAS characterized by the TOP assay. Particularly, three per-/polyfluorinated alcohols were identified for the first time, and hexafluoroisopropanol (HFIP) quantified up to 657 ng/g dw is a novel precursor for TFA. Bistriflimide (NTf2) potentially associated with an oil refinery was also reported for the first time in the soil samples. This study highlighted the advantage of embedding the TOP assay in nontarget analysis to reveal not only the presence of unknown PFAS but also their roles in environmental processes. Overall, this approach provides an efficient way to uncover contamination profiles of PFAS especially in source-impacted areas.

Environmental distribution of per- and polyfluoroalkyl substances (PFAS) on Svalbard: Local sources and long-range transport to the Arctic

The environmental distribution of per- and polyfluoroalkyl substances (PFAS) in water, snow, sediment and soil samples taken along the west coast of Spitsbergen in the Svalbard archipelago, Norwegian Arctic, was determined. The contribution of potential local primary sources (wastewater, firefighting training site at Svalbard airport, landfill) to PFAS concentrations and long-range transport (atmosphere, ocean currents) were then compared, based on measured PFAS levels and composition profiles. In remote coastal and inland areas of Spitsbergen, meltwater had the highest mean ΣPFAS concentration (6.5 ± 1.3 ng L-1), followed by surface snow (2.5 ± 1.7 ng L-1), freshwater (2.3 ± 1.1 ng L-1), seawater (1.05 ± 0.64 ng L-1), lake sediments (0.084 ± 0.038 ng g-1 dry weight (dw)) and marine sediments ( Collapse

Key Words

• Arctic
• Firefighting training sites
• Long-range atmospheric transport
• Meltwater
• Per- and polyfluoroalkyl substances (PFAS)
• Point sources

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MESH Headings

• Svalbard
• Water Pollutants, Chemical/analysis
• Environmental Monitoring
• Fluorocarbons/analysis
• Water
• Lakes
• Alkanesulfonates
• Arctic Regions
• Soil

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Affiliation(s)

Lutz Ahrens Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden.
Jelena Rakovic Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden; Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), Box 7014, SE-750 07, Uppsala, Sweden
Siri Ekdahl Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden
Roland Kallenborn Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Christian Magnus Falsens vei 18, 1433 Ås, Norway; University Centre in Svalbard, Box 156, NO-9171, Longyearbyen, Norway

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Application of in-source fragmentation to the identification of perfluoropentanoic acid and perfluorobutanoic acid in environmental matrices and human serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is the most common analytical technique for per- and polyfluoroalkyl substances (PFASs) research and monitoring. The PFAS identification requires a minimum of two multiple reaction monitoring (MRM) transition ions as quantifier transition ion and qualifier transition ion, respectively. The second transition ion abundance for perfluoropentanoic acid (PFPeA) and perfluobutanoic acid (PFBA) is too low for practical use. A method using the in-source fragment ions as the precursor ion for MRM or pseudo-MRM has been developed and evaluated for PFPeA and PFBA identification in various environmental abiotic and biotic samples including water, soil, sediment, WWTP sludge, fruits, vegetables, egg, macrophytes, fish, dolphin liver and human serum. The PFPeA qualifier MRM transition ion (m/z = 219 > 69) has been successfully applied in all the matrices with spike recoveries (90-125%), signal to noise ratios (>10) and transition ions ratio variation (80-120%). The PFBA qualifier pseudo-MRM transition ion (m/z = 169 > 169) works well in all the matrices except dolphin liver sample. The interpretation of pseudo-MRM results should be with cautions due to lower specificity compared to MRM. In addition, this project indicated under typical chromatographic conditions the MRM isobaric interference does happen frequently to PFPeA quantifier transition ion (m/z = 263 > 219) in serum and fish composite samples, and to PFBA quantifier transition ion (m/z = 213 > 169) in macrophytes, fish composite and dolphin liver samples.

Target and nontarget analysis of per- and polyfluoroalkyl substances in surface water, groundwater and sediments of three typical fluorochemical industrial parks in China

The objectives of this study were to identify both legacy and emerging per- and polyfluoroalkyl substances (PFAS) from three typical fluoridated industrial parks (FIPs) in China, and to assess their environmental occurrence and fate. Complementary suspect target and nontarget screening were implemented, and a total of 111 emerging PFAS were identified. Based on the multi-mass scale analysis, 25 emerging PFAS were identified for the first time, including 24 per- and polyfluoroalkyl ether carboxylic acids (PFECAs) and 1 ultra-short chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs, C2), with a maximum percentage of 48.2 % in nontarget PFAS (exclude target PFAS). The composition of PFAS identified in different media was influenced by functional groups, carbon chain length, substituents and ether bond insertion, with poly-hydrogen substituted being preferably in water and a more diverse pattern of PFECAs in sediments. The patterns of PFAS homologs revealed distinct differences among the three typical FIPs in the shift of PFAS production patterns. The C4-PFAS and short-chain carboxylic acids (≤C6) were the main PFAS in the Fuxin and Changshu, respectively. In contrast, perfluorooctanoic acid (PFOA, C8) remained dominant in Zibo, and the highest point concentrations in water and sediment were up to 706 µg/L and 553 µg/g, respectively.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) by weeds: Effect of PFAS physicochemical properties and plant physiological traits

Phytoextraction is a promising technology that uses plants to remediate contaminated soil. However, its feasibility for per- and polyfluoroalkyl substances (PFAS) and the impact of PFAS properties and plant traits on phytoextraction efficacy remains unknown. In this study, we conducted greenhouse experiment and evaluated the potential of weeds for phytoextraction of PFAS from soil and assessed the effects of PFAS properties and plant traits on PFAS uptake via systematic correlation analyses and electron probe microanalyzer with energy dispersive spectroscopy (FE-EPMA-EDS) imaging. The results showed that 1) phytoextraction can remove 0.04%- 41.4%wt of PFAS from soil, with extracted PFAS primarily stored in plant shoots; 2) Weeds preferentially extracted short-chain PFAS over long-chain homologues from soil. 3) PFAS molecular size and hydrophilicity determined plant uptake behavior, while plant morphological traits, particularly root protein and lipid content, influenced PFAS accumulation and translocation. Although plants with thin roots and small leaf areas exhibited greater PFAS uptake and storage ability, the impact of PFAS physicochemical properties was more significant. 4) Finally, short-chain PFAS were transported quickly upwards in the plant, while uptake of long-chain PFOS was restricted.

Practical application guide for the discovery of novel PFAS in environmental samples using high resolution mass spectrometry

BACKGROUND

The intersection of the topics of high-resolution mass spectrometry (HRMS) and per- and polyfluoroalkyl substances (PFAS) bring together two disparate and complex subjects. Recently non-targeted analysis (NTA) for the discovery of novel PFAS in environmental and biological media has been shown to be valuable in multiple applications. Classical targeted analysis for PFAS using LC-MS/MS, though growing in compound coverage, is still unable to inform a holistic understanding of the PFAS burden in most samples. NTA fills at least a portion of this data gap.

OBJECTIVES

Entrance into the study of novel PFAS discovery requires identification techniques such as HRMS (e.g., QTOF and Orbitrap) instrumentation. This requires practical knowledge of best approaches depending on the purpose of the analyses. The utility of HRMS applications for PFAS discovery is unquestioned and will likely play a significant role in many future environmental and human exposure studies.

METHODS/RESULTS

PFAS have some characteristics that make them standout from most other chemicals present in samples. Through a series of tell-tale PFAS characteristics (e.g., characteristic mass defect range, homologous series and characteristic fragmentation patterns), and case studies different approaches and remaining challenges are demonstrated.

IMPACT STATEMENT

The identification of novel PFAS via non-targeted analysis using high resolution mass spectrometry is an important and difficult endeavor. This synopsis document will hopefully make current and future efforts on this topic easier to perform for novice and experienced alike. The typical time devoted to NTA PFAS investigations (weeks to months or more) may benefit from these practical steps employed.

