Short-chain Perfluoroalkyl Substances Research Articles

Exploring organic and inorganic contaminant histories in sediment cores across the anthropocene: Accounting for site/area dependent factors

Sedimentary records help chronologically identify anthropogenic contamination in environmental systems. This study analysed dated sediment cores from L’Albufera Lake (Valencia, Spain), to assess the occurrence of heavy metals (HMs), polycyclic aromatic hydrocarbons (PAHs), perfluoroalkyl substances (PFASs), organophosphorus flame retardants (OPFRs), pesticides and pharmaceuticals and personal care products (PPCPs). The results evidence the continuing vertical presence of all types of contaminants in this location. The sediment age was difficult to establish. However, the presence of shells together with an historical estimation and the knowledge of sedimentary rates could help. HMs contents are higher in the upper layer reflecting the most recent increase of the industrial and agricultural practices in the area since the middle 20th century. Higher availability index of these HMs in the upper sediment layers is associated with point and diffuse contamination sources in the area. PAHs and OPFRs were homogeneous distributed through the sediments with few exceptions such as phenanthrene in the North and fluoranthene in the South. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) were detected throughout the sediment core while short-chain PFASs (except perfluoropentanoic acid (PFPeA)) were detected only in the top layer. Pesticides and PPCPs showed appreciable down-core mobility. The vertical concentration profiles of organic contaminants did not exhibit a clear trend with depth, then, it is difficult to develop a direct relationship between sediment age and contaminant concentrations, and to elucidate the historical trend of contamination based on dated sediment core. Consequently, linking contaminant occurrence in sediments directly to their historical use is somewhat speculative at least in the conditions of L’Albufera Lake.

Abstract 828: Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-cohort study

Abstract Background: Perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), notable representatives of perfluoroalkyl substances (PFASs), are synthetic persistent chemicals widely accumulated and detected in humans. Short-chain PFASs [PFCAs with carbon number <8 and PFSAs <6, e.g. perfluoroheptanoic acid (PFHpA)] are considered less bioaccumulative and increasingly used in commercial products, yet their health impacts are rarely investigated. Perfluorooctanoic acid (PFOA) has been categorized as a possible human carcinogen (group 2B) and a potential mammary toxicant. However, few population studies explored the prospective associations of PFOA and other common PFASs with breast cancer risk nor the underlying mechanisms. Methods: Hence, we conducted a case-cohort study within the DongFeng-Tongji Cohort, compromising 226 incident breast cancer cases and a random sub-cohort of 990 individuals. Plasma concentrations of four PFCAs [PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and PFHpA] and two PFSAs [perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS)], as well as peripheral blood mitochondrial DNA copy number (mtDNAcn) levels, were measured at baseline. Results: Using Barlow-weighted Cox regression, we found 35% and 20% increased incident risk of breast cancer for each 1-unit ln-transformed increase in PFOA and PFHpA, respectively [HR (95% CI) = 1.35 (1.03, 1.78) and 1.20 (1.02, 1.40)]. Quantile g-computation analysis revealed a 19% increased incident risk of breast cancer along with each simultaneous quartile increase in all ln-transformed PFCA concentrations [HR (95% CI) = 1.19 (1.01, 1.41)], driven mainly by contributions from PFOA (56%), PFNA (24%), and PFHpA (20%). Besides, mtDNAcn was positively associated with PFHpA levels [β (95% CI) =0.027 (0.005, 0.048)], but not with PFOA or PFNA (P>0.05). We also found significantly higher breast cancer risk in participants with the highest mtDNAcn (Q4, ≥1.52) than those with the lowest (Q1, <0.87) [HR (95% CI) =2.92 (1.69, 5.04)], and that mtDNAcn mediated 12.77% of PFHpA-breast cancer association [Indirect effect, HR (95% CI) =1.02 (1.00, 1.04)]. No significant mediation effect of mtDNAcn was observed in associations of PFOA and PFNA with breast cancer (P>0.05). Conclusions: Our work unveiled the relationship of short-chain PFHpA with increased incident risk of breast cancer for the first time and highlighted the intermediate role of mtDNAcn in this association, providing a research clue for exploring the potential mechanisms of PFAS-induced breast cancer. Moreover, co-exposure to PFASs was observed as a risk factor for breast cancer, shedding light on breast cancer prevention by regulating PFASs as a chemical class. Citation Format: Yue Feng, Huan Guo. Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-cohort study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 828.

