Transplacental Transfer of Per- and Polyfluoroalkyl Substances Identified in Paired Maternal and Cord Sera Using Suspect and Nontarget Screening

F-53B stimulated vascular smooth muscle cell phenotypic switch and vascular remodeling via ferroptosis-related pathway

The compound 6:2 chlorinated polyfluorinated ether sulfonate (F53B), an alternative to perfluorooctane sulfonate (PFOS), has been widely utilized in China. Although the connection between the exposure and toxicity of F53B is established, the role and mechanisms of the compound in promoting vascular remodeling are yet to be elucidated. Thus, the present study investigated the impact of F53B on the function of vascular smooth muscle cells (VSMCs) and vascular remodeling. The data exhibited that F53B stimulates vascular morphological alterations in vivo, and exposure to the compound caused excessive VSMCs ferroptosis and phenotype switching, as determined using phenotype and molecular assays. Moreover, Fer-1 reversed F-53B-induced VSMC dysfunction and vascular remodeling. Furthermore, F53B activated the ferroptosis-related pathway, encompassing ATR expression and LOC101929922/miR-542-3p/ACSL4 pathway. Thus, the current results elaborated on the multifaceted toxicities of F53B that induce vascular remodeling, thereby necessitating the assessment of vasotoxicity risks associated with the compound.

Deep Learning Bridged Bioactivity, Structure, and GC-HRMS-Readable Evidence to Decipher Nontarget Toxicants in Sediments

Identifying causative toxicants in mixtures is critical, but this task is challenging when mixtures contain multiple chemical classes. Effect-based methods are used to complement chemical analyses to identify toxicants, yet conventional bioassays typically rely on an apical and/or single endpoint, providing limited diagnostic potential to guide chemical prioritization. We proposed an event-driven taxonomy framework for mixture risk assessment that relied on high-throughput screening bioassays and toxicant identification integrated by deep learning. In this work, the framework was evaluated using chemical mixtures in sediments eliciting aryl-hydrocarbon receptor activation and oxidative stress response. Mixture prediction using target analysis explained <10% of observed sediment bioactivity. To identify additional contaminants, two deep learning models were developed to predict fingerprints of a pool of bioactive substances (event driver fingerprint, EDFP) and convert these candidates to MS-readable information (event driver ion, EDION) for nontarget analysis. Two libraries with 121 and 118 fingerprints were established, and 247 bioactive compounds were identified at confidence level 2 or 3 in sediment extract using GC-qToF-MS. Among them, 12 toxicants were analytically confirmed using reference standards. Collectively, we present a "bioactivity-signature-toxicant" strategy to deconvolute mixtures and to connect patchy data sets and guide nontarget analysis for diverse chemicals that elicit the same bioactivity.

Impacts of PFOS, PFOA and their alternatives on the gut, intestinal barriers and gut-organ axis

With the restricted use of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), a number of alternatives to PFOS and PFOA have attracted great interest. Most of the alternatives are still characterized by persistence, bioaccumulation, and a variety of toxicity. Due to the production and use of these substances, they can be detected in the atmosphere, soil and water body. They affect human health through several exposure pathways and especially enter the gut by drinking water and eating food, which results in gut toxicity. In this review, we summarized the effects of PFOS, PFOA and 9 alternatives on pathological changes in the gut, the disruption of physical, chemical, biological and immune barriers of the intestine, and the gut-organ axis. This review provides a valuable understanding of the gut toxicity of PFOS, PFOA and their alternatives as well as the human health risks of emerging contaminants.

Sodium p-perfluorinated noneoxybenzen sulfonate (OBS) induced neurotoxicity in zebrafish through mitochondrial dysfunction

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS)-one of the main alternatives to perfluorooctane sulfonate-has been increasingly detected in both aquatic environments and human bodies. Therefore, the pathogenic risks of OBS exposure warrant attention, especially its central nervous system toxicity mechanism under long-term exposure. In this study, the effects and mechanisms of OBS on the zebrafish brain at 40 days post exposure were examined. The results demonstrated that at 3.2 μg/L, OBS had no significant effect on the zebrafish brain, but 32 μg/L OBS caused depression or poor social behavior in zebrafish and reduced both their memory and survival ability. These changes were accompanied by histological damage and cell apoptosis. Furthermore, OBS caused the accumulation of excessive reactive oxygen species in the fish brain, leading to oxidative stress and subsequently cell apoptosis. Moreover, an imbalance of both inflammatory factors (IL-6, IL-1β, IL-10, TNF-α, and NF-κB) and neurotransmitters (GABA and Glu) led to neuroinflammation. Additionally, 32 μg/L OBS induced decreases in mitochondrial membrane potential and Na+-K+-ATPase activity, leading to both mitochondrial structural damage and the emergence of mitochondrial autophagosomes, partly explaining the neurotoxicity of OBS. These results help to analyze the target sites and molecular mechanisms of OBS neurotoxicity and provide a basis for the scientific evaluation of its health risks to humans.

Why are nH-perfluoroalkanoate ions more mobile than expected? Implications for identifying an emerging environmental pollutant

nH-Perfluoroalkyl carboxylic acids (nH-PFCAs) are emerging pollutants. Their identification by ion mobility is frustrated by the nH-PFCAs having unexpectedly small collision cross sections (CCS). Theory and experiment agree that this is because nH-PFCA ions undergo internal hydrogen bridging, and this insight will help guide the creation of more accurate methods for pollutant identification.

Combining Advanced Analytical Methodologies to Uncover Suspect PFAS and Fluorinated Pharmaceutical Contributions to Extractable Organic Fluorine in Human Serum (Tromsø Study)

A growing number of studies have reported that routinely monitored per- and polyfluoroalkyl substances (PFAS) are not sufficient to explain the extractable organic fluorine (EOF) measured in human blood. In this study, we address this gap by screening pooled human serum collected over 3 decades (1986-2015) in Tromsø (Norway) for >5000 PFAS and >300 fluorinated pharmaceuticals. We combined multiple analytical techniques (direct infusion Fourier transform ion cyclotron resonance mass spectrometry, liquid chromatography-Orbitrap-high-resolution mass spectrometry, and total oxidizable precursors assay) in a three-step suspect screening process which aimed at unequivocal suspect identification. This approach uncovered the presence of one PFAS and eight fluorinated pharmaceuticals (including some metabolites) in human serum. While the PFAS suspect only accounted for 2-4% of the EOF, fluorinated pharmaceuticals accounted for 0-63% of the EOF, and their contribution increased in recent years. Although fluorinated pharmaceuticals often contain only 1-3 fluorine atoms, our results indicate that they can contribute significantly to the EOF. Indeed, the contribution from fluorinated pharmaceuticals allowed us to close the organofluorine mass balance in pooled serum from 2015, indicating a good understanding of organofluorine compounds in humans. However, a portion of the EOF in human serum from 1986 and 2007 still remained unexplained.

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.

Angiotoxic effects of chlorinated polyfluorinated ether sulfonate, a novel perfluorooctane sulfonate substitute, in vivo and in vitro

Chlorinated polyfluorinated ether sulfonate (Cl-PFESA), a substitute for perfluorooctane sulfonate (PFOS), has been widely used in the Chinese electroplating industry under the trade name F-53B. The production and use of F-53B is keep increasing in recent years, consequently causing more emissions into the environment. Thus, there is a growing concern about the adverse effects of F-53B on human health. However, related research is very limited, particularly in terms of its toxicity to the vascular system. In this study, C57BL/6 J mice were exposed to 0.04, 0.2, and 1 mg/kg F-53B for 12 weeks to assess its impact on the vascular system. We found that F-53B exposure caused aortic wall thickening, collagen deposition, and reduced elasticity in mice. In addition, F-53B exposure led to a loss of vascular endothelial integrity and a vascular inflammatory response. Intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were found to be indispensable for this process. Furthermore, RNA sequencing analysis revealed that F-53B can decrease the repair capacity of endothelial cells by inhibiting their proliferation and migration. Collectively, our findings demonstrate that F-53B exposure induces vascular inflammation and loss of endothelial integrity as well as suppresses the repair capacity of endothelial cells, which ultimately results in vascular injury, highlighting the need for a more thorough risk assessment of F-53B to human health.

