Analysis of hexafluoropropylene oxide-dimer acid (HFPO-DA) by Liquid Chromatography-Mass Spectrometry (LC-MS): Review of Current Approaches and Environmental Levels

Tissue-specific distribution and fatty acid content of PFAS in the northern Bohai Sea fish: Risk-benefit assessment of legacy PFAS and emerging alternatives

This study aimed to examine the distribution of poly- and perfluoroalkyl substances (PFAS) in 15 marine fish species from the northern Bohai Sea, investigate their sources of contamination, and evaluate the benefits-risks associated with the concurrent consumption of fish fatty acids and PFAS. The ∑PFAS concentrations in fish ranged from 9.38 to 262.92 ng·g-1 (dry weight). The highest PFAS levels were found in the viscera and gills, while the lowest levels were found in the muscles. Industrial effluents and sewage treatment plant discharges were the primary sources of PFAS contamination. The individual PFAS concentrations in fish were insignificantly correlated with their trophic levels (p > 0.05). However, the concentrations of hexafluoropropylene oxide dimer acid (HFPO-DA) or long-chain PFAS (C > 8) significantly increased with fish size (e.g., total length, weight) and lipid content (p < 0.001). The benefit-risk analysis suggests that HPFO-DA poses a higher health risk than perfluorooctanoic acid (PFOA) in fish (p < 0.05). Long-term consumption of contaminated fish may significantly increase human serum PFOA concentration and kidney cancer risk (p < 0.05). Daily consumption of 5 g (wet weight) muscle from Ditrema temmincki and Konosirus punctatus is recommended to meet the requirements for fatty acid supplementation without posing health risks.

Evaluation of per- and polyfluoroalkyl substances (PFAS) toxic effects on the acute inflammatory response in the medicinal leech Hirudoverbana

Per- and polyfluoroalkyl (PFAS) substances are a large group of chemicals with elevated water and oil-resistance properties, widely implicated in various applicative fields. Due to the extensive use and high resistance to degradative factors, these compounds pose a significant risk of environmental spreading, bioaccumulating also in living organisms. In this context, despite many researches have been performed to demonstrate "legacy" PFAS harmfulness, only few data are still available about all the emerging fluorinated molecules, industrially introduced to replace the previous ones. For this reason, we proposed the medicinal leech Hirudo verbana as consolidated invertebrate model to assess the effects of four different PFAS (HFPO-DA, PFMoBa, PFOA and PFMOPrA) following freshwater dispersion. Morphological, immunohistochemical and molecular analyses demonstrate that, despite all the compounds basically induce an acute inflammatory and oxidative stress response, a different cellular and molecular response has been observed. Whereas for PFOA and PFMOPrA an increase in the tested concentration leads to a corresponding rise in the immune response, HFPO-DA and PFMoBa trigger an entirely opposite effect. Indeed, the significant recruitment of both granulocytes and macrophage like cells, typically involved in the removal of non-self, is inhibited with increasing concentrations of these compounds. The data collected revealed a different sensitivity of the leech immune system following PFAS exposure, requiring to deepen the current knowledge on the potential toxicity of these compounds.

Novel insights into the mechanisms of bioaccumulation and tissue-specific distribution of hexafluoropropylene oxide homologues, novel PFOA alternatives, in zebrafish (Danio rerio)

Hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide tetramer acid (HFPO-TeA) are two novel alternatives of perfluorooctanoic acid (PFOA). However, their toxicokinetics and accumulation mechanisms in fish are still unknown. This study provides the first line of in vivo uptake and depuration kinetic, bioaccumulation mechanism and tissue-specific distribution for HFPO-TA and HFPO-TeA, upon a 28-day water exposure and a 14-day depuration in zebrafish (Danio rerio). HFPO-TeA and HFPO-TA could quickly accumulate in zebrafish, and the highest concentrations of HFPO-TeA (15.4 ± 1.6 nmol/g ww), HFPO-TA (4.95 ± 0.19 nmol/g ww) and PFOA (0.47 ± 0.03 nmol/g ww) were consistently present in the blood, which was followed by liver, kidney, intestine, gill, gonad and brain, while the lowest were observed in the muscle (1.01 ± 0.11, 0.16 ± 0.02, and 0.01 ± 0.001 nmol/g ww, respectively), indicating both higher accumulation potentials of both HFPO homologs than their predecessor PFOA. The tissue protein content, rather than lipid content, played an enhancing role in the enrichment of three target chemicals, exhibiting a significant positive correlation (r = 0.735, p = 0.038 for HFPO-TeA; r = 0.770, p = 0.026 for HFPO-TA and r = 0.942, p = 0.001 for PFOA) between the tissue bioconcentration factor (BCF) and the protein contents in corresponding tissues. This phenomenon was validated by the equilibrium dialysis experiment, molecular docking analysis and molecular dynamics simulation, which consistently indicated that the binding affinities of serum and liver proteins were greatest with HFPO-TeA, followed by HFPO-TA and least with PFOA. These results suggested that the binding of the target chemicals to specific proteins determined their tissue-specific accumulation potentials. Nontarget screening by high resolution mass spectrometry (HRMS) did not identify suspicious degradation products for HFPO-TA, implying the strong persistence of HFPO-TA in fish.

Electrocatalytic oxidation of hexafluoropropylene oxide homologues in water using a boron-doped diamond electrode

Hexafluoropropylene oxide (GenX) is a kind of substitute to PFOA, which has been listed in the Stockholm Convention. In this study, GenX was attempted to be degraded using a boron-doped diamond anode in the electrochemical oxidation system. The effects of operating parameters, including current density (0.5-10 mA/cm2), initial pH (3.0-11.49), initial concentration of GenX (20-150 mg/L), electrode distances (0.5-2 cm), electrolyte types (Na2SO4, NaCl, NaNO3 and NaHCO3) and Na2SO4 electrolyte concentration (40-80 mm), on GenX were studied. GenX can almost completely be degraded under the optimal operating parameters after 180 min of electrolysis. Free radical quenching experiments were carried out to investigate the effects of hydroxyl radicals and sulphate radicals on the degradation of GenX. The degradation intermediates were identified based on the ultra-high performance liquid chromatography equipped with a tandem mass spectrometer, and the degradation mechanisms were also proposed. Finally, the toxicities of GenX and its degradation products were evaluated using the QSAR models. The novelty is that the degradation mechanisms of the high concentration GenX (100 mg/L) were elucidated based on the free radical quenching experiments and the intermediates detected, when the degradation ratio reached 100%.

