In Vivo and in Vitro Isomer-Specific Biotransformation of Perfluorooctane Sulfonamide in Common Carp (Cyprinus carpio)

Transformation of 6:6 PFPiA in the gut of Xenopus laevis: Synergistic effects of CYP450 enzymes and gut microflora

As a frequently detected per- and polyfluoroalkyl substance in the environment, 6:6 perfluoroalkylhypophosphinic acid (6:6 PFPiA) is vulnerable to transformation in the liver of organisms, but the transformation in gut is still unclear. This study investigates the molecular mechanisms of 6:6 PFPiA transformation in the gut of Xenopus laevis upon a 28-day exposure in water. Before Day 16, a notable correlation (p = 0.03) was observed between the transformation product (PFHxPA) and cytochrome P450 (CYP450) enzyme concentration in gut. This suggests that CYP450 enzymes played an important role in the transformation of 6:6 PFPiA in the gut, which was verified by an in vitro incubation with gut tissues, and supported by the molecular docking results of 6:6 PFPiA binding with CYP450 enzymes. From the day 16, the CYP450 concentration in gut decreased by 31.3 % due to the damage caused by 6:6 PFPiA, leading to a decrease in the transformation capacity in gut, but the transformation rate was stronger than in liver. This was in contrast with the in vitro experiment, where transformation was stronger in liver. In the mean time, the abundance of Bacteroidota in gut increased, which released hydrolytic enzyme and then could participate in the transformation as well. This study reveals the potential of the gut in metabolizing environmental pollutants, and provides profound insights into the potential health risks caused by 6:6 PFPiA in organisms.

Fluorine mass balance analysis in wild boar organs from the Bohemian Forest National Park

Wild boars have been reported as bioindicators for per- and polyfluoroalkyl substances (PFAS) in a variety of studies. However, data about PFAS levels in wild boars from sites with limited industrial and general human activity is scarce. In this study, wild boar (Sus scrofa) organs from the Bohemian Forest National Park (Czech Republic) were used as bioindicators for PFAS pollution. In this work, 29 livers and 24 kidneys from 30 wild boars (0.5-5 years) were investigated using a fluorine mass balance approach. For this, the samples were measured using high performance liquid chromatography with electrospray ionisation tandem mass spectrometry (HPLC-ESI-MS/MS), targeting 30 PFAS, including legacy and replacement PFAS, direct total oxidisable precursor assay (dTOPA) and combustion ion chromatography (CIC). Perfluorocarboxylic acids (PFCAs) from C7 to C14 and perfluorooctanesulfonic acid (PFOS) were detected in >50 % of samples. In the livers, PFCAs dominated the profile with median concentrations of 230 μg/kg for perfluorononanoic acid (PFNA) and 75 μg/kg perfluorooctanoic acid (PFOA). PFOA and PFNA concentrations in the livers were one order of magnitude higher than in livers from wild boars caught in rural NE Germany considered as background concentration. PFOS in liver contributed only 30 % to the Σc(PFASTarget) with a median concentration of 170 μg/kg. Kidneys and livers contain an average of 2460 μg F/kg and 6800 μg F/kg extractable organic fluorine (EOF) respectively. Σc(PFASTarget) add up to a maximum of 10 % of the extractable organic fluorine. After oxidisation of the samples, PFOA, PFNA and Σc(PFASdTOPA) increased in livers, but could not explain the EOF. The elevated concentration of PFOA and PFNA may indicate differences in biomagnification for different habitats or an unidentified PFAS source in proximity to the national park.

Bioaccumulation of Perfluoroalkyl Sulfonamides (FASA)

Hundreds of sites across the United States have high concentrations of perfluoroalkyl sulfonamides (FASA), but little is known about their propensity to accumulate in fish. FASA are precursors to terminal per- and polyfluoroalkyl substances (PFAS) that are abundant in diverse consumer products and aqueous film-forming foams manufactured using electrochemical fluorination (ECF AFFF). In this study, FASA with C3-C8 carbon chain lengths were detected in all fish samples from surface waters up to 8 km downstream of source zones with ECF AFFF contamination. Short-chain FASA ≤ C6 have rarely been included in routine screening for PFAS, but availability of new standards makes such analyses more feasible. Bioaccumulation factors (BAF) for FASA were between 1 and 3 orders of magnitude greater than their terminal perfluoroalkyl sulfonates. Across fish species, BAF for FASA were greater than for perfluorooctanesulfonate (PFOS), which is presently the focus of national advisory programs. Similar concentrations of the C6 FASA (<0.36-175 ng g-1) and PFOS (0.65-222 ng g-1) were detected in all fish species. No safety thresholds have been established for FASA. However, high concentrations in fish next to contaminated sites and preliminary findings on toxicity suggest an urgent need for consideration by fish advisory programs.

Hepatotoxic response of perfluorooctane sulfonamide (PFOSA) in early life stage zebrafish (Danio rerio) is greater than perfluorooctane sulfonate (PFOS)

Perfluorooctane sulfonamide (PFOSA), a typical perfluorooctane sulfonate precursor (PreFOS), has been detected in the aquatic environment globally. However, the effects of PFOSA at levels measured in the environment have not been well characterized in aquatic organisms. In this study, we evaluated the transcriptional, biochemical, histopathological, and morphological effects of PFOSA to characterize the underlying mechanisms of toxicity by using a universal model in aquatic ecotoxicology, zebrafish (Danio rerio). Transcriptional changes in PFOSA-exposed zebrafish predicted hepatic fibrosis and associated immune function. Subsequent, sublethal impacts were observed, which included significant alterations in liver-specific protein levels, increased immune cell numbers, and liver pathological structural damage. In addition, we compared the effects caused by PFOSA and perfluorooctane sulfonate (PFOS) at the same exposure concentration and found a greater hepatotoxic effect of PFOSA relative to PFOS, indicating that the adverse impacts of PFOSA may be more severe. This was the first study to comparatively explore the hepatotoxic response of PFOSA and PFOS in aquatic organisms, which can be used for ecological risk assessments of PreFOS compounds.

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

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

Differences in the internal PFAS patterns of herbivores, omnivores and carnivores - lessons learned from target screening and the total oxidizable precursor assay

Per- and polyfluorinated alkyl substances (PFAS) are a group of anthropogenic chemicals, which are not (fully) biodegradable and accumulate in different environmental compartments worldwide. A comprehensive, quantitative analysis - consisting of target analysis (66 different analytes, including e. g. ultrashort-chain perfluorinated carboxylic acids (PFCAs), precursor compounds and novel substitutes) and the Total Oxidisable Precursor (TOP) assay (including trifluoroacetic acid (TFA)) - were conducted to analyse the PFAS concentrations and patterns in 12 mammalian and two bird species from different areas of Germany and Denmark. The PFAS contamination was investigated in dependance of the trophic class (herbivores, omnivores, carnivores), ecological habitat (terrestrial, (semi-) aquatic) and body tissue (liver, musculature). PFAS concentrations were highest in carnivores, followed by omnivores and herbivores, with ∑PFAS concentration ranging from 1274 μg/kg (Eurasian otter liver) to 22 μg/kg (roe deer liver). TFA dominated in the herbivorous species, whereas perfluorooctanesulfonic acid (PFOS) and the long-chain PFCAs covered the majority of the PFAS contamination in carnivorous species. Besides trophic class, ecological habitat also affected the PFAS levels in the different species, with terrestrial herbivores and omnivores showing higher PFAS concentration than their aquatic counterparts, whereas for carnivores this relationship was reversed. The TOP assay analysis indicated similar trends, with the PFCA formation pattern differing significantly between the trophic classes. TFA was formed predominantly in herbivorous and omnivorous species, whereas in carnivorous species a broad spectrum of PFCAs (chain-length C2-C14) was formed. Musculature tissue of six species exhibited significantly lower PFAS concentrations than the respective liver tissue, but with similar PFAS patterns. The comprehensive approach applied in the present study showed, that primarily the trophic class is decisive for the PFAS concentration, as herbivores, omnivores and carnivores clearly differed in their PFAS concentrations and patterns. Additionally, the TOP assay gave novel insights in the PFCA formation potential in biota samples.

