Paired Liver:Plasma PFAS Concentration Ratios from Adolescents in the Teen-LABS Study and Derivation of Empirical and Mass Balance Models to Predict and Explain Liver PFAS Accumulation

A machine learning multimodal profiling of Per- and Polyfluoroalkyls (PFAS) distribution across animal species organs via clustering and dimensionality reduction techniques

Per- and polyfluoroalkyl substances (PFAS) contamination in aquatic and terrestrial organisms poses significant environmental and health risks. This study quantified 15 PFAS compounds across various tissues (liver, kidney, gill, muscle, skin, lung, blood, breast, feather) from fish (Clarias gariepinus, Oreochromis niloticus, Lates niloticus, Tilapia zilli), livestock (camel, cow, sheep, ram, goat), and birds (pigeon, chicken, turkey). Among the fishes, C. gariepinus exhibited the highest PFAS accumulation, with PFOA (46.5 ng/g) and PFTrDA (50.1 ng/g) dominant in liver and kidney, while O. niloticus showed elevated PFTrDA (56.87 ng/g) and PFUnDA (29.43 ng/g). In livestock, camel liver contained high PFNA (9.22 ng/g), and cow liver had the highest PFOS (8.1 ng/g). Among the birds, pigeon liver showed the highest PFNA (7.83 ng/g). To analyze PFAS distribution patterns, dimensionality reduction and clustering techniques were employed. Principal Component Analysis (PCA) captured 68.28 % of total variance, revealing two distinct clusters whereby fish species are strongly related with higher PFAS concentration, while poultry showed unique PFAS profiles when compared to other types of meat. Clustering of PFOS, PFOA, and other PFAS compounds near the center explained their influence across the general meat types particularly the fish species, while t-Distributed Stochastic Neighbor Embedding (t-SNE) confirmed clear separations in high-dimensional space. Clustering analyses, including K-means, hierarchical clustering, DBSCAN, and Gaussian Mixture Models (GMM), identified well-defined patterns, with DBSCAN and GMM detecting overlapping categories and outliers. Feature importance analysis using a Random Forest model highlighted total PFAS as the most significant predictor, with PFHxA and PFDODA also contributing strongly, while organ type and species played a lesser role. These findings demonstrate the effectiveness of unsupervised learning techniques in characterizing PFAS bioaccumulation patterns across species and tissues, providing valuable information for ecological and toxicological risk assessments.

Accumulation of per- and polyfluoroalkyl substances (PFAS) in tissues of wild boar (Sus scrofa)

The widespread application of per- and polyfluoroalkyl substances (PFAS) resulted in ubiquitous environmental contamination. Understanding the PFAS tissue distribution in mammals and humans is crucial for the assessment of potential health risks. The levels of eleven PFAS were determined by UPLC-MS/MS in plasma and various tissues of wild boar (n = 82) hunted in Germany. The most prevalent PFAS (PFOA, PFNA, PFHxS and PFOS) were detected in all analyzed samples. The median level of the sum (Σ 4PFAS) was highest in liver (90.2 μg/kg), followed by kidney (9.45 μg/kg), plasma (7.63 μg/L), lung (6.84 μg/kg), heart muscle (2.60 μg/kg), spleen (2.46 μg/kg), and skeletal muscle (1.03 μg/kg). Consumption of a single portion (125 g) of liver containing the Σ 4PFAS median level would result in a 36.6-fold exceedance of the tolerable weekly intake (TWI) of EFSA in a 70 kg-person. The accumulation (calculated as tissue/plasma ratio) of perfluoroalkyl carboxylic acids with ηpfc = 8-13 in lung, spleen, muscle and heart tissues increased with molecule size, indicating passive mechanisms of distribution driven by hydrophobicity. In contrast, liver and kidney distribution coefficients scattered, indicating additional involvement of chain-length dependent active transport processes. The highest accumulation was observed for PFOS in the liver (median tissue/plasma ratio 18.0). The shortest PFAS included in the study (PFHxA, PFHpA, PFOA, PFBS and PFHxS) did not accumulate in any of the tissues, probably due to strong binding to blood proteins like serum albumin and their relative polarity impeding passive membrane diffusion.

