Per- and Polyfluoroalkyl Substances (PFAS) in PubChem: 7 Million and Growing

Determination of organic fluorinated compounds content in complex samples through combustion ion chromatography methods: a way to define a "Total Per- and Polyfluoroalkyl Substances (PFAS)" parameter?

Emerging contaminants are a growing concern for scientists and public authorities. The group of per-polyfluoroalkyl substances (PFAS), known as 'forever chemicals', in complex environmental liquid and solid matrices was analysed in this study. The development of global analytical methods based on combustion ion chromatography (CIC) is expected to provide accurate picture of the overall PFAS contamination level via the determination of extractable organic fluorine (EOF) and adsorbable organic fluorine (AOF). The obtained results may be put into perspective with other methods such as targeted analyses (LC-MS/MS). The impact of pH, the presence of dissolved organic carbon and suspended particles on AOF measurements were explored. The effectiveness of the washing step to remove adsorbed inorganic fluorine (IF) has been proven for samples containing up to 8 mgF.L-1. CIC-based methods showed good repeatability and reproducibility for the complex matrices studied. Environmental applications of these methods have been tested. AOF and EOF analyses could explain between 1 % and 23 % and 0.1 % to 2 % of total organic fluorine (TOF), respectively. The sum of PFAS compounds expressed as fluorine could explain from 0.2 % to 11 % and from 0.003 % to 5 % for AOF and EOF, respectively. These results also suggest that some fluorinated compounds are not adsorbed or extractable and/or lost by volatilisation during the application of AOF and EOF analytical procedure. These findings highlight that AOF and EOF are not entirely efficient as proxy to assess "total PFAS" for assessing environmental contamination by PFAS. However, these methods could still be applied to gain a better understanding of the sources and fate of PFAS in the environment.

The link between ancient microbial fluoride resistance mechanisms and bioengineering organofluorine degradation or synthesis

Fluorinated organic chemicals, such as per- and polyfluorinated alkyl substances (PFAS) and fluorinated pesticides, are both broadly useful and unusually long-lived. To combat problems related to the accumulation of these compounds, microbial PFAS and organofluorine degradation and biosynthesis of less-fluorinated replacement chemicals are under intense study. Both efforts are undermined by the substantial toxicity of fluoride, an anion that powerfully inhibits metabolism. Microorganisms have contended with environmental mineral fluoride over evolutionary time, evolving a suite of detoxification mechanisms. In this perspective, we synthesize emerging ideas on microbial defluorination/fluorination and fluoride resistance mechanisms and identify best approaches for bioengineering new approaches for degrading and making organofluorine compounds.

Use of Perfluorochemicals in Li-Air Batteries: A Critical Review

As lithium-ion (Li-ion) batteries approach their theoretical limits, alternative energy storage systems that can power technology with greater energy demands must be realized. Li-metal batteries, particularly Li-air batteries (LABs), are considered a promising energy storage candidate due to their inherent lightweight and energy-dense properties. Unfortunately, LAB practicality remains hindered by inadequate oxygen solubility and diffusion rates within the electrolyte, both which are fundamental for LAB operation. Due to exceptionally high oxygen solubilities, perfluorochemicals (PFCs) have been investigated as a promising solution to this issue. Although PFCs have been reported to enhance LAB performance and longevity when implemented within the cathodic regions of LABs in several studies, the influence of this class of compounds on other components of the battery (including the anode and the electrolyte) is also highly important. This paper reviews the use of PFCs in LABs to date and discusses the performance enhancements resulting from their implementation. We identify and discuss future prospects and emerging research directions for the use of PFCs into LAB design, in the effort toward realization of high-performing LAB technologies.

Machine learning-enhanced molecular network reveals global exposure to hundreds of unknown PFAS

Unknown forever chemicals like per- and polyfluoroalkyl substances (PFASs) are difficult to identify. Current platforms designed for metabolites and natural products cannot capture the diverse structural characteristics of PFAS. Here, we report an automatic PFAS identification platform (APP-ID) that screens for PFAS in environmental samples using an enhanced molecular network and identifies unknown PFAS structures using machine learning. Our networking algorithm, which enhances characteristic fragment matches, has lower false-positive rate (0.7%) than current algorithms (2.4 to 46%). Our support vector machine model identified unknown PFAS in test set with 58.3% accuracy, surpassing current software. Further, APP-ID detected 733 PFASs in real fluorochemical wastewater, 39 of which are previously unreported in environmental media. Retrospective screening of 126 PFASs against public data repository from 20 countries show PFAS substitutes are prevalent worldwide.

