Fluorotelomer Unsaturated Carboxylic Acid Research Articles

Distinctive biotransformation and biodefluorination of 6:2 versus 5:3 fluorotelomer carboxylic acids by municipal activated sludge

Fluorotelomer carboxylic acids (FTCAs) represent an important group of per- and polyfluoroalkyl substances (PFAS) given their high toxicity, bioaccumulation potential, and frequent detection in landfill leachates and PFAS-impacted sites. In this study, we assessed the biodegradability of 6:2 FTCA and 5:3 FTCA by activated sludges from four municipal wastewater treatment plants (WWTPs) in the New York Metropolitan area. Coupling with 6:2 FTCA removal, significant fluoride release (0.56∼1.83 F-/molecule) was evident in sludge treatments during 7 days of incubation. Less-fluorinated transformation products (TPs) were formed, including 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorobutanoic acid (PFBA). In contrast, little fluoride (0.01∼0.09 F-/molecule) was detected in 5:3 FTCA-dosed microcosms, though 25∼68% of initially dosed 5:3 FTCA was biologically removed. This implies the dominance of “non-fluoride-releasing pathways” that may contribute to the formation of CoA adducts or other conjugates over 5:3 FTCA biotransformation. The discovery of defluorinated 5:3 FTUCA revealed the possibility of microbial attacks of the C-F bond at the γ carbon to initiate the transformation. Microbial community analysis revealed the possible involvement of 9 genera, such as Hyphomicrobium and Dechloromonas, in aerobic FTCA biotransformation. This study unraveled that biotransformation pathways of 6:2 and 5:3 FTCAs can be divergent, resulting in biodefluorination at distinctive degrees. Further research is underscored to uncover the nontarget TPs and investigate the involved biotransformation and biodefluorination mechanisms and molecular basis.

Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm.

The susceptibility of 19 representative per- and polyfluoroalkyl substances (PFAS) to direct photolysis and defluorination under far-UVC 222 nm irradiation was investigated. Enhanced photolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), and GenX, compared to that at conventional 254 nm irradiation on a similar fluence basis, while other PFAS showed minimal decay. For degradable PFAS, up to 81% of parent compound decay (photolysis rate constant (k222nm) = 8.19-34.76 L·Einstein-1; quantum yield (Φ222nm) = 0.031-0.158) and up to 31% of defluorination were achieved within 4 h, and the major transformation products were shorter-chain PFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride, and humic acids had mild impacts, while nitrate significantly affected PFAS photolysis/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic decay. The slower degradation of short-chain PFCAs than long-chain ones is related to molar absorptivity and may also be influenced by chain-length dependent structural factors, such as differences in pKa, conformation, and perfluoroalkyl radical stability. Meanwhile, theoretical calculations indicated that the widely proposed HF elimination from the alcohol intermediate (CnF2n+1OH) of PFCA is an unlikely degradation pathway due to high activation barriers. These new findings are useful for further development of far-UVC technology for PFAS in water treatment.

Degradation of 8:2 fluorotelomer carboxylic acid (8:2 FTCA) by plants and their co-existing microorganisms

8:2 fluorotelomer carboxylic acid (8:2 FTCA), an important precursor of perfluorocarboxylic acids (PFCAs), is widely detected in environment and biotas. Hydroponic exposures were conducted to investigate the accumulation and metabolism of 8:2 FTCA in wheat (Triticum aestivum L.) and pumpkin (Cucurbita maxima L.). Endophytic and rhizospheric microorganisms co-existing with the plants were isolated to investigate their contributions to degrade 8:2 FTCA. Wheat and pumpkin roots could take up 8:2 FTCA efficiently with the root concentration factor (RCF) as 5.78 and 8.93, respectively. 8:2 FTCA could be biotransformed to 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 7:3 fluorotelomer carboxylic acid (7:3 FTCA), and seven PFCAs with 2–8 carbon chain length in plant roots and shoots. Cytochromes P450 (CYP450) and glutathione-S-transferase (GST) activities in plants were significantly increased, while flavin-dependent monooxygenases (FMOs) activities were not changed, suggesting that CYP 450 and GST were involved in the transformation of 8:2 FTCA in plant tissues. Twelve 8:2 FTCA-degrading endophytic (8 strains) and rhizospheric (4 strains) bacterial strains were isolated from root interior, shoot interior and rhizosphere of plants, respectively. These bacteria were identified as Klebsiella sp. based on the morphology and 16S rDNA sequence, and they could biodegrade 8:2 FTCA to intermediates and stable PFCAs.

