Occurrence and Tissue Distribution of Novel Perfluoroether Carboxylic and Sulfonic Acids and Legacy Per/Polyfluoroalkyl Substances in Black-Spotted Frog (Pelophylax nigromaculatus)

Novel and legacy poly- and perfluoroalkyl substances (PFASs) in indoor dust from urban, industrial, and e-waste dismantling areas: The emergence of PFAS alternatives in China

With the phase out of perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), the composition profiles of poly- and perfluoroalkyl substance (PFAS) in our living environment are unclear. In this study, 25 PFASs were analyzed in indoor dust samples collected from urban, industrial, and e-waste dismantling areas in China. PFOS alternatives, including 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (median: 5.52 ng/g) and 8:2 chlorinated polyfluorinated ether sulfonate (8:2 Cl-PFESA) (1.81 ng/g), were frequently detected. By contrast, PFOA alternatives, such as hexafluoropropylene oxide dimer acid (HPFO-DA, Gen-X) and ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA), were not found in any of the dust samples. As expected, all legacy PFASs were widely observed in indoor dust, and 4 PFAS precursors were also detected. Dust concentrations of 6:2 Cl-PFESA were strongly correlated (p < 0.05) with those of 8:2 Cl-PFESA regardless of sampling sites. 6:2 Cl-PFESA was also significantly associated with that of PFOS in industrial and e-waste (p < 0.01) areas. Association analysis suggested that the sources of PFOS and its alternatives are common or related. Although ∑Cl-PFESA concentration was lower than that of PFOS (17.4 ng/g), industrial areas had the highest 6:2 Cl-PFESA/PFOS ratio (0.63). Composition profiles of PFASs in the industrial area showed the forefront of fluorine change. Thus, the present findings suggested that Cl-PFESAs are widely used as PFOS alternatives in China, and high levels of human Cl-PFESA exposure are expected in the future. Short-chain PFASs (C4-C7) were the predominant PFASs found in dust samples, contributing to over 40% of ∑total PFASs. Furthermore, perfluoro-1-butanesulfonate/PFOS and perfluoro-n-butanoic acid (PFBA)/PFOA ratios were 2.8 and 0.72, respectively. These findings suggested shifting to the short-chain PFASs in the environment in China. To the authors knowledge this is the first study to document the levels of 6:2 Cl-PFESA, 8:2 Cl-PFESA in indoor dust.

Novel and legacy per- and polyfluoroalkyl substances (PFASs) in a farmland environment: Soil distribution and biomonitoring with plant leaves and locusts

The occurrence of legacy and novel per- and polyfluoroalkyl substances (PFASs) in multiple matrices from a farmland environment was investigated in the Beijing-Tianjin-Hebei core area of northern China. PFASs were ubiquitously detected in farmland soils, and the detection frequency of 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA) was higher than that of perfluorooctane sulfonic acid (98% vs. 83%). Long-chain PFASs, including 6:2 Cl-PFESA, showed a centered distribution pattern around the metropolis of Tianjin, probably due to the local intensive industrial activity, while trifluoroacetic acid (TFA) showed a decreasing trend from the coast to the inland area. Other than soil, TFA was also found at higher levels than other longer-chain PFASs in dust, maize (Zea mays), poplar (Populus alba) leaf and locust (Locusta migratoria manilens) samples. Both poplar leaves and locusts can be used as promising biomonitoring targets for PFASs in farmland environments, and their accumulation potential corresponds with protein and lipid contents. Apart from being exposed to PFASs via food intake, locusts were likely exposed via uptake from soil and precipitated dust in farmland environments. The biomonitoring of locusts may be more relevant to insectivores, which is important to conducting a comprehensive ecological risk assessment of farmland environments.

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

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

Potential sources and sediment-pore water partitioning behaviors of emerging per/polyfluoroalkyl substances in the South Yellow Sea

Emerging per/polyfluoroalkyl substances (PFASs) have received great concerns, but there are few data in the coastal environment, which play an essential role in their global transport. In this study, surface water and sediment samples were collected in the South Yellow Sea close to Jiangsu Province China, and 26 legacy as well as emerging PFASs were investigated. Perfluorooctanoic acid (PFOA) and perfluorobutane sulfonate (PFBS) were predominant in the coastal water of the South Yellow Sea with a relatively higher level than other coastal regions in the world. PFBS and 6:2 fuorotelomer sulfonic acid (6:2 FTSA) were two major alternatives of perfluorooctane sulfonate (PFOS) which were used in textile surface treatment and fire-fighting foams, respectively. Multiple receptor models identified that fluoropolymer manufacture, textile and food packages were three major sources of PFASs in the South Yellow Sea. The partitioning behaviors of PFASs between sediment and pore water in the marine environment were compared, and the partitioning coefficients of hexafluoropropylene oxide trimer acid (HFPO-TA) and 6:2 chlorinated polyfluorinated ether sulfonic acid (6:2 F-53B) were reported for the first time, which exhibited stronger partition in sediment than their predecessors. The results provide important hints to understand the environmental transport of PFASs in the marine environment.

The emerging PFOS alternative OBS exposure induced gut microbiota dysbiosis and hepatic metabolism disorder in adult zebrafish

Sodium ρ-perfluorous nonenoxybenzene sulfonate (OBS), as a novel the alternatives of PFASs, is widely used in many fields of life. Here, adult male zebrafish selected were exposed to OBS at concentrations of 3, 30 and 300 μg/L for 7 and 21 days, respectively. Based on the gut microbiota analysis, at genus level, the relative abundance of the Flavobacterium, Hyphomicrobium, Paracoccus, Lawsonia, Plesiomonas and Vibrio changed significantly in the gut of zebrafish after exposure to 300 μg/L OBS. In addition, the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis suggested that a total of 1077 metabolites in pos-model and a total of 706 metabolites in neg-model changed significantly from the liver, and these changed metabolites were tightly related to several pathways including amino acid, pyrimidine and purine metabolism, etc. Furthermore, the changed gut bacteria including Flavobacterium, Hyphomicrobium, Paracoccus, Lawsonia, Plesiomonas and Vibrio at genus level were significantly correlated with various metabolites (succinic acid, leucine, xanthine, orotic acid, nicotinic acid, etc.). Taken together, all the results showed that low dose of OBS exposure could induce the dysbiosis of gut microbiota and disturbed the hepatic metabolism balance in adult male zebrafish.