Perfluorooctanoic acid increases serum cholesterol in a PPARα-dependent manner in female mice

Per- and polyfluoroalkyl substances (PFAS) are a large group of persistent chemicals that are pervasive in the environment leading to widespread exposure for humans. Perfluorooctanoic acid (PFOA), one of the most commonly measured PFAS in people, disrupts liver and serum lipid homeostasis as shown in animal toxicity and human epidemiological studies. We tested the hypothesis that the effects of PFOA exposure in mice expressing mouse PPARα (mPPARα) are driven largely through PPARα-dependent mechanisms while non-PPARα dependent mechanisms will be more apparent in mice expressing human PPARα (hPPARα). Female and male mPPARα, hPPARα, and PPARα null mice were exposed to PFOA (0.5, 1.4 or 6.2 mg PFOA/L) via drinking water for 14 weeks. Concurrently, mice consumed an American diet containing human diet-relevant amounts of fat and cholesterol. Here, we focused on the effects in female mice, given the dearth of data reported on PFAS-induced effects in females. Increasing the duration of PFOA exposure reduced weight gain in all genotypes of female mice while end-of-study body fat was lower in PFOA exposed hPPARα and PPARα null mice. Serum cholesterol, but not triacylglyceride, concentrations were increased by PFOA exposure in a PPARα-dependent manner. Hepatic triacylglycerides were higher in vehicle-exposed mPPARα and PPARα null mice than hPPARα mice, and PFOA significantly reduced concentrations in mPPARα and PPARα null mice only. In contrast, PFOA increased hepatic cholesterol content in a PPARα-dependent manner. Changes in liver and serum cholesterol may be explained by a strong, PPARα-dependent downregulation of Cyp7a1 expression. PFOA significantly increased PPARα target gene expression in mPPARα mice. Other nuclear receptors were examined: CAR target gene expression was only induced by PFOA in hPPARα and PPARα null mice. PXR target gene expression was induced by PFOA in all genotypes. Results were similar in male mice with two exceptions: (1) vehicle-exposed male mice of all genotypes were equally susceptible to diet-induced hepatic steatosis; (2) male mice drank less water, resulting in lower serum PFOA levels, which may explain the less significant changes in lipid endpoints. Overall, our results show that PFOA modifies triacylglyceride and cholesterol homeostasis independently and that PPARα plays an important role in PFOA-induced increases in liver and serum cholesterol.

Perfluoroalkyl acids interact with major human blood protein fibrinogen: Experimental and computation study

PFAS (per- and polyfluorinated alkyl substances) are synthetic compounds prized for their stability across various industries, but they pose an increasing threat to the environment and human health. Following the regulation of long-chain PFAS, short-chain and ultra-short-chain molecules have been introduced as substitutes, yet their bioaccumulation potential remains poorly understood. In this study, we combined experimental (intrinsic fluorescence, microscale thermophoresis, clotting assays) and computational approaches to investigate how trifluoroacetic acid, perfluorobutanoic acid, and perfluorooctanoic acid bind to fibrinogen, a key human blood protein. All tested perfluoroalkyl acids (PFAAs) exhibited moderate binding affinity (Kd in the 10-4-10-5 M range), yet circular dichroism and fibrin clot formation assays revealed no functional impairment of fibrinogen. Molecular docking indicated distinct, chain-length-specific binding sites, suggesting multiple routes for PFAAs to interact with fibrinogen without disrupting its primary biological role. These findings challenge the assumption that short-chain PFAS are less bioaccumulative and underscore the need for further research into their long-term health impacts, particularly given their widespread presence in the environment and potential accumulation in human blood.

Integrated Spheroid-to-Population Framework for Evaluating PFHpA-Associated Metabolic Dysfunction and Steatotic Liver Disease

