A Bayesian hierarchical model for estimating national PFAS drinking water occurrence

Invited Perspective: Challenges in Evaluating the Effect of Per- and Polyfluoroalkyl Substance Mixtures on Polycystic Ovarian Syndrome

Per- and polyfluoroalkyl substances (PFASs) are known as ‘forever chemical’, commonly used in commercial and daily-life products. Due to their special physico-chemical characteristics, PFASs have been found in various environmental matrices, and can be exposed to organisms and humans. The present review outlines the current state of knowledge on the occurrence of PFASs in the environment, human exposure routes, biomonitoring data, and metabolic mechanism. Diet is considered to be the main route of PFASs exposure, and these compounds enter the human body through accumulation in the food chain, particularly through biomagnification by aquatic organisms. Detection of different PFASs has been reported in human samples including urine, blood, serum, breast milk, hair, and nails, among which perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) are most frequently identified in serum and short-chain PFASs are frequently detected in urine. After entering into human body, particular biotransformation pathways of PFASs in mammals are primarily through hydroxylation, carboxylation, and enzymatic conversion. PFASs can affect metabolism by increasing inflammation, peroxisome proliferator-activated receptor (PPAR) signaling. Long-chain PFASs may cause stronger immunosuppressive effects and higher bioaccumulation potential than short-chain PFASs. PFASs and their metabolites induce similar or even more toxic effects by activating the same signaling associated with endogenous metabolism, thereby affecting lipid metabolism and leading to metabolic disorders and related diseases. This review may contribute to the human exposure risk of PFASs, especially from the respective of human exposure level and metabolic transformation.

BACKGROUND AND AIM: Per- and polyfluoroalkyl substances (PFAS) are a group of water-soluble chemicals of concern due to their persistence, widespread human exposure and associated adverse health outcomes across all life stages. Drinking water is one of the main routes of human exposure to PFAS. METHODS: We assessed 38 PFAS in 64 drinking water samples sourced from tap water (N=42, one per postal code), bottled (N=11), activated carbon (N=6) and reverse osmosis (N=5) filtered tap water in Barcelona, Spain. Liquid chromatography coupled tandem mass spectrometry was used to determine PFAS. Physico-chemical properties including residual chlorine, total organic carbon and conductivity were also measured. Water consumption habits of study participants (N=39) were collected through online questionnaires. RESULTS:The most abundant PFAS in unfiltered tap water were perfluoropentanoic acid (PFPeA) [3 ng/L (2.0-5.0)] -among 64% samples above the limit of quantification (LOQ)-, perfluorohexanoic acid (PFHxA) [14 ng/L (10-18)] -31%-, perfluoroheptanoic acid (PFHpA) [3 ng/L (2.25-4)] -52%-, perfluorooctanoic acid (PFOA) [11 ng/L (10-12)] -12%-, perfluorobutane sulfonic acid (PFBS) [9 ng/L (6.5-14.5)] -64%-, and perfluorooctane sulfonate (PFOS) [12.5 ng/L (10-14)] -52%-, with corresponding median (interquartile range, IQR). The median concentration of total PFAS was 29 ng/L (IQR=24-51), among 79% of tap water samples with PFAS LOQ. Individual PFAS displayed a range of positive correlations (Spearman, two-tailed) between r=0.36 (p=0.02) and r=0.67, (p0.001). Conductivity showed a geographical pattern linked to the tap water source, and a positive correlation (r=0.75, p0.001) with total PFAS. Reverse osmosis removed PFAS from tap water, while activated carbon filters did not. PFAS were not detected in bottled water. The mean consumption of water at home was 1.4L/day, and 0.8L/day outside of home. The main source of water was tap (43%) at home, and bottled or filtered (37.5% each) outside. CONCLUSIONS:Concentrations were below the EU Drinking Water Directive 2020/2184 PFAS Total parametric value (100 ng/L). KEYWORDS: PFAS, Exposure assessment, Chemical exposures, Water quality