PFAS in fish from AFFF-impacted environments: Analytical method development and field application at a Canadian international civilian airport

Methods targeting anionic per- and polyfluoroalkyl substances (PFAS) in aquatic biota are well established, but commonly overlook many PFAS classes present in aqueous film-forming foams (AFFFs). Here, we developed an analytical method for the expanded analysis of negative and positive ion mode PFAS in fish tissues. Eight variations of extraction solvents and clean-up protocols were first tested to recover 70 AFFF-derived PFAS from the fish matrix. Anionic, zwitterionic, and cationic PFAS displayed the best responses with methanol-based ultrasonication methods. The response of long-chain PFAS was improved for extracts submitted to graphite filtration alone compared with those involving solid-phase extraction. The validation included an assessment of linearity, absolute recovery, matrix effects, accuracy, intraday/interday precision, and trueness. The method was applied to a set of freshwater fish samples collected in 2020 in the immediate vicinity (creek, n = 15) and downstream (river, n = 15) of an active fire-training area at an international civilian airport in Ontario, Canada. While zwitterionic fluorotelomer betaines were major components of the subsurface AFFF source zone, they were rarely detected in fish, suggesting limited bioaccumulation potential. PFOS largely dominated the PFAS profile, with record-high concentrations in brook sticklebacks (Culaea inconstans) from the creek (16000-110,000 ng/g wet weight whole-body). These levels exceeded the Canadian Federal Environmental Quality Guidelines (FEQG) for PFOS pertaining to the Federal Fish Tissue Guideline (FFTG) for fish protection and Federal Wildlife Diet Guidelines (FWiDG) for the protection of mammalian and avian consumers of aquatic biota. Perfluorohexane sulfonamide and 6:2 fluorotelomer sulfonate were among the precursors detected at the highest levels (maximum of ∼340 ng/g and ∼1100 ng/g, respectively), likely reflecting extensive degradation and/or biotransformation of C6 precursors originally present in AFFF formulations.

High Persistence of Novel Polyfluoroalkyl Betaines in Aerobic Soils

Some contemporary aqueous film-forming foams (AFFFs) contain n:3 and n:1:2 fluorotelomer betaines (FTBs), which are often detected at sites impacted by AFFFs. As new chemical replacements, little is known about their environmental fate. For the first time, we investigated the biotransformation potential of 5:3 and 5:1:2 FTBs and a commercial AFFF that mainly contains n:3 and n:1:2 FTBs (n = 5, 7, 9, 11, and 13). Although some polyfluoroalkyl compounds are precursors to perfluoroalkyl acids, 5:3 and 5:1:2 FTBs exhibited high persistence, with no significant changes even after 120 days of incubation. While the degradation of 5:3 FTB into suspected products such as fluorotelomer acids or perfluoroalkyl carboxylic acids (PFCAs) could not be conclusively confirmed, we did identify a potential biotransformation product, 5:3 fluorotelomer methylamine. Similarly, 5:1:2 FTB did not break down or produce short-chain hydrogen-substituted polyfluoroalkyl acids (n:2 H-FTCA), hydrogen-substituted PFCA (2H-PFCA), or any other products. Incubating the AFFF in four soils with differing properties and microbial communities resulted in 0.023-0.25 mol % PFCAs by day 120. Most of the products are believed to be derived from n:2 fluorotelomers, minor components of the AFFF. Therefore, the findings of the study cannot be fully explained by the current understanding of structure-biodegradability relationships.

Practical Semiquantification Strategy for Estimating Suspect Per- and Polyfluoroalkyl Substance (PFAS) Concentrations

Semiquantitation of suspect per- and polyfluoroalkyl substances (PFAS) in complex mixtures is challenging due to the increasing number of suspect PFAS. Traditional 1:1 matching strategies require selecting calibrants (target-surrogate standard pairs) based on head group, fluorinated chain length, and retention time, which is time-consuming and requires expert knowledge. Lack of uniformity in calibrant selection for estimating suspect concentrations among different laboratories makes comparing reported suspect concentrations difficult. In this study, a practical approach whereby the area counts for 50 anionic and 5 zwitterionic/cationic target PFAS were ratioed to the average area of their respective stable-isotope labeled surrogates to create "average PFAS calibration curves" for suspects detected in negative- and positive-ionization mode liquid chromatography quadrupole time-of-flight mass spectrometry. The calibration curves were fitted with log-log and weighted linear regression models. The two models were evaluated for their accuracy and prediction interval in predicting the target PFAS concentrations. The average PFAS calibration curves were then used to estimate the suspect PFAS concentration in a well-characterized aqueous film-forming foam. Weighted linear regression resulted in more target PFAS that fell within 70-130% of their known standard value and narrower prediction intervals than the log-log transformation approach. The summed suspect PFAS concentrations calculated by weighted linear regression and log-log transformation were within 8 and 16% of those estimated by a 1:1 matching strategy. The average PFAS calibration curve can be easily expanded and can be applied to any suspect PFAS even if the confidence in the suspect structure is low or unknown.

Target and nontarget screening of PFAS in drinking water for a large-scale survey of urban and rural communities in Québec, Canada

Limited monitoring data are available regarding the occurrence of emerging per- and polyfluoroalkyl substances (PFAS) in drinking water. Here, we validated an analytical procedure for 42 PFAS with individual detection limits of 0.001-0.082 ng/L. We also evaluated how different sample pH conditions, dechlorinating agents, and storage holding times might affect method performance. PFAS were analyzed in tap water samples collected at a large spatial scale in Quebec, Canada, covering 376 municipalities within 17 administrative regions. Target and nontarget screening revealed the presence of 31 and 23 compounds, respectively, representing 24 homolog classes. Overall, 99.3% of the tap water samples were positive for at least one PFAS, and the ƩPFAS ranged from below detection limits to 108 ng/L (95th percentile: 13 ng/L). On average, ƩPFAS was 12 times higher in tap water produced from surface water than groundwater; however, 6 of the top 10 contaminated locations were groundwater-based. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) had high detection rates (88% and 80%, respectively). PFOS (median: 0.15 ng/L; max: 13 ng/L) and PFOA (median: 0.27 ng/L; max: 8.1 ng/L) remained much lower than current Health Canada guidelines but higher than USEPA's interim updated health advisories. Short-chain (C3-C6) perfluoroalkyl sulfonamides were also recurrent, especially the C4 homolog (FBSA: detection rate of 50%). The 6:2 fluorotelomer sulfonyl propanoamido dimethyl ethyl sulfonate (6:2 FTSO2PrAd-DiMeEtS) was locally detected at ∼15 ng/L and recurred in 8% of our samples. Multiple PFAS that are most likely to originate from aqueous film-forming foams were also reported for the first time in tap water, including X:3 and X:1:2 fluorotelomer betaines, hydroxylated X:2 fluorotelomer sulfonates, N-trimethylammoniopropyl perfluoroalkane sulfonamides (TAmPr-FHxSA and TAmPr-FOSA), and N-sulfopropyl dimethylammoniopropyl perfluoroalkane sulfonamidopropyl sulfonates (N-SPAmP-FPeSAPS and N-SPAmP-FHxSAPS).

Determination of Perfluorooctane Sulfonyl Fluoride and Perfluorohexane Sulfonyl Fluoride in Soil by Chemical Derivatization and Liquid Chromatography-Tandem Mass Spectrometry

Perfluorooctane sulfonyl fluoride (PFOSF) and perfluorohexane sulfonyl fluoride (PFHxSF) were listed as persistent organic pollutants by the Stockholm Convention in 2009 and 2022, respectively. To date, their concentrations in environmental samples have not been reported due to the lack of sensitive methods. Herein, a novel chemical derivatization was developed for quantitative analysis of trace PFOSF and PFHxSF in soil by derivatizing them to the corresponding perfluoroalkane sulfinic acids. The method showed good linearity in the range from 25 to 500 ng L^-1 with correlation coefficients (R²) better than 0.99. The detection limit of PFOSF in soil was 0.066 ng g^-1 with recoveries in the range of 96-111%. Meanwhile, the detection limit of PFHxSF was 0.072 ng g^-1 with recoveries in the range of 72-89%. Simultaneously, perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) were also detected accurately without being affected by the derivative reaction. By applying this method in an abandoned fluorochemical manufacturing facility, PFOSF and PFHxSF were successfully detected at concentrations ranging from 2.7 to 357 ng g^-1 and 0.23 to 26 ng g^-1 dry weight, respectively. It is very interesting that 2 years after factory relocation, there still exists high concentrations of PFOSF and PFHxSF, which is of concern.

