A Matrix-Correction Approach to Estimate the Bioaccumulation Potential of Emerging PFASs

Bio-accumulation and health risk assessments of per- and polyfluoroalkyl substances in wheat grains

Per- and polyfluoroalkyl substances (PFASs) have been widely detected in various food, which has attracted worldwide concern. However, the factors influencing the transfer and bio-accumulation of PFASs from soils to wheat in normal farmland, is still ambiguous. We investigated the PFASs accumulation in agricultural soils and grains from 10 cites, China, and evaluated the health risks of PFASs via wheat consumption. Our results show that ∑PFASs in soils range from 0.34 μg/kg to 1.59 μg/kg with PFOA and PFOS dominating, whilst ∑PFASs in wheats range from 2.74 to 6.01 μg/kg with PFOA, PFBA and PFHxS dominating. The lower pH conditions and high total organic carbon (TOC) could result in the higher accumulation of PFASs in soils and subsequently in wheat grains, whilst the bioaccumulation factors of PFASs increase with increasing pH conditions but not with TOC. The estimated daily intake (EDI) values of PFBA, PFOA, and PFHxS are relatively high, but data supports that ingesting wheat grains does not result in any potential risk to the human beings. Our studies provided more information about PFASs accumulation in wheat grains, and help us understand the current potential risks of PFASs in food.

All-in-one strategy to construct bifunctional covalent triazine-based frameworks for simultaneous extraction of per- and polyfluoroalkyl substances and polychlorinated naphthalenes in foods

Per- and polyfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) are of growing concern due to their toxic effects on the environment and human health. There is an urgent need for strategies to monitor and analyze the coexistence of PFASs and PCNs, especially in food samples at trace levels, to ensure food safety. Herein, a novel β-cyclodextrin (β-CD) derived fluoro-functionalized covalent triazine-based frameworks named CD-F-CTF was firstly synthesized. This innovative framework effectively combines the porous nature of the covalent organic framework and the host-guest recognition property of β-CD enabling the simultaneous extraction of PFASs and PCNs. Under the optimal conditions, a simple and rapid method was developed to analyze PFASs and PCNs by solid-phase extraction (SPE) based simultaneous extraction and stepwise elution (SESE) strategy for the first time. When coupled with liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS), this method achieved impressive detection limits for PFASs (0.020 -0.023 ng/g) and PCNs (0.016 -0.075 ng/g). Furthermore, the excellent performance was validated in food samples with recoveries of 76.7-107 % (for PFASs) and 78.0-108 % (for PCNs). This work not only provides a simple and rapid technique for simultaneous monitoring of PFASs and PCNs in food and environmental samples, but also introduces a new idea for the designing novel adsorbents with multiple recognition sites.

Identifying priority PBT-like compounds from emerging PFAS by nontargeted analysis and machine learning models

As traditional per and polyfluoroalkyl substances (PFAS) are phased out, emerging PFAS are being developed and widely used. However, little is known about their properties, including persistence, bioaccumulation, and toxicity (PBT). Screening for emerging PFAS relies on available chemical inventory databases. Here, we compiled a database of emerging PFAS obtained from nontargeted analysis and assessed their PBT properties using machine learning models, including qualitative graph attention networks, Insubria PBT Index and quantitative EAS-E Suite, VEGA, and ProTox-II platforms. Totally 282 homologues (21.8% of emerging PFAS) were identified as PBT based on the combined qualitative and quantitative prediction, in which 140 homologues were detected in industrial and nonbiological/biological samples, belong to four categories, i.e. modifications of perfluoroalkyl carboxylic acids, perfluoroalkane sulfonamido substances, fluorotelomers and modifications of perfluoroalkyl sulfonic acids. Approximately 10.1% of prioritized emerging PFAS were matched to chemical vendors and 19.6% to patents. Aqueous film-forming foams and fluorochemical factories are the predominant sources for prioritized emerging PFAS. The database and screening results can update the assessment related to legislative bodies such as the US Toxic Substances Control Act and the Stockholm Convention. The combined qualitative and quantitative machine learning models can provide a methodological tool for prioritizing other emerging organic contaminants.

