Novel Perfluoroalkyl Ether Carboxylic Acids (PFECAs) and Sulfonic Acids (PFESAs): Occurrence and Association with Serum Biochemical Parameters in Residents Living Near a Fluorochemical Plant in China

Exploring maternal and developmental toxicity of perfluoroalkyl ether acids PFO4DA and PFO5DoA using hepatic transcriptomics and serum metabolomics

Production of per- and polyfluoroalkyl substances (PFAS) has shifted from long-chain perfluoroalkyl acids to short-chain compounds and those with ether bonds in the carbon chain. Next-generation perfluoroalkylether PFAS include HFPO-DA ("GenX chemicals"), Nafion Byproducts, and the PFOx homologous series that includes perfluoro-3,5,7,9-butaoxadecanoic acid (PFO4DA) and perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). PFO4DA and PFO5DoA have been detected in serum and/or tissues from humans and wildlife proximal to contamination point sources. However, toxicity data are extremely limited, with no in vivo developmental toxicology data. To address these data gaps, pregnant Sprague-Dawley rats were exposed via oral gavage to vehicle, PFO4DA, or PFO5DoA across a series of doses (0.1 to 62.5 mg/kg/day) from gestation day (GD) 18-22. Hepatic transcriptomics were assayed in dams and fetuses, and serum metabolomics in dams. These data were overlaid with serum PFO4DA and PFO5DoA concentrations to perform dose-response modeling. Both dams and fetuses exhibited dose-responsive disruption of hepatic gene expression in response to PFO4DA or PFO5DoA, with fetal expression disrupted at lower doses than dams. Several differentially expressed genes were upregulated by every dose of PFO5DoA in both maternal and fetal samples, including genes encoding enzymes that hydrolyze acyl-coA to free fatty acids. Maternal serum metabolomics revealed PFO4DA exposure did not induce significant changes at any tested dose, whereas PFO5DoA exposure resulted in dose-dependent differential metabolite abundance for 149 unique metabolites. Multi-omics pathway analyses of integrated maternal liver transcriptomics and serum metabolomics revealed significant convergent changes as low as 3 mg/kg/d PFO4DA and 0.3 mg/kg/d PFO5DoA exposure. Overall, transcriptomic and metabolomic effects of PFO4DA and PFO5DoA appear consistent with other carboxylic acid PFAS, with primary changes related to lipid metabolism, bile acids, cholesterol, and cellular stress. Importantly, PFO5DoA exposure more potently induced changes in maternal and fetal hepatic gene expression and maternal circulating metabolites, despite high structural similarity. Further, we report in vitro PPARα and PPARγ receptor activation for both compounds as putative molecular mechanisms. This work demonstrates the potential developmental toxicity of alternative moiety perfluoroethers and highlights the developing liver as particularly vulnerable to transcriptomic disruption. Synopsis: Developmental exposure to fluoroether carboxylic acids PFO4DA and PFO5DoA result in differential impacts on hepatic transcriptome in dams and offspring and circulating metabolome in dams, with PFO5DoA exhibiting higher potency than PFO4DA.

Disruption of zebrafish sex differentiation by emerging contaminants hexafluoropropylene oxides at environmental concentrations via antagonizing androgen receptor pathways

As alternatives of perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimeric acid (HFPO-DA) and trimeric acid (HFPO-TA) have been detected increasingly in environmental media and even humans. They have been shown to exhibit reproductive toxicity to model species, but their effects on human remain unclear due to the knowledge gap in their mode of action. Herein, (anti-)androgenic effects of the two HFPOs and PFOA were investigated and underlying toxicological mechanism was explored by combining zebrafish test, cell assay and molecular docking simulation. Exposure of juvenile zebrafish to the chemicals during sex differentiation promoted feminization, with HFPO-TA acting at an environmental concentration of 1 μg/L. The chemicals inhibited proliferation of human prostate cells and transcriptional activity of human and zebrafish androgen receptors (AR), with HFPO-TA displaying the strongest potency. Molecular docking revealed that the chemicals bind to AR in a conformation similar to a known AR antagonist. Combined in vivo, in vitro and in silico results demonstrated that the chemicals disrupted sex differentiation likely by antagonizing AR-mediated pathways, and provided more evidence that HFPO-TA is not a safe alternative to PFOA.

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Polymers are the main building blocks of plastic, with the annual global production volume of fossil carbon-based polymers reaching over 457 million metric tons in 2019 and this figure is anticipated to triple by 2060. There is potential for environmental harm and adverse human health impacts associated with plastic, its constituent polymers and the chemicals therein, at all stages of the plastic life cycle, from extraction of raw materials, production and manufacturing, consumption, through to ultimate disposal and waste management. While there have been considerable research and policy efforts in identifying and mitigating the impacts associated with problematic plastic products such as single-use plastics and hazardous chemicals in plastics, with national and/or international regulations to phase out their use, plastic polymers are often overlooked. In this review, the polymer dimension of the current knowledge on environmental release, human exposure and health impacts of plastic is discussed across the plastic life cycle, including chemicals used in production and additives commonly used to achieve the properties needed for applications for which the polymers are generally used. This review focuses on polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene, four common plastic polymers made from the hazardous monomers, bisphenol, styrene, vinyl chloride and 1,3-butadiene, respectively. Potential alternative polymers, chemicals, and products are considered. Our findings emphasise the need for a whole system approach to be undertaken for effective regulation of plastics whereby the impacts of plastics are assessed with respect to their constituent polymers, chemicals, and applications and across their entire life cycle.

Persistent metabolic toxicities following developmental exposure to hexafluoropropylene oxide trimer acid (HFPO-TA): Roles of peroxisome proliferator activated receptor gamma

BACKGROUND

Hexafluoropropylene oxide trimer acid (HFPO-TA), a perfluorooctanoic acid (PFOA) substitute, exhibited strong affinity and capability to activate peroxisome proliferator activated receptor gamma (PPARγ), a lipid metabolism regulator, suggesting potential to induce metabolic toxicities.

METHODS

Fertile chicken eggs were exposed to 0, 0.5, 1 or 2 mg/kg (egg weight) HFPO-TA and incubated until hatch. Serum from 0- and 3- month-old chickens were subjected to liquid chromatography ultra-high resolution mass spectrometry for HFPO-TA concentration, while liver, pancreas and adipose tissue samples were collected for histopathological assessments. In ovo PPARγ reporter and silencing system were established with lentivirus microinjection. qRT-PCR and immunohistochemistry were utilized to evaluate the expression levels of PPARγ downstream genes.

RESULTS

In 3-month-old animals developmentally exposed to HFPO-TA, adipose tissue hyperplasia, hepatic steatosis, pancreas islet hypertrophy and elevated serum free fatty acid / insulin levels were observed. Results of reporter assay and qRT-PCR indicated HFPO-TA-mediated PPARγ transactivation in chicken embryo. Silencing of PPARγ alleviated HFPO-TA-induced changes, while PPARγ agonist rosiglitazone mimicked HFPO-TA-induced effects. qRT-PCR and immunohistochemistry revealed that FASN and GPD1 were upregulated following developmental exposure to HFPO-TA in 3-month-old animals.

CONCLUSIONS

Developmental exposure to HFPO-TA induced persistent metabolic toxicities in chickens, in which PPARγ played a central role.

A review of sample collection and analytical methods for detecting per- and polyfluoroalkyl substances in indoor and outdoor air

Per- and polyfluoroalkyl substances (PFAS) are a unique class of chemicals synthesized to aid in industrial processes, fire-fighting products, and to benefit consumer products such as clothing, cosmetics, textiles, carpets, and coatings. The widespread use of PFAS and their strong carbon-fluorine bonds has led to their ubiquitous presence throughout the world. Airborne transport of PFAS throughout the atmosphere has also contributed to environmental pollution. Due to the potential environmental and human exposure concerns of some PFAS, research has extensively focused on water, soil, and organismal detection, but the presence of PFAS in the air has become an area of growing concern. Methods to measure polar PFAS in various matrices have been established, while the investigation of polar and nonpolar PFAS in air is still in its early development. This literature review aims to present the last two decades of research characterizing PFAS in outdoor and indoor air, focusing on active and passive air sampling and analytical methods. The PFAS classes targeted and detected in air samples include fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamides (FASAs), perfluoroalkane sulfonamido ethanols (FASEs), perfluorinated carboxylic acids (PFCAs), and perfluorinated sulfonic acids (PFSAs). Although the manufacturing of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) has been largely phased out, these two PFAS are still often detected in air samples. Additionally, recent estimates indicate that there are thousands of PFAS that are likely present in the air that are not currently monitored in air methods. Advances in air sampling methods are needed to fully characterize the atmospheric transport of PFAS.