Evaluation of Developmental Toxicity, Developmental Neurotoxicity, and Tissue Dose in Zebrafish Exposed to GenX and Other PFAS

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of industrial chemicals with widespread environmental occurrence. Exposure to long-chain PFAS is associated with developmental toxicity, prompting their replacement with short-chain and fluoroether compounds. There is growing public concern over the safety of replacement PFAS.

OBJECTIVE

We aimed to group PFAS based on shared toxicity phenotypes.

METHODS

Zebrafish were developmentally exposed to 4,8-dioxa-3H-perfluorononanoate (ADONA), perfluoro-2-propoxypropanoic acid (GenX Free Acid), perfluoro-3,6-dioxa-4-methyl-7-octene-1-sulfonic acid (PFESA1), perfluorohexanesulfonic acid (PFHxS), perfluorohexanoic acid (PFHxA), perfluoro-n-octanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), or 0.4% dimethyl sulfoxide (DMSO) daily from 0-5 d post fertilization (dpf). At 6 dpf, developmental toxicity and developmental neurotoxicity assays were performed, and targeted analytical chemistry was used to measure media and tissue doses. To test whether aliphatic sulfonic acid PFAS cause the same toxicity phenotypes, perfluorobutanesulfonic acid (PFBS; 4-carbon), perfluoropentanesulfonic acid (PFPeS; 5-carbon), PFHxS (6-carbon), perfluoroheptanesulfonic acid (PFHpS; 7-carbon), and PFOS (8-carbon) were evaluated.

RESULTS

PFHxS or PFOS exposure caused failed swim bladder inflation, abnormal ventroflexion of the tail, and hyperactivity at nonteratogenic concentrations. Exposure to PFHxA resulted in a unique hyperactivity signature. ADONA, PFESA1, or PFOA exposure resulted in detectable levels of parent compound in larval tissue but yielded negative toxicity results. GenX was unstable in DMSO, but stable and negative for toxicity when diluted in deionized water. Exposure to PFPeS, PFHxS, PFHpS, or PFOS resulted in a shared toxicity phenotype characterized by body axis and swim bladder defects and hyperactivity.

CONCLUSIONS

All emerging fluoroether PFAS tested were negative for evaluated outcomes. Two unique toxicity signatures were identified arising from structurally dissimilar PFAS. Among sulfonic acid aliphatic PFAS, chemical potencies were correlated with increasing carbon chain length for developmental neurotoxicity, but not developmental toxicity. This study identified relationships between chemical structures and in vivo phenotypes that may arise from shared mechanisms of PFAS toxicity. These data suggest that developmental neurotoxicity is an important end point to consider for this class of widely occurring environmental chemicals. https://doi.org/10.1289/EHP5843.

Chlorinated Polyfluoroalkylether Sulfonic Acids Exhibit Stronger Estrogenic Effects than Perfluorooctane Sulfonate by Activating Nuclear Estrogen Receptor Pathways

Chlorinated polyfluoroalkylether sulfonic acids (Cl-PFESAs) have been shown to have potential thyroid hormone (TH) disruption effects. Here, we further investigated their estrogenic effects and underlying mechanisms. In vivo results revealed that exposure of zebrafish to Cl-PFESAs induced disorder of sex hormones during the early embryonic stages and caused histopathological lesions in the gonads of adult zebrafish relative to control groups. To find out whether the estrogen receptor is the molecular target of Cl-PFESAs, the binding interaction between Cl-PFESAs and ERs was investigated using a series of in vitro assays. We found that all tested chemicals could bind directly to ERs and exhibit relatively weak agonistic activity toward ERs, suggesting that the ER-mediated signaling pathway is directly involved in the estrogenic effects of Cl-PFESAs. The internal dose of 8:2 Cl-PFESA was significantly higher than the others, which explained why it obviously displayed an ER agonistic effect despite its weak ER binding affinity. Taken together, these results uncover that, in addition to the TH disruption effect, Cl-PFESAs might also cause estrogenic effects by activating ER pathways.

Nontarget Discovery of Per- and Polyfluoroalkyl Substances in Atmospheric Particulate Matter and Gaseous Phase Using Cryogenic Air Sampler

Novel per- and polyfluoroalkyl substances (PFASs) have become a key issue in global environmental studies. Although several novel PFASs have been discovered in atmospheric particulate matter through nontarget analysis, information on the environmental occurrence of novel PFASs in atmospheric gaseous phases and conventional sampling techniques is somewhat deficient. Therefore, this Article describes a new type of air sampler, the cryogenic air sampler (CAS), which was used to collect all atmospheric components simultaneously. Nontarget analysis then was performed through PFASs homologue analysis. A total of 117 PFAS homologues (38 classes) were discovered, 48 of which (13 classes) were identified with confidence Level 4 or above. Eleven chlorinated perfluoropolyether alcohols (3 classes) and four chlorinated perfluoropolyether carboxylic acids (2 classes) have been reported for the first time in this Article. This Article is also the first report of 12 hydrosubstituted perfluoroalkyl carboxylates (H-PFCAs) in the atmosphere. H-PFCAs and chlorinated perfluoropolyether carboxylic acids were mainly distributed in the particular phase. These results are evidence that novel chlorinated polyether PFASs should be the focus of future study.

High trans-placental transfer of perfluoroalkyl substances alternatives in the matched maternal-cord blood serum: Evidence from a birth cohort study

BACKGROUND

Recent studies suggest that perfluoroalkyl substances (PFAS) and PFAS alternatives can cross the placental barrier. However, little is known on the differential patterns of trans-placental transfer (TPT) among conventional PFAS and PFAS alternatives in epidemiological study.

