Sub-chronic dietary toxicity of potassium perfluorooctanesulfonate in rats

Systemic and immunotoxicity induced by topical application of perfluoroheptane sulfonic acid (PFHpS) or perfluorooctane sulfonic acid (PFOS) in a murine model

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic surfactants of over 12,000 compounds that are incorporated into numerous products for their chemical and physical properties. Studies have associated PFAS with adverse health effects. Although there is a high potential for dermal exposure, these studies are lacking. The present study evaluated the systemic and immunotoxicity of subchronic 28- or 10-days of dermal exposure, respectively, to PFHpS (0.3125-2.5% or 7.82-62.5 mg/kg/dose) or PFOS (0.5% or 12.5 mg/kg/dose) in a murine model. Elevated levels of PFHpS were detected in the serum and urine, suggesting that absorption is occurring through the dermal route. PFHpS induced significantly increased relative liver weight, significantly decreased relative spleen and thymus weight, altered serum chemistries, and altered histopathology. Additionally, PFHpS significantly reduced the humoral immune response and altered immune subsets in the spleen, suggesting immunosuppression. Gene expression changes were observed in the liver, skin, and spleen of genes involved in fatty acid metabolism, necrosis, and inflammation. Immune-cell phenotyping identified significant decreases in B-cells and CD11b+ monocyte and/or macrophages in the spleen along with decreases in eosinophils and dendritic cells in the skin. These findings support PFHpS absorption through the skin leading to liver damage and immune suppression.

Spatial distribution, trophic magnification, and risk assessment of per- and polyfluoroalkyl substances in Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis): Risks of emerging alternatives

The Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is the only freshwater cetacean found in China. However, per- and polyfluoroalkyl substances (PFASs) risks in YFPs remain unclear. In this study, legacy PFASs, their precursors and alternatives, were determined in YFP muscles (n = 32), liver (n = 29), kidney (n = 24), skin (n = 5), and blubbers (n = 25) collected from Poyang Lake (PL) and Yangtze River (YR) between 2017 and 2023. Perfluorooctane sulfonic acid (PFOS) was the predominant PFAS in all YFP tissues, with a median hepatic concentration of 1700 ng/g wet weight, which is higher than that in other finless porpoises worldwide. PFOS, chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), and perfluoroalkane sulfonamides concentrations in YFP livers from PL were significantly higher than those from YR (p < 0.05); however, the opposite was observed for hexafluoropropylene oxide acids. Biomagnification and trophic magnification factors (BMF and TMF, respectively) of most PFASs in the YFP food web were > 1. Perfluoroheptane sulfonic acid had the highest BMF value (99), followed by 6:2 Cl-PFESA (94) and PFOS (81). The TMFmuscle and TMFliver values of the total PFASs were 3.4 and 6.6, respectively, and were significantly positively correlated with the fluorinated carbon chain length (p < 0.01). In addition, up to 62 % of the hazard quotients for 6:2 Cl-PFESA were > 1, which was higher than that of PFOS (48 %), suggesting a high hepatotoxicity of 6:2 Cl-PFESA to YFPs. Bioaccumulation and biotoxicity of legacy and emerging alternatives in aquatic organisms continue to be a concern, especially for underscoring the vulnerability of the long-lived and endangered species.

Transcriptomic re-analyses of human hepatocyte spheroids treated with PFAS reveals chain length and dose-dependent modes of action

To identify pathway perturbations and examine biological modes of action (MOAs) for various perfluoroalkyl substances, we re-analyzed published in vitro gene expression studies from human primary liver spheroids. With treatment times ranging from 10 to 14 days, shorter-chain PFAS (those with 6 or fewer fluorinated carbon atoms in the alkyl chain) showed enrichment for pathways of fatty acid metabolism and fatty acid beta-oxidation with upregulated genes. Longer-chain PFAS compounds, specifically PFOS (perfluorooctane sulfonate), PFDS (perfluorodecane sulfonate), and higher doses of PFOA (perfluorooctanoic acid), had enrichment for pathways involved in steroid metabolism, fatty acid metabolism, and biological oxidation for downregulated genes. Although PFNA (perfluorononanoic acid), PFDA (perfluorodecanoic acid), and PFUnDA (perfluoroundecanoic acid) were more toxic and could only be examined after a 1-day treatment, all three had enrichment patterns similar to those observed with PFOS. With PFOA there were dose-dependent changes in pathway enrichment, shifting from upregulation of fatty acid metabolism and downregulation of steroid metabolism to downregulation of both at higher doses. The response to PFHpS (perfluoroheptanesulfonic acid) was similar to the PFOA pattern at the lower treatment dose. Based on results of transcription factor binding sites analyses, we propose that downregulation of pathways of lipid metabolism by longer chain PFAS may be due to inhibitory interactions of PPARD on genes controlled by PPARA and PPARG. In conclusion, our transcriptomic analysis indicates that the biological MOAs of PFAS compounds differ according to chain length and dose, and that risk assessments for PFAS should consider these differences in biological MOAs when evaluating mixtures of these compounds.

Transcriptomic analysis of AHR wildtype and Knock-out rat livers supports TCDD's role in AHR/ARNT-mediated circadian disruption and hepatotoxicity

Single, high doses of TCDD in rats are known to cause wasting, a progressive loss of 30 to 50% body weight and death within several weeks. To identify pathway perturbations at or near doses causing wasting, we examined differentially gene expression (DGE) and pathway enrichment in centrilobular (CL) and periportal (PP) regions of female rat livers following 6 dose levels of TCDD - 0, 3, 22, 100, 300, and 1000 ng/kg/day, 5 days/week for 4 weeks. At the higher doses, rats lost weight, had increased liver/body weight ratios and nearly complete cessation of liver cell proliferation, signs consistent with wasting. DGE curves were left shifted for the CL versus the PP regions. Canonical Phase I and Phase II genes were maximally increased at lower doses and remained elevated at all doses. At lower doses, ≤ 22 ng/kg/day in the CL and ≤ 100 ng/kg/day, upregulated genes showed transcription factor (TF) enrichment for AHR and ARNT. At the mid- and high-dose doses, there was a large number of downregulated genes and pathway enrichment for DEGs which showed downregulation of many cellular metabolism processes including those for steroids, fatty acid metabolism, pyruvate metabolism and citric acid cycle. There was significant TF enrichment of the hi-dose downregulated genes for RXR, ESR1, LXR, PPARalpha. At the highest dose, there was also pathway enrichment with upregulated genes for extracellular matrix organization, collagen formation, hemostasis and innate immune system. TCDD demonstrates most of its effects through binding the aryl hydrocarbon receptor (AHR) while the downregulation of metabolism genes at higher TCDD doses is known to be independent of AHR binding to DREs. Based on our results with DEG, we provide a hypothesis for wasting in which high doses of TCDD shift circadian processes away from the resting state, leading to greatly reduced synthesis of steroids and complex lipids needed for cell growth, and producing gene expression signals consistent with an epithelial-to-mesenchymal transition in hepatocytes.

Accumulation features and temporal trends (2002-2015) for legacy and emerging per- and polyfluoroalkyl substances (PFASs) in finless porpoises bycaught off Korean coasts

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) were measured in livers of finless porpoises (Neophocaena asiaeorientalis; n = 167) collected in Korean waters from 2002 to 2015 to investigate their occurrence, bioaccumulation feature, temporal trends, and ecotoxicological implications. Perfulorooctane sulfonate (PFOS), perfluoroundecanoate (PFUnDA), and perfluorotridecanoate (PFTrDA) were the predominant PFASs found in the porpoises. The concentration of 6:2 chlorinated polyfluoroalkyl ether sulfonate (F-53B), an alternative to PFOS, was comparable to that of PFTrDA. Perfluorooctane sulfonamide (FOSA), a precursor of PFOS, was also detected in all the porpoises examined. All PFASs, including F-53B, accumulated to higher concentrations in immature porpoises compared with mature specimens, implying substantial maternal transfer and limited metabolizing capacity for PFASs. A significant correlation was observed between PFOS and F-53B concentrations, indicating similar bioaccumulation processes. Based on prenatal exposure and toxicity, F-53B is an emerging contaminant in marine ecosystems. Significantly increasing trends were observed in the concentrations of sulfonates, carboxylates, and F-53B between 2002/2003 and 2010, whereas the FOSA concentration significantly decreased. During 2010-2015, decreasing trends were observed in the concentrations of FOSA and sulfonates, whereas concentrations of carboxylate and F-53B increased without statistical significance, likely due to a gap for the implementation of regulatory actions between sulfonates and carboxylates. Although PFOS and PFOA were found to pose little health risk to porpoises, the combined toxicological effects of other contaminants should be considered to protect populations and to mitigate PFAS contamination in marine ecosystems.

