From Dawn to Now: The Evolution of PFAS Research Trends

Estimation of Serum PFOA Concentrations from Drinking and Non-Drinking Water Exposures.

Perfluoroalkyl substances (PFAS) are the member of that class of compounds which includes at least one fluorine atom in their structure, are being used in various industrial and consumer products due to their unique chemical properties. Perfluorooctanoic sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most important and well-known components among PFAS. Perfluoroalkyl and polyfluoroalkyl substances (PFAS) exert various kinds of effects on living organisms, but the most serious ones are the metabolic effects. However, PFAS are inert metabolically itself, but they interfere with endogenous metabolic pathways and reactions, and indirectly affect the metabolism of the body. Unluckily, there are many other PFAS to those humans are exposed throughout their life which not only imparts harmful effects on adults but also in whole life. It has been quantified that PFAS are present in amniotic fluid, fetal tissue, breastmilk, lung, heart, umbilical cord, and brain, blood, and placenta which indicates PFAS exposure in infants from the very start of life. PFAS exposure to Nematodes for 72 h shows the evidence of neuropathology during the inspection of GABAergic, dopaminergic, serotoninergic, and cholinergic neuronal morphologies. Ingestion of mycotoxins causes complex problems to human health. Physio-chemical processing aimed to destroy and mineralize contaminants into carbon dioxide and water or less toxic products.

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

Time-dependent effects of perfluorinated compounds on viability in cerebellar granule neurons: Dependence on carbon chain length and functional group attached

Even as states are responding to the coronavirus pandemic, their efforts to address per- and polyfluoroalkyl substances (PFAS) in the environment and in drinking water continue. As of this writing, seven states have taken specific steps in 2020 and eight states continue to follow through on ongoing initiatives. Most state activities are focused on setting drinking water standards, with California, Maine, Massachusetts, New Jersey, and Vermont all advancing primary drinking water standards. State legislative activity continues to target PFAS in drinking water as well. In Virginia, two laws were signed that mandate efforts to develop standards for PFAS, and many other states have seen similar bills introduced. While state efforts have emerged out of frustration that federal action requires time to assess the risks posed by PFAS before taking appropriate regulatory steps, the array of federal activities and work products has changed. A key tenet that AWWA shares with many other stakeholders is that neither the federal government nor states should rely solely on the Safe Drinking Water Act to address PFAS. Preventing PFAS from entering the water supply starts with making sound decisions about if, and how, to use PFAS. While the public spotlight has often focused on PFAS in drinking water, this is slowly changing. Since the publication of the US Environmental Protection Agency's (USEPA's) PFAS Action Plan, research programs have ramped up focus on PFAS. A major component of USEPA research is the characterization of toxicity, including an ongoing effort to conduct rapid screening toxicity research for 150 PFAS and risk assessments for seven specific PFAS. There is also ongoing work to develop analytical methods for natural waters, wastewaters, biosolids, soils, and other media, with a method suitable for monitoring wastewater now available for use. Core regulatory programs at USEPA have taken steps to address PFAS as well. USEPA's solid and hazardous waste program released interim cleanup recommendations for sites contaminated with perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) that are tied directly to the existing PFOA and PFOS health advisory levels. The agency also recently added 172 PFAS to the Toxics Release Inventory (TRI), according to the National Defense Authorization Act for Fiscal Year 2020, which will help characterize facilities releasing PFAS into the environment. USEPA also has recently promulgated a rule that imposes restrictions on the commerce of products containing certain PFAS. As these efforts have proceeded, USEPA has moved forward to address PFAS in drinking water. Not only has the USEPA Office of Water proposed to regulate PFOA and PFOS, it is expected to finalize the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) to gather occurrence data for 29 PFAS using new analytical methods by next summer. While there are considerable differences in the policy debate around PFAS, one constant is the need to make science-based decisions that provide meaningful public health protection. To that end, AWWA and many others expressed support for USEPA's positive regulatory determination for PFOA and PFOS and encouraged the agency to conduct a thorough and transparent evaluation of potential standards. Additionally, AWWA and others emphasized that the agency should not consider additional PFAS yet, given outstanding data gaps and forthcoming data collection activities that would directly address those gaps. Ongoing efforts include data collection programs such as the TRI, UCMR 5, and toxicity research. These programs are expected to facilitate evaluations for more meaningful future determinations for additional PFAS with substantially more data than what are currently available. Education and outreach by the entire water sector will continue to be critical to ensure that all state and federal authorities identify and manage PFAS use. We urge the drinking water community to continue to communicate with state and local decision makers about the need for protecting public health using sound standards. Chris Moody is the regulatory technical manager at the AWWA Government Affairs Office in Washington, D.C. He can be reached at cmoody@awwa.org.