Transport and transformation of perfluoroalkyl acids, isomer profiles, novel alternatives and unknown precursors from factories to dinner plates in China: New insights into crop bioaccumulation prediction and risk assessment

Perfluoroalkyl acids (PFAAs) are contaminants of global concern, and the inadvertent consumption of PFAA-contaminated crops may pose a threat to public health. Therefore, systematically studying their source tracing, bioaccumulation prediction and risk assessments in crops is an urgent priority. This study investigated the source apportionment and transport of PFAAs and novel fluorinated alternatives (collectively as per- and polyfluoroalkyl substances, PFASs) from factories to agricultural fields in a fluorochemical industrial region of China. Furthermore, bioaccumulation specificities and prediction of these chemicals in different vegetables were explored, followed by a comprehensive risk assessment from agricultural fields to dinner plates which considered precursor degradation. A positive matrix factorization model revealed that approximately 70 % of PFASs in agricultural soils were derived from fluorochemical manufacturing and metal processing. Alarming levels of ∑PFASs ranged 8.28-84.3 ng/g in soils and 163-7176 ng/g in vegetables. PFAS with short carbon chain or carboxylic acid group as well as branched isomers exhibited higher environmental transport potentials and bioaccumulation factors (BAFs) across a range of vegetables. The BAFs of different isomers of perfluorooctanoic acid (PFOA) decreased as the perfluoromethyl group moved further from the acid functional group. Hexafluoropropylene oxide dimer acid (GenX) showed relatively low BAFs, probably related to its ether bond with a high affinity to soil. Vegetables with fewer Casparian strips (e.g., carrot and radish), or more protein, possessed larger BAFs of PFASs. A bioaccumulation equation integrating critical parameters of PFASs, vegetables and soils, was built and corroborated with a good contamination prediction. After a total oxidizable precursors (TOP) assay, incremental perfluoroalkyl carboxylic acids (PFCAs) were massively found (325-5940 ng/g) in edible vegetable parts. Besides, precursor degradation and volatilization loss of PFASs was firstly confirmed during vegetable cooking. A risk assessment based on the TOP assay was developed to assist the protection of vegetable consumers.

Major biotransformation of phthalic acid esters in Eisenia fetida: Mechanistic insights and association with catalytic enzymes and intestinal symbionts

Phthalic acid esters (PAEs) are an important group of organic pollutants that are widely used as plasticizers in the environment. The PAEs in soil organisms are likely to be biotransformed into a variety of metabolites, and the combined toxicity of PAEs and their metabolites might be more serious than PAEs alone. However, there are only a few studies on PAE biotransformation by terrestrial animals, e.g. earthworms. Herein, the key biotransformation pathways of PAEs and their association with catalytic enzymes and intestinal symbionts in earthworms were studied using in vivo and in vitro incubation approaches. The widely distributed PAE in soil, dibutyl phthalate (DBP), was proven to be biotransformed rapidly together with apparent bioaccumulation in earthworms. The biotransformation of PAE congeners with medium or long side chains appeared to be faster compared with those with short side chains. DBP was biotransformed into butyl methyl phthalate (BMP), monobutyl phthalate (MBP), and phthalic acid (PA) through esterolysis and transesterification. Besides, the generation of small quantities of low-molecular weight metabolites via β-oxidation, decarboxylation or ring-cleavage, was also observed, especially when the appropriate proportion of NADPH coenzyme was applied to transfer electrons for oxidases. Interestingly, the esterolysis of PAEs was mainly regulated by the cytoplasmic carboxylesterase (CarE) in earthworms, with a Michaelis constant (K_m) of 0.416 mM in the catalysis of DBP. The stronger esterolysis in non-intestinal tissues indicated that the CarE was primarily secreted by non-intestinal tissues of earthworms. Additionally, the intestinal symbiotic bacteria of earthworms could respond to PAE stress, leading to the changes in their diversity and composition. The enrichment of some genera e.g. Bacillus and Paracoccus, and the enhancement of metabolism function, e.g. amino acids, energy, lipids biosynthesis and oxidase secretion, indicated their important role in the degradation of PAEs.

Bioaccumulation and biomagnification of emerging poly- and perfluoroalkyl substances in marine organisms

Accumulating evidence has demonstrated the wide environmental presence of 6:2 chlorinated polyfluoroalkyl ether sulfonates (6:2 Cl-PFAES) and p-perfluorous nonenoxybenzene sulfonate (PFNOBS). However, data on the bioaccumulation and trophic magnification of these emerging poly- and perfluoroalkyl substances (PFASs) in subtropical marine environment is still limited. In this study, seawater (n = 17), sediment (n = 14), and marine organism (27 species; n = 177) samples were collected from East China Sea, and analyzed them for legacy and emerging PFASs. Besides perfluoroalkyl carboxylates and perfluorooctane sulfonate (PFOS), 6:2 Cl-PFAES was always among the predominant PFASs detected in seawater, sediment, and marine organism. For emerging PFASs, 6:2 Cl-PFAES (mean ± SD, 3.1 ± 0.17), 8:2 Cl-PFAES (3.3 ± 0.35), and PFNOBS (3.3 ± 0.19) had lower bioaccumulation factors (BAF) than PFOS (3.4 ± 0.22) in marine fish. In crab, PFNOBS (3.7 ± 0.33) had a lower biota-sediment accumulation factor (BSAF) than PFOS (3.9 ± 0.45). In snail, among all detected PFASs, PFNOBS (4.0 ± 0.42) had the highest mean log BSAF value. 8:2 Cl-PFAES consistently had a higher log BSAF value than 6:2 Cl-PFAES in snail and crab. Notably, these differences in BAF and BSAF are not significant. Among PFASs, 6:2 Cl-PFAES (2.3; 95 % confidence interval, CI: 1.9-2.6) displayed the highest trophic magnification factor (TMF). PFNOBS had the lowest TMF value (1.8, 95 % CI: 1.4-2.1), but which still indicates its weak biomagnification through the current marine food web. This is the first study reporting the bioaccumulation and biomagnification of PFNOBS in marine organisms, which deepens the understanding of its environmental behavior in the marine ecosystem.

The Need for Testing Isomer Profiles of Perfluoroalkyl Substances to Evaluate Treatment Processes

Many environmentally relevant poly-/perfluoroalkyl substances (PFASs) including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) exist in different isomeric (branched and linear) forms in the natural environment. The isomeric distribution of PFASs in the environment and source waters is largely controlled by the source of contamination and varying physicochemical properties imparted by their structural differences. For example, branched isomers of PFOS are relatively more reactive and less sorptive compared to the linear analogue. As a result, the removal of branched and linear PFASs during water treatment can vary, and thus the isomeric distribution in source waters can influence the overall efficiency of the treatment process. In this paper, we highlight the need to consider the isomeric distribution of PFASs in contaminated matrices while designing appropriate remediation strategies. We additionally summarize the known occurrence and variation in the physicochemical properties of PFAS isomers influencing their detection, fate, toxicokinetics, and treatment efficiency.

A review of omics-based PFAS exposure studies reveals common biochemical response pathways

Per and Polyfluoroalkyl Substances (PFAS) are a diverse group of man-made chemicals with a range of industrial applications and which are widespread in the environment. They are structurally diverse but comprise a common chemical feature of at least one (though usually more) perfluorocarbon moiety (-C_nF_2n-) attached to a functional group such as a carboxylic or sulphonic acid. The strength of the Carbon-Fluorine bond means the compounds do not break down easily and can thus bioaccumulate. PFAS are of high concern to regulators and the public due to their potential toxicity and high persistence. At high exposure levels, PFAS have been implicated in a range of harmful effects on human and environmental health, particularly problems in/with development, cholesterol and endocrine disruption, immune system function, and oncogenesis. However, most environmental toxicology studies use far higher levels of PFAS than are generally found in the environment. Additionally, since the type of exposure, the PFAS used, and the organisms tested all vary between studies, so do the results. Traditional ecotoxicology studies may thus not identify PFAS effects at environmentally relevant exposures. Here we conduct a review of omics-based PFAS exposure studies using laboratory ecotoxicological methodologies and environmentally relevant exposure levels and show that common biochemical response pathways are identified in multiple studies. A major pathway identified was the pentose phosphate shunt pathway. Such molecular markers of sublethal PFAS exposure will greatly benefit accurate and effective risk assessments to ensure that new PFAS regulations can consider the full effects of PFAS exposure on environmental and human health receptors.

