Transport of ammonium perfluorooctanoate in environmental media near a fluoropolymer manufacturing facility

Effect of electrolyte composition on electrocatalytic transformation of perfluorooctanoic acid (PFOA) in high pH medium

Recent regulatory actions aim to limit per- and polyfluoroalkyl substances (PFAS) concentrations in drinking water and wastewaters. Regenerable anion exchange resin (AER) is an effective separation process to remove PFAS from water but will require PFAS post-treatment of the regeneration wastestream. Electrocatalytic (EC) processes using chemically boron-doped diamond electrodes, stable in a wide range of chemical compositions show potential to defluorinate PFOA in drinking water and wastewater treatments. Chemical composition and concentration of mineral salts in supporting electrolytes affect AER regeneration efficiency, and play a crucial role in the EC processes. Their impact on PFAS degradation remains understudied. This study investigates the impact of 17 brine electrolytes with different compositions on perfluorooctanoic acid (PFOA) degradation in an alkaline medium and explores the correlation between the rate of PFOA degradation and the solution's conductivity. Results show that higher electrolyte concentrations and conductivity lead to faster PFOA degradation rates. The presence of chloride anions have negligible impact on the degradation rate. However, the presence of nitrate salts reduce PFOA degradation efficiency. Additionally, the use of mixed electrolytes may be a promising approach for reducing the cost of EC operations. PFOA degradation was not influenced by the pH of the bulk solution.

All-cause, cardiovascular disease and cancer mortality in the population of a large Italian area contaminated by perfluoroalkyl and polyfluoroalkyl substances (1980-2018)

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are associated with many adverse health conditions. Among the main effects is carcinogenicity in humans, which deserves to be further clarified. An evident association has been reported for kidney cancer and testicular cancer. In 2013, a large episode of surface, ground and drinking water contamination with PFAS was uncovered in three provinces of the Veneto Region (northern Italy) involving 30 municipalities and a population of about 150,000. We report on the temporal evolution of all-cause mortality and selected cause-specific mortality by calendar period and birth cohort in the local population between 1980 and 2018.

METHODS

The Italian National Institute of Health pre-processed and made available anonymous data from the Italian National Institute of Statistics death certificate archives for residents of the provinces of Vicenza, Padua and Verona (males, n = 29,629; females, n = 29,518) who died between 1980 and 2018. Calendar period analysis was done by calculating standardised mortality ratios using the total population of the three provinces in the same calendar period as reference. The birth cohort analysis was performed using 20-84 years cumulative standardised mortality ratios. Exposure was defined as being resident in one of the 30 municipalities of the Red area, where the aqueduct supplying drinking water was fed by the contaminated groundwater.

RESULTS

During the 34 years between 1985 (assumed as beginning date of water contamination) and 2018 (last year of availability of cause-specific mortality data), in the resident population of the Red area we observed 51,621 deaths vs. 47,731 expected (age- and sex-SMR: 108; 90% CI: 107-109). We found evidence of raised mortality from cardiovascular disease (in particular, heart diseases and ischemic heart disease) and malignant neoplastic diseases, including kidney cancer and testicular cancer.

CONCLUSIONS

For the first time, an association of PFAS exposure with mortality from cardiovascular disease was formally demonstrated. The evidence regarding kidney cancer and testicular cancer is consistent with previously reported data.

PFAS remediation in soil: An evaluation of carbon-based materials for contaminant sequestration

The presence of per- and poly-fluoroalkyl substances (PFAS) in soils is a global concern as these emerging contaminants are highly resistant to degradation and cause adverse effects on human and environmental health at very low concentrations. Sequestering PFAS in soils using carbon-based materials is a low-cost and effective strategy to minimize pollutant bioavailability and exposure, and may offer potential long-term remediation of PFAS in the environment. This paper provides a comprehensive evaluation of current insights on sequestration of PFAS in soil using carbon-based sorbents. Hydrophobic effects originating from fluorinated carbon (C-F) backbone "tail" and electrostatic interactions deriving from functional groups on the molecules' "head" are the two driving forces governing PFAS sorption. Consequently, varying C-F chain lengths and polar functional groups significantly alter PFAS availability and leachability. Furthermore, matrix parameters such as soil organic matter, inorganic minerals, and pH significantly impact PFAS sequestration by sorbent amendments. Materials such as activated carbon, biochar, carbon nanotubes, and their composites are the primary C-based materials used for PFAS adsorption. Importantly, modifying the carbon structural and surface chemistry is essential for increasing the active sorption sites and for strengthening interactions with PFAS. This review evaluates current literature, identifies knowledge gaps in current remediation technologies and addresses future strategies on the sequestration of PFAS in contaminated soil using sustainable novel C-based sorbents.

Spatial distribution, isomer signature and air-soil exchange of legacy and emerging poly- and perfluoroalkyl substances

Widespread occurrences of various poly- and perfluoroalkyl substances (PFAS) in terrestrial environment calls for the growing interest in their transport behaviors. However, limited studies detected PFAS with structural diversity in tree barks, which reflect the long-term contamination in atmosphere and play a vital role in air-soil exchange behaviors. In this study, 26 PFAS congeners and typical branched isomers were investigated in surface soils and tree barks at 28 sites along the Taihu Lake, Taipu River, and Huangpu River. Concentrations of total PFAS in soils and tree barks were 0.991-29.4 and 7.99-188 ng/g dw, with PFPeA and PFDoA were the largest contributors in the two matrices. The highest PFAS levels were found in the Taihu Lake watershed, where textile manufacturing and metal plating activities highly prosper. With regard to the congener and isomer signatures, short-chain homologs dominated in soils (65.5%), whereas long-chain PFAS showed a major proportion in barks (41.9%). The composition of linear isomers of PFOS, PFOA and PFHxS implied that precursor degradation might be an important source of PFAS in addition to the 3M electrochemical fluorination (ECF). Additionally, the distance from the emission source, total organic carbon (TOC), logKOA and logKOW were considered potential influencing factors in PFAS distributions. Based on the multi-media fugacity model, about 71% of the fugacity fraction (ffs) values of the PFAS were below 0.3, indicating the dominant deposition from the atmosphere to the soil. The average fluxes of air-soil exchange for PFAS were -0.700 ± 11.0 ng/(m2·h). Notably, the estimated daily exposure to PFAS ranged from 9.57 × 10-2 to 8.59 × 10-1 ng/kg·bw/day for children and 3.31 × 10-2 to 3.09 × 10-1 ng/kg·bw/day for adults, suggesting low risks from outdoor inhalation and dermal uptake. Overall, results from distribution with structural diversity, air-soil exchange and preliminary risk assessment. This study provided in-depth insight of PFAS in multi-medium environment and bridged gaps between field data and policy-making for pollution control.

Efficient and fast remediation of soil contaminated by per- and polyfluoroalkyl substances (PFAS) by high-frequency heating

This study presents a novel thermal technology (high-frequency heating, HFH) for the decontamination of soil containing per- and polyfluoroalkyl substances (PFAS) and aqueous film-forming foams (AFFFs). Ultra-fast degradation of short-chain PFAS, long-chain homologs, precursors, legacy PFAS, emerging PFAS was achieved in a matter of minutes. The concentrations of PFAS and the soil type had a negligible impact on degradation efficiency, possibly due to the ultra-fast degradation rate overwhelming potential differences. Under the current HFH experiment setup, we achieved near-complete degradation (e.g., >99.9%) after 1 min for perfluoroalkyl carboxylic acids and perfluoroalkyl ether carboxylic acids and 2 min for perfluoroalkanesulfonic acids. Polyfluoroalkyl precursors in AFFFs were found to degrade completely within 1 min of HFH; no residual cationic, zwitterionic, anionic, or non-ionic intermediate products were detected following the treatment. The gaseous byproducts were considered. Most of gaseous organofluorine products of PFAS at low-and-moderate temperatures disappeared when temperatures reached 890 °C, which is in the temperature zone of HFH. For the first time, we demonstrated minimal loss of PFAS in water during the boiling process, indicating a low risk of PFAS entering the atmosphere with the water vapor. The findings highlight HFH its potential as a promising remediation tool for PFAS-contaminated soils.

