Short-chain Perfluoroalkyl Substances Research Articles

DART isotope dilution high resolution mass spectrometry and 19F-NMR detection of fluorotelomeric alcohols in hydrolyzed food contact paper

Fluorotelomer-based acrylate polymers and surfactants used to grease-proof food contact paper (FCP) are potential sources of dietary exposure to perfluoroalkyl substances (PFAS). Food contact substances (FCS) containing polyfluorinated long-chains (≥C8) were voluntarily removed by their manufacturers from the U.S. market in 2011 due to health concerns and largely replaced with FCSs containing short-chain (≤C7) PFAS. In 2020, FDA findings of potential biopersistence of 6:2 FTOH (CF3(CF2)5CH2CH2OH) similarly prompted an additional voluntarily phase-out of FCSs containing 6:2 FTOH by their manufacturers that was completed by the end of 2023. To monitor the phase-out process, a screening method was developed to detect FCPs containing ester-linked polyfluorinated pendant chains. Direct Analysis in Real Time-Isotope Dilution-High Resolution Mass Spectrometry (DART-ID-HRMS) enabled rapid semi-quantitative detection of 6:2 FTOH in FCP saponification reaction headspace without requiring sample concentration or chromatography. 19F-NMR analysis confirmed 6:2 FTOH pendant chain identity and detection dependence on saponification. The speed and specificity of this approach arise from ester saponification in the presence of stable isotopically labeled 6:2 FTOH; high FTOH differential volatility relative to nonfluorinated matrix, and the facile production of FTOH gas-phase anions (e.g., [M + O2]·−, [M-H + CO2]−) under ambient ionization conditions. The efficiency of this simple workflow makes it well-suited for monitoring the phase-out of FCS containing ester-linked polyfluorinated chains from the U.S. marketplace.

Bioaccumulation mechanisms of perfluoroalkyl substances (PFASs) in aquatic environments: Theoretical and experimental insights

Per- and polyfluoroalkyl substances (PFASs) are persistent, bioaccumulative contaminants found in water resources at levels hazardous to human health. However, the PFAS bioaccumulation mechanism remains poorly understood. In this study, we incorporated density functional theory (DFT), molecular dynamics (MD), and experiments to analyze the partitioning pathways and to establish the structure-bioaccumulation relationship. DFT- and MD-calculated environmental fate parameters, comprising LogPO,W, LogPA,W, and diffusion coefficients, coincide with experiments at various ranges of PFAS molecules, with a correction coefficient (R²) of 0.783. MD simulations revealed that medium or long-chain-length PFASs spontaneously aggregate into submicelles in aquatic environments, enhancing their bioaccumulation effect. The short-chain PFASs show weak aggregation, but they also permeate into biological membranes. Particularly, it was discovered that aggregating PFASs “dissolve” into the lipid membrane matrix, owing significantly to van der Waals interactions rather than electrostatic effects. Thermodynamic analysis suggests that PFAS translocation involves spatial flips along the free energy surface. Short-chain PFASs exhibit low steric hindrance, contributing to bioaccumulation—a factor previously neglected in research. PFAS bioaccumulation depends on chain length, as further confirmed by intracellular reactive oxygen species formation and live/dead quantification in HepG2 cells. These insights advance our understanding of PFAS bioaccumulation mechanisms and highlight critical factors influencing their environmental and biological behavior.

Spatial distribution, source apportionment, and risk assessment of perfluoroalkyl substances in urban soils of a typical densely urbanized and industrialized city, Northeast China

As an important capital city of intensive urbanization and industrialization in Northeast China, Changchun has experienced extremely rapid development, with diverse sectors such as automobile manufacturing, equipment manufacturing, optoelectronics, and pharmaceutical decoration. However, data on the levels and profiles of perfluoroalkyl substances (PFASs) in urban soils of Changchun is limited. This study investigated 17 PFASs across various functional zones within the main urban area of Changchun. ∑PFAS concentrations in the soils ranged from 0.236 to 6.483 ng/g, averaging 1.820 ng/g. Perfluorocarboxylic acids (PFCAs) were more prevalent than perfluorosulfonic acids (PFSAs), and short-chain PFASs (C ≤ 6) were the predominant residues. PFAS concentrations varied across functional zones, with commercial markets exhibiting the highest levels, followed by industrial areas, residential areas, suburban zones, and transportation areas. Molecular diagnostic ratio and PCA-MLR analysis identified industrial production processes of consumer goods and wastewater treatment plants as the primary sources of soil PFAS contamination. There were no obvious health risks of soil ∑PFASs, while soil PFOS and PFHxS may have an impact on the richness and diversity of soil microbial communities in some certain locations. This study provides new data on PFAS residues in soils influenced by diverse contamination sources within a key industrial city in Northeast China, offering valuable insights for prioritizing remediation and restoration efforts.