Temporal Trend of Serum Perfluorooctanoic Acid and Perfluorooctane Sulfonic Acid among U.S. Adults with or without Comorbidities in NHANES 1999-2018

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are associated with adverse health effects. This study examined the trend of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) levels in individuals with and without pre-existing comorbidities. We analyzed the characteristics of 13,887 participants across nine U.S. NHANES cycles (1999-2000 to 2017-2018) and calculated the geometric mean (GM) of PFOA and PFOS levels, standardized by sex and age. A joinpoint regression model was used to analyze the temporal trends of serum PFOA and PFOS levels. We observed declining PFOA and PFOS serum levels among adults in NHANES from 1999-2000 to 2017-2018. Serum PFOA and PFOS concentrations were higher in men, smokers, and individuals with pre-existing CKD, hyperlipidemia, CVD, and cancer. We observed faster decline rates in PFOA levels among individuals with diabetes and CKD and faster decline rates in PFOS levels among individuals with diabetes and those without CKD. This study provided evidence of varying levels and changing trends of PFOA and PFOS between groups with and without established chronic disease, highlighting the role of environmental chemicals in the onset and development of chronic diseases.

Integrated Analysis of Per- and Polyfluoroalkyl Substance Exposure and Metabolic Profiling of Elderly Residents Living near Industrial Plants

Per- and polyfluoroalkyl substances (PFASs) are widely used in industrial production, causing potential health risks to the residents living around chemical industrial plants; however, the lack of data on population exposure and adverse effects impedes our understanding and ability to prevent risks. In this study, we performed screening and association analysis on exogenous PFAS pollutants and endogenous small-molecule metabolites in the serum of elderly residents living near industrial plants. Exposure levels of 11 legacy and novel PFASs were determined. PFOA and PFOS were major contributors, and PFNA, PFHxS, and 6:2 Cl-PFESA also showed high detection frequencies. Association analysis among PFASs and 287 metabolites identified via non-target screening was performed with adjustments of covariates and false discovery rate. Strongly associated metabolites were predominantly lipid and lipid-like molecules. Steroid hormone biosynthesis, primary bile acid biosynthesis, and fatty-acid-related pathways, including biosynthesis of unsaturated fatty acids, linoleic acid metabolism, α-linolenic acid metabolism, and fatty acid biosynthesis, were enriched as the metabolic pathways associated with mixed exposure to multiple PFASs, providing metabolic explanation and evidence for the potential mediating role of adverse health effects as a result of PFAS exposure. Our study achieved a comprehensive screening of PFAS exposure and associated metabolic profiling, demonstrating the promising application for integrated analysis of exposome and metabolome.

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.

Screening Novel Per- and Polyfluoroalkyl Substances in Human Blood Based on Nontarget Analysis and Underestimated Potential Health Risks

Nontarget analysis has gained prominence in screening novel perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the environment, yet remaining limited in human biological matrices. In this study, 155 whole blood samples were collected from the general population in Shijiazhuang City, China. By nontarget analysis, 31 legacy and novel PFASs were assigned with the confidence level of 3 or above. For the first time, 11 PFASs were identified in human blood, including C1 and C3 perfluoroalkyl sulfonic acids (PFSAs), C4 ether PFSA, C8 ether perfluoroalkyl carboxylic acid (ether PFCA), C4-5 unsaturated perfluoroalkyl alcohols, C9-10 carboxylic acid-perfluoroalkyl sulfonamides (CA-PFSMs), and C1 perfluoroalkyl sulfonamide. It is surprising that the targeted PFASs were the highest in the suburban population which was impacted by industrial emission, while the novel PFASs identified by nontarget analysis, such as C1 PFSA and C9-11 CA-PFSMs, were the highest in the rural population who often drank contaminated groundwater. Combining the toxicity prediction results of the bioaccumulation potential, lethality to rats, and binding affinity to target proteins, C3 PFSA, C4 and C7 ether PFSAs, and C9-11 CA-PFSMs exhibit great health risks. These findings emphasize the necessity of broadening nontarget analysis in assessing the PFAS exposure risks, particularly in rural populations.

Suspect and nontarget screening of per- and polyfluoroalkyl substances based on ion mobility mass spectrometry and machine learning techniques

High-resolution mass spectrometry (HRMS)-based suspect and nontarget screening techniques are powerful tools for the comprehensive identification of per- and polyfluoroalkyl substances (PFASs), but the interference of complex matrices (especially for wastewater) pose an analytical challenge. This study explored the potential of combining ion mobility spectrometry (IMS) with HRMS and machine learning techniques to achieve the rapid and accurate suspect and nontarget screening of PFAS in wastewater. There were fewer interfering peaks and a clearer spectrum in the data acquired by IMS-HRMS than conventional HRMS. The introduction of collision cross section (CCS) in PFAS homologous series search could filter out 63% of false positive results. Retention time and CCS prediction models were helpful in improving the confidence for PFAS qualitative identification and the random forest algorithm combined with RDKit descriptor performed best for CCS prediction. With the inclusion of extra dimensional information, this study also proposed a comprehensive and concise confidence assignment criterion to better convey the certainty of the qualitative identification of PFAS. Finally, a total of 56 potential PFASs were identified in the wastewater sample using the newly developed method and 45 of them were identified outside reference standards, emphasizing the importance of suspect and nontarget screening for PFAS.

Adipogenic and osteogenic effects of OBS and synergistic action with PFOS via PPARγ-RXRα heterodimers

Sodium p-perfluorous nonenoxybenzenesulfonate (OBS) is a novel alternative to perfluorooctane sulfonate (PFOS), with environmental health risks largely unknown. The present study aims to unravel the adipogenesis effects and underlying molecular initiating events of OBS, which are crucial for understanding and predicting its adverse outcome. In undifferentiated human mesenchymal stem cells (hMSCs), exposure to 1-100 nM of OBS for 7 days stimulated reactive oxygen species production. In the subsequent multipotent differentiation, hMSCs favored adipogenesis and repressed osteogenesis. The point of departure (PoD) for cellular responses of OBS was 38.85 nM, higher than PFOS (0.39 nM). Notably, OBS/PFOS co-exposure inhibited osteogenesis and synergistically promoted adipogenesis. Consistently, the expression of adipogenic marker genes was up-regulated, while that of osteogenic marker genes was down-regulated. The decreased adiponectin and elevated tumor necrosis factor α (TNFα) secretion were observed in differentiated cells exposed to the mixture of OBS and PFOS. The co-treatment of a peroxisome proliferator-activated receptor γ (PPARγ) antagonist alleviated the adipogenic effects of PFOS and its combination with OBS. Moreover, OBS/PFOS co-exposure induced peroxisome PPARγ activation in reporter gene assays, and increased formation of PPARγ - retinoid X receptor α (RXRα) heterodimers measured by co-immunoprecipitation assays. Molecular docking showed interaction energy of OBS (-20.7 kcal/mol) with intact PPARγ-RXRα complex was lower than that of PFOS (-25.9 kcal/mol). Overall, single OBS exhibited lower potency in inducing adipogenesis but is comparable to PFOS in repressing osteogenesis, whereas OBS/PFOS co-exposure increases interaction with PPARγ-RXRα heterodimers, resulting in the synergistic activation of PPARγ, ultimately enhancing adipogenesis at the expense of osteogenic differentiation. The results indicate the potential health risks of increased obesity and decreased bone density caused by OBS and its co-exposure with PFOS, as well as other perfluorinated alkylated substances mixtures.