Screening for 26 per- and polyfluoroalkyl substances (PFAS) in German drinking waters with support of residents

The occurrence of per- and polyfluoroalkyl substances (PFAS) in water cycles poses a challenge to drinking water quality and safety. In order to counteract the large knowledge gap regarding PFAS in German drinking water, 89 drinking water samples from all over Germany were collected with the help of residents and were analyzed for 26 PFAS by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The 20 PFAS recently regulated by sum concentration (PFAS∑20), as well as six other PFAS, were quantified by targeted analysis. In all drinking water samples, PFAS∑20 was below the limit of 0.1 μg/L, but the sum concentrations ranged widely from below the limit of quantification up to 80.2 ng/L. The sum concentrations (PFAS∑4) of perfluorohexanesulfonate (PFHxS), perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorononanoate of 20 ng/L were exceeded in two samples. The most frequently detected individual substances were PFOS (in 52% of the samples), perfluorobutanesulfonate (52%), perfluorohexanoate (PFHxA) (44%), perfluoropentanoate (43%) and PFHxS (35%). The highest single concentrations were 23.5 ng/L for PFHxS, 15.3 ng/L for PFOS, and 10.1 ng/L for PFHxA. No regionally elevated concentrations were identified, but some highly urbanized areas showed elevated levels. Concentrations of substitution PFAS, including 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate and 2,2,3-trifluor-3-[1,1,2,2,3,3-hexafluor-3-(trifluormethoxy)propoxy]-propanoate (anion of ADONA), were very low compared to regulated PFAS. The most frequently detected PFAS were examined for co-occurrences, but no definite correlations could be found.

Accumulation and glucocorticoid signaling suppression by four emerging perfluoroethercarboxylic acids based on animal exposure and cell testing

Various perfluoroethercarboxylic acids (PFECA) have emerged as next-generation replacements of legacy per- and polyfluoroalkyl substances (PFAS). However, there is a paucity of information regarding their bioaccumulation ability and hazard characterization. Here, we explored the accumulation and hepatotoxicity of four PFECA compounds (HFPO-DA, HFPO-TA, PFO4DA, and PFO5DoDA) in comparison to perfluorooctanoic acid (PFOA) after chronic low-dose exposure in mice. Except for HFPO-DA, the levels of all tested PFAS in the liver exceeded that in serum. High molecular weight PFECA compounds (PFO5DoDA and HFPO-TA) showed stronger accumulation capacity and longer half-lives (t1/2) than low molecular weight PFECA compounds (HFPO-DA and PFO4DA) and even legacy PFOA. Although hepatomegaly is a common apical end point of PFAS exposure, the differentially expressed gene (DEG) profiles in the liver suggested significant differences between PFOA and the four PFECA compounds. Gene enrichment analysis supported a considerable inhibitory effect of PFECA, but not PFOA, on the glucocorticoid receptor (GR) signaling pathway. Both HFPO-TA and PFO5DoDA demonstrated a more pronounced ability to perturb RNA expression profiles in vivo and to suppress GR signaling in vitro compared to HFPO-DA and PFO4DA. Calculated reference doses (RfDs) emphasized the potential hazard of PFECA to human health. Overall, our findings indicate that PFECA alternatives do not ease the concerns raised from legacy PFAS pollution.

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

BACKGROUND

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

OBJECTIVES

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

METHODS/RESULTS

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

IMPACT STATEMENT

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

Bioaccumulation, tissue distribution, and maternal transfer of novel PFOS alternatives (6:2 Cl-PFESA and OBS) in wild freshwater fish from Poyang Lake, China

As emerging alternatives to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA) and sodium p-perfluorous nonenox-benzenesulfonate (OBS) were frequently detected in the four freshwater fish species collected from Poyang Lake. Median concentrations of 6:2 Cl-PFESA and OBS in fish tissues were 0.046-6.0 and 0.46-5.1 ng/g wet weight, respectively. The highest concentrations of 6:2 Cl-PFESA was found in fish livers, whereas OBS was found in the pancreas, brain, gonads, and skin. The tissue distribution pattern of 6:2 Cl-PFESA is similar to that of PFOS. The tissue/liver ratios of OBS were higher than those of PFOS, suggesting that OBS has a greater tendency to transfer from the liver to other tissues. The logarithmic bioaccumulation factors (log BAFs) of 6:2 Cl-PFESA in three carnivorous fish species were greater than 3.7, whereas those of OBS were less than 3.7, indicating that 6:2 Cl-PFESA had a strong bioaccumulation potential. Notably, sex- and tissue-specific bioaccumulation of OBS has also been observed in catfish. Most tissues (except the gonads) exhibited higher OBS concentrations in males than in females. However, no differences were found for 6:2 Cl-PFESA and PFOS. Maternal transfer efficiency of OBS was higher than that of 6:2 Cl-PFESA and PFOS in catfish (p < 0.05), indicating that OBS presents a higher risk of exposure to males and offspring through maternal offloading.