Analytical methods for determining environmental contaminants of concern in water and wastewater

Control and prevention of environmental pollution have emerged as paramount global concerns. Anthropogenic activities, such as industrial discharges, agricultural runoff, and improper waste disposal, introduce a wide range of contaminants into various ecosystems. These pollutants encompass organic and inorganic compounds, particulates, microorganisms, and disinfection by-products, posing severe threats to human health, ecosystems, and the environment. Effective monitoring methods are indispensable for assessing environmental quality, identifying pollution sources, and implementing remedial measures. This paper suggests that the development and utilization of highly advanced analytical tools are both essential for the analysis of contaminants in water samples, presenting a foundational hypothesis for the review. This paper comprehensively reviews the development and utilization of highly advanced analytical tools which is mandatory for the analysis of contaminants in water samples. Depending on the specific pollutants being studied, the choice of analytical methods widely varies. It also reveals insights into the diverse applications and effectiveness of these methods in assessing water quality and contaminant levels. By emphasizing the critical role of the reviewed monitoring methods, this review seeks to deepen the understanding of pollution challenges and inspire innovative monitoring solutions that contribute to a cleaner and more sustainable global environment.•Urgent global concerns: control and prevention of pollution from diverse sources.•Varied contaminants, diverse methods: comprehensive review of analytical tools.•Inspiring a sustainable future: innovative monitoring for a cleaner environment.

Resistivity detection of perfluoroalkyl substances with fluorous polyaniline in an electrical lateral flow sensor

Perfluoroalkyl substances (PFAS), known as "forever chemicals," are a growing concern in the sphere of human and environmental health. In response, rapid, reproducible, and inexpensive methods for PFAS detection in the environment and home water supplies are needed. We have developed a simple and inexpensive perfluoroalkyl acid detection method based on an electrically read lateral flow assay (e-LFA). Our method employs a fluorous surfactant formulation with undoped polyaniline (F-PANI) fabricated to create test lines for the lateral flow assay. In perfluoroalkyl acid sensing studies, an increase in conductivity of the F-PANI film is caused by acidification and doping of PANI. A conductivity enhancement by 104-fold can be produced by this method, and we demonstrate a limit of detection for perfluorooctanoic acid (PFOA) of 400 ppt and perfluorobutanoic acid of 200 ppt. This method for PFOA detection can be expanded for wide-scale environmental and at-home water testing.

Microbial defluorination of TFA, PFOA, and HFPO-DA by a native microbial consortium under anoxic conditions

In this study, the biodegradability of trifluoroacetate (TFA), perfluorooctanoic acid (PFOA), and perfluoro-2-methyl-3-oxahexanoic acid (HFPO-DA) by a native microbial community was evaluated over a 10-month incubation period. The observed microbial defluorination ratios and removal efficiency were 3.46 ( ± 2.73) % and 8.03 ( ± 3.03) %, 8.44 ( ± 1.88) % and 13.52 ( ± 4.96) %, 3.02 ( ± 0.62) % and 5.45 ( ± 2.99) % for TFA, PFOA and HFPO-DA, respectively. The biodegradation intermediate products, TFA and pentafluoropropionic acid (PFA), of PFOA and HFPO-DA were detected in their biodegradation treatment groups. Furthermore, the concentrations of the PFOA metabolites, perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA), in the aqueous solutions after incubation were quantified to be 0.21 and 4.14 µg/L. TFA, PFOA and HFPO-DA significantly reduced the microbial diversity and changed the structure of the community. The co-occurrence network analysis showed that low abundance species, such as Flexilinea flocculi, Bacteriovorax stolpii, and g_Sphingomonas, are positively correlated with the generation of fluoride ion, implying their potential collaborative functions contributing to the observed biodefluorination. The findings in this study can provide insights for the biodegradation of perfluoroalkyl carboxylic acids and their emerging alternatives by indigenous microorganisms in the environment.

Prenatal exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) disrupts the maternal gut microbiome and fecal metabolome homeostasis

Initially considered a "safe" substitute for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been extensively used in the production of fluoropolymers for several years, leading to its environmental ubiquity and subsequent discovery of its significant bio-accumulative properties and toxicological effects. However, the specific impact of HFPO-TA on females, particularly those who are pregnant, remains unclear. In the present study, pregnant mice were exposed to 0.63 mg/kg/day HFPO-TA from gestational day (GD) 2 to GD 18. We then determined the potential effects of exposure on gut microbiota and fecal metabolites at GD 12 (mid-pregnancy) and GD 18 (late pregnancy). Our results revealed that, in addition to liver damage, HFPO-TA exposure during the specified window altered the structure and function of cecal gut microbiota. Notably, these changes showed the opposite trends at GD 12 and GD 18. Specifically, at GD 12, HFPO-TA exposure primarily resulted in the down-regulation of relative abundances within genera from the Bacteroidetes and Proteobacteria phyla, as well as associated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. With extended exposure time, the down-regulated genera within Proteobacteria became significantly up-regulated, accompanied by corresponding up-regulation of human disease- and inflammation-associated pathways, suggesting that HFPO-TA exposure can induce intestinal inflammation and elevate the risk of infection during late pregnancy. Pearson correlation analysis revealed that disturbances in the gut microbiota were accompanied by abnormal fecal metabolite. Additionally, alterations in hormones related to the steroid hormone biosynthesis pathway at both sacrifice time indicated that HFPO-TA exposure might change the steroid hormone level of pregnant mice, but need further study. In conclusion, this study provides new insights into the mechanisms underlying HFPO-TA-induced adverse effects and increases awareness of potential persistent health risks to pregnant females.

Comparison of high-resolution mass spectrometry acquisition methods for the simultaneous quantification and identification of per- and polyfluoroalkyl substances (PFAS)

Simultaneous identification and quantification of per- and polyfluoroalkyl substances (PFAS) were evaluated for three quadrupole time-of-flight mass spectrometry (QTOF) acquisition methods. The acquisition methods investigated were MS-Only, all ion fragmentation (All-Ions), and automated tandem mass spectrometry (Auto-MS/MS). Target analytes were the 25 PFAS of US EPA Method 533 and the acquisition methods were evaluated by analyte response, limit of quantification (LOQ), accuracy, precision, and target-suspect screening identification limit (IL). PFAS LOQs were consistent across acquisition methods, with individual PFAS LOQs within an order of magnitude. The mean and range for MS-Only, All-Ions, and Auto-MS/MS are 1.3 (0.34-5.1), 2.1 (0.49-5.1), and 1.5 (0.20-5.1) pg on column. For fast data processing and tentative identification with lower confidence, MS-Only is recommended; however, this can lead to false-positives. Where high-confidence identification, structural characterisation, and quantification are desired, Auto-MS/MS is recommended; however, cycle time should be considered where many compounds are anticipated to be present. For comprehensive screening workflows and sample archiving, All-Ions is recommended, facilitating both quantification and retrospective analysis. This study validated HRMS acquisition approaches for quantification (based upon precursor data) and exploration of identification workflows for a range of PFAS compounds.