Association between prenatal perfluorinated compounds exposure and risk of pregnancy complications: A meta-analysis

BACKGROUND AND OBJECTIVE

Per- and polyfluoroalkyl substances (PFASs) have been shown to be persistent and bioaccumulative. An elevated danger of pregnancy complications perhaps connected with exposure to PFASs, but the potential effects remain elusive. The objective of this study is to investigate the possible association between PFASs exposure and pregnancy complications, drawing upon existing evidence.

METHODS

Electronic databases of PubMed, Qvid Medline, Embase, and Web of Science were searched thoroughly to identify eligible research published prior to November 28, 2023, examining the relationship between PFASs and pregnancy-related complications. To evaluate the quality of observational studies incorporated into the article, the Strengthening Reporting of Observational Studies in Epidemiology (STROBE) tool was utilized. The main outcomes assessed in this study included gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), gestational hypertension (GH), and preeclampsia (PE).

RESULTS

Twenty-five relevant studies involving 30079 participants were finally selected from four databases. The combined estimates indicate that prenatal exposure to perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), and perfluoroenanthic acid (PFHpA) is associated with gestational diabetes mellitus (GDM) (PFOA: OR = 1.45, 95%CI: 1.07-1.94, P = 0.015; PFHxS: OR = 1.16, 95%CI: 1.00-1.36, P = 0.055; PFBS: OR = 1.44, 95%CI: 1.16-1.79, P = 0.001; PFHpA: OR = 1.41, 95%CI: 1.10-1.82, P = 0.008). The exposure to PFBS is positively associated with HDP (OR = 1.27, 95%CI: 1.14-1.41, P < 0.001), while both PFOA and PFHpA demonstrate statistically significant positive correlations with GH (PFOA: OR = 1.09, 95%CI: 1.00-1.19, P = 0.049; PFHpA: OR = 1.43, 95%CI: 1.15-1.78, P = 0.001). Negative correlations were observed for prenatal perfluorododecanoic acid (PFDoA) exposure and GH (OR = 0.71, 95%CI: 0.57-0.87, P = 0.001). However, no compelling evidence was identified to link PFASs exposure with the risk of PE.

CONCLUSION

According to the meta-analysis findings, exposure to PFASs may be linked to GDM, HDP, and GH, but it does not significantly raise the risk of PE alone. Further research with larger sample size is required to verify this potential association and explore the biological mechanisms.

Association of per- and polyfluoroalkyl substances with hepatic steatosis and metabolic dysfunction-associated fatty liver disease among patients with acute coronary syndrome

Etiology of hepatic steatosis and metabolic dysfunction-associated fatty liver disease (MAFLD) among acute coronary syndrome (ACS) remains unclear. Existing studies suggested the potential role of per- and polyfluoroalkyl substances (PFAS) in comorbidity of hepatic steatosis among ACS patients. Therefore, we conducted a cross-sectional study based on the ACS inpatients to assess the associations of plasma PFAS congeners and mixtures with hepatic steatosis and MAFLD. This study included 546 newly diagnosed ACS patients. Twelve PFAS were quantified using ultra-high-performance liquid chromatography-tandem mass spectrometry. Hepatic steatosis was defined by hepatic steatosis index (HSI). MAFLD was defined as the combination of hepatic steatosis based on the risk factor calculation with metabolic abnormalities. Generalized linear model was used to examine the associations of PFAS congeners with HSI and MAFLD. Adaptive elastic net (AENET) was further used for PFAS congeners selection. Mixture effects were also assessed with Bayesian kernel machine regression model (BKMR). Congeners analysis observed significant greater percent change of HSI for each doubling in PFOS (1.82%, 95% CI: 0.87%, 2.77%), PFHxS (1.17%, 95% CI: 0.46%, 1.89%) and total PFAS (1.84%, 95% CI: 0.56%, 3.14%). Moreover, each doubling in PFOS (OR=1.42, 95% CI: 1.13, 1.81), PFHxS (OR=1.31, 95% CI: 1.09, 1.59) and total PFAS (OR=1.43, 95% CI: 1.06, 1.94) was associated with increased risk of MAFLD. In AENET regression, only PFOS presented significant positive associations with HSI. Mixture analysis indicated significant positive associations between PFAS mixtures and HSI. This is the first study to demonstrate associations of PFAS congeners and mixtures with hepatic steatosis and MAFLD among ACS patients, which provides hypothesis into the mechanisms behind comorbidity of hepatic steatosis among ACS patients, as well as tertiary prevention of ACS.

Combined toxic effects of polypropylene and perfluorooctanoic acid on duckweed and periphytic microorganisms

Microplastics and perfluorooctanoic acid coexist in the aquatic environment. Duckweed was exposed to a range of concentrations (0.1-1000 μg L-1) of solutions containing polypropylene (PP) and perfluorooctanoic acid (PFOA) for 14 days to measure their toxicity. The result showed the single and combined PP and PFOA treatments did not significantly influence the growth of duckweed. The greatest PP and PFOA concentrations of combined pollution affect plant chlorophyll. Moreover, the combined treatment of duckweed consistently resulted in increased malondialdehyde (MDA) levels, indicating oxidative damage. As an antioxidant stress response, the combination-treated plants were encouraged to produce superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Meanwhile, 3519 Operational Taxonomic Units (OTUs) were identified in the duckweed rhizosphere. Proteobacteria was the most predominant microbial community. Shannon, Simpson, and Chao1 discovered that microbial communities changed in response to single and combination PP and PFOA treatments, with decreased diversity and increased abundance. In addition, SEM analysis also revealed that the combined treatment significantly phyllosphere microorganisms. The findings of this investigation add to our knowledge of how PP and PFOA affect duckweed and the rhizospheric microorganisms, expanding the theoretical basis for employing duckweed in complex contamination.

Antibiotic induced restructuring of the gut microbiota does not affect oral uptake and accumulation of perfluorooctane sulfonic acid (PFOS) in rats

Perfluorooctane sulfonic acid (PFOS) is a manmade legacy compound belonging to the group of persistent per- and polyfluorinated substances (PFAS). While many adverse health effects of PFOS have been identified, knowledge about its effect on the intestinal microbiota is scarce. The microbial community inhabiting the gut of mammals plays an important role in health, for instance by affecting the uptake, excretion, and bioavailability of some xenobiotic toxicants. Here, we investigated (i) the effect of vancomycin-mediated microbiota modulation on the uptake of PFOS in adult Sprague-Dawley rats, and (ii) the effects of PFOS exposure on the rat microbiota composition. Four groups of twelve rats were exposed daily for 7 days with either 3 mg/kg PFOS plus 8 mg/kg vancomycin, only PFOS, only vancomycin, or a corn oil control. Vancomycin-induced modulation of the gut microbiota composition did not affect uptake of branched and linear PFOS over a period of 7 days, measured in serum samples. 16S rRNA amplicon sequencing of faecal and intestinal samples revealed that vancomycin treatment lowered microbial alpha-diversity, while PFOS increased the microbial diversity in vancomycin-treated as well as in non-antibiotic treated animals, possibly because an observed decrease in the Enterobacteriaceae abundance allows other microbial species to propagate. Colonic short-chain fatty acids were significantly lower in vancomycin-treated animals but remained unaffected by PFOS. Our results suggest that PFOS exposure may disturb the intestinal microbiota, but that antibiotic-induced modulation of the intestinal ecosystem does not affect systemic uptake of PFOS in rats.