OBJECTIVES

We aimed to characterize comprehensive TPT patterns in conventional PFAS and PFAS alternatives using matched maternal-cord blood serum from a birth cohort.

METHODS

A total of 424 mother-fetus pairs were recruited from the Maoming Birth Cohort during 2015-2018. We detected 20 PFAS in cord and maternal serum using an ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). TPT of PFAS was calculated via cord to maternal serum concentration ratios.

RESULTS

Both of PFOS alternatives (chlorinated polyfluorinated ether sulfonates, Cl-PFESAs) and PFOA short-chain alternative (perfluorobutanoic acid, PFBA) were widely detected in the cord and maternal serum. In cord serum, the predominant PFAS was PFOS (1.93 ng/mL), followed by PFBA (1.45 ng/mL), PFOA (0.75 ng/mL) and 6:2 Cl-PFESA (0.32 ng/mL). We found that the PFAS alternatives had higher TPT than PFOS and PFOA, such as PFBA vs. PFOA (median: 1.41 vs. 0.73, P < 0.001) and 8:2 Cl-PFESA vs. PFOS (median: 0.98 vs. 0.42, P < 0.001). Moreover, the TPT of 8:2 Cl-PFESA was higher than the precursor, linear and isomeric PFOS, respectively (P < 0.01). Furthermore, we found a U-shaped pattern for TPT in perfluorocarboxylic acid compounds (PFCAs) across different length of carbon chain.

CONCLUSION

Our findings suggest that PFAS alternatives may be more easily across the placenta than conventional PFAS. Given the widespread usage of PFAS alternatives, our results indicate that more research is needed to assess the potential health risks of prenatal exposure to PFAS alternatives in children.

Degradation of Perfluoroalkyl Ether Carboxylic Acids with Hydrated Electrons: Structure-Reactivity Relationships and Environmental Implications

This study explores structure-reactivity relationships for the degradation of emerging perfluoroalkyl ether carboxylic acid (PFECA) pollutants with ultraviolet-generated hydrated electrons (e_aq^-). The rate and extent of PFECA degradation depend on both the branching extent and the chain length of oxygen-segregated fluoroalkyl moieties. Kinetic measurements, theoretical calculations, and transformation product analyses provide a comprehensive understanding of the PFECA degradation mechanisms and pathways. In comparison to traditional full-carbon-chain perfluorocarboxylic acids, the distinct degradation behavior of PFECAs is attributed to their ether structures. The ether oxygen atoms increase the bond dissociation energy of the C-F bonds on the adjacent -CF₂- moieties. This impact reduces the formation of H/F-exchanged polyfluorinated products that are recalcitrant to reductive defluorination. Instead, the cleavage of ether C-O bonds generates unstable perfluoroalcohols and thus promotes deep defluorination of short fluoroalkyl moieties. In comparison to linear PFECAs, branched PFECAs have a higher tendency of H/F exchange on the tertiary carbon and thus lower percentages of defluorination. These findings provide mechanistic insights for an improved design and efficient degradation of fluorochemicals.

Are perfluorooctane sulfonate alternatives safer? New insights from a birth cohort study

BACKGROUND

Experimental studies show that chlorinated polyfluorinated ether sulfonic acids (Cl-PFESA 6:2 and 8:2), one of perfluoroalkyl substances (PFAS) used as perfluorooctane sulfonate (PFOS) alternatives, are reproductive toxicants in vivo and in vitro. However, the associations between gestational exposure to Cl-PFESAs and birth outcomes are unknown.

OBJECTIVES

We investigated associations between 6:2 Cl-PFESA and 8:2 Cl-PFESA in maternal serum and birth outcomes.

METHODS

We measured four PFAS, including 6:2 Cl-PFESA, 8:2 Cl-PFESA, PFOS, and perfluorooctanoic acid (PFOA) in third-trimester maternal serum collected from 372 mother-child dyads participating in the Guangzhou Birth Cohort Study. Characteristics of mothers and infants were gathered from medical records and by interviewer-administered questionnaires.

RESULTS

PFOS was the most abundant PFAS in maternal serum (median: 7.15 ng/mL), followed by 6:2 Cl-PFESA (median: 2.41 ng/mL). Greater maternal serum levels of all PFAS alternatives were significantly associated with lower birth weight, adjusted for confounding variables. For example, each ln-ng/mL greater concentration of 6:2 Cl-PFESA and 8:2 Cl-PFESA was associated with a 54.44 g [95% confidence interval (CI): -95.66, -13.22] and 21.15 g (95% CI: -41.44, -0.86) lower birth weight, respectively. Greater continuous maternal serum 6:2 Cl-PFESA (OR: 2.67, 95% CI: 1.73, 4.15) and PFOS (OR: 2.03, 95% CI: 1.24, 3.32) were also associated with higher risks for preterm birth, adjusted for confounders, with a possible threshold effect at the highest quartile of 6:2 Cl-PFESA.

CONCLUSIONS

For the first time, we report associations between maternal serum 6:2 Cl-PFESA and 8:2 Cl-PFESA concentrations and adverse birth outcomes. Our findings suggest that PFOS alternatives may be reproductive toxicants in human populations and should be considered with caution before widespread use. Given the preliminary nature of our results, additional epidemiological and toxicological investigations are needed to more definitively assess the risks.