Investigation of the Deionization Rate of Asymmetric Capacitive Deionization Technology for the Treatment of Short-Chain Perfluoroalkyl Substances (PFAS)

Objectives : This study aims to introduce and evaluate the effectiveness of asymmetric membrane capacitive deionization (ACDI) in removing short-chain perfluoroalkyl substances (PFAS), specifically perfluorobutane sulfonic acid (PFBS), from aqueous solutions. This study offers important insights for the advancement of CDI technology in the sustainable treatment of industrial wastewater containing PFAS.Methods : ACDI was employed by removing the anion exchange membrane from conventional membrane capacitive deionization system. The effect of key operational parameters such as voltage (0.5~1.2 V), initial concentration (50~500 mg/L), and flow rate (1~5 ml/min) on PFBS removal efficiency was systematically investigated. Additionally, PFBS removal performance in the presence of chloride ions was also investigated to determine competing ion effects.Results and Discussion : The ACDI system significantly outperformed both CDI and MCDI, achieving a maximum deionization rate of 0.032 mg/g/s, compared to 0.012 mg/g/s for CDI and 0.01 mg/g/s for MCDI. Increasing the applied voltage from 0.5 V to 1.2 V enhanced the deionization rate, with the highest rate observed at 1.2 V. Higher initial PFBS concentrations also improved the deionization rate, increasing from 0.0009 mg/g/s at 50 mg/L to 0.032 mg/g/s at 500 mg/L. The optimal flow rate was found to be 2 ml/min, balancing ion contact time and throughput, resulting in the highest deionization rate. The presence of competing ions, such as chloride, reduced PFBS removal efficiency, as shown by the decrease in deionization rate when NaCl was added to the feed solution.Conclusion : Overall, the ACDI system demonstrated superior deionization capacity and energy efficiency for PFBS removal, highlighting its potential as a sustainable and efficient technology for treating water contaminated with short-chain PFAS. Future research should address the challenges posed by competing ions in real-world wastewater to further optimize the ACDI system’s performance.

Efficient adsorption of short-chain perfluoroalkyl substances by pristine and Fe/Cu-loaded reed straw biochars

As the substitutes of legacy long-chain per-/polyfluoroalkyl substances (PFASs), short-chain PFASs have been widely detected in the environment. Compared to long-chain PFASs, short-chain PFASs have smaller molecules and are more hydrophilic. Therefore, they are more likely to experience long-distance transport and pose lasting environmental impacts. In this study, Fe-doped (R-Fe) and Cu-doped biochars (R-Cu) were prepared using reed straw biochar (R). The results showed that the PFBA and PFPeA sorption capacities of R-Fe were 25.81 and 43.59 mg g−1, 1.65 and 1.55 times higher than those of R, respectively. The PFBA and PFPeA sorption capacities of R-Cu were 19.34 and 33.69 mg g−1, 1.24 and 1.20 times higher than those of R, respectively. In addition, R, R-Fe, and R-Cu exhibited higher PFBA and PFPeA sorption capacities than the biochars previously reported. The excellent PFAS sorption performances of the biochars were attributed to the highly porous structure of R, which provided rich adsorption sites. Ion-pair sorption, pore filling, electrostatic interaction between the Fe/Cu and cationic groups on biochar and the anionic groups of PFASs, and hydrophobic interaction between the hydrophobic surface of biochar and the fluorinated tails of PFASs were the underlying sorption mechanisms. The biochars presented high removal rates (>86 %) of multiple PFASs (∑PFAS: 350 μg L−1) from synthetic wastewaters, including legacy and emerging PFASs of different chain lengths and with different functional groups. The biochars reported in this study are promising candidate adsorbents for treating waters contaminated with short-chain PFASs.