The Latest Sensor Detection Methods for per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFASs) have emerged as a prominent environmental pollutant in recent years, primarily due to their tendency to accumulate and magnify in both the environment and living organisms. The entry of PFASs into the environment can have detrimental effects on human health. Hence, it is crucial to actively monitor and detect the presence of PFASs. The current standard detection method of PFAS is the combination of chromatography and mass spectrometry. However, this requires expensive instruments, extra sample pretreatment steps, complicated operation and long analysis time. As a result, new methods that do not rely on chromatography and mass spectrometry have been developed and applied. These alternative methods mainly include optical and electrochemical sensor methods, which offer great potential in terms of real-time field detection, instrument miniaturization, shorter analysis time, and reduced detection cost. This review provides a summary of recent advancements in PFAS detection sensors. We categorize and explain the principles and mechanisms of these sensors, and compare their limits of detection and sensitivity. Finally, we discuss the future challenges and improvements needed for PFAS sensors, such as field application, commercialization, and other related issues.

Beyond Conventional Density Functional Theory: Advanced Quantum Dynamical Methods for Understanding Degradation of Per- and Polyfluoroalkyl Substances

Computational chemistry methods, such as density functional theory (DFT), have now become more common in environmental research, particularly for simulating the degradation of per- and polyfluoroalkyl substances (PFAS). However, the vast majority of PFAS computational studies have focused on conventional DFT approaches that only probe static, time-independent properties of PFAS near stationary points on the potential energy surface. To demonstrate the rich mechanistic information that can be obtained from time-dependent quantum dynamics calculations, we highlight recent studies using these advanced techniques for probing PFAS systems. We briefly discuss recent applications ranging from ab initio molecular dynamics to DFT-based metadynamics and real-time time-dependent DFT for probing PFAS degradation in various reactive environments. These quantum dynamical approaches provide critical mechanistic information that cannot be gleaned from conventional DFT calculations. We conclude with a perspective of promising research directions and recommend that these advanced quantum dynamics simulations be more widely used by the environmental research community to directly probe PFAS degradation dynamics and other environmental processes.

Emerging Contaminants: An Emerging Risk Factor for Diabetes Mellitus

Emerging contaminants have been increasingly recognized as critical determinants in global public health outcomes. However, the intricate relationship between these contaminants and glucose metabolism remains to be fully elucidated. The paucity of comprehensive clinical data, coupled with the need for in-depth mechanistic investigations, underscores the urgency to decipher the precise molecular and cellular pathways through which these contaminants potentially mediate the initiation and progression of diabetes mellitus. A profound understanding of the epidemiological impact of these emerging contaminants, as well as the elucidation of the underlying mechanistic pathways, is indispensable for the formulation of evidence-based policy and preventive interventions. This review systematically aggregates contemporary findings from epidemiological investigations and delves into the mechanistic correlates that tether exposure to emerging contaminants, including endocrine disruptors, perfluorinated compounds, microplastics, and antibiotics, to glycemic dysregulation. A nuanced exploration is undertaken focusing on potential dietary sources and the consequential role of the gut microbiome in their toxic effects. This review endeavors to provide a foundational reference for future investigations into the complex interplay between emerging contaminants and diabetes mellitus.

Predictions of PFAS regional-scale atmospheric deposition and ambient air exposure

Per- and polyfluoroalkyl substances (PFAS) are a large class of human-made compounds that have contaminated the global environment. One environmental entry point for PFAS is via atmospheric emission. Air releases can impact human health through multiple routes, including direct inhalation and contamination of drinking water following air deposition. In this work, we convert the reference dose (RfD) underlying the United States Environmental Protection Agency's GenX drinking water Health Advisory to an inhalation screening level and compare to predicted PFAS and GenX air concentrations from a fluorochemical manufacturing facility in Eastern North Carolina. We find that the area around the facility experiences ~15 days per year of GenX concentrations above the inhalation screening level we derive. We investigate the sensitivity of model predictions to assumptions regarding model spatial resolution, emissions temporal profiles, and knowledge of air emission chemical composition. Decreasing the chemical specificity of PFAS emissions has the largest impact on deposition predictions with domain-wide total deposition varying by as much as 250 % for total PFAS. However, predicted domain-wide mean and median air concentrations varied by <18 % over all scenarios tested for total PFAS. Other model features like emission temporal variability and model spatial resolution had weaker impacts on predicted PFAS deposition.

Evidence of large-scale deposition of airborne emissions of per- and polyfluoroalkyl substances (PFASs) near a fluoropolymer production plant in an urban area

Airborne emissions of per- and polyfluoroalkyl substances (PFASs) from fluoropolymer manufacturing facilities-especially those producing polyvinylidene (PVDF)-have rarely been investigated. Once PFASs are released into the air from the facility stacks, they settle in the surrounding environment, contaminating all surfaces. Human beings living in close proximity to these facilities can be exposed through air inhalation and ingestion of contaminated vegetables, drinking water or dust. In this study, we collected nine surface soil and five outdoor settled dust samples within 200 m of the fence line of a PVDF and fluoroelastomer production site near Lyon (France). Samples were collected in an urban area including a sports field. High concentrations of long-chain perfluoroalkyl carboxylic acids (PFCAs) (C ≥ 9) were found at sampling points downwind of the facility. Perfluoroundecanoic acid (PFUnDA) was the predominant PFAS in surface soil (12-245 ng/g dw), whereas perfluorotridecanoic acid (PFTrDA) was in outdoor dust (<0.5-59 ng/g dw). The PFAS profiles observed in soil and dust samples very likely originate from the processing aids used for PVDF and fluoroelastomer production. To our knowledge, long-chain PFCA concentrations as high as reported herein have never been found outside the perimeter fencing of a fluoropolymer plant. PFAS concentrations in other environmental compartments (such as air, vegetables or groundwater) should be monitored to assess all potential pathways to exposure of nearby residents before carrying out human biomonitoring.

Perfluorinated compound correlation between human serum and drinking water: Is drinking water a significant contributor?

Perfluorinated compounds (PFASs) are a new artificial chemical. Due to its substantial toxicity and complex degradation in the natural environment, monitoring PFASs has become a hot issue for many researchers. Currently, the relationship between the concentration of PFASs in serum and the concentration of PFASs in drinking water is unclear. This paper aims to study the concentration levels of PFASs in drinking water and residents' serum in a city in northern China and the relationship between them. The results show that the concentration of PFASs in drinking water is low, and the average concentrations of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) were 2.57 ± 0.69 ng/L and 0.30 ng/L, respectively, which were lower than the limits specified in China's newly introduced Standards for drinking water quality (GB 5749-2022). In the serum of residents, PFOA and PFOS were the two PFASs with the highest concentration. Spearman correlation analysis showed that perfluorohexane sulfonate (PFHxS) and PFOS concentrations were positively correlated with age, and PFHxS, PFOA, PFNA, and PFOS varied with sex. At the same time, the correlation analysis also showed no correlation between PFAS in drinking water and serum, indicating that drinking water was not the main factor causing the physical burden of PFAS in residents. The HI method was used to assess the health risks of PFASs to human beings. The risk entropy of all PFASs for human hepatotoxicity and reproductive toxicity is below 1.

Tubing material considerably affects measurement delays of gas-phase oxygenated per- and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants associated with negative health impacts. Assessments of tubing-related measurement bias for volatile PFAS are lacking, as gas-wall interactions with tubing can delay quantification of gas-phase analytes. We use online iodide chemical ionization mass spectrometry measurements to characterize tubing delays for three gas-phase oxygenated PFAS - 4:2 fluorotelomer alcohol (4:2 FTOH), perfluorobutanoic acid (PFBA), and hexafluoropropylene oxide dimer acid (HFPO-DA). Perfluoroalkoxy alkane and high-density polyethylene tubing yielded relatively short absorptive measurement delays, with no clear dependence on tubing temperature or sampled humidity. Sampling through stainless steel tubing led to prolonged measurement delays due to reversible adsorption of PFAS to the tubing surface, with strong dependence on tubing temperature and sample humidification. Silcosteel tubing afforded shorter measurement delays than stainless steel due to diminished surface adsorption of PFAS. Characterizing and mitigating these tubing delays is crucial for reliable quantification of airborne PFAS.Implications: Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants. Many PFAS are sufficiently volatile to exist as airborne pollutants. Measurements and quantification of airborne PFAS can be biased from material-dependent gas-wall interactions with sampling inlet tubing. Thus, characterizing these gas-wall interactions are crucial for reliably investigating emissions, environmental transport, and fates of airborne PFAS.