Characterization of nutrients and contaminants in fish sludge from Atlantic salmon (Salmo salar L.) production sites - A future resource

A total of 47 fish sludge samples from commercial land-based Atlantic salmon (Salmo salar) farms in Norway were assessed for their nutrient composition, presence of various legacy contaminants and a wide spectrum of contaminants of emerging concern, veterinary medicines as well as selected salmonid pathogenic bacteria and virus. The aim was to document the levels of desirable and undesirable components in fish sludge in relation to a potential future use of sludge as invertebrate feed. The samples had variable, but relatively high protein and fat contents, indicating a high load of undigested feed in some of the sludge samples. Fatty acid analysis showed the presence of essential omega-3 fatty acids. In terms of undesirable substances, 43% and 84% of the sludge samples contained levels of arsenic and cadmium, respectively, which exceeded the EU Maximum Levels established for complete animal feed. The concentrations of copper, zinc, iron and aluminum were highly variable in the sludge samples. The concentrations of dioxins, sum PCB6, and chlorinated pesticides were all below the Maximum Levels for animal feed. Of the 18 per- and polyfluoroalkyl substances (PFAS) only one compound (L-PFOS) was present at measurable levels. None of the samples had detectable levels of veterinary medicines, salmonid virus or bacteria. Performing a suspect and non-target screening of the sludge samples identified 18 compounds, including four pharmaceuticals, plastic-related products and the UV filter benzophenone, warranting further investigations. Overall, the results from this study show that fish sludge is a nutrient-rich resource; however, undesirable substances, originating from the feed or from treatment of sludge may be present.

Grouping strategies for assessing and managing persistent and mobile substances

Background

Persistent, mobile and toxic (PMT), or very persistent and very mobile (vPvM) substances are a wide class of chemicals that are recalcitrant to degradation, easily transported, and potentially harmful to humans and the environment. Due to their persistence and mobility, these substances are often widespread in the environment once emitted, particularly in water resources, causing increased challenges during water treatment processes. Some PMT/vPvM substances such as GenX and perfluorobutane sulfonic acid have been identified as substances of very high concern (SVHCs) under the European Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation. With hundreds to thousands of potential PMT/vPvM substances yet to be assessed and managed, effective and efficient approaches that avoid a case-by-case assessment and prevent regrettable substitution are necessary to achieve the European Union's zero-pollution goal for a non-toxic environment by 2050.

Main

Substance grouping has helped global regulation of some highly hazardous chemicals, e.g., through the Montreal Protocol and the Stockholm Convention. This article explores the potential of grouping strategies for identifying, assessing and managing PMT/vPvM substances. The aim is to facilitate early identification of lesser-known or new substances that potentially meet PMT/vPvM criteria, prompt additional testing, avoid regrettable use or substitution, and integrate into existing risk management strategies. Thus, this article provides an overview of PMT/vPvM substances and reviews the definition of PMT/vPvM criteria and various lists of PMT/vPvM substances available. It covers the current definition of groups, compares the use of substance grouping for hazard assessment and regulation, and discusses the advantages and disadvantages of grouping substances for regulation. The article then explores strategies for grouping PMT/vPvM substances, including read-across, structural similarity and commonly retained moieties, as well as the potential application of these strategies using cheminformatics to predict P, M and T properties for selected examples.

Conclusions

Effective substance grouping can accelerate the assessment and management of PMT/vPvM substances, especially for substances that lack information. Advances to read-across methods and cheminformatics tools are needed to support efficient and effective chemical management, preventing broad entry of hazardous chemicals into the global market and favouring safer and more sustainable alternatives.