PFASs in Soil: How They Threaten Human Health through Multiple Pathways and Whether They Are Receiving Adequate Concern

Per- and polyfluoroalkyl substances (PFASs) have been mass-produced and widely applied in consumer and industrial products, resulting in their widespread presence in the environment. Features such as environmental persistence, bioaccumulation, and high toxicity even at low doses have made PFASs an increasing concern. This brief review focuses on soil PFASs, especially the effect of soil PFASs on other environmental media and their potential threats to human health through daily diet. Specifically, soil PFASs contamination caused by different pathways was first investigated. Soil pollution from application of aqueous film-forming foams (AFFFs) is generally more severe than that from fluorochemical manufacturing plants, followed by biosolid land use, landfill, and irrigation. Factors, such as carbon chain length of PFASs, wastewater treatment technology, geographical conditions, and regional development level, are related to soil PFASs' pollution. Then, the migration, bioaccumulation, and toxicity characteristics of soil PFASs were analyzed. Short-chain PFASs have higher solubility, mobility, and bioavailability, while long-chain PFASs have higher bioaccumulation potential and are more toxic to organisms. Factors such as soil texture, solution chemistry conditions, enzymes, and fertilization conditions also influence the environmental behavior of PFASs. The risk of human exposure to PFASs through agricultural and animal products is difficult to control and varies depending on living region, age, eating habits, lifestyle, ethnicity, etc. Soil PFASs threaten drinking water safety, affect soil function, and enter food webs, threatening human health. Knowledge gaps and perspectives in these research fields are also included in current work to assist future research to effectively investigate and understand the environmental risks of soil PFASs, thereby reducing human exposure.

An Integrated Approach for Determination of Total Per- and Polyfluoroalkyl Substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are difficult to analyze in environmental media due challenges such as extraction recovery and lack of analytical standards. The total oxidizable precursor (TOP) assay and suspect screening analysis coupled with semiquantitative (SQ) concentration estimates are two approaches to assess total PFAS in environmental media, but studies are needed to optimize workstreams for total PFAS analysis. This study applied two soil extraction methods, TOP assay, and SQ analysis to three aqueous film-forming foams (AFFFs) and three AFFF-impacted soils. In soils, the total PFAS estimated with results from an extraction method utilizing sequential acidic and basic solvents led to a 35% increase in precursors during TOP assay relative to results from a basic solvent only extraction in one of three soils tested, but concentrations did not increase significantly in remaining soils. Furthermore, sample-specific dilution schemes were required to overcome matrix effects caused by the acidic extraction step that influenced estimates of total PFAS by SQ analysis. The results highlight that there is not an advantage to routine application of an acid extraction step in PFAS-impacted soils. In three AFFFs, suspect screening of post-TOP samples identified eight classes of PFAS present after oxidation. Concentrations of three classes increased, suggesting they are new TOP end points. Concentrations of the remaining five classes either remained constant after TOP or exhibited slight decreases. As a result, combined TOP and SQ workstreams may yield the most representative assessment of total PFAS composition and concentration. The eight classes of PFAS present after TOP did not degrade in harsh conditions. Some are structurally similar to PFCAs and PFSAs and are known to occur in the environment, suggesting a similar degree of persistence and a need for more routine monitoring.

Targeted and Suspect Screening of Per- and Polyfluoroalkyl Substances in Cosmetics and Personal Care Products

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals reported in cosmetics and personal care products as ingredients, possible impurities in the raw material manufacturing process, or degradation products. The purpose of this study was to further delineate contributions of these varying PFAS sources to these products. Thirty-eight cosmetics and personal care products were selected and analyzed for polyfluoroalkyl phosphates (PAPs), perfluoroalkyl carboxylic acids (PFCAs), fluorotelomer sulfonic acids (FTSAs), and perfluoroalkyl sulfonic acids (PFSAs) using targeted liquid chromatography tandem mass spectrometry (LC-MS/MS). A subset of products was also subjected to suspect screening using LC-high resolution mass spectrometry (HRMS) for >200 compounds. Results of LC-MS/MS and LC-HRMS indicated a predominant and ubiquitous presence of PAPs (detection frequency 99.7%, mean and median ΣPAPs 1 080 000 and 299 ng/g). Total median PFCA and PFSA concentrations were 3 and 38 times lower, respectively. There were significant correlations (Spearman's correlation coefficients = 0.60-0.81, p < 0.05) between 6:2 PAPs and their biotransformation products. Low levels of other PFAS classes were detected, including those previously measured in wastewater and human blood (e.g., hydrido-PFCAs), and five compounds associated with aqueous film-forming foams. Overall, these data highlight that cosmetics and personal care products can contain a breadth of PFAS at extremely high levels, leading to human and environmental exposure.

Suspect screening and nontargeted analysis of per- and polyfluoroalkyl substances in representative fluorocarbon surfactants, aqueous film-forming foams, and impacted water in China

Massive usage of aqueous film-forming foams (AFFF) containing fluorocarbon surfactants (FS) is one of the major sources of per- and polyfluoroalkyl substances (PFAS) contamination, which poses negative environmental and health effects. However, there is a critical knowledge gap regarding PFAS chemical compositions in high consumption FS products which were used in AFFFs on the Chinese market and in water impacted by such products. This study firstly applied a comprehensive suspect screening and nontargeted analysis (NTA) workflow to investigate the main ionic and neutral PFAS in FS products from the largest Chinese vendor and compared with two international brands to unveil the PFAS used in AFFF. Overall, 24 classes of PFAS, including 69 compounds, were tentatively identified in FS products, and high concentrations of neutral PFAS were found in polymer-based products, indicating potential environmental risk. In addition, we applied a simplified data mining process to capture 36 PFAS from the impacted water, and the relationship among FS, AFFF concentrates and impacted water was explored. This study parsed the PFAS characteristics in AFFF-related industrial products and impacted water in China, which is instrumental for managing and controlling prioritized PFAS in this field.

Aerobic biotransformation of 6:2 fluorotelomer sulfonate by Dietzia aurantiaca J3 under sulfur-limiting conditions

The polyfluorinated alkyl substance 6:2 fluorotelomer sulfonate (6:2 FTS) has been detected in diverse environments impacted by aqueous film-forming foams used for firefighting. In this study, a bacterial strain (J3) using 6:2 FTS as a sulfur source was isolated from landfill leachate previously exposed to polyfluoroalkyl substances in New South Wales, Australia. Strain J3 shares 99.9% similarity with the 16S rRNA gene of Dietzia aurantiaca CCUG 35676^T. Genome sequencing yielded a draft genome sequence of 37 contigs with a G + C content of 69.7%. A gene cluster related to organic sulfur utilisation and assimilation was identified, that included an alkanesulfonate monooxygenase component B (ssuD), an alkanesulfonate permease protein (ssuC), an ABC transporter (ssuB), and an alkanesulfonate-binding protein (ssuA). Proteomic analyses comparing strain J3 cultures using sulfate and 6:2 FTS as sulfur source indicated that the ssu gene cluster was involved in 6:2 FTS biodegradation. Upregulated proteins included the SsuD monooxygenase, the SsuB transporter, the ABC transporter permease (SsuC), an alkanesulfonate-binding protein (SsuA), and a nitrilotriacetate monooxygenase component B. 6:2 Fluorotelomer carboxylic acid (6:2 FTCA) and 6:2 fluorotelomer unsaturated acid (6:2 FTUA) were detected as early degradation products in cultures (after 72 h) while 5:3 fluorotelomer acid (5:3 FTCA), perfluorohexanoic acid (PFHxA) and perfluoropentanoic acid (PFPeA) were detected as later degradation products (after 168 h). This work provides biochemical and metabolic insights into 6:2 FTS biodegradation by the Actinobacterium D. aurantiaca J3, informing the fate of PFAS in the environment.