Environmental explanation of prostate cancer progression based on the comprehensive analysis of perfluorinated compounds

Perfluorinated compounds (PFCs) are man-made chemicals used in the manufacture of many products with water and dirt repellent properties. Many diseases have been proved to be related to the exposure of PFCs, including breast fibroadenoma, hepatocellular carcinoma, breast cancer and leydig cell adenoma. However, whether the PFCs promote the progression of prostate cancer remains unclear. In this work, through comprehensive bioinformatics analysis, we discovered the correlation between the prostate cancer and five PFCs using Comparative Toxicogenomics Database (CTD), Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. In addition, further analysis showed that several PFCs-related genes demonstrated strong prognostic value for prostate cancer patients. The survival analysis and receiver operating characteristic (ROC) curves revealed that PFCs-related genes based prognostic model held great predictive value for the prognosis of prostate cancer, which could potentially serve as an independent risk factor in the future. In vitro experiments verified the promotive role of perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) in the growth of prostate cancer cells. This study provided novel insights into understanding the role of PFCs in prostate cancer and brought attention to the environmental association with cancer risks and progression.

PFOA exposure induces aberrant glucose and lipid metabolism in the rat liver through the AMPK/mTOR pathway

Perfluorooctanoic acid (PFOA) is the most prominent member of a widely utilized family of compounds named Perfluoroalkyl substances (PFASs). Initially produced for use in both industrial and consumer applications, it has since been recognized that PFASs are extremely persistent in the environment where they have been characterized as persistent organic pollutants (POPs). While previous studies have demonstrated that PFOA may induce disorders of lipid and carbohydrate metabolism, the precise mechanisms by which PFOA produces this phenotype and the involvement of downstream AMPK/mTOR pathways remains unclear. In this study, male rats were exposed to 1.25, 5 and 20mg PFOA/kg body weight/day for 28 days by oral gavage. After 28 days, blood was collected and tested for serum biochemical indicators and livers were removed and weighed. To investigate aberrant metabolism in rats exposed to PFOA, livers were analyzed by performing LC-MS/MS untargeted metabolomics, quantitative real-time PCR, western blotting, immunohistochemical staining was also performed on exposed tissues. Our results showed that exposure to PFOA induced liver damage, increased the expression of glucose and lipid related biochemical indexes in liver and serum, and altered the expression levels of AMPK/mTOR pathway related genes and proteins. In summary, this study clarifies the mechanisms responsible for PFOA toxicity in the liver of exposed animals.

Variations of the Level, Profile, and Distribution of PFAS around POSF Manufacturing Facilities in China: An Overlooked Source of PFCA

The occurrence of per- and polyfluoroalkyl substances (PFAS) was investigated inside two manufacturing facilities in China. Levels, profiles, and spatial distribution of the detected PFAS were found to be distinctly site-specific and influenced by the area's historic function, production structure of the plant, downpour-induced accidental pollution, and variations in the adsorption and transport of compounds. Very high concentrations of PFAS [mainly C4 and C8 perfluoroalkyl sulfonic acids (PFSAs)] were found in topsoil and groundwater from both plants, with the highest values of 4.89 × 10⁶ μg/kg dw and 1.10 × 10⁴ μg/L, respectively. Elevated concentrations of perfluoroalkyl carboxylic acids (PFCAs) in this study were attributed to their unintentional formation during the electrochemical fluorination process, which might be an overlooked source of PFCA. PFAS generally showed decreasing trends from shallow layers to the bottom of the soil core and demonstrated some downward migrations at different soil depths with time, and C4-C8 PFAS presented a deeper seepage than their long-chain homologues. Total organic carbon appeared to be more important for PFAS sorption to the topsoil than to the soil core. Workers were at potential risk of exposure to perfluorooctanesulfonic acid via soil at production and storage related sites. This study provides a critical reference for the systematic control of PFAS pollution around manufacturing facilities and a proof for an overlooked source of PFCA.

Association of increased risk of cardiovascular diseases with higher levels of perfluoroalkylated substances in the serum of adults

Evidence showing the association of perfluoroalkylated substance (PFAS) exposure with CVD risk is scarce. The objective of this study was to explore the relationships of CVD risk with mixed or individual serum PFAS levels among general adults. We analyzed combined data of 7904 adults who participated in the National Health and Nutrition Examination Survey 2003-2012 with a Bayesian kernel machine regression (BKMR) to examine the relationships of individual or mixed PFAS exposure with total CVD risk. A logistic regression model and restricted cubic spline (RCS) regression with multivariate adjustment were conducted to assess the relationships between individual serum PFAS levels and the risk of total CVD or its subtypes. A mediation model was applied to investigate how C-reactive protein (CRP) levels mediate the strength of the association. The BKMR results indicated a positive relationship between mixed PFAS exposure and total CVD risk; among the PFASs, perfluorooctane sulfonic acid (PFOS) had the highest posterior inclusion probability. As determined by logistic regression, a log-unit change in PFOS levels was positively related to a higher risk of heart attack and stroke in males (both P < 0.05). A nonlinear relationship was found between PFOS levels and stroke risk (P for nonlinearity = 0.04), as illustrated in the RCS plot. The mediation analysis showed that CRP levels mediated 8% and 1.2% of the relationship between serum PFOS and PFNA levels, respectively, and the prevalence of stroke. A significant relationship between higher serum PFAS concentrations and an increased risk of CVD was observed, mainly in males.

Reproductive and developmental toxicity of perfluorooctane sulfonate (PFOS) in the white-footed mouse (Peromyscus leucopus)

Concerns about per- and polyfluoroalkyl substances (PFAS) stem from their ubiquitous presence in the environment, bioaccumulation, resistance to degradation, and toxicity. Previously, toxicity data relevant to ecological risk assessment has largely been aquatic, terrestrial invertebrates, or avian in origin. In this study, repeated oral exposures of perfluorooctane sulfonate (PFOS) were administered to white-footed mice (Peromyscus leucopus) to evaluate effects on reproduction and development. Prenatal exposure to high doses of PFOS caused neonatal mortality, though growth and development were unaffected by low doses. Additionally, parental (P) generation animals exhibited increased liver:body weight, increased hepatocyte cytoplasmic vacuolization, and decreased serum thyroxine (T4) levels. Total litter loss was selected as the protective critical effect in this study resulting in a benchmark dose low (BMDL) of 0.12 mg/kg-d PFOS. Importantly, PFOS exposure has been linked to reduced adult recruitment in myriad species and at similar thresholds to this study. Similarities in critical/toxicologic effects across taxa may add confidence in risk assessments at sites with multiple taxa or environments.

Comparative Hepatotoxicity of a Novel Perfluoroalkyl Ether Sulfonic Acid, Nafion Byproduct 2 (H-PFMO2OSA), and Legacy Perfluorooctane Sulfonate (PFOS) in Adult Male Mice

Nafion byproduct 2 (H-PFMO2OSA) has been detected in the environment, but little is known about its toxicities. To compare the hepatotoxicity of H-PFMO2OSA with legacy perfluorooctane sulfonate (PFOS), male adult mice were exposed to 0.2, 1, or 5 mg/kg/d of each chemical for 28 days. Results showed that, although H-PFMO2OSA liver and serum concentrations were lower than those of PFOS, the relative liver weight in the H-PFMO2OSA groups was significantly higher than that in the corresponding PFOS groups. In addition, the increase in alanine transaminase and aspartate aminotransferase activity was greater in the H-PFMO2OSA groups than in the PFOS groups. Reduced glutathione (GSH) content and glutathione reductase activity in the liver increased in the 1 and 5 mg/kg/d H-PFMO2OSA groups and in the 5 mg/kg/d PFOS group. Liver quantitative proteome analysis demonstrated that, similar to PFOS, H-PFMO2OSA caused lipid metabolism disorder, and most lipid metabolism-related differentially expressed proteins (DEPs) were controlled by peroxisome proliferator-activated receptor alpha (PPARα). Additionally, KEGG enrichment analysis highlighted changes in the GSH metabolism pathway after PFOS and H-PFMO2OSA exposure. Then, there were eight DEPs involved in the GSH metabolism pathway that mostly were upregulated after exposure to H-PFMO2OSA but not after exposure to PFOS. In conclusion, H-PFMO2OSA induced higher levels of liver damage and more serious GSH metabolism dysregulation compared to PFOS.

Internal Relative Potency Factors for the Risk Assessment of Mixtures of Per- and Polyfluoroalkyl Substances (PFAS) in Human Biomonitoring

BACKGROUND

In human biomonitoring, blood is often used as a matrix to measure exposure to per- and polyfluoroalkyl substances (PFAS). Because the toxicokinetics of a substance (determining the steady-state blood concentration) may affect the toxic potency, the difference in toxicokinetics among PFAS has to be accounted for when blood concentrations are used in mixture risk assessment.