Per- and polyfluoroalkyl substances (PFAS) exposure through munitions in the Russia-Ukraine conflict

Considered contaminants of emerging concern, per- and polyfluoroalkyl substances (PFAS) are a class of toxic, manufactured chemicals found in commercial and consumer products such as nonstick cookware, food packaging, and firefighting foams. Human exposure to PFAS through inhalation and ingestion can cause a variety of harmful effects and negative health outcomes. Per- and polyfluoroalkyl substances possess high polarity and chemical stability, enabling them to resist degradation in most environmental conditions. These characteristics allow PFAS to be mobile in soil, air, and water, and bioaccumulate in living organisms. Due to their thermally resistant chemical properties, PFAS are used as binders in polymer-bonded explosives (PBX) and in various components of munitions. Thus, when munitions are detonated, PFAS are released into the environment as aerosols and can deposit in the soil, surface water, or biota. Air emission modeling suggests that ground-level and airborne detonation of munitions can increase PFAS deposition both locally and long range. Further, if industrial facilities with PFAS are damaged or destroyed, there is greater potential for environmental degradation from increased release of PFAS into the environment. As a consequence of their persistent nature, PFAS can remain in an environment long after armed conflict, indirectly affecting ecosystems, food sources, and human health. The toxic contamination from munitions could present a greater hazard to a larger population over time than acute detonation events. This article discusses methods for estimating war-related damage from PFAS by exploring predictive modeling approaches and postwar ground validation techniques. Integr Environ Assess Manag 2023;19:376-381. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Perfluorooctanoic acid (PFOA) exposure in relation to the kidneys: A review of current available literature

Perfluorooctanoic acid is an artificial and non-degradable chemical. It is widely used due to its stable nature. It can enter the human body through food, drinking water, inhalation of household dust and contact with products containing perfluorooctanoic acid. It accumulates in the human body, causing potential harmful effects on human health. Based on the biodegradability and bioaccumulation of perfluorooctanoic acid in the human body, there are increasing concerns about the adverse effects of perfluorooctanoic acid exposure on kidneys. Research shows that kidney is the main accumulation organ of Perfluorooctanoic acid, and Perfluorooctanoic acid can cause nephrotoxicity and produce adverse effects on kidney function, but the exact mechanism is still unknown. In this review, we summarize the relationship between Perfluorooctanoic acid exposure and kidney health, evaluate risks more clearly, and provide a theoretical basis for subsequent research.

Photodegradation of per- and polyfluoroalkyl substances in water: A review of fundamentals and applications

Per- and polyfluoroalkyl substances (PFAS) are persistent, mobile, and toxic chemicals that are hazardous to human health and the environment. Several countries, including the United States, plan to set an enforceable maximum contamination level for certain PFAS compounds in drinking water sources. Among the available treatment options, photocatalytic treatment is promising for PFAS degradation and mineralization in the aqueous solution. In this review, recent advances in the abatement of PFAS from water using photo-oxidation and photo-reduction are systematically reviewed. Degradation mechanisms of PFAS by photo-oxidation involving the holes (h_vb⁺) and oxidative radicals and photo-reduction using the electrons (e_cb^-) and hydrated electrons (e_aq^-) are integrated. The recent development of innovative heterogeneous photocatalysts and photolysis systems for enhanced degradation of PFAS is highlighted. Photodegradation mechanisms of alternative compounds, such as hexafluoropropylene oxide dimer acid (GenX) and chlorinated polyfluorinated ether sulfonate (F-53B), are also critically evaluated. This paper concludes by identifying major knowledge gaps and some of the challenges that lie ahead in the scalability and adaptability issues of photocatalysis for natural water treatment. Development made in photocatalysts design and system optimization forges a path toward sustainable treatment of PFAS-contaminated water through photodegradation technologies.

Phytoremediation prospects of per- and polyfluoroalkyl substances: A review

Extensive use of per- and polyfluoroalkyl substances (PFASs) in various industrial activities and daily-life products has made them ubiquitous contaminants in soil and water. PFAS-contaminated soil acts as a long-term source of pollution to the adjacent surface water bodies, groundwater, soil microorganisms, and soil invertebrates. While several remediation strategies exist to eliminate PFASs from the soil, strong ionic interactions between charged groups on PFAS with soil constituents rendered these PFAS remediation technologies ineffective. Pilot and field-scale data from recent studies have shown a great potential of PFAS to bio-accumulate and distribute within plant compartments suggesting that phytoremediation could be a potential remediation technology to clean up PFAS contaminated soils. Even though several studies have been performed on the uptake and translocation of PFAS by different plant species, most of these studies are limited to agricultural crops and fruit species. In this review, the role of both aquatic and terrestrial plants in the phytoremediation of PFAS was discussed highlighting different mechanisms underlying the uptake of PFASs in the soil-plant and water-plant systems. This review further summarized a wide range of factors that influence the bioaccumulation and translocation of PFASs within plant compartments including both structural properties of PFASs and physiological properties of plant species. Even though phytoremediation appears to be a promising remediation technique, some limitations that reduced the feasibility of phytoremediation in the practical application have been emphasized in previous studies. Additional research directions are suggested, including advanced genetic engineering techniques and endophyte-assisted phytoremediation to upgrade the phytoremediation potential of plants for the successful removal of PFASs.

PFAS concentrations in soil versus soil porewater: Mass distributions and the impact of adsorption at air-water interfaces

Determining the risk posed by PFAS leaching from soil to groundwater requires quantification of the magnitude and temporal/spatial variability of PFAS mass discharge from the vadose zone, which is governed in part by the concentrations of PFAS in soil porewater. Porewater concentrations are impacted and mediated by the properties of the PFAS and soil, multiple transport and fate processes, and site conditions. The objective of this research was to delineate the relationship between soil porewater concentrations and soil concentrations, based on a comprehensive model of PFAS mass distribution within a soil sample volume. Measured parameters representing solid-phase sorption and air-water interfacial adsorption are used to illustrate the impact of soil and PFAS properties on the distribution of representative PFAS between soil and soil porewater. Literature data reported for soil and soil porewater concentrations of several PFAS obtained from outdoor lysimeter experiments are used to test the distribution model. Soil-to-porewater concentration ratios predicted with the model compared very well to the measured concentration ratios. The nondimensional distribution coefficient that describes the distribution of PFAS mass amongst all domains within a soil sample was observed to be a function of PFAS molecular size. Numerical simulations conducted for a model fire-training source area were used to illustrate the ranges in magnitude of soil versus porewater concentrations for representative field conditions. The results of the measured and simulated data sets demonstrated the importance of air-water interfacial adsorption for the distribution of the longer-chain PFAS within soil samples. PFAS soil porewater concentrations are anticipated to range from ng/L to mg/L depending upon soil concentrations, which in turn depend upon the nature of the site.

A review of recent studies on toxicity, sequestration, and degradation of per- and polyfluoroalkyl substances (PFAS)

The fate, effects, and treatment of per- and polyfluoroalkyl substances (PFAS), an anthropogenic class of chemicals used in industrial and commercial production, are topics of great interest in recent research and news cycles. This interest stems from the ubiquity of PFAS in the global environment as well as their significant toxicological effects in humans and wildlife. Research on toxicity, sequestration, removal, and degradation of PFAS has grown rapidly, leading to a flood of valuable knowledge that can get swamped out in the perpetual rise in the number of publications. Selected papers from the Journal of Hazardous Materials between January 2018 and May 2022 on the toxicity, sequestration, and degradation of PFAS are reviewed in this article and made available as open-access publications for one year, in order to facilitate the distribution of critical knowledge surrounding PFAS. This review discusses routes of toxicity as observed in mammalian and cellular models, and the observed human health effects in exposed communities. Studies that evaluate of toxicity through in-silico approaches are highlighted in this paper. Removal of PFAS through modified carbon sorbents, nanoparticles, and anion exchange materials are discussed while comparing treatment efficiencies for different classes of PFAS. Finally, various biotic and abiotic degradation techniques, and the pathways and mechanisms involved are reviewed to provide a better understanding on the removal efficiencies and cost effectiveness of existing treatment strategies.