Prenatal exposure to poly/perfluoroalkyl substances and risk for congenital heart disease in offspring

Congenital heart disease (CHD) is the most prevalent congenital malformation worldwide, and the association between per- and polyfluoroalkyl substances (PFASs) exposure and CHD in population has only received limited study. Therefore, we conducted a multicenter case-control study to explore the associations between prenatal exposure to individual PFASs, and also a PFAS mixture, and CHD risk, including 185 CHDs and 247 controls in China from 2016 to 2021. Thirteen PFASs in maternal plasma were quantified using liquid chromatography-tandem mass spectrometry. Logistic regression and two multipollutant models (Bayesian kernel machine regression [BKMR] and quantile g-computation [qgcomp]) were used to assess the potential associations between any individual PFAS, and also a PFAS mixture, and CHD risk. After adjusting for potential confounders, logistic regression indicated significant associations between elevated levels of perfluorononanoic acid (odds ratio [OR]= 1.30, 95% confidence intervals [CI]: 1.07-1.58), perfluorodecanoic acid (OR=2.07, 95%CI: 1.32-3.26), and perfluoroundecanoic acid (OR=2.86, 95%CI:1.45-5.65) and CHD risk. The BKMR model and qgcomp approach identified that a significant positive association between the PFAS mixture and risk for CHD. These findings provide essential evidence that there is indeed a health crisis associated with PFASs and that it is linked to CHD.

Hexafluoropropylene oxide trimer acid, a perfluorooctanoic acid alternative, induces cardiovascular toxicity in zebrafish embryos

As an increasingly used alternative to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been widely detected in global water environments. However, little is known regarding its toxic effects on cardiovascular development. Here, zebrafish embryos were treated with egg water containing 0, 60, 120, or 240 mg/L HFPO-TA. Results showed that HFPO-TA treatment led to a significant reduction in both larval survival percentage and heart rate. Furthermore, HFPO-TA exposure caused severe pericardial edema and elongation of the sinus venous to bulbus arteriosus distance (SV-BA) in Tg (myl7: GFP) transgenic larvae, disrupting the expression of genes involved in heart development and thus causing abnormal heart looping. Obvious sprouting angiogenesis was observed in the 120 and 240 mg/L exposed Tg (fli: GFP) transgenic larvae. HFPO-TA treatment also impacted the mRNA levels of genes involved in the vascular endothelial growth factor (VEGF) pathway and embryonic vascular development. HFPO-TA exposure significantly decreased erythrocyte number in Tg (gata1: DsRed) transgenic embryos and influenced gene expression associated with the heme metabolism pathway. HFPO-TA also induced oxidative stress and altered the transcriptional levels of genes related to cell cycle and apoptosis, inhibiting cell proliferation while promoting apoptosis. Therefore, HFPO-TA exposure may induce abnormal development of the cardiovascular and hematopoietic systems in zebrafish embryos, suggesting it may not be a suitable or safe alternative for PFOA.

Environmental occurrence, bioaccumulation and human risks of emerging fluoroalkylether substances: Insight into security of alternatives

Per- and polyfluoroalkyl substances (PFASs) are widely used due to their unique structure and excellent performance, while also posing threats on ecosystem, especially long-chain perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). As the control of conventional PFASs, fluoroalkylether substances (ether-PFASs) as alternatives are constantly emerging. Subsequently, the three representative ether-PFASs, chlorinated polyfluoroalkyl ether sulfonic acid (F-53B), hexafluoropropylene oxide-dimer acid (HFPO-DA), and 4,8-Dioxa-3H-perfluorononanoicacid (ADONA) are discovered and have received more attention in the environment and ecosystem. But their security is now also being challenged. This review systematically assesses their security from six dimensions including environmental occurrence in water, soil and atmosphere, as well as bioaccumulation and risk in plants, animals and humans. High substitution level is observed for F-53B, whether in environment or living things. Like PFOS or even more extreme, F-53B exhibits high biomagnification ability, transmission efficiency from maternal to infant, and various biological toxicity effects. HFPO-DA still has a relatively low substitution level for PFOA, but its use has emerged in Europe. Although it is less detected in human bodies and has a higher metabolic rate than PFOA, the strong migration ability of HFPO-DA in plants may pose dietary safety concerns for humans. Research on ADONA is limited, and currently, it is detected in Germany frequently while remaining at trace levels globally. Evidently, F-53B has shown increasing risk both in occurrence and toxicity compared to PFOS, and HFPO-DA is relatively safe based on available data. There are still knowledge gaps on security of alternatives that need to be addressed.

Single-cell RNA sequencing reveals the heterogeneity of hepatic non-parenchymal cell responses to chronic PFO5DoDA exposure in male mice

Perfluoroalkyl ether carboxylic acids (PFECA) have emerged as novel alternatives to legacy per- and polyfluoroalkyl substances (PFAS). Existing research has revealed hepatoxicity induced by various PFAS, including PFECA. However, these studies have primarily focused on overall changes in whole liver tissue, particularly in hepatocytes, with the impact of PFAS on diverse liver non-parenchymal cells (NPCs) still inadequately understood. In the present study, we examined the heterogeneous responses of hepatic NPCs following exposure to perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoDA), a type of PFECA, by administering PFO5DoDA (5 μg/L)-contaminated water to male mice for one year. Single-cell RNA sequencing (scRNA-seq) of 15 008 cells from the liver identified 10 distinct NPC populations. Notably, although relative liver weight remained largely unchanged following exposure to 5 μg/L PFO5DoDA, there was an observed increase in proliferating cells, indicating that proliferating NPCs may contribute to the hepatomegaly frequently noted in PFAS-exposed livers. There was also a considerable alteration in the composition of hepatic NPCs. Specifically, the total number of B cells decreased substantially, while many other cells, such as monocytes and macrophages, increased after PFO5DoDA exposure. In addition, interactions among the hepatic NPC populations changed variously after PFO5DoDA exposure. The findings emphasize the heterogeneity in the responses of hepatic NPCs to PFO5DoDA exposure. Taken together, the changes in immune cell populations and their intercellular interactions suggest that PFO5DoDA disrupts immune homeostasis in the liver. These findings offer new insights into the cellular mechanisms of PFAS-induced liver damage.

The association between per-/polyfluoroalkyl substances in serum and thyroid function parameters: A cross-sectional study on teenagers living near a Chinese fluorochemical industrial plant

Thyroid hormones (THs) play an important role in a wide range of crucial biological functions related to growth and development, and thyroid antibodies (TAs) can influence the biosynthesis of THs. Epidemiological studies have indicated that per- and polyfluoroalkyl substances (PFAS) could induce thyroid disruption, but studies on teenagers living in areas with high PFAS exposure are limited. This cross-sectional study focused on 836 teenagers (11- 15 years) living near a Chinese fluorochemical industrial plant. Decreased levels of free thyroxine (FT4, ﹤9.6 pmol/L, abnormal rate = 19.0 %) and elevated levels of free triiodothyronine (FT3, ﹥6.15 pmol/L, abnormal rate = 29.8 %) were observed. Correlations of serum PFAS concentrations and TAs/THs were analyzed. Increased PFOA was identified as a risk factor of decreased FT4 by using unadjusted (OR: 11.346; 95 % CI: 6.029, 21.352, p < 0.001) and adjusted (OR: 12.566; 95 % CI: 6.549, 24.115, p < 0.001) logistic regression models. In addition, significantly negative correlations were found between log10 transformed PFOA and FT4 levels using linear (unadjusted: β = -1.543, 95 % CI: -1.937, -1.148, p < 0.001; adjusted: β = -1.534, 95 % CI: -1.930, -1.137, p < 0.001) and BKMR models. For abnormal FT3, a significantly positive association between PFHxS and FT3 levels was observed in a regression model (unadjusted: β = -0.903, 95 % CI: -1.212, -0.595, p < 0.001; adjusted: β = -0.894, 95 % CI: -1.204, -0.583, p < 0.001), and PFHxS was identified as a risk factor (unadjusted: OR: 4.387; 95 % CI: 2.619, 7.346, p < 0.001; adjusted: OR: 4.527; 95 % CI: 2.665, 7.688, p < 0.001). Sensitivity analyses confirmed the robustness of the above results. This study reported the elevated PFAS exposure and thyroid function of teenagers living near a fluorochemical industrial plant from China.

Oxidative Transformation of Nafion-Related Fluorinated Ether Sulfonates: Comparison with Legacy PFAS Structures and Opportunities of Acidic Persulfate Digestion for PFAS Precursor Analysis

The total oxidizable precursor (TOP) assay has been extensively used for detecting PFAS pollutants that do not have analytical standards. It uses hydroxyl radicals (HO•) from the heat activation of persulfate under alkaline pH to convert H-containing precursors to perfluoroalkyl carboxylates (PFCAs) for target analysis. However, the current TOP assay oxidation method does not apply to emerging PFAS because (i) many structures do not contain C-H bonds for HO• attack and (ii) the transformation products are not necessarily PFCAs. In this study, we explored the use of classic acidic persulfate digestion, which generates sulfate radicals (SO4-•), to extend the capability of the TOP assay. We examined the oxidation of Nafion-related ether sulfonates that contain C-H or -COO-, characterized the oxidation products, and quantified the F atom balance. The SO4-• oxidation greatly expanded the scope of oxidizable precursors. The transformation was initiated by decarboxylation, followed by various spontaneous steps, such as HF elimination and ester hydrolysis. We further compared the oxidation of legacy fluorotelomers using SO4-• versus HO•. The results suggest novel product distribution patterns, depending on the functional group and oxidant dose. The general trends and strategies were also validated by analyzing a mixture of 100000- or 10000-fold diluted aqueous film-forming foam (containing various fluorotelomer surfactants and organics) and a spiked Nafion precursor. Therefore, (1) the combined use of SO4-• and HO• oxidation, (2) the expanded list of standard chemicals, and (3) further elucidation of SO4-• oxidation mechanisms will provide more critical information to probe emerging PFAS pollutants.

