Perfluorinated Sulfonic Acids Research Articles

Predicting bioconcentration factors (BCFs) for Per- and Polyfluoroalkyl Substances (PFAS)

The bioconcentration factor (BCF) is an important parameter that gives information regarding the ability of a contaminant to be taken up by organisms from the water. Per- and polyfluoroalkyl substances (PFAS) are widespread in the environment, causing concern regarding their impact on human health. Due to the lack of available bioaccumulation data for most compounds in the PFAS group, we developed a quantitative structure-property relationship (QSPR) model to predict the log BCF for fish (taxonomic class Teleostei), based on experimental data available for the most studied 33 representatives of this group of compounds. Furthermore, we implemented the developed model to predict log BCF for an external dataset of 2,209 PFAS. Consequently, 1,045 PFAS were found not to be bioaccumulative, 208 were classified as bioaccumulative, and 956 were predicted to be very bioaccumulative. Finally, we obtained the high correlation (R2=0.844) between the log BCFs obtained in laboratory and field studies for 13 PFAS. In silico analyses indicate that PFAS bioconcentration depends on the size (chain length – number of CF2 groups in alkyl tail/chain) of a molecule, as well as on the atomic distribution properties. In general, long-chain PFAS - above 8 and 6 carbon atoms for perfluorinated carboxylic acids (PFCAs)and perfluorinated sulfonic acids (PFSAs), respectively - tend to bioconcentrate more compared to the short-chain ones. In conclusion, predicting BCF on fish is possible for a wide range of fluorinated compounds, which can be further used for estimating PFAS behavior in the environment.

Dumbbell‐Shaped, Block‐Graft Copolymer with Aligned Domains for High‐Performance Hydrocarbon Polymer Electrolyte Membranes

AbstractGiven the environmental concerns surrounding fluoromaterials, the use of high‐cost perfluorinated sulfonic acids (PFSAs) in fuel cells and water electrolysis contradicts the pursuit of clean energy systems. Herein, we present a fluorine‐free dumbbell‐shaped block‐graft copolymer, derived from the cost‐effective triblock copolymer, poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS), for polymer electrolyte membranes (PEMs). This unique polymer shape led to the alignment of the hydrophobic‐hydrophilic domains along a preferred orientation, resulting in the construction of interconnected proton channels across the membrane. A bicontinuous network allowed efficient proton transport with reduced tortuosity, leading to an exceptional ionic conductivity (249 mS cm−1 at 80 °C and 90 % relative humidity (RH)), despite a low ion exchange capacity (IEC; 1.41). Furthermore, membrane electrode assembly (MEA) prepared with our membrane exhibited stable performance over a period of 150 h at 80 °C and 30 % RH. This study demonstrates a novel polymer structure design and highlights a promising outlook for hydrocarbon PEMs as alternatives to PFSAs.

Dumbbell-Shaped, Block-Graft Copolymer with Aligned Domains for High-Performance Hydrocarbon Polymer Electrolyte Membranes.

Given the environmental concerns surrounding fluoromaterials, the use of high-cost perfluorinated sulfonic acids (PFSAs) in fuel cells and water electrolysis contradicts the pursuit of clean energy systems. Herein, we present a fluorine-free dumbbell-shaped block-graft copolymer, derived from the cost-effective triblock copolymer, poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), for polymer electrolyte membranes (PEMs). This unique polymer shape led to the alignment of the hydrophobic-hydrophilic domains along a preferred orientation, resulting in the construction of interconnected proton channels across the membrane. A bicontinuous network allowed efficient proton transport with reduced tortuosity, leading to an exceptional ionic conductivity (249 mS cm-1 at 80 °C and 90 % relative humidity (RH)), despite a low ion exchange capacity (IEC; 1.41). Furthermore, membrane electrode assembly (MEA) prepared with our membrane exhibited stable performance over a period of 150 h at 80 °C and 30 % RH. This study demonstrates a novel polymer structure design and highlights a promising outlook for hydrocarbon PEMs as alternatives to PFSAs.