Spatial distribution and load of per- and polyfluoroalkyl substances (PFAS) in background soils in Sweden

Per- and polyfluoroalkyl substances (PFAS) are known to be persistent, bioaccumulative, and have adverse health effects, but very little is known about PFAS in the terrestrial environment and factors influencing their distribution. This paper presents one of the first comprehensive studies investigating PFAS (n = 28) in background forest soils (n = 27) on national scale across Sweden. The results showed that 16 of 28 target PFAS were present and all sites contained at least three PFAS compounds, with total concentrations ranging between 0.40 ng/g dry weight (dw) and 6.6 ng/g dw. Perfluorooctanesulfonic acid (PFOS) showed the highest detection frequency of 89% and a median concentration of 0.39 ng/g dw. The PFOS loads (ng/m³) showed a distinct spatial distribution, with a significant exponential increase from north to south (R² = 0.55; p < 0.001) and west to east (R² = 0.35; p < 0.01). In some parts of Sweden, the compound 6:2 fluorotelomer sulfonate (6:2 FTSA) had a higher median concentration (1.4 ng/g dw), but was in comparison to PFOS more impacted by local sources. Partial least squares discriminant analysis (PLS-DA) showed regional clustering of PFAS compositional profiles, indicating that PFAS soil background concentrations are functions of spatial variations at local, regional, and countrywide scale. Such spatial trends have not been observed previously and it could not be deduced whether they are indicative of trends on a global scale, or country-specific and better explained by proximity to densely populated urban areas. An interpolation and extrapolation raster map created from the results was used to calculate the average total PFAS load on Swedish soils. Estimated total load in the top 10-cm soil layer was 2.7 ± 2.4 tons for PFOS and 16 ± 14 tons for ∑PFAS, indicating that soil carries a considerable legacy of past PFAS release.

Utilizing Pine Needles to Temporally and Spatially Profile Per- and Polyfluoroalkyl Substances (PFAS)

As concerns over exposure to per- and polyfluoroalkyl substances (PFAS) are continually increasing, novel methods to monitor their presence and modifications are greatly needed, as some have known toxic and bioaccumulative characteristics while most have unknown effects. This task however is not simple, as the Environmental Protection Agency (EPA) CompTox PFAS list contains more than 9000 substances as of September 2020 with additional substances added continually. Nontargeted analyses are therefore crucial to investigating the presence of this immense list of possible PFAS. Here, we utilized archived and field-sampled pine needles as widely available passive samplers and a novel nontargeted, multidimensional analytical method coupling liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) to evaluate the temporal and spatial presence of numerous PFAS. Over 70 PFAS were detected in the pine needles from this study, including both traditionally monitored legacy perfluoroalkyl acids (PFAAs) and their emerging replacements such as chlorinated derivatives, ultrashort chain PFAAs, perfluoroalkyl ether acids including hexafluoropropylene oxide dimer acid (HFPO-DA, "GenX") and Nafion byproduct 2, and a cyclic perfluorooctanesulfonic acid (PFOS) analog. Results from this study provide critical insight related to PFAS transport, contamination, and reduction efforts over the past six decades.

Coupled photocatalytic alkaline media as a destructive technology for per- and polyfluoroalkyl substances in aqueous film-forming foam impacted stormwater

The release of aqueous film forming foam (AFFF) from fuel fire events, fire training events, and other activities has resulted in the presence of persistent and recalcitrant per- and polyfluoroalkyl substances (PFAS) in soil and water nationwide. This study describes the degradation and defluorination of PFAS in stormwater collected from an AFFF-impacted site. Silica-based granular media (SGM) containing titanium dioxide was packed into a column reactor and placed between ultraviolet (UV) lamps to excite the photocatalyst within the SGM and generate free radicals to degrade PFAS present in water that was passed through the media. The system was amended with nucleophiles (hydroxyls) to facilitate the destruction of PFAS. Results showed rapid degradation of 17 identified PFAS, including perfluoroalkyl acid (PFAA) precursors, perfluorosulfonic acids (PFSAs), and perfluorocarboxylic acids (PFCAs). Significant defluorination was observed, indicating PFAS destruction as a result of the coupled photocatalytic and nucleophilic attack. Column reactor experiment findings indicate SGM in the presence of UV light passively degraded a mixture of PFAS in a concentrated waste stream at ambient conditions.

Perfluoroalkyl and Polyfluoroalkyl Substances in Groundwater Used as a Source of Drinking Water in the Eastern United States

In 2019, 254 samples were collected from five aquifer systems to evaluate perfluoroalkyl and polyfluoroalkyl substance (PFAS) occurrence in groundwater used as a source of drinking water in the eastern United States. The samples were analyzed for 24 PFAS, major ions, nutrients, trace elements, dissolved organic carbon (DOC), volatile organic compounds (VOCs), pharmaceuticals, and tritium. Fourteen of the 24 PFAS were detected in groundwater, with 60 and 20% of public-supply and domestic wells, respectively, containing at least one PFAS detection. Concentrations of tritium, chloride, sulfate, DOC, and manganese + iron; percent urban land use within 500 m of the wells; and VOC and pharmaceutical detection frequencies were significantly higher in samples containing PFAS detections than in samples with no detections. Boosted regression tree models that consider 57 chemical and land-use variables show that tritium concentration, distance to the nearest fire-training area, percentage of urban land use, and DOC and VOC concentrations are the top five predictors of PFAS detections, consistent with the hydrologic position, geochemistry, and land use being important controls on PFAS occurrence in groundwater. Model results indicate that it may be possible to predict PFAS detections in groundwater using existing data sources.

Experimental insights into anodic oxidation of hexafluoropropylene oxide dimer acid (GenX) on boron-doped diamond anodes

GenX is the trade name of the ammonium salt of hexafluoropropylene oxide dimer acid (HFPO-DA) and is used as a replacement for the banned perfluorooctanoic acid (PFOA). However, recent studies have found GenX to be more toxic than PFOA. This work deals with the electrochemical degradation of HFPO-DA using boron-doped diamond anodes. For the first time, an experimental study was conducted to investigate the influence of sulfate concentration and other operating parameters on HFPO-DA degradation. Results demonstrated that sulfate radicals were ineffective in HFPO-DA degradation due to steric hindrance by -CF₃ branch. Direct electron transfer was found as the rate-determining step. By comparing degradation of HFPO-DA with that of PFOA, it was observed that the steric hindrance by -CF₃ branch in HFPO-DA decreased the rate of electron transfer from the carboxyl head group even though its defluorination rate was faster. Conclusively, a degradation pathway is proposed in which HFPO-DA mineralizes to CO₂ and F- via formation of three intermediates.