Adsorption of perfluoroalkyl substances on deep eutectic solvent-based amorphous metal-organic framework: Structure and mechanism

Perfluoroalkyl substances (PFASs) are a class of emerging organic pollutants characterized by high toxicity, environmental persistence, and widespread detection in water sources. The removal of PFASs from water is a matter of global concern, given their detrimental impact on both the environment and public health. Many commonly used PFAS adsorbents demonstrate limited adsorption capacities and/or slow adsorption kinetics. Therefore, there is an urgent need for the development of efficient adsorbents. For the first time, this work systematically investigated the performance of a deep eutectic solvent (DES)-based amorphous metal-organic framework (MOF) for the adsorption of PFASs with different carbon-chain lengths under the state of the mixture in aquatic environments. The adsorption mechanism was probed by a suite of adsorption kinetics studies, adsorption isotherm profiling, spectral characterization, and ab initio molecular dynamics (AIMD) simulations, revealing that PFAS adsorption is driven by synergistic capturing effects including acid/base coordination, CF-π (carbon-fluorine-π), hydrogen bonding, and hydrophobic interactions. Furthermore, the adsorption processes of short-chain and long-chain targets were found to involve different rate-controlling steps and interaction sites. Hydrophobic interactions facilitated the swift arrival of long-chain PFASs at the coordinatively interacting sites between carboxyl termini and Lewis acid Zr unsaturated sites, thanks to their lower reaction barriers. On the other hand, the adsorption of short-chain PFASs primarily relied on a Zr hydroxyl-based ligand exchange force, which would take place at Brønsted acid sites. The existence of massive structural disorder in amorphous UiO-66 led to the development of larger pores, thus improving the accessibility of abundant adsorption sites and facilitating adsorption and diffusion. The presence of multiple types of interactions and flexible structure in defect-rich amorphous UiO-66 significantly increased the exposure of functional groups to the adsorbates. Additionally, this material possessed outstanding regeneration efficiency and outperformed other MOF-based adsorbents with high affinity for targets. It enhances our understanding of the adsorption performances and mechanisms of amorphous materials toward PFASs, thereby paving the way for designing more efficient PFAS adsorbents.

Insight into the differential toxicity of PFOA and PFBA based on a 3D-cultured MDA-MB-231 cell model

Perfluoroalkyl substances (PFASs) are a category of high-concerned emerging contaminants which are suspected to correlate with various human adverse health outcomes including tumors. It is also a question whether short-chain PFASs are qualified alternatives under the regulation of long-chain PFASs. In this study, a three-dimensional (3D) culture system based on Gelatin methacrylate (GelMA) hydrogel matrix was used to investigate the impacts of 120-h perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) exposure of MDA-MB-231 cells. The results showed that PFOA exposure promoted the proliferation, migration, and invasion of MDA-MB-231 cells in an environmentally relevant concentration range (0.1 to 10 μM), exhibiting a clear malignant-promoting risk. In contrast, PFBA only showed a trend to induce non-invasive cell migration. Hippo/YAP signaling pathway was identified as the contributor to the differences between the two PFASs. PFOA but PFBA reduced YAP phosphorylation and increased the nuclear content of YAP, which further facilitated abundant key factors of epithelial-mesenchymal transition (EMT) process. Our results provided a new idea for the carcinogenicity of PFOA using a 3D-based paradigm. Although the effects by PFBA were much milder than PFOA in the current test duration, the cell model suitable for longer exposure is still necessary to better assess the safety of alternative short-chain PFASs.

Bioaccumulation Characteristics of Typical Perfluoroalkyl Compounds in Alfalfa Under Salt Stress.

Medicago sativa, commonly known as alfalfa, is widely distributed worldwide, known for its strong stress resistance and well-developed root system, making it an important plant in ecological restoration research. To investigate the absorption and transport characteristics of alfalfa for typical perfluoroalkyl substances (PFAS) under salt stress, a 30-day indoor greenhouse experiment was conducted. The results showed that alfalfa exhibited varying degrees of absorption and transport for the selected PFAS. The highest BCF (Bioconcentration Factor) for shoot tissue reached 725.4 (for PFBA), and the highest TF (Translocation Factor) reached 53.8 (for PFPeA). Different PFAS compounds exhibited distinct bioaccumulation behaviors, with short-chain PFAS more readily entering the plant's root system and being transported upwards, while long-chain PFAS tended to adsorb to the surface of the root system. Furthermore, salt stress did not significantly affect the uptake of PFAS by alfalfa. This suggests that alfalfa is salt-tolerant and holds great potential for ecological restoration in short-chain PFAS-contaminated sites.