OBJECTIVES

This research focuses on deriving relative potency factors (RPFs) at the blood serum level. These RPFs can be applied to PFAS concentrations in human blood, thereby facilitating mixture risk assessment with primary input from human biomonitoring studies.

METHODS

Toxicokinetic models are generated for 10 PFAS to estimate the internal exposure in the male rat at the blood serum level over time. By applying dose-response modeling, these internal exposures are used to derive quantitative internal RPFs based on liver effects.

RESULTS

Internal RPFs were successfully obtained for nine PFAS. Perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluorononanoic acid (PFNA), perfluorododecanoic acid (PFDoDA), perfluorooctane sulfonic acid (PFOS), and hexafluoropropylene oxide-dimer acid (HFPO-DA, or GenX) were found to be more potent than perfluorooctanoic acid (PFOA) at the blood serum level in terms of relative liver weight increase, whereas perfluorobutane sulfonic acid (PFBS) and perfluorohexane sulfonic acid (PFHxS) were found to be less potent. The practical implementation of these internal RPFs is illustrated using the National Health and Nutrition Examination Survey (NHANES) biomonitoring data of 2017-2018.

DISCUSSION

It is recommended to assess the health risk resulting from exposure to PFAS as combined, aggregate exposure to the extent feasible. https://doi.org/10.1289/EHP10009.

Replacement per- and polyfluoroalkyl substances (PFAS) are potent modulators of lipogenic and drug metabolizing gene expression signatures in primary human hepatocytes

Per- and polyfluoroalkyl substances (PFAS) are a class of environmental toxicants, and some, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been associated with hepatic steatosis in rodents and monkeys. It was hypothesized that perfluorosulfonic acids (C4, 6, 8), perfluorocarboxylic acids (C4-14), perfluoro(2-methyl-3-oxahexanoic) acid (HFPO-DA), 1H, 1H, 2H, 2H-perfluorooctanesulfonic acid (6:2 FTS) along with 3 PFOS precursors could induce expression of lipid metabolism genes and lipid deposition in human hepatocytes. Five-donor pooled cryopreserved human hepatocytes were cultured and treated with 0.1% DMSO vehicle or various PFAS (0.25 to 25 μM) in media. After a 48-h treatment, mRNA transcripts related to lipid transport, metabolism, and synthesis were measured using a Quantigene Plex assay. After 72-h treatments, hepatocytes were stained with Nile Red dye to quantify intracellular lipids. Overall, PFAS were transcriptionally active at 25 μM. In this model, lipid accumulation was not observed with C8-C12 treatments. Shorter chain PFAS (C4-C5), 6:2 FTS, and PFOS precursor, metFOSA, induced significant liver lipid accumulation, and gene activation at lower concentrations than legacy PFAS. In summary short chain PFAS and other alternative PFAS were more potent gene inducers, and potential health effects of replacement PFAS should be critically evaluated in humans.

Exposure to per- and Polyfluoroalkyl Substances and Markers of Liver Injury: A Systematic Review and Meta-Analysis

BACKGROUND

Experimental evidence indicates that exposure to certain pollutants is associated with liver damage. Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals widely used in industry and consumer products and bioaccumulate in food webs and human tissues, such as the liver.

OBJECTIVE

The objective of this study was to conduct a systematic review of the literature and meta-analysis evaluating PFAS exposure and evidence of liver injury from rodent and epidemiological studies.

METHODS

PubMed and Embase were searched for all studies from earliest available indexing year through 1 December 2021 using keywords corresponding to PFAS exposure and liver injury. For data synthesis, results were limited to studies in humans and rodents assessing the following indicators of liver injury: serum alanine aminotransferase (ALT), nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, or steatosis. For human studies, at least three observational studies per PFAS were used to conduct a weighted z-score meta-analysis to determine the direction and significance of associations. For rodent studies, data were synthesized to qualitatively summarize the direction and significance of effect.

RESULTS

Our search yielded 85 rodent studies and 24 epidemiological studies, primarily of people from the United States. Studies focused primarily on legacy PFAS: perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid. Meta-analyses of human studies revealed that higher ALT levels were associated with exposure to PFOA (z-score= 6.20, p<0.001), PFOS (z-score= 3.55, p<0.001), and PFNA (z-score= 2.27, p=0.023). PFOA exposure was also associated with higher aspartate aminotransferase and gamma-glutamyl transferase levels in humans. In rodents, PFAS exposures consistently resulted in higher ALT levels and steatosis.

CONCLUSION

There is consistent evidence for PFAS hepatotoxicity from rodent studies, supported by associations of PFAS and markers of liver function in observational human studies. This review identifies a need for additional research evaluating next-generation PFAS, mixtures, and early life exposures. https://doi.org/10.1289/EHP10092.

Perfluoroalkyl substances in circum-ArcticRangifer: caribou and reindeer

Livers of caribou and reindeer (Rangifer tarandus) from Canada (n = 146), Greenland (n = 30), Svalbard (n = 7), and Sweden (n = 60) were analyzed for concentrations of eight perfluoroalkyl carboxylic acids and four perfluoroalkane sulfonic acids. In Canadian caribou, PFNA (range < 0.01-7.4 ng/g wet weight, ww) and PFUnDA (<0.01-5.6 ng/g ww) dominated, whereas PFOS predominated in samples from South Greenland, Svalbard, and Sweden, although the highest concentrations were found in caribou from Southwest Greenland (up to 28 ng/g ww). We found the highest median concentrations of all PFAS except PFHxS in Akia-Maniitsoq caribou (Southwest Greenland, PFOS 7.2-19 ng/g ww, median 15 ng/g ww). The highest concentrations of ΣPFAS were also found in Akia-Maniitoq caribou (101 ng/g ww) followed by the nearby Kangerlussuaq caribou (45 ng/g ww), where the largest airport in Greenland is situated, along with a former military base. Decreasing trends in concentrations were seen for PFOS in the one Canadian and three Swedish populations. Furthermore, PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA showed decreasing trends in Canada's Porcupine caribou between 2005 and 2016. In Sweden, PFHxS increased in the reindeer from Norrbotten between 2003 and 2011. The reindeer from Västerbotten had higher concentrations of PFNA and lower concentrations of PFHxS in 2010 compared to 2002. Finally, we observed higher concentrations in 2010 compared to 2002 (albeit statistically insignificant) for PFHxS in Jämtland, while PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA showed no difference at all.

Perfluorinated alkyl substances: Sewage treatment and implications for receiving waters

This study comprises a detailed analysis of data for perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) for over 600 wastewater treatment works effluents (WwTW) as well as samples upstream and downstream of each discharge of effluent into its receiving water. This has allowed an investigation of not only the effectiveness of removal of the perfluoroalkyl substances (PFAS) compounds during wastewater treatment but also implications for compliance with the environmental quality standard (EQS) set for PFOS under the Water Framework Directive. It is shown that effluents contain concentrations of PFOS that exceed the annual average EQS by a factor between 1.1-fold and 40-fold. The corresponding factors for PFOA are between 2-fold and 22-fold. The presence of high concentrations upstream, means that between a quarter and a third of individual effluents are found to reduce the concentration of fluorocarbons in the river downstream of the discharge point. The elevated concentrations upstream of the studied wastewater treatment works suggest inputs of these perfluoro compounds into the aquatic environment are ubiquitous and therefore difficult to address from simply setting permit conditions for individual WwTW. The freshwater EQS set for PFOS is based on several worst-case accumulation coefficients and large safety factors, which, when combined, result in a sub ng/L EQS. Consequently, the use of the biota derived quality standard may be a more realistic measure of environmental risk. It may be prudent, to assess the effectiveness of controls implemented in the last few years before considering widespread end-of-pipe treatment.

