Fluorotelomer alcohol biodegradation-direct evidence that perfluorinated carbon chains breakdown

Analysis of Legacy and Novel Neutral Per- and Polyfluoroalkyl Substances in Soils from an Industrial Manufacturing Facility

Per- and polyfluoroalkyl substances (PFASs) have been detected in an array of environmental media due to their ubiquitous use in industrial and consumer products as well as potential release from fluorochemical manufacturing facilities. During their manufacture, many fluorotelomer (FT) facilities rely on neutral intermediates in polymer production including the FT-alcohols (FTOHs). These PFAS are known to transform to the terminal acids (perfluoro carboxylic acids; PFCAs) at rates that vary with environmental conditions. In the current study on soils from a FT facility, we employed gas chromatography coupled with conventional- and high-resolution mass spectrometry (GC-MS and GC-HRMS) to investigate the profile of these precursor compounds, the intermediary secondary alcohols (sFTOHs), FT-acrylates (FTAcr), and FT-acetates (FTAce) in soils around the former FT-production facility. Of these precursors, the general trend in detection intensity was [FTOHs] > [sFTOHs] > [FTAcrs], while for the FTOHs, homologue intensities generally were [12:2 FTOH] > [14:2 FTOH] > [16:2 FTOH] > [10:2 FTOH] > [18:2 FTOH] > [20:2 FTOH] > [8:2 FTOH] ∼ [6:2 FTOH]. The corresponding terminal acids were also detected in all soil samples and positively correlated with the precursor concentrations. GC-HRMS confirmed the presence of industrial manufacturing byproducts such as FT-ethers and FT-esters and aided in the tentative identification of previously unreported dimers and other compounds. The application of GC-HRMS to the measurement and identification of precursor PFAS is in its infancy, but the methodologies described here will help refine its use in tentatively identifying these compounds in the environment.

A review of the occurrence and microbial transformation of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF)-impacted environments

Aqueous film-forming foams (AFFFs) have been extensively used for extinguishing hydrocarbon-fuel fires at military sites, airports, and fire-training areas. Despite being a significant source of per- and polyfluoroalkyl substances (PFAS), our understanding of PFAS occurrence in AFFF formulations and AFFF-impacted environments is limited, as is the impact of microbial transformation on the environment fate of AFFF-derived PFAS. This literature review compiles PFAS concentrations in electrochemical fluorination (ECF)- and fluorotelomer (FT)-based AFFFs and provides an overview of PFAS occurrence in AFFF-impacted environments. Our analysis reveals that AFFF use is a predominant point source of PFAS contamination, including primary precursors (polyfluoroalkyl substances as AFFF components), secondary precursors (polyfluoroalkyl transformation products of primary precursors), and perfluoroalkyl acids (PFAAs). Moreover, there are discrepancies between PFAS concentration profiles in AFFFs and those measured in AFFF-impacted media. For example, primary precursors constitute 52.6 % and 99.5 % of PFAS mass in ECF- and FT-based AFFFs, respectively, whereas they represent only 0.7 % total mass in AFFF-impacted groundwater. Conversely, secondary precursors, which constitute <1 % of PFAS in AFFFs, represent 4.0-27.8 % of PFAS in AFFF-impacted environments. The observed differences in PFAS levels between AFFFs and environmental samples are likely due to in-situ biotransformation processes. Biotransformation rates and pathways reported for AFFF-derived primary and secondary precursors varied among different classes of precursors, consistent with the PFAS occurrence in AFFF-impacted environments. For example, readily biodegradable primary precursors, N-dimethyl ammonio propyl perfluoroalkane sulfonamide (AmPr-FASA) and n:2 fluorotelomer thioether amido sulfonate (n:2 FtTAoS), were rarely detected in AFFF-impacted environments. In contrast, key secondary precursors, perfluoroalkane sulfonamides (FASAs) and n:2 fluorotelomer sulfonate (n:2 FTS), were widely detected, which was attributed to their resistance to biotransformation. Key knowledge gaps and future research priorities are presented to better understand the occurrence, fate, and transport of AFFF-derived PFAS in the environment and to design more effective remediation strategies.