Behaviors of 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) in wheat seedlings: Bioaccumulation, biotransformation and ecotoxicity

As a new alternative to perfluorooctane sulfonate (PFOS), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) has been currently used in industrial and consumer applications, which has been frequently detected in environment media. However, the behaviors of 6:2 FTAB in plants are still unclear. This study investigated the bioaccumulation, biotransformation and ecotoxicity of 6:2 FTAB in wheat (Triticum aestivum L.) by hydroponic exposure. 6:2 FTAB was easily taken up by roots with the root concentration factor (RCF) as high as 94.8, but difficult to be acropetally translocated in the shoots with the translocation factor (TF) as low as 0.058. Two intermediates and six terminal perfluorocarboxylic acid (PFCA) metabolites were detected in roots and shoots. The detected metabolites included 6:2 fluorotelomer sulfonic acid (6:2 FTSA), 6:2 fluorotelomer carboxylic acid (6:2 FTCA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutyric acid (PFBA), pentafluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA), and 6:2 FTSA was the main metabolite. 6:2 FTAB significantly reduced the biomass of plant and prevented chlorophyll (Chl) accumulation, while caused no significant change in malondialdehyde (MDA) content. Significant reduction in glutathione (GSH) contents, excess production of reactive oxygen species (ROS), and obvious inhibition of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST) activities were observed, suggesting damage of antioxidant defense systems and failure to detoxication of 6:2 FTAB in wheat. These findings provide important knowledge for the fate of 6:2 FTAB in plants.

Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foam (AFFF) comprise some perfluoroalkyl substances but a larger variety of polyfluoroalkyl substances. Despite their abundance in AFFF, information is lacking on the potential transformation of these polyfluoroalkyl substances. Due to the biological and chemical stability of the repeating perfluoroalkyl -(CF₂)_n- moiety common to all known AFFF-derived PFASs, it is not immediately evident whether the microbial biotransformation mechanisms observed for other organic contaminants also govern the microbial biotransformation of polyfluoroalkyl substances. Herein, we aim to: 1) review the literature on the aerobic or anaerobic microbial biotransformation of AFFF-derived polyfluoroalkyl substances in environmental media; 2) compile and summarize proposed microbial biotransformation pathways for major classes of polyfluoroalkyl substances; 3) identify the dominant biotransformation intermediates and terminal biotransformation products; and 4) discuss these findings in the context of environmental monitoring and source allocation. This analysis revealed that much more is currently known about aerobic microbial biotransformation of polyfluoroalkyl substances, as compared to anaerobic biotransformation. Further, there are some similarities in microbial biotransformations of fluorotelomer and electrochemical fluorination-derived polyfluoroalkyl substances, but differences may be largely due to head group composition. Dealkylation, oxidation, and hydrolytic reactions appear to be particularly important for microbial biotransformation of AFFF-derived polyfluoroalkyl substances, and these biotransformations may lead to formation of some semi-stable intermediates. Finally, this review discusses key knowledge gaps and opportunities for further research.

Target and Nontarget Screening of PFAS in Biosolids, Composts, and Other Organic Waste Products for Land Application in France

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFAS) are increasingly reported in terrestrial and aquatic environments, but their inputs to agricultural lands are not fully understood. Here, we characterized PFAS in 47 organic waste products (OWP) applied in agricultural fields of France, including historical and recent materials. Overall, 160 PFAS from 42 classes were detected from target screening and homologue-based nontarget screening. Target PFAS were low in agriculture-derived wastes such as pig slurry, poultry manure, or dairy cattle manure (median ∑₄₆PFAS: 0.66 μg/kg dry matter). Higher PFAS levels were reported in urban and industrial wastes, paper mill sludge, sewage sludge, or residual household waste composts (median ∑₄₆PFAS: 220 μg/kg). Historical municipal biosolids and composts (1976-1998) were dominated by perfluorooctanesulfonate (PFOS), N-ethyl perfluorooctanesulfonamido acetic acid (EtFOSAA), and cationic and zwitterionic electrochemical fluorination precursors to PFOS. Contemporaneous urban OWP (2009-2017) were rather dominated by zwitterionic fluorotelomers, which represented on average 55% of ∑₁₆₀PFAS (max: 97%). The fluorotelomer sulfonamidopropyl betaines (X:2 FTSA-PrB, median: 110 μg/kg, max: 1300 μg/kg) were the emerging class with the highest occurrence and prevalence in contemporary urban OWP. They were also detected as early as 1985. The study informs for the first time that urban sludges and composts can be a significant repository of zwitterionic and cationic PFAS.

Removal of Zwitterionic PFAS by MXenes: Comparisons with Anionic, Nonionic, and PFAS-Specific Resins

Zwitterionic per- and polyfluoroalkyl substances are increasingly detected in aquatic environments. The magnitude of their concentration and increased frequency of detection worldwide raise questions on their presence in drinking water and associated health risk. Scientific knowledge on the identification of treatment technologies to effectively capture such zwitterionic PFAS from contaminated water sources remains largely unknown. In this study, we investigated the application of anionic organic scavenger ion exchange (IX) resins (A860), nonionic IX resins (XAD 4 and XAD 7), PFAS-specific resins (A694 and A592), and Ti₃C₂ MXenes (novel two-dimensional metal carbides) for the removal of select fluorotelomer zwitterionic PFAS from natural waters. The cumulative removal of zwitterionic PFAS at pH ∼ 7 follows the order: Ti₃C₂ MXenes > A694 > A592 > A860 > XAD 4 ∼ XAD 7. Ti₃C₂ MXenes were able to capture >75% of the total influent zwitterionic PFAS and the performance remained consistent in natural and synthetic water. Ti₃C₂ MXenes also exhibited efficient regeneration (>90% recovery) with 0.4 M Na₂SO₃ solution, while the regeneration efficacy of other IX resins generally remained below 20%. Treatment with ∼180 J/cm² UV dosage in the 0.4 M Na₂SO₃ regenerant brine solution yielded >99.9% reduction in the zwitterionic PFAS concentration indicating that UV-sulfite systems exhibit promising potential for the treatment of zwitterionic PFAS concentrates.

An introduction to the sources, fate, occurrence and effects of endocrine disrupting chemicals released into the environment

Many classes of compounds are known or suspected to disrupt the endocrine system of vertebrate and invertebrate organisms. This review of the sources and fate of selected endocrine disrupting chemicals (EDCs) in the environment includes classes of compounds that are "legacy" contaminants, as well as contaminants of emerging concern. EDCs included for discussion are organochlorine compounds, halogenated aromatic hydrocarbons, brominated flame retardants, per- and polyfluoroalkyl substances, alkylphenols, phthalates, bisphenol A and analogues, pharmaceuticals, drugs of abuse and steroid hormones, personal care products, and organotins. An exhaustive survey of the fate of these contaminants in all environmental media (e.g., air, water, soil, biota, foods and beverages) is beyond the scope of this review, so the priority is to highlight the fate of EDCs in environmental media for which there is a clear link between exposure and endocrine effects in humans or in biota from other taxa. Where appropriate, linkages are also made between the fate of EDCs and regulatory limits such as environmental quality guidelines for water and sediments and total daily intake values for humans.

Transport and fate of aqueous film forming foam in an urban estuary

The deployment of aqueous film forming foams (AFFF) used for firefighting during emergencies and training often releases per- and polyfluoroalkyl substances (PFAS) into the environment. In October 2018, first responders in Providence, RI, USA applied an AFFF during a fuel spill. Due to the proximity of the incident to the upper reaches of Narragansett Bay (NB), an unknown quantity of gasoline and AFFF entered the estuary via surface runoff and stormwater drains. Water samples near the spill were collected approximately 15 h after the incident and analyzed for 24 PFAS. Minor increases in measured PFAS concentrations were observed relative to pre- and post-spill samples at monitoring sites near the incident, except 6:2-fluorotelomer sulfonate (6:2-FTS) that peaked post-spill (max 311 ng/L). After performing the total oxidizable precursor (TOP) assay on water samples and the AFFF concentrate, significant increases in perfluorocarboxylic acids (PFCAs) were observed. One compound, 6:2 fluorotelomer mercaptoalkylamido sulfonate (6:2-FTSAS), was identified as a major component of the AFFF used. Peak areas of 6:2-FTSAS and the degradation product 6:2-FTSAS-sulfoxide corresponded to observed increases in the TOP assay results and were useful as tracers of AFFF in surrounding waters. Elevated levels of PFAS at the time of sampling were limited to a confined area of the Providence River due to river flow and tidal action. Observed concentrations were also compared to hydrodynamic model results, and results confirmed rapid dissipation of AFFF components with distance from the spill. However, modeled results did not capture possible secondary releases of AFFF from local municipal stormwater and sewer infrastructure, as observational data suggest. The multiple lines of evidence of PFAS present in surface waters permitted a better assessment of the potential environmental impacts from products such as AFFF for which the chemical composition is largely unknown.