The role of maternal high fat diet on mouse pup metabolic endpoints following perinatal PFAS and PFAS mixture exposure

Per- and polyfluoroalkyl substances (PFAS) are a family of chemicals that are ubiquitous in the environment. Some of these chemicals, such as perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA), are found in human sera and have been shown to cause liver steatosis and reduce postnatal survival and growth in rodents. The purpose of this work is to evaluate the impact of diet and PFAS exposure to mouse dam (mus musculus) on the risk to pup liver and metabolism endpoints later in life, as well as evaluate PFAS partitioning to pups. Timed-pregnant dams were fed a standard chow diet or 60 % kcal high fat diet (HFD). Dams were administered either vehicle, 1 mg/kg PFOA, 1 mg/kg PFOS, 1 mg/kg PFHxS, or a PFAS mixture (1 mg/kg of each PFOA, PFOS, and PFHxS) daily via oral gavage from gestation day 1 until postnatal day (PND) 20. At PND 21, livers of dams and 2 pups of each sex were evaluated for lipid changes while remaining pups were weaned to the same diet as the dam for an additional 10 weeks. Dam and pup serum at PND 21 and PND 90 were also evaluated for PFAS concentration, alanine aminotransferase (ALT), leptin and adiponectin, and glycosylated hemoglobin A1c. Perinatal exposure to a HFD, as expected, increased pup body weight, maternal liver weight, pup liver triglycerides, pup serum ALT, and pup serum leptin. PFOA and the PFAS mixture increased liver weights, and. treatment with all three compounds increased liver triglycerides. The maternal HFD increased dam and pup serum PFAS levels, however, was protective against PFOA-induced increase in serum ALT and observed increases in liver triglycerides. The PFAS mixture had very distinct effects when compared to single compound treatment, suggesting some cumulative effects, particularly when evaluating PFAS transfer from dam to pup. This data highlights the importance of diet and mixtures when evaluating liver effect of PFAS and PFAS partitioning.

Perfluorooctanesulfonic Acid (PFOS) Thwarts the Beneficial Effects of Calorie Restriction and Metformin

A combination of calorie restriction (CR), dietary modification, and exercise is the recommended therapy to reverse obesity and nonalcoholic fatty liver disease. In the liver, CR shifts hepatic metabolism from lipid storage to lipid utilization pathways, such as AMP-activated protein kinase (AMPK). Perfluorooctanesulfonic acid (PFOS), a fluorosurfactant previously used in stain repellents and anti-stick materials, can increase hepatic lipids in mice following relatively low-dose exposures. To test the hypothesis that PFOS administration interferes with CR, adult male C57BL/6N mice were fed ad libitum or a 25% reduced calorie diet concomitant with either vehicle (water) or 100 μg PFOS/kg/day via oral gavage for 6 weeks. CR alone improved hepatic lipids and glucose tolerance. PFOS did not significantly alter CR-induced weight loss, white adipose tissue mass, or liver weight over 6 weeks. However, PFOS increased hepatic triglyceride accumulation, in both mice fed ad libitum and subjected to CR. This was associated with decreased phosphorylated AMPK expression in liver. Glucagon (100 nM) treatment induced glucose production in hepatocytes, which was further upregulated with PFOS (2.5 μM) co-treatment. Next, to explore whether the observed changes were related to AMPK signaling, HepG2 cells were treated with metformin or AICAR alone or in combination with PFOS (25 μM). PFOS interfered with glucose-lowering effects of metformin, and AICAR treatment partially impaired PFOS-induced increase in glucose production. In 3T3-L1 adipocytes, metformin was less effective with PFOS co-treatment. Overall, PFOS administration disrupted hepatic lipid and glucose homeostasis and interfered with beneficial glucose-lowering effects of CR and metformin.

Understanding the Impact of Perfluorinated Compounds on Cardiovascular Diseases and Their Risk Factors: A Meta-Analysis Study

Perfluorinated compounds (PFCs) are non-biodegradable synthetic chemical compounds that are widely used in manufacturing many household products. Many studies have reported the association between PFCs exposure with the risk of developing cardiovascular diseases (CVDs). However, those reports are still debatable, due to their findings. Thus, this review paper aimed to analyse the association of PFCs compound with CVDs and their risk factors in humans by systematic review and meta-analysis. Google Scholar, PubMed and ScienceDirect were searched for PFCs studies on CVDs and their risk from 2009 until present. The association of PFCs exposure with the prevalence of CVDs and their risk factors were assessed by calculating the quality criteria, odds ratios (ORs), and 95% confidence intervals (CIs). CVDs risk factors were divided into serum lipid profile (main risk factor) and other known risk factors. The meta-analysis was then used to derive a combined OR test for heterogeneity in findings between studies. Twenty-nine articles were included. Our meta-analysis indicated that PFCs exposure could be associated with CVDs (Test for overall effect: z = 2.2, p = 0.02; Test for heterogeneity: I² = 91.6%, CI = 0.92–1.58, p < 0.0001) and their risk factors (Test for overall effect: z = 4.03, p < 0.0001; Test for heterogeneity: I² = 85.8%, CI = 1.00–1.14, p < 0.0001). In serum lipids, total cholesterol levels are frequently reported associated with the exposure of PFCs. Among PFCs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) exposure increased the risk of CVDs than other types of PFCs. Although the risk of PFOA and PFOS were positively associated with CVDs and their risk factors, more observational studies shall be carried out to identify the long-term effects of these contaminants in premature CVDs development in patients.

LC-HRMS screening of per- and polyfluorinated alkyl substances (PFAS) in impregnated paper samples and contaminated soils

High per- and polyfluorinated alkyl substance (PFAS) concentrations have been detected in agricultural soils in Southwest Germany. Discharges of PFAS-contaminated paper sludge and compost are suspected to be the cause of the contamination. Perfluorinated carboxylic acids (PFCAs) have been detected also in groundwater, drinking water, and plants in this area. Recently, previously unknown compounds have been identified by high-resolution mass spectrometry (HRMS). Major contaminants were polyfluorinated dialkylated phosphate esters (diPAPs) and N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diester (diSAmPAP). In this study, HRMS screening for PFAS was applied to 14 soil samples from the contaminated area and 14 impregnated paper samples which were from a similar period than the contamination. The paper samples were characterized by diPAPs (from 4:2/6:2 to 12:2/12:2), fluorotelomer mercapto alkyl phosphates (FTMAPs; 6:2/6:2 to 10:2/10:2), and diSAmPAP. In soil samples, diPAPs and their transformation products (TPs) were the major contaminants, but also FTMAPs, diSAmPAP, and their TPs occurred. The distribution patterns of the carbon chain lengths of the precursor PFAS in soil samples were shown to resemble those in paper samples. This supports the hypothesis that paper sludge is a major source of contamination. The presence of major degradation products like PFCAs, FTSAs, or PFOS and their distribution of carbon chain lengths indicate the activity of biotic or abiotic degradation processes and selective leaching processes from the upper soil horizons.

Systemic PFOS and PFOA exposure and disturbed lipid homeostasis in humans: what do we know and what not?

Associations between per- and polyfluoroalkyl substances (PFASs) and increased blood lipids have been repeatedly observed in humans, but a causal relation has been debated. Rodent studies show reverse effects, i.e. decreased blood cholesterol and triglycerides, occurring however at PFAS serum levels at least 100-fold higher than those in humans. This paper aims to present the main issues regarding the modulation of lipid homeostasis by the two most common PFASs, PFOS and PFOA, with emphasis on the underlying mechanisms relevant for humans. Overall, the apparent contrast between human and animal data may be an artifact of dose, with different molecular pathways coming into play upon exposure to PFASs at very low versus high levels. Altogether, the interpretation of existing rodent data on PFOS/PFOA-induced lipid perturbations with respect to the human situation is complex. From a mechanistic perspective, research on human liver cells shows that PFOS/PFOA activate the PPARα pathway, whereas studies on the involvement of other nuclear receptors, like PXR, are less conclusive. Other data indicate that suppression of the nuclear receptor HNF4α signaling pathway, as well as perturbations of bile acid metabolism and transport might be important cellular events that require further investigation. Future studies with human-relevant test systems would help to obtain more insight into the mechanistic pathways pertinent for humans. These studies shall be designed with a careful consideration of appropriate dosing and toxicokinetics, so as to enable biologically plausible quantitative extrapolations. Such research will increase the understanding of possible perturbed lipid homeostasis related to PFOS/ PFOA exposure and the potential implications for human health.