Using Network Analysis and Predictive Functional Analysis to Explore the Fluorotelomer Biotransformation Potential of Soil Microbial Communities

Microbial transformation of per- and polyfluoroalkyl substances (PFAS), including fluorotelomer-derived PFAS, by native microbial communities in the environment has been widely documented. However, few studies have identified the key microorganisms and their roles during the PFAS biotransformation processes. This study was undertaken to gain more insight into the structure and function of soil microbial communities that are relevant to PFAS biotransformation. We collected 16S rRNA gene sequencing data from 8:2 fluorotelomer alcohol and 6:2 fluorotelomer sulfonate biotransformation studies conducted in soil microcosms under various redox conditions. Through co-occurrence network analysis, several genera, including Variovorax, Rhodococcus, and Cupriavidus, were found to likely play important roles in the biotransformation of fluorotelomers. Additionally, a metagenomic prediction approach (PICRUSt2) identified functional genes, including 6-oxocyclohex-1-ene-carbonyl-CoA hydrolase, cyclohexa-1,5-dienecarbonyl-CoA hydratase, and a fluoride-proton antiporter gene, that may be involved in defluorination. This study pioneers the application of these bioinformatics tools in the analysis of PFAS biotransformation-related sequencing data. Our findings serve as a foundational reference for investigating enzymatic mechanisms of microbial defluorination that may facilitate the development of efficient microbial consortia and/or pure microbial strains for PFAS biotransformation.

Phase transitions of fluorotelomer alcohols at the water|alkane interface studied via molecular dynamics simulation

Fluorosurfactants are long-lasting environmental pollutants that accumulate at interfaces ranging from aerosol droplet surfaces to cell membranes. Modeling of adsorption-based removal technologies for fluorosurfactants requires accurate simulation methods which can predict their adsorption isotherm and monolayer structure. Fluorotelomer alcohols with one or two methylene groups adjacent to the alcohol (7 : 1 FTOH and 6 : 2 FTOH, respectively) are investigated using the OPLS-AA force field at the water|hexane interface, varying the interfacial area per surfactant. The acquired interfacial pressure isotherms and monolayer phase behavior are compared with previous experimental results. The results are consistent with the experimental data inasmuch as, at realistic adsorption densities, only 7 : 1 FTOH shows a phase transition between liquid-expanded (LE) and 2D crystalline phases. Structures of the LE and crystalline phases are in good agreement with the sticky disc and Langmuir defective crystal models, respectively, used previously to interpret experimental data. Interfacial pressure of the LE phase agrees well with experiment, and sticky disc interaction parameters indicate no 2D LE-gas transition is present for either molecule. Conformation analysis reveals 7 : 1 FTOH favors conformers where the OH dipole is perpendicular to the molecular backbone, such that the crystalline phase is stabilized when these dipoles align.

Stability and Biotransformation of 6:2 Fluorotelomer Sulfonic Acid, Sulfonamide Amine Oxide, and Sulfonamide Alkylbetaine in Aerobic Sludge

The 6:2 fluorotelomer sulfonamide (6:2 FTSAm)-based compounds signify a prominent group of per- and polyfluoroalkyl substances (PFAS) widely used in contemporary aqueous film-forming foam (AFFF) formulations. Despite their widespread presence, the biotransformation behavior of these compounds in wastewater treatment plants remains uncertain. This study investigated the biotransformation of 6:2 FTSAm-based amine oxide (6:2 FTNO), alkylbetaine (6:2 FTAB), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA) in aerobic sludge over a 100-day incubation period. The biotransformation of 6:2 fluorotelomer sulfonamide alkylamine (6:2 FTAA), a primary intermediate product of 6:2 FTNO, was indirectly assessed. Their stability was ranked based on the estimated half-lives (t1/2): 6:2 FTAB (no obvious products were detected) ≫ 6:2 FTSA (t1/2 ≈28.8 days) > 6:2 FTAA (t1/2 ≈11.5 days) > 6:2 FTNO (t1/2 ≈1.2 days). Seven transformation products of 6:2 FTSA and 15 products of 6:2 FTNO were identified through nontarget and suspect screening using high-resolution mass spectrometry. The transformation pathways of 6:2 FTNO and 6:2 FTSA in aerobic sludge were proposed. Interestingly, 6:2 FTSAm was hardly hydrolyzed to 6:2 FTSA and further biotransformed to perfluoroalkyl carboxylic acids (PFCAs). Furthermore, the novel pathways for the generation of perfluoroheptanoic acid (PFHpA) from 6:2 FTSA were revealed.