Electrochemical Oxidation of 6:2 Polyfluoroalkyl Phosphate Diester-Simulation of Transformation Pathways and Reaction Kinetics with Hydroxyl Radicals.

Polyfluoroalkyl phosphate diesters (diPAPs) are widely used for paper and cardboard impregnation and discharged via waste streams from production processes and consumer products. To improve the knowledge about the environmental fate of diPAPs, electrochemical oxidation (EO) was used to characterize the transformation pathways and reaction kinetics. 6:2 diPAP was transformed electrochemically to perfluorocarboxylic acids (C5-C7 PFCAs) and two intermediates (6:2 fluorotelomer carboxylic acid, FTCA, and 6:2 fluorotelomer unsaturated carboxylic acid, FTUCA). EO of potential intermediates 6:2 monoPAP and 6:2 fluorotelomer alcohol (FTOH) showed similar transformation products but with different ratios. We show that 6:2 diPAP is initiated by OH radical (•OH) reactions, as evidenced by the measured steady-state concentrations of •OH with the probe molecule terephthalic acid, quenching experiments, and pH dependency of the reaction. PFHpA was the main product of 6:2 diPAP oxidation, and it was formed in a pseudo-first-order reaction for which a bimolecular rate constant was estimated to be = 9.4(±1.4) × 107 M-1 s-1 by an initial rate approach. This can be utilized to estimate the environmental half-life of 6:2 diPAP for the reaction with •OH and the formation kinetics of persistent PFCAs.

Uptake, Tissue Distribution, and Elimination of 8:2 Polyfluoroalkyl Phosphate Diesters in Mytilus galloprovincialis.

Although the distribution of 8:2 polyfluoroalkyl phosphate diester (8:2 diPAP) in aquatic environments has been reported, details on its uptake, tissue specificity, and elimination in bivalve mollusks remain to be clarified. The present study is the first report on the accumulation and elimination of 8:2 diPAP in mussels (Mytilus galloprovincialis). The tissue-specific accumulation and depuration of 8:2 diPAP and its metabolites were investigated via semistatic seawater exposure (8:2 diPAP at a nominal concentration of 10 μg/L), through water-borne exposure with static daily renewal over a 72-h exposure period and a 360-h depuration period. The digestive gland was found to be the target organ where accumulation and biotransformation primarily occur. The bioaccumulation factor values (mL/g dry wt) in different organs were in the following order: digestive gland (1249) > adductor muscle (315) > gills (289) > gonad (82.9) > mantle (33.0). Moreover, the distribution of 8:2 diPAP among tissues may be related to the total protein content. The 8:2 diPAP tended to be excreted in feces. The compounds 8:2 fluorotelomer carboxylic acid, 8:2 fluorotelomer unsaturated carboxylic acid, 7:3 fluorotelomer carboxylic acid, perfluorooctanoic acid, and perfluoroheptanoic acid were detected and quantified as phase I metabolites, and the concentration of all phase I metabolites relative to the 8:2 diPAP concentration (72 h) was 0.304 mol%. A phase II metabolite, 8:2 fluorotelomer alcohol conjugated with sulfate, was detected but not quantitated in the digestive gland. A biotransformation pathway of 8:2 diPAP in M. galloprovincialis was proposed on the basis of the results obtained in the present study and previous studies. These findings improve our understanding of the accumulation of perfluorocarboxylic acids in bivalve mollusks.Environ Toxicol Chem 2021;40:1992-2004. © 2021 SETAC.