A targeted and non-targeted discovery screening approach for poly-and per-fluoroalkyl substances in model environmental biota samples

A comprehensive analytical approach for targeted and non-targeted discovery screening of per- and polyfluoroalkyl substances (PFAS) was developed and applied to model complex environmental biotic samples. Samples were extracted by formic acid-acetonitrile solution and cleaned up and fractionated by SPE (WAX). Target PFAS quantification was performed by ultra-high performance liquid chromatography interfaced with a triple quadrupole mass spectrometer (UPLC-QqQ-MS/MS). Non-targeted analysis (NTA) PFAS screening was performed with UPLC coupled with a quadrupole-Exactive orbitrap high resolution mass spectrometer (UPLC-Q-Exactive-HRMS). An iterative exclusion (IE) approach was applied to data acquisition for NTA suspect screening to increase the potential for unknown PFAS discovery with MS/MS. A complex workflow in Compound Discoverer was set up to automate data processing of the PFAS suspects search. New mass lists and MS/MS databases, which included a large number of PFAS, were set up and introduced into the search for high-throughput structure identification using HRMS techniques. The integrated targeted-NTA method successfully analyzed for legacy and alternative PFAS in model environmental biota samples, namely polar bear liver and bird egg samples. Targeted analysis provided unequivocal identification of well known/established PFAS (mainly perfluoroalkyl acids) with quantification at very low levels. The NTA suspect screening was able to determine a broader range of PFAS. The data analysis method offered high-confidence annotations for PFAS despite lacking available authentic standards. Overall, the analytical coverage of PFAS was greater and elucidated other PFAS present in these model apex predators.

Association of adverse fetal outcomes with placental inflammation after oral gestational exposure to hexafluoropropylene oxide dimer acid (GenX) in Sprague-Dawley rats

Hexafluoropropylene oxide dimer acid (HFPO-DA), known as "GenX" for its trade name, is gradually taking the place of Perfluorooctanoic acid (PFOA). However, there is a poor understanding of the developmental effects of GenX. This study aims to explore whether GenX produces adverse effects on offspring development in Sprague-Dawley (SD) rats and the underlying mechanisms. Pregnant rats were orally administered with GenX (0, 1, 10 and 100 mg/kg/day) from gestational 0.5-19.5 days. Experimental data showed that the exposure to GenX resulted in increased rats' gestational weight gain, whereas both body weight and body length of their fetuses born naturally were significantly reduced. This could contribute to the developmental delays of fetal body weight, body length and tail length from postnatal 1-21 days. Histopathological evaluation of placenta indicated that GenX exposure led to neutrophil infiltration in decidual zone and congestion in labyrinth zone. Moreover, placental proteomics showed changes at the expression levels of the inflammation-related proteins in the Rap1 signaling pathway. In conclusion, gestational exposure to GenX induced fetal intrauterine and extrauterine development retardation in SD rats. Placental inflammation may play a key role in this process through the Rap1 signaling pathway.

Antibiotic induced restructuring of the gut microbiota does not affect oral uptake and accumulation of perfluorooctane sulfonic acid (PFOS) in rats

Perfluorooctane sulfonic acid (PFOS) is a manmade legacy compound belonging to the group of persistent per- and polyfluorinated substances (PFAS). While many adverse health effects of PFOS have been identified, knowledge about its effect on the intestinal microbiota is scarce. The microbial community inhabiting the gut of mammals plays an important role in health, for instance by affecting the uptake, excretion, and bioavailability of some xenobiotic toxicants. Here, we investigated (i) the effect of vancomycin-mediated microbiota modulation on the uptake of PFOS in adult Sprague-Dawley rats, and (ii) the effects of PFOS exposure on the rat microbiota composition. Four groups of twelve rats were exposed daily for 7 days with either 3 mg/kg PFOS plus 8 mg/kg vancomycin, only PFOS, only vancomycin, or a corn oil control. Vancomycin-induced modulation of the gut microbiota composition did not affect uptake of branched and linear PFOS over a period of 7 days, measured in serum samples. 16S rRNA amplicon sequencing of faecal and intestinal samples revealed that vancomycin treatment lowered microbial alpha-diversity, while PFOS increased the microbial diversity in vancomycin-treated as well as in non-antibiotic treated animals, possibly because an observed decrease in the Enterobacteriaceae abundance allows other microbial species to propagate. Colonic short-chain fatty acids were significantly lower in vancomycin-treated animals but remained unaffected by PFOS. Our results suggest that PFOS exposure may disturb the intestinal microbiota, but that antibiotic-induced modulation of the intestinal ecosystem does not affect systemic uptake of PFOS in rats.

Taking a look at the surface: μ-XRF mapping and fluorine K-edge μ-XANES spectroscopy of organofluorinated compounds in environmental samples and consumer products

For the first time, μ-X-ray fluorescence (μ-XRF) mapping combined with fluorine K-edge μ-X-ray absorption near-edge structure (μ-XANES) spectroscopy was applied to depict per- and polyfluoroalkyl substance (PFAS) contamination and inorganic fluoride in sample concentrations down to 100 μg kg^-1 fluoride. To demonstrate the matrix tolerance of the method, several PFAS contaminated soil and sludge samples as well as selected consumer product samples (textiles, food contact paper and permanent baking sheets) were investigated. μ-XRF mapping allows for a unique element-specific visualization at the sample surface and enables localization of fluorine containing compounds to a depth of 1 μm. Manually selected fluorine rich spots were subsequently analyzed via fluorine K-edge μ-XANES spectroscopy. To support spectral interpretation with respect to inorganic and organic chemical distribution and compound class determination, linear combination (LC) fitting was applied to all recorded μ-XANES spectra. Complementarily, solvent extracts of all samples were target-analyzed via LC-MS/MS spectrometry. The detected PFAS sum values range from 20 to 1136 μg kg^-1 dry weight (dw). All environmentally exposed samples revealed a higher concentration of PFAS with a chain length > C₈ (e.g. 580 μg kg^-1 dw PFOS for Soil1), whereas the consumer product samples showed a more uniform distribution with regard to chain lengths from C₄ to C₈. Independent of quantified PFAS amounts via target analysis, μ-XRF mapping combined with μ-XANES spectroscopy was successfully applied to detect both point-specific concentration maxima and evenly distributed surface coatings of fluorinated organic contaminants in the corresponding samples.