Optimization for the analysis of 42 per- and polyfluorinated substances in human plasma: A high-throughput method for epidemiological studies

There is an increasing awareness about the presence of per- and polyfluoroalkyl substances (PFAS) in many environmental and biological compartments, including human biofluids and tissues. However, the increase of PFAS replacements, including alternatives with shorter chain or less bioaccumulative potential, has broaden the exposure and the need for wider identification procedures. Moreover, the low volumes available for human blood or plasma, and the high number of samples needed to assess adequately epidemiologic studies, require particularly fast, reproducible and, if possible, miniaturized protocols. Therefore, accurate and robust analytical methods are still needed to quantify the PFAS's burden in humans and to understand potential health risks. In this study, we have developed and validated the analysis of 42 PFAS in human plasma by means of a Captiva 96-well micro extraction plate and a LC-q-Orbitrap. For the optimization of the analytical workflow, three extraction/clean-up methods were tested, and the selected one was validated using spiked artificial and bovine plasma at four concentration levels. The final method showed high absolute recoveries for the 42 PFAS, ranging from 52% to 130%, instrumental detection limits between 0.001-0.6 ng mL-1, overall good precision (CV < 20% for most of the PFAS) and a low uncertainty (< 30% of relative expanded deviation, k = 2). The method was further validated both with the NIST plasma Standard Reference Material 1950, showing that the accuracy of the provided results was between 63%-101%, and by the proficiency test arranged by the Arctic Monitoring Assessment Program (AMAP, 2022) obtaining satisfactory results within 95% confidence interval of the assigned value.

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

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

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.

Novel PFOS alternative OBS inhibits body growth of developing zebrafish by triggering thyroid function disorder and osteoclast differentiation

The extensive use of the perfluorooctane sulfonate (PFOS) alternative sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has resulted in its widespread detection in the environment and enrichment in wildlife and humans. However, little is known about its potential toxicity, particularly in terms of body development. In this study, zebrafish embryos were acutely exposed to PFOS and OBS for a comparative developmental toxicity assessment. Both PFOS and OBS led to lower body weight and shorter body length, and the damaging effects of PFOS were more severe than those of OBS at the same exposure concentration. Biochemical assays of THs and transcription profiles correlated to the HPT axis demonstrated that OBS-induced body development inhibition resulted mainly from interference in THs synthesis, transfer, coupling with receptors, and conversion from T4 to T3, which was similar to the case of PFOS, except that the disruptive effects of OBS on thyroid function were more intense. Further transcriptome analysis showed that PFOS and OBS also promoted osteoclast differentiation, aggravating the inhibitory effects on body growth, and that PFOS had more obvious inhibitory effects than OBS. This study systematically explored the inhibitory effects of PFOS and OBS exposure on body development and tightly linked the toxic effects to thyroid function disorder and osteoclast differentiation. Our findings highlight that the health risks associated with OBS, an emerging substitute for PFOS, should not be ignored.

Trimester-specific hemodynamics of per- and polyfluoroalkyl substances and its relation to lipid profile in pregnant women

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants widely detected in blood from pregnant women, yet limited study evaluated the trimester-specific variance of serum PFAS, and even less is known for the window of vulnerability to lipids metabolism interrupting effects of PFAS during pregnancy. We quantified 16 legacy, 3 emerging PFAS, and lipid biomarkers in 286 serum samples from 118 pregnant women. All target PFAS, except perfluorotridecanoic acid (PFTrDA), in maternal serum showed moderate to low temporal irregular variability across gestation (average intraclass correlation coefficients ≥ 0.57), while the generalized estimating equations showed a significant declining trend in the serum levels during pregnancy (p for trend < 0.05). The decline of 6:2 chlorinated polyfluorinated ether sulfonate in maternal serum was the greatest with a change of - 21.63% from 1st to 2nd trimester, which indicated a possible higher accumulation of this emerging PFAS in fetal compartment. Multiple linear regression, multiple informant model and Bayesian kernel machine regression showed a higher vulnerability in the 1st trimester to effects of PFAS exposure on serum lipids of pregnant women. The results highlighted the importance of the study timing of PFAS exposure during pregnancy.

Exposure to per- and polyfluoroalkyl substances in women with twin pregnancies: Patterns and variability, transplacental transfer, and predictors

The extensive exposure to per- and polyfluoroalkyl substances (PFASs) has raised public health concerns. The issue of PFAS exposures in women with twin pregnancies remains unresolved. To determine exposure profiles, the transplacental transfer efficiencies (TTEs) of PFASs and predictors were estimated. We found that serum PFASs were widely detected, with detection rates of over 50% for 12 PFASs in maternal serum throughout pregnancy. The majority of PFAS levels exhibited fair to good reproducibility (ICCs > 0.40). Moderate to low correlations were observed for most PFASs between twin cord serum and maternal serum at three trimesters (rs = 0.13-0.77, p values < 0.01). We first presented a U-shaped trend for TTEs with increasing chain length for perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) in twins, even in twin sex subgroups. Further, we found that PC4 and PC5 (indicators of exposure to PFHxS and 6:2 Cl-PFESA) were positively associated with age (β = 0.85, 1.30, and 1.36, respectively). Our findings suggested that there is moderate variability among certain PFASs and that these PFASs have the ability to cross the placental barrier. Exposure patterns were found to be associated with maternal age.

SWATH-F: A Novel Nontarget Strategy Based on the SWATH-MS Deconvolution Method Assisting in Annotating PFAS Homologues in Multisample Studies

In order to identify emerging per- and polyfluoroalkyl substances (PFASs) and their alternatives in the environment or population, we need to perform extensive profiling of PFASs to determine their distribution in samples. The sequential window acquisition of all theoretical fragment-ion spectra (SWATH mode) is capable of obtaining a wide range of MS2 spectra but is difficult for direct identification of PFASs due to its complex MS2 spectra, and the nontarget screening method is difficult to identify due to its lack of a priori information. In this study, we demonstrated the great potential of SWATH-F, a nontarget fragment-based homologue screening method in combination with the SWATH-MS deconvolution, for detecting PFASs. We evaluated the application of SWATH-F to gradient spiked samples and real population serum samples, compared it with nontarget homologue screening in the information-dependent acquisition mode (IDA mode), and obtained better results for SWATH-F with 276% improvement (IDA:17 PFASs, SWATH-F: 64 PFASs) in identification. In addition, we automated the screening and identification process of SWATH-F to facilitate its use by researchers. SWATH-F is freely available on GitHub (https://github.com/njuIrene/SWATH-F) under an MIT license.

Further Insight into Extractable (Organo)fluorine Mass Balance Analysis of Tap Water from Shanghai, China

The ubiquitous occurrence of per- and polyfluoroalkyl substances (PFAS) and the detection of unexplained extractable organofluorine (EOF) in drinking water have raised growing concerns. A recent study reported the detection of inorganic fluorinated anions in German river systems, and therefore, in some samples, EOF may include some inorganic fluorinated anions. Thus, it might be more appropriate to use the term "extractable fluorine (EF) analysis" instead of the term EOF analysis. In this study, tap water samples (n = 39) from Shanghai were collected to assess the levels of EF/EOF, 35 target PFAS, two inorganic fluorinated anions (tetrafluoroborate (BF4-) and hexafluorophosphate (PF6-)), and novel PFAS through suspect screening and potential oxidizable precursors through oxidative conversion. The results showed that ultra-short PFAS were the largest contributors to target PFAS, accounting for up to 97% of ΣPFAS. To the best of our knowledge, this was the first time that bis(trifluoromethanesulfonyl)imide (NTf2) was reported in drinking water from China, and p-perfluorous nonenoxybenzenesulfonate (OBS) was also identified through suspect screening. Small amounts of precursors that can be oxidatively converted to PFCAs were noted after oxidative conversion. EF mass balance analysis revealed that target PFAS could only explain less than 36% of EF. However, the amounts of unexplained extractable fluorine were greatly reduced when BF4- and PF6- were included. These compounds further explained more than 44% of the EF, indicating the role of inorganic fluorinated anions in the mass balance analysis.