Per- and polyfluoroalkyl substances (PFASs) are a diverse class of >4700 chemicals used in commercial products and industrial processes. Concerns surrounding PFASs are principally due to their widespread occurrence in humans and the environment and links to adverse health effects. One of the lesser known uses for PFASs is in cosmetic products (CPs) which come into contact with the skin (e.g. hair products, powders, sunblocks, etc.). In the present work, thirty-one CPs from five product categories (cream, foundation, pencil, powder and shaving foam) were analyzed for 39 PFASs by liquid chromatography-tandem mass spectrometry, as well as extractable organic fluorine (EOF) and total fluorine (TF) by combustion ion chromatography (CIC). This multi-platform approach enabled determination of the fraction of fluorine accounted for by known PFASs (i.e. fluorine mass balance). Foundations and powders contained 25 different PFASs with the most frequently detected being perfluorinated carboxylic acids (perfluoroheptanoic acid and perfluorohexanoic acid) and polyfluoroalkyl phosphate esters (PAPs). Σ14PAP concentrations up to 470 μg g-1 were measured in products listing mixtures of PAPs as an ingredient. For all samples, Σ39PFAS concentrations only explained a small fraction of the EOF and TF, pointing to the presence of unknown organic and/or inorganic fluorinated substances, including polymers. While creams, pencil and shaving foams did not contain measurable concentrations of any of the 39 PFASs targeted here, CIC revealed high to moderate TF content. Overall, these data highlight the need for further investigations into the occurrence of PFASs in CPs and their importance with regards to human and environmental exposure.

A flow-through cell for the electrochemical oxidation of perfluoroalkyl substances in landfill leachates

Treatment of poly- and perfluoroalkyl substances in U.S. full-scale water treatment systems

Per-and Polyfluoroalkyl Substances (PFAS), which includes PFOS and PFOA, are recognized as the most important class of emerging contaminants due to their widespread presence in wildlife and humans, their environmental persistence, bioaccumulative potential, and toxicity. Low environmental pH conditions affect the state and physicochemical properties of PFAS, which in turn impacts on their toxicity. Sparse information is available regarding the effect of these compounds on microorganisms, and the possible associated knock-on effect on ecosystem services. The purpose of this study is to investigate the ability of E. coli to tolerate stress in the presence of PFAS compounds. To this end, we carried out phenotypic comparisons of E. coli exposed to a series of environmental conditions in the presence and absence of PFOA and PFOS. Quite remarkably, E. coli growth was not affected by the presence of PFOA and PFOS up to 500 mg/L. The survival of E. coli at pH3, however, decreased by more than three-fold when the medium was supplemented with PFOA. PFOA and PFOS were also found to decrease the growth rates of E. coli in minimal media in the presence of 0.75 and 1M NaCl. We are currently screening further stresses of environmental relevance with the aim to conduct molecular investigations to examine the mechanisms underpinning the effect of PFAS exposure on bacterial stress tolerance. This work will provide some insights into the impact of PFAS on microorganisms, which should shed new light on the assessment of the ecological effects of PFAS.

New insight into PFOS transformation pathways and the associated competitive inhibition with other perfluoroalkyl acids via photoelectrochemical processes using GOTiO2 film photoelectrodes

Perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonic acid (PFHxS) have been listed under the Stockholm Convention and are being progressively phased out worldwide; environmental prevalence and human exposure to other poly- and perfluoroalkyl substances (PFASs) with different structures are on the rise. However, the toxic effects and mechanisms of other PFASs remain unclear. This study explored and compared the estrogenic effects and underlying mechanisms of eight typical PFASs. PFOA, PFOS, PFHxS, and perfluorooctane sulfonamide (PFOSA) promoted the proliferation of MCF-7 cells, with PFOSA exhibiting the strongest estrogenic effect among the eight targeted PFASs. Specifically, for the PFASs with the same number of carbons and different functional groups, the estrogenic effect is in the decreasing order of PFOSA (sulfonamide group) > PFOS (sulfonic acid group) > PFOA (carboxylic acid group). The observed enhancement was likely caused by estrogen receptor (ER) activation, as an ER antagonist significantly inhibited the pro-proliferation effect. Luciferase reporter gene assays, fluorescence competitive binding assays, and molecular docking simulation were used to furnish supplementary evidence for the direct action of PFASs on the ER. PFOA, PFHxS, PFOS, and PFOSA can activate ER transcriptional activity and bind to the ER, demonstrating that ER is a potential target of PFASs. For PFOA, PFOS, and PFOSA, the rank order of binding affinities with ER in fluorescence competitive binding assays and the calculated binding energy in molecular docking simulation were consistent with the results of the cell proliferation experiment and luciferase reporter gene assays, suggesting that receptor binding affinity also plays a critical role in the activation effect of the ER pathway. Overall, our results indicate the estrogenic effects of other PFASs through ER-mediated pathways and elucidate the molecular mechanism for the different activity of eight PFASs, as well as suggest that PFOS precursors require more attention when determining the environmental risk of PFASs.