An exposome atlas of serum reveals the risk of chronic diseases in the Chinese population

Although adverse environmental exposures are considered a major cause of chronic diseases, current studies provide limited information on real-world chemical exposures and related risks. For this study, we collected serum samples from 5696 healthy people and patients, including those with 12 chronic diseases, in China and completed serum biomonitoring including 267 chemicals via gas and liquid chromatography-tandem mass spectrometry. Seventy-four highly frequently detected exposures were used for exposure characterization and risk analysis. The results show that region is the most critical factor influencing human exposure levels, followed by age. Organochlorine pesticides and perfluoroalkyl substances are associated with multiple chronic diseases, and some of them exceed safe ranges. Multi-exposure models reveal significant risk effects of exposure on hyperlipidemia, metabolic syndrome and hyperuricemia. Overall, this study provides a comprehensive human serum exposome atlas and disease risk information, which can guide subsequent in-depth cause-and-effect studies between environmental exposures and human health.

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

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

Adverse effects of gestational exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) homologs on maternal, fetal, and placental health in mice

In an effort to identify and develop potential alternatives for perfluorooctanoic acid (PFOA), PFDMO2HpA and PFDMO2OA have been engineered by reducing the -CF2 content in the molecular structure of hexafluoropropylene oxide trimer acid (HFPO-TA). Yet, despite their subsequent presence in environmental samples, there is a paucity of information regarding their toxicity, particularly on pregnancy. Here, pregnant CD-1 mice were exposed to PFDMO2HpA (0, 0.04, 0.16, 0.63, 2.5, or 10 mg/kg/day) or PFDMO2OA (0, 0.01, 0.04, 0.16, 0.63, or 2.5 mg/kg/day) via oral gavage from gestational days 2 (GD2) to 12 or 18 to evaluate the detrimental effects on dams and embryo-placenta units. Both two chemicals can transfer across the placenta, with a higher transfer ratio in late-pregnancy (GD18) than in mid-pregnancy (GD12), and PFDMO2OA being transferred at a higher rate than PFDMO2HpA. PFDMO2HpA/PFDMO2OA exposure caused maternal hepatotoxicity and fetal hepatomegaly, showing the lowest no-observed-adverse-effect level among all observed endpoints, which were used for calculating their reference dose (13.33 ng/kg/day). In the 2.5 and 10 mg/kg/day PFDMO2HpA groups as well as 2.5 mg/kg/day PFDMO2OA group at GD18, besides the abnormally high abortion rates exceeding 5 %, survival fetal weight was notably reduced (2.33 %, 6.44 %, and 5.59 % decrease relative to corresponding controls, respectively). Concurrently, placentas exhibited significant enlargement following PFDMO2HpA or PFDMO2OA exposure at doses of 0.63 mg/kg/day or higher, resulting in diminished placental efficiency. The deleterious effects of two chemicals on dams, fetuses, and placentas were stronger than that of PFOA or HFPO-DA, suggesting that neither PFDMO2HpA nor PFDMO2OA is suitable PFOA alternative. Bioinformatics analyses revealed significant alterations in the expression of genes involved in inflammation and immunity in the placenta upon exposure to 10 mg/kg/day PFDMO2HpA and 2.5 mg/kg/day PFDMO2OA at GD18, potentially elucidating mechanism behind the observed decrease in placental efficiency and increase in abortion rates after exposure.

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

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

Maternal and Neonatal Effects of Maternal Oral Exposure to Perfluoro-2-methoxyacetic Acid (PFMOAA) during Pregnancy and Early Lactation in the Sprague-Dawley Rat

Perfluoro-2-methoxyacetic acid (PFMOAA) is a short-chain perfluoroalkyl ether carboxylic acid that has been detected at high concentrations (∼10 μg/L) in drinking water in eastern North Carolina, USA, and in human serum and breastmilk in China. Despite documented human exposure there are almost no toxicity data available to inform risk assessment of PFMOAA. Here we exposed pregnant Sprague-Dawley rats to a range of PFMOAA doses (10-450 mg/kg/d) via oral gavage from gestation day (GD) 8 to postnatal day (PND) 2 and compared results to those we previously reported for perfluorooctanoic acid (PFOA) and hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX). Newborn pups displayed reduced birthweight (≥30 mg/kg), depleted liver glycogen concentrations (all doses), hypoglycemia (≥125 mg/kg), and numerous significantly altered genes in the liver associated with fatty acid and glucose metabolism similar to gene changes produced by HFPO-DA. Pup survival was significantly reduced at ≥125 mg/kg, and at necropsy on PND2 both maternal and neonatal animals displayed increased liver weights, increased serum aspartate aminotransferase (AST), and reduced serum thyroid hormones at all doses (≥10 mg/kg). Pups also displayed highly elevated serum cholesterol at all doses. PFMOAA concentrations in serum and liver increased with maternal oral dose in both maternal and F1 animals and were similar to those we reported for PFOA but considerably higher than HFPO-DA. We calculated 10% effect levels (ED10 or EC10) and relative potency factors (RPF; PFOA = index chemical) among the three compounds based on maternal oral dose and maternal serum concentration (μM). Reduced pup liver glycogen, increased liver weights and reduced thyroid hormone levels (maternal and pup) were the most sensitive end points modeled. PFMOAA was ∼3-7-fold less potent than PFOA for most end points based on maternal serum RPFs, but slightly more potent for increased maternal and pup liver weights. PFMOAA is a maternal and developmental toxicant in the rat producing a constellation of adverse effects similar to PFOA and HFPO-DA.

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.

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

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

Binding interaction of environmental DNA with typical emerging perfluoroalkyl acids and its impact on bioavailability

As the replacement compounds of perfluoroalkyl acids (PFAAs), emerging PFAAs generally exhibit equal or more hazardous toxicity than legacy PFAAs. Numerous DNA as environmental organic matters coexists with emerging PFAAs, but their interactions and the resulting interaction impacts on the bioavailability of emerging PFAAs remain insufficiently understood. Here, we studied the binding strength and mechanism between DNA and emerging PFAAs (perfluorobutyric acid, perfluorobutylsulfonic acid, and hexafluoropropylene oxide dimer acid) using perfluorooctanoic acid as the control, and further investigated the impacts of DNA binding on the bioavailability of the emerging PFAAs. Isothermal titration calorimetry and quantum chemical calculation found that the emerging PFAAs could bind with DNA bases (main thymine) by van der Waals force and halogen-bond, showing the binding affinities in the range of 7.87 × 104 to L/mol to 6.54 × 106 L/mol. The PFAAs-DNA binding significantly decreased the bioavailability of the PFAAs in both seedlings and plants of pakchoi (Brassica chinensis L.), with little differences in bioavailability change extent among PFAAs. The findings highlight the universality and similarity of the DNA binding effects on PFAAs bioavailability, which can be the natural detoxification mechanism for response to the PFAAs pollution.

Per- and polyfluoroalkyl ether acids in well water and blood serum from private well users residing by a fluorochemical facility near Fayetteville, North Carolina

BACKGROUND

A fluorochemical facility near Fayetteville, North Carolina, emitted per- and polyfluoroalkyl ether acids (PFEAs), a subgroup of per- and polyfluoroalkyl substances (PFAS), to air.

OBJECTIVE

Analyze PFAS in private wells near the facility and in blood from well users to assess relationships between PFEA levels in water and serum.

METHODS

In 2019, we recruited private well users into the GenX Exposure Study and collected well water and blood samples. We targeted 26 PFAS (11 PFEAs) in water and 27 PFAS (9 PFEAs) in serum using liquid chromatography-mass spectrometry. We used regression modeling to explore relationships between water and serum PFAS. For the only PFEA detected frequently in water and serum, Nafion byproduct 2, we used generalized estimating equation (GEE) models to assess well water exposure metrics and then adjusted for covariates that may influence Nafion byproduct 2 serum concentrations.

RESULTS

We enrolled 153 participants ages 6 and older (median = 56 years) using 84 private wells. Most wells (74%) had ≥6 detectable PFEAs; median ∑PFEAs was 842 ng/L (interquartile range = 197-1760 ng/L). Low molecular weight PFEAs (PMPA, HFPO-DA [GenX], PEPA, PFO2HxA) were frequently detected in well water, had the highest median concentrations, but were not detectable in serum. Nafion byproduct 2 was detected in 73% of wells (median = 14 ng/L) and 56% of serum samples (median = 0.2 ng/mL). Cumulative dose (well concentration × duration at address) was positively associated with Nafion byproduct 2 serum levels and explained the most variability (10%). In the adjusted model, cumulative dose was associated with higher Nafion byproduct 2 serum levels while time outside the home was associated with lower levels.