Legacy and Emerging Per- and Polyfluoroalkyl Substances in a Subtropical Marine Food Web: Suspect Screening, Isomer Profile, and Identification of Analytical Interference

The ban/elimination of legacy per- and polyfluoroalkyl substances (PFASs) has led to a dramatic increase in the production and use of various emerging PFASs over the past decade. However, trophodynamics of many emerging PFASs in aquatic food webs remain poorly understood. In this study, samples of seawaters and marine organisms including 15 fish species, 21 crustacean species, and two cetacean species were collected from the northern South China Sea (SCS) to investigate the trophic biomagnification potential of legacy and emerging PFASs. Bis(trifluoromethylsulfonyl)imide was found in seawater via suspect screening (concentration up to 1.50 ng/L) but not in the biota, indicating its negligible bioaccumulation potential. A chlorinated perfluorooctane sulfonate (PFOS) analytical interfering compound was identified with a predicted formula of C14H23O5SCl6- (most abundant at m/z = 514.9373). Significant trophic magnification was observed for 22 PFASs, and the trophic magnification factors of cis- and trans-perfluoroethylcyclohexane sulfonate isomers (1.92 and 2.25, respectively) were reported for the first time. Perfluorohexanoic acid was trophic-magnified, possibly attributed to the PFAS precursor degradation. The hazard index of PFOS was close to 1, implying a potential human health risk via dietary exposure to PFASs in seafood on the premise of continuous PFAS discharge to the SCS.

Simultaneous determination of multiple perfluoroalkyl and polyfluoroalkyl substances in aquatic products by ultra-performance liquid chromatography-tandem mass spectrometry with automated solid-phase extraction

Diet is an important route of human exposure to perfluoroalkyl and polyfluoroalkyl substances (PFASs), and aquatic products are the main dietary source of PFASs. This study aimed to establish a method for the analysis of 52 PFASs in typical aquatic products, such as crucian carp, large yellow croaker, shrimp, and clam, by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) after automated solid phase extraction (SPE). After optimization of the conditions of SPE, the recovery and precision of the method is within an acceptable range. The intra-day and inter-day average recoveries of spiked samples ranged from 66.5% to 122.3% and 64.5%-128.0% for crucian carp, large yellow croaker, shrimp, and clam, with intra-day and inter-day relative standard deviation (RSD) of 0.78%-11.4%, and 2.54%-24.2%. The ranges of method detection limits (MDLs) and quantification limits (MQLs) of PFASs were 0.003-0.60 ng/g and 0.005-2.0 ng/g, respectively. The accuracy of the method was also verified by standard reference material (SRM), and the measured values of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were in the allowable range. The method was applied to analyze aquatic products from the local supermarket. The concentrations of ∑PFASs ranged from 13.9 ng/g ww to 75.5 ng/g ww. PFOS was the dominant pollutant, accounting for 79.6% of ∑PFASs. The branch-chain isomers, perfluoro-3-methylheptane sulfonate (P3MHpS) and perfluoro-6-methylheptane sulfonate (P6MHpS) accounted for one-quarter of PFOS. Long-chain perfluoro carboxylic acids (PFCAs) were also detected in most samples. The estimated daily intake of PFOS was over the recommended tolerable intake by several organizations such as the Minnesota Department of Health (MDH), the New Jersey Drinking Water Quality Institute (NJDWQI), and the European Food Safety Authority (EFSA). PFOS would have posed health risks to consumers through dietary exposure.

Warming Affects Bioconcentration and Bioaccumulation of Per- and Polyfluoroalkyl Substances by Pelagic and Benthic Organisms in a Water-Sediment System

Warming and exposure to emerging global pollutants, such as per- and polyfluoroalkyl substances (PFAS), are significant stressors in the aquatic ecosystem. However, little is known about the warming effect on the bioaccumulation of PFAS in aquatic organisms. In this study, the pelagic organisms Daphnia magna and zebrafish, and the benthic organism Chironomus plumosus were exposed to 13 PFAS in a sediment-water system with a known amount of each PFAS at different temperatures (16, 20, and 24 °C). The results showed that the steady-state body burden (C_b-ss) of PFAS in pelagic organisms increased with increasing temperatures, mainly attributed to increased water concentrations. The uptake rate constant (k_u) and elimination rate constant (k_e) in pelagic organisms increased with increasing temperature. In contrast, warming did not significantly change or even mitigate C_b-ss of PFAS in the benthic organism Chironomus plumosus, except for PFPeA and PFHpA, which was consistent with declined sediment concentrations. The mitigation could be explained by the decreased bioaccumulation factor due to a more significant percent increase in k_e than k_u, especially for long-chain PFAS. This study suggests that the warming effect on the PFAS concentration varies among different media, which should be considered for their ecological risk assessment under climate change.

Legacy and emerging poly- and perfluoroalkyl substances in wastewater treatment plant and receiving water: abundance, removal, and potential ecological risk

Poly- and perfluoroalkyl substances (PFASs) are toxic persistent organic pollutants and bioaccumulative chemicals, which affect the environment and ecology. PFASs in the wastewater treatment plant (WWTP) and receiving river downstream were investigated. Fourteen out of eighteen PFASs were detected, ranging from 197 to 0.14 ng L^-1. The main pollutants were 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoro-propoxy) propanoic acid (HFPO-DA), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA). The concentration of HFPO-DA (181 ng L^-1) was the highest in influent, which indicated the use and emission of PFASs in the sewage collection region of WWTP changed from legacy to emerging ones. However, PFOS from catering wastewater as the main source was dominant PFASs in the reclaimed water. Biological treatment could be effective in the removal of PFASs, especially for HFPO-DA. HFPO-DA could directly bind to cytochrome P450 and bring potential ecotoxicity to the surrounding environment, and the ecological risk of degradation products should be under consideration. Coagulation might result in PFASs release from sludge. More attention should be paid to sewage treatment process decision of WWTP for the control of PFASs.