Biotransformation and tissue bioaccumulation of 8:2 fluorotelomer alcohol in broiler by oral exposure

In order to examine whether 8:2 FTOH exposure would lead to a contamination risk of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in broiler derived food, the biotransformation, and tissue distribution and accumulation of 8:2 FTOH following oral exposure in male broilers were investigated. The main metabolites of 8:2 FTOH in plasma and six tissues (muscle, liver, kidney, fat, heart, and lungs) identified by LC-Q-TOF were 2-perfluorooctyl ethanoic acid (8:2 FTCA), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 3-perfluoroheptyl propanoic acid (7:3 FTCA), perfluoropentanoic acid (PFPeA), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluorononanoic acid (PFNA), 8:2 FTOH glucuronide conjugate, and 8:2 FTOH sulfate conjugate. The tissue distribution and bioaccumulation of 8:2 FTOH and its unconjugated metabolites were determinated by LC-MS/MS. 8:2 FTOH was quickly depleted in plasma and all six tested tissues, while PFOA, PFNA, and 7:3 FTCA showed strong accumulation in blood and all six examined tissues and were eliminated more slowly than the other metabolites. The tissues with the highest accumulation levels for 8:2 FTOH and its metabolites were heart, kidneys and liver, and the tissue with the lowest accumulation levels was muscle. The elimination half-lifes of PFNA in kidney and 7:3 FTCA in lung were longer compared to those of other metabolites in all six determined tissues. Thus, PFNA and 7:3 FTCA can be selected as potential biomonitoring markers after 8:2 FTOH exposure. This study has improved our understanding of 8:2 FTOH biotransformation and tissue bioaccumulation in broilers, which will help us monitor human exposure risk via food derived from broilers polluted by 8:2 FTOH.

Occurrence and Degradation Potential of Fluoroalkylsilane Substances as Precursors of Perfluoroalkyl Carboxylic Acids.

Polyfluoroalkylsilanes (PFASis) are a class of artificial chemicals with wide applications in surface coating, which arouse attention due to their hydrophobic/oleophobic properties and potential biological effects. In this study, a robust high-resolution mass spectrometry method through direct injection into a Fourier transform ion cyclotron resonance instrument was established, with the aid of CF2-scaled Kendrick mass defect analysis and isotope fine structure elucidation. The occurrence of 8:2 polyfluoroalkyl trimethoxysilane (8:2 PTrMeOSi) and 8:2 polyfluoroalkyl triethoxysilane (8:2 PTrEtOSi), as well as their cationic adducts, solvent substitutions, and other compound analogues, were identified in commercial antifingerprint liquid products. In the hydroxyl radical-based total oxidizable precursor assay, differential molar yields of products were observed with regard to varied PFASi carbon-chain lengths and terminal groups. The yields of perfluoroalkyl carboxylic acids (PFCAs) from 8:2 PTrMeOSi conversion were the highest (92 ± 9%, n = 3), with the C ( n - 1) perfluoroheptanoic acid (PFHpA, 49 ± 11%, n = 3) as the dominating product. Distinct conversion of 8:2 PTrMeOSi in the simulated solar exposure experiments found that C ( n) perfluorooctanoic acid (PFOA, 0.6 ± 0.04 ‰, n = 3) was predominant, and 8:2 fluorotelomer carboxylic acid (8:2 FTCA, 0.59 ± 0.08‰, n = 3), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA, 0.09 ± 0.00‰, n = 3) intermediates were also observed. To our knowledge, this is the first report regarding the occurrence and degradation potential of several fluoroalkylsilane substances as PFCA precursors.

Distribution and Fluxes of Perfluoroalkyl and Polyfluoroalkyl Substances in the Middle Reaches of the Yellow River (Weinan-Zhengzhou Section)

Surface water samples were collected in the middle reaches of the Yellow River (Weinan-Zhengzhou section) and all 28 perfluoroalkyl and polyfluoroalkyl substance (PFAS) levels were measured using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results show that the levels of PFASs in the water and particle phase are 18.4-56.9 ng·L-1 and 26.8-164 ng·g-1, respectively. Perfluorohexanoic acid (PFHxA) in the water and particle phases is the main pollutant, accounting for 27% and 16% of the total concentrations, respectively, and 3H-perfluoro-3-[(3-methoxy-propoxy)-propanoate] acid (ADONA) and chlorinated polyfluorinated ethersulfonic acids (6:2 and 8:2 Cl-PFESA) were detected in the particle phase, indicating that the use of PFAS alternatives gradually increases. The lgKd of PFASs between the water and particle phase ranges from 2.95±0.553 (PFPeA) to 3.85±0.237 (8:2 FTUCA)and the adsorption of fluorotelomer carboxylic acids (FTCAs) and fluorotelomer unsaturated carboxylic acids (FTUCAs) on particulate matter increases with increasing of carbon chain length. Perfluoroalkane sulfonic acids (PFSAs) are more easily adsorbed by particulate matter than perfluoroalkyl carboxylic acids (PFCAs). The fluxes of PFASs in the Weinan-Zhengzhou section of the Yellow River show a decrease at first and then increase, indicating that this section receives pollution inputs from the upstream and tributaries. In addition, the results show that the fluxes of PFASs in the water phase are greater than those in the particle phase.