Concentration-dependent toxicokinetics of novel PFOS alternatives and their chronic combined toxicity in adult zebrafish

The increasing use of perfluorooctanesulfonate (PFOS) alternatives has led to their release into the aquatic environment. This study sought to determine the effects of exposure concentration on the toxicokinetics of PFOS and its alternatives, including perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), chlorinated polyfluorinated ether sulfonate (F-53B) and sodium p-perfluorous nonenoxybenzenesulfonate (OBS) in adult zebrafish by exposure to mixtures of the five per- and polyfluoroalkyl substances (PFAS) at 1, 10, and 100 ng/mL for 28-day, followed by a 14-day depuration. PFAS predominantly accumulated in the blood and liver, and the bioconcentration factor (BCF) decreased in the order of F-53B > PFOS > OBS ≫ PFHxS > PFBS in whole-fish homogenates. The uptake rate constants and BCF of the short-chain PFAS (≤C6) positively correlated with increasing exposure concentration, while the long-chain PFAS (≥C8) exhibited a pattern of first increasing and then decreasing. A consistent increase in the elimination rate constants of short- and long-chain PFAS was observed with increasing exposure concentration. All PFAS form tight conformations with ZSA and ZL-FABP via hydrogen bonding as revealed by molecular docking analysis. Furthermore, chronic combined exposure to PFAS induced the occurrence of vacuolation and oxidative stress in the zebrafish liver. Our findings uniquely inform the concentration-dependent bioconcentration potential and health risks to aquatic organisms of these PFOS alternatives in the environment.

Simulation modelling the structure related bioaccumulation and biomagnification of per- and polyfluoroalkyl substances in aquatic food web

Until now, there is no bioaccumulation model to predict bioaccumulation of polyfluoroalkyl substances (PFASs) in aquatic organisms due to their unique amphiphilic properties. For the first time, protein contents instead of lipid contents of organisms were used in bioaccumulation models to predict the concentrations and reveal the accumulation mechanisms of PFASs in various aquatic organisms, based on the available data. Comparison between the modeled and measured results indicated the models were promising to predict the PFAS concentrations in the fishes at different trophic levels very well, as well as their bioaccumulation factors (BAF) and trophic magnification factors (TMF) of PFASs in fish. Both water and sediment are important exposure sources of PFASs in aquatic organisms. As the two main uptake pathways, the contribution of gill respiratory decreases while that of dietary intake increases with the chain length of PFASs increasing. Fecal excretion and gill respiration are the main pathways for fish to eliminate PFASs, and their relative contributions increase and decrease respectively with chain length. The short-chain (C6-C8) perfluoroalkyl acids (PFAAs) are greatly eliminated via gill respiratory quickly, leading to their very low BAFs. As the carbon chain length increases, dietary intake becomes dominant in the uptake, while elimination is mainly through fecal excretion with relatively low rates, especially in the fishes with high protein contents. For the very long chain (C12-C16) PFASs, they are very difficult to excrete with a low total elimination rate constant (k_e = 0.463-0.743 d^-1), thus leading to their high BAFs and TMFs. The high intake rate but low elimination rate, as well as the high water and sediment concentrations together contribute to the highest accumulated concentration perfluorooctane sulfonic acid in the fish of Taihu Lake.

Perfluorooctane Sulfonamide (PFOSA) Induces Cardiotoxicity via Aryl Hydrocarbon Receptor Activation in Zebrafish

Perfluorooctane sulfonamide (PFOSA), a precursor of perfluorooctanesulfonate (PFOS), is widely used during industrial processes, though little is known about its toxicity, particularly to early life stage organisms that are generally sensitive to xenobiotic exposure. Here, following exposure to concentrations of 0.01, 0.1, 1, 10, and 100 μg/L PFOSA, transcriptional, morphological, physiological, and biochemical assays were used to evaluate the potential effects on aquatic organisms. The top Tox functions in exposed zebrafish were related to cardiac diseases predicted by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and Ingenuity Pathway Analysis (IPA) analysis. Consistent with impacts predicted by transcriptional changes, abnormal cardiac morphology, disordered heartbeat signals, as well as reduced heart rate and cardiac output were observed following the exposure of 0.1, 1, 10, or 100 μg/L PFOSA. Furthermore, these PFOSA-induced cardiac effects were either prevented or alleviated by supplementation with an aryl hydrocarbon receptor (AHR) antagonist or ahr2-morpholino knock-down, uncovering a seminal role of AHR in PFOSA-induced cardiotoxicity. Our results provide the first evidence in fish that PFOSA can impair proper heart development and function and raises concern for PFOSA analogues in the natural environment.

Exposure pathways and bioaccumulation of per- and polyfluoroalkyl substances in freshwater aquatic ecosystems: Key considerations

Due to the bioaccumulative behavior, toxicity, and recalcitrance to degradation, per- and polyfluoroalkyl substances (PFAS) are a focus for many researchers investigating freshwater aquatic ecosystems. PFAS are a diverse set of chemicals that accumulate and transport quite differently in the environment depending on the length of their fluoroalkyl chains and their functional groups. This diversity in PFAS chemical characteristics combined with varying environmental factors also impact the bioaccumulation of these compounds in different organisms. In this review, we evaluate environmental factors (such as organic carbon, proteins, lipids, and dissolved cations) as well as PFAS characteristics (head group, chain-length, and concentration) that contribute to the significant variation seen in the literature of bioaccumulation metrics reported for organisms in aquatic ecosystems. Of the factors evaluated, it was found that PFAS concentration, dissolved organic matter, sediment organic matter, and biotransformation of precursor PFAS tended to significantly impact reported bioaccumulation metrics the most. Based on this review, it is highly suggested that future studies provide sufficient details of important environmental factors, specific organism traits/ behavior, and PFAS concentrations/compounds when reporting on bioaccumulation metrics to further fill data gaps and improve our understanding of PFAS in aquatic ecosystems.

Bioavailability and trophic magnification of antibiotics in aquatic food webs of Pearl River, China: Influence of physicochemical characteristics and biotransformation

Information on trophodynamics of antibiotics and subsequent relationships to antibiotic metabolism in river ecosystem is still unavailable, limiting the evaluation of their bioaccumulation and trophodynamics in aquatic food webs. In the present study, concentrations and relative abundance of 11 antibiotics were investigated in surface water, sediment and 22 aquatic taxa (e.g., fish, invertebrates and plankton) from Pearl River, South China. The logarithmic bioaccumulation factors (log BAFs) of antibiotics generally showed positive relationships with their log D (pH-adjusted log Kow), implying that their bioaccumulation of ionizable antibiotics depends on it is in an ionized form. Higher BAFs of antibiotics in benthic biota were observed than those in fish, indicating that sediment ingestion was a possible route of antibiotic exposure. The logarithmic biota-sediment accumulation factors (log BSAFs) of benthic biota increased when log D increased from -4.79 to -0.01, but declined thereafter. Trophodynamics of antibiotics was investigated, and intrinsic clearance were measured in liver microsomes of Tilapia zillii (trophic level [TL]: 2.5), Anabas testudineu (TL: 3.9), and Coilia grayi (TL: 5.0). Only ciprofloxacin (CFX) showed significant trophic magnification (Trophic Magnification Factor [TMF] = 1.95), and a higher metabolism rate in lower trophic levels suggest that metabolic biotransformation play a significant role in driving biomagnification of antibiotics.

Determinants of serum half-lives for linear and branched perfluoroalkyl substances after long-term high exposure-A study in Ronneby, Sweden

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are persistent substances with surfactant and repellent properties. Municipal drinking water contaminated with PFAS had been distributed for decades to one third of households in Ronneby, Sweden. The source was firefighting foam used in a nearby airfield since the mid-1980s. Clean water was provided from December 16, 2013.

AIMS

The purpose was to estimate serum half-lives and their determinants in the study population for different PFAS.

METHODS

Up to ten blood samples were collected between 2014 and 2018 from 114 participants (age 4-84 years at entry, 53% female). 19 PFAS were analysed. Linear mixed models were used to estimate the half-lives.

RESULTS

Eight PFAS were increased in Ronneby: perfluorooctanoic acid (PFOA), perfluoropentane sulfonate (PFPeS), perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS), linear perfluorooctane sulfonate (L-PFOS) and three branched perfluorooctane sulfonates (1 m-PFOS, 3/4/5m-PFOS and 2/6m-PFOS). The mean estimated half-lives (in years) were 0.94 (95 %CI 0.86-1.02) for PFPeS, 2.47 (2.27-2.7) for PFOA, 2.67 (2.51-2.85) for 2/6m-PFOS, 2.73 (2.55-2.92) for L-PFOS, 3.43 (3.19-3.71) for 3/4/5m-PFOS, 4.52 (4.14-4.99) for PFHxS, 4.55 (4.14-5.06) for PFHpS, and 5.01 (4.56-5.55) for 1 m-PFOS. The most important determinants of a shorter half-life were young age, and better kidney function measured by estimated glomerular filtration rate and ratio of paired urine and serum PFAS levels, followed by female sex during their fertile period aged 15-50. Markers of gut inflammation and reduced permeability i.e. zonulin and calprotectin were also possibly associated with shorter half-life. The results also suggested a time-dependent PFAS elimination process, with more rapid elimination in the first year after the end of exposure.