Fate and partition of perfluoroalkyl acids (PFAAs) driven by particles in mangrove ecosystems: Mechanistic insights and environmental implications

A critical gap in understanding emerging pollutants in mangrove ecosystems should be addressed. Despite their ecological importance, the state of environmental quality in fragmented mangrove patches, especially emerging contaminants, remains largely uncharted. Our research presented an in-depth analysis of the distribution of perfluoroalkyl acids (PFAAs) across porewater, suspended particles, and sediment in these small, fragmented mangroves, revealing the mechanisms behind their distribution. The findings indicated that PFAA concentrations in sediments were generally lower than in suspended particles, except for C12–C14 perfluorinated carboxylic acids (PFCAs) and C4–C6 perfluorinated sulfonic acids (PFSAs). A comparison of contamination levels in different mangrove patches concurred with conventional water quality assessments and crab burrow surveys, showing that large artificially planted patches were less contaminated, while areas with intense human activity were more polluted. Notably, no significant differences were observed in the concentrations of long-chain PFAAs and PFCAs between patches (p > 0.1). Elevated crab burrowing activity and higher concentrations of perfluorobutanoic acid (PFBA) and perfluorohexane sulfonic acid (PFHxS) in suspended particles in low intertidal zones suggested that seafood, particularly crabs and shellfish, might be at risk of PFAA pollution. Rainfall-runoff was identified as the primary source of PFAA pollution in porewater and suspended particle systems in these areas. The transport of PFAAs and organic carbon in mangroves was influenced by the concentrations and properties of suspended particles. These insights were critical for developing targeted environmental management strategies to mitigate the impact of PFAAs and preserve the ecological integrity of mangrove ecosystems.

Analysis of Binding Modes between Three Perfluorosulfonates and GPER Based on Computational Simulation and Multiple Spectral Methods.

Perfluorinated compounds (PFCs) belong to a significant category of global environmental pollutants. Investigating the toxicological effects of PFCs within biological systems is of critical significance in various disciplines such as life sciences, environmental science, chemistry, and ecotoxicology. In this study, under simulated human physiological conditions (pH = 7.4), a combination of multiple spectroscopic techniques and computational simulations was employed to investigate the impact of perfluorinated compounds (PFCs) on the G protein-coupled estrogen receptor (GPER). Additionally, the research focused on exploring the binding modes and toxicological mechanisms between PFCs and GPER at the molecular level. All three perfluorinated sulfonic acids (PFSAs) can induce quenching of GPER fluorescence through static quenching and non-radiative energy transfer. Steady-state fluorescence calculations at different temperatures revealed apparent binding constants in the order of 106, confirming a strong binding affinity between the three PFSAs and GPER. Molecular docking studies indicated that the binding sites of PFSAs are located within the largest hydrophobic cavity in the head region of GPER, where they can engage in hydrogen bonding and hydrophobic interactions with amino acid residues within the cavity. Fourier transform infrared spectroscopy, three-dimensional fluorescence, and molecular dynamics simulations collectively indicate that proteins become more stable upon binding with small molecules. There is an overall increase in hydrophobicity, and alterations in the secondary structure of the protein are observed. This study deepens the comprehension of the effects of PFCs on the endocrine system, aiding in evaluating their potential impact on human health. It provides a basis for policy-making and environmental management while also offering insights for developing new pollution monitoring methods and drug therapies.

Thermochemistry of Gas-Phase Thermal Oxidation of C2 to C8 Perfluorinated Sulfonic Acids with Extrapolation to C16.

New ideal-gas thermochemistry Cp°(T), H°(T), S°(T), and G°(T) are predicted for 53 species involved in the thermal destruction of perfluorinated sulfonic acids (PFSAs) ranging from C2 to C8 in perfluorinated alkyl chain length. Species were selected by considering both the pyrolytic and oxidative pathways of PFSA destruction. After the sulfur-containing moieties are removed, subsequent reactions largely involve species from a prior set of thermochemistry for the thermal destruction of perfluorinated carboxylic acids (Ram et al., J. Phys. Chem. A, 2024, 128, 7, 1313-1326). Enthalpies of formation at 0 K are computed using a new isogyric reaction scheme. Rigid-rotor harmonic-oscillator partition functions were calculated over a 200-2500 K temperature range using rovibrational properties at G4 (≤C3S1 species) and M06-2X-D3(0)/def2-QZVPP (≥C4S1 species), employing the 1D hindered rotor approximation to correct for torsional modes. Seven-coefficient NASA polynomial fits are reported in standardized formats. Bond dissociation energies and important reaction equilibria are examined to provide insights into the reactivity of potentially persistent species. Extrapolated NASA polynomials are also systematically predicted for 126 species larger than C8/C8S1 in size, allowing reasonably accurate estimates of thermochemistry without the need for expensive electronic structure calculations.