The rising prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), particularly among pediatric populations, requires identification of modifiable risk factors to control disease progression. Per- and polyfluoroalkyl substances (PFAS) have emerged as potential contributors to liver damage; however, their role in the etiology of MASLD remains underexplored. This study aimed to bridge the gap between human epidemiological data and in vitro experimental findings to elucidate the effect of perfluoroheptanoic acid (PFHpA), a short chain, unregulated PFAS congener on MASLD development. Our analysis of the Teen-LABS cohort, a national multi-site study on obese adolescents undergoing bariatric surgery, revealed that doubling of PFHpA plasma levels was associated with an 80% increase in MASLD risk (OR, 1.8; 95% CI: 1.3-2.5) based on liver biospies. To further investigate the underlying mechanisms, we used 3D human liver spheroids and single-cell transcriptomics to assess the effect of PFHpA on hepatic metabolism. Integrative analysis identified dysregulation of common pathways in both human and spheroid models, particularly those involved in innate immunity, inflammation, and lipid metabolism. We applied the latent unknown clustering with integrated data (LUCID) model to assess associations between PFHpA exposure, multiomic signatures, and MASLD risk. Our results identified a proteome profile with significantly higher odds of MASLD (OR = 7.1), whereas a distinct metabolome profile was associated with lower odds (OR = 0.51), highlighting the critical role of protein dysregulation in disease pathogenesis. A translational framework was applied to uncover the molecular mechanisms of PFAS-induced MASLD in a cohort of obese adolescents. Identifying key molecular mechanisms for PFAS-induced MASLD can guide the development of targeted prevention and treatment.

Per- and Polyfluoroalkyl Substances (PFAS) in Consumer Products: An Overview of the Occurrence, Migration, and Exposure Assessment

Per- and polyfluoroalkyl substances (PFASs) have been widely used in the production of consumer products globally due to the excellent water and oil resistance and anti-fouling properties. The multiple toxic effects of some PFASs also pose a threat to human health and ecosystem, and the frequent use of certain consumer products increased the risk of human exposure to PFASs. More data on the occurrence, concentration, and migration of PFASs in consumer products is urgently needed to address the possible risks posed by exposure to consumer products. This paper reviews the PFAS concentrations found, the migration characteristics known, and the exposure risks of PFASs arising from several types of consumer products over the last five years. The types of consumer products considered here include food contact materials, textiles, and disposable personal hygiene products. The influence of different factors on the migration process of PFASs from these products are summarized and discussed. Additionally, the main approaches and models of exposure assessment are evaluated and summarized. Current challenges and future research prospects in this field are discussed with a view to providing guidance for the future assessment and regulation of PFASs in consumer products.

Association between exposure to perfluoroalkyl and polyfluoroalkyl substances with estimated glomerular filtration rate: Mediating role of serum albumin

BACKGROUND

Previous studies have demonstrated perfluoroalkyl and polyfluoroalkyl substances (PFAS) impact renal function, with albumin playing dominant role in their transport and accumulation. However, the mediating role of albumin in PFAS-induced renal impairment and the identification of sensitive populations remain uninvestigated.

METHODS

This study included 9328 individuals from NHANES 1999-2018 with data on serum PFAS, creatinine, albumin, and covariates. The estimated glomerular filtration rate (eGFR) was calculated using standardized creatinine. Associations between perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA) with eGFR and the risk of decreased renal function (eGFR < 90 vs. eGFR ≥ 90) using linear and logistic regression, weighted quantile sum (WQS) regression, Bayesian kernel machine regression (BKMR), and restricted cubic spline (RCS) analyses. Subgroup analyses identified sensitive populations. Mediation analysis was performed to examine the mediating role of albumin. Comparative toxicology databases identified relevant genes for mechanistic exploration.

RESULTS

Ln-transformed PFOA (β = -1.91, 95 % CI: -2.82 to -1), PFOS (β = -1.48, 95 % CI: -2.19 to -0.78) and PFHxS (β = -0.94, 95 % CI: -1.65 to -0.23) were negatively correlated with eGFR. PFOA (aOR = 1.21, 95 % CI: 1.1-1.32), PFOS (aOR = 1.2, 95 % CI: 1.12-1.29), and PFHxS (aOR = 1.13, 95 % CI: 1.05-1.21) were positively correlated with the risk of decreased renal function. Subgroup analyses indicated that individuals ≤ 45 years, females and other races were more sensitive. Albumin mediated 18.2 %, 16.4 %, 29.8 %, and 18.7 % of the negative effects of PFOA, PFOS, PFHxS, and PFNA on eGFR, respectively. Functional enrichment analysis suggested PFAS impair renal function by affecting lipid metabolism and increasing oxidative stress.

CONCLUSIONS

PFAS exposure is negatively associated with eGFR and positively associated with the risk of decreased renal function, with albumin playing a partial mediating role.