Perfluorooctanoic acid-induced cell death via the dual roles of ROS-MAPK/ERK signaling in ameloblast-lineage cells

Perfluorooctanoic acid (PFOA) is an artificial fluorinated organic compound that has generated increased public attention due to its potential health hazards. Unsafe levels of PFOA exposure can affect reproduction, growth and development. During tooth enamel development (amelogenesis), environmental factors including fluoride can cause enamel hypoplasia. However, the effects of PFOA on ameloblasts and tooth enamel formation remain largely unknown. In the present study we demonstrate several PFOA-mediated cell death pathways (necrosis/necroptosis, and apoptosis) and assess the roles of ROS-MAPK/ERK signaling in PFOA-mediated cell death in mouse ameloblast-lineage cells (ALC). ALC cells were treated with PFOA. Cell proliferation and viability were analyzed by MTT assays and colony formation assays, respectively. PFOA suppressed cell proliferation and viability in a dose dependent manner. PFOA induced both necrosis (PI-positive cells) and apoptosis (cleaved-caspase-3, γH2AX and TUNEL-positive cells). PFOA significantly increased ROS production and up-regulated phosphor-(p)-ERK. Addition of ROS inhibitor N-acetyl cysteine (NAC) suppressed p-ERK and decreased necrosis, and increased cell viability compared to PFOA alone, whereas NAC did not change apoptosis. This suggests that PFOA-mediated necrosis was induced by ROS-MAPK/ERK signaling, but apoptosis was not associated with ROS. Addition of MAPK/ERK inhibitor PD98059 suppressed necrosis and increased cell viability compared to PFOA alone. Intriguingly, PD98059 augmented PFOA-mediated apoptosis. This suggests that p-ERK promoted necrosis but suppressed apoptosis. Addition of the necroptosis inhibitor Necrostatin-1 restored cell viability compared to PFOA alone, while pan-caspase inhibitor Z-VAD did not mitigate PFOA-mediated cell death. These results suggest that 1) PFOA-mediated cell death was mainly caused by necrosis/necroptosis by ROS-MAPK/ERK signaling rather than apoptosis, 2) MAPK/ERK signaling plays the dual roles (promoting necrosis and suppressing apoptosis) under PFOA treatment. This is the initial report to indicate that PFOA could be considered as a possible causative factor for cryptogenic enamel malformation. Further studies are required to elucidate the mechanisms of PFOA-mediated adverse effects on amelogenesis.

A Review: Per- and Polyfluoroalkyl Substances-Biological Degradation

Per- and polyfluoroalkyl substances (PFASs), highly stable synthetic organic compounds with multiple carbon-fluorine bonds, are emerging as environmental contaminants, toxic, bioaccumulative, and environmentally persistent. PFASs are strongly resistant to biological and chemical degradation, and therefore PFASs present a challenge to researchers and scientists for a better understanding and application of remediation methods and biodegradation of PFASs and have become subject to strict government regulations. The review summarizes the recent knowledge of bacterial and fungal degradation of PFASs, as well as the enzymes involved in the processes of transformation/degradation of PFASs.

High Persistence of Novel Polyfluoroalkyl Betaines in Aerobic Soils

Some contemporary aqueous film-forming foams (AFFFs) contain n:3 and n:1:2 fluorotelomer betaines (FTBs), which are often detected at sites impacted by AFFFs. As new chemical replacements, little is known about their environmental fate. For the first time, we investigated the biotransformation potential of 5:3 and 5:1:2 FTBs and a commercial AFFF that mainly contains n:3 and n:1:2 FTBs (n = 5, 7, 9, 11, and 13). Although some polyfluoroalkyl compounds are precursors to perfluoroalkyl acids, 5:3 and 5:1:2 FTBs exhibited high persistence, with no significant changes even after 120 days of incubation. While the degradation of 5:3 FTB into suspected products such as fluorotelomer acids or perfluoroalkyl carboxylic acids (PFCAs) could not be conclusively confirmed, we did identify a potential biotransformation product, 5:3 fluorotelomer methylamine. Similarly, 5:1:2 FTB did not break down or produce short-chain hydrogen-substituted polyfluoroalkyl acids (n:2 H-FTCA), hydrogen-substituted PFCA (2H-PFCA), or any other products. Incubating the AFFF in four soils with differing properties and microbial communities resulted in 0.023-0.25 mol % PFCAs by day 120. Most of the products are believed to be derived from n:2 fluorotelomers, minor components of the AFFF. Therefore, the findings of the study cannot be fully explained by the current understanding of structure-biodegradability relationships.