IMPACT

PFAS are a large class of synthetic, fluorinated chemicals. Fluorochemical facilities are important sources of environmental PFAS contamination globally. The fluorochemical industry is producing derivatives of perfluoroalkyl acids, including per- and polyfluoroalkyl ether acids (PFEAs). PFEAs have been detected in various environmental samples but information on PFEA-exposed populations is limited. While serum biomonitoring is often used for PFAS exposure assessment, serum biomarkers were not good measures of long-term exposure to low molecular weight PFEAs in a private well community. Environmental measurements and other approaches besides serum monitoring will be needed to better characterize PFEA exposure.

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

Comprehensive Assessment of Exposure Pathways for Perfluoroalkyl Ether Carboxylic Acids (PFECAs) in Residents Near a Fluorochemical Industrial Park: The Unanticipated Role of Cereal Consumption

With the replacement of perfluorooctanoic acid (PFOA) with perfluorinated ether carboxylic acids (PFECAs), residents living near fluorochemical industrial parks (FIPs) are exposed to various novel PFECAs. Despite expectations of low accumulation, short-chain PFECAs, such as perfluoro-2-methoxyacetic acid (PFMOAA), previously displayed a considerably high body burden, although the main exposure routes and health risks remain uncertain. Here, we explored the distribution of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in diverse environmental media surrounding a FIP in Shandong Province, China. PFECAs were found at elevated concentrations in all tested matrices, including vegetables, cereals, air, and dust. Among residents, 99.3% of the ∑36PFAS exposure, with a 43.9% contribution from PFECAs, was due to gastrointestinal uptake. Dermal and respiratory exposures were negligible at 0.1 and 0.6%, respectively. The estimated daily intake (EDI) of PFMOAA reached 114.0 ng/kg body weight (bw)/day, ranking first among all detected PFECAs. Cereals emerged as the dominant contributor to PFMOAA body burden, representing over 80% of the overall EDI. The median EDI of hexafluoropropylene oxide dimer acid (HFPO-DA) was 17.9 ng/kg bw/day, markedly higher than the USEPA reference doses (3.0 ng/kg bw/day). The absence of established threshold values for other PFECAs constrains a comprehensive risk assessment.

Legacy and emerging per- and polyfluoroalkyl substances suppress the neutrophil respiratory burst

Per- and polyfluoroalkyl substances (PFASs) are used in a multitude of processes and products, including nonstick coatings, food wrappers, and fire-fighting foams. These chemicals are environmentally-persistent, ubiquitous, and can be detected in the serum of 98% of Americans. Despite evidence that PFASs alter adaptive immunity, few studies have investigated their effects on innate immunity. The report here presents results of studies that investigated the impact of nine environmentally-relevant PFASs [e.g. perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid potassium salt (PFOS-K), perfluorononanoic acid (PFNA), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), 7H-perfluoro-4-methyl-3,6-dioxa-octane sulfonic acid (Nafion byproduct 2), and perfluoromethoxyacetic acid sodium salt (PFMOAA-Na)] on one component of the innate immune response, the neutrophil respiratory burst. The respiratory burst is a key innate immune process by which microbicidal reactive oxygen species (ROS) are rapidly induced by neutrophils in response to pathogens; defects in the respiratory burst can increase susceptibility to infection. The study here utilized larval zebrafish, a human neutrophil-like cell line, and primary human neutrophils to ascertain whether PFAS exposure inhibits ROS production in the respiratory burst. It was observed that exposure to PFHxA and GenX suppresses the respiratory burst in zebrafish larvae and a human neutrophil-like cell line. GenX also suppressed the respiratory burst in primary human neutrophils. This report is the first to demonstrate that these PFASs suppress neutrophil function and support the utility of employing zebrafish larvae and a human cell line as screening tools to identify chemicals that may suppress human immune function.

Activation of estrogen-related receptor: An alternative mechanism of hexafluoropropylene oxide homologs estrogenic effects

Perfluorooctanoic acid (PFOA) alternatives such as hexafluoropropylene oxide homologs (HFPOs) cause concern due to increased occurrence in the environment as well as potential bioaccumulation and toxicity. HFPOs have been demonstrated to activate the estrogen receptor (ER) pathway. The ER pathway is homologous and connected to the estrogen-related receptor (ERR) pathway, but HFPOs effects on the ERR pathway have not been studied. Hence, we assessed the potential estrogenic effects of HFPOs via ERRγ pathway. In vitro assays revealed that HFPO dimeric, trimeric, and tetrameric acids (HFPO-DA, -TA, and -TeA, respectively), acted as ERRγ agonists, activating the transcription of both human and zebrafish ERRγ at low concentrations, but inhibiting zebrafish ERRγ at high concentrations. We also found that HFPO-TA promoted the human endometrial cancer cells (Ishikawa cells) proliferation via ERRγ/EGF, Cyclin D1 pathway. The HFPO-TA-induced proliferation of Ishikawa cells was inhibited by co-exposure with a specific antagonist of ERRγ, GSK5182. In vivo exposure of female zebrafish to HFPO-TA disturbed sex hormone levels, interfered with the gene expression involved in estrogen synthesis and follicle regulation, and caused histopathological lesions in the ovaries, which were similar to those induced by a known ERRγ agonist GSK4716. Taken together, this study revealed a new mechanism concerning the estrogenic effect of HFPOs via activation of the ERRγ pathway.

Different Life-Stage Exposure to Hexafluoropropylene Oxide Trimer Acid Induces Reproductive Toxicity in Adult Zebrafish (Danio rerio)

As a novel alternative to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been widely used and has caused ubiquitous water pollution. However, its adverse effects on aquatic organisms are still not well known. In the present study, zebrafish at different life stages were exposed to 0, 5, 50, and 100 μg/L of HFPO-TA for 21 days to investigate reproductive toxicity in zebrafish. The results showed that HFPO-TA exposure significantly inhibited growth and induced reproductive toxicity in zebrafish, including a decrease of the condition factor, gonadosomatic index, and the average number of eggs. Histological section observation revealed that percentages of mature oocytes and spermatozoa were reduced, while those of primary oocytes and spermatocytes increased. In addition, exposure to HFPO-TA at three stages induced a significant decrease in the hatching rate, while the heart rate and normal growth rate of F1 offspring were only significantly inhibited for the exposure from fertilization to 21 days postfertilization (dpf). Compared with the exposure from 42 to 63 dpf, the reproductive toxicity induced by HFPO-TA was more significant for the exposure from fertilization to 21 dpf and from 21 to 42 dpf. Expression of the genes for cytochrome P450 A1A, vitellogenin 1, estrogen receptor alpha, and estrogen receptor 2b was significantly up-regulated in most cases after exposure to HFPO-TA, suggesting that HFPO-TA exhibited an estrogen effect similar to PFOA. Therefore, HFPO-TA might disturb the balance of sex steroid hormones and consequently induce reproductive toxicity in zebrafish. Taken together, the results demonstrate that exposure to HFPO-TA at different life stages could induce reproductive toxicity in zebrafish. However, the underlying mechanisms deserve further investigation. Environ Toxicol Chem 2023;42:2490-2500. © 2023 SETAC.

Synthesis, Surface Activity, and Foamability of Two Short-Chain Fluorinated Sulfonate Surfactants with Ether Bonds

Fluorinated surfactants are widely used in many fields because of their excellent surface active properties, but their high stability has caused many environmental problems. With the ban and restriction of classical long-chain fluorinated surfactants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) worldwide, the development and replacement of their alternatives is now a major challenge. How to reduce environmental persistence, bioaccumulation, and biotoxicity while maintaining high surface activity has become an important issue in the development of fluorinated surfactants. Using short-chain fluorinated surfactants is one of the important solutions to resolve the pollution of organic fluorinated compounds. In this article, we synthesized two short-chain fluorinated surfactants with ether bonds. One of them 6:2 FTESNa (2) used the perfluoroalkyl chain (n-C6F13-) and the other C72 FEESNa (4) used the fluoroether segment with six fluorinated carbons and two oxygens (CF3OCF(CF3)CF2OCF(CF3)). The surface activity, foam performance, and wettability of the two molecules were measured. The surface tensions at critical micelle concentration (γcmc) and the critical micelle concentration (cmc) of 2 and 4 were 17.6 mN/m (2.2 g/L) and 20.2 mN/m (4.6 g/L), respectively. Both of them were significantly superior to the surface activity of 6:2 FTSNa (7) which is one of the current alternatives for PFOS. Additionally, the foamability and foam stability of both 2 and 4 were better than that of 7. In the aspect of wettability on PTFE, that of 4 was greater than those of 2 and 7. In summary, this work provided a new choice for alternatives of PFOS and PFOA.

Exposure characteristics of legacy and novel per- and polyfluoroalkyl substances in blood and association with hypertension among low-exposure population

The exposure characteristics of per- and polyfluoroalkyl substances (PFAS) in blood and their associations with hypertension have been well investigated in high-exposure populations, yet limited information is available concerning low-exposure populations. We conducted a cross-sectional study in a low-exposure population in China. A total of 394 females, including 162 with hypertension, were recruited and 30 PFAS were measured in whole blood samples. General linear model, generalized additive model, and logistic model were used to identify the associations with hypertension. Additionally, a Bayesian kernel machine regression model was conducted to test the mixture effects. Fourteen PFAS, including two novel species, 6:2 and 8:2 chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), were detected, among which PFOS predominated with the highest median level of 1.47 ng/mL. The median levels of individual PFAS were, however, below the 25th, and even the 5th percentile of previous reports, except for PFHxA, which was above the 50th percentile (median of 0.10 ng/mL). After adjusting for covariates, PFHxA showed a positive association with hypertension (OR=1.54, 95% CI: 1.25, 1.89), while 6:2 Cl-PFESA showed a negative association (OR=0.73, 95% CI: 0.56, 0.95). PFAS didn't show significant mixture effects. We proposed that PFHxA may contribute to hypertension and 6:2 Cl-PFESA may have a hormesis effect.