Tissue distribution and bioaccumulation of a novel polyfluoroalkyl benzenesulfonate in crucian carp

The emergence of novel per- and polyfluoroalkyl substances (PFASs) has enabled researchers to determine their bioaccumulation, which is important for understanding their internal doses and environmental risks. Here, for the first time, we report on the occurrence of a novel PFAS, p-perfluorous nonenoxybenzenesulfonate (OBS) in wild crucian carp and explore its tissue distribution and bioaccumulation. The highest levels of OBS were observed in blood (mean/median: 144/133 ng/ml) with the mean tissue/blood ratios (TBRs) consistently below 1, ranging from 0.090 (muscle) to 0.644 (liver). This followed the pattern of perfluorooctane sulfonate (PFOS), implying that their distributions were similar. The calculated tissue-specific LogBAF values, except for muscle, 3.78 (gill)-4.14 (blood) over the regulatory bioaccumulation criterion (Log value: 3.70) indicated its obvious bioaccumulative potency in crucian carp. Molecular docking with estimated binding energies at -8.5 and -9.0 kcal/mol corroborated the strong interactions of OBS with human serum albumin and liver fatty acid binding protein, even though the binding energies were lower than those of PFOS. This, to some extent, explained the lower bioaccumulation of OBS than PFOS. Considering its bioaccumulative potential, large production volume, and wide use, further investigation into the environmental risk and in vivo toxicology of OBS is required.

Insights into Uptake, Translocation, and Transformation Mechanisms of Perfluorophosphinates and Perfluorophosphonates in Wheat (Triticum aestivum L.)

As emerging alternatives of legacy perfluoroalkyl substances, perfluorophosphinates (PFPiAs) and perfluorophosphonates (PFPAs) are widely applied in industrial and agricultural fields and are supposed to be large partitioned to soil and highly persistent. It is of particular interest to understand their transfer from roots to shoots and transformation in plants, such as wheat. The results of hydroponic experiments indicated that C6/C6 PFPiA, C8/C8 PFPiA, perfluorooctanophosphonic acid (PFOPA), and perfluorohexaphosphonic acid (PFHxPA) were quickly adsorbed on the epidermis of wheat root (Triticum aestivum L.), which was driven by their hydrophobicity. A small fraction of the accumulated PFPiAs and PFPAs in the wheat root was subjected to absorption via an active process dependent on H⁺-ATPase. PFHxPA, which has the smallest molecular weight and medium hydrophilicity (log K_ow < 4), displayed the strongest absorption efficiency via the water and anion channels and had the highest translocation potential from roots to shoots in wheat. C6/C6 and C8/C8 PFPiAs experienced phase I metabolism in wheat, although at a low rate, to form more persistent PFHxPA and PFOPA, respectively, as well as 1H-perfluorohexane (1H-PFHx) and 1H-perfluorooctane (1H-PFO), which were regulated by cytochrome P450 in wheat root. As a result, exposure to PFPiAs in roots ultimately caused the accumulation of more persistent PFPAs in the above-ground parts of plants, raising concerns on their potential risks on human health.

A review of sources, multimedia distribution and health risks of novel fluorinated alternatives

Per- and polyfluoroalkyl substances (PFASs) are a class of emerging persistent organic pollutants (POPs). They are widely used in industrial and consumer applications. Due to their persistence, bioaccumulation, long-distance migration and toxicity, it is important to find new compounds that can replace PFASs. The present review investigated the sources, fates and environmental effects of alternative PFAS compounds using surveys have been conducted over the past several years. Concentrations of PFAS alternatives in various environmental media, as well as human tissues, are summarized based on the available data. The results showed that hexafluoropropylene oxide dimer (HFPO-DA), hexafluoropropylene trimer acids (HFPO-TA), and 6:2 chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) have become the dominant global perfluorinated pollutants. Currently, there are a few toxicity assessments of these novel fluorinated alternatives, showing that they have systemic multiple organ toxicities. PFAS alternatives exhibited comparable or even more serious potential toxicity than legacy PFASs, indicating that these fluorinated alternatives are also harmful to the environment. Therefore, these alternatives require additional toxicological studies to confirm whether they can be used for a long time.

Removal of F-53B as PFOS alternative in chrome plating wastewater by UV/Sulfite reduction

Chrome mist suppressants are key chemicals used in the chrome plating industry to reduce exposure of workers by inhalation to airborne chromic acid pollution. Perfluoroalkyl sulfonated compounds are excellent mist suppressants, thanks to their chemical stability and surface activity. Therefore, despite mounting evidence for their persistence, bioaccumulation and toxicity, it is likely that such chemicals will continue to be used for the foreseeable future because of their importance and lack of alternatives. The present study is aimed at assessing the feasibility of advanced reduction as an effective technology to treat chrome plating industry wastewater. In particular, wastewater containing a chlorinated polyfluorinated ether sulfonate (i.e. F-53B), an alternative to perfluorooctanesulfonate (PFOS) used to prepare chrome mist suppressant in China, was treated by UV-activated sulfite. Results demonstrates that in ultrapure water F-53B can be easily degraded within 1 min-much faster than PFOS. Stoichiometric fluoride recovery was also achieved, confirming significant defluorination of the pollutant. Such superior reducibility was due to the presence of chlorine atoms, as corroborated by quantum chemical calculations. F-53B degradation was also achieved in chrome plating industrial wastewater, which yielded results were slower than those achieved in the laboratory nonetheless obtained complete abatement within 60 min. These results suggest that the proposed advanced reduction process is one of the safest options to control PFAS discharge in the environment and reduce the related risks to ecosystems.

Larval amphibians rapidly bioaccumulate poly- and perfluoroalkyl substances

Poly- and perfluoroalkyl substances (PFAS) are ubiquitous contaminants that can bioaccumulate in aquatic taxa. Amphibians are particularly vulnerable to contaminants and sensitive to endocrine disruptors during their aquatic larval stage. However, few studies have explored PFAS uptake rates in amphibians, which is critical for designing ecotoxicology studies and assessing the potential for bioaccumulation. Uptake rates of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were measured for larval northern leopard frogs (Rana pipiens), American toads (Anaxyrus americanus), and eastern tiger salamanders (Ambystoma tigrinum) during a 240-h exposure to 10 and 1000 μg/L concentrations. We measured body burden and calculated bioconcentration factor (BCF) every 48 h during the experiments. For all species and exposures, body burdens often reached steady state within 48-96 h of exposure. Steady-state body burdens for PFOA and PFOS ranged from 3819 to 16,481 ng/g dry weight (BCF = 0.46-2.5) and 6955-489,958 ng/g dry weight (47-259 BCFs), respectively. Therefore, PFAS steady state occurs rapidly in the larval amphibians we studied and particularly for PFOS. This result reflects a high potential for PFAS trophic transfer because amphibians are often low in trophic position and are important prey for many aquatic and terrestrial species.