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

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

Legacy and Emerging Per- and Polyfluoroalkyl Substances Behave Distinctly in Spatial Distribution and Multimedia Partitioning: A Case Study in the Pearl River, China

Per- and polyfluoroalkyl substances (PFASs) have attracted worldwide attention due to their ubiquitous occurrence, bioaccumulation, and toxicological effects, yet the fate of PFASs in a lotic ecosystem is largely unknown. To elucidate spatial distribution and multimedia partitioning of legacy and emerging PFASs in a lotic river flowing into an estuary, PFASs were synchronously analyzed in water, suspended particulate matter (SPM), sediment, and biota samples collected along Guangzhou reach of the Pearl River, South China. Geographically, the concentrations of PFASs in the water phase showed a decreasing trend from the upper and middle sections (urban area) to the down section (suburban area close to estuary) of the river. While perfluorooctanoic acid predominated in water and SPM, more diverse compositions were observed in sediment and biota with the increase in contributions of long-chain PFASs. Field-derived sediment-water partitioning coefficients (K_d) and bioaccumulation factors (BAFs) of PFASs increased with the increase in perfluorinated carbons. Besides hydrophobicity, water pH and salinity significantly affected the multimedia partitioning of PFASs in a lotic ecosystem. In addition, 87 homologues (63 classes) were identified as emerging PFASs in four media using suspect analysis. Interestingly, K_d and BAF of the emerging PFASs were often higher than legacy PFASs containing the same perfluorinated carbons, raising a special concern on the environmental risk of emerging PFASs.

Occurrence and Distribution of Per- and Polyfluoroalkyl Substances in Tianjin, China: The Contribution of Emerging and Unknown Analogues

Tianjin, located in Bohai Bay, China, constitutes a relevant study area to investigate emerging per- and polyfluoroalkyl substances (PFASs) due to its high population density, clustering of chemical and aircraft industries, as well as international airports, harbors, and oil rigs. In this study, 53 anionic, zwitterionic, and cationic PFASs were monitored in river surface water, groundwater, seawater, and sediments in this area (overall n = 226). 6:2 chlorinated polyfluorinated ether sulfonic acid (Cl-PFESA), perfluorooctanoic acid, and perfluorooctane sulfonic acid were generally the predominant PFASs. 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) was also widespread (occurrence >86%), with the highest concentration (1300 ng/L) detected at contamination hot spots impacted by wastewater effluents. The aqueous film-forming foam (AFFF)-related PFASs with sulfonamide betaine, amine oxide, amine, or quaternary ammonium moieties are also reported for the first time in river water and seawater samples. Fifteen classes of infrequently reported PFASs, including n:2 FTABs and n:2 fluorotelomer sulfonamide amines, hydrogen-substituted PFESA homologues, and p-perfluorous nonenoxybenzenesulfonate (OBS), were also identified in the water and sediment samples using suspect screening. Field-derived sediment-water distribution coefficients (K_d) of these emerging PFASs are provided for the first time, confirming that cationic and zwitterionic PFASs tend to be strongly associated with sediments.

Robust Matrix Effect-Free Method for Simultaneous Determination of Legacy and Emerging Per- and Polyfluoroalkyl Substances in Crop and Soil Matrices

Increasing use of emerging per- and polyfluoroalkyl substances (PFASs) has caused extensive concerns around the world. Effective detection methods to trace their pollution characteristics and environmental behaviors in complex soil-crop systems are urgently needed. In this study, a reliable and matrix effect (ME)-free method was developed for simultaneous determination of 14 legacy and emerging PFASs, including perfluorooctanoic acid, perfluorooctane sulfonate, 6 hydrogenous PFASs, 3 chlorinated PFASs, and 3 hexafluoropropylene oxide homologues, in 6 crop (the edible parts) and 5 soil matrices using ultrasonic extraction combined with solid-phase extraction and ultraperformance liquid chromatography-mass spectrometry (MS)/MS. The varieties of extractants and cleanup cartridges, the dosage of ammonia hydroxide, and the ME were studied to obtain an optimal pretreatment procedure. The developed method had high sensitivity and accuracy with satisfactory method detection limits (2.40-83.03 pg/g dry weight) and recoveries (72-117%) of all target analytes in matrices at five concentrations, that is, 0.1, 1, 10, 100, and 1000 ng/g. In addition, the ME of this method (0.82-1.15) was negligible for all PFASs, even considering 11 different matrices. The successful application of the ME-free method to simultaneously determine the legacy and emerging PFASs in crop and soil samples has demonstrated its excellent practicability for monitoring emerging PFASs in soil-crop systems.