Perfluoroundecanoic acid induces DNA damage, reproductive and pathophysiological dysfunctions via oxidative stress in male Swiss mice

Perfluoroundecanoic acid (PFUnA) is an eleven carbon-chain compound that belongs to the perfluoroalkyl carboxylic acid family. It has been detected in the human blood, effluents, and surface/ground waters, but its toxic effects to the DNA and reproductive system remain unclear. This study was aimed at exploring the toxicity of PFUnA on the hepatic DNA, organ-system and reproductive system in orally treated male Swiss mice. In this present study, administration of PFUnA for 28 days with five doses (0.1, 0.3, 05, 0.7 and 1.0 mg kg-1 b.w./d) in male Swiss mice induced significant hepatic DNA damage which was observed using the alkaline comet assay and equally altered hematological and clinical biochemical parameters. In addition to testicular atrophy, sperm count and sperm motility significantly decreased while sperm abnormalities increased after 35 days exposure. Serum LH and FSH levels were remarkably increased while serum testosterone levels were strikingly reduced. Histopathology revealed the liver, kidney, and testis as potential targets of PFUnA toxicity. Increased activities of superoxide dismutase (SOD) and catalase (CAT), as well as levels of glutathione-s-transferase (GST) and reduced glutathione (GSH), with consistent reduction of glutathione peroxidase (GPx) and reduced glutathione (GSH) in the liver and testis induced oxidative stress. In conclusion, PFUnA exhibited both genotoxicity and reproductive toxicity via oxidative stress induction.

6:2 Chlorinated Polyfluoroalkyl Ether Sulfonates Exert Stronger Thyroid Homeostasis Disruptive Effects in Newborns than Perfluorooctanesulfonate: Evidence Based on Bayesian Benchmark Dose Values from a Population Study

Growing toxicologic evidence suggests that emerging perfluoroalkyl substances (PFASs), like chlorinated polyfluoroalkyl ether sulfonate (Cl-PFESA), may be as toxic or more toxic than perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA). However, further investigations are needed in terms of the human health risk assessment. This study examined the effects of emerging and legacy PFAS exposure on newborn thyroid homeostasis and compared the thyroid disruption caused by 6:2 Cl-PFESA and PFOS using a benchmark dose approach. The health effects of mixture and individual exposure were estimated using the partial least-squares (PLS) model and linear regression, respectively. A Bayesian benchmark dose (BMD) analysis determined the BMD value for adverse effect comparison between 6:2 Cl-PFESA and PFOS. The median (interquartile range) concentrations of 6:2 Cl-PFESA (0.573 [0.351-0.872] ng/mL), PFOS (0.674 [0.462-1.007] ng/mL), and PFOA (1.457 [1.034, 2.405] ng/mL) were found to be similar. The PLS model ranked the PFAS variables' importance in projection (VIP) scores as follows: 6:2 Cl-PFESA > PFOS > PFOA. Linear regression showed that 6:2 Cl-PFESA had a positive association with free triiodothyronine (FT3, P = 0.006) and triiodothyronine (T3, P = 0.014), while PFOS had a marginally significant positive association with FT3 alone (P = 0.042). The BMD analysis indicated that the estimated BMD10 for 6:2 Cl-PFESA (1.01 ng/mL) was lower than that for PFOS (1.66 ng/mL) in relation to a 10% increase in FT3. These findings suggest that 6:2 Cl-PFESA, an alternative to PFOS, has a more pronounced impact on newborns' thyroid homeostasis compared to PFOS and other legacy PFASs.

Novel perfluoroalkyl substances (PFAS) discovered in whole blood using automated non-targeted analysis of dried blood spots

A small subset of per- and polyfluoroalkyl substances (PFAS) are routinely screened in human blood. These compounds generally explain <50 % of the total PFAS in human blood. The percentage of known PFAS in human blood has been decreasing as replacement PFAS and more complex PFAS chemistries are introduced to the market. Most of these novel PFAS have not been previously identified. Non-targeted methods are required to characterize this "dark matter" PFAS. Our objective was to apply non-targeted PFAS analysis to human blood to gain an understanding about the sources, concentrations, and toxicity of these compounds. A high-resolution tandem mass spectrometry (HRMS) and software workflow for PFAS characterization in dried blood spots is reported. Dried blood spots are a less invasive collection technique compared to venous blood draws, allowing collection from vulnerable populations. Biorepositories of archived dried blood spots are available internationally from newborns and present opportunities to study prenatal exposure to PFAS. In this study, dried blood spot cards were analyzed using iterative MS/MS by liquid chromatography HRMS. Data processing was conducted using FluoroMatch Suite including a visualizer tool that presents homologous series, retention time vs m/z plots, MS/MS spectra, feature tables, annotations, and fragments for fragment screening. The researcher performing data-processing and annotation was blinded to the fact that standards were spiked in, and was able to annotate 95 % of standards spiked on dried blood spot samples, signifying a low false negative rate using FluoroMatch Suite. A total of 28 PFAS (20 standards and 4 exogenous compounds) were detected across five homologous series with Schymanski Level 2 confidence. Of these 4, 3 were perfluoroalkyl ether carboxylic acids (PFECA), a chemical class of PFAS which is increasingly being detected in environmental and biological matrices but is not currently screened in most targeted analysese. A further 86 potential PFAS were detected using fragment screening. PFAS are extremely persistent and widespread yet remain largely unregulated. Our findings will contribute to an improved an understanding of exposures. Application of these methods in environmental epidemiology studies have the potential to inform policy with regards to PFAS monitoring, regulation, and individual-level mitigation strategies.

Trophic behaviors of PFOA and its alternatives perfluoroalkyl ether carboxylic acids (PFECAs) in a coastal food web

With the increasing restrictions and concerns about legacy poly- and perfluoroalkyl substances (PFAS), the production and usage of alternatives, i.e., perfluoroalkyl ether carboxylic acids (PFECAs), have risen recently. However, there is a knowledge gap regarding the bioaccumulation and trophic behaviors of emerging PFECAs in coastal ecosystems. The bioaccumulation and trophodynamics of perfluorooctanoic acid (PFOA) and its substitutes (PFECAs) were investigated in Laizhou Bay, which is located downstream of a fluorochemical industrial park in China. Hexafluoropropylene oxide trimer acid (HFPO-TrA), perfluoro-2-methoxyacetic acid (PFMOAA) and PFOA constituted the dominant compounds in the ecosystem of Laizhou Bay. PFMOAA was dominant in invertebrates, whereas the long-chain PFECAs preferred to accumulate in fishes. The PFAS concentrations in carnivorous invertebrates were higher than those in filter-feeding species. Considering migration behaviors, the ∑PFAS concentrations followed the order oceanodromous fish < diadromous fish < non-migratory fish. The trophic magnification factors (TMFs) of long-chain PFECAs (HFPO-TrA, HFPO-TeA and PFO5DoA) were >1, suggesting trophic magnification potential, while biodilution for short-chain PFECAs (PFMOAA) was observed. The intake of PFOA in seafood may constitute a great threat to human health. More attention should be given to the impact of emerging hazardous PFAS on organisms for the health of ecosystems and human beings.

Mechanistic Investigations of Thermal Decomposition of Perfluoroalkyl Ether Carboxylic Acids and Short-Chain Perfluoroalkyl Carboxylic Acids

In this study, we investigated the thermal decomposition mechanisms of perfluoroalkyl ether carboxylic acids (PFECAs) and short-chain perfluoroalkyl carboxylic acids (PFCAs) that have been manufactured as replacements for phased-out per- and polyfluoroalkyl substances (PFAS). C-C, C-F, C-O, O-H, and C═C bond dissociation energies were calculated at the M06-2X/Def2-TZVP level of theory. The α-C and carboxyl-C bond dissociation energy of PFECAs declines with increasing chain length and the attachment of an electron-withdrawing trifluoromethyl (-CF3) group to the α-C. Experimental and computational results show that the thermal transformation of hexafluoropropylene oxide dimer acid to trifluoroacetic acid (TFA) occurs due to the preferential cleavage of the C-O ether bond close to the carboxyl group. This pathway produces precursors of perfluoropropionic acid (PFPeA) and TFA and is supplemented by a minor pathway (CF3CF2CF2OCFCF3COOH → CF3CF2CF2· + ·OCFCF3COOH) through which perfluorobutanoic acid (PFBA) is formed. The weakest C-C bond in PFPeA and PFBA is the one connecting the α-C and the β-C. The results support (1) the C-C scission in the perfluorinated backbone as an effective PFCA thermal decomposition mechanism and (2) the thermal recombination of radicals through which intermediates are formed. Additionally, we detected a few novel thermal decomposition products of studied PFAS.