Comparative in Vitro and in Vivo Evaluation of the Estrogenic Effect of Hexafluoropropylene Oxide Homologues

As alternatives to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide (HFPO) homologues, including hexafluoropropylene oxide dimer acid (HFPO-DA), hexafluoropropylene oxide trimer acid (HFPO-TA), and hexafluoropropylene oxide tetramer acid (HFPO-TeA), have been used in the fluoropolymer industry for a long period of time. These compounds have attracted widespread attention in recent years due to their environmental ubiquity and high bioaccumulation capability, as well as their toxicity. In our study, we evaluated the potential estrogenic effects of HFPOs in comparison to PFOA by ligand binding, transcriptional activity, and in vivo assays. Fluorescence ligand binding assays showed that both HFPO-TA and HFPO-TeA exhibited higher binding affinity to estrogen receptor ligand binding domains (ER-LBDs) than PFOA, with 2.5- and 57.5-fold higher affinity to ERα-LBD and 2.6- and 41.8-fold higher affinity to ERβ-LBD, respectively, whereas HFPO-DA exhibited weaker binding affinity than PFOA. Unlike PFOA, HFPO-TA and HFPO-TeA exhibited antagonistic activity toward the ERs' signaling pathway, with HFPO-TeA displaying the strongest potency. In silico study revealed that while PFOA binds with ERs in a similar fashion as 17β-estradiol, the HFPOs display an antagonistic binding mode. Using a zebrafish model, we further found that exposure to HFPO homologues significantly altered the levels of sex steroid hormones and vitellogenin. In general, both in vivo and in vitro results indicate that HFPO homologues might exert higher estrogenic effects than PFOA.

Per- and polyfluoroalkyl substances (PFASs) in the blood of two colobine monkey species from China: Occurrence and exposure pathways

Per-/polyfluoroalkyl substances (PFASs), which are widely used in industrial and commercial products, have been identified as global and ubiquitous pollutants. Despite this, limited data are available regarding the impacts of PFAS exposure and intake in non-human primates. Here, we report for the first time on the occurrence of PFASs in the blood and dietary sources of two rare and endangered primate species, namely, the golden snub-nosed monkey (Rhinopithecus roxellana) and Francois' leaf monkey (Trachypithecus francoisi). Results showed that perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) were dominant and found at the highest proportions in the blood of both species at the four study sites. The ∑PFAS levels in blood samples from captive golden snub-nosed monkeys in Tongling Zoo (mean: 2.51 ng/mL) and Shanghai Wild Zoo (3.52 ng/mL) near urbanized areas were one order of magnitude higher than the levels in wild monkeys from Shennongjia Nature Reserve (0.27 ng/mL). Furthermore, significant age positive relationships for perfluorodecanoic acid (PFDA), perfluorooctane sulfonate (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonates (6:2 Cl-PFESA) were observed in both golden snub-nosed monkeys at Shanghai Wild Zoo and Francois' leaf monkeys at Wuzhou Breeding Center. In addition, PFAS levels in frequently consumed food and drinking water were analyzed for Francois' leaf monkeys. Results showed that tree leaves accounted for the highest percentage of total daily intake of PFASs, especially PFOA, thus highlighting tree leaf consumption as a primary PFAS exposure route for this species. Overall, however, dietary exposure to PFASs was of relatively low risk to Francois' leaf monkey health.

Chronic exposure to 6:2 chlorinated polyfluorinated ether sulfonate acid (F-53B) induced hepatotoxic effects in adult zebrafish and disrupted the PPAR signaling pathway in their offspring

As a Chinese-specific alternative to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (commercial name: F-53B) has been used in the metal plating industry for over 40 years. This prevalence of use has resulted in its subsequent detection within the environment, wildlife, and humans. Despite this, however, its hepatotoxic effects on aquatic organisms remain unclear. Here, we characterized the impacts of long-term F-53B exposure on adult zebrafish liver and their offspring. Results showed that the concentration of F-53B was greater in the F0 liver than that in the gonads and blood. Furthermore, males had significantly higher liver F-53B levels than females. Hepatomegaly and obvious cytoplasmic vacuolation indicated that F-53B exposure induced liver injury. Compared to control, liver triglyceride levels decreased by 30% and 33.5% in the 5 and 50 μg/L-exposed males and 22% in 50 μg/L-exposed females. Liver transcriptome analysis of F0 adult fish found 2175 and 1267 differentially expressed genes (DEGs) in the 5 μg/L-exposed males and females, respectively. Enrichment analyses further demonstrated that the effects of F-53B on hepatic transcripts were sex-dependent. Gene Ontology showed that most DEGs were involved in multicellular organism development in male fish, whereas in female fish, most DEGs were related to metabolic processes and gene expression. qRT-PCR analysis indicated that the PPAR signaling pathway likely contributed to F-53B-induced disruption of lipid metabolism in F0 adult fish. In F1 larvae (5 days post fertilization), the transcription of pparα increased, like that in F0 adult fish, but most target genes showed the opposite expression trends as their parents. Taken together, our research demonstrated chronic F-53B exposure adversely impacts zebrafish liver, with disruption of PPAR signaling pathway dependent on sex and developmental stage.