Assessing aerobic biotransformation of 8:2 fluorotelomer alcohol in aqueous film-forming foam (AFFF)-impacted soils: Pathways and microbial community dynamics

Production of 8:2 fluorotelomer alcohol (8:2 FTOH) for industrial and consumer products, including aqueous film-forming foams (AFFFs) used for firefighting, has resulted in its widespread occurrence in the environment. However, the fate of 8:2 FTOH at AFFF-impacted sites remains largely unknown. Using AFFF-impacted soils from two United States Air Force Bases, microcosm experiments evaluated the aerobic biotransformation of 8:2 FTOH (extent and byproduct formation) and the dose-response on microbial communities due to 8:2 FTOH exposure. Despite different microbial communities, rapid transformation of 8:2 FTOH was observed during a 90-day incubation in the two soils, and 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were detected as major transformation products. Novel transformation products, including perfluoroalkane-like compounds (1H-perfluoroheptane, 1H-perfluorohexane, and perfluoroheptanal) were identified by liquid chromatography-high resolution mass spectrometry (LC-HRMS) and used to develop aerobic 8:2 FTOH biotransformation pathways. Microbial community analysis suggests that species from genus Sphingomonas are potential 8:2 FTOH degraders based on increased abundance in both soils after exposure, and the genus Afipia may be more tolerant to and/or involved in the transformation of 8:2 FTOH at elevated concentrations. These findings demonstrate the potential role of biological processes on PFAS fate at AFFF-impacted sites through fluorotelomer biotransformation.

A review of microbial degradation of per- and polyfluoroalkyl substances (PFAS): Biotransformation routes and enzymes

Since the 1950s, copious amounts of per- and polyfluoroalkyl substances (PFAS) (dubbed "forever chemicals") have been dumped into the environment, causing heavy contamination of soil, surface water, and groundwater sources. Humans, animals, and the environment are frequently exposed to PFAS through food, water, consumer products, as well as waste streams from PFAS-manufacturing industries. PFAS are a large group of synthetic organic fluorinated compounds with widely diverse chemical structures that are extremely resistant to microbial degradation. Their persistence, toxicity to life on earth, bioaccumulation tendencies, and adverse health and ecological effects have earned them a "top priority pollutant" designation by regulatory bodies. Despite that a number of physicochemical methods exist for PFAS treatment, they suffer from major drawbacks regarding high costs, use of high energy and incomplete mineralization (destruction of the CF bond). Consequently, microbial degradation and enzymatic treatment of PFAS are highly sought after as they offer a complete, cheaper, sustainable, and environmentally friendly alternative. In this critical review, we provide an overview of the classification, properties, and interaction of PFAS within the environment relevant to microbial degradation. We discuss latest developments in the biodegradation of PFAS by microbes, transformation routes, transformation products and degradative enzymes. Finally, we highlight the existing challenges, limitations, and prospects of bioremediation approaches in treating PFAS and proffer possible solutions and future research directions.

Suspect Screening and Nontargeted Analysis of Per- and Polyfluoroalkyl Substances in a Lake Ontario Food Web

Per- and polyfluoroalkyl substances (PFAS) are globally distributed in the natural environment, and their persistent and bioaccumulative potential illicit public concern. The production of certain PFAS has been halted or controlled by regulation due to their adverse effect on the health of humans and wildlife. However, new PFAS are continuously developed as alternatives to legacy PFAS. Additionally, many precursors are unknown, and their metabolites have not been assessed. To better understand the PFAS profiles in the Lake Ontario (LO) aquatic food web, a quadrupole time-of-flight mass spectrometer (QToF) coupled to ultrahigh-performance liquid chromatography (UPLC) was used to generate high-resolution mass spectra (HRMS) from sample extracts. The HRMS data files were analyzed using an isotopic profile deconvoluted chromatogram (IPDC) algorithm to isolate PFAS profiles in aquatic organisms. Fourteen legacy PFAAs (C5-C14) and 15 known precursors were detected in the LO food web. In addition, over 400 unknown PFAS features that appear to biomagnify in the LO food web were found. Profundal benthic organisms, deepwater sculpin(Myoxocephalus thompsonii), and Mysis were found to have more known precursors than other species in the food web, suggesting that there is a large reservoir of fluorinated substances in the benthic zone.