Biotransformation and bioconcentration of 6:2 and 8:2 polyfluoroalkyl phosphate diesters in common carp (Cyprinus carpio): Underestimated ecological risks

Polyfluoroalkyl phosphates esters (PAPs) are widely used in a variety of commercial products, and have been detected in many aquatic organisms. In this study, common carps (Cyprinus carpio) were administered with 6:2 and 8:2 diPAP in water to investigate their bio-accumulation and transformation in fish. Several degradation products, including fluorotelomer unsaturated carboxylic acids (6:2 and 8:2 FTUCA), 5:3 and 7:3 fluorotelomer carboxylic acids (5:3 and 7:3 FTCA), perfluoroalkyl carboxylates (PFCAs) were identified in the carp liver. In addition, several phase-II metabolites, such as glutathione- and glucuronide-conjugated compounds were detected in the carp bile. 8:2 diPAP displayed lower accumulation potential than 6:2 diPAP probably due to its relatively large molecular size. However, 8:2 diPAP experienced more extensive transformation (transformation rate 6.78–14.6 mol%) and produced more phase I metabolites than 6:2 diPAP (0.49–0.66 mol%). The in vitro incubation with the liver S9 fraction confirmed that biotransformation of 6:2 and 8:2 diPAP took place in the carp liver. Further analyses of enzyme activities indicated that acid phosphatase (ACP) could be involved in mediating phase I while glutathione S-transferase (GST) involved in phase II metabolism of 6:2 and 8:2 diPAP in carp.

Per- and Polyfluoroalkyl Substances (PFASs) in Indoor Air and Dust from Homes and Various Microenvironments in China: Implications for Human Exposure.

A newly developed solid-phase extraction cartridge composed of mixed sorbents was optimized for collection of both neutral and ionizable per- and polyfluoroalkyl substances (PFASs) in indoor air. Eighty-one indoor air samples and 29 indoor dust samples were collected from rooms of homes and hotels, textile shops, and cinemas in Tianjin, China. Fluorotelomer alcohols (FTOHs) were the predominant PFASs found in air (250-82 300 pg/m3) and hotel dust (24.8-678 ng/g). Polyfluoroalkyl phosphoric acid diesters were found at lower levels of nd-125 pg/m3 in air and 0.32-183 ng/g in dust. Perfluoroalkyl carboxylic acids (PFCAs) were dominant ionizable PFASs in air samples (121-20 600 pg/m3) with C4-C7 PFCAs contributing to 54% ± 17% of the profiles, suggesting an ongoing shift to short-chain PFASs. Long-chain PFCAs (C > 7) were strongly correlated and the intermediate metabolite of FTOHs, fluorotelomer unsaturated carboxylic acids, occurred in all the air samples at concentrations up to 413 pg/m3, suggesting the transformation of precursors such as FTOHs in indoor environment. Daily intake of ∑PFASs via air inhalation and dust ingestion was estimated at 1.04-14.1 ng/kg bw/d and 0.10-8.17 ng/kg bw/d, respectively, demonstrating that inhalation of air with fine suspended particles was a more important direct exposure pathway than dust ingestion for PFASs to adults.

Review of the fate and transformation of per- and polyfluoroalkyl substances (PFASs) in landfills.