Abstract 828: Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-cohort study

Abstract Background: Perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), notable representatives of perfluoroalkyl substances (PFASs), are synthetic persistent chemicals widely accumulated and detected in humans. Short-chain PFASs [PFCAs with carbon number <8 and PFSAs <6, e.g. perfluoroheptanoic acid (PFHpA)] are considered less bioaccumulative and increasingly used in commercial products, yet their health impacts are rarely investigated. Perfluorooctanoic acid (PFOA) has been categorized as a possible human carcinogen (group 2B) and a potential mammary toxicant. However, few population studies explored the prospective associations of PFOA and other common PFASs with breast cancer risk nor the underlying mechanisms. Methods: Hence, we conducted a case-cohort study within the DongFeng-Tongji Cohort, compromising 226 incident breast cancer cases and a random sub-cohort of 990 individuals. Plasma concentrations of four PFCAs [PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and PFHpA] and two PFSAs [perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS)], as well as peripheral blood mitochondrial DNA copy number (mtDNAcn) levels, were measured at baseline. Results: Using Barlow-weighted Cox regression, we found 35% and 20% increased incident risk of breast cancer for each 1-unit ln-transformed increase in PFOA and PFHpA, respectively [HR (95% CI) = 1.35 (1.03, 1.78) and 1.20 (1.02, 1.40)]. Quantile g-computation analysis revealed a 19% increased incident risk of breast cancer along with each simultaneous quartile increase in all ln-transformed PFCA concentrations [HR (95% CI) = 1.19 (1.01, 1.41)], driven mainly by contributions from PFOA (56%), PFNA (24%), and PFHpA (20%). Besides, mtDNAcn was positively associated with PFHpA levels [β (95% CI) =0.027 (0.005, 0.048)], but not with PFOA or PFNA (P>0.05). We also found significantly higher breast cancer risk in participants with the highest mtDNAcn (Q4, ≥1.52) than those with the lowest (Q1, <0.87) [HR (95% CI) =2.92 (1.69, 5.04)], and that mtDNAcn mediated 12.77% of PFHpA-breast cancer association [Indirect effect, HR (95% CI) =1.02 (1.00, 1.04)]. No significant mediation effect of mtDNAcn was observed in associations of PFOA and PFNA with breast cancer (P>0.05). Conclusions: Our work unveiled the relationship of short-chain PFHpA with increased incident risk of breast cancer for the first time and highlighted the intermediate role of mtDNAcn in this association, providing a research clue for exploring the potential mechanisms of PFAS-induced breast cancer. Moreover, co-exposure to PFASs was observed as a risk factor for breast cancer, shedding light on breast cancer prevention by regulating PFASs as a chemical class. Citation Format: Yue Feng, Huan Guo. Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-cohort study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 828.

Casting Electrodes on PEEK Reinforced Sulfonated Polyphenylsulfone Membrane

Researchers are exploring the potential of proton exchange membranes made from hydrocarbon polymers that do not contain fluorine. These polymers possess desirable properties that could make them more environmentally friendly and cost-effective compared to current perfluorinated sulfonic acids (PFSA). Hydrocarbon polymers have a unique structure that maintains high proton conductivity while reducing gas crossover, thus presenting a promising alternative to PFSA membranes [1]. Previous studies have demonstrated the potential of hydrocarbon membranes in electrolyzers using sulfonated polyphenylene sulfone (sPPS) [2]. However, sPPS has a high ion exchange capacity (2.17 – 3.57 meq/g), leading to excessive water uptake that causes the membrane to swelling and impedes upscaling, such as casting anodes directly onto the membrane. To overcome this issue, a woven, open-mesh PEEK substrate was incorporated into the membrane. The reinforced membrane exhibited a significant reduction in water uptake of up to 53% at room temperature and 43% at 60°C compared to the initial membrane. This improvement made it possible to cast the anode directly onto the membrane, resulting in a homogeneous surface (Fig. 1 left). In addition, preliminary electrolysis tests showed promising performance with low membrane resistance of 69 mΩcm² for a 74 µm thick membrane (Fig. 1 right). Literature: [1] Miyake, J.; Taki, R.; Mochizuki, T.; Shimizu, R.; Akiyama, R.; Uchida, M.; Miyatake, K. Design of flexible polyphenylene proton-conducting membrane for next-generation fuel cells. Sci. Adv. 2017, 3(10), eaao0476. DOI: 10.1126/sciadv.aao0476[2] Klose, C.; Saatkamp, T.; Münchinger, A.; Bohn, L.; Titvinidze, G.; Breitwieser, M.; Kreuer, K.; Vierrath, S. All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency. Adv. Energy Mater. 2020, 10 (14), 1903995. DOI: 10.1002/aenm.201903995 Figure 1