Analysis of per- and polyfluoroalkyl substances in Houston Ship Channel and Galveston Bay following a large-scale industrial fire using ion-mobility-spectrometry-mass spectrometry

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants of concern because of their ubiquitous presence in surface and ground water; analytical methods that can be used for rapid comprehensive exposure assessment and fingerprinting of PFAS are needed. Following the fires at the Intercontinental Terminals Company (ITC) in Deer Park, TX in 2019, large quantities of PFAS-containing firefighting foams were deployed. The release of these substances into the Houston Ship Channel/Galveston Bay (HSC/GB) prompted concerns over the extent and level of PFAS contamination. A targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based study of temporal and spatial patterns of PFAS associated with this incident revealed presence of 7 species; their levels gradually decreased over a 6-month period. Because the targeted LC-MS/MS analysis was focused on about 30 PFAS molecules, it may have missed other PFAS compounds present in firefighting foams. Therefore, we utilized untargeted LC-ion mobility spectrometry-mass spectrometry (LC-IMS-MS)-based analytical approach for a more comprehensive characterization of PFAS in these water samples. We analyzed 31 samples from 9 sites in the HSC/GB that were collected over 5 months after the incident. Our data showed that additional 19 PFAS were detected in surface water of HSC/GB, most of them decreased gradually after the incident. PFAS features detected by LC-MS/MS correlated well in abundance with LC-IMS-MS data; however, LC-IMS-MS identified a number of additional PFAS, many known to be components of firefighting foams. These findings therefore illustrate that untargeted LC-IMS-MS improved our understanding of PFAS presence in complex environmental samples.

Novel and legacy per- and polyfluoroalkyl substances (PFAS) in freshwater sporting fish from background and firefighting foam impacted ecosystems in Eastern Canada

Emerging PFAS were recently reported at sites impacted by aqueous film-forming foams (AFFFs) and near major manufacturing centers; however, few studies have evaluated whether these can occur far from release sites. Here, newly identified PFAS were investigated in wild sporting fish from boreal freshwater ecosystems (background sites, 2013-2014 summer seasons), compared to fish impacted by a major AFFF release (summer 2013 and autumn 2014). Different freshwater wild sporting fish species (Esox lucius, Esox masquinongy, Micropterus dolomieu, Sander vitreus, Perca flavescens, and Semotilus corporalis, n = 74) were collected from 13 ecosystems (lakes, reservoirs, and rivers) across Eastern Canada. Of 29 quantitative PFAS, 15 compounds were detected in fish from background sites, including perfluorocarboxylates (C_6,8-14), perfluoroalkane sulfonates (C_6,8,10), perfluorooctane sulfonamide (FOSA), 6:2 fluorotelomer sulfonate (6:2 FTSA), 7:3 fluorotelomer carboxylic acid (7:3 FTCA), and a zwitterionic PFAS-perfluorooctane sulfonamidoalkyl betaine (PFOSB). To our knowledge, this is the first report of PFOSB in biota. It is also one of the first reports of anionic fluorotelomers (6:2 FTSA, 7:3 FTCA, 9:3 FTCA) in wildlife from background sites. Long-chain fluorotelomer sulfonamidoalkyl betaines (e.g., 8:2 and 10:2 FTAB), fluorotelomer betaines (e.g., 9:3 and 9:1:2 FTB), and fluorotelomer sulfone propanoic acids (e.g., 8:2 FT(SO₂)-PA, 10:2 FT(SO₂)-PA)) were solely prevalent (up to 97% of summed suspect PFAS) in Smallmouth Bass (M. dolomieu) from the AFFF-impacted site. Perfluorobutane sulfonamide (FBSA), perfluorohexane sulfonamide (FHxSA), 6:2 FTSA and 7:3 FTCA were detected in at least one Smallmouth Bass sample both at the AFFF-impacted and background sites. According to the estimated chronic daily intake and current tolerable daily intake suggested by national agencies, the observed PFOS levels would not pose a health risk to anglers who might consume these wild-caught fish.

Coupled photocatalytic alkaline media as a destructive technology for per- and polyfluoroalkyl substances in aqueous film-forming foam impacted stormwater

The release of aqueous film forming foam (AFFF) from fuel fire events, fire training events, and other activities has resulted in the presence of persistent and recalcitrant per- and polyfluoroalkyl substances (PFAS) in soil and water nationwide. This study describes the degradation and defluorination of PFAS in stormwater collected from an AFFF-impacted site. Silica-based granular media (SGM) containing titanium dioxide was packed into a column reactor and placed between ultraviolet (UV) lamps to excite the photocatalyst within the SGM and generate free radicals to degrade PFAS present in water that was passed through the media. The system was amended with nucleophiles (hydroxyls) to facilitate the destruction of PFAS. Results showed rapid degradation of 17 identified PFAS, including perfluoroalkyl acid (PFAA) precursors, perfluorosulfonic acids (PFSAs), and perfluorocarboxylic acids (PFCAs). Significant defluorination was observed, indicating PFAS destruction as a result of the coupled photocatalytic and nucleophilic attack. Column reactor experiment findings indicate SGM in the presence of UV light passively degraded a mixture of PFAS in a concentrated waste stream at ambient conditions.

PFAS Analysis with Ultrahigh Resolution 21T FT-ICR MS: Suspect and Nontargeted Screening with Unrivaled Mass Resolving Power and Accuracy

Per- and polyfluoroalkyl substances (PFASs) are a large family of thousands of chemicals, many of which have been identified using nontargeted time-of-flight and Orbitrap mass spectrometry methods. Comprehensive characterization of complex PFAS mixtures is critical to assess their environmental transport, transformation, exposure, and uptake. Because 21 tesla (T) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest available mass resolving power and sub-ppm mass errors across a wide molecular weight range, we developed a nontargeted 21 T FT-ICR MS method to screen for PFASs in an aqueous film-forming foam (AFFF) using suspect screening, a targeted formula database (C, H, Cl, F, N, O, P, S; ≤865 Da), isotopologues, and Kendrick-analogous mass difference networks (KAMDNs). False-positive PFAS identifications in a natural organic matter (NOM) sample, which served as the negative control, suggested that a minimum length of 3 should be imposed when annotating CF₂-homologous series with positive mass defects. We putatively identified 163 known PFASs during suspect screening, as well as 134 novel PFASs during nontargeted screening, including a suspected polyethoxylated perfluoroalkane sulfonamide series. This study shows that 21 T FT-ICR MS analysis can provide unique insights into complex PFAS composition and expand our understanding of PFAS chemistries in impacted matrices.

Reduced bioaccumulation of fluorotelomer sulfonates and perfluoroalkyl acids in earthworms (Eisenia fetida) from soils amended with modified clays

Soils contaminated by per- and polyfluoroalkyl substances (PFAS) pose long-term sources to adjacent water bodies and soil invertebrates. The study investigated the stabilization using a modified clay adsorbent (FLUORO-SORB100®) in reducing the bioaccumulation of 13 anionic PFAS by earthworms (Eisenia fetida), as compared to coal-based granular activated carbon. The target PFAS included four perfluoroalkyl sulfonates such as perfluorooctane sulfonate (PFOS), six perfluoroalkyl carboxylates (e.g., perfluorooctanoate PFOA), and three (X:2) fluorotelomer sulfonates. Laboratory-spiked surface soil and the soil collected from a site contaminated by aqueous film-forming foams were examined. Both adsorbents resulted in reduced earthworm PFAS body burdens at the end of the 28-day uptake phase. The highest adsorbent amendment concentration (4 w/w%) was most effective, achieving >95% reduction of PFAS body burden. Soil leaching tests indicated better immobilization performance by the clay adsorbent for most analytes; in comparison, the activated carbon performed better at reducing total PFAS body burdens, possibly owing to the avoidance of larger-sized particles by earthworms. Strong positive logarithm relationships were observed between leachate concentrations and earthworm body burdens for most PFAS in the spiked soil. The study demonstrated that stabilization of PFAS using modified clay adsorbents can achieve concurrent benefits of lowering leachability and reducing bioaccumulation.