A critical review of existing publications is presented i) to summarize the occurrence of various classes of per- and polyfluoroalkyl substances (PFASs) and their sources in landfills, ii) to identify temporal and geographical trends of PFASs in landfills; iii) to delineate the factors affecting PFASs in landfills; and iv) to identify research gaps and future research directions. Studies have shown that perfluoroalkyl acids (PFAAs) are routinely detected in landfill leachate, with short chain (C4-C7) PFAAs being most abundant, possibly indicating their greater mobility, and reflecting the industrial shift towards shorter-chain compounds. Despite its restricted use, perfluorooctanoic acid (PFOA) remains one of the most abundant PFAAs in landfill leachates. Recent studies have also documented the presence of PFAA-precursors (e.g., saturated and unsaturated fluorotelomer carboxylic acids) in landfill leachates at concentrations comparable to, or higher than, the most frequently detected PFAAs. Landfill ambient air also contains elevated concentrations of PFASs, primarily semi-volatile precursors (e.g., fluorotelomer alcohols) compared to upwind control sites, suggesting that landfills are potential sources of atmospheric PFASs. The fate of PFASs inside landfills is controlled by a combination of biological and abiotic processes, with biodegradation releasing most of the PFASs from landfilled waste to leachate. Biodegradation in simulated anaerobic reactors has been found to be closely related to the methanogenic phase. The methane-yielding stage also results in higher pH (>7) of leachates, correlated with higher mobility of PFAAs. Little information exists regarding PFAA-precursors in landfills. To avoid significant underestimation of the total PFAS released from landfills, PFAA-precursors and their degradation products should be determined in future studies. Owing to the semi-volatile nature of some precursor compounds and their degradation products, future studies also need to include landfill gas to clarify degradation pathways and the overall fate of PFASs.

Impact of the Biodegradation of 6:2 Fluorotelomer Alcohol on the Bacterial Community Structure of Surface Sediment

Fluorotelomer alcohol (6:2 FTOH) is a polyfluoalkyl substance that has been widely used in industry and consumer products in recent years, causing potential harm to the environment. However, currently the impact of 6:2 FTOH and its degradation products on microbial communities in sediment is unclear. The purpose of this study is to explore the impact of the biodegradation of 6:2 FTOH on bacterial community structures in surface sediment based on gene analysis. Surface sediment and river water were collected from Hai river, Tianjin, and a microcosm experiment was performed in the laboratory. The concentration of 6:2 FTOH and its degradation products were analyzed by liquid chromatograph-mass spectrometry/mass spectrometry (LC-MS/MS). The bacterial community structure was analyzed by denaturing gradient gel electrophoresis and high-throughput sequencing. The results showed that 6:2 FTOH could be degraded by microorganisms (half-life was less than 3 d), producing transient products such as 6:2 fluorotelomer carboxylic acid (FTCA) and 6:2 fluorotelomer unsaturated carboxylic acid (FTUCA) and stable products such as 5:2 fluorotelomer (FT) ketone, 5:2 fluorotelomer alcohol (sFTOH), perfluorohexanoic acid(PFHxA), perfluoro-n-pentanoic acid (PFPeA), perfluorobutanoic acid (PFBA) and 5:3 polyfluorinated acid. At different stages of 6:2 FTOH degradation, a change of bacteria and the predominant population became somewhat different. Based on the experimental results for 100 d, at the Phylum level, the biodegradation of 6:2 FTOH greatly increases the abundance of Chloroflexi (+24.8%) and decreases the abundance of Proteobacteria (-17.8%) and Firmicutes (-15.9%). At the Class level, due to the biodegradation of 6:2 FTOH, bacteria with notable increases included Anaerolineae (+19.6%) and δ-Proteobacteria (+4.3%), while bacteria with notable decreases included ε-Proteobacteria (-20.0%), Clostridia (-10.1%), Bacilli (-5.8%) and γ-Proteobacteria (- 4.2%). At the Genus level, due to the biodegradation of 6:2 FTOH, bacteria with notable increases included Anaerolineaceae_(uncultured) (+19.1%) and Thioalkalispira (+13.3%), while bacteria with notable decreases included Vibrio (-14.1%), Sulfurimonas (-13.2%), Bacillus (-5.1%), Sulfurovum (-4.2%) and Fusibacter (-4.1%). These results are helpful for predicting the response of bacteria to the contamination of polyfluoalkyl substances and isolating the bacteria capable of the biodegradation of polyfluoalkyl substances.

Aerobic biodegradation of 2 fluorotelomer sulfonamide-based aqueous film-forming foam components produces perfluoroalkyl carboxylates.