Per- and polyfluoroalkyl substances (PFAS) in white-tailed sea eagle eggs from Sweden: temporal trends (1969-2021), spatial variations, fluorine mass balance, and suspect screening

Temporal and spatial trends of 15 per- and polyfluoroalkyl substances (PFAS) were determined in white-tailed sea eagle (WTSE) eggs (Haliaeetus albicilla) from two inland and two coastal regions of Sweden between 1969 and 2021. PFAS concentrations generally increased from ∼1969 to ∼1990s-2010 (depending on target and site) and thereafter plateaued or declined, with perfluorooctane sulfonamide (FOSA) and perfluorooctane sulfonate (PFOS) declining faster than most perfluoroalkyl carboxylic acids (PFCAs). The net result was a shift in the PFAS profile from PFOS-dominant in 1969-2010 to an increased prevalence of PFCAs over the last decade. Further, during the entire period higher PFAS concentrations were generally observed in coastal populations, possibly due to differences in diet and/or proximity to more densely populated areas. Fluorine mass balance determination in pooled samples from three of the regions (2019-2021) indicated that target PFAS accounted for the vast majority (i.e. 81-100%) of extractable organic fluorine (EOF). Nevertheless, high resolution mass-spectrometry-based suspect screening identified 55 suspects (31 at a confidence level [CL] of 1-3 and 24 at a CL of 4-5), of which 43 were substances not included in the targeted analysis. Semi-quantification of CL ≤ 2 suspects increased the identified EOF to >90% in coastal samples. In addition to showing the impact of PFAS regulation and phase-out initiatives, this study demonstrates that most extractable organofluorine in WTSE eggs is made up of known (legacy) PFAS, albeit with low levels of novel substances.

Prenatal exposures to per- and polyfluoroalkyl substances and epigenetic aging in umbilical cord blood: The Healthy Start study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous, environmentally persistent chemicals, and prenatal exposures have been associated with adverse child health outcomes. Prenatal PFAS exposure may lead to epigenetic age acceleration (EAA), defined as the discrepancy between an individual's chronologic and epigenetic or biological age.

OBJECTIVES

We estimated associations of maternal serum PFAS concentrations with EAA in umbilical cord blood DNA methylation using linear regression, and a multivariable exposure-response function of the PFAS mixture using Bayesian kernel machine regression.

METHODS

Five PFAS were quantified in maternal serum (median: 27 weeks of gestation) among 577 mother-infant dyads from a prospective cohort. Cord blood DNA methylation data were assessed with the Illumina HumanMethylation450 array. EAA was calculated as the residuals from regressing gestational age on epigenetic age, calculated using a cord-blood specific epigenetic clock. Linear regression tested for associations between each maternal PFAS concentration with EAA. Bayesian kernel machine regression with hierarchical selection estimated an exposure-response function for the PFAS mixture.

RESULTS

In single pollutant models we observed an inverse relationship between perfluorodecanoate (PFDA) and EAA (-0.148 weeks per log-unit increase, 95% CI: -0.283, -0.013). Mixture analysis with hierarchical selection between perfluoroalkyl carboxylates and sulfonates indicated the carboxylates had the highest group posterior inclusion probability (PIP), or relative importance. Within this group, PFDA had the highest conditional PIP. Univariate predictor-response functions indicated PFDA and perfluorononanoate were inversely associated with EAA, while perfluorohexane sulfonate had a positive association with EAA.

CONCLUSIONS

Maternal mid-pregnancy serum concentrations of PFDA were negatively associated with EAA in cord blood, suggesting a pathway by which prenatal PFAS exposures may affect infant development. No significant associations were observed with other PFAS. Mixture models suggested opposite directions of association between perfluoroalkyl sulfonates and carboxylates. Future studies are needed to determine the importance of neonatal EAA for later child health outcomes.

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.

The occurrence, tissue distribution, and PBT potential of per- and polyfluoroalkyl substances in the freshwater organisms from the Yangtze river via nontarget analysis

Numerous emerging per- and polyfluoroalkyl substances (PFASs) occur in the aquatic environment, posing a threat to aquatic ecosystems and human health. In this study, we conducted a nontarget analysis on 3 surface water samples and 92 tissue samples of 16 fish collected from the Yangtze River to investigate the patterns, tissue distribution, and environmental impacts of emerging PFASs. A total of 43 PFASs from 11 classes were identified, including 17 legacy PFASs and 26 emerging PFASs. Among the 43 PFASs, seven PFASs were reported in biota for the first time while five PFASs were reported in the environment for the first time. Chlorine substituted perfluoroalyl ether sulfonic acids were the major emerging PFASs detected in organisms. Our results showed that most emerging PFASs tended to accumulate in the liver whereas perfluorinated sulfonamides tended to accumulate in the blood, and all of the emerging PFASs accumulated less in the muscle. Methods for evaluating the persistence, bioaccumulation, and toxicity (PBT) of PFASs were developed by combining the in-silico methods and experimental methods. Long-chain PFASs were found to have extremely high PBT scores compared to short-chain PFASs. Additionally, most emerging PFASs exhibited comparable PBT characteristics with legacy PFASs, especially Cl-substituted PFASs.

Discovery of 35 novel classes of per- and polyfluoroalkyl substances in representative commercial fluorinated products in China

Per- and polyfluoroalkyl substances (PFAS) have received increasing scientific and regulatory attention due to their global distribution and health hazards. However, little is known about the PFAS composition of fluorinated products commercially available in China. In this study, a sensitive and robust analytical method was proposed for the comprehensive characterization of PFAS in aqueous film-forming foam and fluorocarbon surfactants in the domestic market based on liquid chromatography-high resolution mass spectrometry in full scan acquisition mode followed by parallel reaction monitoring mode. Consequently, a total of 102 PFAS from 59 classes were elucidated, of which 35 classes are reported for the first time, including 27 classes of anionic, seven classes of zwitterionic, and one class of cationic PFAS. The anionic-type products are mainly C6 fluorotelomerization-based (FT-based) PFAS. Perfluorooctanoic acid and perfluorooctane sulfonate are negligible, while some known electrochemical fluorination-based long-chain precursors in zwitterionic products are worthy of concern because of their high abundance and potential degradation. New precursors detected in zwitterionic products are FT-based PFAS, for example, 6:2 FTSAPr-AHOE and 6:2 FTSAPr-diMeAmPrC. The structural elucidation of PFAS in commercial products facilitates a better assessment of human exposure and environmental release.

Prenatal exposure to per- and polyfluoroalkyl substances and pregnancy outcome in Austria

Per- and polyfluoroalkyl substances (PFAS) are a large group of persistent industrial chemicals that can harm reproductive health. PFAS levels were analysed to determine the current sources of exposure and possible associations between prenatal PFAS exposure and adverse pregnancy outcome. Samples from 136 mother-newborn pairs recruited between 2017 and 2019 were analysed for the presence of 31 target PFAS in maternal serum, umbilical cord serum, and placental tissue by high-performance liquid chromatography coupled to a tandem mass spectrometer. Questionnaires and medical records were used to survey sources of exposure and pregnancy outcome, including small for gestational age (SGA), fetal growth restriction (FGR), preeclampsia (PE), preterm birth, large for gestational age (LGA) and gestational diabetes mellitus (GDM). Data were analysed for individual PFAS and sum4PFAS (sum of perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) serum levels) in logistic regression analyses and categorical regression analyses. Compared to data from a previous Viennese study in 2010-12, sum4PFAS levels were generally lower. Sum4PFAS serum levels of three women (2.2%) exceeded 6.9 µg/L, a level that corresponds to the recently established tolerable weekly intake (TWI) of EFSA for nursing mothers aged 35 years; in the 2010/2012 study it was 13.6%. The large contribution of unidentified extractable organofluorine (EOF) fractions to total PFAS exposure is a concern. Study site, mean maternal corpuscular hemoglobin (MCH), use of facial lotion, and owning upholstered furniture were significantly influencing maternal exposure. While no effect of sum4PFAS on pregnancy outcome could be detected, we found highest placental PFDA levels in SGA births. PFHxS levels in umbilical cord and placenta were highest in preterm births. Further studies are needed to elucidate the relationship of prenatal PFAS exposure and pregnancy outcome, in particular to confirm whether and how placental PFDA levels may contribute to an increased risk for SGA.