Per- and Polyfluoroalkyl Substances in Contaminated Soil and Groundwater at Airports: A Canadian Case Study

The occurrence of 93 classes of per- and polyfluoroalkyl substances (PFASs) was investigated at aqueous film-forming foam (AFFF)-impacted sites of four Canadian airports. Surface/subsurface soil and groundwater samples were characterized using high-resolution mass spectrometry (HRMS) and an improved total oxidizable precursor (TOP) assay. PFAS profiles, loads, and spatial trends were highly site-specific, influenced by the AFFF use history, variations in sorption, transport, and in situ transformation potential of PFASs. All sites have been impacted by more than one AFFF chemistry, with the active firefighter training area exhibiting a greater PFAS variety and total PFAS burden than decommissioned sites. Zwitterionic and cationic compounds composed a large percentage (34.5-85.5%) of the total PFAS mass in most surface soil samples in the source zone but a relatively low percentage (<20%) in groundwater samples. Background soils surrounding the source zone contained predominantly unidentified precursors attributed to atmospheric deposition, while in AFFF-impacted soils, precursors originating from AFFFs can be largely captured by HRMS using available suspect lists. Horizontal transfer of PFASs in surface soils was limited, but vertical migration down the soil column occurred even in locations of low permeability. This study provides a critical data set to support developing new priority analyte lists and integrating TOP assay for comprehensive PFAS monitoring at AFFF-impacted sites.

PFAS Molecules: A Major Concern for the Human Health and the Environment

Per- and polyfluoroalkyl substances (PFAS) are a group of over 4700 heterogeneous compounds with amphipathic properties and exceptional stability to chemical and thermal degradation. The unique properties of PFAS compounds has been exploited for almost 60 years and has largely contributed to their wide applicability over a vast range of industrial, professional and non-professional uses. However, increasing evidence indicate that these compounds represent also a serious concern for both wildlife and human health as a result of their ubiquitous distribution, their extreme persistence and their bioaccumulative potential. In light of the adverse effects that have been already documented in biota and human populations or that might occur in absence of prompt interventions, the competent authorities in matter of health and environment protection, the industries as well as scientists are cooperating to identify the most appropriate regulatory measures, substitution plans and remediation technologies to mitigate PFAS impacts. In this review, starting from PFAS chemistry, uses and environmental fate, we summarize the current knowledge on PFAS occurrence in different environmental media and their effects on living organisms, with a particular emphasis on humans. Also, we describe present and provisional legislative measures in the European Union framework strategy to regulate PFAS manufacture, import and use as well as some of the most promising treatment technologies designed to remediate PFAS contamination in different environmental compartments.

Density Functional Theory Calculations Decipher Complex Reaction Pathways of 6:2 Fluorotelomer Sulfonate to Perfluoroalkyl Carboxylates Initiated by Hydroxyl Radical

6:2 Fluorotelomer sulfonate (6:2 FTSA) is a ubiquitous environmental contaminant belonging to the family of per- and polyfluoroalkyl substances. Previous studies showed that hydroxyl radical (^•OH) efficiently transforms 6:2 FTSA into perfluoroalkyl carboxylates (PFCAs) of different chain lengths (C2-C7), yet the reaction mechanisms were not elucidated. This study used density functional theory (DFT) calculations to map the entire reaction path of 6:2 FTSA initiated by ^•OH and experimentally verified the theoretical results. Optimal reaction pathways were obtained by comparing the rate constants calculated from the transition-state theory. We found that 6:2 FTSA was first transformed to C7 PFCA and C₆F₁₃^•; C₆F₁₃^• was then further reacted to C2-C6 PFCAs. The parallel addition of ^•OH and O₂ to C_nF_2n+1^• was essential to producing C2-C6 PFCAs. The critical step is the generation of alkoxyl radicals, which withdraw electrons from the adjacent C-C groups to result in chain cleavage. The validity of the calculated optimal reaction pathways was further confirmed by the consistency with our experimental data in the aspects of O₂ involvement, identified intermediates, and the final PFCA profile. This study provides valuable insight into the transformation of polyfluoroalkyl substances containing aliphatic carbons in ^•OH-based oxidation processes.

Simulating Impacts of Biosparging on Release and Transformation of Poly- and Perfluorinated Alkyl Substances from Aqueous Film-Forming Foam-Impacted Soil

Poly- and perfluorinated alkyl substances (PFASs) frequently co-occur with fuel-derived contaminants because of the use of aqueous film-forming foam (AFFF). Biosparging is a common remediation technology that injects oxygen into the saturated zone to encourage aerobic biodegradation, thereby altering aquifer redox conditions and potentially facilitating the biotransformation of polyfluorinated substances. Between 136 and 280 pore volumes of nitrogen-sparged or oxygen-sparged artificial groundwater amended with toluene were pumped through four saturated, AFFF-impacted soil columns to assess impacts on PFAS release and transformation. Column effluents and soils were analyzed for PFASs by high-resolution mass spectrometry. Significantly higher concentrations of five PFASs eluted from O₂-sparged columns compared to N₂-sparged columns shortly after sparging was initiated. The mass fractions eluted of many zwitterionic, sulfonamide-based PFASs were higher in both sets of columns than unaltered, non-biostimulated columns. Mass balance calculations suggested the transformation of sulfonamide-based precursors to perfluorinated sulfonamides (i.e., perfluorohexanesulfonamide) in oxygen- and nitrogen-sparged columns: recoveries of perfluorinated sulfonamides were 158-235% for C3-C6 homologs but recoveries of several prominent sulfonamide-based zwitterions were low. For example, the recovery of n-carboxyethyldimethyl-ammoniopropyl perfluorohexanesulfonamide was 9-13%. These results suggest biosparging can enhance the transformation and release of PFASs in saturated soils, which has important implications for site characterization and remediation.

Environmental Sources, Chemistry, Fate, and Transport of Per- and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting

A Society of Environmental Toxicology and Chemistry (SETAC) Focused Topic Meeting (FTM) on the environmental management of per- and polyfluoroalkyl substances (PFAS) convened during August 2019 in Durham, North Carolina (USA). Experts from around the globe were brought together to critically evaluate new and emerging information on PFAS including chemistry, fate, transport, exposure, and toxicity. After plenary presentations, breakout groups were established and tasked to identify and adjudicate via panel discussions overarching conclusions and relevant data gaps. The present review is one in a series and summarizes outcomes of presentations and breakout discussions related to (1) primary sources and pathways in the environment, (2) sorption and transport in porous media, (3) precursor transformation, (4) practical approaches to the assessment of source zones, (5) standard and novel analytical methods with implications for environmental forensics and site management, and (6) classification and grouping from multiple perspectives. Outcomes illustrate that PFAS classification will continue to be a challenge, and additional pressing needs include increased availability of analytical standards and methods for assessment of PFAS and fate and transport, including precursor transformation. Although the state of the science is sufficient to support a degree of site-specific and flexible risk management, effective source prioritization tools, predictive fate and transport models, and improved and standardized analytical methods are needed to guide broader policies and best management practices. Environ Toxicol Chem 2021;40:3234-3260. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Perfluoroalkyl acids on suspended particles: Significant transport pathways in surface runoff, surface waters, and subsurface soils

Eroded particles from the source zone could transport a high concentration of perfluoroalkyl acids (PFAAs) to sediments and water bodies. Yet, the contribution of suspended particles has not been systematically reviewed. Analyzing reported studies, we quantitatively demonstrate that suspended particles in surface water can contain significantly higher concentrations of PFAAs than the sediment below, indicating the source of suspended particles are not the sediment but particles eroded and carried from the source zone upstream. The affinity of PFAAs to particles depends on the particle composition, including organic carbon fraction and iron or aluminum oxide content. In soils, most PFAAs are retained within the top 5 m below the ground surface. The distribution of PFAAs in the subsurface varies based on site properties and local weather conditions. The depth corresponding to the maximum concentration of PFAA in soil decreases with an increase in soil organic carbon or rainfall amount received in the catchment areas. We attribute a greater accumulation of PFAAs near the upper layer of the subsurface to an increase in the accumulation of particles eroded from source zones upstream receiving heavy rainfall. Precursor transformation in the aerobic zone is significantly higher than in the anaerobic zone, thereby making the aerobic subsurface zone serve as a long-term source of groundwater pollution. Collectively, these results suggest that suspended particles, often an overlooked vector for PFAAs, can be a dominant pathway for the transport of PFAAs in environments.