Durable water- and oil-repellent textiles without long- or short-chain perfluoroalkylated substances

For decades, the water and oil repellency of textiles was achieved using long-chain (CnF2n+1, n ≥ 7) perfluoroalkyl substances (PFAS). However, due to their proven bioaccumulative nature and toxic impacts on the environment and human health, these substances have been phased out of industrial production and/or legally banned in many countries. There is some evidence that a shorter carbon chain leads to less bioaccumulation and toxicity, and accordingly short-chain PFAS have been widely used as a replacement in recent years. Nevertheless, short-chain PFAS exhibit inferior surface properties due to their less crystalline and more loosely packed polymer chains, as compared to their long-chain counterparts. Moreover, surface properties become worse with decreasing chain length. Here we develop an alternative method for obtaining durable water and oil repellency on a nylon fabric using a liquidlike perfluoropolyether (PFPE) brush coating. The coating demonstrates excellent water and oil repellency, on par with the banned long-chain PFAS finishes, although its longest PFAS degradation product would have a chain length of L = 3, i.e. an ultra-short-chain PFAS. The PFPE-treated nylon exhibits superior surface properties compared to state-of-the-art, short-chain PFAS finished fabrics used in industry currently, even after laundering and 10,000 cycles of abrasion. The comfort of the treated fabrics is also maintained. The PFPE coatings developed here could replace the toxic, short-chain PFAS in use worldwide today.

Continuous-flow titration of low iron doses to promote photo-Fenton and photo-Fenton-like processes at neutral pH

Photo-Fenton (PF) is a promising process for degrading a wide range of contaminants of emerging concern (CECs) present in urban wastewater (UWW) after secondary treatment, mitigating their spread in aquatic systems. However, the near-neutral pH of UWW poses a challenge to PF performance. In this research, a tubular membrane photoreactor, designed for continuous “titration” of Fe2+, is explored to promote the PF process for the tertiary treatment of UWW. The application of persulfate (PF-like) as an alternative oxidant and the impact of phosphate (PO43−) content in UWW were also assessed. Process efficiency was evaluated in continuous mode, applying low residence times (RT: 6.1, 36.6, and 73.2 s) and low Fe2+ doses (1, 2, and 5 mg L−1), for the oxidation of 19 CECs (each spiked at 10 µg/L), in demineralized water (DW) and secondary-treated UWW. Despite the persistence of certain short-chain perfluoroalkyl substances (PFAS) and saccharine across all conditions tested, the PF-like process exhibited superior performance when compared with PF, attaining higher removals for most target CECs, especially for melamine. In UWW, for an RT = 73.2 s, [Fe2+] = 5 mg L−1, and [oxidant] = 1.2 mM, PF process removed 7 CECs > 60 % and PF-like 10 CECs > 60 %. Moreover, higher residual concentrations of Fe2+ and lower precipitation of PO43− were observed for PF-like treatments, evidencing its advantages for tertiary treatment. These results emphasize the importance of photoreactor design to achieve efficient PF/PF-like at neutral pH, avoiding the use of chelating agents while managing iron concentrations compatible with UWW discharge or reuse limits.

Biomagnification and temporal trends (1990–2021) of perfluoroalkyl substances in striped dolphins (Stenella coeruleoalba) from the NW Mediterranean sea