Perfluoroalkyl and polyfluoroalkyl substances in the lower atmosphere and surface waters of the Chinese Bohai Sea, Yellow Sea, and Yangtze River estuary

Polyfluoroalkyl and perfluoroalkyl substances (PFAS) are persistent organic pollutants and exposure have been suggested with the risk of developing preeclampsia. Yet, evidence on the associations of PFAS with preeclampsia is still conflicting. Thus, the current study conducted a systematic review and meta-analysis of the epidemiological evidence linking maternal PFAS exposure to preeclampsia. This research methodology involved searching three electronic databases for epidemiological studies, and then conducting a meta-analysis using a random-effects model to analyse the heterogeneity between the studies. The quality and strength of evidence for each exposure-outcome pair was also evaluated, as well as the risk of bias. The search identified 10 potentially eligible studies related to maternal PFAS blood level with preeclampsia, which 7 were ultimately selected. Meta-analysis demonstrated evidence of association between combined PFAS compounds in pregnant mother with preeclampsia with zero heterogeneity (I2=0.0%, Q= 3.09, df= 6, p=0.798). Preeclampsia was found to have moderate association with maternal perfluorooctanoic acid (PFOA) exposure (Test for overall effect: z=2.2, p=0.03; Test for heterogeneity: I2=0.0%, Q= 3.49, df= 6, p=0.745) as well as maternal perfluorooctane sulfonate (PFOS) exposure (Test for overall effect: z=2.5, p=0.01; Test for heterogeneity: I2=0.0%, Q= 3.70, df= 6, p=0.718). This study showed significant associations between PFOA and PFOS exposure with the risk of preeclampsia. However, in-depth investigation is imperative to elucidate the impact of the different concentration and types of PFAS on preeclampsia risk.

First report of perfluoroalkyl acids (PFAAs) in the Indus Drainage System: Occurrence, source and environmental risk

Exposure to per and poly-fluoroalkyl substances (PFAS) is suggested to interfere with the central nervous system that may affect mental health. Studies on the relationships between exposure to PFAS mixtures and anxiety in humans are rare. This study aimed to evaluate the associations between single and combined exposure to PFAS and anxiety among adults. Data were extracted from the National Health and Nutrition Examination Survey (NHANES, 2007-2012). Six serum PFAS concentrations were accessed including perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), PFOS (perfluorooctanesulfonic acid), PFHxS (perfluorohexane sulfonate), PFDA (perfluorodecanoic acid), Me-PFOSA-AcOH (2-(N-methylperfluorooctanesulfonamide) acetic acid). The anxiety state was defined through the questionnaire responses of the participants. Weighted logistics regression was used to calculate their odds ratio (OR) and corresponding confidence interval (95% CI) that assessed the relationship between PFAS exposure and anxiety. Moreover, Two different statistical methods including quantile-based g-computation (Qgcomp), and Bayesian kernel machine regression (BKMR) were employed to investigate the overall effects of PFAS mixtures on anxiety. The effects of specific PFAS exposure on anxiety varied by sex. In male participants, one-unit increase in PFDA (OR = 0.62; 95%CI: 0.44, 0.88), PFOA (OR = 0.60; 95%CI: 0.41, 0.87), PFNA (OR = 0.68; 95%CI: 0.46, 0.96) concentrations were inversely linked to anxiety. In female participants, a one-unit increase in PFOA (OR = 1.50; 95%CI: 1.05, 2.14) concentration was associated with anxiety. Analysis of Qgcomp demonstrated that PFAS mixtures were negatively associated with anxiety in males (OR = 0.85; 95%CI: 0.74, 0.99), and were positively associated with anxiety in females(OR = 1.16; 95%CI: 1.01, 1.33). Analysis of BKMR suggested that PFAS mixtures were negatively associated with anxiety in the males, while its associations with anxiety were positive in the females. Although a growing number of studies have focused on the relationship between PFAS and anxiety, most have been performed based on animal observations rather than human populations, and the combined effects of PFAS mixtures on anxiety have not been evaluated. To address these gaps, this study first explored the associations between individual PFAS and PFAS mixture exposures and anxiety among US adults. Using data from the National Health and Nutrition Examination Survey, we demonstrated that co-exposure to a mixture of PFAS was negatively associated with anxiety in males, and its association was contrary in females.