Enhanced Recovery of Per- and Polyfluoroalkyl Substances (PFASs) from Impacted Soils Using Heat Activated Persulfate

Varying transport potential of cationic, zwitterionic, and anionic per- and polyfluoroalkyl substances (PFASs) may pose challenges for remediation of aqueous film forming foam (AFFF) impacted sites, particularly during groundwater extraction. Slow desorption of stronger sorbing, zwitterionic, and cationic PFASs may cause extended remediation times and rebound in aqueous PFAS concentrations. Persulfate oxidation has the potential to convert a complex mixture of PFASs into a simpler and more recoverable mixture of perfluoroalkyl acids (PFAAs). AFFF-impacted soils were treated with heat-activated persulfate in batch reactors and subjected to 7-day leaching experiments. Soil and water were analyzed using a combination of targeted and high resolution liquid chromatography mass spectrometry techniques as well as the total oxidizable precursors assay. Following oxidation, total PFAS composition showed the expected shift to a higher fraction of PFAAs, and this led to higher total PFAS leaching in pretreated reactors (108-110%) vs control reactors (62-90%). In both pretreated and control soils, precursors that remained following leaching experiments were 61-100% cationic and zwitterionic. Results suggest that persulfate pretreatment of soils has promise as an enhanced recovery technique for remediation of total PFASs in impacted soils. They also demonstrate that PFAS distribution may have been altered at sites where in situ chemical oxidation was applied to treat co-occurring contaminants of concern.

Environmental Source Tracking of Per- and Polyfluoroalkyl Substances within a Forensic Context: Current and Future Techniques

The source tracking of per- and polyfluoroalkyl substances (PFASs) is a new and increasingly necessary subfield within environmental forensics. We define PFAS source tracking as the accurate characterization and differentiation of multiple sources contributing to PFAS contamination in the environment. PFAS source tracking should employ analytical measurements, multivariate analyses, and an understanding of PFAS fate and transport within the framework of a conceptual site model. Converging lines of evidence used to differentiate PFAS sources include: identification of PFASs strongly associated with unique sources; the ratios of PFAS homologues, classes, and isomers at a contaminated site; and a site's hydrogeochemical conditions. As the field of PFAS source tracking progresses, the development of new PFAS analytical standards and the wider availability of high-resolution mass spectral data will enhance currently available analytical capabilities. In addition, multivariate computational tools, including unsupervised (i.e., exploratory) and supervised (i.e., predictive) machine learning techniques, may lead to novel insights that define a targeted list of PFASs that will be useful for environmental PFAS source tracking. In this Perspective, we identify the current tools available and principal developments necessary to enable greater confidence in environmental source tracking to identify and apportion PFAS sources.

Fate and transport of per- and polyfluoroalkyl substances (PFASs) in the vadose zone

Per- and polyfluoroalkyl substances (PFASs) are a heterogeneous group of persistent organic pollutants that have been detected in various environmental compartments around the globe. Emerging research has revealed the preferential accumulation of PFASs in shallow soil horizons, particularly at sites impacted by firefighting activities, agricultural applications, and atmospheric deposition. Once in the vadose zone, PFASs can sorb to soil, accumulate at interfaces, become volatilized, be taken up in biota, or leach to the underlying aquifer. At the same time, polyfluorinated precursor species may transform into highly recalcitrant perfluoroalkyl acids, changing their chemical identity and thus transport behavior along the way. In this review, we critically discuss the current state of the knowledge and aim to interconnect the complex processes that control the fate and transport of PFASs in the vadose zone. Furthermore, we identify key challenges and future research needs. Consequently, this review may serve as an interdisciplinary guide for the risk assessment and management of PFAS-contaminated sites.

Removal of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) Using Ion-Exchange and Nonionic Resins

Despite benefits to the firefighting industry, the release of per- and polyfluoroalkyl substances (PFASs) from aqueous film-forming foam (AFFF) into aquatic systems poses significant risks to human health and other organisms. While anion-exchange technologies have proven to be effective for removing perfluoroalkyl acids (PFAAs) from water, their effectiveness for removing the diverse PFAS structures discovered in AFFF remains unknown. Here, we report on the adsorption of 75 PFASs, including 63 polyfluorinated substances, in a diluted AFFF mixture using 14 commercially available ion-exchange (IX)/nonionic resins and granular activated carbon (GAC). Results showed that anion-exchange resins (AERs) exhibited significant adsorption of PFASs compared to cation-exchange resins (CERs), nonionic resins (NIRs), and GAC regardless of the PFAS's predicted charge. Isotherm data showed that macroporous AERs have a higher PFAS adsorption capacity compared to gel-type AERs. Cross-correlation comparison of PFAS/Cl^- selectivity coefficients (K_ex) for each PFAS-AER combination showed that the hydrophobicity of the AER functional group, and polymer matrix played a dominant role in determining resin affinity for PFASs. PFAS structural characteristics also significantly affected adsorption, with increasing chain length and a net negative charge increasing the extent of adsorption. Results from this study provide guidelines for the selection of resins to adsorb a wider range of PFASs and meaningful insights for the development of quantitative models for IX treatment of AFFF-impacted water.

Stability of Nitrogen-Containing Polyfluoroalkyl Substances in Aerobic Soils

Zwitterionic per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foams (AFFFs) could face diverse environmental fates once released at military bases, airports, fire-training areas, and accidental release sites. Here, we studied for the first time the transformation potential of four electrochemical fluorination (ECF)-based PFAS zwitterions (two carboxyl betaines and two tertiary amines) in aerobic soils. The two perfluoroalkyl sulfonamide derivatives were precursors to perfluorooctanesulfonate (PFOS), while the amide derivatives were precursors to perfluorooctane carboxylate (PFOA). These zwitterions and four other previously reported zwitterions or cations were compared for their transformation pathways and kinetics. Structural differences, especially the nitrogen head groups, largely influenced the persistence of these compounds in aerobic soils. The perfluoroalkyl sulfonamide-based compounds showed higher microbial stability than the corresponding perfluoroalkyl amide-based ones. Their stability in aerobic soils is ranked based on the magnitude of DT₅₀ (time for 50% of substance to disappear): quaternary ammonium ≈ carboxyl betaine ≫ tertiary amine > amine oxide. The PFASs containing quaternary ammonium or betaine groups showed high stability in soils, with the longest DT₅₀ likely to be years or decades, while those with tertiary amine or amine oxide groups showed DT₅₀ of weeks or months. These eight ECF-based precursors provide insights into the degradation pathways and persistence in surface soils of other perfluoroalkyl cations and zwitterions present in AFFFs.

Sequestration and potential release of PFAS from spent engineered sorbents

Per- and poly-fluoroalkyl substances (PFAS) have contaminated land and water at numerous sites worldwide that now require remediation. The most common approach for treating contaminated water currently relies on removal of PFAS by sorption. The spent sorbents loaded with PFAS can potentially be disposed of at landfills, provided the sorbed contaminants remain sequestered and certain risk criteria are met. Hence, it is essential that remediation sorbents (i) rapidly adsorb a large variety of PFAS under varying water chemistry conditions, and (ii) do not release the adsorbed PFAS in due course. This review aims at establishing the current state of knowledge about the potential release of PFAS that may occur during and after treatment. The scientific literature currently provides data for a very restricted range of long-chain PFAS. Our knowledge of the dynamics of PFAS adsorption processes on engineered sorbents is limited, and even less is known about their desorption processes. The sorption of PFAS can be strongly affected by changes in the solution pH, ionic strength and dissolved organic matter content, and the process is also subject to complex competition mechanisms in the presence of other PFAS as well as organic contaminants and inorganic salts. Several studies suggest that changes in one or several of these factors may trigger the release of PFAS from engineered sorbents. This phenomenon is more likely to occur for PFAS with shorter carbon chain lengths (<C8), at high pH and in the presence of other PFAS or other anionic sorbates. The release of PFAS from spent sorbent materials, stored or deposited under conditions that vary over time, is highly undesirable, as they can potentially become a secondary source of PFAS in the environment. Our analysis identifies a number of knowledge-gaps that should be urgently addressed in order to design sustainable remediation solutions, including an improved management of spent sorbent materials.