Poly- and Perfluoroalkyl Substances (PFAS) are a well-known class of pollutants which can bioaccumulate and biomagnify with a vast majority being highly persistent. This study aims to determine the biomagnification rates of PFAS in sexually mature striped dolphins and to assess temporal trends on PFAS concentrations over the past three decades (1990–2021) in the North-Western Mediterranean Sea. Thirteen and 17 of the 19 targeted PFAS were detected in the samples of the dolphins’ digestive content and liver, respectively, at concentrations ranging between 43 and 1609 ng/g wet weight, and 254 and 7010 ng/g wet weight, respectively. The most abundant compounds in both types of samples were linear perfluorooctanesulfonic acid (n-PFOS) and perfluorooctanesulfonamide (FOSA), which were present in all samples, followed by perfluoroundecanoic acid (PFUnDA), perfluorotridecanoic acid (PFTrDA) and perfluorononanoic acid (PFNA). Long-chain PFAS (i.e., PFCAs C ≥ 7 and PFSAs C ≥ 6) biomagnified to a greater extent than short-chain PFAS, suggesting a potential effect on the health of striped dolphins. Environmental Quality Standards concentrations set in 2014 by the European Union were exceeded in half of the samples of digestive content, suggesting that polluted prey may pose potential health risks for striped dolphins. Concentrations of most long-chain PFAS increased from 1990 to 2004–2009, then stabilized during 2014–2021, possibly following country regulations and industrial initiatives. The current study highlights the persistent presence of banned PFAS and may contribute to future ecological risk assessments and the design of management strategies to mitigate PFAS pollution in marine ecosystems.

Legacy and novel perfluoroalkyl substances in major economic species of invertebrates in South China Sea: Health implication from consumption

Continuously release of perfluoroalkyl substances (PFASs) would pose non-negligible impacts on environment, organisms, and human health. In present study, 18 PFASs in 7 typical economic invertebrates and their habitats were investigated from the South China Sea. The higher concentrations of PFASs in the nearshore water (6.61–15.54 ng/L) and sediment (0.82–8.84 ng/g) obviously due to frequent human activities. Long-chain PFASs have tendency to accumulate in sediment, however, short-chain PFASs dominated in biota. The acute reference dose (%ARfD) and hazard ratios (HR) of major PFASs in biota were all <100 %, and also below 1, respectively, which means that consumption of PFASs from seafood does not pose risk and threat to human health. However, it should be taken into account that the HR of PFHxA in Mimachlamys nobilis reached 0.82. Potential adverse effects toward human health induced by short-chain PFASs (such as <6 C) via invertebrate seafood consumption should be concerned.

Losses of Ultrashort- and Short-Chain PFAS to Polypropylene Materials

Losses of long-chain poly-/per-fluoroalkyl substances (PFAS) due to adsorption on polypropylene (PP) materials have been reported in the literature. However, there is a lack of information on losses of ultrashort-/short-chain PFAS to PP materials, particularly in environmentally relevant conditions. In this study, we evaluated the losses of ultrashort-chain perfluoropropionic acid (PFPrA) and two short-chain PFAS, viz., perfluorobutanoic acid (PFBA) and perfluorobutanesulfonic acid (PFBS), to PP. Losses up to 20 ± 1% were observed for the studied PFAS after 24 h from 100 μg/L solutions. Losses varied greatly between PP tubes of different brands, probably due to differences in the availability of adsorption sites. Several processes were involved in the adsorptive losses of the three compounds. For example, charge screening and hydrophobic interactions affected the behavior of PFBS and PFBA. Lower losses observed in methanol and wastewater can be explained by the higher PFAS solubility and competition with other organics, respectively. This study highlights that laboratory-specific PFAS losses shall be carefully considered as they can prevent accurate trace analysis of short-chain PFAS. Our results will also help to improve the accuracy of future monitoring and adsorption studies of ultrashort-/short-chain PFAS.

Periodically reversing electrocoagulation technique for efficient removal of short-chain perfluoroalkyl substances from contaminated groundwater around a fluorochemical facility

Widespread distributions of short-chain perfluoroalkyl substances (PFASs) has been recognized as a crucial environmental issue. However, multiple treatment techniques were ineffective due to their high polarity and mobility, contributing to a never-ending existence in the aquatic environment ubiquitously. The present study revealed potential technique of periodically reversing electrocoagulation (PREC) to perform efficient removal of short-chain PFASs including experimental factors (in the conditions of 9 V for voltage, 600 r/min of stirring speed, 10 s of reversing period, and 2 g/L of NaCl electrolyte), orthogonal experiments, actual application, and removal mechanism. Accordingly, based upon the orthogonal experiments, the removal efficiencies of perfluorobutane sulfonate (PFBS) in simulated solution could achieve 81.0% with the optimal parameters of Fe–Fe electrode materials, addition of 665 μL H2O2 per 10 min, and pH at 3.0. The PREC was further applied for treating the actual groundwater around a fluorochemical facility, consequently the removal efficiencies for typical short-chain perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), PFBS, and perfluoropentane sulfonate (PFPeS) were 62.5%, 89.0%, 96.4%, 90.0%, and 97.5%, respectively. The other long-chain PFASs contaminants had superior removal with the removal efficiencies up to 97%–100%. In addition, a comprehensive removal mechanism related to electric attraction adsorption for short-chain PFASs could be verified through the morphological analysis of ultimate flocs composition. The oxidation degradation was further revealed as the other removal mechanism by suspect and nontarget screening of intermediates formed in simulated solution, as well as density functional theory (DFT) calculation theory. Moreover, the degradation pathways about one CF2O molecule or CO2 eliminated with one C atom removed in PFBS by ·OH generated from the PREC oxidation process were further proposed. As a result, the PREC would be a promising technique for the efficient removal of short-chain PFASs from severely contaminated water bodies.