Nutrition paves the way to environmental toxicants and influences fetal development during pregnancy

Nutrition plays a major role in the healthy pregnancy and development of the fetus. In addition, nutrition can expose humans to a wide range of potentially hazardous environmental constituents, such as organic pollutants and heavy metals from marine or agricultural food products while processing, producing, and packaging. Humans constantly face these constituents through air, water, soil, food, and domestic products. During pregnancy, the rate of cellular division and differentiation is higher; exposure to any of these environmental toxicants can lead to developmental defects as they cross the placental barrier and, in some cases, can harm the successive generation too, as some contaminants can act on the reproductive cells of the fetus (Diethylstilbestrol). Pregnant women are considered a vulnerable population to food contaminant exposure and require a proper dietary chart and conscious food choices. Food is a source of both essential nutrients and environmental toxicants. Here, we have researched the possible toxicants of the food industry and their influence on the fetus's in-utero development, along with the importance of dietary interventions and the need to balance a healthy diet to overcome the harms. The cumulative exposure to environmental toxicants can influence the mother's prenatal environment and affect the fetus's development.

Determinants of maternal and neonatal PFAS concentrations: a review

Per- and polyfluoroalkyl substances (PFAS) are used for their properties such as stain and water resistance. The substances have been associated with adverse health outcomes in both pregnant mothers and infants, including pre-eclampsia and low birthweight. A growing body of research suggests that PFAS are transferred from mother to fetus through the placenta, leading to in utero exposure. A systematic review was performed using the PubMed database to search for studies evaluating determinants of PFAS concentrations in blood matrices of pregnant mothers and neonates shortly after birth. Studies were included in this review if an observational study design was utilized, exposure to at least one PFAS analyte was measured, PFAS were measured in maternal or neonatal matrices, at least one determinant of PFAS concentrations was assessed, and results such as beta estimates were provided. We identified 35 studies for inclusion in the review and evaluated the PFAS and determinant relationships among the factors collected in these studies. Parity, breastfeeding history, maternal race and country of origin, and household income had the strongest and most consistent evidence to support their roles as determinants of certain PFAS concentrations in pregnant mothers. Reported study findings on smoking status, alcohol consumption, and pre-pregnancy body mass index (BMI) suggest that these factors are not important determinants of PFAS concentrations in pregnant mothers or neonates. Further study into informative factors such as consumer product use, detailed dietary information, and consumed water sources as potential determinants of maternal or neonatal PFAS concentrations is needed. Research on determinants of maternal or neonatal PFAS concentrations is critical to estimate past PFAS exposure, build improved exposure models, and further our understanding on dose-response relationships, which can influence epidemiological studies and risk assessment evaluations. Given the potential for adverse outcomes in pregnant mothers and neonates exposed to PFAS, it is important to identify and understand determinants of maternal and neonatal PFAS concentrations to better implement public health interventions in these populations.

A Review on Per- and Polyfluoroalkyl Substances in Pregnant Women: Maternal Exposure, Placental Transfer, and Relevant Model Simulation

Per- and polyfluoroalkyl substances (PFASs) are important and ubiquitous environmental contaminants worldwide. These novel contaminants can enter human bodies via various pathways, subsequently posing risks to the ecosystem and human health. The exposure of pregnant women to PFASs might pose risks to the health of mothers and the growth and development of fetuses. However, little information is available about the placental transfer of PFASs from mothers to fetuses and the related mechanisms through model simulation. In the present study, based upon a review of previously published literature, we initially summarized the exposure pathways of PFASs in pregnant women, factors affecting the efficiency of placental transfer, and mechanisms associated with placental transfer; outlined simulation analysis approaches using molecular docking and machine learning to reveal the mechanisms of placental transfer; and finally highlighted future research emphases that need to be focused on. Consequently, it was notable that the binding of PFASs to proteins during placental transfer could be simulated by molecular docking and that the placental transfer efficiency of PFASs could also be predicted by machine learning. Therefore, future research on the maternal-fetal transfer mechanisms of PFASs with the benefit of simulation analysis approaches is warranted to provide a scientific basis for the health effects of PFASs on newborns.

Integration of target, suspect, and nontarget screening with risk modeling for per- and polyfluoroalkyl substances prioritization in surface waters

Though thousands of per- and polyfluoroalkyl substances (PFAS) have been on the global market, most research focused on only a small fraction, potentially resulting in underestimated environmental risks. Here, we used complementary target, suspect, and nontarget screening for quantifying and identifying the target and nontarget PFAS, respectively, and developed a risk model considering their specific properties to prioritize the PFAS in surface waters. Thirty-three PFAS were identified in surface water in the Chaobai river, Beijing. The suspect and nontarget screening by Orbitrap displayed a sensitivity of > 77%, indicating its good performance in identifying the PFAS in samples. We used triple quadrupole (QqQ) under multiple-reaction monitoring for quantifying PFAS with authentic standards due to its potentially high sensitivity. To quantify the nontarget PFAS without authentic standards, we trained a random forest regression model which presented the differences up to only 2.7 times between measured and predicted response factors (RFs). The maximum/minimum RF in each PFAS class was as high as 1.2-10.0 in Orbitrap and 1.7-22.3 in QqQ. A risk-based prioritization approach was developed to rank the identified PFAS, and four PFAS (i.e., perfluorooctanoic acid, hydrogenated perfluorohexanoic acid, bistriflimide, 6:2 fluorotelomer carboxylic acid) were flagged with high priority (risk index > 0.1) for remediation and management. Our study highlighted the importance of a quantification strategy during environmental scrutiny of PFAS, especially for nontarget PFAS without standards.

The novel polyfluoroalkyl benzenesulfonate OBS exposure induces cell cycle arrest and senescence of rat pituitary cell GH3 via the p53/p21/RB pathway

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS), an economical alternative to perfluorooctane sulfonate (PFOS) in multiple industrial fields, is widely detected in the environment. The toxicity of OBS has received increasing attention. Pituitary cells are components of the endocrine system and act as vital regulators of homeostatic endocrine balance. However, the effects of OBS on pituitary cells remain unknown. The present study explores the effects of OBS (0.5, 5, and 50μM) on GH3 rat pituitary cells after treatment for 24, 48, and 72h. We found that OBS significantly inhibited cell proliferation in GH3 cells with remarkable senescent phenotypes, including enhanced SA-β-gal activity and expression of senescence-associated secretory phenotype (SASP)-related genes, cell cycle arrest, and upregulation of the senescence-related proteins γ-H2A.X and Bcl-2. OBS caused significant cell cycle arrest of GH3 cells at the G1-phase and concomitantly downregulated the expression of some key proteins for the G1/S transition, including cyclin D1 and cyclin E1. Consistently, the phosphorylation of retinoblastoma (RB), which plays a central role in regulating the cell cycle, was prominently reduced after OBS exposure. Furthermore, OBS notably activated the p53-p21 signalling pathway in GH3 cells, as evidenced by increased p53 and p21 expressions, enhanced p53 phosphorylation, and augmented p53 nuclear import. To our knowledge, this study is the first to reveal that OBS triggers senescence in pituitary cells via the p53-p21-RB signalling pathway. Our study demonstrates a novel toxic effect of OBS in vitro, and provides new perspectives for understanding the potential toxicity of OBS.