Environmental Sources, Chemistry, Fate, and Transport of Per- and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting

A Society of Environmental Toxicology and Chemistry (SETAC) Focused Topic Meeting (FTM) on the environmental management of per- and polyfluoroalkyl substances (PFAS) convened during August 2019 in Durham, North Carolina (USA). Experts from around the globe were brought together to critically evaluate new and emerging information on PFAS including chemistry, fate, transport, exposure, and toxicity. After plenary presentations, breakout groups were established and tasked to identify and adjudicate via panel discussions overarching conclusions and relevant data gaps. The present review is one in a series and summarizes outcomes of presentations and breakout discussions related to (1) primary sources and pathways in the environment, (2) sorption and transport in porous media, (3) precursor transformation, (4) practical approaches to the assessment of source zones, (5) standard and novel analytical methods with implications for environmental forensics and site management, and (6) classification and grouping from multiple perspectives. Outcomes illustrate that PFAS classification will continue to be a challenge, and additional pressing needs include increased availability of analytical standards and methods for assessment of PFAS and fate and transport, including precursor transformation. Although the state of the science is sufficient to support a degree of site-specific and flexible risk management, effective source prioritization tools, predictive fate and transport models, and improved and standardized analytical methods are needed to guide broader policies and best management practices. Environ Toxicol Chem 2021;40:3234-3260. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

An electrocoagulation and electrooxidation treatment train to remove and degrade per- and polyfluoroalkyl substances in aqueous solution

This study examined the feasibility of a novel treatment train that combines electrocoagulation (EC) with electrooxidation (EO) treatment to remove and degrade per- and polyfluoroalkyl substances (PFASs) from water. Electrocoagulation with a zinc anode could effectively remove PFASs from water, and long-chain PFASs (C₇-C₁₀) tended to have a higher removal rate. Foam was generated when a relatively high current density (>1 mA cm^-2) was applied to a relatively high PFAS concentration (each PFAS > 0.1 μM) during EC, which promoted the separation of PFASs from the bulk solution, especially for long-chain PFASs. Isotherm-like adsorption results indicated that competitive adsorption on floc occurred between PFASs when no foam was produced in a solution containing 10 different PFASs. Acid dissolution methods could recover and concentrate 10 PFASs in controlled volumes from both the floc and the foam, and it was also successfully applied in groundwater collected from a contaminated site. The concentrated PFASs in the acid solutions were efficiently destructed using EO treatment with a Ti₄O₇ anode at 10 mA cm^-2, and no supplement of electrolyte was needed for the floc dissolved solution. This electrochemical-based process can economically separate, concentrate and destroy PFASs in groundwater and wastewater.

Exposure assessment of PFAS-contaminated sites using avian eggs as a biomonitoring tool: A frame of reference and a case study in the Po River valley (Northern Italy)

For many years, eggs of diverse bird species have been used as monitoring tools in studies investigating perfluoroalkyl substances (PFAS) contamination, especially in marine and remote areas. Avian eggs are a suitable monitoring matrix because they are relatively easy to collect and their yolks store diverse maternally transferred PFAS. Moreover, the concentrations of PFAS detected in the eggs are a good proxy for maternal exposure and allow the assessment of the potential risk for birds. These features support the use of avian eggs as a key monitoring tool in exposure assessment of PFAS-contaminated sites. We first review the recent application of avian eggs in PFAS monitoring in environmental risk assessment schemes, highlighting strengths and limitations and suggesting which criteria should be considered when selecting a proper study species and structuring the sampling and analytical protocol. Eventually, we report findings from a field study realized in 2020 near a perfluoropolymer factory site in the upper Po plain (Northern Italy), revealing an unprecedented contamination level of PFOA and C6O4 in three species of wild passerines. In future, long-term monitoring of PFAS contamination using avian eggs should be maintained, to provide crucial information on the temporal trend of fluorochemical production and waste disposal, while facilitating early identification of emerging PFAS as well as the quantification of their biomagnification across the trophic web. Integr Environ Assess Manag 2021;17:733-745. © 2021 SETAC.

Predicting the risk of GenX contamination in private well water using a machine-learned Bayesian network model

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants that pose significant challenges in mechanistic fate and transport modeling due to their diverse and complex chemical characteristics. Machine learning provides a novel approach for predicting the spatial distribution of PFAS in the environment. We used spatial location information to link PFAS measurements from 1207 private drinking water wells around a fluorochemical manufacturing facility to a mechanistic model of PFAS air deposition and to publicly available data on soil, land use, topography, weather, and proximity to multiple PFAS sources. We used the resulting linked data set to train a Bayesian network model to predict the risk that GenX, a member of the PFAS class, would exceed a state provisional health goal (140 ng/L) in private well water. The model had high accuracy (ROC curve index for five-fold cross-validation of 0.85, 90% CI 0.84-0.87). Among factors significantly associated with GenX risk in private wells, the most important was the historic rate of atmospheric deposition of GenX from the fluorochemical manufacturing facility. The model output was used to generate spatial risk predictions for the study area to aid in risk assessment, environmental investigations, and targeted public health interventions.

Environmental Source Tracking of Per- and Polyfluoroalkyl Substances within a Forensic Context: Current and Future Techniques

The source tracking of per- and polyfluoroalkyl substances (PFASs) is a new and increasingly necessary subfield within environmental forensics. We define PFAS source tracking as the accurate characterization and differentiation of multiple sources contributing to PFAS contamination in the environment. PFAS source tracking should employ analytical measurements, multivariate analyses, and an understanding of PFAS fate and transport within the framework of a conceptual site model. Converging lines of evidence used to differentiate PFAS sources include: identification of PFASs strongly associated with unique sources; the ratios of PFAS homologues, classes, and isomers at a contaminated site; and a site's hydrogeochemical conditions. As the field of PFAS source tracking progresses, the development of new PFAS analytical standards and the wider availability of high-resolution mass spectral data will enhance currently available analytical capabilities. In addition, multivariate computational tools, including unsupervised (i.e., exploratory) and supervised (i.e., predictive) machine learning techniques, may lead to novel insights that define a targeted list of PFASs that will be useful for environmental PFAS source tracking. In this Perspective, we identify the current tools available and principal developments necessary to enable greater confidence in environmental source tracking to identify and apportion PFAS sources.

Exposure to perfluorooctanesulfonate (PFOS) but not perflurorooctanoic acid (PFOA) at ppb concentration induces chronic toxicity in Daphnia carinata

Widespread environmental contamination of per- and polyfluoroalkyl substances (PFAS) is well established. Nevertheless, few studies have reported on the aquatic toxicity of PFAS, especially in indicator species such as Daphnia. In this study, the toxicity of two major PFAS, namely perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), was investigated on water flea (Daphnia carinata) using a battery of comprehensive toxicity tests, including a 48 h acute and a 21-day chronic assays. The survival, growth, and reproduction of D. carinata were monitored over a 21-day life cycle. PFOS exhibited higher toxicity than PFOA. The 48 h LC₅₀ values (confidence interval) based on acute toxicity for PFOA and PFOS were 78.2 (54.9-105) mg L^-1 and 8.8 (6.4-11.6) mg L^-1, respectively. Chronic exposure to PFOS for 21 days displayed mortality and reproductive defects in D. carinata at a concentration as low as 0.001 mg L^-1. Genotoxicity assessment using comet assay revealed that exposure for 96 h to PFOS at 1 and 10.0 mg L^-1 significantly damaged the organism's genetic makeup. The results of this study have great implications for risk assessment of PFOS and PFOA in aquatic ecosystems, given the potential of PFOS to pose a risk to Daphnia even at lower concentrations (1 μg L^-1).

Per- and Polyfluoroalkyl Substance (PFAS) Transport from Groundwater to Streams near a PFAS Manufacturing Facility in North Carolina, USA

We quantified per- and polyfluoroalkyl substance (PFAS) transport from groundwater to five tributaries of the Cape Fear River near a PFAS manufacturing facility in North Carolina (USA). Hydrologic and PFAS data were coupled to quantify PFAS fluxes from groundwater to the tributaries. Up to 29 PFAS were analyzed, including perfluoroalkyl acids and recently identified fluoroethers. Total quantified PFAS (ΣPFAS) in groundwater was 20-4773 ng/L (mean = 1863 ng/L); the range for stream water was 426-3617 ng/L (mean = 1717 ng/L). Eight PFAS constituted 98% of ΣPFAS; perfluoro-2-(perfluoromethoxy)propanoic acid (PMPA) and hexafluoropropylene oxide dimer acid (GenX) accounted for 61%. For PFAS discharge from groundwater to one tributary, values estimated from stream water measurements (18 ± 4 kg/yr) were similar to those from groundwater measurements in streambeds (22-25 ± 5 kg/yr). At baseflow, 32 ± 7 kg/yr of PFAS discharged from groundwater to the five tributaries, eventually reaching the Cape Fear River. Given the PFAS emission timeline at the site, groundwater data suggest the abundant fluoroethers moved through the subsurface to streams in ≪50 yr. Discharge of contaminated groundwater may lead to long-term contamination of surface water and impacts on downstream drinking water supplies. This work addresses a gap in the PFAS literature: quantifying PFAS mass transfer between groundwater and surface water using field data.