Progress toward understanding the bioaccumulation of perfluorinated alkyl acids

Considering environmental exposures to per- and polyfluoroalkyl substances (PFAS) as risk factors for hypertensive disorders of pregnancy

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.

BackgroundThe specific mechanisms by which poly - and polyfluoroalkyl substances (PFAS) influence the particular lipid levels of adolescents and the progression of early subclinical atherosclerosis remain unclear. A certain degree of correlation exists between folate and the exposure of adolescents to PFAS, the maintenance of lipid homeostasis, as well as cardiovascular health status. This study investigated the role and mechanisms of folate in the process through which PFAS can influence the blood lipid profiles of adolescents.MethodsWe used data from the National Health and Nutrition Examination Survey 2005–2018. Weighted generalized linear regression analysis, Bayesian kernel machine regression, weighted quantile sum regression, mediation analysis, and network toxicology were employed to investigate the association between mixed exposures to perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate, and perfluorononanoic acid (PFNA) and lipids, as well as the atherogenic index of plasma (AIP), and to determine the impact of red blood cell folate or serum folate in the body.ResultsA positive association was detected between low density lipoprotein cholesterol (LDL-C) and PFOS; between total cholesterol (TC) and both PFOS and PFOA; between triglycerides (TG) and PFNA, PFOS, and PFOA; and between AIP and PFNA, PFOS, and PFOA. Analysis identified a positive correlation between mixed PFAS and LDL-C, TC, TG, and AIP. Red blood cell folate suppressed the associations of PFOA, PFOS, PFNA, and total PFAS with TG, as well as PFOA, PFOS, and total PFAS with AIP. The suppression effect of red blood cell folate was more pronounced in female adolescents. PFAS was associated with certain targets, including albumin, peroxisome proliferator-activated receptor γ, and interleukin-10, and may influence lipid metabolism and atherosclerosis. PFAS and folate share caspase-1 and carbonic anhydrase 2 as targets for mechanisms associated with atherosclerosis.ConclusionsPFAS exposure may be associated with dyslipidemia and impaired cardiovascular health in adolescents, while folate could potentially attenuate the direct association between PFAS exposure and these health outcomes. In the future, maintaining normal levels of folate in the body could be a key strategy in preventing disruptions to lipid metabolism and potential threats to cardiovascular health in adolescents caused by PFAS.