Broad PFAS binding with fatty acid binding protein 4 is enabled by variable binding modes

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous pollutants that bioaccumulate in wildlife and humans, yet the molecular basis of their protein interactions remains poorly understood. Here, we show that human adipocyte fatty acid-binding protein (FABP4) can bind a diverse array of PFAS, including next-generation replacements for legacy chemicals and longer-chain perfluorocarboxylic acids. Shorter-chain PFAS, although weaker binders, still displayed measurable affinities-surpassing those of their nonfluorinated analogs. We determined crystal structures of FABP4 bound to perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDA), and perfluorohexadecanoic acid (PFHxDA), revealing three distinct binding modes. Notably, PFOA binds in two separate sites, and two distinct conformations define single-ligand binding of PFDA and PFHxDA. These arrangements enhance hydrophobic interactions within the binding cavity and likely explain the low micromolar dissociation constants observed in fluorescence competition assays. Our findings underscore the critical roles of chain length, headgroup functionality, and protein conformation in PFAS-FABP4 interactions. Given the emerging implications of the role of FABP4 in endocrine function, even subtle PFAS-induced perturbations could affect metabolic regulation and disease risk. Overall, this work highlights the value of direct structural and biochemical insights into PFAS-FABP4 interactions and paves the way for future research on PFAS transport and toxicological outcomes.

Effects of per- and polyfluoroalkyl substances on the liver: Human-relevant mechanisms of toxicity

Per- and polyfluoroalkyl substances (PFAS) are abundantly used in a plethora of products with applications in daily life. As a result, PFAS are widely distributed in the environment, thus providing a source of exposure to humans. The majority of human exposure to PFAS is attributed to the human diet, which encompasses drinking water. Their chemical nature grants persistent, accumulative and toxic properties, which are currently raising concerns. Over the past few years, adverse effects of PFAS on different organs have been repeatedly documented. Numerous epidemiological studies established a clear link between PFAS exposure and liver toxicity. Likewise, effects of PFAS on liver homeostasis, lipid metabolism, bile acid metabolism and hepatocarcinogenesis have been reported in various in vitro and in vivo studies. This review discusses the role of PFAS in liver toxicity with special attention paid to human relevance as well as to the mechanisms underlying the hepatotoxic effects of PFAS. Future perspectives and remaining knowledge gaps were identified to enhance future PFAS risk assessment.

Exposure to per- and polyfluoroalkyl substances and alterations in plasma microRNA profiles in children

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that persist in the environment and can accumulate in humans, leading to adverse health effects. MicroRNAs (miRNAs) are emerging biomarkers that can advance the understanding of the mechanisms of PFAS effects on human health. However, little is known about the associations between PFAS exposures and miRNA alterations in humans.

OBJECTIVE

To investigate associations between PFAS concentrations and miRNA levels in children.

METHODS

Data from two distinct cohorts were utilized: 176 participants (average age 17.1 years; 75.6% female) from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) cohort in the United States, and 64 participants (average age 6.5 years, 39.1% female) from the Rhea study, a mother-child cohort in Greece. PFAS concentrations and miRNA levels were assessed in plasma samples from both studies. Associations between individual PFAS and plasma miRNA levels were examined after adjusting for covariates. Additionally, the cumulative effects of PFAS mixtures were evaluated using an exposure burden score. Ingenuity Pathways Analysis was employed to identify potential disease functions of PFAS-associated miRNAs.

RESULTS

Plasma PFAS concentrations were associated with alterations in 475 miRNAs in the Teen-LABs study and 5 miRNAs in the Rhea study (FDR p < 0.1). Specifically, plasma PFAS concentrations were consistently associated with decreased levels of miR-148b-3p and miR-29a-3p in both cohorts. Pathway analysis indicated that PFAS-related miRNAs were linked to numerous chronic disease pathways, including cardiovascular diseases, inflammatory conditions, and carcinogenesis.

CONCLUSION

Through miRNA screenings in two independent cohorts, this study identified both known and novel miRNAs associated with PFAS exposure in children. Pathway analysis revealed the involvement of these miRNAs in several cancer and inflammation-related pathways. Further studies are warranted to enhance our understanding of the relationships between PFAS exposure and disease risks, with miRNA emerging as potential biomarkers and/or mediators in these complex pathways.