Laboratory-Derived Bioaccumulation Kinetic Parameters for Four Per- and Polyfluoroalkyl Substances in Freshwater Mussels.

Although freshwater mussels are imperiled and identified as key conservation priorities, limited bioaccumulation information is available on these organisms for contaminants of emerging concern. In the present study we investigated the bioaccumulation of per- and polyfluoroalkyl substances (PFAS) in the model freshwater pond mussel Sagittunio subrostratus because mussels provide important ecosystem services and are important components of aquatic systems where PFAS occur. In the present study we selected four representative perfluorinated carboxylic acids and sulfonic acids, then determined the bioaccumulation kinetics of freshwater mussels in a controlled laboratory study. Because uptake (ku ) and elimination (ke ) rate constants and time to steady state are important parameters for food web bioaccumulation models, we derived bioaccumulation kinetic parameters following exposure to perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), and perfluorodecanoic acid (PFDA) at 10 µg/L and perfluoroundecanoic acid (PFUnDA) at 1 µg/L during a 14-day uptake period followed by a 7-day elimination period. Kinetic and ratio-based bioaccumulation factors (BAFs) were subsequently calculated, for example ratio-based BAFs for mussel at day 7 were determined for PFHxS (0.24 ± 0.08 L/kg), PFOS (7.73 ± 1.23 L/kg), PFDA (4.80 ± 1.21 L/kg), and PFUnDA (84.0 ± 14.4 L/kg). We generally observed that, for these four model PFAS, freshwater mussels have relatively low BAF values compared with other aquatic invertebrates and fish. Environ Toxicol Chem 2023;42:1190-1198. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Residue Distribution and Daily Exposure of Per- and Polyfluoroalkyl Substances in Indica and Japonica Rice.

Per- and polyfluoroalkyl substances (PFAS) have excellent chemical stability but have adverse environmental impacts of concern. Furthermore, bioaccumulation of PFAS in rice varieties─which is the essential staple food crop in Asia─has not been verified. Therefore, we cultivated Indica (Kasalath) and Japonica rice (Koshihikari) in the same Andosol (volcanic ash soil) paddy field and analyzed the air, rainwater, irrigated water, soil, and rice plants for 32 PFAS residues, throughout the cultivation to human consumption. During the rice cultivation period, the cultivation environment in atmospheric particulate matter (PM) constituted perfluoroalkyl carboxylic acids (PFCAs), with minimal perfluorinated sulfonic acids (PFSAs). Furthermore, perfluorooctanesulfonic acid (PFOS) migrates at a PM > 10 to drop in a cultivation field and was conducive to leakage and accumulation of PFCAs in air particles in the field environment. Moreover, precipitation was a sources of irrigation water contamination, and cultivated soil with a high carbon content could capture PFSAs and PFCAs (over C10). There were no major differences in residual PFAS trends in the rice varieties, but the distribution of PFAS in the growing soil, air, and rainwater differed. The edible white rice part was mainly affected by irrigation water in both varieties. Monte Carlo simulations of daily exposure assessments of PFOS, PFOA, and perfluorononanic acid showed similar results for Indians consuming Indica rice and Japanese consuming Japonica rice. The results indicate that the ultratrace PFAS residue concentrations and their daily exposure were not cultivar-specific.