Bile acid metabolism disorder mediates hepatotoxicity of Nafion by-product 2 and perfluorooctane sulfonate in male PPARα-KO mice

Perfluorooctane sulfonate (PFOS) and Nafion by-product 2 (H-PFMO2OSA) induce hepatotoxicity in male mice via activation of the peroxisome proliferator-activated receptor α (PPARα) pathway; however, accumulating evidence suggests that PPARα-independent pathways also play a vital role in hepatotoxicity after exposure to per- and polyfluoroalkyl substances (PFASs). Thus, to assess the hepatotoxicity of PFOS and H-PFMO2OSA more comprehensively, adult male wild-type (WT) and PPARα knockout (PPARα-KO) mice were exposed to PFOS and H-PFMO2OSA (1 or 5 mg/kg/d) for 28 d via oral gavage. Results showed that although elevations in alanine transaminase (ALT) and aspartate aminotransferase (AST) were alleviated in PPARα-KO mice, liver injury, including liver enlargement and necrosis, was still observed after PFOS and H-PFMO2OSA exposure. Liver transcriptome analysis identified fewer differentially expressed genes (DEGs) in the PPARα-KO mice than in the WT mice, but more DEGs associated with the bile acid secretion pathway after PFOS and H-PFMO2OSA treatment. Total bile acid content in the liver was increased in the 1 and 5 mg/kg/d PFOS-exposed and 5 mg/kg/d H-PFMO2OSA-exposed PPARα-KO mice. Furthermore, in PPARα-KO mice, proteins showing changes in transcription and translation levels after PFOS and H-PFMO2OSA exposure were involved in the synthesis, transportation, reabsorption, and excretion of bile acids. Thus, exposure to PFOS and H-PFMO2OSA in male PPARα-KO mice may disturb bile acid metabolism, which is not under the control of PPARα.

Bioaccumulation and risk mitigation of legacy and novel perfluoroalkyl substances in seafood: Insights from trophic transfer and cooking method

Per- and polyfluoroalkyl substances (PFAS) have widespread application in industrial and civil areas due to their unique physical and chemical properties. With the increasingly stringent regulations of legacy PFAS, various novel alternatives have been developed and applied to meet the market demand. Legacy and novel PFAS pose potential threats to the ecological safety of coastal areas, however, little is known about their accumulation and transfer mechanism, especially after cooking treatment. This study investigated the biomagnification and trophic transfer characteristics of PFAS in seafood from the South China Sea, and assessed their health risks after cooking. Fifteen target PFAS were all detected in the samples, of which perfluorobutanoic acid (PFBA) was dominant with concentrations ranging from 0.76 to 4.12 ng/g ww. Trophic magnification factors (TMFs) > 1 were observed for perfluorooctane sulfonate (PFOS) and 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (F-53B), indicating that these compounds experienced trophic magnification in the food web. The effects of different cooking styles on PFAS occurrence were further explored and the results suggested that ΣPFAS concentrations increased in most organisms after baking, while ΣPFAS amounts decreased basically after boiling and frying. Generally, there is a low health risk of exposure to PFAS when cooked seafood is consumed. This work provided quantitative evidence that cooking methods altered PFAS in seafood. Further, suggestions to mitigate the health risks of consuming PFAS-contaminated seafood were provided.

Exposure to per- and polyfluoroalkyl substances in early pregnancy, risk of gestational diabetes mellitus, potential pathways, and influencing factors in pregnant women: A nested case-control study

Although previous studies have reported an association between maternal serum perfluoroalkyl substance (PFAS) exposure and gestational diabetes mellitus (GDM) risk, results have been inconsistent. Few studies have focused on the combined effects of emerging and legacy PFASs on glucose homeostasis while humans are always exposed to multiple PFASs simultaneously. Moreover, the potential pathways by which PFAS exposure induces GDM are unclear. A total of 295 GDM cases and 295 controls were enrolled from a prospective cohort of 2700 pregnant women in Shanghai, China. In total, 16 PFASs were determined in maternal spot serum samples in early pregnancy. We used conditional logistic regression, multiple linear regression, and Bayesian kernel machine regression (BKMR) to examine individual and joint effects of PFAS exposure on GDM risk and oral glucose tolerance test outcomes. The mediating effects of maternal serum biochemical parameters, including thyroid and liver function were further assessed. Maternal perfluorooctanoic acid (PFOA) exposure was associated with an increased risk of GDM (odds ratio (OR) = 1.68; 95% confidence interval (95% CI): 1.10, 2.57), consistent with higher concentrations in GDM cases than controls. Based on mediation analysis, an increase in the free triiodothyronine to free thyroxine ratio partially explained the effect of this association. For continuous glycemic outcomes, positive associations were observed between several PFASs and 1-h and 2-h glucose levels. In BKMR, PFAS mixture exposure showed a positive trend with GDM incidence, although the CIs were wide. These associations were more pronounced among women with normal pre-pregnancy body mass index (BMI). Mixed PFAS congeners may affect glucose homeostasis by increasing 1-h glucose levels, with perfluorononanoic acid found to be a main contributor. Exposure to PFASs was associated with increased risk of GDM and disturbance in glucose homeostasis, especially in normal weight women. The PFAS-associated disruption of maternal thyroid function may alter glucose homeostasis.

Toxicological Mechanisms of Emerging Per-/poly-fluoroalkyl Substances: Focusing on Transcriptional Activity and Gene Expression Disruption

Environmental and human monitoring studies have witnessed increasing occurrence of emerging per-/poly-fluoroalkyl substances (ePFASs) worldwide. Three classes of ePFASs, namely chlorinated polyfluoroalkylether sulfonic acids, hexafluoropropylene oxide homologues and short-chain perfluoroalkyl acids attracted the most attention. It is, therefore, the goal of this review to systematically and critically analyse the toxicity and toxicological mechanisms of these ePFASs based on the papers published between 2017 and 2022. The review summarized the main findings from both in vivo and in vitro studies, covering the hepatotoxicity of ePFASs and their interference with the endocrine system, including reproductive, developmental and thyroid toxicity. It also summarized the changes in gene expression in the hypothalamic-pituitary-thyroid axis and hypothalamic-pituitary-gonad axis of the model organisms after ePFASs exposure. The changes in gene expression in vitro and in vivo provide a clearer understanding of the toxicological mechanisms of ePFASs interference on hormonal levels (i.e., estradiol, testosterone, and thyroid hormones), developmental disturbance (e.g., swim bladder dysfunction) and lipid metabolism disruption (e.g., lipid droplet accumulation and hepatomegaly). In the end, future research directions on the toxicological mechanisms of ePFASs are suggested.

Perfluoroalkyl substances promote breast cancer progression via ERα and GPER mediated PI3K/Akt and MAPK/Erk signaling pathways

Perfluoroalkyl substances (PFASs) are a classic environmental endocrine disruptor with carcinogenic risk. Epidemiological studies have shown that PFASs contamination is associated with breast cancer development, but the mechanism remains largely unknown. This study first obtained complex biological information about PFASs-induced breast cancer through the comparative toxicogenomics database (CTD). The Protein-Protein Interaction (PPI) network, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis were utilized to investigate molecular pathways. The ESR1 and GPER expression levels at different pathological stages and the prognosis of Breast Cancer patients were confirmed using the Cancer Genome Atlas (TCGA) database. Furthermore, we verified this by cellular experiments and the results showed breast cancer cell migration and invasion were promoted by PFOA. Two estrogen receptors (ER), ERα and G protein-coupled estrogen receptor (GPER), mediated the promoting effects of PFOA by activating MAPK/Erk and PI3K/Akt signaling pathways. These pathways were regulated by ERα and GPER in MCF-7 cells or independently by GPER in MDA-MB-231 cells. Overall, our study provides a better overview of the mechanisms associated with PFASs-induced breast cancer development and progression.

Unveiling Distribution of Per- and Polyfluoroalkyl Substances in Matched Placenta-Serum Tetrads: Novel Implications for Birth Outcome Mediated by Placental Vascular Disruption

The placenta is pivotal for fetal development and maternal-fetal transfer of many substances, including per- and polyfluoroalkyl substances (PFASs). However, the intraplacental distribution of PFASs and their effects on placental vascular function remain unclear. In this study, 302 tetrads of matched subchorionic placenta (fetal-side), parabasal placenta (maternal-side), cord serum, and maternal serum samples were collected from Guangzhou, China. Eighteen emerging and legacy PFASs and five placental vascular biomarkers were measured. Results showed that higher levels of perfluorooctanoic (PFOA), perfluorooctane sulfonic acid (PFOS), and chlorinated polyfluorinated ether sulfonic acids (Cl-PFESAs) were detected in subchorionic placenta compared to parabasal placenta. There were significant associations of PFASs in the subchorionic placenta, but not in the serum, with placental vascular biomarkers (up to 32.5%) and lower birth size. Birth weight was negatively associated with PFOA (β: -103.8, 95% CI: -186.3 and -21.32) and 6:2 Cl-PFESA (β: -80.04, 95% CI: -139.5 and -20.61), primarily in subchorionic placenta. Mediation effects of altered placental angiopoietin-2 and vascular endothelial growth factor receptor-2 were evidenced on associations of adverse birth outcomes with intraplacental PFOS and 8:2 Cl-PFESA, explaining 9.5%-32.5% of the total effect. To the best of our knowledge, this study is the first to report on differential intraplacental distribution of PFASs and placental vascular effects mediating adverse birth outcomes and provides novel insights into the placental plate-specific measurement in PFAS-associated health risk assessment.