CONCLUSION

The half-life estimates are in line with past estimates for some PFAS such as PFOA, and the novel results for different PFOS isomers. These results provide observational support for elimination routes - renal, fecal and maternal.

Novel Brominated Flame Retardants (NBFRs) in a Tropical Marine Food Web from the South China Sea: The Influence of Hydrophobicity and Biotransformation on Structure-Related Trophodynamics

The increasing discharge and ubiquitous occurrence of novel brominated flame retardants (NBFRs) in aquatic environments have initiated intense global concerns; however, little information is available regarding their structure-related trophodynamics in marine food webs. In this study, a tropical marine food web including 29 species (18 fish and 11 invertebrate species) was collected from coral reef waters of the Xisha Islands, the South China Sea, for an analysis of 11 representative NBFRs. The mean ∑NBFR concentrations generally increased in the following sequence: sea cucumbers (0.330 ng/g lw) < crabs (0.380 ng/g lw) < shells (2.10 ng/g lw) < herbivorous fishes (2.30 ng/g lw) < carnivorous fishes (4.13 ng/g lw), with decabromodiphenyl ethane (DBDPE) and hexabromobenzene (HBB) as the predominant components. Trophic magnification was observed for all of the investigated NBFRs, with trophic magnification factors (TMFs) ranging from 1.53 (tetrabromobisphenol A bis(dibromopropyl ether)) to 5.32 (HBB). Significant negative correlations were also found between the TMFs and the tested in vitro transformation clearance rates (CL_in vitro) for the target NBFRs except for bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (TBPH) (p < 0.05). Multiple linear regression analysis confirmed that the transformation rate is a more powerful predictor for TMFs than the hydrophobicity of NBFRs in this marine food web.

Evaluation of single and joint toxicity of perfluorooctanoic acid and arsenite to earthworm (Eisenia fetida): A multi-biomarker approach

Perfluorooctanoic acid (PFOA) and arsenic are ubiquitous environmental contaminants and could co-exist in soil. However, data on their possible combined toxic effects on terrestrial organisms are still lacking. In this study, we exposed earthworm Eisenia fetida to artificial soil spiked with different sub-lethal levels of PFOA, arsenite (As(III)) or their mixture for 28 days. The bioaccumulation and multi-biomarker responses in the earthworms were measured. Results showed that the co-existence of PFOA and As(III) in soil enhanced the bioaccumulation of arsenic while reduced the bioaccumulation of PFOA. Most selected biomarkers exhibited significant responses at higher exposure levels and indicated oxidative damages. Biomarker Response Index (BRI) was used to integrate the multi-biomarker responses and the results showed significant dose-effect relationships between biological health status and exposure levels. Moreover, variation analysis of multi-biomarkers and BRI proved that As(III) exhibited more toxicity than PFOA to the earthworms. Based on BRI results, Effect Addition Index (EAI) was calculated to evaluate the joint effects of the two toxicants. According to EAI, the joint toxicity of PFOA and As(III) was related to exposure concentration, changing from synergism to slight antagonism with the increase of exposure level. These results provide valuable toxicological information for the risk assessment of co-exposure to PFOA and arsenic in the soil environment. Moreover, this study proved that BRI is an effective tool to integrate multi-biomarker responses, and its combination with EAI provides a useful combined approach to evaluate the joint effects of mixed contamination systems.

A review of PFAS fingerprints in fish from Norwegian freshwater bodies subject to different source inputs

The extensive use of per- and polyfluorinated alkyl substances (PFAS) has resulted in many environmental point and diffuse sources. Identifying the source responsible for a pollution hot spot is vital for assessing remediation measures, however, as there are many possible sources of environmental PFAS pollution, this can be challenging. Chemical fingerprinting has been proposed as an approach to identify contamination sources. Here, concentrations and profiles (relative distribution profiles) of routinely targeted PFAS in freshwater fish from eight sites in Norway, representing three different sources: (1) production of paper products, (2) the use of aqueous film forming foams (AFFF), and (3) long-range atmospheric transport, were investigated. The data were retrieved from published studies. Results showed that fingerprinting of PFAS in fish can be used to identify the dominant exposure source(s), and the profiles associated with the different sources were described in detail. Based on the results, the liver was concluded to be better suited for source tracking compared to muscle. PFAS fingerprints originating from AFFF were dominated by perfluorooctanesulfonate (PFOS) and other perfluoroalkanesulfonic acids (PFSA). Fingerprints originating from both long-range atmospheric transport and production of paper products were associated with high percentages of long chained perfluoroalkyl carboxylic acids (PFCA). However, there were differences between the two latter sources with respect to the ∑PFAS concentrations and ratios of specific PFCA pairs (PFUnDA/PFDA and PFTrDA/PFDoDA). Low ∑PFAS concentrations were detected in fish exposed mainly to PFAS via long-range atmospheric transport. In contrast, ∑PFAS concentrations were high and high percentages of PFOS were detected in fish exposed to pollution from production of paper products. The source-specific fingerprints described here can be used for source tracking.

Potency Ranking of Per- and Polyfluoroalkyl Substances Using High-Throughput Transcriptomic Analysis of Human Liver Spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (ie, benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in 3 subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7-10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

Potency Ranking of Per- and Polyfluoroalkyl Substances Using High-Throughput Transcriptomic Analysis of Human Liver Spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (ie, benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in 3 subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7-10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

6:2 Cl-PFESA has the potential to cause liver damage and induce lipid metabolism disorders in female mice through the action of PPAR-γ

6:2 Cl-PFESA is a polyfluoroalkyl ether with high environmental persistence that has been confirmed to have significant adverse effects on animals. In this study, 6-week-old female C57BL/6 mice were exposed to 0, 1, 3 and 10 μg/L 6:2 Cl-PFESA for 10 weeks to estimate the hepatotoxicity of 6:2 Cl-PFESA and explore its underlying molecular mechanism. The results indicated that 6:2 Cl-PFESA preferentially bioaccumulated in the liver and induced hepatic cytoplasmic vacuolation and hepatomegaly in mice. In addition, serum metabolic profiling showed that 6:2 Cl-PFESA exposure caused an abnormal increase in amino acids and an abnormal decrease in acyl-carnitine, which interfered with fatty acid transport and increased the risk of metabolic diseases. Further experiments showed that 6:2 Cl-PFESA formed more hydrogen bonds with PPAR-γ than PFOS, Rosi and GW9662, and the binding affinity of 6:2 Cl-PFESA toward PPAR-γ was the highest among the ligands. 6:2 Cl-PFESA promoted the differentiation of 3T3-L1 cells by increasing PPAR-γ expression. Therefore, our results showed that 6:2 Cl-PFESA has the potential to induce liver damage and dysfunction in female mice, and this effect was achieved through PPAR-γ. This study is the first to reveal the hepatic toxicity of 6:2 Cl-PFESA in female mammals and provides new insights for subsequent in-depth research.

A Roadmap to the Structure-Related Metabolism Pathways of Per- and Polyfluoroalkyl Substances in the Early Life Stages of Zebrafish (Danio rerio)

BACKGROUND

Thousands of per- and polyfluoroalkyl substances (PFAS) with diverse structures have been detected in the ambient environment. Apart from a few well-studied PFAS, the structure-related toxicokinetics of a broader set of PFAS remain unclear.

OBJECTIVES

To understand the toxicokinetics of PFAS, we attempted to characterize the metabolism pathways of 74 structurally diverse PFAS samples from the U.S. Environmental Protection Agency's PFAS screening library.

METHODS

Using the early life stages of zebrafish (Danio rerio) as a model, we determined the bioconcentration factors and phenotypic toxicities of 74 PFAS. Then, we applied high-resolution mass spectrometry-based nontargeted analysis to identify metabolites of PFAS in zebrafish larvae after 5 d of exposure by incorporating retention time and mass spectra. In vitro enzymatic activity experiments with human recombinant liver carboxylesterase (hCES1) were employed to validate the structure-related hydrolysis of 11 selected PFAS.

RESULTS

Our findings identified five structural categories of PFAS prone to metabolism. The metabolism pathways of PFAS were highly related to their structures as exemplified by fluorotelomer alcohols that the predominance of β-oxidation or taurine conjugation pathways were primarily determined by the number of hydrocarbons. Hydrolysis was identified as a major metabolism pathway for diverse PFAS, and perfluoroalkyl carboxamides showed the highest in vivo hydrolysis rates, followed by carboxyesters and sulfonamides. The hydrolysis of PFAS was verified with recombinant hCES1, with strong substrate preferences toward perfluoroalkyl carboxamides.

CONCLUSIONS

We suggest that the roadmap of the structure-related metabolism pathways of PFAS established in this study would provide a starting point to inform the potential health risks of other PFAS. https://doi.org/10.1289/EHP7169.