Software Comparison for Nontargeted Analysis of PFAS in AFFF-Contaminated Soil

Per- and polyfluoroalkyl substances (PFAS) are an emerging class of toxic environmental contaminants. Over 7500 PFAS exist, but reference standards are available for less than 2% of compounds. Nontargeted analysis using liquid chromatography-high-resolution tandem mass spectrometry is therefore an essential technique for increasing the analytical coverage of PFAS present in environmental samples. However, typical nontargeted data analysis is laborious and has a steep learning curve. Recently, FluoroMatch, a new open source, vendor neutral software, was published specifically for automating data processing for nontargeted analysis of PFAS and generating PFAS libraries. Here, we analyze soil contaminated with PFAS based aqueous film forming foam (AFFF) and compare the results produced by data analysis workflows using FluoroMatch and Compound Discoverer, an established nontargeted analysis program. High-confidence PFAS annotations were nearly identical between the methods, with 27 out of 32 compounds found using both Compound Discoverer and the modular version of FluoroMatch. Twenty-two high-confidence annotations were found using the comprehensive FluoroMatch Flow. The FluoroMatch method was faster and required significantly less manual curation than the Compound Discoverer method. Both platforms produced high-quality data that were useful for assessing PFAS contamination in the soil.

Evaluation of extraction workflows for quantitative analysis of per- and polyfluoroalkyl substances: A case study using soil adjacent to a landfill

Specific aspects of previously reported extraction workflows, for measurement of per- and polyfluoroalkyl substances (PFAS) in solid matrices, have not been adequately interrogated. The objective of this study was to explore the importance of each workflow step in providing the most appropriate extraction for a comprehensive set of PFAS (51 different species) in soil. We compared different procedures, including two pre-extraction set ups (overnight handling of samples prior to extraction), two extraction solvents (methanol (MeOH), and acetonitrile (ACN)), two extraction solvent volumes (10 mL and 8.5 mL), and two post-extraction cleanup strategies (ENVI-Carb and ion-pair). Of the 51 species targeted, 21 were at quantifiable levels in soil samples collected adjacent to a landfill, of which 13 PFAS were consistently detected among the different extraction workflows. Overall, results showed no significant difference in PFAS concentration between different extraction solvents and cleanup strategies. Perfluoropentanoic acid, perfluorohexanoic acid, and perfluorooctanoic acid had the highest concentrations in all extraction workflows, accounting for nearly 13%, 38%, and 17% of the total monitored PFAS (ΣPFAS), respectively. While final concentration values were similar across methods, recovery and accuracy studies showed that MeOH had the best recovery, with 88% of the isotopically labeled PFAS standards showing extraction recovery within the acceptable range of 80% to 120% (compared to 14% of isotopically labeled PFAS standards in workflows using ACN). Upon examination of additional cleanup steps, 67% of monitored PFAS (out of 51 total PFAS monitored), on average, exhibited higher accuracy (relative error ≤20%) using ENVI-Carb clean up (in comparison with 51% in workflows using ion pair clean up). Results also demonstrated that larger volumes of MeOH (and subsequent re-extractions) did not yield a better recovery, enabling a reduction in overall analysis time and cost in comparison to many published methods.

PFAS soil and groundwater contamination via industrial airborne emission and land deposition in SW Vermont and Eastern New York State, USA

In order to understand the extent to which airborne PFAS emission can impact soil and groundwater, we conducted a sampling campaign in areas of conserved forest lands near Bennington, VT/Hoosick Falls, NY. This has been home to sources of PFAS air-emissions from Teflon-coating operations for over 50 years. Since 2015, the Vermont and New York Departments of Environmental Conservation have documented ∼1200 residential wells and two municipal water systems across a 200 km2 area contaminated with perfluorooctanoic acid (PFOA). Given the large areal extent of the plume, and the fact that much of the contaminated area lies up-gradient and across rivers from manufactures, we seek to determine if groundwater contamination could have resulted primarily from air-emission, land deposition, and subsequent leaching to infiltrating groundwater. Sampling of soils and groundwater in the Green Mountain National Forest (GMNF) downwind of factories shows that both soil and groundwater PFOA contamination extend uninterrupted from inhabited areas into conserved forest lands. Groundwater springs and seeps in the GMNF located 8 km downwind, but >300 meters vertically above factories, contain up to 100 ppt PFOA. Our results indicate that air-emitted PFAS can contaminate groundwater and soil in areas outside of those normally considered down-gradient of a source with respect to regional groundwater flow.

Biotransformation of perfluoroalkyl acid precursors from various environmental systems: advances and perspectives

Perfluoroalkyl acids (PFAAs) are widely used in industrial production and daily life because of their unique physicochemical properties, such as their hydrophobicity, oleophobicity, surface activity, and thermal stability. Perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) are the most studied PFAAs due to their global occurrence. PFAAs are environmentally persistent, toxic, and the long-chain homologs are also bioaccumulative. Exposure to PFAAs may arise directly from emission or indirectly via the environmental release and degradation of PFAA precursors. Precursors themselves or their conversion intermediates can present deleterious effects, including hepatotoxicity, reproductive toxicity, developmental toxicity, and genetic toxicity. Therefore, exposure to PFAA precursors constitutes a potential hazard for environmental contamination. In order to comprehensively evaluate the environmental fate and effects of PFAA precursors and their connection with PFSAs and PFCAs, we review environmental biodegradability studies carried out with microbial strains, activated sludge, plants, and earthworms over the past decade. In particular, we review perfluorooctyl-sulfonamide-based precursors, including perfluroooctane sulfonamide (FOSA) and its N-ethyl derivative (EtFOSA), N-ethyl perfluorooctane sulfonamido ethanol (EtFOSE), and EtFOSE-based phosphate diester (DiSAmPAP). Fluorotelomerization-based precursors are also reviewed, including fluorotelomer alcohols (FTOH), fluorotelomer sulfonates (FTSA), and a suite of their transformation products. Though limited information is currently available on zwitterionic PFAS precursors, a preliminary review of data available for 6:2 fluorotelomer sulfonamide betaine (FTAB) was also conducted. Furthermore, we update and refine the recent knowledge on biotransformation strategies with a focus on metabolic pathways and mechanisms involved in the biotransformation of PFAA precursors. The biotransformation of PFAA precursors mainly involves the cleavage of carbon-fluorine (C-F) bonds and the degradation of non-fluorinated functional groups via oxidation, dealkylation, and defluorination to form shorter-chained PFAAs. Based on the existing research, the current problems and future research directions on the biotransformation of PFAA precursors are proposed.

Target, Nontarget, and Suspect Screening and Temporal Trends of Per- and Polyfluoroalkyl Substances in Marine Mammals from the South China Sea

Per- and polyfluoroalkyl substances (PFASs) have been manufactured and widely used for over 60 years. Currently, there are thousands of marketed PFASs, but only dozens of them are routinely monitored. This work involved target, nontarget, and suspect screening of PFASs in the liver of Indo-Pacific humpback dolphin (Sousa chinensis) and finless porpoise (Neophocaena phocaenoides), two resident marine mammals in the South China Sea, stranded between 2012 and 2018. Among the 21 target PFASs, perfluorooctane sulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) predominated in the samples, accounting for 46 and 30% of the total PFASs, respectively. Significantly higher total target PFAS concentrations (p < 0.05) were found in dolphin liver samples [3.23 × 10³ ± 2.63 × 10³ ng/g dry weight (dw)] than in porpoise liver samples (2.63 × 10³ ± 1.10 × 10³ ng/g dw). Significant increasing temporal trends (p < 0.05) were found in the concentrations of two emerging PFASs, perfluoroethylcyclohexane sulfonate and 2,3,3,3-tetrafluoro-2-propanoate in porpoises, indicating increasing pollution by these emerging PFASs. Forty-four PFASs from 9 classes were additionally identified by nontarget and suspect screening, among which 15 compounds were reported for the first time in marine mammals. A primary risk assessment showed that the emerging PFAS 6:2 Cl-PFESA could have possible adverse effects in terms of reproductive injury potential on most of the investigated cetaceans.