Mechanochemical remediation of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) amended sand and aqueous film-forming foam (AFFF) impacted soil by planetary ball milling

Per- and polyfluoroalkyl substances (PFAS) are manmade, fluorinated organic chemicals which have been identified as persistent organic pollutants. PFAS have surface active properties that have made them suitable for applications in oil- and water-resistant products, as well as many firefighting foams. No on-site remediation strategies exist to treat PFAS impacted soils. Mechanochemical remediation of PFOS- and PFOA-amended sand via a planetary ball mill was studied. The effect of sand mass, KOH as a co-milling reagent, and water saturation on the degradation of PFOA and PFOS was evaluated. By 4 h of milling concentrations were reduced by up to 98% for PFOS-amended dry sand and 99% for PFOA-amended dry sand without the addition of a co-milling reagent. Water saturation was determined to be a significant hindrance on the mechanochemical destruction of PFOS and PFOA. A maximum of 89% of fluoride was recovered from PFOS-amended sand when KOH was used as a co-milling reagent. It is hypothesized that reactive particles generated from the fracture of sand grains react with PFAS molecules to initiate destruction, which can result in full defluorination. Milling experiments were also conducted on soils from a Canadian firefighting training area (FFTA), demonstrating that PFOS concentrations can be reduced by up to 96% in site soils. For the first time, ball milling for the remediation of PFAS in environmental media has been demonstrated using amended sand and legacy soils from a FFTA.

An evaluation of health-based federal and state PFOA drinking water guidelines in the United States

Perfluorooctanoic acid (PFOA) is a synthetic, perfluorinated organic acid previously used in fluoropolymer production in the United States. PFOA has been a recent focal point for regulation because of its ubiquitous presence in drinking water throughout the United States. In 2016, the United States Environmental Protection Agency (US EPA) issued a lifetime drinking water Health Advisory (HA) for PFOA of 0.07 μg/L; several states have also implemented their own drinking water guidelines for PFOA. The current study aimed to evaluate the basis and derivation of state and federal guidelines for PFOA in drinking water, with particular emphasis on the exposure parameters utilized. Twelve distinct PFOA drinking water standards were identified ranging from 0.0051 to 2 μg/L. The US EPA HA assumptions were evaluated using a Monte Carlo analysis that included distributions for drinking water intake (DWI) rate and the relative source contribution (RSC). We determined that US EPA's HA of 0.07 μg/L is protective of 99% of the population of lactating women. We also demonstrated that the health-based guidelines were highly variable across states and that the actual RSC of PFOA from drinking water is likely greater than 20%, based on studies of actual PFOA exposures from dust, water, and food. A sensitivity analysis was performed using the same equations as the US EPA, while substituting the RSC and DWI variables; resulting in HAs ranging from 0.074 to 0.346 μg/L. We also evaluated the contribution of PFOA in drinking water to the systemic PFOA body burden of the general population using an available biokinetic model. We conclude that more rigorous efforts are warranted to establish consistent health-based drinking water guidelines for PFOA, given that drinking water is a primary source of human exposure to PFOA in the United States.

PFAS soil and groundwater contamination via industrial airborne emission and land deposition in SW Vermont and Eastern New York State, USA

In order to understand the extent to which airborne PFAS emission can impact soil and groundwater, we conducted a sampling campaign in areas of conserved forest lands near Bennington, VT/Hoosick Falls, NY. This has been home to sources of PFAS air-emissions from Teflon-coating operations for over 50 years. Since 2015, the Vermont and New York Departments of Environmental Conservation have documented ∼1200 residential wells and two municipal water systems across a 200 km2 area contaminated with perfluorooctanoic acid (PFOA). Given the large areal extent of the plume, and the fact that much of the contaminated area lies up-gradient and across rivers from manufactures, we seek to determine if groundwater contamination could have resulted primarily from air-emission, land deposition, and subsequent leaching to infiltrating groundwater. Sampling of soils and groundwater in the Green Mountain National Forest (GMNF) downwind of factories shows that both soil and groundwater PFOA contamination extend uninterrupted from inhabited areas into conserved forest lands. Groundwater springs and seeps in the GMNF located 8 km downwind, but >300 meters vertically above factories, contain up to 100 ppt PFOA. Our results indicate that air-emitted PFAS can contaminate groundwater and soil in areas outside of those normally considered down-gradient of a source with respect to regional groundwater flow.

PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding

We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on 2 to 5 legacy PFAS, and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly, and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine measurements complemented by suspect screening using high-resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids. Available data suggest that diet is the major human exposure pathway for some PFAS, but there is large variability across populations and PFAS compounds. Additional data on total fluorine in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, for the general population, exposures from dust, personal care products, indoor environments, and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a reevaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations. Environ Toxicol Chem 2021;40:631-657. © 2020 SETAC.

Characterizing the Air Emissions, Transport, and Deposition of Per- and Polyfluoroalkyl Substances from a Fluoropolymer Manufacturing Facility

Per- and polyfluoroalkyl substances (PFASs) have been released into the environment for decades, yet contributions of air emissions to total human exposure, from inhalation and drinking water contamination via deposition, are poorly constrained. The atmospheric transport and fate of a PFAS mixture from a fluoropolymer manufacturing facility in North Carolina were investigated with the Community Multiscale Air Quality (CMAQ) model applied at high resolution (1 km) and extending ∼150 km from the facility. Twenty-six explicit PFAS compounds, including GenX, were added to CMAQ using current best estimates of air emissions and relevant physicochemical properties. The new model, CMAQ-PFAS, predicts that 5% by mass of total emitted PFAS and 2.5% of total GenX are deposited within ∼150 km of the facility, with the remainder transported out. Modeled air concentrations of total GenX and total PFAS around the facility can reach 24.6 and 8500 ng m-3 but decrease to ∼0.1 and ∼10 ng m-3 at 35 km downwind, respectively. We find that compounds with acid functionality have higher deposition due to enhanced water solubility and pH-driven partitioning to aqueous media. To our knowledge, this is the first modeling study of the fate of a comprehensive, chemically resolved suite of PFAS air emissions from a major manufacturing source.

Epigenetic Modifications, and Alterations in Cell Cycle and Apoptosis Pathway in A549 Lung Carcinoma Cell Line upon Exposure to Perfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a group of human-made compounds with strong C-F bonds, and have been used in various manufacturing industries for decades. PFAS have been reported to deleterious effect on human health, which has led to studies identifying the possible toxicity and toxicity routes of these compounds. We report that these compounds have the potential to cause epigenetic modifications, and to induce dysregulation in the cell proliferation cycle as well as apoptosis in A549 lung cancer cells when exposed to 10-, 200- and 400 μM concentrations of each compound. Our studies show that exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) may cause hypomethylation in the epigenome, but changes in the epigenetic makeup are not evident upon exposure to GenX. We establish that exposure to lower doses of these compounds causes the cells' balance to shift to cell proliferation, whereas exposure to higher concentrations shifts the balance more towards apoptosis. Furthermore, the apoptosis pathway upon exposure to GenX, PFOA, and PFOS has also been identified. Our findings suggest that exposure to any of these compounds may have profound effects in patients with pre-existing lung conditions or could trigger lung cancinogenesis.

Aqueous Film-Forming Foams Exhibit Greater Interfacial Activity than PFOA, PFOS, or FOSA

Perfluoroalkyl acids spontaneously concentrate at air-water and non-aqueous phase liquid (NAPL)-water interfaces, which can influence their retention during subsurface transport. This work presents measurements of air- and NAPL-water interfacial tension for synthetic groundwater containing perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorooctanesulfonamide (FOSA), or aqueous film-forming foam (AFFF) formulations at concentrations ranging from 0.1 to greater than 1000 mg/L. The NAPLs tested included dodecane, tetrachloroethylene, and jet fuel. AFFF formulations were less efficient at lowering interfacial tension than PFOA, FPOS, or FOSA substances below 100 mg/L, while above 100 mg/L, these formulations were more effective, achieving tensions of less than 3 mN/m. Infiltration of solutions with such low tension could lead to mobilization of residual NAPL. Equations based on interfacial tension measurements show that concentrations of PFOA, PFOS, and FOSA at the air-water interface were from 2 to 16 times greater than at the NAPL-water interface below 100 mg/L and were 10-50 times greater for AFFF below 20 mg/L. Calculations for unsaturated soil estimate that up to 87% of PFOS mass was at the air-water interface and less than 4% at the dodecane-water interface for bulk-water concentrations below 1 mg/L.