Effects on food intake of Gammarus spp. after exposure to PFBA in very low concentrations

Per- and polyfluoroalkyl substances (PFAS) are a group of thousands of highly persistent anthropogenic chemicals widely used in many industries. Therefore, they are, ubiquitously present in various types of environments. Despite their omnipresence, ecotoxicological studies of most PFAS are scarce, and those available often assess the effects of long chain PFAS. In this study, we present the results of an exposure experiment in which wild aquatic amphipod Gammarus spp. was exposed to the short chain perfluorinated substance perfluorobutanoic acid (PFBA) at very low and environmentally relevant concentrations of 0, 10 and 100 ng/L. The exposure lasted for 12 days, and food intake and non-reproductive behavior were analyzed. Exposure to 10 and 100 ng/L PFBA resulted in a lower consumption of food during exposure but no effect on behavior was found.

Evolutionary obstacles and not C-F bond strength make PFAS persistent

The fate of organic matter in the environment, including anthropogenic chemicals, is largely predicated on the enzymatic capabilities of microorganisms. Microbes readily degrade, and thus recycle, most of the ~100,000 commercial chemicals used in modern society. Per- and polyfluorinated compounds (PFAS) are different. Many research papers posit that the general resistance of PFAS to microbial degradation is based in chemistry and that argument relates to the strength of the C-F bond. Here, I advance the opinion that the low biodegradability of PFAS is best formulated as a biological optimization problem, hence evolution. The framing of the problem is important. If it is framed around C-F bond strength, the major effort should focus on finding and engineering new C-F cleaving enzymes. The alternative, and preferred approach suggested here, is to focus on the directed evolution of biological systems containing known C-F cleaving systems. There are now reports of bacteria degrading and/or growing on multiply fluorinated arenes, alkenoic and alkanoic acids. The impediment to more efficient and widespread biodegradation in these systems is biological, not chemical. The rationale for this argument is made in the five sections below that follow the Introduction.

Rapid detection of per- and polyfluoroalkyl substances (PFAS) using paper spray-based mass spectrometry

Traditional PFAS analysis by mass spectrometry (MS) is time-consuming, as laborious sample preparation (e.g., extraction and desalting) is necessary. Herein, we report fast detection of PFAS by paper spray (PS)-based MS techniques, which employs a triangular-shaped filter paper for sample loading and ionization (≤ 3 min per sample). In this study, PS-MS was first used for direct PFAS analysis of drinking water, tap water, and wastewater. Interestingly, food package paper materials can be directly cut and examined with PS-MS for possible PFAS contamination. For samples containing salt matrices which would suppress PFAS ion signal, desalting paper spray mass spectrometry (DPS-MS), was shown to be capable of rapidly desalting, ionizing and detecting PFAS species such as per-fluorooctanoic acid (PFOA) and per-fluorosulphonic acid (PFOS). The retention of PFAS on paper substrate while salts being washed away by water is likely due to hydrophilic interaction between the PFAS polar head (e.g., carboxylic acid, sulfonic acid) with the polar filter paper cellulose surface. The DPS-MS method is highly sensitive (limits of detection:1.2-4.5 ppt) and can be applicable for directly analyzing soil extract and soil samples. These results suggest the high potential of PS-MS and the related DPS-MS technique in real-world environmental analysis of PFAS.

GenX analogs exposure induced greater hepatotoxicity than GenX mainly via activation of PPARα pathway while caused hepatomegaly in the absence of PPARα in female mice

Despite their use as substitutes for perfluorooctanoic acid, the potential toxicities of hexafluoropropylene oxide dimer acid (HFPO-DA, commercial name: GenX) and its analogs (PFDMOHxA, PFDMO2HpA, and PFDMO2OA) remain poorly understood. To assess the hepatotoxicity of these chemicals on females, each chemical was orally administered to female C57BL/6 mice at the dosage of 0.5 mg/kg/d for 28 d. The contribution of peroxisome proliferator-activated receptors (PPARα and γ) and other nuclear receptors involving in these toxic effects of GenX and its analogs were identified by employing two PPAR knockout mice (PPARα-/- and PPARγΔHep) in this study. Results showed that the hepatotoxicity of these chemicals increased in the order of GenX < PFDMOHxA < PFDMO2HpA < PFDMO2OA. The increases of relative liver weight and liver injury markers were significantly much lower in PPARα-/- mice than in PPARα+/+ mice after GenX analog exposure, while no significant differences were observed between PPARγΔHep and its corresponding wildtype groups (PPARγF/F mice), indicating that GenX analog induce hepatotoxicity mainly via PPARα instead of PPARγ. The PPARα-dependent complement pathways were inhibited in PFDMO2HpA and PFDMO2OA exposed PPARα+/+ mice, which might be responsible for the observed liver inflammation. In PPARα-/- mice, hepatomegaly and increased liver lipid content were observed in PFDMO2HpA and PFDMO2OA treated groups. The activated pregnane X receptor (PXR) and constitutive activated receptor (CAR) pathways in the liver of PPARα-/- mice, which were highlighted by bioinformatics analysis, provided a reasonable explanation for hepatomegaly in the absence of PPARα. Our results indicate that GenX analogs could induce more serious hepatotoxicity than GenX whether there is a PPARα receptor or not. These chemicals, especially PFDMO2HpA and PFDMO2OA, may not be appropriate PFOA alternatives.