The biodegradation of 2 common fluorotelomer surfactants used in aqueous film forming foams (AFFFs), 6:2 fluorotelomer sulfonamide alkylamine (FTAA) and 6:2 fluorotelomer sulfonamide alkylbetaine (FTAB), was investigated over 109 d with aerobic wastewater-treatment plant (WWTP) sludge. Results show that biodegradation of 6:2 FTAA and 6:2 FTAB produces 6:2 fluorotelomer alcohol (FTOH), 6:2 fluorotelomer carboxylic acid (FTCA), 6:2 fluorotelomer unsaturated carboxylic acid (FTUCA), 5:3 FTCA, and short-chain perfluoroalkyl carboxylates (PFCAs). Additional degradation products included 6:2 fluorotelomer sulfonamide (FTSAm), which was a major degradation product in the presence of either active or sterilized sludge, whereas 6:2 fluorotelomer sulfonate (FTSA) production was measured with sterilized sludge only. Six additional degradation products were tentatively identified by quadrupole time-of-flight mass spectrometry (qTOF-MS) and attributed to N-dealkylation and oxidation of 6:2 FTAA. Environ Toxicol Chem 2017;36:2012-2021. © 2017 SETAC.

HPLC-MS/MS methods for the determination of 52 perfluoroalkyl and polyfluoroalkyl substances in aqueous samples.

Two quantitative methods using high-performance liquid chromatography (HPLC) combined with triple quadrupole tandem mass spectrometry (MS/MS) were developed to determine perfluoroalkyl and polyfluoroalkyl substances (PFASs) in aqueous samples. The first HPLC-MS/MS method was applied to 47 PFASs of 12 different substance classes with acidic characteristics such as perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs), as well as precursor substances and biotransformation intermediates (e.g., unsaturated fluorotelomer carboxylic acids). In addition, 25 13C-, 18O-, and 2H-labeled PFASs were used as internal standards in this method. The second HPLC-MS/MS method was applied to fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamidoethanols as these compounds have physicochemical properties different from those of the previous ones. Accuracy between 82% and 110% and a standard deviation in the range from 2% to 22% depending on the substances were determined during the evaluation of repeatability and precision. The method quantification limit after solid-phase extraction ranged from 0.3 to 199ng/L depending on the analyte and matrix. The HPLC-MS/MS methods developed were suitable for the determination of PFASs in aqueous samples (e.g., wastewater treatment plant effluents or influents after solid-phase extraction). These methods will be helpful in monitoring campaigns to evaluate the relevance of precursor substances as indirect sources of perfluorinated substances in the environment. In one exemplary application in an industrial wastewater treatment plant, FTOHs were found to be the major substance class in the influent; in particular, 6:2-FTOH was the predominant compound in the industrial samples and accounted for 74% of the total PFAS concentration. The increase in the concentration of the transformation products of FTOHs in the corresponding effluent, such as fluorotelomer carboxylic acids, unsaturated fluorotelomer carboxylic acids, n:3 polyfluorinated saturated carboxylic acids (n indicates the number of nonfluorinated carbon atoms), and PFCAs, indicated biotransformation of FTOHs or their derivatives during wastewater treatment. However, only 33mol% of the total amount of PFASs present in the influent was quantified in the corresponding effluent. Graphical abstract Method development of an HPLC-MS/MS multi-method for the determination of PFASs in aqueos samples.

Transformation of polyfluorinated compounds in natural waters by advanced oxidation processes.

The presence of perfluorocarboxylic acids (PFCAs) in source and finished drinking waters is a concern with studies showing bioaccumulation and adverse toxicological effects in wildlife and potentially humans. Per/Polyfluoroalkyl substances (PFAS) such as fluorotelomer alcohols have been identified as precursors for PFCAs in biological pathways. In this study, we investigated the fate of 6:2 and 8:2 homologues of the fluorotelomer unsaturated carboxylic acids (FTUCAs) during advanced oxidation process (AOPs). Results showed 6:2 FTUCA and 8:2 FTUCA transformed into 6-C PFCA (PFHxA) and 8-C PFCA (PFOA) respectively with very little other PFCA formation for all AOPs. The degradation of 6:2 FTUCA and 8:2 FTUCA was greater in the GW compared to SW for the ozone processes but similar for UV/H2O2. The formation of n-C PFCA followed O3>O3/H2O2 at same dose and UV/H2O2 had much lower formation at the doses tested. Non-targeted analysis with the LC-MS-qTOF indicated the production of other PFCAs which contribute to the total mass balance, although no intermediate product was discovered indicating a rapid and direct transformation from the FTUCAs to the PFCAs and/or significant volatilization of intermediates. With the use of AOPs essential to water reuse treatment schemes, this work raises concerns over the risk of potential formation of PFCAs in the treatment and their adverse health effects in finished drinking water.