Association of single and multiple prefluoroalkyl substances exposure with preterm birth: Results from a Chinese birth cohort study

BackgroundPerfluoroalkyl substances (PFASs) are persistent organic pollutants that may lead the adverse birth outcomes, including preterm birth (PTB). However, previous studies have reported inconsistent results on the association between PFASs and PTB, and lack of the epidemiological evidence regarding the effect of PFASs mixture on PTB. This study aimed to explore association of individual and multiple exposure to PFASs with PTB. MethodsThe study subjects were consisted of 1341 pregnant women from Guangxi Zhuang Birth Cohort in Guangxi, China, from June 2015 to April 2019. Nine PFASs concentrations in the maternal serum were examined by ultrahigh liquid performance chromatography-tandem mass spectrometry, and the gestational weeks were obtained from medical records. We applied binary logistics regression model to explore correlation between individual PFAS and PTB and inspected the combined effect of PFASs mixture on PTB by applying Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression models. ResultsIn adjusted logistics regression model, perfluorooctane sulfonate (PFOS), perfluoroheptanoic acid (PFHpA), perfluorobutanesulfonic acid (PFBS), ∑perfluorinated sulfonic acids (PFSA), and ∑PFASs were positively associated with the risk of PTB. In contrast, perfluoroundecanoic acid (PFUnA), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA) were negatively associated with the risk of PTB. These associations of n PFOS and PFHpA with PTB were found to be more pronounced in male infants. Restricted cubic splines (RCSs) showed an inverse U-shaped relationship between PFBS and PTB. Analysis from BKMR model showed a positive association between PFASs mixture and PTB, and no evidence of interactions among the nine PFASs were detected. Additionally, PFHpA, PFOS, and PFBS were identified as the main contributors for the effect of PFASs mixture on increasing the risk of PTB by BKMR and WQS models. ConclusionPrenatal exposure to higher levels of PFASs mixture was associated with higher risk of PTB.

Combining target analysis with sum parameters-a comprehensive approach to determine sediment contamination with PFAS and further fluorinated substances.

Recent studies aiming at a fluorine mass balance analysis in sediments combined the determination of extractable organic fluorine (EOF) with target analysis. They reported high fractions of unidentified organic fluorine (UOF) compounds, as the target analysis covers only a limited number of per- and polyfluoroalkyl substances (PFAS). For this reason, in this study, a comprehensive approach was used combining target analysis with an extended PFAS spectrum, the EOF and a modified total oxidisable precursor (TOP) assay, which includes trifluoroacetic acid, to determine the PFAS contamination in sediments (n=41) and suspended solids (n=1) from water bodies in Northern Germany (Lower Saxony). PFAS are ubiquitous in the sediments (detected in 83% of the samples). Perfluorinated carboxylic acids (PFCAs) were found in 64% of the samples; perfluorinated sulfonic acids (PFSAs) were detected less frequently (21%), with the highest concentration observed for perfluorooctanesulfonic acid (PFOS). Levels of precursors and substitutes were lower. Applying the TOP assay resulted in an increase in PFCAs in 43% of the samples analysed. In most cases, target analysis and the TOP assay could not account for the EOF concentrations measured. However, as the fraction of UOF decreased significantly, the application of the TOP assay in fluorine mass balance analysis proved to be an important tool in characterising the PFAS contamination of riverine sediments.

Global patterns and temporal trends of perfluoroalkyl substances in municipal wastewater: A meta-analysis

Despite increasing regulatory efforts to reduce production of per- and polyfluoroalkyl substances (PFAS), continued human and ecological exposure to PFAS has led to concerns about historical releases. Municipal wastewater treatment plants (WWTPs) provide important conduits between waste sources and the environment. We present a meta-analysis of results reported in 44 peer-reviewed publications that include 460 influent and 528 effluent samples, collected from 21 countries, for which some or all of five perfluorinated carboxylic acids (PFCAs) and three perfluorinated sulfonic acids (PFSAs) were measured. Our meta analysis revealed global patterns and trends that, to our knowledge, have not been reported elsewhere. Regression analyses of samples collected from 2004 to 2020 quantified the temporal trends of global wastewater effluent concentrations of each of the PFAS and the corresponding mean concentration for each country. Although legacy compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), have been reported with the highest measured concentrations, their global temporal trends are lowest of all PFAS considered. Concentrations of most PFAS analyzed in wastewater in the United States have not changed significantly with time, whereas reported PFAS concentrations in wastewater effluent from China have increased from 11% to 37% per year. In addition, our results show significant positive correlations between previous wastewater effluent concentrations of individual PFAS and the gross domestic product per capita of each country. Our analysis of this global data set also confirmed conclusions from previous studies on smaller data sets: (i) none of the PFAS studied are effectively removed by conventional treatment processes; (ii) effluents from treatment plants that include a significant industrial component to their influent tend to have higher PFAS concentrations; and (iii) the few studies that measured both aqueous concentrations and concentrations adsorbed to suspended particulate matter (SPM) indicate that PFAS adsorbed to SPM can contribute significantly to the total PFAS load.