Determination of in vitro hepatotoxic potencies of a series of perfluoroalkyl substances (PFASs) based on gene expression changes in HepaRG liver cells

Per- and polyfluoroalkyl substances (PFASs) are omnipresent and have been shown to induce a wide range of adverse health effects, including hepatotoxicity, developmental toxicity, and immunotoxicity. The aim of the present work was to assess whether human HepaRG liver cells can be used to obtain insight into differences in hepatotoxic potencies of a series of PFASs. Therefore, the effects of 18 PFASs on cellular triglyceride accumulation (AdipoRed assay) and gene expression (DNA microarray for PFOS and RT-qPCR for all 18 PFASs) were studied in HepaRG cells. BMDExpress analysis of the PFOS microarray data indicated that various cellular processes were affected at the gene expression level. From these data, ten genes were selected to assess the concentration-effect relationship of all 18 PFASs using RT-qPCR analysis. The AdipoRed data and the RT-qPCR data were used for the derivation of in vitro relative potencies using PROAST analysis. In vitro relative potency factors (RPFs) could be obtained for 8 PFASs (including index chemical PFOA) based on the AdipoRed data, whereas for the selected genes, in vitro RPFs could be obtained for 11-18 PFASs (including index chemical PFOA). For the readout OAT5 expression, in vitro RPFs were obtained for all PFASs. In vitro RPFs were found to correlate in general well with each other (Spearman correlation) except for the PPAR target genes ANGPTL4 and PDK4. Comparison of in vitro RPFs with RPFs obtained from in vivo studies in rats indicate that best correlations (Spearman correlation) were obtained for in vitro RPFs based on OAT5 and CXCL10 expression changes and external in vivo RPFs. HFPO-TA was found to be the most potent PFAS tested, being around tenfold more potent than PFOA. Altogether, it may be concluded that the HepaRG model may provide relevant data to provide insight into which PFASs are relevant regarding their hepatotoxic effects and that it can be applied as a screening tool to prioritize other PFASs for further hazard and risk assessment.

A review of cardiovascular effects and underlying mechanisms of legacy and emerging per- and polyfluoroalkyl substances (PFAS)

Cardiovascular disease (CVD) poses the leading threats to human health and life, and their occurrence and severity are associated with exposure to environmental pollutants. Per- and polyfluoroalkyl substances (PFAS), a group of widely used industrial chemicals, are characterized by persistence, long-distance migration, bioaccumulation, and toxicity. Some PFAS, particularly perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS), have been banned, leaving only legacy exposure to the environment and human body, while a number of novel PFAS alternatives have emerged and raised concerns, such as polyfluoroalkyl ether sulfonic and carboxylic acid (PFESA and PFECA) and sodium p-perfluorous nonenoxybenzene sulfonate (OBS). Overall, this review systematically elucidated the adverse cardiovascular (CV) effects of legacy and emerging PFAS, emphasized the dose/concentration-dependent, time-dependent, carbon chain length-dependent, sex-specific, and coexposure effects, and discussed the underlying mechanisms and possible prevention and treatment. Extensive epidemiological and laboratory evidence suggests that accumulated serum levels of legacy PFAS possibly contribute to an increased risk of CVD and its subclinical course, such as cardiac toxicity, vascular disorder, hypertension, and dyslipidemia. The underlying biological mechanisms may include oxidative stress, signaling pathway disturbance, lipid metabolism disturbance, and so on. Various emerging alternatives to PFAS also play increasingly prominent toxic roles in CV outcomes that are milder, similar to, or more severe than legacy PFAS. Future research is recommended to conduct more in-depth CV toxicity assessments of legacy and emerging PFAS and explore more effective surveillance, prevention, and treatment strategies, accordingly.

Emerging and Legacy Perfluoroalkyl Substances in Breastfed Chinese Infants: Renal Clearance, Body Burden, and Implications

BACKGROUND

Human breast milk is a primary route of exposure to perfluoroalkyl substances (PFAS) in infants. To understand the associated risks, the occurrence of PFAS in human milk and the toxicokinetics of PFAS in infants need to be addressed.

OBJECTIVES

We determined levels of emerging and legacy PFAS in human milk and urine samples from Chinese breastfed infants, estimated renal clearance, and predicted infant serum PFAS levels.

METHODS

In total, human milk samples were collected from 1,151 lactating mothers in 21 cities in China. In addition, 80 paired infant cord blood and urine samples were obtained from two cities. Nine emerging PFAS and 13 legacy PFAS were analyzed in the samples using ultra high-performance liquid chromatography tandem mass spectrometry. Renal clearance rates (CLrenals) of PFAS were estimated in the paired samples. PFAS serum concentrations in infants (<1 year of age) were predicted using a first-order pharmacokinetic model.

RESULTS

All nine emerging PFAS were detected in human milk, with the detection rates of 6:2 Cl-PFESA, PFMOAA, and PFO5DoDA all exceeding 70%. The level of 6:2 Cl-PFESA in human milk (median concentration=13.6 ng/L) ranked third after PFOA (336 ng/L) and PFOS (49.7 ng/L). The estimated daily intake (EDI) values of PFOA and PFOS exceeded the reference dose (RfD) of 20 ng/kg BW per day recommended by the U.S. Environmental Protection Agency in 78% and 17% of breastfed infant samples, respectively. 6:2 Cl-PFESA had the lowest infant CLrenal (0.009mL/kg BW per day), corresponding to the longest estimated half-life of 49 y. The average half-lives of PFMOAA, PFO2HxA, and PFO3OA were 0.221, 0.075, and 0.304 y, respectively. The CLrenals of PFOA, PFNA, and PFDA were slower in infants than in adults.

CONCLUSIONS

Our results demonstrate the widespread occurrence of emerging PFAS in human milk in China. The relatively high EDIs and half-lives of emerging PFAS suggest potential health risks of postnatal exposure in newborns. https://doi.org/10.1289/EHP11403.

Perfluoroalkyl acids in the aquatic environment of a fluorine industry-impacted region: Spatiotemporal distribution, partition behavior, source, and risk assessment

The present study investigated the temporal and spatial distributions, partition behaviors, sources, and risks of 14 perfluoroalkyl acids (PFAAs) in the aquatic environment of a fluorine industry-impacted region. The total concentrations of 14 PFAAs (ΣPFAAs) were 118.10-2235.4 ng/L, 40.00-2316.1 ng/g dw, and 6.90-180.5 ng/g dw in dissolved, suspended particle matter (SPM), and sedimentary phases, respectively. The predominant pollutants in the dissolved and SPM phases were perfluoroalkyl carboxylic acids (PFCAs) with carbon chain lengths <9, whereas C13 and C14 PFCAs accounted for a large proportion in the sedimentary phase. The dry season exhibited the highest concentration of ΣPFAAs in the dissolved phase (500.9 ± 350.2 ng/L), while the wet season showed the highest concentrations of ΣPFAAs in the SPM and sedimentary phases (591.6 ± 469.1 ng/g dw and 59.7 ± 35.5 ng/g dw, respectively). Significantly higher concentrations of PFAAs have been found in sewage plant and industrial areas. The concentration of PFAAs in the Xupu water source area (XPS) was slightly higher than that in other water source areas of the Yangtze River, which were either not affected or were less affected by the fluorine industry. The log K_D-SPM (distribution coefficient between SPM and water), log K_D-SED (distribution coefficient between sediment and water), and log K_OC-SED (the organic carbon normalized distribution coefficient) of PFAAs showed significant differences between the wet season and dry season, which may also be affected by carbon chain length. Source identification results showed that industries, wastewater discharge, and nonpoint sources were the main sources of PFAAs in this region. The ecological risk posed by long-chain PFAAs in aquatic organisms cannot be ignored, especially in areas with intensive industrial and agricultural activities. Health risks may exist for local toddlers with long-term exposure to perfluorooctanoic acid (PFOA) through drinking water intake and dermal contact.

Emerging polyfluorinated compound Nafion by-product 2 disturbs intestinal homeostasis in zebrafish (Danio rerio)

Nafion by-product 2 (Nafion BP2), an emerging fluorinated sulfonic acid commonly used in polymer electrolyte membrane technologies, has been detected in various environmental and human matrices. To date, however, few studies have explored its toxicity. In this study, zebrafish embryos were exposed to Nafion BP2 at concentrations of 20, 40, 60, 80, 100, 120, 140, and 160 mg/L from fertilization to 120 post-fertilization (hpf), and multiple developmental parameters (survival rate, hatching rate, and malformation rate) were then determined. Results showed that Nafion BP2 exposure led to a significant decrease in survival and hatching rates and an increase in malformations. The half maximal effective concentration (EC₅₀) of Nafion BP2 for malformation at 120 hpf was 55 mg/L, which is higher than the globally important contaminant perfluorooctane sulfonate (PFOS, 6 mg/L). Furthermore, exposure to Nafion BP2 resulted in additional types of malformations compared to PFOS exposure. Pathologically, Nafion BP2 caused abnormal early foregut development, with exfoliation of intestinal mucosa, damage to lamina propria, and aberrant proliferation of lamina propria cells. Nitric oxide content also decreased markedly. In addition, embryos showed an inflammatory response following Nafion BP2 exposure, with significantly increased levels of pro-inflammatory factors C4 and IL-6. Acidic mucin in the hindgut increased more than two-fold. 16 S rRNA sequencing revealed a marked increase in the pathogen Pseudomonas otitidis. Furthermore, pathways involved in intestinal protein digestion and absorption, inflammatory response, and immune response were significantly altered. Our findings suggest that the intestine is a crucial toxicity target of Nafion BP2 in zebrafish, thus highlighting the need to evaluate its health risks.