Targeted Per- and Polyfluoroalkyl substances (PFAS) assessments for high throughput screening: Analytical and testing considerations to inform a PFAS stock quality evaluation framework

Per- and polyfluoroalkyl substances (PFAS) represent a large chemical class lacking hazard, toxicokinetic, and exposure information. To accelerate PFAS hazard evaluation, new approach methodologies (NAMs) comprised of in vitro high-throughput toxicity screening, toxicokinetic data, and computational modeling are being employed in read across strategies to evaluate the larger PFAS landscape. A critical consideration to ensure robust evaluations is a parallel assessment of the quality of the screening stock solutions, where dimethyl sulfoxide (DMSO) is often the diluent of choice. Challenged by the lack of commercially available reference standards for many of the selected PFAS and reliance on mass spectrometry approaches for such an evaluation, we developed a high-throughput framework to evaluate the quality of screening stocks for 205 PFAS selected for these NAM efforts. Using mass spectrometry coupled with either liquid or gas chromatography, a quality scoring system was developed that incorporated observations during mass spectral examination to provide a simple pass or fail notation. Informational flags were used to further describe findings regarding parent analyte presence through accurate mass identification, evidence of contaminants and/or degradation, or further describe characteristics such as isomer presence. Across the PFAS-DMSO stocks tested, 148 unique PFAS received passing quality scores to allow for further in vitro testing whereas 57 received a failing score primarily due to detection issues or confounding effects of DMSO. Principle component analysis indicated vapor pressure and Henry's Law Constant as top indicators for a failed quality score for those analyzed by gas chromatography. Three PFAS in the hexafluoropropylene oxide family failed due to degradation in DMSO. As the PFAS evaluated spanned over 20 different structural categories, additional commentary describes analytical observations across specific groups related to PFAS stock composition, detection, stability, and methodologic considerations that will be useful for informing future analytical assessment and downstream HTS efforts. The high-throughput stock quality scoring workflow presented holds value as a tool to evaluate chemical presence and quality efficiently and for informing data inclusion in PFAS or other NAM screening efforts.

Comparison of developmental toxicity induced by PFOA, HFPO-DA, and HFPO-TA in zebrafish embryos

Hexafluoropropylene oxide dimer acids (HFPO-DA) and hexafluoropropylene oxide trimer acids (HFPO-TA) are alternatives to perfluorooctanoic acid (PFOA). However, little information on the comparison of their toxicities is available. Here, zebrafish embryos were exposed to PFOA, HFPO-DA, and HFPO-TA with exposure concentrations of 5 and 500 μg/L. Behavioral abnormal, enzyme activities and gene expression profiles in zebrafish embryos were determined. Results showed that exposure to PFOA and its alternatives increased heart rates and inhibited locomotor activity of zebrafish embryos. Further, their exposures changed the enzyme activities (acetylcholinesterase and oxidative stress-related enzymes), ATP content, and expressions of genes related to hypothalamic-pituitary-thyroid (HPT) axis, apoptosis, and lipid metabolism. Comparison analyses found that PFOA, HFPO-TA, and HFPO-DA exposures induced different effects on the embryonic development of zebrafish, which indicates the different modes of action. The HFPO-DA exposure induced specific effects on the disorder of lipid metabolism, HPT axis, and neurodevelopment. The HFPO-TA exposure also induced different effects from the PFOA exposure, which focused on lipid metabolism. The current data shows that the HFPO-DA and HFPO-TA might not be safe alternatives to PFOA. This study provides a new understanding of the biological hazards of PFOA alternatives in aquatic organisms, which can guide their usage.

Investigation of the Interaction between Human Serum Albumin and Branched Short-Chain Perfluoroalkyl Compounds

The current trend dealing with the production of per- and polyfluoroalkyl substances (PFASs) involves the shifting toward branched short-chain fluorinated compounds known as new-generation PFASs. A key aspect to be clarified, to address the adverse health effects associated with the exposure to PFASs, is their binding mode to human serum albumin (hSA), the most abundant protein in plasma. In this study, we investigated the interaction between hSA and two representative branched short-chain PFASs, namely, HPFO-DA and C6O4. In-solution studies revealed that both compounds bind hSA with affinities and stoichiometries lower than that of the legacy long-chain perfluoroalkyl compound PFOA. Competition experiments using hSA-binding drugs with known site-selectivity revealed that both HPFO-DA and C6O4 bound to pockets located in subdomain IIIA. The crystal structure of hSA in complex with HPFO-DA unveiled the presence of two binding sites. The characterization and direct comparison of hSA interactions with new-generation PFASs may be key elements for the understanding of the toxicological impact of these compounds.

Comparison of sub-lethal metabolic perturbations of select legacy and novel perfluorinated alkyl substances (PFAS) in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of pollutants of concern due to their ubiquitous presence, persistence, and toxicity in aquatic environments. Legacy PFAS pollutants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have been more widely studied in aquatic environments. However, replacement PFAS, such as ammonium perfluoro (2-methyl-3-oxahexanoate; GenX) are increasingly being detected with little known information surrounding their toxicity. Here, Daphnia magna, a model organism for freshwater ecotoxicology was used to compare the acute sub-lethal toxicity of PFOS, PFOA, GenX, and PFAS mixtures. Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the targeted polar metabolic profile extracted from single Daphnia was quantified to investigate perturbations in the exposure groups versus the unexposed organisms. Multivariate statistical analyses demonstrated significant non-monotonic separation in PFOA, GenX, and PFAS mixture exposures. Sub-lethal exposure to concentrations of PFOS did not lead to significant separation in multivariate analyses. Univariate statistics and pathway analyses were used to elucidate the mode of action of PFAS exposure. Exposure to all individual PFAS led to significant perturbations in many amino acids including cysteine, histidine, tryptophan, glycine, and serine. These perturbations are consistent with biochemical pathway disruptions in the pantothenate and Coenzyme A (CoA) biosynthesis, thiamine metabolism, histidine metabolism, and aminoacyl-tRNA biosynthesis pathways. Overall, the collected metabolomic data is consistent with disruptions in energy metabolism and protein synthesis as the primary mode of action of sub-lethal PFAS exposure. Secondary modes of action among individual pollutant exposures demonstrated that the structural properties (carboxylic acid vs. sulfonic acid group) may play a role in the metabolic perturbations observed. Sub-lethal exposure to PFAS mixtures highlighted a mixed response when compared to the individual pollutants (PFOS, PFOA, and GenX). Overall, this study emphasizes the niche capability of environmental metabolomics to differentiate secondary modes of action from metabolic perturbations in both single pollutant and pollutant mixtures within the same chemical class.