A comprehensive untargeted metabolomics study in zebrafish embryos exposed to perfluorohexane sulfonate (PFHxS)

Perfluorohexane sulfonate (PFHxS) is one of the short-chain perfluoroalkyl substances (PFASs), and frequently detected in the environment, humans, and wildlife, but a detailed mechanism of toxicity has been not studied yet. In this study, a comprehensive set of polar metabolites was determined in i) the developing zebrafish embryo (4, 24, 48, 72, and 120 h post fertilization (hpf)), and ii) in the developing zebrafish after exposure to four concentrations of PFHxS (0.3, 1, 3, and 10 μM) from 24to 120 hpf. The temporal (developmental stages) distribution of individual metabolites (541 metabolites) in zebrafish provided comprehensive information about the biological roles of various metabolites in developing vertebrates such as genetic processes, energy metabolism, protein metabolism, and glycerophospholipid metabolism. PFHxS in zebrafish embryo showed time- and concentration- dependent bioaccumulation, and no baseline toxicity was expected at the test concentrations. However, effects on many metabolites were already observed at the lowest tested concentration (0.3 μM), and these effects were more pronounced at later stages of developmental (72 and 120 hpf). In addition to oxidative stress, the effects of PFHxS on zebrafish embryos were related to the disruption of the fatty acid oxidation (FAO), sugar metabolism, and other metabolic pathways. This study gave new and comprehensive information on the underlying mechanism of the toxicity of PFHxS.

Efficient removal of perfluorobutanesulfonic acid from water through a chitosan/polyethyleneimine xerogel

Due to the recently ratified legislations, the use of long-chain poly- and perfluoroalkyl substances (PFASs) must be reduced and in the absence of a safe alternative, short-chain PFASs are currently used in their place. The continuously growing utilization of the short-chain PFASs, results in their abrupt introduction in the environment, and highlights the importance of adopting efficient remediation strategies. This study addresses an appropriate solution to remove perfluorobutanesulfonic acid (PFBS) from aqueous media through a static adsorption process. Specifically, a chitosan/polyethyleneimine based composite xerogel was prepared and its ability to remove PFBS from water was studied in detail. Behavioral patterns of the PFBS adsorption process were perused over a broad range of concentrations from ppb to ppm, and the adsorption studies reveal that the maximum PFBS adsorption capacity reaches up to 305 mg/g within 24 h from the beginning of the process. In addition to the electrostatic interaction between the amine groups of the xerogels and the negatively charged PFBS molecules, the formation of hydrogen bonds were also revealed by the chemical characterization and confirmed by molecular dynamics simulation studies.

Study on Pollution Characteristics of Perfluoroalkyl Substances (PFASs) in Shallow Groundwater

Perfluoroalkyl substances (PFASs) in shallow groundwater are increasingly being studied due to the global occurrence, environment persistence, bioaccumulation, and potential human health risk. In this research, 16 PFAS (11 perfluorinated carboxylic acids and 5 perfluorinated sulfonic acids) concentrations in groundwater were quantified to obtain information on geographical distribution and PFAS detection pattern for 4 years in South Korea. In the results, groundwater PFAS concentration ranged from non-detectable to average 45.2 ng/L (sum of PFASs). The major PFAS compounds were perfluorooctanoic acid (PFOA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS). The short chain (C &lt; 8) PFASs were more prevalent than long chain (C &gt; 8) PFASs in shallow groundwater. However, the detection patterns of 15 PFASs were different for each aquifer. Subsequently, through a health risk assessment, a non-carcinogenic risk level through ingestion, inhalation, and dermal contact for PFOA and PFOS was determined at 10−1, and it presents the need for PFAS management of groundwater.