Suggestions for Improving the Characterization of Risk from Exposures to Per and Polyfluorinated Alkyl Substances

Many state and federal environmental and health agencies have developed risk-based criteria for assessing the risk of adverse health effects of per- and polyfluorinated alkyl substances (PFAS) exposure to humans and the environment. However, the criteria that have been developed vary; drinking water criteria developed for perfluorooctanoic acid, for example, can vary by up to 750 fold. This is due to differences and variability in the data and information used, study/endpoint selection, assumptions and magnitude of uncertainty factors used in the absence and extrapolation of critical effect data, differences in underlying approaches to addressing exposure within criteria development, and/or policy decisions on levels of acceptable risk. We have critically evaluated the methods used to develop these criteria while focusing on derivation and application of drinking water criteria and discuss a range of improvements to risk-characterization practice recently presented at a Focused Topic Meeting on PFAS conducted by the Society of Environmental Toxicology and Chemistry in Durham, North Carolina, USA, 12 to 15 August 2019. We propose methods that consider maximizing the use of disparate data streams, seeking patterns, and proposing biologically based approaches to evidence integration toward informed criteria development. Environ Toxicol Chem 2021;40:883-898. © 2020 SETAC.

Human Biomonitoring (HBM)-I values for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) - Description, derivation and discussion

In 2016, the German Human Biomonitoring Commission (HBM-C) published a statement on its decision to develop HBM-I values for Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS) (Bundesgesundheitsbl 2016, 59:1364 DOI 10.1007/s00103-016-2437-1). The HBM-I value corresponds to the concentration of a substance in a human biological material below which no adverse health effects are expected, according to current knowledge and assessment by the HBM-C, and, consequently, there is no need for action. Evidence for associations between PFOA- and PFOS-body burden and health outcomes was found for fertility and pregnancy, weights of newborns at birth, lipid metabolism, immunity, sex hormones and age at puberty/menarche, thyroid hormones, onset of menopause as well as uric acid metabolism. Significant contrasts were reported for human blood plasma concentrations between 1 and 10 ng PFOA/mL, and 1-15 ng PFOS/mL, respectively. Within the reported ranges, the HBM-C has decided to set the HBM-I-values at 2 ng PFOA/mL and 5 ng PFOS/mL blood plasma. The underlying pathomechanisms do not appear to be sufficiently clarified to provide an unambiguous explanation of the effects observed. Consistency of toxicological and epidemiological data has been considered. The available data do not indicate an unequivocal proof of a genotoxicity of PFOA and PFOS.

What are the effects of PFAS exposure at environmentally relevant concentrations?

The group of synthetic chemicals known as poly and per-fluoroalkyl substances (PFAS) are currently of high concern to environmental regulators and the public due to their widespread occurrence, resistance to degradation and reported toxicity. However, little data exists on the effects of exposure to PFAS at environmentally relevant concentrations and this hampers the effective management of these compounds. This paper reviews current research on the occurrence and ecotoxicology of PFAS at environmentally relevant doses to assess their potential biological impacts. Hazard Quotient (HQ) analysis was undertaken as part of this assessment. Most PFAS detected in the environment were found to have a HQ risk value of <1 meaning their reported concentrations are below their predicted no effect concentration. This indicates many reported toxic effects of PFAS are, theoretically, unlikely to occur outside the laboratory. However, lack of information on new PFAS as well as their precursors and degradation products, coupled with lack of knowledge of their mixture toxicity means our understanding of the risks of PFAS is incomplete, especially in regard to sub-lethal and/or chronic effects. It is proposed that the development of molecular markers for PFAS exposure are needed to aid in the development of environmental PFAS regulations that are effective in fully protecting the environment.

PFAS Environmental Pollution and Antioxidant Responses: An Overview of the Impact on Human Field

Due to their unique properties, perfluorinated substances (PFAS) are widely used in multiple industrial and commercial applications, but they are toxic for animals, humans included. This review presents some available data on the PFAS environmental distribution in the world, and in particular in Europe and in the Veneto region of Italy, where it has become a serious problem for human health. The consumption of contaminated food and drinking water is considered one of the major source of exposure for humans. Worldwide epidemiological studies report the negative effects that PFAS have on human health, due to environmental pollution, including infertility, steroid hormone perturbation, thyroid, liver and kidney disorders, and metabolic disfunctions. In vitro and in vivo researches correlated PFAS exposure to oxidative stress effects (in mammals as well as in other vertebrates of human interest), produced by a PFAS-induced increase of reactive oxygen species formation. The cellular antioxidant defense system is activated by PFAS, but it is only partially able to avoid the oxidative damage to biomolecules.

Early life exposure to per- and polyfluoroalkyl substances (PFAS) and latent health outcomes: A review including the placenta as a target tissue and possible driver of peri- and postnatal effects

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous drinking water contaminants of concern due to mounting evidence implicating adverse health outcomes associated with exposure, including reduced kidney function, metabolic syndrome, thyroid disruption, and adverse pregnancy outcomes. PFAS have been produced in the U.S. since the 1940s and now encompass a growing chemical family comprised of diverse chemical moieties, yet the toxicological effects have been studied for relatively few compounds. Critically, exposures to some PFAS in utero are associated with adverse outcomes for both mother and offspring, such as hypertensive disorders of pregnancy (HDP), including preeclampsia, and low birth weight. Given the relationship between HDP, placental dysfunction, adverse health outcomes, and increased risk for chronic diseases in adulthood, the role of both developmental and lifelong exposure to PFAS likely contributes to disease risk in complex ways. Here, evidence for the role of some PFAS in disrupted thyroid function, kidney disease, and metabolic syndrome is synthesized with an emphasis on the placenta as a critical yet understudied target of PFAS and programming agent of adult disease. Future research efforts must continue to fill the knowledge gap between placental susceptibility to environmental exposures like PFAS, subsequent perinatal health risks for both mother and child, and latent health effects in adult offspring.

Per- and polyfluoroalkyl substances (PFASs) in blood of captive Siberian tigers in China: Occurrence and associations with biochemical parameters

Per- and polyfluoroalkyl substances (PFASs) have been ubiquitously detected in the environment and marine animals. However, little is known about these substances and their associations with health parameters in wild terrestrial mammals. In this study, we determined PFAS levels and distribution in the blood of captive Siberian tigers in Harbin, China, and evaluated potential exposure pathways by daily intake. In addition, for the first time, we explored the associations between serum PFAS concentrations and clinical parameters. Results showed that perfluorooctanoate (PFOA) was the dominant PFAS compound in blood (accounting for 64%), followed by perfluorooctanesulfonate (PFOS). In addition, 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) concentrations were also detected in blood and dietary food. Furthermore, significant positive age relationships were observed for levels of perfluoroheptanoate (PFHpA), PFOA, PFOS, and 6:2 Cl-PFESA in the blood of female tigers. Results showed that PFOA and PFOS in dietary food accounted for over 70% of total daily intake of PFASs, indicating that meat consumption is a predominant exposure pathway in tigers. We also found positive associations between higher exposure to PFASs (including PFOA, PFOS, and 6:2 Cl-PFESA) and elevated serum levels of alanine transaminase (ALT), a marker of liver damage. Thus, comprehensive health assessments of PFAS burdens in wildlife are needed.

Perfluorooctanesulfonic acid (PFOS) administration shifts the hepatic proteome and augments dietary outcomes related to hepatic steatosis in mice

Hepatic steatosis increases risk of fatty liver and cardiovascular disease. Perfluorooctanesulfonic acid (PFOS) is a persistent, bio-accumulative pollutant that has been used in industrial and commercial applications. PFOS administration induces hepatic steatosis in rodents and increases lipogenic gene expression signatures in cultured hepatocytes. We hypothesized that PFOS treatment interferes with lipid loss when switching from a high fat diet (HFD) to a standard diet (SD), and augments HFD-induced hepatic steatosis. Male C57BL/6 N mice were fed standard chow diet or 60% kCal high-fat diet (HFD) for 4 weeks to increase body weight. Then, some HFD mice were switched to SD and mice were further divided to diet only or diet containing 0.0003% PFOS, for six treatment groups: SD, HFD to SD (H-SD), HFD, SD + PFOS, H-SD + PFOS, or HFD + PFOS. After 10 weeks on study, blood and livers were collected. HFD for 14 weeks increased body weight and hepatic steatosis, whereas H-SD mice returned to SD measures. PFOS administration reduced body weight in mice fed a SD, but not H-SD or HFD. PFOS administration increased liver weight in H-SD + PFOS and HFD + PFOS mice. PFOS increased hepatic steatosis in H-SD and HFD groups. Hepatic mRNA expression and SWATH-MS proteomic analysis revealed that PFOS induced lipid and xenobiotic transporters, as well as metabolism pathways. Overall, the findings herein suggest that PFOS treatment did interfere with lipid loss associated with switch to a SD and similarly augmented hepatic lipid accumulation in mice established on an HFD.