Development and validation of a high resolving power absolute quantitative per- and polyfluoroalkyl substances method incorporating Skyline data processing

RATIONALE

The ability to perform absolute quantitation and non-targeted analysis on a single mass spectrometry instrument would be advantageous to many researchers studying per- and polyfluoroalkyl substances (PFAS). High-resolution accurate mass (HRAM) instrumentation (typically deployed for non-targeted work) carries several advantages over traditional triple quadrupole workflows when performing absolute quantitation. Processing this data using a vendor-neutral software would promote collaboration for these environmental studies.

METHODS

LC-MS (Orbitrap Exploris 240) was used for absolute quantitation of 45 PFAS using precursor (MS1) peak areas for quantitation, whereas isotope pattern matching and fragmentation (MS2) pattern matching were used for qualitative identification. In addition, a fluorinated chromatographic column achieved superior separation compared to the typical C18 columns typically used in PFAS analyses. This method was validated across eight different chemical classes using recommended guidelines found in EPA Method 537.1 and Skyline data processing software.

RESULTS

The validated limits of all 45 compounds, as well as metrics or accuracy and reproducibility, are reported. Most compounds achieved limits of quantitation in the range of 2-50 ng/L. Four newly released Chemours-specific compounds (PEPA, PFO3OA, PFO4DA, and PFO5DoA) were also validated. Aspects of data analysis specific to high resolving power absolute quantitation are reviewed as are the details of processing these data via Skyline.

CONCLUSIONS

This method shows the feasibility of performing reproducible absolute quantitation of PFAS on an HRAM platform and does so using an open-source vendor-neutral data processing software to facilitate sharing of data across labs and institutions.

Per- and Polyfluoroalkyl Substances (PFAS) in Street Sweepings

One hundred and seventeen street sweeping samples were collected and analyzed for per- and polyfluoroalkyl substances (PFAS). Fifty-six samples were collected in one city (Gainesville, Florida) allowing for an in-depth city-wide characterization. Street sweepings from five other urban areas, (Orlando, n = 15; Key West, n = 15; Pensacola, n = 12; Tampa, n = 13; and Daytona Beach, n = 6) were analyzed to provide a city-to-city comparison of PFAS. Within our analytical workflow, 37 PFAS were quantified across all samples, while the maximum number of PFAS quantified at one site was 26. Of those PFAS quantified in Gainesville, 60% were perfluoroalkyl acids (PFAAs) and 33% were precursors to PFAA. Among the PFAAs, short-chain perfluoroalkyl carboxylic acids (PFCAs) were the dominant class representing 26% of the total PFAS by concentration. In the comparison across different urban cities, the dominant compound by concentration and frequency of detection varied; however, perfluorooctanoic acid (PFOA) and linear perfluorooctanesulfonic acid (PFOS_lin) were the two PFAS that were detected the most frequently. This study documents the first-time detection of hexadecafluorosebacic acid and perfluoro-3,6,9-trioxaundecane-1,11-dioic acid within environmental samples.

Beyond the Tip of the Iceberg: Suspect Screening Reveals Point Source-Specific Patterns of Emerging and Novel Per- and Polyfluoroalkyl Substances in German and Chinese Rivers

Only a few dozens of the several thousand existing per- and polyfluoroalkyl substances (PFAS) are monitored using conventional target analysis. This study employed suspect screening to examine patterns of emerging and novel PFAS in German and Chinese river water affected by industrial point sources. In total, 86 PFAS were (tentatively) identified and grouped into 18 structure categories. Homologue patterns revealed distinct differences between fluoropolymer production sites of the two countries. In the Chinese Xiaoqing River Basin, the C₈ homologue was the most prevalent compound of the emerging series of chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs) and perfluoroalkylether carboxylic acids (PFECAs). In contrast, C₆ and shorter homologues were dominant in the German Alz River. This indicates that the phaseout of long-chain compounds in Europe and their ongoing production in Asian countries also apply to unregulated emerging PFAS classes. Additional characteristics to differentiate the point sources were the peak area ratio of perfluorobutane sulfonic acid (PFBS) versus the emerging compound hydro-substituted PFBS (H-PFBS) as well as the occurrence of byproducts of the sulfonated tetrafluoroethylene-based polymer Nafion. The large number of identified unregulated PFAS underlines the importance of a grouping approach on a regulatory level, whereas the revealed contamination patterns can be used to estimate, prioritize, and minimize contributions of specific sources.

GenX in water: Interactions and self-assembly

2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoate, a.k.a. "GenX", is a surfactant introduced as a safer alternative to replace perfluorooctanoate (PFOA) in the manufacturing of fluorinated polymers, however, GenX is shown to cause adverse health effects similar to, or even worse than, those of the legacy PFOA. With an overarching goal to understand the behavior of GenX molecules in aqueous media, we report here on GenX micelle formation and structure in aqueous solutions, on the basis of results obtained from a combination of experimental techniques such as surface tension, fluorescence, viscosity, and small-angle neutron scattering (SANS), and molecular dynamics (MD) simulations. To our best knowledge, this is the first report on GenX micelles. The critical micelle concentration (CMC) of GenX ammonium salt in water is 175 mM. GenX forms small micelles with association number 6-8 and 10 Å radius. GenX molecules prefer to align along the micelle surface, and the ether oxygen of GenX has very little interaction with and exposure to water. Information on the surfactant and interfacial properties of GenX is crucial, since such properties are manifestations of interactions between GenX molecules and between GenX and water molecules and, in turn, the amphiphilic character of GenX dictates its fate and transport in the aqueous environment, its interactions with various biomolecules, and its binding to adsorbent materials.

Methods for the analysis of endocrine disrupting chemicals in selected environmental matrixes

Endocrine disrupting chemicals (EDCs) are heterogenous in structure, chemical and physical properties, and their capacity to partition into various environmental matrixes. In many cases, these chemicals can disrupt the endocrine systems of vertebrate and invertebrate organisms when present at very low concentrations. Therefore, sensitive and varied analytical methods are required to detect these compounds in the environment. This review summarizes the analytical methods and instruments that are most used to monitor for EDCs in selected environmental matrixes. Only those matrixes for which there is a clear link between exposures and endocrine effects are included in this review. Also discussed are emerging methods for sample preparation and advanced analytical instruments that provide greater selectivity and sensitivity.