A Review of the Applications, Environmental Release, and Remediation Technologies of Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are pollutants that have demonstrated a high level of environmental persistence and are very difficult to remediate. As the body of literature on their environmental effects has increased, so has regulatory and research scrutiny. The widespread usage of PFAS in industrial applications and consumer products, complicated by their environmental release, mobility, fate, and transport, have resulted in multiple exposure routes for humans. Furthermore, low screening levels and stringent regulatory standards that vary by state introduce considerable uncertainty and potential costs in the environmental management of PFAS. The recalcitrant nature of PFAS render their removal difficult, but existing and emerging technologies can be leveraged to destroy or sequester PFAS in a variety of environmental matrices. Additionally, new research on PFAS remediation technologies has emerged to address the efficiency, costs, and other shortcomings of existing remediation methods. Further research on the impact of field parameters such as secondary water quality effects, the presence of co-contaminants and emerging PFAS, reaction mechanisms, defluorination yields, and the decomposition products of treatment technologies is needed to fully evaluate these emerging technologies, and industry attention should focus on treatment train approaches to improve efficiency and reduce the cost of treatment.

Bacterial community in a freshwater pond responding to the presence of perfluorooctanoic acid (PFOA)

Microbial community is an essential component of freshwater, providing valuable self-purification ecosystem service. Poly-and perfluoroalkyl substances (PFAS) have attracted increasing concerns in light of their potential ecotoxicological effects and ubiquitous occurrence in the aquatic environment. Knowledge about their influences on the microbial community, however, remains largely unknown. In the present study, Illumina high-throughput sequencing of 16S ribosomal DNA was applied to explore the changes in the dynamic and composition of the bacterial community upon exposure to perfluorooctanoic acid (PFOA) at different concentrations, i.e. 0.45 µg L^-1, 130 µg L^-1 and 5.0 mg L^-1. Principal component analysis (PCA) revealed variations of 57.2% for Principal Component 1 and 16.0% for Principal Component 2 of the total community. This clearly demonstrated changes in the bacterial community structure between the controls and PFOA-amended water samples. At the phylum level, the predominant bacteria in the original pond water included Proteobacteria (64.47%), Armatimonadetes (11.87%), Actinobacteria (10.81%), Bacteroidetes (6.36%), Chloroflexi (1.44%), Verrucomicrobia (0.61%) and Firmicutes (0.14%). The relative abundance of Actinobacteria, Bacteroidetes, and Verrucomicrobia decreased 26.5-38.8%, 40.5-70.7%, and 47.4-87.5%, respectively, upon PFOA exposure. By contrast, PFOA led to an obvious increase of Proteobacteria, by 12.5-18.6% and Chloroflexi by 19.1-74.4%. Results from this study provided the needed evidence that PFAS at high concentrations could affect the microbial community in a freshwater ecosystem. Principle Component Analysis (PCA) results suggest clear distinctions of bacterial community structure between the original pond water and the water samples spiked with PFOA based on pyrosequencing of 16S rRNA gene.

PFAS concentrations in soils: Background levels versus contaminated sites

Per- and polyfluoroalkyl substances (PFAS) are contaminants of critical concern due to their persistence, widespread distribution in the environment, and potential human-health impacts. In this work, published studies of PFAS concentrations in soils were compiled from the literature. These data were combined with results obtained from a large curated database of PFAS soil concentrations for contaminated sites. In aggregate, the compiled data set comprises >30,000 samples collected from >2500 sites distributed throughout the world. Data were collected for three types of sites- background sites, primary-source sites (fire-training areas, manufacturing plants), and secondary-source sites (biosolids application, irrigation water use). The aggregated soil-survey reports comprise samples collected from all continents, and from a large variety of locations in both urban and rural regions. PFAS were present in soil at almost every site tested. Low but measurable concentrations were observed even in remote regions far from potential PFOS sources. Concentrations reported for PFAS-contaminated sites were generally orders-of-magnitude greater than background levels, particularly for PFOS. Maximum reported PFOS concentrations ranged upwards of several hundred mg/kg. Analysis of depth profiles indicates significant retention of PFAS in the vadose zone over decadal timeframes and the occurrence of leaching to groundwater. It is noteworthy that soil concentrations reported for PFAS at contaminated sites are often orders-of-magnitude higher than typical groundwater concentrations. The results of this study demonstrate that PFAS are present in soils across the globe, and indicate that soil is a significant reservoir for PFAS. A critical question of concern is the long-term migration potential to surface water, groundwater, and the atmosphere. This warrants increased focus on the transport and fate behavior of PFAS in soil and the vadose zone, in regards to both research and site investigations.

Scientific Basis for Managing PFAS as a Chemical Class

This commentary presents a scientific basis for managing as one chemical class the thousands of chemicals known as PFAS (per- and polyfluoroalkyl substances). The class includes perfluoroalkyl acids, perfluoroalkylether acids, and their precursors; fluoropolymers and perfluoropolyethers; and other PFAS. The basis for the class approach is presented in relation to their physicochemical, environmental, and toxicological properties. Specifically, the high persistence, accumulation potential, and/or hazards (known and potential) of PFAS studied to date warrant treating all PFAS as a single class. Examples are provided of how some PFAS are being regulated and how some businesses are avoiding all PFAS in their products and purchasing decisions. We conclude with options for how governments and industry can apply the class-based approach, emphasizing the importance of eliminating non-essential uses of PFAS, and further developing safer alternatives and methods to remove existing PFAS from the environment.

NUrF-Optimization of in situ UV-vis and fluorescence and autonomous characterization techniques with small-angle neutron scattering instrumentation

We have designed, built, and validated a (quasi)-simultaneous measurement platform called NUrF, which consists of neutron small-angle scattering, UV-visible, fluorescence, and densitometry techniques. In this contribution, we illustrate the concept and benefits of the NUrF setup combined with high-performance liquid chromatography pumps to automate the preparation and measurement of a mixture series of Brij35 nonionic surfactants with perfluorononanoic acid in the presence of a reporter fluorophore (pyrene).

Evidence of Air Dispersion: HFPO-DA and PFOA in Ohio and West Virginia Surface Water and Soil near a Fluoropolymer Production Facility

Perfluorooctanoic acid (PFOA) was used as a fluoropolymer manufacturing aid at a fluoropolymer production facility in Parkersburg, WV from 1951 to 2013. The manufacturer introduced a replacement surfactant hexafluoropropylene oxide dimer acid (HFPO-DA) that has been in use at this site since 2013. Historical releases of PFOA and related epidemiological work in this area has been primarily focused on communities downstream. To provide an update on the ongoing impacts from this plant, 94 surface water samples and 13 soil samples were collected mainly upstream and downwind of this facility. PFOA was detected in every surface water sample with concentrations exceeding 1000 ng/L at 13 sample sites within an 8 km radius of the plant. HFPO-DA was also found to be widespread with the highest levels (>100 ng/L) found in surface water up to 6.4 km north of the plant. One sample site, 28 km north of the plant, had PFOA at 143 ng/L and HFPO-DA at 42 ng/L. Sites adjacent to landfills containing fluorochemical waste had PFOA concentrations ranging up to >1000 ng/L. These data indicate that downwind atmospheric transport of both compounds has occurred and that the boundaries of the impact zone have yet to be fully delineated.

Capture of Perfluorooctanoic Acid Using Oil-Filled Graphene Oxide-Silica Hybrid Capsules

Fluorinated hydrocarbon (FHC) contamination has attracted global attention recently because of persistence within the environment and ecosystems of many types of FHC. The surfactant perfluorooctanoic acid (PFOA) is particularly commonly found in contaminated sites, and thus, urgent action is needed for its removal from the environment. In this study, water dispersible hybrid capsules were successfully prepared from an oil-in-water emulsion stabilized by graphene oxide and including a silicate precursor to grow a strong, mesoporous capsule shell surrounding the droplets. These capsules were decorated with amine groups to present a positively charged outer corona that attracts negative PFOA molecules. The aminated capsules were effectively applied as a novel technology to adsorb and sequester PFOA contamination in water. It was confirmed that PFOA removal by the capsules was pH and PFOA concentration dependent, with adsorption efficiencies of >60 mg g^-1 under ideal conditions. PFOA removal kinetics followed using high-performance liquid chromatography and liquid chromatography-mass spectrometry showed that capture of PFOA by the capsules reached a maximum of >99.9% in 2-3 days.