Distribution, partitioning behavior and potential source of legacy and alternative per- and polyfluoroalkyl substances (PFASs) in water and sediments from a subtropical Gulf, South China Sea

Spatial distribution, vertical profiles and transport of legacy and emerging per- and polyfluoroalkyl substances in the Indian Ocean

Multi-media occurrence, bioaccumulation, and exposure assessment of PFAS across a Midwestern U.S. State.

Per- and Polyfluoroalkyl Substances (PFAS) bioaccumulate in the human body, presenting potential health risks and cellular toxicity. Their transport mechanisms and interactions with tissues and the circulatory system require further investigation. This study investigates the interaction mechanisms of six PFAS with Human Serum Albumin (HSA) using multi-spectroscopy, DFT and a molecular dynamics approach. Multi-spectral analysis shows that perfluorononanoic acid (PFNA) has the best binding capabilities with HSA. The order of binding constants (298 K) is as follows: "Perfluorononanoic Acid (PFNA, 7.81 × 106 L·mol-1) > Perfluoro-2,5-dimethyl-3,6-dioxanonanoic Acid (HFPO-TA, 3.70 × 106 L·mol-1) > Perfluorooctanoic Acid (PFOA, 2.27 × 105 L·mol-1) > Perfluoro-3,6,9-trioxadecanoic Acid (PFO3DA, 1.59 × 105 L·mol-1) > Perfluoroheptanoic Acid (PFHpA, 4.53 × 103 L·mol-1) > Dodecafluorosuberic Acid (DFSA, 1.52 × 103 L·mol-1)". Thermodynamic analysis suggests that PFNA and PFO3DA's interactions with HSA are exothermic, driven primarily by hydrogen bonds or van der Waals interactions. PFHpA, DFSA, PFOA, and HFPO-TA's interactions with HSA, on the other hand, are endothermic processes primarily driven by hydrophobic interactions. Competitive probe results show that the main HSA-PFAS binding site is in the HSA structure's subdomain IIA. These findings are also consistent with the findings of molecular docking. Molecular dynamics simulation (MD) analysis further shows that the lowest binding energy (-38.83 kcal/mol) is fund in the HSA-PFNA complex, indicating that PFNA binds more readily with HSA. Energy decomposition analysis also indicates that van der Waals and electrostatic interactions are the main forces for the HSA-PFAS complexes. Correlation analysis reveals that DFT quantum chemical descriptors related to electrostatic distribution and characteristics like ESP and ALIE are more representative in characterizing HSA-PFAS binding. This study sheds light on the interactions between HSA and PFAS. It guides health risk assessments and control strategies against PFAS, serving as a critical starting point for further public health research.

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants, but few studies have explored the relationship between PFAS and levels of metabolic syndrome (MetS) in the population. The available evidence of an association is also conflicting. We selected adults and adolescents with complete PFAS data from the National Health and Nutrition Examination Survey conducted between 2003 and 2018. We analyzed the association between PFAS and MetS using multivariate logistic regression models and evaluated potential nonlinear relationships with restricted cubic spline models. Additionally, we employed weighted quantile sum (WQS) regressions to uncover the multiple exposure effects and relative weights of each PFAS. Finally, we conducted a series of sensitivity analyses to test the robustness of our findings. In this population-based study, we analyzed data from a total of 4,973 adults, aged 20–85 years, and 1,381 adolescents, aged 12–19 years. Using fully adjusted multivariate logistic regression models, we found that serum levels of perfluorodecanoate (PFDA) [0.65 (0.50, 0.85)] and total PFAS [0.92 (0.85, 0.99)] were negatively associated with the prevalence of MetS in adults. Similarly, in adolescents, we observed negative correlations between the prevalence of MetS and levels of PFDA [0.55 (0.38, 0.80)], perfluorooctanoic acid (PFOA) [0.62 (0.39, 1.00)], perfluorooctane sulfonic acid (PFOS) [0.59 (0.36, 0.96)], and total PFAS [0.61 (0.37, 0.99)]. Additionally, our study identified statistically significant negative associations between serum levels of PFAS and certain components of MetS, primarily elevated fasting glucose and lower high-density lipoprotein cholesterol. Our study found that PFAS was associated with a lower prevalence of MetS in both adults and adolescents, offering new insights into the relationship between PFAS and metabolic health. Interestingly, however, we observed conflicting findings across the components of MetS. Specifically, we observed that PFAS had a negative correlation with some metrics and a positive correlation with others. These conflicting results point to a complex interplay between PFAS and various metrics of metabolic health.

Preconception exposure to perfluoroalkyl and polyfluoroalkyl substances and couple fecundity: A couple-based exploration