Is HFPO-DA (GenX) a suitable substitute for PFOA? A comprehensive degradation comparison of PFOA and GenX via electrooxidation

Due to the potential hazard of perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (HFPO-DA, GenX) has become a typical alternative since 2009. However, GenX has recently been reported to have equal or even greater toxicity and bioaccumulation than PFOA. Considering the suitability of alternatives, it is quite essential to study and compare the degradation degree between PFOA and GenX in water. Therefore, in the present study, a comprehensive degradation comparison between them via electrooxidation with a titanium suboxide membrane anode was conducted. The degradation rate decreased throughout for PFOA, while it first increased and then decreased for GenX when the permeate flux increased from 17.3 L to 100.3 L m^-2·h^-1. The different responses of PFOA and GenX to flux might be attributed to their different solubilities. In addition, the higher k_obs of PFOA demonstrated that it had a better degradability than GenX by 2.4-fold in a mixed solution. The fluorinated byproduct perfluoropropanoic acid (PFPrA) was detected as a GenX intermediate, suggesting that ether bridge splitting was needed for GenX electrooxidation. This study provides a reference for assessing the degradability of GenX and PFOA and indicates that it is worth reconsidering whether GenX is a suitable alternative for PFOA from the point of view of environmental protection.

Experimental insights into anodic oxidation of hexafluoropropylene oxide dimer acid (GenX) on boron-doped diamond anodes

GenX is the trade name of the ammonium salt of hexafluoropropylene oxide dimer acid (HFPO-DA) and is used as a replacement for the banned perfluorooctanoic acid (PFOA). However, recent studies have found GenX to be more toxic than PFOA. This work deals with the electrochemical degradation of HFPO-DA using boron-doped diamond anodes. For the first time, an experimental study was conducted to investigate the influence of sulfate concentration and other operating parameters on HFPO-DA degradation. Results demonstrated that sulfate radicals were ineffective in HFPO-DA degradation due to steric hindrance by -CF₃ branch. Direct electron transfer was found as the rate-determining step. By comparing degradation of HFPO-DA with that of PFOA, it was observed that the steric hindrance by -CF₃ branch in HFPO-DA decreased the rate of electron transfer from the carboxyl head group even though its defluorination rate was faster. Conclusively, a degradation pathway is proposed in which HFPO-DA mineralizes to CO₂ and F- via formation of three intermediates.

Thermal decomposition of heptafluoropropylene-oxide-dimer acid (GenX)

Incineration appears as a viable strategy in the disposal of the notorious perfluoroalkyl substances (PFASs) in a process that typically leads to fluorine mineralization. Central in the design of such operation is to comprehend the underlying chemical mechanisms that dictate thermal fragmentation of PFASs into smaller perfluorinated cuts and HF. Among notable short-chain PFASs entities is the heptafluoropropylene-oxide-dimer acid (HFPO-DA, C₅F₁₁C(O)OH), commercially known as GenX synthesized as a possible replacement of other PFASs compounds. However, reaction pathways that underpin the degradation of GenX at temperatures relevant to its decomposition in incinerators (i.e., cement kilns), remain unknown. Herein, we map out all plausible initial reactions that govern the thermal decomposition of GenX. Simultaneous elimination of HF and CO₂ appears as the kinetically most favored channel with an accessible activation enthalpy of ∼62.0 kcal/mol. Fission of the ether linkage in the 1,1,1,2,2,3,3-heptafluoro-3-[(1-fluoroethenyl)oxy] propane molecule (that forms after HF/CO₂ elimination) affords a wide array of C_nF_m cuts, most notably CF₂ at elevated temperatures. Constructed kinetic model plots temperature-dependent profiles of important species. It is predicted that GenX to commence decomposition around 700 K at a residence time of 2.0 s, a value that is generally applied in incinerators. Findings from the study call to further investigate interactions between the predicted major fluorine carriers (HF and CF₂) and other constituents encountered in relevant incineration mediums, most notably, calcium hydroxides and polymeric materials.

Comparison of bioconcentration and kinetics of GenX in tilapia Oreochromis mossambicus in fresh and brackish water

Contaminants of emerging concern (CEC) are a broad suite of chemicals commonly found in the environment, aquatic organisms and even drinking water. They include pharmaceuticals, personal care products, industrial chemicals and compounds added to consumer products. The CEC ammonium 2,3,3,3-tetrafluoro-2-heptafluoropropoxy propanoic acid, which is more commonly known as generic name GenX, is a replacement of common processing aid longer chain perfluorinated compounds (PFAS) due to a manufacturing shift in 2002 following the EPA stewardship program of 2015/16 in USA (USEPA, 2006). However, recently reported in North Carolina drinking water, GenX raising concerns about its accumulation in aquatic organisms, both wild and cultured, which could be a pathway for human exposure. To examine GenX accumulation and potential for human exposure, tilapia (Oreochromis mossambicus) fingerlings were dosed with GenX for up to 96 h in fresh (0 ppt) or brackish (16 ppt) water to determine uptake and bioconcentration. Depuration values were also determined after a 96 h exposure followed by 96 h without exposure. Bioconcentration was in decreasing order of plasma > liver > carcass > muscle, with higher distribution to liver followed by carcass and muscle. Muscle was found to have the highest half-life (1278 h) followed by carcass (532 h), plasma (106 h), and liver (152 h). The rate of uptake and depuration was positively affected by the salinity. As bioconcentration in all tissues increased with increasing salinity, this may raise concern for marine organisms and human exposure.

Development and validation of an LC-MS/MS method for the quantitation of 30 legacy and emerging per- and polyfluoroalkyl substances (PFASs) in human plasma, including HFPO-DA, DONA, and cC6O4

Per- and polyfluoroalkyl substances (PFASs) include persistent organic pollutants whose spread is still ubiquitous. Efforts to substitute substances of high concern with fluorinated alternatives, such as HFPO-DA (GenX), DONA (ADONA), and cC6O4, have been made. The aim of this work was to develop and validate an isotopic dilution liquid chromatography-tandem mass spectrometry (LC–MS/MS) method suitable to quantify 30 PFASs in human plasma. Analytes included legacy PFASs (PFOA, PFOS, and PFHxS), fluorinated alternatives (PFBA, PFBS, 6:2 FTSA, HFPO-DA, DONA, and cC6O4), and newly identified compounds (F-53B and PFECHS). The sample preparation was rapid and consisted of simple protein precipitation and centrifugation. Calibration standards and quality control solutions were prepared with a human pooled plasma containing relatively low background levels of the considered analytes. A complete validation was carried out: the lower limits of quantitation (LLOQs) ranged from 0.009 to 0.245 µg/L; suitable linearity (determination coefficients, R² 0.989–0.999), precision (2.0–19.5%, relative standard deviation), and accuracy (87.9–113.1% of theoretical) were obtained for considered concentration ranges. No significant variations of analyte responses were recorded under investigated storage conditions and during matrix effect tests. The external verification confirmed the accuracy of the method, although limited to 12 analytes. The method was also applied to 38 human plasma samples to confirm its applicability. The developed assay is suitable for large-scale analyses of a wide range of legacy and emerging PFASs in human plasma. To our knowledge, this is the first published method including cC6O4 for human biomonitoring.