Parental exposure to 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) induced transgenerational thyroid hormone disruption in zebrafish

Although 6:2 chlorinated polyfluorinated ether sulfonate (F-53B), an alternative to perfluorooctanesulfonate (PFOS), has been regularly detected in different environmental matrices, information regarding its toxicity remains limited. To explore the transgenerational thyroid-disrupting capacity of F-53B, adult zebrafish (F0) were exposed to different concentrations of F-53B (0, 5, 50, or 500μg/L) for 180d, with their offspring (F1 and F2) subsequently reared in uncontaminated water. Thyroid disturbances were then examined in the three (F0, F1, and F2) generations. For F0 adult fish, thyroxine (T4) increased in both sexes after exposure to 50μg/LF-53B, whereas 3,5,3'-triiodothyronine (T3) decreased in all groups, except for 50μg/LF-53B-treated males. For F1 embryos, parental exposure resulted in F-53B transfer as well as an increase in T4 content. At 5days post-fertilization, the significant increase in T4 and decrease in T3 were accompanied by a decrease in body length, increase in mortality, and increase in uninflated posterior swim bladder occurrence in F1 larvae. Although thyroid hormone levels were not changed significantly in F1 adult fish or F2 offspring compared with the control, the transcription levels of several genes along the hypothalamus-pituitary-thyroid axis were significantly modified. Our study demonstrated that F-53B possesses transgenerational thyroid-disrupting capability in zebrafish, indicating it might not be a safer alternative to PFOS.

Tissue-Specific Accumulation, Sexual Difference, and Maternal Transfer of Chlorinated Paraffins in Black-Spotted Frogs

The restriction on usage of short-chain chlorinated paraffins (SCCPs) under Stockholm Convention may promote the production and application of medium chain chlorinated paraffins (MCCPs) and long chain chlorinated paraffins (LCCPs) as substitutes. This study focused on the tissue-specific exposure to SCCPs, MCCPs, and LCCPs in black-spotted frog, a prevalent amphibian species in the Yangtze River Delta, China. The total CP concentrations in frog liver, muscle, and egg samples ranged of 35-1200, 6.3-97, and 6.8-300 ng/g wet weight (ww), respectively. Livers and eggs contained primary SCCPs (on average 78%) while MCCPs (43%) together with SCCPs (41%) were dominant in muscles. A significantly negative correlation was observed between hepatosomatic index and CPs concentration in liver ( p < 0.01), indicating that CP exposure may lower survival rates of frogs by suppressing the energy storage in liver. Additionally, maternal transfer, an important uptake pathway for CPs, was evaluated for the first time by calculating the ratios of CP levels in eggs to those in their paired liver tissues. The ratio of egg to liver for CP congener groups raised with the increasing of log K_ow values, indicating mother to egg transport of CPs was related to the lipophilicity of the chemicals.

Adipogenic Activity of Oligomeric Hexafluoropropylene Oxide (Perfluorooctanoic Acid Alternative) through Peroxisome Proliferator-Activated Receptor γ Pathway

Hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide dimer acid (HFPO-DA) have been used as perfluorooctanoic acid (PFOA) alternatives in the fluoropolymer industry for years. Their widespread environmental distribution, high bioaccumulation capability, and human exposure have caused great concern. Nevertheless, their potential toxicity and health risk remain largely unknown. In the present study, we compared potential disruption effects of HFPO-TA, HFPO-DA, and PFOA on peroxisome proliferator-activated receptor γ (PPARγ) via the investigation of receptor binding, receptor activity, and cell adipogenesis effects. The receptor binding experiment showed HFPO-TA exhibited 4.8-7.5 folds higher binding affinity with PPARγ than PFOA, whereas HFPO-DA exhibited weaker binding affinity than PFOA. They also showed agonistic activity toward PPARγ signaling pathway in HEK 293 cells in the order of HFPO-TA > PFOA > HFPO-DA. Molecular docking simulation indicated HFPO-TA formed more hydrogen bonds than PFOA, whereas HFPO-DA formed fewer hydrogen bonds than PFOA. HFPO-TA promoted adipogenic differentiation and lipid accumulation in both mouse and human preadipocytes with potency higher than PFOA. Adipogenesis in human preadipocytes is a more sensitive end point than mouse preadipocytes. Collectively, HFPO-TA exerts higher binding affinity, agonistic activity, and adipogenesis activity than PFOA. The potential health risk of HFPO-TA should be of concern.

Fate of Per- and Polyfluoroalkyl Ether Acids in the Total Oxidizable Precursor Assay and Implications for the Analysis of Impacted Water

Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. The PFAS class includes almost 5000 registered compounds, but analytical methods are lacking for most PFASs. The total oxidizable precursor (TOP) assay was developed to indirectly quantify unknown PFASs that are precursors to commonly measured perfluoroalkyl acids. To understand the behavior of recently identified per- and polyfluoroalkyl ether acids (PFEAs), including fluorinated replacements and manufacturing byproducts, we determined the fate of 15 PFEAs in the TOP assay. Ten perfluoroalkyl ether acids and a chlorinated polyfluoroalkyl ether acid (F-53B) were stable in the TOP assay and represent terminal products that are likely as persistent as historically used PFASs. Adding perfluoroalkyl ether acids and F-53B to the target analyte list for the TOP assay is recommended to capture a higher percentage of the total PFAS concentration in environmental samples. In contrast, polyfluoroalkyl ether acids with a -O-CFH- moiety were oxidized, typically to products that could not be identified by liquid chromatography and high-resolution mass spectrometry. Application of the TOP assay in its proposed enhanced form revealed high levels of PFEAs, the presence of precursors that form perfluoroalkyl carboxylic acids, and the absence of precursors that form PFEAs in surface water impacted by PFAS-containing wastewater discharges.