Strategies for grouping per- and polyfluoroalkyl substances (PFAS) to protect human and environmental health

Grouping strategies are needed for per- and polyfluoroalkyl substances (PFAS), in part, because it would be time and resource intensive to test and evaluate the more than 4700 PFAS on the global market on a chemical-by-chemical basis. In this paper we review various grouping strategies that could be used to inform actions on these chemicals and outline the motivations, advantages and disadvantages for each. Grouping strategies are subdivided into (1) those based on the intrinsic properties of the PFAS (e.g. persistence, bioaccumulation potential, toxicity, mobility, molecular size) and (2) those that inform risk assessment through estimation of cumulative exposure and/or effects. The most precautionary grouping approach of those reviewed within this article suggests phasing out PFAS based on their high persistence alone (the so-called "P-sufficient" approach). The least precautionary grouping approach reviewed advocates only grouping PFAS for risk assessment that have the same toxicological effects, modes and mechanisms of action, and elimination kinetics, which would need to be well documented across different PFAS. It is recognised that, given jurisdictional differences in chemical assessment philosophies and methodologies, no one strategy will be generally acceptable. The guiding question we apply to the reviewed grouping strategies is: grouping for what purpose? The motivation behind the grouping (e.g. determining use in products vs. setting guideline levels for contaminated environments) may lead to different grouping decisions. This assessment provides the necessary context for grouping strategies such that they can be adopted as they are, or built on further, to protect human and environmental health from potential PFAS-related effects.

In Vivo Generation of PFOA, PFOS, and Other Compounds from Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in a Terrestrial Invertebrate (Lumbricus terrestris)

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are two environmentally persistent per- and polyfluoroalkyl substances (PFAS) that have been detected globally in human tissues and fluids. As part of a project investigating the indirect sources of PFOA/PFOS in the environment and engineered systems, this study is concerned with the mechanisms leading to their in vivo generation in terrestrial invertebrates. We demonstrate here the formation of PFOA and PFOS in earthworms (Lumbricus terrestris) from a group of four zwitterionic/cationic polyfluoroalkyl amides and sulfonamides. In bioaccumulation tests, the zwitterionic PFAS compounds were metabolized within 10 days to PFOA/PFOS at yields of 3.4-20.8 mol % by day 21 and several infrequently reported PFAS species for which chemical structures were determined using high-resolution mass spectrometry. Cationic PFAS, on the other hand, were found to be much less metabolizable in terms of the number (n = 2) and yields (0.9-5.1 mol %) of metabolites. Peak-shaped bioaccumulation profiles were frequently observed for the studied PFAS. Residual zwitterionic/cationic PFAS in earthworms were detected at the end of the elimination phase, indicating that not all zwitterionic/cationic PFAS molecules in vivo are available for enzymatic degradation. Finally, the relative importance of different exposure routes (i.e., waterborne and dietary exposure) was investigated.

Nontargeted identification of per- and polyfluoroalkyl substances in human follicular fluid and their blood-follicle transfer

The female reproductive toxicity of per- and polyfluoroalkyl substances (PFAS) has raised concerns, but knowledge about their human preconception exposure is limited. In this study, 15 emerging PFAS were identified in follicular fluid samples from healthy women by using high-resolution mass spectrometry, and Cl-substituted perfluoroalkyl ether sulfonates (Cl-PFESAs) including 4:2, 5:2, 6:2, and 8:2 Cl-PFESAs, 4:4 C₈ perfluoroalkyl ether sulfonate (PFESA), C₈ perfluoroalkyl ether carboxylate (PFECA), and C₈ polyether PFECA (Po-PFECA) were detected in over 50% of 28 follicular fluid samples. Ten legacy PFAS were also detected, and the geometric mean concentration of PFOS was the highest (4.82 ng/mL), followed by PFOA (4.60 ng/mL), 6:2 Cl-PFESA (1.09 ng/mL), PFHxS (0.515 ng/mL), PFNA (0.498 ng/mL), and C₈ PFECA (0.367 ng/mL). The blood-follicle transfer efficiencies for PFCAs decreased with increasing chain length (0.96 for PFHpA, 0.56 for PFTriDA), and the transfer efficiencies of C₈ PFECA (0.78) was significantly higher than that of PFOA (0.76). The transfer efficiencies of 4:2 Cl-PFESA (0.73), 6:2 Cl-PFESA (0.75) and 8:2 Cl-PFESA (0.91) were significantly higher than that (0.70) of PFOS (p = 0.028, 0.026 and 0.002, respectively). This study constitutes the first report of the human oocyte exposure to emerging PFAS and their blood-follicle transfer abilities.