Unbound Fractions of PFAS in Human and Rodent Tissues: Rat Liver a Suitable Proxy for Evaluating Emerging PFAS?

Adverse health effects associated with exposures to perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a concern for public health and are driven by their elimination half-lives and accumulation in specific tissues. However, data on PFAS binding in human tissues are limited. Accumulation of PFAS in human tissues has been linked to interactions with specific proteins and lipids in target organs. Additional data on PFAS binding and unbound fractions (funbound) in whole human tissues are urgently needed. Here, we address this gap by using rapid equilibrium dialysis to measure the binding and funbound of 16 PFAS with 3 to 13 perfluorinated carbon atoms (ηpfc = 3-13) and several functional headgroups in human liver, lung, kidney, heart, and brain tissue. We compare results to mouse (C57BL/6 and CD-1) and rat tissues. Results show that funbound decreases with increasing fluorinated carbon chain length and hydrophobicity. Among human tissues, PFAS binding was generally greatest in brain > liver ≈ kidneys ≈ heart > lungs. A correlation analysis among human and rodent tissues identified rat liver as a suitable surrogate for predicting funbound for PFAS in human tissues (R2 ≥ 0.98). The funbound data resulting from this work and the rat liver prediction method offer input parameters and tools for toxicokinetic models for legacy and emerging PFAS.

Comparative analysis of UV-initiated ARPs for degradation of the emerging substitute of perfluorinated compounds: Does defluorination mean the sole factor?

Due to the increasing attention for the residual of per- and polyfluorinated compounds in environmental water, Sodium p-Perfluorous Nonenoxybenzenesulfonate (OBS) have been considered as an alternative solution for perfluorooctane sulfonic acid (PFOS). However, recent detections of elevated OBS concentrations in oil fields and Frontal polymerization foams have raised environmental concerns leading to the decontamination exploration for this compound. In this study, three advanced reduction processes including UV-Sulfate (UV-SF), UV-Iodide (UV-KI) and UV-Nitrilotriacetic acid (UV-NTA) were selected to evaluate the removal for OBS. Results revealed that hydrated electrons (eaq-) dominated the degradation and defluorination of OBS. Remarkably, the UV-KI exhibited the highest removal rate (0.005 s-1) and defluorination efficiency (35 %) along with the highest concentration of eaq- (K = -4.651). Despite that nucleophilic attack from eaq- on sp2 carbon and H/F exchange were discovered as the general mechanism, high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC/Q-TOF-MS) analysis with density functional theory (DFT) calculations revealed the diversified products and routes. Intermediates with lowest fluorine content for UV-KI were identified, the presence nitrogen-containing intermediates were revealed in the UV-NTA. Notably, the nitrogen-containing intermediates displayed the enhanced toxicity, and the iodine poly-fluorinated intermediates could be a potential-threat compared to the superior defluorination performance for UV-KI.

PFHpA alters lipid metabolism and increases the risk of metabolic dysfunction-associated steatotic liver disease in youth-a translational research framework

To address the growing epidemic of liver disease, particularly in pediatric populations, it is crucial to identify modifiable risk factors for the development and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Per- and polyfluoroalkyl substances (PFAS) are persistent ubiquitous chemicals and have emerged as potential risk factors for liver damage. However, their impact on the etiology and severity of MASLD remains largely unexplored in humans. This study aims to bridge the gap between human and in vitro studies to understand how exposure to perfluoroheptanoic acid (PFHpA), one of the emerging PFAS replacements which accumulates in high concentrations in the liver, contributes to MASLD risk and progression. First, we showed that PFHpA plasma concentrations were significantly associated with increased risk of MASLD in obese adolescents. Further, we examined the impact of PFHpA on hepatic metabolism using 3D human liver spheroids and single-cell transcriptomics to identify major hepatic pathways affected by PFHpA. Next, we integrated the in vivo and in vitro multi-omics datasets with a novel statistical approach which identified signatures of proteins and metabolites associated with MASLD development triggered by PFHpA exposure. In addition to characterizing the contribution of PFHpA to MASLD progression, our study provides a novel strategy to identify individuals at high risk of PFHpA-induced MASLD and develop early intervention strategies. Notably, our analysis revealed that the proteomic signature exhibited a stronger correlation between both PFHpA exposure and MASLD risk compared to the metabolomic signature. While establishing a clear connection between PFHpA exposure and MASLD progression in humans, our study delved into the molecular mechanisms through which PFHpA disrupts liver metabolism. Our in vitro findings revealed that PFHpA primarily impacts lipid metabolism, leading to a notable increase of lipid accumulation in human hepatocytes after PFHpA exposure. Among the pathways involved in lipid metabolism in hepatocytes, regulation of lipid metabolism by PPAR-a showed a remarkable activation. Moreover, the translational research framework we developed by integrating human and in vitro data provided us biomarkers to identify individuals at a high risk of MASLD due to PFHpA exposure. Our framework can inform policies on PFAS-induced liver disease and identify potential targets for prevention and treatment strategies.