Associations between serum isomers of perfluoroalkyl acids and metabolic syndrome in adults: Isomers of C8 Health Project in China

BACKGROUND

Exposure to perfluoroalkyl acids (PFAAs) is known to be associated with metabolic disorders. However, whether PFAAs isomers are associated with metabolic syndrome (MetS) still remains unknown.

OBJECTIVES

To explore the associations between serum PFAAs isomers and MetS.

METHODS

We recruited 1,501 adults from a cross-sectional study, the "Isomers of C8 Health Project in China" to investigate the associations between PFAAs isomers and MetS. A total of 20 PFAAs including the isomers of PFOS and PFOA were detected. Logistic regression models and restricted cubic spline models were used to evaluate the relationship of serum PFAAs isomers exposure with MetS and its components as well after adjusting for covariates.

RESULTS

The MetS prevalence in our study was 43.0%. The serum levels of both PFOS and PFOA isomers were higher in participants with MetS than that with non-MetS (p < 0.05). We found positive associations for per natural log-transformed ng/mL of branched perfluorooctane sulfonate (br-PFOS) (odds ratio (OR) = 1.18, 95% confidence interval (CI): 1.01, 1.38)) linear perfluoronanoic acid (n-PFOA) (OR = 1.35, 95% CI: 1.16, 1.58) and perfluoro-6-methylpheptanoic acid (6 m-PFOA) (OR = 1.32, 95% CI: 1.11, 1.57) with higher odds of MetS after covariates adjustment, while null association was observed for linear isomers of PFOS (OR = 1.09, 95% CI: 0.94, 1.25). We found a nonlinear dose-response relationship with a "threshold" effect in serum br-PFOS isomers with MetS, in which the odds of MetS increased quickly with increasing serum br-PFOS isomers under low exposure (p for nonlinearity = 0.030).

CONCLUSION

We report new evidence of associations between PFAAs isomers and MetS and the nonlinearity of dose-response relationship with br-PFOS isomers. Our findings indicate that more attention is needed to pay on the nonlinearity of dose-response relationship when investigate the association of PFAAs isomers with human health.

Biotransformation of perfluoroalkyl acid precursors from various environmental systems: advances and perspectives

Perfluoroalkyl acids (PFAAs) are widely used in industrial production and daily life because of their unique physicochemical properties, such as their hydrophobicity, oleophobicity, surface activity, and thermal stability. Perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) are the most studied PFAAs due to their global occurrence. PFAAs are environmentally persistent, toxic, and the long-chain homologs are also bioaccumulative. Exposure to PFAAs may arise directly from emission or indirectly via the environmental release and degradation of PFAA precursors. Precursors themselves or their conversion intermediates can present deleterious effects, including hepatotoxicity, reproductive toxicity, developmental toxicity, and genetic toxicity. Therefore, exposure to PFAA precursors constitutes a potential hazard for environmental contamination. In order to comprehensively evaluate the environmental fate and effects of PFAA precursors and their connection with PFSAs and PFCAs, we review environmental biodegradability studies carried out with microbial strains, activated sludge, plants, and earthworms over the past decade. In particular, we review perfluorooctyl-sulfonamide-based precursors, including perfluroooctane sulfonamide (FOSA) and its N-ethyl derivative (EtFOSA), N-ethyl perfluorooctane sulfonamido ethanol (EtFOSE), and EtFOSE-based phosphate diester (DiSAmPAP). Fluorotelomerization-based precursors are also reviewed, including fluorotelomer alcohols (FTOH), fluorotelomer sulfonates (FTSA), and a suite of their transformation products. Though limited information is currently available on zwitterionic PFAS precursors, a preliminary review of data available for 6:2 fluorotelomer sulfonamide betaine (FTAB) was also conducted. Furthermore, we update and refine the recent knowledge on biotransformation strategies with a focus on metabolic pathways and mechanisms involved in the biotransformation of PFAA precursors. The biotransformation of PFAA precursors mainly involves the cleavage of carbon-fluorine (C-F) bonds and the degradation of non-fluorinated functional groups via oxidation, dealkylation, and defluorination to form shorter-chained PFAAs. Based on the existing research, the current problems and future research directions on the biotransformation of PFAA precursors are proposed.

Prenatal exposure and transplacental transfer of perfluoroalkyl substance isomers in participants from the upper and lower reaches of the Yangtze River

Data on gestational exposure characteristics and transplacental transfer are quite limited for perfluoroalkyl substance (PFAS) isomers, especially those from large-scale comparative studies. To fill this gap, we examined isomers of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in matched maternal and cord serum from Mianyang and Hangzhou, which are located in the upper and lower reaches of the Yangtze River, China, respectively. These data were compared with those from our previous study on Wuhan in the middle reach. The average ΣPFAS concentration increased from upstream to downstream (Mianyang (4.44 ng/mL) < Wuhan (9.88 ng/mL) < Hangzhou (19.72 ng/mL)) and may be related to the per capita consumption expenditure of each city. The ln-transformed PFAS concentrations showed significant differences between Mianyang and Hangzhou after adjusting confounding factors (p < 0.05). The percentages of linear PFOS and PFOA in maternal and cord serum from these cities all exceeded those in electrochemical fluorination products. The isomer profiles of PFASs in maternal and cord serum might be greatly influenced by local production processes of PFASs and residents' dietary habits. The transplacental transfer efficiencies decreased significantly with increasing concentrations in maternal serum for ΣPFAS, ΣPFOS, ΣPFOA, ΣPFHxS, n-PFOS, iso-PFOS, 4m-PFOS, 1m-PFOS, n-PFOA, n-PFHxS, and br-PFHxS (Spearman rank correlation coefficients (r) = 0.373-0.687, p < 0.01). These findings support an understanding of the regional characteristics in maternal exposure to PFASs along the Yangtze River, isomeric profiles of PFASs in these regions, and the transplacental transfer processes of PFAS isomers.

Tissue distribution and bioaccumulation of legacy and emerging per-and polyfluoroalkyl substances (PFASs) in edible fishes from Taihu Lake, China

Tissue distribution of legacy and emerging per-and polyfluoroalkyl substances (PFASs) in several kinds of edible fishes collected from Meiliang bay of Taihu Lake, China were investigated and the related human health risks were assessed. Perfluorooctanesulfonate (PFOS), perfluorooctanesulfonamide (PFOSA) and 6:2 fluorotelomer phosphate diester (6:2 diPAP) were the most abundant legacy perfluoroalkyl acid (PFAA), PFOS related precursor (PreFOS), and the emerging PFASs in all fish tissues, respectively. Similar to the legacy PFAAs, 6:2 diPAP and 6:6 perfluorophosphinate (6:6 PFPiA) had the highest levels in the fish liver, whereas the highest level of PFOSA was in kidney, which might be due to its intensive transformation in fish liver. The concentrations of PFASs were generally positively correlated with the trophic levels. The profiles of PFASs were significantly different among bitterling, crucian and other fish, which might be related to their different metabolic capacities. Bioaccumulation factors (BAFs) of PreFOSs, 6:2 diPAP, and 6:6 PFPiA were lower than those of PFAAs with the same number of perfluorinated carbons. The calculated hazard ratios (HR) of PFOS (Range: 0.0100-0.655) and perfluorooctanoic acid (PFOA) (<0.00200) in all fish muscles were less than 1.0. However, the HR of the ∑PFASs in crucian muscle was 1.04, which implied that frequent consumption of crucian collected from Meiliang Bay might pose potential risks to human health.

Paper product production identified as the main source of per- and polyfluoroalkyl substances (PFAS) in a Norwegian lake: Source and historic emission tracking

The entirety of the sediment bed in lake Tyrifjorden, Norway, is contaminated by per- and polyfluoroalkyl substances (PFAS). A factory producing paper products and a fire station were investigated as possible sources. Fire station emissions were dominated by the eight carbon perfluoroalkyl sulfonic acid (PFSA), perfluorooctanesulfonic acid (PFOS), from aqueous film forming foams. Factory emissions contained PFOS, PFOS precursors (preFOS and SAmPAP), long chained fluorotelomer sulfonates (FTS), and perfluoroalkyl carboxylic acids (PFCA). Concentrations and profiles in sediments and biota indicated that emissions originating from the factory were the main source of pollution in the lake, while no clear indication of fire station emissions was found. Ratios of linear-to branched-PFOS increased with distance from the factory, indicating that isomer profiles can be used to trace a point source. A dated sediment core contained higher concentrations in older sediments and indicated that two different PFAS products have been used at the factory, referred to here as Scotchban and FTS mixture. Modelling, based on the sediment concentrations, indicated that 42-189 tons Scotchban, and 2.4-15.6 tons FTS mixture, were emitted. Production of paper products may be a major PFAS point source, that has generally been overlooked. It is hypothesized that paper fibres released from such facilities are important vectors for PFAS transport in the aquatic environment.