Aerobic Biotransformation of Fluorotelomer Thioether Amido Sulfonate (Lodyne) in AFFF-Amended Microcosms

The aerobic biotransformation pathways of 4:2, 6:2, and 8:2 fluorotelomer thioether amido sulfonate (FtTAoS) were characterized by determining the fate of the compounds in soil and medium microcosms amended with an aqueous film-forming foam (AFFF) solution. The biotransformation of FtTAoS occurred in live microcosms over approximately 40 days and produced 4:2, 6:2, and 8:2 fluorotelomer sulfonate (FtS), 6:2 fluorotelomer unsaturated carboxylic acid (FtUCA), 5:3 fluorotelomer carboxylic acid (FtCA), and C4 to C8 perfluorinated carboxylic acids (PFCAs). Two biotransformation products corresponding to singly and doubly oxygenated forms of 6:2 FtTAoS were also identified through high resolution mass spectrometry (MS) analysis and liquid chromatography tandem-MS. An oxidative assay was used to indirectly quantify the total concentration of polyfluorinated compounds and check the mass balance. The assay produced near complete mass recovery of FtTAoS after biotransformation, with 10% (mol/mol) of the amended FtTAoS accounted for in FtS, FtCA, and PFCA products. The transformation rates of identified products appear to be slow relative to FtTAoS, indicating that some intermediates may persist in the environment. This study confirms some of the sources of FtS and PFCAs in groundwater and soil at AFFF-impacted sites and suggests that fluorinated intermediates that are not routinely measured during the biotransformation of PFASs may accumulate.

World-Wide Indoor Exposure to Polyfluoroalkyl Phosphate Esters (PAPs) and other PFASs in Household Dust.

Human exposure to perfluorooctanoic acid (PFOA) and other per- and polyfluoroalkyl substances (PFASs) is ongoing and in some cases increasing, despite efforts made to reduce emissions. The role of precursor compounds such as polyfluorinated phosphate esters (PAPs) has received increasing attention, but there are knowledge gaps regarding their occurrence and impact on human exposure. In this study, mono-, di-, and triPAPs, perfluorinated alkyl acids (PFAAs), saturated, and unsaturated fluorotelomer carboxylic acids (FTCA/FTUCAs), perfluoroalkane sulfonamides, and sulfonamidethanols (FOSA/FOSEs), and one fluorotelomer sulfonic acid (FTSA)) were compared in household dust samples from Canada, the Faroe Islands, Sweden, Greece, Spain, Nepal, Japan, and Australia. Mono-, di-, and triPAPs, including several diPAP homologues, were frequently detected in dust from all countries, revealing an ubiquitous spread in private households from diverse geographic areas, with significant differences between countries. The median levels of monoPAPs and diPAPs ranged from 3.7 ng/g to 1 023 ng/g and 3.6 ng/g to 692 ng/g, respectively, with the lowest levels found in Nepal and the highest in Japan. The levels of PAPs exceeded those of the other PFAS classes. These findings reveal the importance of PAPs as a source of PFAS exposure worldwide.