Investigation of pH-dependent extraction methods for PFAS in (fluoropolymer-based) consumer products: A comparative study between targeted and sum parameter analysis

Here, we report a comparative study of different sum parameter analysis methods for the extraction of per- and polyfluoroalkyl substances (PFAS) from manufactured consumer products, which can be measured by combustion ion chromatography (CIC). Therefore, a hydrolysis-based extraction method was further developed, which accounts for the addition of hydrolyzable covalently bound polyfluoroalkylated side-chain polymers (SFPs) to the extractable organic fluorine portion of the mass balance proposed as "hydrolyzable organically bound fluorine" (HOF). To test this hypothesis, the method was applied to 39 different consumer products containing fluoropolymers or monomeric PFAS taken from four different categories: outdoor textiles, paper packaging, carpeting, and permanent baking sheets. We also evaluated the method's efficiency by extracting four synthesized fluorotelomer polyacrylate reference compounds. The total fluorine (TF) and extractable organically bound fluorine (EOF) values were measured through CIC using established protocols. The TF values ranged from sub-ppb to %-levels, depending on the compound class. All samples showed results for hydrolyzed organofluorine (HOF) between 0.03 and 76.3 μg/g, while most EOF values were lower ( Collapse

Key Words

• Combustion ion chromatography (CIC)
• Extractable organically bound fluorine (EOF)
• Hydrolytic extraction
• Per- and polyfluoroalkyl substances (PFAS) sum parameter
• Side-chain fluorinated polymers (SFPs)
• Solid-liquid extraction

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MESH Headings

• Fluorocarbon Polymers/analysis
• Fluorocarbons/analysis
• Chromatography, Liquid
• Fluorine/chemistry
• Tandem Mass Spectrometry
• Hydrogen-Ion Concentration

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Affiliation(s)

Philipp Roesch Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany.
Andrea Schinnen Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany
Maren Riedel Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany
Thomas Sommerfeld Federal Institute for Materials Research and Testing, Division 1.7 - Organic Trace and Food Analysis, Richard-Willstätter-Straße 11, 12489, Berlin, Germany
George Sawal German Environment Agency, Colditzstr. 34, 12099, Berlin, Germany
Nicole Bandow German Environment Agency, Colditzstr. 34, 12099, Berlin, Germany
Christian Vogel Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany
Ute Kalbe Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany
Franz-Georg Simon Federal Institute for Materials Research and Testing, Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany

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Occurrence and pattern of legacy and emerging per- and Poly-FluoroAlkyl substances (PFAS) in eggs of loggerhead turtle Caretta caretta from western Mediterranean