Nontarget analysis and fluorine atom balances of transformation products from UV/sulfite degradation of perfluoroalkyl contaminants

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of highly fluorinated, anthropogenic compounds that are used in a wide variety of consumer applications. Due to their widespread use and high persistence, PFAS are ubiquitous in drinking water, which is of concern due to the threats these compounds pose to human health. Reduction via the hydrated electron is a promising technology for PFAS remediation and has been well-studied. However, since previous work rarely reports fluorine atom balances and often relies on suspect screening, some transformation products are likely unaccounted for. Therefore, we performed non-target analysis using high-resolution mass spectrometry on solutions of perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate (PFBS), perfluorooctanoate (PFOA), and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate (GenX) that had been treated with UV/sulfite to produce hydrated electrons. We determined fluorine atom balances for all compounds studied, finding high fluorine atom balances for PFOS and PFBS. PFOA and GenX had lower overall fluorine atom balances, likely due to the production of volatile or very polar transformation products that were not measured by our methods. Transformation products identified by our analysis were consistent with literature, with a few exceptions. Namely, shorter-chain perfluorosulfonates (PFSA) and their H/F substituted counterparts were also detected from PFOS. This is an unexpected result based on literature, as no documented pathway exists for the formation of shorter-chain PFSA during UV/sulfite treatment. Furthermore, the nontarget approach we employed allowed for identification of novel, unsaturated products from the hydrated electron treatment of perfluorooctanesulfonate (PFOS) that warrant further investigation.

First Discovery of Iodinated Polyfluoroalkyl Acids by Nontarget Mass-Spectrometric Analysis and Iodine-Specific Screening Algorithm

Per- and polyfluoroalkyl acids (PFAAs) including polyfluoroalkyl carboxylic acids and polyfluoroalkyl sulfonic acids are a large category of crucial environmental pollutants of global concern. Besides known PFAAs, numerous unknown species may exist in the environment, urgently needing discovery and characterization. This study implemented nontarget analysis for a group of novel PFAA pollutants, viz., iodinated PFAAs (I-PFAAs) in wastewater from a fluorochemical manufacturing park by liquid chromatography-high-resolution mass spectrometry in combination with an iodine-specific data-processing algorithm. The algorithm took into account the diagnostic fragment iodine ion (I-) together with carbon and sulfur isotopologue distributions. In total, 18 I-PFAA formulas involving 21 congeners were identified. Semiquantification was conducted, and the total concentrations of I-PFAAs were 1.9-274.7 μg/L, indicating severe pollution of I-PFAAs in the wastewater. The determined concentrations along with predicted environmental behaviors and toxicities demonstrate that I-PFAAs merit further in-depth investigation. The analytical method including the instrumental analysis and data-processing algorithm can be extended to screening and identification of I-PFAAs in other matrices. Furthermore, the analysis results for the first time provide recognition on the occurrence, distribution features, and pollution status of I-PFAAs in the environment.

Approaches to mixture risk assessment of PFASs in the European population based on human hazard and biomonitoring data

Per- and polyfluoroalkyl substances (PFASs) are a highly persistent, mobile, and bioaccumulative class of chemicals, of which emissions into the environment result in long-lasting contamination with high probability for causing adverse effects to human health and the environment. Within the European Biomonitoring Initiative HBM4EU, samples and data were collected in a harmonized way from human biomonitoring (HBM) studies in Europe to derive current exposure data across a geographic spread. We performed mixture risk assessments based on recent internal exposure data of PFASs in European teenagers generated in the HBM4EU Aligned Studies (dataset with N = 1957, sampling years 2014-2021). Mixture risk assessments were performed based on three hazard-based approaches: the Hazard Index (HI) approach, the sum value approach as used by the European Food Safety Authority (EFSA) and the Relative Potency Factor (RPF) approach. The HI approach resulted in the highest risk estimates, followed by the RPF approach and the sum value approach. The assessments indicate that PFAS exposure may result in a health risk in a considerable fraction of individuals in the HBM4EU teenager study sample, thereby confirming the conclusion drawn in the recent EFSA scientific opinion. This study underlines that HBM data are of added value in assessing the health risks of aggregate and cumulative exposure to PFASs, as such data are able to reflect exposure from different sources and via different routes.

A sensitive and robust method for the simultaneous determination of thirty-three legacy and emerging per- and polyfluoroalkyl substances in human plasma and serum

Legacy and emerging per- and polyfluoroalkyl substances (PFAS) have attracted growing attention due to their potential adverse effects on humans. We developed a method to simultaneously determine thirty-three PFAS (legacy PFAS, precursors, and alternatives) in human plasma and serum using solid phase extraction coupled to ultra-performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS). The method yielded good linearity (>0.995) and excellent limits of detection (LODs) (0.0005~0.012 ng mL^-1 in plasma and 0.002~0.016 ng mL^-1 in serum). The relative recoveries ranged from 80.1 to 116%, with intra- and inter-day precision less than 14.3%. The robustness of this method has been tested continuously for 10 months (coefficients of variation <14.9%). Our method was successfully applied to the PFAS analysis of 42 real human plasma and serum samples collected from women. The proposed method is attractive for the biomonitoring of multi-class PFAS in human health risk assessment and epidemiological studies.

First Evidence of Prenatal Exposure to Emerging Poly- and Perfluoroalkyl Substances Associated with E-Waste Dismantling: Chemical Structure-Based Placental Transfer and Health Risks

Limited information is available about prenatal exposure to per- and polyfluoroalkyl substances (PFAS) in electronic waste (e-waste) recycling sites. In this study, we determined 21 emerging PFAS and 13 legacy PFAS in 94 paired maternal and cord serum samples collected from an e-waste dismantling site in Southern China. We found 6:2 fluorotelomer sulfonate (6:2 FTSA), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), and perfluorooctanephosphonate (PFOPA) as the major emerging PFAS, regardless of matrices, at median concentrations of 2.40, 1.78, and 0.69 ng/mL, respectively, in maternal serum samples, and 2.30, 0.73, and 0.72 ng/mL, respectively, in cord serum samples. Our results provide evidence that e-waste dismantling activities contribute to human exposure to 6:2 FTSA, 6:2 Cl-PFESA, and PFOPA. The trans-placental transfer efficiencies of emerging PFAS (0.42-0.94) were higher than that of perfluorooctanesulfonic acid (0.37) and were structure-dependent. The substitution of fluorine with chlorine or hydrogen and/or hydrophilic functional groups may alter trans-placental transfer efficiencies. Multiple linear regression analysis indicated significant associations between maternal serum concentrations of emerging PFAS and maternal clinical parameters, especially liver function and erythrocyte-related biomarkers. This study provides new insights into prenatal exposure to multiple PFAS in e-waste dismantling areas and the prevalence of emerging PFAS in people living near the sites.

Nontarget Identification of Novel Per- and Polyfluoroalkyl Substances in Cord Blood Samples

Per- and polyfluoroalkyl substances (PFASs) can penetrate the placental barrier and reach embryos through cord blood, probably causing adverse birth outcomes. Therefore, novel PFASs identification in cord blood and their relationships with birth outcomes are essential to evaluate prenatal exposure risk of PFASs. Herein, 16 legacy and 12 novel PFASs were identified in 326 cord blood samples collected from pregnant women in Jinan, Shandong, China. The presence of perfluoropolyether carboxylic acids, hydrogen-substituted polyfluoroetherpropane sulfate, and 3:3 chlorinated polyfluoroalkyl ether alcohol in cord blood was reported for the first time. Two extensive OECD (Organization for Economic Co-operation and Development)-defined PFASs named fipronil sulfone and 2-chloro-6-(trifluoromethyl)pyridine-3-ol were also identified. Quantification results showed that the emerging and OECD-defined PFASs separately accounted for 9.4 and 9.7% of the total quantified PFASs, while the legacy PFOA, PFOS, and PFHxS were still the most abundant PFASs with median concentrations of 2.12, 0.58, and 0.37 ng/mL, respectively. Several PFASs (C₉-C₁₂ PFCAs, C₆-C₈ PFSAs, and 6:2 Cl-PFESA) showed significantly higher levels for older maternities than younger ones. PFHxS levels were positively associated with birth weight and ponderal index (p < 0.05). The results provide comprehensive information on the presence and exposure risks of several novel PFASs during the early life stage.