Plasma perfluoroalkyl substance exposure and incidence risk of breast cancer: A case-cohort study in the Dongfeng-Tongji cohort

Experimental studies have suggested perfluoroalkyl substances (PFASs) as mammary toxicants, but few studies evaluated the prospective associations of PFASs with breast cancer risk. We performed a case-cohort study within the Dongfeng-Tongji cohort, including incident breast cancer cases (n = 226) and a random sub-cohort (n = 990). Baseline plasma concentrations of four perfluorinated carboxylic acids (PFCAs) [perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroheptanoic acid (PFHpA)] and two perfluorinated sulfonic acids (PFSAs) [perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS)] were measured. Barlow-weighted Cox regression models revealed that each 1-unit increase in ln-transformed PFOA and PFHpA was associated with a separate 35% and 20% elevated incident risk of breast cancer [HR(95%CI) = 1.35(1.03, 1.78) and 1.20(1.02, 1.40), respectively], which were also significant among postmenopausal females [HR(95%CI) = 1.34(1.01, 1.77) and 1.23 (1.02, 1.48), respectively]. Quantile g-computation analysis observed a 19% increased incident risk of breast cancer along with each simultaneous quartile increase in all ln-transformed PFCA concentrations [HR(95%CI) = 1.19(1.01, 1.41)], with PFOA accounting for 56% of the positive effect. Our findings firstly revealed the impact of short-chain PFHpA on increased incident risk of breast cancer, suggested exposure to PFASs as a risk factor for breast cancer, and shed light on breast cancer prevention by regulating PFASs as a chemical class.

Distribution, source identification and health risk assessment of PFASs in groundwater from Jiangxi Province, China

There is an urgent need to investigate on the distribution and fate of short-chain analogues and emerging per- and polyfluoroalkyl substances (PFASs) in groundwater, and little research on their source apportionment and health risks through the drinking water exposure pathway has been carried out. In present study, the concentration and source of 22 PFASs, including five alternatives: 6:2 fluorotelomer sulfonate (6:2 FTS), potassium 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F–53B), hexafluoropropylene oxide trimer acid (HFPO-TA), hexafluoropropylene oxide dimer acid (HFPO-DA) and ammonium 4, 8-dioxa-3H-perfluorononanoate (ADONA), were analyzed in 88 groundwater samples from wells in Jiangxi Province, southeastern China. The total PFASs concentration (Σ18PFASs) in groundwater varied from 1.27 to 381.00 ng/L (mean 47.60 ng/L). Short-chain perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were the most abundant perfluorinated carboxylic acids (PFCAs), and short-chain perfluorobutanesulfonate (PFBS) was the most abundant perfluorinated sulfonic acids (PFSAs) in groundwater samples. The quantitative source apportionment by nonnegative matrix/tensor factorization coupled with k-means clustering (NMFk) model suggested that short-chain homologues and emerging alternatives have been used as substitutes for legacy PFOS and PFOA. Furthermore, the human risk assessment results showed that the estimated daily intakes (EDIs) for short-chain PFCAs were higher than that of PFOA, whereas the EDIs of PFBS, 6:2 FTS and F–53B were comparable to that of PFOS.