Enantioselectivity in transplacental transfer of perfluoro-1-methylheptanesulfonate (1m-PFOS): Human biomonitoring and in silico study

Perfluorooctane sulfonates (PFOS) are one of the most prominent perfluoroalkyl contaminants in humans and wildlife. Currently, information regarding enantiomer-specific exposure to PFOS in humans through transplacental transfer is lacking. This study examined 32 matched maternal serum, cord serum and placenta samples collected from mother-infant pairs in Wuhan, China. The enantiomer fraction (EF) value of perfluoro-1-methylhptanesulfonate (1m-PFOS) was lower in cord sera (0.362 ± 0.062, n = 23) compared to maternal sera (0.422 ± 0.048, n = 21) and placenta (0.410 ± 0.060, n = 16). Evaluations of the difference between EF_1m-PFOS suggested enantioselective transplacental transfer of 1m-PFOS. In silico evaluation of the binding affinity of 1m-PFOS to human serum albumin (HSA) showed that the two 1m-PFOS enantiomers enantioselectively interacted with the HSA. This result hints the enantioselective carrier protein affinity may be a key factor for stereoselective 1m-PFOS transplacental transfer. The percentage of branched PFOS (%br-PFOS) and EF_1m-PFOS was correlated in maternal sera, but not in cord sera and placentas. These data indicated that %br-PFOS and EF_1m-PFOS may be less reliable in identifying PreFOS exposure when it comes to complex biological processes, such as transplacental transport. This study could expand our understanding of stereoselective placental contaminant transfer in humans.

Cumulative dietary risk assessment overarching different regulatory silos using a margin of exposure approach: A case study with three chemical silos

Risk assessment of chemicals occurring in our diet is commonly performed for single chemicals without considering exposure to other chemicals. We performed a case study on risk assessment of combined dietary exposure to chemicals from different regulatory silos, i.e. pesticides (PPRs), persistent organic pollutants (POPs) and food additives (FAs). Chemicals were grouped into the cumulative assessment group (CAG) liver steatosis using a component-based approach. Based on literature, the CAG included 144 PPRs, 49 POPS and 7 FAs for which concentration data were available. For each silo, chronic combined dietary exposure was assessed for adults and children of nine European countries following the most commonly used exposure methodologies in Europe and by using a relative potency factor approach. For risk characterization, a Margin of Exposure (MOE) was calculated. To overarch the risk across silos, a normalised combined margin of exposure (nMOET) approach was proposed. This case study demonstrated that risk assessment of combined exposure to chemicals can be performed within regulatory silos. It also highlighted important differences in the conservatism of exposure scenarios, the derivation of point of departures and the subsequent acceptable MOEs between the silos. To overarch the risk despite these differences, a nMOET approach can be used.

Transcriptome analysis of acute exposure of the Manila clam, Ruditapes philippinarum to perfluorooctane sulfonate (PFOS)

Perfluorooctane sulfonate (PFOS) is an increasingly important environmental pollutant, which has been detected almost everywhere in the environment. Despite the widespread presence of PFOS, much less notice is taken of its toxicology effects on marine bivalves. Thus, the transcriptome response to PFOS treatment (nominal concentration of 20 mg/L) in hepatopancreas of a sentinel organism, Ruditapes philippinarum was examined. Compared with the control group, 32,149 unigenes were up-regulated and 26,958 unigenes down-regulated. Notably, significant gene expression changes were found in carbohydrate metabolism, energy metabolism, amino acid metabolism, lipid metabolism and protein biosynthesis, indicating the metabolic disruptions caused by PFOS in R. philippinarum. Additionally, numerous other differentially expressed genes were involved in immune system, antioxidant defense system and detoxification metabolism. In summary, transcriptome profiling of R. philippinarum after exposure to PFOS provided molecular support for our current understanding of the detrimental toxicity of PFOS on marine bivalves.

Chronic Reproductive Toxicity of Perfluorooctane Sulfonic Acid and a Simple Mixture of Perfluorooctane Sulfonic Acid and Perfluorohexane Sulfonic Acid to Northern Bobwhite Quail (Colinus virginianus)

Per- and poly-fluoroalkyl substances (PFAS) are a broad class of environmentally persistent chemicals that include thousands of potentially toxic synthetic organic molecules. Some PFAS have been shown to cause adverse health effects including decreased total cholesterol, birth weight, and reproductive success in laboratory animals; however, a lack of chronic toxicity data exists for PFAS in avian ecological receptors. The present study reports on the chronic toxicity of perfluorooctane sulfonic acid (PFOS) and a mixture of PFOS and perfluorohexane sulfonic acid (PFHxS) to northern bobwhite quail (Colinus virginianus) via oral exposure from drinking water. Female weight gain was adversely affected at an average daily intake (ADI) of 3.10 × 10^-3  ± 0.15 × 10^-3  mg PFOS:PFHxS (1.2:1) mixture × kg^-1 body weight × d^-1 . Successful liberation from the shell once pipped was adversely affected at an ADI of 2.45 × 10^-3  ± 0.01 × 10^-3  mg PFOS x kg^-1 body weight × d^-1 . These values are comparatively much lower than the current dietary avian toxicity reference value (TRV) derived from birds that were exposed via feed, suggesting the need for updated avian TRVs. Relationships between test chemical (PFOS) and test substance (PFOS:PFHxS) showed that PFOS and PFHxS have possible interacting effects in avian receptors and likely differing mechanisms of toxicity depending on chemical co-occurrence and dose. Both the single-chemical and mixture exposures produced similar and possibly additive toxicity values. Environ Toxicol Chem 2020;39:1101-1111. © 2020 SETAC.

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.

Quantitative bias analysis of the association between subclinical thyroid disease and two perfluoroalkyl substances in a single study

Exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) has been associated with the occurrence of thyroid disease in some epidemiologic studies. We hypothesized that in a specific epidemiologic study based on the National Health and Nutrition Examination Survey, the association of subclinical thyroid disease with serum concentration of PFOA and PFOS was due to reverse causality. Thyroid hormone affects glomerular filtration, which in turn affects excretion of PFOA and PFOS. We evaluated this by linking a model of thyroid disease status over the lifetime to physiologically based pharmacokinetic models of PFOA and PFOS. Using Monte Carlo methods, we simulated the target study population and analyzed the data using multivariable logistic regression. The target and simulated populations were similar with respect to age, estimated glomerular filtration rate, serum concentrations of PFOA and PFOS, and prevalence of subclinical thyroid disease. Our findings suggest that in the target study the associations with subclinical hypothyroidism were overstated and the results for subclinical hyperthyroidism were, in general, understated. For example, for subclinical hypothyroidism in men, the reported odds ratio per ln(PFOS) increase was 1.98 (95% CI 1.19-3.28), whereas in the simulated data the bias due to reverse causality gave an odds ratio of 1.19 (1.16-1.23). Our results provide evidence of bias due to reverse causality in a specific cross-sectional study of subclinical thyroid disease with exposure to PFOA and PFOS among adults.

Indoor exposure to per- and polyfluoroalkyl substances (PFAS) in the childcare environment

Per- and polyfluoroalkyl substances (PFAS) are widely used in stain-resistant carpets, rugs, and upholstery, as well as in waxes and cleaners, and are potential contaminants in the childcare environment. However, limited knowledge exists on the occurrence of PFAS in indoor environments, apart from residential homes. Here, we determined the occurrence and distribution of 37 neutral and ionic PFAS, including perfluoroalkyl carboxylates (PFCAs) perfluoroalkyl sulfonates (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer sulfonates (FTSs), perfluorooctane sulfonamides and perfluorooctane sulfonamidoethanols (FOSAs/FOSEs), and fluorotelomer acrylates and fluorotelomer methacrylates (FTACs/FTMACs) in the childcare environment and estimated children's exposure through dust ingestion and dermal absorption. We analyzed dust and nap mats, a commonly used item in many childcares, from eight facilities located in the United States. Twenty-eight PFAS were detected in dust with total PFAS concentrations (ΣPFAS) ranging from 8.1 to 3,700 ng/g and were dominated by the two neutral PFAS groups: ΣFTOH (n.d. - 3,100 ng/g) and ΣFOSA/FOSE (n.d. - 380 ng/g). The ionic PFAS were detected at lower concentrations and were dominated by 6:2 FTS and 8:2 FTS (median 12 and 5.8 ng/g, respectively). ΣPFAS concentrations in mats (1.6-600 ng/g) were generally an order of magnitude lower than in dust and were dominated by ΣFOSA/FOSE concentrations (n.d. - 220 ng/g). Daily intake of neutral PFAS in the childcare environment via dust ingestion was estimated at 0.20 ng/kg bw/day and accounted for 75% of the ΣPFAS intake. This higher exposure to neutral PFAS is concerning considering that many neutral PFAS are the precursors of toxic ionic PFAS, such as PFOA.