Identification of novel polyfluoroalkyl substances in surface water runoff from a chemical stockpile fire

In 2018, over 30,000 L of fluorine-free firefighting foam was used to extinguish an industrial warehouse fire of uncharacterized chemical and industrial waste. Contaminated firewater and runoff were discharged to an adjacent freshwater creek in Melbourne, Australia. In this study, we applied nontarget analysis using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) to 15 surface water samples to investigate the presence of legacy, novel and emerging per-and polyfluoroalkyl substances (PFAS). We identified six novel and emerging fluorotelomer-based fluorosurfactants in the Australian environment for the first time, including: fluorotelomer sulfonamido betaines (FTABs or FTSA-PrB), fluorotelomer thioether amido sulfonic acids (FTSASs), and fluorotelomer sulfonyl amido sulfonic acids (FTSAS-So). Legacy PFAS including C₆-C₈ perfluoroalkyl sulfonic acids, C₄-C₁₀ perfluoroalkyl carboxylic acids, and perfluoro-4-ethylcyclohexanesulfonate were also detected in surface water. Of note, we report the first environmental detection of ethyl 2-ethenyl-2-fluoro-1-(trifluoromethyl) cyclopropane-1-carboxylate. Analysis of several Class B certified fluorine-free foam formulations allowed for use in Australia revealed that there was no detectable PFAS. Patterns in the homologue profiles of fluorotelomers detected in surface water are consistent with environments impacted by fluorinated aqueous film-forming foams. These results provide strong evidence that firewater runoff of stockpiled fluorinated firefighting foam was the dominant source of detectable PFAS to the surrounding environment.

Target analysis and suspect screening of per- and polyfluoroalkyl substances in paired samples of maternal serum, umbilical cord serum, and placenta near fluorochemical plants in Fuxin, China

The levels of legacy per- and polyfluoroalkyl substances (PFASs) have been growing in the environmental matrices and blood of residents living around the fluorochemical industrial park (FIP) in Fuxin of China over the past decade. Although some recent studies have reported occurrence of novel PFAS alternatives in biotic and abiotic matrices near fluorochemical facilities worldwide, little is known about novel PFAS congeners in maternal sera, umbilical cord sera, and placentas from the female residents close to the FIP and their related health risks. In this study, 50 paired samples of maternal and cord serum as well as placenta were derived from Fuxin pregnant women at delivery, and 21 target analytes of legacy PFASs in all the samples were analyzed via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), revealing that PFBS, PFBA, and PFOA were the dominant PFAS contaminants observed in the whole samples. Based upon the suspect screening through high-resolution mass spectrometry (HRMS), 49 novel PFASs assigned to 11 classes were further identified in the Fuxin samples, of which, 20 novel congeners in 4 classes were reported in human blood and placentas for the first time. Moreover, the coefficients for mother-placenta transfer (R_m/p), placenta-newborn transfer (R_p/n), and mother-newborn transfer (R_m/n) of legacy PFASs could be calculated with median values of 1.7, 1.1, and 2.0, respectively, and R_m/p, R_p/n, and R_m/n for each novel PFAS identified were also estimated with the median values of 0.9, 1.2, and 0.8 individually. Accordingly, novel PFASs contributed 90% of all the legacy and novel PFASs in maternal sera and even occupied 96% of the whole PFASs in both placentas and cord sera. In addition, significant associations were determined among the neonate birth outcomes and serum concentrations of thyroid hormone, sex hormone, and glucocorticoid, together with the levels of certain legacy and novel PFASs in cord sera.

Comprehensive Exposure Studies of Per- and Polyfluoroalkyl Substances in the General Population: Target, Nontarget Screening, and Toxicity Prediction

Novel per- and polyfluoroalkyl substances (PFASs) in the environment and populations have received extensive attention; however, their distribution and potential toxic effects in the general population remain unclear. Here, a comprehensive study on PFAS screening was carried out in serum samples of 202 individuals from the general population in four cities in China. A total of 165 suspected PFASs were identified using target and nontarget analysis, including seven identified PFAS homolog series, of which 16 PFASs were validated against standards, and seven PFASs [4:2 chlorinated polyfluorinated ether sulfonate (4:2 Cl-PFESA), 7:2 chlorinated polyfluorinated ether sulfonate (7:2 Cl-PFESA), hydrosubstituted perfluoroheptanoate (H-PFHpA), chlorine-substituted perfluorooctanoate (Cl-PFOA), chlorine-substituted perfluorononanate (Cl-PFNA), chlorine-substituted perfluorodecanoate (Cl-PFDA), and perfluorodecanedioic acid (PFLDCA n = 8)] were reported for the first time in human serum. The Tox21-GCN model (a graph convolutional neural network model based on the Tox21 database) was established to predict the toxicity of the discovered PFASs, revealing that PFASs containing sulfonic acid groups exhibited multiple potential toxic effects, such as estrogenic effects and stress responses. Our study indicated that the general population was exposed to various PFASs, and the toxicity prediction results of individual PFASs suggested potential health risks that could not be ignored.

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

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

Non-target discovery of emerging PFAS homologues in Dagang Oilfield: Multimedia distribution and profiles in crude oil

Per- and polyfluoroalkyl substances (PFASs) are applied in oil exploitation activity. In this study, non-target and suspect target analyses with high-resolution mass spectrometry were used for identification of novel PFASs in the oilfield environment. A total of thirty-seven PFAS homologues belonging to eight classes were identified as level 4 or above, which partly explained the amount of potential unknown PFAS-precursors that were indicated by total oxidisable precursor assay in our previous study. Hydrogen-substituted and ether-substituted homologues were the main identified PFASs, and seven of them were newly reported homologues. C1-C3 perfluoroalkane sulphonic acids (PFSAs) were also for the first time identified in the oilfield. The sediment-water partitioning coefficients of most identified PFAS homologues positively correlate with their predicted octanol-water partitioning coefficients while those of C1-C3 PFSAs may have elevated sediment partitioning potential as also previously observed for ultra-short chain C2-C3 perfluoroalkyl carboxylic acids. The crude oil and sludge samples were further examined with the target and identified PFAS profiles. An annual flux of 10.4 kg/y via oil production was estimated in Dagang Oilfield with 16.6 % not from the target PFASs. This demonstrates that oil exploitation activities can be a significant underlying source of PFASs to the environment.

Aberrant hepatic lipid metabolism associated with gut microbiota dysbiosis triggers hepatotoxicity of novel PFOS alternatives in adult zebrafish

Perfluorooctane sulfonate (PFOS) has been reported to induce hepatotoxicity in wildlife and humans. Novel PFOS alternatives have been widely used following restrictions on PFOS, but little is known about their potential toxicity. Here, the first comprehensive investigation on the chronic hepatotoxicity and underlying molecular mechanisms of PFOS, 6:2Cl-PFESA (F-53B), and sodium p-perfluorous nonenoxybenzene sulfonate (OBS) was carried out on adult zebrafish through a histopathological examination, biochemical measurement, and multi-omics analysis. PFOS and its alternatives caused changes in liver histopathology and liver function indices in the order of F-53B > PFOS > OBS, which was consistent with their concentration in the liver. In silico modeling and transcriptional profiles suggested that the aberrant hepatic lipid metabolism induced by F-53B and PFOS was initiated by the action on peroxisome proliferator-activated receptor γ (PPARγ), which triggered changes in downstream genes transcription and led to an imbalance between lipid synthesis and expenditure. Gut microbiome analysis provided another novel mechanistic perspective that changes in the abundance of Legionella, Ralstonia, Brevundimonas, Alphaproteobacteria, Plesiomonas, and Hyphomicrobium might link to alterations in the PPAR pathway based on their significant correlation. This study provides insight into the molecular mechanisms of hepatotoxicity induced by PFOS and its novel alternatives and highlights the need for concern about their environmental exposure risks.