Two-generational reproductive toxicity assessment of 6:2 chlorinated polyfluorinated ether sulfonate (F-53B, a novel alternative to perfluorooctane sulfonate) in zebrafish

As an alternative to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (commercial name: F-53B) has been used in the Chinese chrome plating industry for over four decades. It has been increasingly detected in environmental matrices in recent years, causing great concern regarding its potential health risks to humans and wildlife. However, its adverse effects on biota remain largely unknown. To explore the chronic toxicity of F-53B on reproduction, a two-generational study was conducted using zebrafish (Danio rerio). Adult zebrafish (F0 generation) were chronically exposed to different concentrations of F-53B (0, 5, 50, and 500 μg/L) for 180 d using a flow-through exposure system, with F1 and F2 generations reared without exposure. The reproductive toxicity endpoints were assessed in F0 and F1 adult fish. Results showed that F-53B accumulated in the F0 gonads and transferred to the F1 generation via maternal eggs, and even remained in F1 adult fish and their eggs (F2) after 180 d depuration. In the F0 generation, F-53B exposure significantly inhibited growth and induced reproductive toxicity, including decreased gonadosomatic index and egg production/female, changes in the histological structure of the gonads, and increased serum testosterone levels. In particular, serum estradiol and vitellogenin levels were significantly increased in 5 μg/L F-53B-exposed adult males. The transcriptional levels of several genes along the hypothalamic-pituitary-gonadal axis were altered in F0 generation fish. Testis transcriptome analysis revealed that F-53B exposure disrupted spermatogenesis in F0 male zebrafish. Maternal transfer of F-53B also induced adverse effects on growth and reproduction in the F1 generation. Furthermore, the higher occurrence of malformation and lower survival in F1 and F2 embryos indicated that parental exposure to F-53B could impair the embryonic development of offspring. Taken together, this study demonstrated that F-53B could induce reproductive toxicity in zebrafish similar to that induced by legacy PFOS, and its potential adverse effects on offspring deserve further investigation.

Subchronic Hepatotoxicity Effects of 6:2 Chlorinated Polyfluorinated Ether Sulfonate (6:2 Cl-PFESA), a Novel Perfluorooctanesulfonate (PFOS) Alternative, on Adult Male Mice

The compound 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), an alternative to perfluorooctanesulfonate (PFOS) in the metal-plating industry, has been widely detected in various environmental matrices. However, its hepatotoxicity has yet to be clarified. Here, male mice were exposed to 0.04, 0.2, or 1 mg/kg/day of 6:2 Cl-PFESA for 56 days. Results demonstrated that relative liver weight increased significantly in the 0.2 and 1 mg/kg/day 6:2 Cl-PFESA groups, whereas liver lipid accumulation increased in all 6:2 Cl-PFESA groups. Serum enzyme activities of alanine transaminase and alkaline phosphatase were increased. Serum triglycerides and low-density lipoprotein cholesterol both increased, whereas serum total cholesterol and high-density lipoprotein cholesterol decreased following 6:2 Cl-PFESA exposure. A total of 264 differentially expressed proteins (127 up-regulated and 137 down-regulated), mainly involved in lipid metabolism, xenobiotic metabolism, and ribosome biogenesis, were identified by quantitative proteomics. Bioinformatics analysis highlighted the de-regulation of PPAR and PXR, which may contribute to the hepatotoxicity of 6:2 Cl-PFESA. Additionally, 6:2 Cl-PFESA induced both cell apoptosis and proliferation in the mouse liver. Compared to the overt toxicity of PFOS, 6:2 Cl-PFESA exhibited more-serious hepatotoxicity. Thus, caution should be exercised in the application of 6:2 Cl-PFESA as a replacement alternative to PFOS in industrial areas.

Developmental Toxicity of Perfluorooctanesulfonate (PFOS) and Its Chlorinated Polyfluoroalkyl Ether Sulfonate Alternative F-53B in the Domestic Chicken

The chlorinated polyfluoroalkyl ether sulfonate F-53B is used as a mist suppressant in the Chinese electroplating industry. Because of the regulations on perfluorooctanesulfonate (PFOS), its use is expected to increase. Until now, F-53B toxicity data have been scarce and are, to our knowledge, lacking for birds. This study therefore investigated the effects of PFOS and F-53B, separately and as mixtures, on the development of the chicken ( Gallus gallus domesticus). Compounds were injected in ovo, before incubation, at 150 and 1500 ng/g egg. At embryonic day 20, a significantly lower heart rate was observed in all treated groups compared to the control group and hatchlings exposed to the high dose of F-53B had a significantly enlarged liver (8%). Embryonic survival was not affected and no significant effects on hatchling body mass or oxidative stress parameters were found. Our results suggest that these compounds likely have different toxicity thresholds for the investigated endpoints, and/or different modes of action. This study thereby underlines the potential developmental toxicity of PFOS and F-53B at environmentally relevant concentrations. Assessment of PFOS alternatives should therefore continue, preferably prior to their large scale use, as they should be ensured to be less harmful than PFOS itself.

Degradation of PFOA Substitute: GenX (HFPO-DA Ammonium Salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite?

Hexafluoropropylene oxide dimer acid (HFPO-DA, ammonium salt with trade name: GenX) has been recently detected in river water worldwide. There are significant concerns about its persistence, and potential adverse effects to the biota. In this study, the degradability of GenX by typical advanced redox technologies (UV/persulfate and UV/sulfate) is investigated. Results demonstrate that <5% GenX is oxidized after 3 h in UV/persulfate system, which is much lower than ∼27% for PFOA. In comparison, GenX can be readily degraded and defluorinated by hydrated electron (e_aq^-) generated by UV/sulfite system. Specifically, GenX is not detectable after 2 h, and >90% of fluoride ion is recovered 6 h later. This is attributed to the accumulation and subsequent degradation of CF₃CF₂COOH and CF₃COOH, which are stable intermediates of GenX degradation. Mechanistic investigations suggest that the etheric bond in the molecule is a favorable attack point for the e_aq^-. Such finding is corroborated by quantum chemical calculations. The side CF₃- at the α-carbon probably acts as an effective barrier that prevents GenX from being cleaved by SO₄^-• or OH• at its most sensible point (i.e. the carboxyl group). This study illustrates that reduction by UV/sulfite might be a promising technology to remove GenX from contaminated water.