Changes in plasma concentrations of per- and Polyfluoroalkyl substances after bariatric surgery in adolescents from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study

Exposure to per- and poly-fluoroalkyl substances (PFAS) is ubiquitous due to their persistence in the environment and in humans. Extreme weight loss has been shown to influence concentrations of circulating persistent organic pollutants (POPs). Using data from the multi-center perspective Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) cohort, we investigated changes in plasma-PFAS in adolescents after bariatric surgery. Adolescents (Mean age = 17.1 years, SD = 1.5 years) undergoing bariatric surgery were enrolled in the Teen-LABS study. Plasma-PFAS were measured at the time of surgery and then 6-, 12-, and 36 months post-surgery. Linear mixed effect models were used to evaluate longitudinal changes in plasma-PFAS after the time of bariatric surgery. This study included 214 adolescents with severe obesity who had available longitudinal measures of plasma-PFAS and underwent bariatric surgery between 2007 and 2012. Underlying effects related to undergoing bariatric surgery were found to be associated with an initial increase or plateau in concentrations of circulating PFAS up to 6 months after surgery followed by a persistent decline in concentrations of 36 months (p < 0.001 for all plasma-PFAS). Bariatric surgery in adolescents was associated with a decline in circulating PFAS concentrations. Initially following bariatric surgery (0-6 months) concentrations were static followed by decline from 6 to 36 months following surgery. This may have large public health implications as PFAS are known to be associated with numerous metabolic related diseases and the significant reduction in circulating PFAS in individuals who have undergone bariatric surgery may be related to the improvement of such metabolic related diseases following bariatric surgery.

Species Difference? Bovine, Trout, and Human Plasma Protein Binding of Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) strongly bind to proteins and lipids in blood, which govern their accumulation and distribution in organisms. Understanding the plasma binding mechanism and species differences will facilitate the quantitative in vitro-to-in vivo extrapolation and improve risk assessment of PFAS. We studied the binding mechanism of 16 PFAS to bovine serum albumin (BSA), trout, and human plasma using solid-phase microextraction. Binding of anionic PFAS to BSA and human plasma was found to be highly concentration-dependent, while trout plasma binding was linear for the majority of the tested PFAS. At a molar ratio of PFAS to protein ν < 0.1 molPFAS/molprotein, the specific protein binding of anionic PFAS dominated their human plasma binding. This would be the scenario for physiological conditions (ν < 0.01), whereas in in vitro assays, PFAS are often dosed in excess (ν > 1) and nonspecific binding becomes dominant. BSA was shown to serve as a good surrogate for human plasma. As trout plasma contains more lipids, the nonspecific binding to lipids affected the affinities of PFAS for trout plasma. Mass balance models that are parameterized with the protein-water and lipid-water partitioning constants (chemical characteristics), as well as the protein and lipid contents of the plasma (species characteristics), were successfully used to predict the binding to human and trout plasma.

Individual and joint associations of per- and polyfluoroalkyl substances (PFAS) with gallstone disease in adults: A cross-sectional study