Prioritisation of emerging contaminants in the northern Antarctic Peninsula based on their environmental risk

Although Antarctica is protected and human activity is restricted exclusively to scientific research, with numerous restrictions on tourism, the steadily increasing human presence appears to be having a marked impact on terrestrial and aquatic, especially marine, ecosystems. Evidence of this excessive presence can be seen from the recent detection of contaminants linked to human activity in locations that should be considered to be untouched. The aim of this study is to determine the environmental risk present on the Antarctic Peninsula due to the 54 emerging contaminants linked to human presence previously detected and reported in previous studies published in leading scientific journals. The substances analysed belong to the group of drugs/medicines of abuse, endocrine disruptors, pyrethroids, perfluorinated compounds and sunscreens. The environmental risk was determined for all substances detected by calculating the hazard quotient (HQ) following the guidelines established by the European Union. An HQ value higher than 10 was taken to represent a high environmental risk. In the group of drugs/medicines of abuse, a high risk was detected for two analgesics, namely acetaminophen and diclofenac, and the anti-inflammatory ibuprofen. Although the risk detected was considered to be medium, the presence of the antibiotic clarithromycin, one of the substances included in the EU's current watch list for emerging contaminants, should be noted. In the group of endocrine disruptors, the high risk posed by the metabolite nonylphenol diethoxylate, which is higher than that for its parent compound nonylphenol, should be noted. In the group of pyrethroids/sunscreens/perfluorinated compounds, two pyrethroids, namely bifenthrin and cyhalothrin, were found to pose a high environmental risk. We propose the need to establish a monitoring system for emerging contaminants linked to human presence on the Antarctic Peninsula similar to the watch list found in the EU Water Framework Directive. Subsequently, an environmental monitoring plan based on individual ecotoxicological studies with the substances concerned, and analysing their possible synergic effects, should be implemented.

Investigation of levels of perfluoroalkyl substances in surface water, sediment and fish tissue in New Jersey, USA

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative, and toxic substances found in New Jersey (NJ) due to historic and current industrial activities and the use of aqueous film forming foams. This research documents PFAS occurrence in surface water, sediments, and fish tissue at 11 targeted waterbodies in NJ suspected to be impacted by PFAS. Thirteen PFAS compounds were quantified from each media. The profile of detected PFAS differed among media from the same site, with shorter chain PFAS tending to predominate in surface water while longer chain PFAS predominated in fish and sediments. All water samples contained detectable levels of at least four perfluoroalkyl substances. PFOA, PFHpA and PFPeA were detected at every site. ΣPFAS concentrations in water samples ranged from 22.9 to 279.5 ng/L. At least one, and up to eight, PFAS were detected in sediment samples at 10 sites, while there were no detections of PFAS in sediments at the reference site. ΣPFAS concentrations in sediment samples ranged from below detection to 30.9 ng/g. At least one fish of each species at every site had detectable levels of PFAS compounds. ΣPFAS concentrations in fish were highest at sites downstream from a military facility, and lowest at the reference site. PFOS, PFDA, PFUnA and PFDoA were the predominant PFAS detected in fish tissue. PFOS was generally found in fish tissue at higher concentrations than other PFAS, with higher PFOS concentrations found in the tissue of yellow perch, American eel, pumpkinseed, and largemouth bass collected at sites with higher detections of PFOS in surface waters. PFOS levels in nearly all fish species were, on average, high enough to trigger fish consumption advisories. Additional studies are needed to further evaluate the sources and occurrence of PFAS in NJ and to better understand their movement through the environment and potential risks.

Tissue-specific bioaccumulation, metabolism and excretion of tris (2-ethylhexyl) phosphate (TEHP) in rare minnow (Gobiocyprisrarus)

Tris (2-ethylhexyl) phosphate (TEHP) is one of the most commonly used organophosphorus flame retardant (OPFR) analogues and is commonly detected in surface water and sediments. Limited information is available about the metabolic pathway or metabolite formation related to TEHP in fish. In this study, rare minnows (Gobiocyprisrarus) were exposed to TEHP in static water for 30 d to investigate the bioaccumulation and metabolite distribution in the fish muscle, liver, kidney, gill, GI-tract, ovary and testis. Based on the estimated k_up,_parent and k_d,parent values, the bioconcentration factors (BCF_parent) of TEHP in fish tissues were calculated in the order of kidney > ovary ≈ liver ≈ testis > gill ≈ GI-tract > muscle; this finding was consistent with the results of our previous study on other alkyl-substituted OPFRs. In addition, this study identified the metabolic profiles of TEHP in the liver. TEHP was oxidatively metabolized by the fish to a dealkylated metabolite (di 2-ethylhexyl phosphate; DEHP) and hydroxylated TEHP (OH-TEHP). OH-TEHP further underwent extensive phase II metabolism to yield glucuronic acid conjugates. DEHP was mainly distributed in rare minnow in the following order: liver > GI-tract > kidney ≫ other tissues. However, the metabolite showed lower accumulation potential in fish tissues than TEHP, with metabolite parent concentration factors (MPCFs) for DEHP of less than 0.1 in all the investigated tissues. The BCF_parent values of TEHP in various fish tissues were only 9.0 × 10^-3-7.2 × 10^-4 times its estimated tissue-water partition coefficient (K_tissue-water) values based on tissue lipid, protein and water contents, which indicated the significance of biotransformation in reducing the bioaccumulation potential of TEHP in fish. The toxicokinetic data in the present study help in understanding the tissue-specific bioaccumulation and metabolism pathways of TEHP in fish and highlight the importance of toxicology research on TEHP metabolites in aquatic organisms.

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.

Bioaccumulation of Novel Per- and Polyfluoroalkyl Substances in Mice Dosed with an Aqueous Film-Forming Foam

Per- and polyfluoroalkyl substances (PFASs) are widespread in the blood of the general human population, and their bioaccumulation is of considerable scientific and regulatory interest. PFAS exposure resulting from aqueous film-forming foam (AFFF) ingestion is poorly understood due to the complexity of AFFF mixtures and the presence of polyfluorinated substances that may undergo metabolic transformation. C57BL/6 mice were dosed with an AFFF primarily containing electrochemically fluorinated PFASs for 10 days, followed by a 6 day depuration. Urine was collected throughout the study and serum was collected post-depuration. Samples were analyzed via high-resolution mass spectrometry. Relative to the dosing solution, C6 and C7 perfluoroalkyl sulfonates (PFSAs) were enriched in dosed mouse serum, suggesting in vivo transformation of sulfonamide precursors. Some substituted C8 PFSAs [keto-perfluorooctane sulfonate (PFOS), hydrogen-PFOS, and unsaturated PFOS] appeared to be more bioaccumulative than linear PFOS, or were formed in vivo from unidentified precursors. A series of seven peaks in dosed mouse serum was tentatively identified as sulfonimide dimers that were either a minor component of the AFFF or were formed via metabolism of other AFFF components. This work highlights the importance of sulfonamide precursors in contributing to bioaccumulation of AFFF-associated PFSAs and identifies several classes of potentially bioaccumulative novel PFASs that warrant further investigation.

Probing Mechanisms for the Tissue-Specific Distribution and Biotransformation of Perfluoroalkyl Phosphinic Acids in Common Carp (Cyprinus carpio)

This study investigated the tissue-specific accumulation and biotransformation of 6:6 and 8:8 perfluoroalkyl phosphinic acids (PFPiA) in common carp (Cyprinus carpio) during 90 d exposure and 30 d depuration in water in the laboratory. Both 6:6 and 8:8 PFPiAs could quickly accumulate in the carp, and 6:6 PFPiA displayed higher bioaccumulation potential than 8:8 PFPiA. The highest concentrations of PFPiAs were observed in the blood, while the lowest were found in the muscle. The equilibrium dialysis experiment indicated that both PFPiAs had higher binding affinities with the proteins in the fish serum than in liver, which was supported by the molecular docking analysis. The results also indicated that 6:6 PFPiA had higher binding affinities with the serum and liver proteins than 8:8 PFPiA. These results suggested that the tissue-specific distribution of PFPiAs was highly dependent on the binding affinities with the specific proteins. Both in vivo and in vitro experiments consistently indicated that PFPiAs experienced biotransformation and produced perfluoroalkyl phosphonic acids (PFPAs), and biotransformation of 8:8 PFPiA was more active than 6:6 PFPiA. It was worth noting that perfluorohexanonate and perfluorooctanoic acids were identified in fish as metabolites after long-term exposure to PFPiAs for the first time.