Imparting Selective Fluorophilic Interactions in Redox Copolymers for the Electrochemically Mediated Capture of Short-Chain Perfluoroalkyl Substances

With increasing regulations on per- and polyfluoroalkyl substances (PFAS) across the world, understanding the molecular level interactions that drive their binding by functional adsorbent materials is key to effective PFAS removal from water streams. With the phaseout of legacy long-chain PFAS, the emergence of short-chain PFAS has posed a significant challenge for material design due to their higher mobility and hydrophilicity and inefficient removal by conventional treatment methods. Here, we demonstrate how cooperative molecular interactions are essential to target short-chain PFAS (from C4 to C7) by tailoring structural units to enhance affinity while modulating the electrochemical control of capture and release of PFAS. We report a new class of fluorinated redox-active amine-functionalized copolymers to leverage both fluorophilic and electrostatic interactions for short-chain PFAS binding. We combine molecular dynamics (MD) simulations and electrosorption to elucidate the role of the designer functional groups in enabling affinity toward short-chain PFAS. Preferential interaction coefficients from MD simulations correlated closely with experimental trends: fluorination enhanced the overall PFAS uptake and promoted the capture of less hydrophobic short-chain PFAS (C ≤ 5), while electrostatic interactions provided by secondary amine groups were sufficient to capture PFAS with higher hydrophobicity (C ≥ 6). The addition of an induced electric field showed favorable kinetic enhancement for the shortest PFAS and increased the reversibility of release from the electrode. Integration of these copolymers with electrochemical separations showed potential for removing these contaminants at environmentally relevant conditions while eliminating the need for chemical regeneration.

Sorptive removal of short-chain perfluoroalkyl substances (PFAS) during drinking water treatment using activated carbon and anion exchanger

Laboratory tests and column tests were carried out in a waterwoks to investigate the removal of short- and long-chain PFAS using activated carbon filtration and ion exchange treatment. For all adsorbents, the sorption affinity of short-chain per- and polyfluoroalkyl carboxylic acids (PFCA) was significantly lower than that of long-chain PFAS or short-chain per- and polyfluoroalkyl sulfonic acids (PFSA). In the PFAS-polluted groundwater matrix, the short-chain PFCA PFBA and PFPeA could only be sufficiently removed with activated carbon over short run times of 6000 and 11,000 bed volumes (BV), respectively. Longer PFCA with a chain length of C6 or more were removed over longer run times.The removal of short-chain PFCA using ion exchange media could also only be achieved over relatively short run times of 5000 BV for PFBA, 10,000BV for PFPeA and 18,000 BV for PFHxA. These are sometimes significantly longer than those of activated carbon. Due to the higher material costs for ion exchange media, there are nevertheless no lower operating costs when the ion exchangers are used in single-use mode. However, ion exchangers can be regenerated and then reused which can result in economic advantages compared to activated carbon filtration. However, for the extensive regeneration, especially for the elution of the long-chain PFAS, the additional use of ethanol is needed in the process. In contrast, the short-chain PFBA and PFPeA can be extracted without organic solvent from a weakly basic ion exchanger.

Different Sources, Fractionation, and Migration of Legacy and Novel Per- and Polyfluoroalkyl Substances between Greenhouse and Open-Field Soils.

Perfluoroalkyl substances (PFASs) are widely present in agricultural soils, but their sources and fate in greenhouse soils remain unclear. In this study, the sources, fractionation, and migration of PFASs were compared in the greenhouse and open-field soils of the Fen-Wei Plain, China. The total concentrations of PFASs (Σ17PFAS) were comparable in the greenhouse and open-field soils but with different profiles. Detrended correspondence and correlation analyses indicated that dry deposition was an important source of PFASs in the open-field soils, whereas surface water had a notable contribution to the greenhouse soils due to more frequent irrigation. The PFASs in the soils were mainly present in water-soluble fraction (F1). The F1 proportions of short-chain and long-chain PFASs were negatively correlated with the anion exchange capacity (AEC) and organic carbon content (foc) in soil, respectively, with that of short-chain PFASs being higher than long-chain ones. The AEC was significantly higher while foc was lower in the greenhouse soil than the open-field soil, leading to lower proportions of F1 for short-chain PFASs while higher for long-chain ones in the greenhouse soil. Frequent irrigation and elevated temperatures promoted the migration of PFASs in greenhouse soil; thus, the Σ17PFAS and F1 exhibited an increasing trend with soil depth.