Predicting the effects of per- and polyfluoroalkyl substance mixtures on peroxisome proliferator-activated receptor alpha activity in vitro

Human exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous, with mixtures of PFAS detected in drinking water, food, household dust, and other exposure sources. Animal toxicity studies and human epidemiology indicate that PFAS may act through shared mechanisms including activation of peroxisome proliferator activated receptor α (PPARα). However, the effect of PFAS mixtures on human relevant molecular initiating events remains an important data gap in the PFAS literature. Here, we tested the ability of modeling approaches to predict the effect of diverse PPARα ligands on receptor activity using Cos7 cells transiently transfected with a full length human PPARα (hPPARα) expression construct and a peroxisome proliferator response element-driven luciferase reporter. Cells were treated for 24 h with two full hPPARα agonists (pemafibrate and GW7647), a full and a partial hPPARα agonist (pemafibrate and mono(2-ethylhexyl) phthalate), or a full hPPARα agonist and a competitive antagonist (pemafibrate and GW6471). Receptor activity was modeled with three additive approaches: effect summation, relative potency factors (RPF), and generalized concentration addition (GCA). While RPF and GCA accurately predicted activity for mixtures of full hPPARα agonists, only GCA predicted activity for full and partial hPPARα agonists and a full agonist and antagonist. We then generated concentration response curves for seven PFAS, which were well-fit with three-parameter Hill functions. The four perfluorinated carboxylic acids (PFCA) tended to act as full hPPARα agonists while the three perfluorinated sulfonic acids (PFSA) tended to act as partial agonists that varied in efficacy between 28–67 % of the full agonist, positive control level. GCA and RPF performed equally well at predicting the effects of mixtures with three PFCAs, but only GCA predicted experimental activity with mixtures of PFSAs and a mixture of PFCAs and PFSAs at ratios found in the general population. We conclude that of the three approaches, GCA most accurately models the effect of PFAS mixtures on hPPARα activity in vitro. Understanding the differences in efficacy with which PFAS activate hPPARα is essential for accurately predicting the effects of PFAS mixtures. As PFAS can activate multiple nuclear receptors, future analyses should examine mixtures effects in intact cells where multiple molecular initiating events contribute to proximate effects and functional changes.

Levels and profiles of perfluorinated alkyl acids in liver tissues of birds with different habitat types and trophic levels from an urbanized coastal region of South Korea

Contamination status and characteristics of perfluorinated alkyl acids (PFAAs) including perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs) was examined using liver tissue of birds - black-tailed gulls (Larus crassirostris), domestic pigeons (Columba livia var. domestica), pacific loons (Gavia pacifica), herons (Ardea cinerea), and egrets (Egretta garzetta and Ardea alba) - with different trophic levels, habitat types and migratory behaviors from an industrialized coastal region of South Korea. A wide range of PFAAs (1.09 ng/g to 1060 ng/g; median = 52.6 ng/g) were detected in bird livers from the Korean coasts with high detection frequency. Accumulation features of PFAAs in birds indicated that primarily trophic position and secondly habitat type influence the levels and composition of PFAAs, e.g., relatively high PFAA levels and high composition of odd-numbered long carbon chain PFCAs (perfluoroundecanoic acid (PFUnDA) and perfluorotridecanoic acid (PFTriDA)) and PFOS in higher trophic and marine birds. The prevalence of long carbon chain (≥14) PFCAs likely implies a wide use of fluorotelomer-based substances in Korea. Interspecies comparison in the accumulation profile of persistent organic pollutants (including polychlorinated biphenyls (PCBs), organochlorine pesticides, polybrominated diphenylethers (PBDEs), and PFAAs) reveals relatively high load of PFAAs in inland (pigeons) and estuarine (egrets/herons) species compared to marine bird species, indicating wide use of PFAAs in the terrestrial environment.

Occurrence and distribution of per- and polyfluoroalkyl substances (PFASs) in human livers with liver cancer

Per- and polyfluoroalkyl substances (PFASs) are anthropogenic compounds that are widely accumulated in human tissues, and the liver is considered a primary target organ for PFASs exposure. The occurrence and distribution of 21 PFASs in liver tissues with tumors (n = 55) and without tumors (n = 55) are investigated in this study. Eleven perfluorinated carboxylic acids (PFCAs) and five perfluorinated sulfonic acids (PFSAs) were detected at high frequencies (45.5%–100 %), while the detection frequencies of five perfluoroalkyl phosphate (PFPAs) were relatively lower (≤29.1 %). PFSAs and PFCAs accounted for up to 82.5%–92.7 % of the total PFASs. Although it was not found to be statistically significant, the concentrations of the total PFASs were slightly higher in the tumor liver samples (mean 64.3, range 5.70–303 ng/g) than those in the non-tumor liver samples (mean 62.7, range 4.08–240 ng/g).The perfluorooctanoic acid (PFOA), perfluorotridecanoic acid (PFTrDA), and perfluorobutanesulphonate (PFBS) showed significant differences (p < 0.05) between the tumor and non-tumor liver samples, and the different distribution levels of these three PFASs may have been a consequence of oxidative stress. The total concentrations of PFASs in the three age groups were in the decreasing order of middle-aged people (45–60) > old people (>60) > young people (<45). The PFASs in females were generally lower than in males, which may have been related to women's special excretion methods (such as childbirth and breastfeeding). The results should be valuable for further mechanistic studies regarding the toxic effects of PFASs in human livers.