Visible light-induced decomposition of a fluorotelomer unsaturated carboxylic acid in water with a combination of tungsten trioxide and persulfate

Photochemical decomposition of a fluorotelomer unsaturated carboxylic acid, C3F7CFCHCOOH (1), in the presence of WO3 and an electron acceptor (S2O82- or H2O2) in water under visible-light irradiation was investigated. Under an O2 atmosphere, 1 was not decomposed either by TiO2 (P25) or WO3 alone. A combination of WO3 and H2O2 also resulted in almost no decomposition of 1. In contrast, irradiation in the presence of a combination of WO3 and S2O82- (potassium salt) efficiently decomposed 1 to F−, CO2, C3F7COOH, and C2F5COOH. The decomposition of 1 was affected by the counter cation of S2O82-: the decomposition extent was higher with K2S2O8 than with (NH4)2S2O8. The decomposition of 1 was further enhanced when the reaction in the presence of WO3 and K2S2O8 was carried out under an argon atmosphere. Under O2, the amount of H2O2 formed in the reaction solution was an order of magnitude higher than the amount formed under argon. This fact suggests that the decrease in the decomposition of 1 under O2 can be ascribed to the formation of H2O2, which consumed S2O82- and SO4-.

Covalent Binding of Fluorotelomer Unsaturated Aldehydes (FTUALs) and Carboxylic Acids (FTUCAs) to Proteins

Fluorotelomer unsaturated carboxylic acids and aldehydes (FTUCAs and FTUALs) are intermediate compounds that form from the biotransformation of fluorotelomer-based compounds. Previous evidence that FTUCAs and FTUALs bind to biological nucleophiles has indicated that protein binding might give rise to toxicity resulting from protein function disruption. The current study assesses the reactivity of FTUALs and FTUCAs by probing the covalent interactions of FTUALs and FTUCAs with proteins present in rat liver microsomes and bovine blood plasma. The FTUALs exhibited significant levels of protein covalent binding, with binding levels ranging from 20.1 (±2.8)% to 71.3 (±19.5)% in microsomes and 24.0 (±1.5)% to 82.5 (±14.0)% in blood plasma. By contrast, the FTUCAs did not exhibit any apparent covalent binding. Bovine serum albumin (BSA) was extracted and isolated from the plasma after incubation of 8:2 FTUAL (5-100 μM). Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the stoichiometry of 8:2 FTUAL covalently bound to BSA; three measurable FTUAL adducts were formed with BSA. To compare the percent binding results from the FTUAL microsome incubation experiments, 8:2 FTOH was incubated in microsomes to determine the protein binding associated with the biotransformation of 8:2 FTOH. Results from this study showed that the biotransformation of 8:2 FTOH yielded 26.1 (±3.0)% binding, and was statistically similar to the percent binding associated with 8:2 FTUAL exposure (p > 0.05), indicating that the binding of 8:2 FTUAL to proteins might be a primary fate in the biotransformation of 8:2 FTOH.

Polyfluorinated and Perfluorinated Chemicals in Precipitation and Runoff from Cities Across Eastern and Central China

Twenty-three polychlorinated and perfluorinated compounds (PFCs) were investigated in water phase and particulate matters of 19 precipitation samples (18 snow samples and 1 rain sample) from different cities across eastern and central China collected in February 2010. The PFCs in samples of 9e precipitation events during more than half a year at 1 site in Tianjin and 6 successive samples during 1 precipitation event were measured to elucidate the change of PFC in precipitation. In addition, PFCs in 3 runoffs at different kinds of sites in Tianjin were compared with those in the corresponding precipitation. The results showed that the particulate matters separated from the precipitation contained undetectable PFCs. The total PFC concentration ranged between 4.7 and 152ngL(-1) in water phase of the precipitation samples, with perfluorooctanoic acid (PFOA) being detected at all of the sampling sites and the dominant PFC at most of the sampling sites. Some potential precursors of environmentally concerned PFCs and their degradation intermediates were measured simultaneously, among which 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), 8:2 FTUCA, and ×(3, 4, 5, 7):3 acid [F(CF(2))xCH(2)CH(2)COOH] were measured for the first time in Chinese precipitations; however, their concentrations were all lower than the limits of detection except that 6:2 FTUCA and 8:2 FTUCA could be detected in 3 and 8 precipitation samples, respectively. No clear seasonal variation in PFC concentrations in precipitation was observed during half a year; however, a relatively greater average concentration of total PFCs was observed during winter and summer compared with spring. The concentration of individual PFCs showed an obvious descending trend in the successive samples of the precipitation event. PFOA and perfluorononanoic acid in runoffs collected from different sites showed the following similar pattern-gas station>highway>university campus-whereas the other detected PFCs had no concurrent trend.