Influence of soil physicochemical properties on the depth profiles of perfluoroalkylated acids (PFAAs) in soil along a distance gradient from a fluorochemical plant and associations with soil microbial parameters

The widespread use of perfluoroalkylated acids (PFAAs) has led to a global presence in the environment, in which they accumulate and may cause detrimental effects. Although soils are known sinks for many persistent organic pollutants, still little is known on the behaviour of PFAAs in soils. Furthermore, studies that examine the relationships between PFAA concentrations and soil microbial parameters are scarce. The 3 M fluorochemical plant near Antwerp has been characterized as a PFAAs hotspot. In the present study, we examined the vertical distribution of 15 PFAAs and their associations with multiple physicochemical soil properties along a distance gradient from this hotspot. Additionally, we tested the relationships between PFAA concentrations in the top soil with soil respiration, microbial activity and microbial biomass. Our results show that both perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) concentrations were elevated in the subsurface layer (up to 50 cm), after which concentrations decreased again, suggesting a downward migration of both analytes in the soil. This downward movement might pose a potential threat for the contamination of the groundwater and, consequently, organisms that rely on this water for consumption. The soil concentrations were influenced by multiple physicochemical properties of the soil, which suggests differences in bioavailability and sorption/desorption capacities between different soil types. We did not observe any influence of PFAA contamination in the top soil on microbial activity and biomass nor soil respiration.

Contamination of groundwater with per- and polyfluoroalkyl substances (PFAS) from legacy landfills in an urban re-development precinct

The extent of per- and polyfluoroalkyl substances (PFAS) in groundwater surrounding legacy landfills is currently poorly constrained. Seventeen PFAS were analysed in groundwater surrounding legacy landfills in a major Australian urban re-development precinct. Sampling locations (n = 13) included sites installed directly in waste material and down-gradient from landfills, some of which exhibited evidence of leachate contamination including elevated concentrations of ammonia-N (≤106 mg/L), bicarbonate (≤1,740 mg/L) and dissolved methane (≤10.4 mg/L). Between one and fourteen PFAS were detected at all sites and PFOS, PFHxS, PFOA and PFBS were detected in all samples. The sum of detected PFAS (∑₁₄PFAS) varied from 26 ng/L at an ambient background site to 5,200 ng/L near a potential industrial point-source. PFHxS had the highest median concentration (34 ng/L; range: 2.6-280 ng/L) followed by PFOS (26 ng/L; range: 1.3-4,800 ng/L), PFHxA (19 ng/L; range: <LOQ - 46 ng/L) and PFOA (12 ng/L; range: 1.7-74 ng/L). Positive correlations between ∑₁₄PFAS, PFOA and other perfluoroalkyl carboxylic acids (PFCAs) (e.g. PFHxA) with typical leachate indicators including ammonia-N and bicarbonate were observed. In contrast, no such correlations were found with perfluoroalkyl sulfonic acids (PFSAs) (e.g., PFOS and PFHxS). In addition, a strong positive linear correlation (R² = 0.69) was found between the proportion of PFOA in the sum of detected perfluorinated alkylated acids (PFOA/∑PFAA) and ammonia-N concentrations in groundwater. This is consistent with previous research showing relatively high PFOA/∑PFAA in municipal landfill leachates, and more conservative behaviour (e.g. less sorption and reactivity) of PFCAs during subsurface transport compared to PFSAs. PFOA/∑PFAA in groundwater may therefore be a useful indicator of municipal landfill-derived PFAA. One site with significantly elevated PFOS and PFHxS concentrations (4,800 and 280 ng/L, respectively) appears to be affected by point-source industrial contamination, as landfill leachate indicators were absent.

Matrix-specific distribution and compositional profiles of perfluoroalkyl substances (PFASs) in multimedia environments

This study investigated perfluoroalkyl substances (PFASs) in multimedia environments to confirm the effects of emission sources of PFASs and to elucidate their spatial distribution. The highest PFAS levels were detected from the samples of air (272.30 pg/m³) and surface water (36.54 ng/L) in an industrial complex area, meanwhile high PFAS levels were found from the samples of soil (8.80 ng/g) and sediment (84.98 ng/g) in urban areas and near wastewater treatment plants (WWTPs). Perfluorobutane sulfonate (PFBS) was primarily detected in water, influent and effluent, whereas long chain perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS) were dominant in dust, soil, sediment and sludge. While PFBS and neutral PFASs were dominant in air, PFCAs were primarily detected in plant and fish. The specific distribution patterns of PFASs in each matrix showed the influences of surrounding environments and different physicochemical characteristics of each congener. These findings suggest that the industrial complex and WWTP might be major emission sources to air and aquatic environments, respectively. This is the first study in which 6 neutral and 13 ionic PFASs were investigated simultaneously for nine different matrices in multimedia environments, and also it would be a good model study for future assessment of PFASs.

Distribution and partitioning of perfluoroalkyl carboxylic acids in surface soil, plants, and earthworms at a contaminated site

A field study was conducted to elucidate distribution and partitioning of perfluoroalkyl carboxylic acids (PFCAs; C7-12) in a terrestrial ecosystem that was contaminated with industrial sources of release. Surface soil (0-6 cm), plants, and earthworms were collected from a field located within a 1-mile radius of a fluoropolymer industry that had been manufacturing fluorochemicals for over five decades. The mean concentrations of ∑PFCAs were 150, 420, 61, 68, and 430 ng/g dry weight (dw) in surface soil, earthworms, grass roots, grass leaves, and tree leaves, respectively. The measured concentrations were higher than those reported for corresponding matrices in other locations worldwide, suggesting that fluorochemical manufacturing operations have contributed to the contamination of this nearby land. Soil and plant tissues consisted mainly of perfluorooctanoic acid (PFOA; C8) (77.3-97.1% of the total PFCAs), whereas longer-chain PFCAs, such as perfluoroundecanoic acid (PFUnDA; C11: 17.6%) and perfluorododecanoic acid (PFDoDA; C12: 31.9%), accounted for relatively higher proportions in earthworms. Spatial distribution of PFCAs at this site suggested that both atmospheric deposition and groundwater recharge have contributed to the sources of contamination. Both earthworm- and grass-accumulated PFCAs from soil with biota-soil accumulation factors and root concentration factors increased with perfluorocarbon chain length. The translocation factors of PFCAs in grass decreased as the number of carbons in the fluorocarbon moiety increased. This field study is appropriate to improve our understanding of partitioning of PFCAs among soil, plants, and earthworms.

Treatment of perfluoroalkyl acids by heat-activated persulfate under conditions representative of in situ chemical oxidation

Perfluoroalkyl acids (PFAAs) are a class of organic contaminants notable for their extreme persistence. The unique chemical properties of these compounds make them difficult to remove from water using most standard water treatment techniques. To gain insight into the possibility of remediating contaminated groundwater by in situ chemical oxidation with heat-activated persulfate, PFAA removal and the generation of transformation products were evaluated under laboratory conditions. Solution pH had a strong influence on the removal of perfluorooctanoic acid (PFOA), resulting in its transformation into shorter-chain perfluorocarboxylic acids (PFCAs) at pH values below 3. The presence of chloride and aquifer sediments decreased the efficiency of the process by less than 25% under conditions likely to be encountered in drinking water aquifers. Perfluorooctane sulfonic acid (PFOS) was not transformed by heat-activated persulfate under any of the conditions tested. Despite challenges related to the need to manipulate aquifer pH, the possible generation of undesirable short-chain PFCAs and chlorate, and metals mobilization, heat-activated persulfate may be a useful treatment technology for sites contaminated with PFCAs and fluorotelomer-based compounds, including those used in current-generation aqueous film-forming foams.