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants that have been used in many applications, including firefighting foams, stain repellents, nonstick coatings, and electroplating. Due to the extremely strong carbon-fluorine bonds in PFAS, they are highly stable and environmentally persistent. Because of their stability, PFAS can lead to bioaccumulation in humans and cause various health issues, including prostate and kidney cancer, thyroid disease, and cardiovascular disease. PFAS widely contaminate the river and lake water systems and hence cause contaminations in the drinking water. Analytical methods used for PFAS detection are currently dominated by chromatography in combination with mass spectrometry. U.S. EPA has established health advisory levels at 70 parts per trillion (70 ng/L) for PFOA and PFOS individually or combined in drinking water. Since this is a very low PFOA/PFOS concentration, preconcentrating the sample up to a detectable level plays a vital role and is an essential step during the analysis. Herein we present a novel preconcentration method for PFAS using electrogenerated shrinking gas bubbles, which can preconcentrate the PFOA and PFOS by 1300 folds within 15 minutes.Our preconcentration method is based on the natural phenomenon called sea-spray aerosol enrichment. Once air gets trapped inside a liquid column, and as these air bubbles start moving to the top through the liquid column, surface-active compounds can be preferentially adsorbed onto the air/liquid interface of the bubble. When these bubbles reach the air/liquid interface at the top of the liquid column, they burst and produce aerosol droplets enriched with surface-active compounds. Rather than using an external gas supply to generate bubbles, we in situ electrogenerated O2 and CO2 bubbles by water oxidation in the presence of 0.2 M ammonium bicarbonate as an electrolyte. The advantages of using anodically enriched bubbles bursting aerosol are 2-fold. The first one is in an ammonium bicarbonate electrolyte; the anodic side generates oxygen bubbles and carbon dioxide bubbles. Since carbon dioxide bubbles get shrunk, the effective surface area reduces. Hence the surface concentration of PFAS increases. With that high surface concentration of PFAS, the droplet's effective concentration becomes higher when it becomes aerosol droplets. The second one is when the electrolysis happens, the anode is charged positively. Due to the charge interactions, PFAS can pre-regulate near the electrode surface and provide additional preconcentration. We tested eight PFAS compounds, including perfluoroalkyl sulfonates and carboxylates. All the perfluoroalkyl carboxylate compounds show an average of 50% increase in the enrichment for the anodically enriched bubble aerosol than the cathodically enriched bubble aerosol. Furthermore, all the perfluoroalkyl sulfonate compounds show an average of 30% enrichment in the anodically enriched bubble aerosol than the cathodically enriched bubble aerosol. Due to its high contribution to environmental contamination, we used perfluorooctanoic acid (PFOA) as our model analyte. Enrichment ratios for different concentrations of PFOA ranging from 10-11 M to 10-7 M show an average of 1050 fold enrichment. To test our bubble shrinking theory, we measured the radius of the bubbles at different heights from the electrode surface. We observed an 87.5% volume reduction when the bubble moves a distance of 17.5 cm from the electrode surface to the air-water interface. We measured the enrichment ratio vs different heights to test the surface interaction between the PFAS molecules and the electrode surface. We obtained the intercept of 400 from the anodic compartment, while from the cathodic enrichment, we obtained the intercept of 200. The intercept (enrichment at zero height) involves two factors. The first one is a higher PFAS content at the air-water interface, which may cause enrichment at zero height. However, this factor is common for both compartments. However, the anodic side electrode is positively charged, and since PFAS are negatively charged, there can be a surface interaction and causing additional enrichment in the anodic side. Furthermore, our method is compatible with the LC/MS/MS method because ammonium bicarbonate is LC/MS/MS friendly solvent. Moreover, we successfully couple this technique with our previously published bubble nucleation-based electrochemical detection. This novel technique may lead to a path toward building a low-cost and fast onsite detection method for PFAS in water.

Human ingestion of per- and polyfluoroalkyl substances (PFAS) from contaminated food and water is linked to the development of several cancers, birth defects and other illnesses. The complete mineralisation of aqueous PFAS by ultrasound (sonolysis) into harmless inorganics has been demonstrated in many studies. However, the range and interconnected nature of reaction parameters (frequency, power, temperature etc.), and variety of reaction metrics used, limits understanding of degradation mechanisms and parametric trends. This work summarises the state-of-the-art for PFAS sonolysis, considering reaction mechanisms, kinetics, intermediates, products, rate limiting steps, reactant and product measurement techniques, and effects of co-contaminants. The meta-analysis showed that mid-high frequency (100 – 1,000 kHz) sonolysis mechanisms are similar, regardless of reaction conditions, while the low frequency (20 – 100 kHz) mechanisms are specific to oxidative species added, less well understood, and generally slower than mid-high frequency mechanisms. Arguments suggest that PFAS degradation occurs via adsorption (not absorption) at the bubble interface, followed by headgroup cleavage. Further mechanistic steps toward mineralisation remain to be proven. For the first time, complete stoichiometric reaction equations are derived for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) sonolysis, which add H2 as a reaction product and consider CO an intermediate. Fluorinated intermediate products are derived for common, and more novel PFAS, and a naming system proposed for novel perfluoroether carboxylates. The meta-analysis also revealed the transition between pseudo first and zero order PFOA/S kinetics commonly occurs at 15 – 40 µM. Optimum values of; ultrasonic frequency (300 – 500 kHz), concentration (>15 – 40 μM), temperature (≈20 °C), and pH range (3.2 – 4) for rapid PFOX degradation are derived by evaluation of prior works, while optimum values for the dilution factor applied to PFAS containing firefighting foams and applied power require further work. Rate limiting steps are debated and F− is shown to be rate enhancing, while SO42− and CO2 by products are theorised to be rate limiting. Sonolysis was compared to other PFAS destructive technologies and shown to be the only treatment which fully mineralises PFAS, degrades different PFAS in order of decreasing hydrophobicity, is parametrically well studied, and has low-moderate energy requirements (several kWh g−1 PFAS). It is concluded that sonolysis of PFAS in environmental samples would be well incorporated within a treatment train for improved efficiency.