Disturbances in the enterohepatic circulation are important biological mechanisms for causing gallstones and also have important effects on the metabolism of Per- and polyfluoroalkyl substances (PFAS). Moreover, PFAS is associated with sex hormone disorder which is another important cause of gallstones. However, it remains unclear whether PFAS is associated with gallstones. In this study, we used logistic regression, restricted cubic spline (RCS), quantile g-computation (qg-comp), Bayesian kernel machine regression (BKMR), and subgroup analysis to assess the individual and joint associations of PFAS with gallstones and effect modifiers. We observed that the individual associations of perfluorodecanoic acid (PFDeA) (OR: 0.600, 95% CI: 0.444 to 0.811), perfluoroundecanoic acid (PFUA) (OR: 0.630, 95% CI: 0.453 to 0.877), n-perfluorooctane sulfonic acid (n-PFOS) (OR: 0.719, 95% CI: 0.571 to 0.906), and perfluoromethylheptane sulfonic acid isomers (Sm-PFOS) (OR: 0.768, 95% CI: 0.602 to 0.981) with gallstones were linearly negative. Qg-comp showed that the PFAS mixture (OR: 0.777, 95% CI: 0.514 to 1.175) was negatively associated with gallstones, but the difference was not statistically significant, and PFDeA had the highest negative association. Moreover, smoking modified the association of perfluorononanoic acid (PFNA) with gallstones. BKMR showed that PFDeA, PFNA, and PFUA had the highest groupPIP (groupPIP = 0.93); PFDeA (condPIP = 0.82), n-perfluorooctanoic acid (n-PFOA) (condPIP = 0.68), and n-PFOS (condPIP = 0.56) also had high condPIPs. Compared with the median level, the joint association of the PFAS mixture with gallstones showed a negative trend; when the PFAS mixture level was at the 70th percentile or higher, they were negatively associated with gallstones. Meanwhile, when other PFAS were fixed at the 25th, 50th, and 75th percentiles, PFDeA had negative associations with gallstones. Our evidence emphasizes that PFAS is negatively associated with gallstones, and more studies are needed in the future to definite the associations of PFAS with gallstones and explore the underlying biological mechanisms.

Species-Specific Unbound Fraction Differences in Highly Bound PFAS: A Comparative Study across Human, Rat, and Mouse Plasma and Albumin

Per- and polyfluoroalkyl substances (PFAS) are a diverse group of fluorinated compounds which have yet to undergo comprehensive investigation regarding potential adverse health effects and bioaccumulative properties. With long half-lives and accumulative properties, PFAS have been linked to several toxic effects in both non-clinical species such as rat and mouse as well as human. Although biological impacts and specific protein binding of PFAS have been examined, there is no study focusing on the species-specific fraction unbound (fu) in plasma and related toxicokinetics. Herein, a presaturation equilibrium dialysis method was used to measure and validate the binding of 14 individual PFAS with carbon chains containing 4 to 12 perfluorinated carbon atoms and several functional head-groups to albumin and plasma of mouse (C57BL/6 and CD-1), rat, and human. Equivalence testing between each species-matrix combination showed positive correlation between rat and human when comparing fu in plasma and binding to albumin. Similar trends in binding were also observed for mouse plasma and albumin. Relatively high Spearman correlations for all combinations indicate high concordance of PFAS binding regardless of matrix. Physiochemical properties of PFAS such as molecular weight, chain length, and lipophilicity were found to have important roles in plasma protein binding of PFAS.

Occurrence of Major Perfluorinated Alkylate Substances in Human Blood and Target Organs

Human exposure to perfluorinated alkylate substances (PFASs) is usually assessed from the concentrations in serum or plasma, assuming one-compartment toxicokinetics. To characterize body distributions of major PFASs, we obtained and extracted tissue samples from 19 forensic autopsies of healthy adult subjects who had died suddenly and were not known to have elevated levels of PFAS exposure. As target organs of toxicological importance, we selected the liver, kidneys, lungs, spleen, and brain, as well as whole blood. Samples weighing about 0.1 g were analyzed by liquid chromatography coupled to triple mass spectrometers. Minor variations in PFAS concentrations were found between the kidney cortex and medulla and between lung lobes. Organ concentrations of perfluorooctanoic sulfonate (PFOS) and perfluorononanoate (PFNA) correlated well with blood concentrations, while perfluorooctanoate (PFOA) and perfluorohexanoic sulfonate (PFHxS) showed more variable associations. Likewise, the liver concentrations correlated well with those of other organs. Calculations of relative distributions were carried out to assess the interdependence of organ retentions. Equilibrium model predictions largely explained the observed PFAS distributions, except for the brain. Although the samples were small and affected by a possible lack of homogeneity, these findings support the use of blood-PFAS concentrations as a measure of PFAS exposure, with the liver possibly acting as the main organ of retention.