Fluoro-cotton assisted non-targeted screening of organic fluorine compounds from rice (Oryza sativa L.) grown in perfluoroalkyl substance polluted soil

The toxicity and environmental persistence of perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS) are of great concern for food intake in humans. However, PFASs conversion or conjugation to other substances in rice grown on PFASs polluted soil has not been explored clearly. These unknown transformed or conjugated products of PFOA and PFOS could be harmful to human health. The restriction factor in evaluating the possible transformation of PFOA and PFOS is mainly attributed to the lack of an efficient method for screening PFOA and PFOS and their related metabolites. To circumvent this challenge, we established a non-targeted screening method by combining a fluoro-cotton fiber-based solid phase extraction (FC-SPE) and liquid chromatography-high resolution mass spectrometry (LC-HRMS) to monitor the formation of possible organic fluorine compounds from rice (Oryza sativa L.) grown on PFASs. We synthesized fluoro-cotton fibers to serve as the FC-SPE packing material and characterized by field-emission scanning electron-microscope, Fourier transform infrared, and X-ray photoelectron spectroscopy measurements. The optimal extraction conditions for the prepared FC-SPE were investigated. The performance of FC-SPE in LC-MS analysis was validated by linearity, precision, recovery, and matrix effect. Then the FC-SPE combined with LC-HRMS was used to specifically capture organic fluorine compounds from complex matrices via F-F interaction, including rice seedlings grown in PFOA and PFOS polluted soil and soil samples. By the established FC-SPE LC-HRMS method, in total 429 features were found as the possible organic fluorine compounds from rice seedlings grown in PFOA polluted soil among the 1781 features from the rice seedlings. Finally, we employed a¹³C metabolic tracing analysis of organic fluorine compounds in combination with the FC-SPE LC-HRMS method to further identify the features that detected from rice seedlings grown in PFOA polluted soil. The final result indicated that there were not any new organic fluorine metabolites screened out from rice grown in PFOA or PFOS polluted soil.

Uptake, distribution, and depuration of emerging per- and polyfluoroalkyl substances in mice: Role of gut microbiota

The bioaccumulation and fate in mammals of hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide dimer acid (HFPO-DA), as major alternatives for perfluorooctanoate (PFOA), have rarely been reported. In addition, the role of gut microbiota was greatly understudied. In this study, the uptake, distribution, and depuration of HFPO-TA, HFPO-DA, and PFOA were investigated by exposure to mice for 14 days, followed by a clearance period of 7 days. The patterns of tissue distribution and depuration kinetics of HFPO-TA and PFOA were similar, but different from HFPO-DA. Liver was the main deposition organ for HFPO-TA and PFOA, making contributions of 58.8 % and 59.1 % to the total mass recovered on day 14. Depuration of HFPO-DA was more rapid than HFPO-TA and PFOA. Approximately 95.3 % of HFPO-DA in liver was eliminated on day 21 compared with day 14. While the clearance rates of HPFO-TA and PFOA were only 6.1 % and 13.9 % on day 21. The comparison between normal and pseudo germ-free mice (GM) was also conducted to investigate the effect of gut microbial on in vivo absorption of the three per- and polyfluoroalkyl substances (PFASs). Significantly higher (p < 0.05) concentrations of all the three PFASs were observed in most organs and tissues of GM compared with NC group. An analysis of gut microbiota showed that the higher absorption of PFASs in GM group may be attributed to the increase of intestinal permeability (as indicated by the decrease of tight junction protein expression), which were induced by the change of lachnospiraceae abundance. The result highlighted the importance of gut microbiota in absorption and health risk evaluation of emerging PFASs.

Legacy and emerging airborne per- and polyfluoroalkyl substances (PFAS) collected on PM2.5 filters in close proximity to a fluoropolymer manufacturing facility

Large fluoropolymer manufacturing facilities are major known sources of per- and polyfluoroalkyl substances (PFAS), many of which accumulate in groundwater, surface water, crops, wildlife, and people. Prior studies have measured high PFAS concentrations in groundwater, drinking water, soil, as well as dry and wet deposition near fluoropolymer facilities; however, much less is known about near-source PFAS air concentrations. We measured airborne PFAS on PM2.5 filters in close proximity to a major fluoropolymer manufacturing facility (Chemours' Fayetteville Works) located near Fayetteville, North Carolina, USA. Weekly PM2.5 filter samples collected over a six-month field campaign using high-volume air samplers at locations 3.7 km apart, north-northeast and south-southwest of the facility were analyzed for thirty-four targeted ionic PFAS species by liquid chromatography coupled to electrospray ionization tandem mass spectrometry. Twelve emerging and ten legacy PFAS compounds were detected. Thirteen PFAS were found at higher concentrations in these nearfield samples than at regional background sites, suggesting a local source for these compounds. Five emerging and five legacy PFAS compounds had maximum concentrations exceeding 1 pg m-3. PFBA, PFHxA, PFHxDA, PFOS, PMPA, NVHOS, PFO5DoA, and Nafion BP1 contributed the most to the total (legacy + emerging) PFAS concentration (86%). Six PFAS, specifically PFBA, PFOS, PFO5DoA, Nafion BP1, Nafion BP2, and Nafion BP4, provide a consistent representative profile of elevated species across the two sites (with detection frequency >50%). To our knowledge, this is the first study to report both legacy and emerging ionic PFAS in air in close proximity to a U.S. fluoropolymer manufacturing facility.

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.

Paints: A Source of Volatile PFAS in Air─Potential Implications for Inhalation Exposure

Paints are widely used in indoor settings yet there are no data for volatile per- and polyfluoroalkyl substances (PFAS) for paints or knowledge if paints are potentially important sources of human exposure to PFAS. Different commercial paints (n = 27) were collected from local hardware stores and analyzed for volatile PFAS by gas chromatography-mass spectrometry (GC-MS), nonvolatile PFAS by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qTOF), and total fluorine by ¹⁹F nuclear magnetic resonance spectroscopy (NMR). Diluted paint required clean up to remove 6:2 fluorotelomer phosphate diester (diPAP), which thermally transforms into 6:2 FTOH at 280 °C (GC inlet temperature). Only 6:2 FTOH (0.9-83 μg/g) and 6:2 diPAP (0.073-58 μg/g) were found in five exterior and nine interior paints and only accounted for a maximum of 17% of total fluorine. Upon drying, 40% of the FTOH mass was lost, and the loss was verified by measurements of the cumulative FTOH mass measured in the air of a small, confined space over a 3 h period. Based on the liquid paint results, the ConsExpo model was used for potential exposure assessment and one commercial paint exceeded the chosen reference dose (5 μg/kg-day) for children and adults, indicating the potential for human exposure during painting.

Perfluoroalkyl substances and lipid concentrations in the blood: A systematic review of epidemiological studies

BACKGROUND

Perfluoroalkyl substances (PFAS) are widely used synthetic aliphatic compounds. This systematic review aims to assess PFAS associations with low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol (TC) and total triglyceride (TG) concentrations in human populations.

METHOD

We systematically searched four online databases, PubMed, Scopus, Embase, and Cochrane Library for relevant peer-reviewed English language articles published until July 2021. Additional relevant articles identified were also included in the search results. We categorised populations into adults (≥18 years old) and children. Primary findings were the associations between PFAS concentrations and LDL, HDL, TC, and TG concentrations in the serum, plasma, or whole blood; secondary findings were the associations between PFAS concentrations and the odds of lipid-related health outcomes. Quantitative synthesis was done by vote counting of the effect directions between concentrations of PFAS and lipids/health outcomes, repeated on articles with sample size >1000. Sign tests were performed to assess the statistical significance of the differences between positive and negative associations. Sensitivity analysis was performed by separating out articles with populations having high concentrations of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Quality was assessed with the STROBE checklist and NHBLI Study Quality Assessment Tool.

RESULTS

A total of 58 articles were included for review. There was evidence that PFAS exposure is associated with higher concentrations of LDL, HDL, and TC, particularly for PFOA-LDL, PFOA-TC, PFOS-TC, and PFNA-LDL. Associations between PFAS and TG tended to be negative, especially for perfluoroundecanoic acid (PFUnDA). Associations between PFAS concentration and the odds of secondary outcomes generally supported a positive association between PFAS and cholesterol concentrations.

CONCLUSION

We found evidence of associations between the concentrations of some PFAS-lipid pairs in human populations. Future research should be conducted on the less well-studied PFAS to explore their effects on human health and in regions where such studies are currently lacking. (300 words).