Cationic surfactant-assisted foam fractionation enhances the removal of short-chain perfluoroalkyl substances from impacted water

Several studies have demonstrated that air-bubbling and foam fractionation techniques can efficiently remove long-chain PFAS from contaminated water. However, removing short-chain PFAS is challenging due to its lower surface activity and inability to form self-assembly structures at the air-water interface. In this study, we tested various additives, including salts, surfactants, and polymers, to improve short-chain PFAS (e.g., perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA)) removal in non-foaming solutions using a bench-scale system. We found that in the presence of cetyltrimethylammonium chloride (CTAC) and salt, air-bubbling can significantly remove 0.5 μg L−1 of PFBS and PFBA in deionized water by >99% (15 min) and 81% (60 min), respectively. The decline of surface tension and the formation of thin foam-like layers during bubbling, controlled by the concentration of CTAC, significantly improved the removal of short-chain PFAS. Adding anionic and neutral surfactants showed no removal of short-chain PFAS during bubbling, suggesting the importance of the electrostatic interactions between short-chain PFAS and the cationic CTAC. We observed a 1:1 M ratio between CTAC and PFBS removed from the solution, suggesting the formation of ion pairs in the solution and enhancing the surface activity of the overall neutral (PFAS-CTAC) complex. A mass balance of the system revealed that the primary mechanism by which PFAS was removed from non-foaming waters was through aerosol generation (70−100%). Using the optimized condition, PFAS mixtures (short- and long-chain PFAS, including five recently regulated PFAS by USPEA, 2 nM each) in deionized water and natural groundwater were successfully removed to below detection (>99% removal; <2 ng L−1), except for PFBA (25−73% removal). These results provide an improved understanding of the mechanism by which PFAS is removed during foam fractionation and highlight the need for capturing aerosols enriched with PFAS to prevent secondary contamination.

Comparison of perfluoroalkyl substance adsorption performance by inorganic and organic silicon modified activated carbon

Owing to the persistence and increasingly stringent regulations of perfluoroalkyl substances (PFAS), it is necessary to improve their adsorption capacities using activated carbon (AC). However, their adsorption capacities are suppressed by dissolved organic matter (DOM). In this study, two ACs modified with organic silicon (C-OS) and inorganic silicon (C-IS) were synthesized and used for the adsorption of PFAS in raw water (RW). The results showed that the PFAS adsorption capacity of C-IS was much less influenced by DOM than that of the original AC (C-virgin). In RW, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption capacities on C-IS were 15.08 and 3.65 times higher than those on C-virgin, respectively. DOM had less influence on the PFOA and PFOS adsorption kinetics of C-IS than C-OS and C-virgin. Under multi-PFAS condition, C-IS also exhibited slower desorption of short-chain PFAS and breakthrough in batch and column tests, respectively. Characterization of the ACs before and after adsorption and independent gradient modelling indicated that hydrogen bond interactions between the O-Si of C-IS and the –COOH or –CSO3H groups of PFAS contributed to PFAS adsorption. Density functional theory calculations demonstrated that the adsorption energy of C-IS was much lower than that of C-OS and C-virgin. The arrangement of PFAS molecules on C-OS was chaotic owing to the hydrophobic siloxane chain, whereas the arrangement of PFAS on C-IS was orderly in multi-layer or semi-micelle status and more favorable to PFAS adsorption. This study provides a new strategy for avoiding adverse effects of DOM on PFAS adsorption.

Efficient removal of short-chain perfluoroalkyl substances (PFAS) using asymmetric membrane capacitive deionization

Concerns have been raised over the persistence and potential health risks of perfluoroalkyl substances (PFAS). PFAS pose significant challenges in water treatment owing to their chemical stability and the difficulty of treating them with conventional purification methods. Although traditional water treatment methods for contaminant removal have been explored, their effectiveness against PFAS remains limited. This gap in knowledge highlights the need for innovative approaches. This study introduces asymmetric membrane capacitive deionization (ACDI) as a novel method for short-chain PFAS removal to address the shortcomings of existing techniques. ACDI refers to a configuration in which an anion exchange membrane is removed from a conventional membrane capacitive deionization with both a cation exchange membrane and an anion exchange membrane. Among the PFAS, perfluorobutanesulfonic acid (PFBS), which is known to be difficult to remove because of its short chain, has been the focus. The ACDI system demonstrated superior deionization capacity (28.75 mg/g) and energy efficiency (energy consumption of 0.46 Wh/g) compared to conventional CDI and membrane CDI systems. In addition, the effects of key operating parameters, such as voltage (0.5 ∼ 1.2 V), initial concentration (50 ∼ 500 mg/L), and flow rate (1 ∼ 5 mL/min), on the PFBS removal were systematically investigated and superior at 1.2 V, 500 mg/L, and 2 mL/min. This study suggests the need for further exploration of real-world applications considering the presence of competing ions in wastewater. This study provides valuable insights into advancing CDI technology for the sustainable treatment of industrial wastewater containing PFAS.

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 &amp;lt;8 and PFSAs &amp;lt;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&amp;gt;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, &amp;lt;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&amp;gt;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.