FindPFΔS: Non-Target Screening for PFAS─Comprehensive Data Mining for MS2 Fragment Mass Differences

The limited availability of analytical reference standards makes non-target screening approaches based on high-resolution mass spectrometry increasingly important for the efficient identification of unknown PFAS (per- and polyfluoroalkyl substances) and their TPs. We developed and optimized a vendor-independent open-source Python-based algorithm (FindPFΔS = FindPolyFluoroDeltas) to search for distinct fragment mass differences in MS/MS raw data (.ms2-files). Optimization with PFAS standards, two pre-characterized paper and soil samples (iterative data-dependent acquisition), revealed Δ(CF₂)_n, ΔHF, ΔC_nH₃F_2n-3, ΔC_nH₂F_2n-4, ΔC_nHF_2n-5, ΔC_nF_2nSO₃, ΔCF₃, and ΔCF₂O as relevant and selective fragment differences depending on applied collision energies. In a PFAS standard mix, 94% (36 of 38 compounds from 10 compound classes) could be found by FindPFΔS. The use of fragment differences was applicable to a wide range of PFAS classes and appears as a promising new approach for PFAS identification. The influence of mass tolerance and intensity threshold on the identification efficiency and on the detection of false positives was systematically evaluated with the use of selected HR-MS²-spectra (20,998) from MassBank. To this end, with the use of FindPFΔS, we could identify different unknown PFAS homologues in the paper extracts. FindPFΔS is freely available as both Python source code on GitHub (https://github.com/JonZwe/FindPFAS) and as an executable windows application (https://doi.org/10.5281/zenodo.6797353) with a graphical user interface on Zenodo.

Exploring the origin of efficient adsorption of poly- and perfluoroalkyl substances in household point-of-use water purifiers: Deep insights from a joint experimental and computational study

Poly- and perfluoroalkyl substances (PFAS) are harmful chemicals to humans and widely detected in water bodies including tap water. PFAS cannot be efficiently removed from water through conventional treatment processes used in full-scale drinking water treatment plants, posing a latent risk to human health via drinking tap water. Here in-field investigations show that the household point-of-use (POU) water purifiers constituted with coconut shell activated carbon can achieve 21%-99% removal for 14 legacy and emerging PFAS in tap water based on the ratio of influent and effluent. Extensive characterizations combine with chemical analyses demonstrate that physical adsorption based on Van der Waals force can remove 23 PFAS from tap water, wherein the hydrophobicity of PFAS is the crucial factor. Density functional theory calculations together with the quantitative structure-activity relationship model confirm that both topological structures as well as hydrophobicity of PFAS and electrostatic interactions between the strong electronegative F atoms and the adsorbent surface are the most critical factors controlling the PFAS adsorption to activated carbon. Overall, our results offer insights into the molecular mechanisms that enable the adsorption of PFAS in POU filters.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in groundwater: current understandings and challenges to overcome

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been frequently detected in groundwater globally. With the phase-out of perfluorooctane sulfonate (PFOS) and perfluorooctanate (PFOA) due to their risk to the ecosystem and human population, various novel PFASs have been used as replacements and detected in groundwater. In order to summarize the current understanding and knowledge gaps on PFASs in groundwater, we reviewed the studies about environmental occurrence, transport, and risk of legacy and novel PFASs in groundwater published from 1999 to 2021. Our review suggests that PFOS and PFOA could still be detected in groundwater due to the long residence time and the retention in the soil-groundwater system. Firefighting training sites, industrial parks, and landfills were commonly hotspots of PFASs in groundwater. More novel PFASs have been detected via nontarget analysis using high-resolution mass spectrometry. Some novel PFASs had concentrations comparable to that of PFOS and PFOA. Both legacy and novel PFASs can pose a risk to human population who rely on contaminated groundwater as drinking water. Transport of PFASs to groundwater is influenced by various factors, i.e., the compound structure, the hydrochemical condition, and terrain. The exchange of PFASs between groundwater and surface water needs to be better characterized. Field monitoring, isotope tracing, nontarget screening, and modeling are useful approaches and should be integrated to get a comprehensive understanding of PFASs sources and behaviors in groundwater.

Rapid quantitative analysis and suspect screening of per-and polyfluorinated alkyl substances (PFASs) in aqueous film-forming foams (AFFFs) and municipal wastewater samples by Nano-ESI-HRMS

A rapid analytical method for per- and polyfluoroalkyl substances (PFASs) combining nano-electrospray ionization and high-resolution mass spectrometry (Nano-ESI-HRMS) was developed and applied to aqueous film-forming foams (AFFFs) and wastewater samples collected from three local wastewater treatment plants (WWTPs). This method exhibited high sensitivity with lower limits of detection (LODs) of 3.2∼36.2 ng/L for 22 target PFAS analytes. In AFFF formulations, Nano-ESI-HRMS enabled the first-time detection of trifluoromethanesulfonic acid (TFMS), perfluoroethyl cyclohexanesulfonate (PFECHS), 6:2 fluorotelomer sulfonyl amido sulfonic acid (6:2 FTSAS-SO2), N-ammoniopropyl perfluoroalkanesulfonamidopropylsulfonate (N-AmP-FASAPS, n = 3-6), ketone-perfluorooctanesulfonic acid (Keto-PFOS), fluorotelomer unsaturated amide sulfonic acid (FTUAmS, n = 7), and 6:2 fluorotelomer amide (6:2 FTAm). Their structures were verified by the tandem MS analysis using collision-induced dissociation. Further, the combination of absolute and semi-quantification results revealed 16 PFASs from 9 PFAS classes as dominant AFFF constituents, accounting for 88.2∼96.5% of the total detected anionic and zwitterionic PFASs, including perfluorinated sulfonic acids (PFSAs, n = 1,4∼8), 6:2 fluorotelomer sulfonates (6:2 FTS), fluorotelomer thioether amido sulfonic acid (FTSAS, n = 6,8), fluorotelomer sulfinyl amido sulfonic acid (FTSAS-SO, n = 6,8), N-AmP-FASAPS (n = 6), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), perfluoroalkylsulfonamido amino carboxylate (PFASAC, n = 6), 2-((perfluorooctyl)thio)acetatic acid (Thio-8:2 FTCA), and 6:2 FTAm. At WWTPs, aerobic and anaerobic biotransformation of PFAS precursors at the aeration tanks and secondary clarifiers were evident by the generation of mid/short-chain perfluoroalkyl acids, such as perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), as well as the emergence of ultrashort trifluoroacetic acid (TFA) and TFMS and several novel fluorotelomer carboxylic acids (FTCAs). Overall, Nano-ESI-HRMS enabled comprehensive PFAS quantitative analysis and suspect screening, applicable for rapid investigation and assessment of PFAS-related exposure and treatment in environmental matrixes. Our results also revealed that AFFFs and municipal wastewaters are two key sources contributing to the prevalent detection of ultrashort-chain PFASs (e.g., TFMS and TFA) in water.

Nontargeted Identification and Temporal Trends of Per- and Polyfluoroalkyl Substances in a Fluorochemical Industrial Zone and Adjacent Taihu Lake

Various per- and polyfluoroalkyl substances (PFASs) remain undiscovered and unexplored in the environment. The goals of this study were to discover new species of PFASs in effluent and surface waters from a fluorochemical industrial zone, and to assess their concentration, distribution, and temporal trends in the adjacent natural environment. In total, 83 emerging PFASs from 14 classes were identified, 22 of which were reported for the first time. Authentic standards were synthesized for 13 per- and polyfluoroalkyl ether carboxylic acids (PFECAs), thereby greatly expanding the scope of PFAS-targeted monitoring. The newly identified compounds accounted for 27%-95% of the total PFAS concentrations. Of note, a novel diether carboxylic acid, 2-[2-(trifluoromethoxy)hexafluoropropoxy]tetrafluoropropanoic acid (C7 HFPO-TA) was detected at an extremely high concentration in the fluorochemical zone effluent (447 000 ng/L) and at a median concentration in the fluorochemical zone surface water (670 ng/L), with detectable levels also found in the natural environment, that is, Wangyu River (23 ng/L) and Taihu Lake (5.6 ng/L). The distinct geographic distribution of C7 HFPO-TA suggests transport from the industrial point source to Taihu Lake via the Wangyu River. The concentration of C7 HFPO-TA in Taihu Lake, along with that of many other emerging PFASs, continued to grow in three sampling campaigns from 2016 to 2021. Considering the environmental persistence and toxicity of structurally similar PFECAs (e.g., HFPO-DA), studies on C7 HFPO-TA are urgently needed.