Bioavailability and Bioaccumulation of 6:2 Fluorotelomer Sulfonate, 6:2 Chlorinated Polyfluoroalkyl Ether Sulfonates, and Perfluorophosphinates in a Soil-Plant System

As emerging alternatives of legacy perfluoroalkyl substances, 6:2 fluorotelomer sulfonate (6:2 FTS), 6:2 chlorinated polyfluoroalkyl ether sulfonates (6:2 Cl-PFESA), and perfluorophosphinates (C6/C6 and C8/C8 PFPiAs) are supposed to be partitioned to soil and highly persistent in the environment. The uptake of novel per- and polyfluoroalkyl substances (PFASs) by plants represents a potential pathway for their transfer in the food chain. In this study, the bioavailability of these four novel PFASs in soil and the bioaccumulation characteristics in greenhouse-grown wheat (Triticum aestivum L.), maize (Zea mays L.), soybean (Glycine max L. Merrill), and pumpkin (Cucurbita maxima L.) were investigated. The results indicated that these novel PFASs with higher hydrophobicity were more easily sequestrated in soil, and the fractions extracted by methanol could well describe their bioavailability, which could be stimulated by low-molecular-weight organic acids at rhizospheric concentrations. A negative relationship was found between root soil concentration factors (RSCFs) and hydrophobicity (log Kow) of the target PFASs. This correlation was also found in the translocation factors (TF) from roots to shoots. Furthermore, the uptake and transfer of the target PFASs were regulated by the protein contents in plant roots and shoots.

Toxicokinetics and bioaccumulation characteristics of bisphenol analogues in common carp (Cyprinus carpio)

Toxicokinetics and bioconcentration of eight common bisphenol analogues, including bisphenol A (BPA), -B, -C, -E, -S, -Z, -AF, and -AP in common carp (Cyprinus carpio) were investigated. Both free (BP_free) and total forms (BP_total) of the bisphenols were measured in various fish tissues. The conjugated forms of bisphenols were calculated based on BP_free and BP_total. The calculated bioconcentration factors (BCFs) based on the total bisphenols (BP_total) in the carp whole body were in the range of 0.3-320, agreeing with previous field results from Taihu Lake, China. The elimination rate constant (k_e) positively correlated with the fraction of conjugated form (f_conjugated), which displayed negative correlation with their log K_ow (r = -0.861, p < 0.05), indicating that conjugation facilitated their elimination and those with higher hydrophobicity were more difficult to be eliminated. Except BPA, the concentrations of all bisphenols in the carp tissues were in the order of kidney > liver ≫ muscle. The uptake rate constants (k_u) in kidney (r = 0.836, p < 0.05) and in liver (r = 0.863, p < 0.05) displayed significantly positive correlations with BCFs, and k_u in kidney was greater than in liver except BPA. These results indicated that kidney and liver played important roles in accumulating bisphenols in carp, and kidney made more contribution than liver for most bisphenols. Biliary excretion predominated for elimination of most bisphenols while BPA and BPS were mainly through urinary excretion.

Dietary Uptake and Depuration Kinetics of Perfluorooctane Sulfonate, Perfluorooctanoic Acid, and Hexafluoropropylene Oxide Dimer Acid (GenX) in a Benthic Fish

Per- and poly-fluoroalkyl substances (PFAS) are ubiquitously distributed throughout aquatic environments and can bioaccumulate in organisms. We examined dietary uptake and depuration of a mixture of 3 PFAS: perfluorooctanoic acid (PFOA; C₈ HF₁₅ O₂ ), perfluorooctane sulfonate (PFOS; C₈ HF₁₇ SO₃ ), and hexafluoropropylene oxide dimer acid (HPFO-DA; C₆ HF₁₁ O₃ ; trade name GenX). Benthic fish (blue spot gobies, Pseudogobius sp.) were fed contaminated food (nominal dose 500 ng g^-1 ) daily for a 21-d uptake period, followed by a 42-d depuration period. The compounds PFOA, linear-PFOS (linear PFOS), and total PFOS (sum of linear and branched PFOS) were detected in freeze-dried fish, whereas GenX was not, indicating either a lack of uptake or rapid elimination (<24 h). Depuration rates (d^-1 ) were 0.150 (PFOA), 0.045 (linear-PFOS), and 0.042 (linear+branched-PFOS) with corresponding biological half-lives of 5.9, 15, and 16 d, respectively. The PFOS isomers were eliminated differently, resulting in enrichment of linear-PFOS (70-90%) throughout the depuration period. The present study is the first reported study of GenX dietary bioaccumulation potential in fish, and the first dietary study to investigate uptake and depuration of multiple PFASs simultaneously, allowing us to determine that whereas PFOA and PFOS accumulated as expected, GenX, administered in the same way, did not appear to bioaccumulate. Environ Toxicol Chem 2020;39:595-603. © 2019 SETAC.

In vitro metabolism of pesticides and industrial chemicals in fish

Metabolism is one of the most important factors in controlling the toxicity and bioaccumulation of pesticides in fish. In vitro systems using subcellular fractions, cell lines, hepatocytes and tissues of a specific organ, each of which is characterized by usability, enzyme activity and chemical transport via membrane, have been applied to investigate the metabolic profiles of pesticides. Not only species and organs but also the fishkeeping conditions are known to greatly affect the in vitro metabolism of pesticides. A comparison of the metabolic profiles of pesticides and industrial chemicals taken under similar conditions has shown that in vitro systems using a subcellular S9 fraction and hepatocytes qualitatively reproduce many in vivo metabolic reactions. More investigation of these in vitro systems for pesticides is necessary to verify their applicability to the estimation of pesticide metabolism in fish.

Investigation of the Interaction Mechanism of Perfluoroalkyl Carboxylic Acids with Human Serum Albumin by Spectroscopic Methods

Perfluoroalkyl carboxylic acids (PFCAs) are some of the most significant pollutants in human serum, and are reported to be potentially toxic to humans. In this study, the binding mechanism of PFCAs with different carbon lengths to human serum albumin (HSA) was studied at the molecular level by means of fluorescence spectroscopy under simulated physiological conditions and molecular modeling. Fluorescence data indicate that PFCAs with a longer carbon chain have a stronger fluorescence quenching ability. Perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) had little effect on HSA. Fluorescence quenching of HSA by perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) was a static process that formed a PFCA-HSA complex. Electrostatic interactions were the main intermolecular forces between PFOA and HSA, while hydrogen bonding and van der Waals interactions played important roles in the combination of PFDA and HSA. In fact, the binding of PFDA to HSA was stronger than that of PFOA as supported by fluorescence quenching and molecular docking. In addition, infrared spectroscopy demonstrated that the binding of PFOA/PFDA resulted in a sharp decrease in the β-sheet and α-helix conformations of HSA. Our results indicated that the carbon chain length of PFCAs had a great impact on its binding affinity, and that PFCAs with longer carbon chains bound more strongly.

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.

First Report on In Vivo Pharmacokinetics and Biotransformation of Chlorinated Polyfluoroalkyl Ether Sulfonates in Rainbow Trout

This study provides the first in vivo pharmacokinetic data for chlorinated perfluorooctanesulfonate (Cl-PFOS), 6:2 and 8:2 chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs), upon a 30 day dietary exposure and 34 day depuration phase in rainbow trout (Oncorhynchus mykiss). Biological handling of these three novel molecules and legacy PFOS were investigated via cross-comparison. PFOS and Cl-PFOS displayed comparable bioaccumulative potencies and similar distribution tendencies in tissues (blood > liver > kidneys), despite the presence of a terminal chlorine atom in Cl-PFOS molecule. The Cl-PFESAs, especially 8:2 Cl-PFESA, were predominantly assimilated from the bloodstream by liver and kidneys and resisted elimination, leading to higher bioaccumulation factors in liver than in blood (0.576 and 0.254, respectively, for 8:2 Cl-PFESA) and longer half-lives in liver and kidneys than PFOS, suggesting these alternatives may pose greater risks in terms of the great accumulation potentials in fish tissues. The present study provides the first report of the in vivo transformation of 6:2 and 8:2 Cl-PFESAs and identifies 6:2 and 8:2 H-PFESAs as their respective sole metabolites. This provides the first line of evidence suggesting that the transformation susceptibility of Cl-PFESAs in organisms is distinct from their environmental persistence.

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.