Insights into the Dermal Absorption, Deposition, and Elimination of Poly- and Perfluoroalkyl Substances in Rats: The Importance of Skin Exposure.

Humans are frequently exposed to poly- and perfluoroalkyl substances (PFASs) via direct skin contact with personal care and consumer products containing them. Here, we used a rat model to estimate the dermal penetration efficiency of 15 representative PFASs. After 144 h post-dosing, 4.1-18.0 and 5.3-15.1% of the applied PFASs in the low (L) and high (H) groups, respectively, were absorbed into the rats. PFAS absorption and permeation were parabolically associated with the perfluorinated carbon chain length (CF), peaking for perfluoroheptanoic acid (PFHpA). The lipid-rich stratum corneum of the skin barrier substantially suppressed the penetration of less hydrophobic short-chain PFASs, whereas the water-rich viable epidermis and dermis served as obstacles to hydrophobic long-chain PFAS permeation. However, the renal clearance (CLrenal) of the target PFAS decreased with increasing CF, suggesting that urinary excretion is crucial to eliminate less hydrophobic short-chain PFASs. Notably, the peak times of PFASs in the systemic circulation of rats (8-72 h) were remarkably longer than those after oral administration (1-24 h). These results suggest that dermal penetration can be long-lasting and contribute considerably to the body burden of PFASs, especially for those with moderate hydrophobicity due to their favorable skin permeation and unfavorable urinary excretion.

XGBoost model as an efficient machine learning approach for PFAS removal: Effects of material characteristics and operation conditions

Due to the implications of poly- and perfluoroalkyl substances (PFAS) on the environment and public health, great attention has been recently made to finding innovative materials and methods for PFAS removal. In this work, PFAS is considered universal contamination which can be found in many wastewater streams. Conventional materials and processes used to remove and degrade PFAS do not have enough competence to address the issue particularly when it comes to eliminating short-chain PFAS. This is mainly due to the large number of complex parameters that are involved in both material and process designs. Here, we took the advantage of artificial intelligence to introduce a model (XGBoost) in which material and process factors are considered simultaneously. This research applies a machine learning approach using data collected from reported articles to predict the PFAS removal factors. The XGBoost modeling provided accurate adsorption capacity, equilibrium, and removal estimates with the ability to predict the adsorption mechanisms. The performance comparison of adsorbents and the role of AI in one dominant are studied and reviewed for the first time, even though many studies have been carried out to develop PFAS removal through various adsorption methods such as ion exchange, nanofiltration, and activated carbon (AC). The model showed that pH is the most effective parameter to predict PFAS removal. The proposed model in this work can be extended for other micropollutants and can be used as a basic framework for future adsorbent design and process optimization.

Perfluorobutanoic Acid (PFBA) Induces a Non-Enzymatic Oxidative Stress Response in Soybean (Glycine max L. Merr.).

Short-chain perfluoroalkyl substances (PFAS) are generally considered to be of less environmental concern than long-chain analogues due to their comparatively shorter half-lives in biological systems. Perfluorobutanoic acid (PFBA) is a short-chain PFAS with the most root–shoot transfer factor of all PFAS. We investigated the impact of extended exposure of soybean plants to irrigation water containing environmentally relevant (100 pg–100 ng/L) to high (100 µg–1 mg/L) concentrations of PFBA using phenotypical observation, biochemical characterization, and transcriptomic analysis. The results showed a non-monotonous developmental response from the plants, with maximum stimulation and inhibition at 100 ng/L and 1 mg/L, respectively. Higher reactive oxygen species and low levels of superoxide dismutase (SOD) and catalase (CAT) activity were observed in all treatment groups. However transcriptomic analysis did not demonstrate differential expression of SOD and CAT coding genes, whereas non-enzymatic response genes and pathways were enriched in both groups (100 ng/L and 1 mg/L) with glycine betaine dehydrogenase showing the highest expression. About 18% of similarly downregulated genes in both groups are involved in the ethylene signaling pathway. The circadian rhythm pathway was the only differentially regulated pathway between both groups. We conclude that, similar to long chain PFAS, PFBA induced stress in soybean plants and that the observed hormetic stimulation at 100 ng/L represents an overcompensation response, via the circadian rhythm pathway, to the induced stress.