Per/polyfluoroalkyl substances production, applications and environmental impacts

The per/polyfluoroalkyl substances (PFAS) are growing contaminants which are extremely difficult to get degraded naturally. PFAS have been produced for nearly a century using electrochemical flourination and more relomerization processes. High chemical resistance, hydrophobicity, lipophobicity, heat resistace, extremly low friction coefficient make this class of chemicals invaluable for many applications. These same properties useful unfortunately make them 'forever chemicals' once released into the envrironment. This review focuses on the production and applications of PFAs, determining the concentration of PFAs in environmental and biological matrices and their efficient degradation. Various methods of detection of PFAS have been developed but insitu methods of detction are still in the early stages of development. Current chemical and biological remediation technologies are expensive/not effective and thus new remediation technolgies must be developed. It is imperative to focus on methods for detection of the short chain PFAS with their projected increased use.

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

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

PFAS removal by ion exchange resins: A review

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

Toxic effects and mechanisms of PFOA and its substitute GenX on the photosynthesis of Chlorella pyrenoidosa

Perfluorooctanoic acid (PFOA) and its substitute GenX are toxic chemicals that are widespread in the aquatic environment. However, there is little information about their toxicity mechanisms to aquatic organisms. In this study, Chlorella pyrenoidosa (C. pyrenoidosa) was treated with two concentrations (100 ng L^-1 and 100 μg L^-1) of PFOA or GenX for 12 days. The results showed that these two concentrations of PFOA and GenX began to inhibit the growth of algae after 6 days of treatment, and the Chlorophyll content and photosynthetic activity of C. pyrenoidosa were also negatively affected by these two chemicals. The transcriptomic results indicated that most of the genes related to the photosynthetic metabolism of C. pyrenoidosa were down-regulated (in 100 ng L^-1 treatment groups) on the 12th day. Besides, GenX and PFOA showed similar effects on algae photosynthesis including physical damage and metabolic disorders. According to this study, GenX might not be an ideal substitute for PFOA, and more attention should be paid on the management of emerging perfluoroalkyl substances.

Legacy and Emerging Per- and Polyfluoroalkyl Substances: Analytical Techniques, Environmental Fate, and Health Effects

Due to their unique chemical properties, per- and polyfluoroalkyl substances (PFAS) have been used extensively as industrial surfactants and processing aids. While several types of PFAS have been voluntarily phased out by their manufacturers, these chemicals continue to be of ecological and public health concern due to their persistence in the environment and their presence in living organisms. Moreover, while the compounds referred to as “legacy” PFAS remain in the environment, alternative compounds have emerged as replacements for their legacy predecessors and are now detected in numerous matrices. In this review, we discuss the historical uses of PFAS, recent advances in analytical techniques for analysis of these compounds, and the fate of PFAS in the environment. In addition, we evaluate current biomonitoring studies of human exposure to legacy and emerging PFAS and examine the associations of PFAS exposure with human health impacts, including cancer- and non-cancer-related outcomes. Special focus is given to short-chain perfluoroalkyl acids (PFAAs) and ether-substituted, polyfluoroalkyl alternatives including hexafluoropropylene oxide dimer acid (HFPO-DA; tradename GenX), 4,8-dioxa-3H-perfluorononanoic acid (DONA), and 6:2 chlorinated polyfluoroethersulfonic acid (6:2 Cl-PFESA; tradename F-53B).

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.

Perfluoroalkyl substances in the Lingang hybrid constructed wetland, Tianjin, China: occurrence, distribution characteristics, and ecological risks

In this study, the occurrence, spatial distribution, sources, and ecological risks of perfluoroalkyl substances (PFASs) in the surface waters of the Lingang hybrid constructed wetland were systematically investigated. Twenty-three PFASs were analyzed from 7 representative sampling zones. The obtained results indicated that PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFBS, PFOS, and HFPO-DA were frequently detected; and PFBA, PFOA, and PFOS were the dominant PFASs with the relative abundances in ranges of 26.91 to 52.26%, 11.79 to 28.79%, and 0 to 31.98%, respectively. The total concentrations of 8 PFASs (Σ₈PFASs) ranged from 25.9 to 56.6 ng/L, and the highest concentration was observed in subsurface flow wetland. Moreover, HFPO-DA with high toxicity was detected in wetlands for the first time. Based on the principal component analysis-multiple linear regression (PCA-MLR) analysis, three sources and their contributions were fluoropolymer processing aids (67.6%), fluororesin coatings and metal plating (17.9%), and food packaging materials and atmospheric precipitation (14.5%), respectively. According to the risk quotients (RQs), the ecological risk of 8 PFASs was low to the aquatic organisms.

A liquid chromatography-high resolution mass spectrometry method for the determination of thirty-three per- and polyfluoroalkyl substances in animal liver

An analytical method for the quantification of thirty-three perfluoroalkyl and polyfluoroalkyl substances (PFASs) in animal liver was developed applying the isotopic dilution methodology with twenty-one labelled isotopologues of native compounds. The proposed protocol involved the determination of short and long aliphatic chain PFASs (C₄C₁₈) extracting liver with acetonitrile followed by two clean-up steps. The instrumental analysis was performed with liquid chromatography coupled to high-resolution mass spectrometry. The acquisition method combined full MS/dd-MS², t-SIM/dd-MS² and SIM experiments with variable resolution in order to maximize in one chromatographic run accuracy, sensitivity and selectivity. An eight-level validation study was performed evaluating linearity, trueness, precision, quantification and detection limits. Trueness was from 94 to 126% with intra-laboratory reproducibility lower than 20%. Limits of quantification were in the range 2-100 pg g^-1, except for 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoic acid, HFPO-DA (500 pg g^-1). The analysis of a certified reference material (IRMM-427) and participation in a proficiency test scheme (FAPAS - 0687) confirmed these satisfactory performances. Finally, the application of the developed procedure to detect PFASs in sixteen liver samples of farm animals revealed that chicken was the less contaminated species.