High-content screening in zebrafish identifies perfluorooctanesulfonamide as a potent developmental toxicant

Per- and polyfluoroalkyl substances (PFASs) have been used for decades within industrial processes and consumer products, resulting in frequent detection within the environment. Using zebrafish embryos, we screened 38 PFASs for developmental toxicity and revealed that perfluorooctanesulfonamide (PFOSA) was the most potent developmental toxicant, resulting in elevated mortality and developmental abnormalities following exposure from 6 to 24 h post fertilization (hpf) and 6 to 72 hpf. PFOSA resulted in a concentration-dependent increase in mortality and abnormalities, with surviving embryos exhibiting a >12-h delay in development at 24 hpf. Exposures initiated at 0.75 hpf also resulted in a concentration-dependent delay in epiboly, although these effects were not driven by a specific sensitive window of development. We relied on mRNA-sequencing to identify the potential association of PFOSA-induced developmental delays with impacts on the embryonic transcriptome. Relative to stage-matched vehicle controls, these data revealed that pathways related to hepatotoxicity and lipid transport were disrupted in embryos exposed to PFOSA from 0.75 to 14 hpf and 0.75 to 24 hpf. Therefore, we measured liver area as well as neutral lipids in 128-hpf embryos exposed to vehicle (0.1% DMSO) or PFOSA from 0.75 to 24 hpf and clean water from 24 to 128 hpf, and showed that PFOSA exposure from 0.75 to 24 hpf resulted in a decrease in liver area and increase in yolk sac neutral lipids at 128 hpf. Overall, our findings show that early exposure to PFOSA adversely impacts embryogenesis, an effect that may lead to altered lipid transport and liver development.

Contributions of enzymes and gut microbes to biotransformation of perfluorooctane sulfonamide in earthworms (Eisenia fetida)

Perfluorooctane sulfonamide (FOSA) is known as a key intermediate of perfluorooctane sulfonic acid (PFOS) precursors, which can be frequently detected in the environment and biota. FOSA could be bioaccumulated in earthworms from soil, but the contributions of enzymes and gut microbes involved in the biotransformation of FOSA in earthworms have not been identified. Therefore, the effects of enzyme inhibitors and intestinal microflora on biotransformation of FOSA in earthworms were investigated in the present study. FOSA was biotransformed to form PFOS by earthworms obtained from in vivo and in vitro tests. The addition of FOSA had significantly positive effects on cytolchrome P450 (CYP450) and glutathione-s-transferase (GST) activities, suggesting CYP450 and GST are likely involved in the enzymatic transformation. In addition, both 1-Aminobenzotriazole (ABT) and ezatiostat hydrochloride (TLK199), which were selected to inhibit the CYP and GST enzymes, respectively, demonstrated inhibition effects on biotransformation of FOSA in earthworms with a dose-dependent relationship. However, the concentrations of FOSA weren't changed by the bacteria isolated from worm gut, suggesting that gut bacteria did not contribute to FOSA biotransformation in earthworms. The results of this study confirm that the transformation of FOSA in earthworms is mediated mainly by enzymes rather than by gut microbes.

Occurrence and source apportionment of novel and legacy poly/perfluoroalkyl substances in Hai River basin in China using receptor models and isomeric fingerprints

A variety of fluorinated alternatives are being manufactured and applied as a consequence of stringent regulations on legacy poly/perfluoroalkyl substances (PFASs). In this study, 26 emerging and legacy PFASs were measured in the surface water (including dissolved phase and suspended particulate matter) and sediments taken from Hai River basin, China. The total concentrations of PFASs (∑PFASs) ranged from 1.74 to 172 ng/L, with perfluorooctanonate (PFOA) as the dominant compound (15.2% of the ∑PFASs, median value). Emerging PFASs, such as dimer acid of hexafluoropropylene oxide dimer acid (HFPO-DA) and trimer acid (HFPO-TA), were widely detected in the water samples. Specifically, chlorinated polyfluorinated ether sulfonate (F-53B) was observed to be predominant in some sediment samples. A receptor model, Unmix, was introduced to identify the sources of PFASs in the surface water, and the results indicated that fire-fighting foam/fluoropolymer processing aids (36.6%) were the dominant source. The field-based sediment-water (organic carbon normalized) coefficients, K_oc, were correlated to the carbon chain lengths of the PFASs. A technique coupling one-way analysis of variance with chemical mass balance model was developed to trace the manufacturing sources of PFOA. Electrochemical fluorination (ECF) was the major PFOA manufacturing source with considerable contribution by telomerization. For the first time, the isomers of perfluorooctane sulfonamide (PFOSA) were quantified in the environmental samples. The lower proportion of branched (br-) PFOSA isomers and higher percentage of br-perfluorooctane sulfonate (PFOS) isomers in the water samples relative to their corresponding commercial products, provided more direct evidences that br-PFOSA isomers were biotransformed more easily than n-PFOSA, explaining the observed enrichment of br-PFOS in the aquatic environment.

Probing the hepatotoxicity mechanisms of novel chlorinated polyfluoroalkyl sulfonates to zebrafish larvae: Implication of structural specificity

Hepatotoxicity in zebrafish (Danio rerio) larvae elicited by legacy perfluorooctane sulfonate (PFOS) and its three novel chlorinated alternatives, including chlorinated polyfluorooctane sulfonate (Cl-PFOS) and chlorinated polyfluoroalkyl ether sulfonates (6:2 and 8:2 Cl-PFESA analogs), was evaluated in this study. Upon 7-day separate exposure to the four target compounds at 1 µmol/L, significant hepatic steatosis in exposed larvae was evidenced by pathological micro/macro vacuolation, which was presumably attributed to the excess accumulation of lipid, especially the overloaded triglyceride (TG) level. Disruption on gene transcription was subjected to a structure-dependent manner. In general, PFOS, Cl-PFOS and 6:2 Cl-PFESA of the identical carbon chain length (i.e. C8), despite with different substituents, displayed a similar activation mode and comparable disruptive potency on lipid metabolism responsive genes, which particularly promoted fatty acid synthesis (acetyl-CoA carboxylase, acacb) and β-oxidation (cytochrome P450 enzymes-1A, cyp1a; peroxisomal acyl-CoA oxidase 1, acox1; and acyl-CoA dehy-drogenase, acadm). However, 8:2 Cl-PFESA with a prolonged carbon chain length (i.e. C10), preferentially disturbed fatty acid exportation (apolipoprotein-B100, apob) and triggered a different modulation pattern on fatty acid β-oxidation against the other three compounds. Molecular docking analysis indicated that 8:2 Cl-PFESA exhibited considerably higher peroxisome proliferator-activated receptors (PPARs) antagonism than others, corresponding to its unique suppression effect on fatty acid β-oxidation responsive genes. To our knowledge, this is the first in vivo study reporting hepatotoxicity of Cl-PFOS and Cl-PFESAs to aquatic organisms. Although characterized with different toxic mode-of-action, these novel alternatives can elicit hepatic steatosis as strong as PFOS, stressing the biological risks in view of their global contamination.

PFOA and PFOS promote diabetic renal injury in vitro by impairing the metabolisms of amino acids and purines

BACKGROUND

Environmental pollutants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common surfactants in various consumer products. Epidemiological studies have demonstrated the association of diabetic kidney diseases with PFOA and PFOS. However, mechanisms of metabolic alterations involved are still unclear.

METHODS

Considering their involvement of glomerular hemodynamics, rat mesangial cells (MCs) are used as an in vitro model of diabetic kidney diseases for exposure to PFOS/PFOA under diabetic condition. Non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry were conducted to determine how PFOA/PFOS promoted fibrotic and proinflammatory responses in the MCs under diabetic condition.

RESULTS

Exposure of PFOA/PFOS (10 μM) increased oxidative stress and the levels of fibrotic and proinflammatory markers in MCs under diabetic condition. We demonstrated for the first time that PFOA and PFOS altered amino acid biosynthesis, citrate cycle, and purine metabolism in MCs under diabetic condition. Compared with diabetic condition, the exposure of PFOA and PFOS under diabetic condition more significantly altered the levels of 13 intracellular metabolites, including L-tyrosine, L-phenylalanine, L-arginine, L-tryptophan, AMP, ADP, UMP, inosine, and hypoxanthine, which have been reported to be related to kidney injury. In addition, PFOA/PFOS treatment significantly altered the expression levels of key enzymes involved in these metabolisms. Treatment with L-tyrosine, L-phenylalanine, L-arginine, and L-tryptophan reduced the levels of fibrotic and inflammatory markers induced by PFOA/PFOS.

CONCLUSION

Our results suggest that under diabetic condition, exposure of PFOA or PFOS aggravated diabetic kidney injury in vitro by impairing metabolisms of amino acids and purines to induce more fibrosis and inflammation in MCs.