Distribution, bioaccumulation and trophic transfer of chlorinated polyfluoroalkyl ether sulfonic acids in the marine food web of Bohai, China

Chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) caused great concerns recently as novel fluorinated alternatives. However, information on their bioconcentration, bioaccumulation and biomagnification in marine ecosystems is limited. In this study, 152 biological samples including invertebrates, fishes, seabirds and mammals collected from Bohai Sea of China were analyzed to investigate the residual level, spatial distribution, bioaccumulation and biomagnification of Cl-PFESAs. 6:2 Cl-PFESA was found in concentrations ranging from <MDL (method detection limit) to 3.84 ng/g ww and it is the dominant congener when compared with concentrations of 8:2 Cl-PFESA. Compared with other bays and regions, levels of 6:2 Cl-PFESA are relatively high in bivalves and fishes from Liaodong Bay. These levels were also found to tend to increase as compared with those in 2010-2014. Logarithm bioaccumulation factors (BAFs) for 6:2 Cl-PFESA ranged from 2.23 to 4.21, implying the bioaccumulation of this compound. The trophic magnification factor (BMF) for 6:2 Cl-PFESA was determined to be 3.37 in the marine food web, indicating biomagnification potential along the marine food chain.

Sorption, Aerobic Biodegradation, and Oxidation Potential of PFOS Alternatives Chlorinated Polyfluoroalkyl Ether Sulfonic Acids

Global phase out of perfluorooctanesulfonic acid (PFOS) has led to increasing production of alternatives such as the chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) for which little is known on their environmental fate. In this study, sorption by soils, aerobic soil biodegradation, and oxidation potential of 6:2 Cl-PFESA (9-chlorohexadecafluoro-3-oxanonane-1-sulfonate) and 8:2 Cl-PFESA (9-chlorooctadecafluoro-3-oxanonane-1-sulfonate) were evaluated. 6:2 Cl-PFESA sorption was quantified for aqueous and acetone/water solutions, whereas 8:2 PFESA could only be accurately measured in acetone/water solutions. The log-linear cosolvency model was applied and validated to estimate sorption of 8:2 Cl-PFESA. Only soil organic carbon (OC, 0.76-4.30%) was highly and positively correlated to sorption of the Cl-PFESAs ( R² > 0.96). The resulting log K_oc values (OC-normalized sorption coefficients) are 4.01 ± 0.09 ( n = 6) and 5.54 ± 0.05 ( n = 4) L kg^-1 for 6:2 Cl-PFESA and 8:2 Cl-PFESA, respectively. Aerobic biodegradation in a loam soil at 24 ± 0.5 °C showed negligible degradation of both Cl-PFESAs. Cl-PFESAs also remained unchanged in an unbuffered heat (50 °C)-activated 42 mM persulfate oxidation treatment. Therefore, Cl-PFESAs are equally recalcitrant as PFOS in addition to being more sorptive, thus with a higher bioaccumulation potential for a similar alkyl chain length.

Hepatotoxic Effects of Hexafluoropropylene Oxide Trimer Acid (HFPO-TA), A Novel Perfluorooctanoic Acid (PFOA) Alternative, on Mice

As an alternative to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been increasingly used for fluoropolymer manufacture in recent years. Its growing detection in environmental matrices and wildlife raises considerable concern about its potential health risks. Here we investigated the effects of HFPO-TA on mouse liver following 28 days of exposure to 0.02, 0.1, or 0.5 mg/kg/d of HFPO-TA via oral gavage. Results showed that HFPO-TA concentrations increased to 1.14, 4.48, and 30.8 μg/mL in serum and 12.0, 32.2, and 100 μg/g in liver, respectively. Liver injury, including hepatomegaly, necrosis, and increase in alanine aminotransferase activity, was observed. Furthermore, total cholesterol and triglycerides decreased in the liver in a dose-dependent manner. Liver transcriptome analysis revealed that 281, 1001, and 2491 genes were differentially expressed (fold change ≥2 and FDR < 0.05) in the three treated groups, respectively, compared with the control group. KEGG enrichment analysis highlighted the PPAR and chemical carcinogenesis pathways in all three treatment groups. Protein levels of genes involved in carcinogenesis, such as AFP, p21, Sirt1 C-MYC, and PCNA, were significantly increased. Compared with previously published toxicological data of PFOA, HFPO-TA showed higher bioaccumulation potential and more serious hepatotoxicity. Taken together, HFPO-TA does not appear to be a safer alternative to PFOA.

Worldwide Distribution of Novel Perfluoroether Carboxylic and Sulfonic Acids in Surface Water

Driven by increasingly stringent restrictions on long-chain per- and polyfluoroalkyl substances (PFASs), novel fluorinated compounds have emerged on the market. Here we report on the occurrences of several perfluoroalkyl ether carboxylic and sulfonic acids (PFECAs and PFESAs), including hexafluoropropylene oxide dimer and trimer acids (HFPO-DA and HFPO-TA), ammonium 4,8-dioxa-3 H-perfluorononanoate (ADONA), chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA), and its hydrogen-substituted analogue (6:2 H-PFESA) in surface waters from China ( n = 106), the United States ( n = 12), the United Kingdom ( n = 6), Sweden ( n = 10), Germany ( n = 14), The Netherlands ( n = 6), and Korea ( n = 6). Results showed that HFPO-DA, HFPO-TA, and 6:2 Cl-PFESA (median = 0.95, 0.21, and 0.31 ng/L, respectively) were frequently detected in all countries, indicating ubiquitous dispersal and distribution in global surface waters. The presence of 6:2 H-PFESA was widely detected in China (detection rate > 95%) but not in any other country. Only trace levels of ADONA (0.013-1.5 ng/L) were detected in the Rhine River flowing through Germany. The estimated total riverine mass discharges of HFPO-DA, HFPO-TA, and ΣPFESAs reached 2.6, 6.0, and 4.3 ton/year in five of the major river systems in China. Our results indicated that novel PFECAs and PFESAs might become global contaminants, and future investigations are warranted.