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.

Temporal Trends (1981-2013) of Per- and Polyfluoroalkyl Substances and Total Fluorine in Baltic cod (Gadus morhua)

Temporal trends from 1981 to 2013 of 28 per- and polyfluoroalkyl substances (PFASs) were investigated in liver tissue of cod (Gadus morhua) sampled near southeast Gotland, in the Baltic Sea. A total of 10 PFASs were detected, with ∑₂₈ PFAS geometric mean concentrations ranging from 6.03 to 23.9 ng/g ww. Perfluorooctane sulfonate (PFOS) was the predominant PFAS, which increased at a rate of 3.4% per year. Most long-chain perfluoroalkyl carboxylic acids increased at rates of 3.9 to 7.3% per year except for perfluorooctanoate (PFOA), which did not change significantly over time. The perfluoroalkyl acid precursors perfluorooctane sulfonamide (FOSA) and 6:2 fluorotelomer sulfonic acid were detected, of which the former (FOSA) declined at a rate of -4.4% per year, possibly reflecting its phase-out starting in 2000. An alternate time trend analysis from 2000 to 2013 produced slightly different results, with most compounds increasing at slower rates compared to the entire study period. An exception was perfluorohexane sulfonate (PFHxS), increasing at a faster rate of 3.7% measured from 2000 on, compared to the 3.0% per year measured starting from 1981. Analysis of the total fluorine content of the samples revealed large amounts of unidentified fluorine; however, its composition (organic or inorganic) remains unclear. Significant negative correlations were found between concentrations of individual PFASs (with the exception of PFOS) and liver somatic index. In addition, body length was negatively correlated with PFOA and perfluorononanoate, but positively correlated with perfluorododecanoate (PFDoDA) and FOSA. Additional studies on endocrine, immunological, and metabolic effects of PFAS in marine fish are essential to assess the environmental risk of these substances. Environ Toxicol Chem 2020;39:300-309. © 2019 SETAC.

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.

Children's exposure to perfluoroalkyl acids - a modelling approach

Adults are mainly exposed to per- and polyfluoroalkyl substances (PFASs) via ingestion of food, inhalation of air and ingestion of dust, whereas for children the exposure to PFASs is largely unknown. This study aimed to reconstruct the serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) in children after infancy up to 10.5 years of age and to test if dietary intake is the major exposure pathway for children to PFOA, PFOS and PFHxS after infancy. For this work, a dataset from a Finnish child cohort study was available, which comprised serum concentrations of the studied perfluoroalkyl acids (PFAAs) and PFAS concentration measurements in dust and air samples from the children's bedrooms. The calculated PFAA intakes were used in a pharmacokinetic model to reconstruct the PFAA serum concentrations from 1 to 10.5 years of age. The calculated PFOA and PFOS intakes were close to current regulatory intake thresholds and diet was the major exposure medium for the 10.5 year-olds. The one-compartment PK model reconstructed median PFOA and PFOS serum concentrations well compared to corresponding measured median serum concentrations, while the modelled PFHxS serum concentrations showed a constant underestimation. The results imply that children's exposure to PFOA and PFOS after breastfeeding and with increasing age resembles the exposure of adults. Further, the children in the Finnish cohort experienced a rather constant exposure to PFOA and PFOS between 1 and 10.5 years of age. The PFHxS exposure sources and respective pharmacokinetic parameter estimations need further investigation.

Bayesian evaluation of a physiologically based pharmacokinetic (PBPK) model for perfluorooctane sulfonate (PFOS) to characterize the interspecies uncertainty between mice, rats, monkeys, and humans: Development and performance verification

A challenge in the risk assessment of perfluorooctane sulfonate (PFOS) is the large interspecies differences in its toxicokinetics that results in substantial uncertainty in the dosimetry and toxicity extrapolation from animals to humans. To address this challenge, the objective of this study was to develop an open-source physiologically based pharmacokinetic (PBPK) model accounting for species-specific toxicokinetic parameters of PFOS. Considering available knowledge about the toxicokinetic properties of PFOS, a PBPK model for PFOS in mice, rats, monkeys, and humans after intravenous and oral administrations was created. Available species-specific toxicokinetic data were used for model calibration and optimization, and independent datasets were used for model evaluation. Bayesian statistical analysis using Markov chain Monte Carlo (MCMC) simulation was performed to optimize the model and to characterize the uncertainty and interspecies variability of chemical-specific parameters. The model predictions well correlated with the majority of datasets for all four species, and the model was validated with independent data in rats, monkeys, and humans. The model was applied to predict human equivalent doses (HEDs) based on reported points of departure in selected critical toxicity studies in rats and monkeys following U.S. EPA's guidelines. The lower bounds of the model-derived HEDs were overall lower than the HEDs estimated by U.S. EPA (e.g., 0.2 vs. 1.3 μg/kg/day based on the rat plasma data). This integrated and comparative analysis provides an important step towards improving interspecies extrapolation and quantitative risk assessment of PFOS, and this open-source model provides a foundation for developing models for other perfluoroalkyl substances.

Breastfeeding as a Predictor of Serum Concentrations of Per- and Polyfluorinated Alkyl Substances in Reproductive-Aged Women and Young Children: A Rapid Systematic Review

PURPOSE OF REVIEW

Per- and polyfluorinated alkyl substances (PFASs) are synthetic chemicals widely detected in human serum, and at low levels in breast milk. We conducted a rapid systematic review on breastfeeding practices and serum concentrations of PFASs-specifically PFOS and PFOA-among reproductive-aged women and young children using the Navigation Guide systematic review methodology.

RECENT FINDINGS

We included 14 studies examining associations between breastfeeding and PFASs in infants/toddlers or pregnant/postnatal women. Breastfeeding was significantly associated with lower PFASs exposure among women and higher PFASs exposure among children. We concluded there was "sufficient" evidence supporting an association between breastfeeding and serum PFASs concentrations among women, and "limited" evidence of an association among children due to issues with sample size, confounding, and exposure assessment. These findings reinforce that lactation is an important excretion route of PFASs for women, and that breast milk may be an important exposure pathway for young children.

Perfluoroalkyl substances (PFASs) in edible fish species from Charleston Harbor and tributaries, South Carolina, United States: Exposure and risk assessment

Concentrations of 11 PFASs were determined in muscle and whole fish for six species collected from Charleston, South Carolina (SC) for the assessment of potential health risks to humans and wildlife. Across all species and capture locations, total PFAS levels in whole fish were significantly higher than fillets by a factor of two- to three-fold. Mean ∑PFAS concentrations varied from 12.7 to 33.0 ng/g wet weight (ww) in whole fish and 6.2-12.7 ng/g ww in fillets. For individual whole fish, ∑PFASs ranged from 12.7 ng/g ww in striped mullet to 85.4 ng/g ww in spotted seatrout, and in fillets individual values ranged from 6.2 ng/g ww in striped mullet to 27.9 ng/g ww in spot. The most abundant compound in each species was perfluorooctane sulfonate (PFOS), comprising 25.5-69.6% of the ∑PFASs. Striped mullet had significantly lower relative amounts of PFOS compared to all other species and higher relative amounts of PFUnDA compared to Atlantic croaker, spotted seatrout, and spot. Unlike whole fish, PFAS levels in fillets varied significantly by location with higher ∑PFOS from the Ashley River than the Cooper River and Charleston Harbor, which reflects the levels of PFASs contamination in these systems. In whole fish, differences in relative concentrations of PFOS, PFNA, and PFDA occurred by capture location, suggestive of different sources. PFOS concentrations for southern flounder and spotted seatrout fillets were within the advisory range to limit fish consumption to 4 meals a month. PFOS levels exceeded screening values to protect mammals in 83% of whole fish examined and represent a potential risk to wildlife predators such as dolphins.