Analysis of elimination half-lives in MamTKDB 1.0 related to bioaccumulation: Requirement of repeated administration and blood plasma values underrepresent tissues

When building the novel public mammalian toxicokinetic database (MamTKDB) we collected and included 3927 elimination half-lives (elimt1/2) for 1407 xenobiotics in various species (rat, human, mouse, dog, monkey, rabbit, cattle, pig, sheep, guinea pig, hamster, horse and goat) with specification of compartment (whole body, organ/tissue, cell type, medium) studied. Here we describe and analyse the collected data in MamTKDB 1.0. Most elimt1/2 are for humans and rats and their data differ in some ways: whereas the rat data are mainly for pesticides, the human data are mainly for pharmaceuticals and environmental contaminants. There are also differences in types of compartments studied and in metabolites followed: human elimt1/2 are mainly whole body based (i.e. based on blood plasma or excretion), animal data are additionally for various organs/tissues, cells or media. Contrary to human studies, animal studies regularly administrate radiolabeled (e.g. 14C) substances and distribution of both parent and eventual metabolites are followed, measuring the radioactivity. In rats, substances had been given through single, preconditioning or repeated administration. Single administration studies dominated, but repeated studies generally had longer elimt1/2 than single or preconditioning studies for which elimt1/2 were similar. Repeated administration studies should better ascertain steady state conditions throughout the body, a process involving time-dependent tissue loading, and the data show that for most substances, repeated studies are required to address bioaccumulation potential. About 65% of the substances in MamTKDB 1.0 fulfilled the octanol–water and octanol–air partitioning-based screening criteria (log Kow > 2 and log Koa > 5) for further bioaccumulation assessment and/or testing, and most of the substances with long elimt1/2 in both humans and rats fulfill these criteria. Of note, however, there are also many chemicals with log Kow > 2 with intermediate or short elimt1/2. Per- and polyfluoroalkyl substances (PFAS) stand out in that they often have log Koa < 5. Rats are poor toxicokinetic test models for perfluoroalkyl acids (PFAAs) for which pigs (and possibly mice) elimt1/2 data resemble those of humans better. Perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs) of similar molecular weight had similar elimt1/2 in the species tested. For polychlorinated biphenyls (PCBs), elimt1/2 increases with the degree of chlorination in humans. In relation to other compartments, blood plasma/serum had among the shortest elimt1/2 in rats and often underrepresent elimt1/2 in tissues. Rat data were divided into 38 compartment (tissue or media) types out of which 20 had sufficient data for correlational tests. In general, there was a strong degree of correlation of rat elimt1/2 in-between most compartments, but there were also exceptions. Surprisingly, the correlation between brain and white fat was relatively weak. Interestingly, several substances or their metabolites bound to haemoglobin in red blood cells. MamTKDB 1.0 allows investigation on how certain chemical characteristics influence elimt1/2 and is a promising database for assessment of bioaccumulation potential.

Rapid detection of perfluorinated sulfonic acids through preconcentration by bubble bursting and surface-assisted laser desorption/ionization.

We developed a preconcentration method in which aerosol droplets containing enriched perfluorinated sulfonic acids (PFSs) are generated through bubble bursting and collected. The droplets were subjected to PFS analysis of perfluorohexane sulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) through surface-assisted laser desorption/ionization-time-of-flight mass spectrometry; silver nanoplates (AgNPts) were assisting materials. The method was highly efficient, with an approximately three-order magnitude enhancement (5 × 10-13 to 1 × 10-11 M). Ultralow PFS concentrations (0.5 ng/L of PFOS; 0.4 ng/L of PFHxS) were detected in preconcentrated tap water containing PFSs. Our method has potential for rapid real-world PFS detection in water.