Per-and Poly-FluoroAlkyl Substances (PFAS) are a class of persistent, toxic, and mobile and chemicals both from industrial sources and from the use and disposal of Consumers products containing PFAS, whose concentration in marine food webs could pose a toxicological risk for biota and humans. In 2021, unhatched eggs were sampled from 41 loggerhead turtle Caretta caretta nests from the Italian shores of the Campania Region (Southern Italy). Whole eggs were analysed for the presence of 66 legacy and emerging PFAS with Liquid Chromatography coupled to Hybrid High Resolution Mass Spectrometry. A median Σ66 Per- and Poly-FluoroAlkyl Substances value of 3.34 ng/g egg fresh weight was found; perfluoroctane sulfonate (PFOS) represented the most contributing congener (47%), followed by perfluoro-n-undecanoic acid, perfluoro-n-tridecanoic acid, perfluoro-n-decanoic acid, perfluoro-n-decanoic acid, and perfluoro-n-tetradecanoic acid, respectively. Such compounds showed a log-norm distribution, suggesting found concentrations could represent the baseline levels in the considered sampling area. Emerging ChloroPolyFluoroPolyEthers Carboxylic Acids (ClPFECAs) were found in 20 out of 41 samples in the range 0.01-1.59 ng/g. Four samples had 20-100 fold higher concentration compared to that of other samples, suggesting the presence of hot spot areas possibly related to presence of fluoropolymer-based marine litter turtles may ingest. The analysis of two paired eggs/liver samples recovered from stranded animals revealed PFAS concentration in the same order of magnitude, supporting the role of vitellogenin in their selective transfer to yolk. Significant (P = 0.0155) Kendall negative correlation coefficient of -0.2705 among PFOS content in eggs and the recorded hatching success prompts for further investigation on associated exposure assessment and related eco-toxicity risk. This work reports for the first time PFAS presence in georeferenced loggerhead turtle eggs of the Mediterranean Sea and results represent a starting point to study PFAS time-trends in this vulnerable species.

Closing the Organofluorine Mass Balance in Marine Mammals Using Suspect Screening and Machine Learning-Based Quantification

High-resolution mass spectrometry (HRMS)-based suspect and nontarget screening has identified a growing number of novel per- and polyfluoroalkyl substances (PFASs) in the environment. However, without analytical standards, the fraction of overall PFAS exposure accounted for by these suspects remains ambiguous. Fortunately, recent developments in ionization efficiency (IE) prediction using machine learning offer the possibility to quantify suspects lacking analytical standards. In the present work, a gradient boosted tree-based model for predicting log IE in negative mode was trained and then validated using 33 PFAS standards. The root-mean-square errors were 0.79 (for the entire test set) and 0.29 (for the 7 PFASs in the test set) log IE units. Thereafter, the model was applied to samples of liver from pilot whales (n = 5; East Greenland) and white beaked dolphins (n = 5, West Greenland; n = 3, Sweden) which contained a significant fraction (up to 70%) of unidentified organofluorine and 35 unquantified suspect PFASs (confidence level 2-4). IE-based quantification reduced the fraction of unidentified extractable organofluorine to 0-27%, demonstrating the utility of the method for closing the fluorine mass balance in the absence of analytical standards.

PFΔScreen - an open-source tool for automated PFAS feature prioritization in non-target HRMS data

Per- and polyfluoroalkyl substances (PFAS) are a huge group of anthropogenic chemicals with unique properties that are used in countless products and applications. Due to the high stability of their C-F bonds, PFAS or their transformation products (TPs) are persistent in the environment, leading to ubiquitous detection in various samples worldwide. Since PFAS are industrial chemicals, the availability of authentic PFAS reference standards is limited, making non-target screening (NTS) approaches based on high-resolution mass spectrometry (HRMS) necessary for a more comprehensive characterization. NTS usually is a time-consuming process, since only a small fraction of the detected chemicals can be identified. Therefore, efficient prioritization of relevant HRMS signals is one of the most crucial steps. We developed PFΔScreen, a Python-based open-source tool with a simple graphical user interface (GUI) to perform efficient feature prioritization using several PFAS-specific techniques such as the highly promising MD/C-m/C approach, Kendrick mass defect analysis, diagnostic fragments (MS2), fragment mass differences (MS2), and suspect screening. Feature detection from vendor-independent MS raw data (mzML, data-dependent acquisition) is performed via pyOpenMS (or custom feature lists) with subsequent calculations for prioritization and identification of PFAS in both HPLC- and GC-HRMS data. The PFΔScreen workflow is presented on four PFAS-contaminated agricultural soil samples from south-western Germany. Over 15 classes of PFAS (more than 80 single compounds with several isomers) could be identified, including four novel classes, potentially TPs of the precursors fluorotelomer mercapto alkyl phosphates (FTMAPs). PFΔScreen can be used within the Python environment and is easily automatically installable and executable on Windows. Its source code is freely available on GitHub ( https://github.com/JonZwe/PFAScreen ).