Biotransformation of 8:2 Fluorotelomer Alcohol in Soil from Aqueous Film-Forming Foams (AFFFs)-Impacted Sites under Nitrate-, Sulfate-, and Iron-Reducing Conditions

The environmental fate of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFFs) remains largely unknown, especially under the conditions representative of natural subsurface systems. In this study, the biotransformation of 8:2 fluorotelomer alcohol (8:2 FTOH), a component of new-generation AFFF formulations and a byproduct in fluorotelomer-based AFFFs, was investigated under nitrate-, iron-, and sulfate-reducing conditions in microcosms prepared with AFFF-impacted soils. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-resolution mass spectrometry (HRMS) were employed to identify biotransformation products. The biotransformation was much slower under sulfate- and iron-reducing conditions with >60 mol % of initial 8:2 FTOH remaining after ∼400 days compared to a half-life ranging from 12.5 to 36.5 days under nitrate-reducing conditions. Transformation products 8:2 fluorotelomer saturated and unsaturated carboxylic acids (8:2 FTCA and 8:2 FTUA) were detected under all redox conditions, while 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were only observed as transformation products under nitrate-reducing conditions. In addition, 1H-perfluoroheptane (F(CF₂)₆CF₂H) and 3-F-7:3 acid (F(CF₂)₇CFHCH₂COOH) were identified for the first time during 8:2 FTOH biotransformation. Comprehensive biotransformation pathways for 8:2 FTOH are presented, which highlight the importance of accounting for redox condition and the related microbial community in the assessment of PFAS transformations in natural environments.

Evaluating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal across granular activated carbon (GAC) filter-adsorbers in drinking water treatment plants

Granular activated carbon (GAC) was harvested from six filter-adsorbers that are used for taste and odour control in three drinking water treatment plants in Ontario, Canada, and evaluated for the removal of perfluorooctanic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using minicolumn tests under different operational conditions. Parallel column tests were conducted using unsterilized GAC and sterilized GAC to distinguish adsorption from potential biodegradation of PFOA and PFOS across the GAC. It was observed that the GAC could achieve approximately 20% to 55% of PFOA and PFOS removal even after a long period of GAC operation (e.g., 6 years). There was no evidence of PFOA and PFOS biodegradation, so the removal in GAC can be attributed solely to adsorption under the conditions tested. However, in one location, there was evidence suggesting both removal and formation of PFOS and PFOA across the GAC, with the formation presumably due to the biotransformation of pre-existing precursors in the source water. Additionally, GAC service time and empty bed contact time (EBCT) were identified to be important factors that could affect the removal of PFOA and PFOS. Based on this information, an empirical model was proposed to predict PFOA and PFOS removal in GAC filter-adsorbers as a function of GAC service time and EBCT. This study provides useful information for utilities that have installed GAC for taste and odour control but may consider per- and polyfluoroalkyl substances (PFAS) removal as an additional voluntary objective or due to more stringent guidelines.

Occurrence and contamination profile of legacy and emerging per- and polyfluoroalkyl substances (PFAS) in Belgian wastewater using target, suspect and non-target screening approaches

With the growing concern regarding the health risks of per- and polyfluoroalkyl substances (PFAS), there is an increasing demand for the identification of emerging PFAS. This study provides a comprehensive investigation of legacy and emerging PFAS in 16 wastewater treatment plants (WWTPs) in Belgium using target, suspect, and non-target screening methods. Perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were the dominant compounds in most locations, whereas perfluorooctanoic acid (PFOA) was the most predominant PFAS in WWTP Deurne (Antwerp region). Using a suspect screening approach, 14 PFAS were annotated as confidence level (CL) of 4 or higher and 4 PFAS were annotated as CL 2a and 2b, including aqueous film forming foam (AFFF)-derived PFAS. The compound group of n:3 unsaturated fluorotelomer carboxylic acid was found using non-target screening in the wastewater from WWTP Deurne. Population exposure in a catchment area estimated using population-normalized mass loads (PNML) showed the highest value in the catchment area of WWTP Deurne, implying a potentially higher exposure to PFAS in this community.

Per- and polyfluoroalkyl substances in the atmosphere of waste management infrastructures: Uncovering secondary fluorotelomer alcohols, particle size distribution, and human inhalation exposure

Per- and polyfluoroalkyl substances (PFAS) have been applied in numerous industrial and consumer products, the majority of which flow into waste management infrastructures (WMIs) at the end of their life cycles, but little is known about atmospheric releases of PFAS from these facilities. In this study, we addressed this key issue by investigating 49 PFAS, including 23 ionic and 26 neutral and precursor PFAS, in the potential sources (n = 4; within or adjacent to WMIs) and reference sites (n = 2; coastal and natural reserve sites) in urban and rural areas of Hong Kong, China. Duplicate samples of air and size-segregated particulate matter were collected for 48 h continuously using a 11-stage Micro-Orifice Uniform Deposit Impactor (MOUDI). In general, fluorotelomer alcohols (FTOHs) and perfluoroalkane sulfonamides were the predominant PFAS classes found across sampling sites. We also demonstrated the release of several less frequently observed semivolatile intermediate products (e.g., secondary FTOHs) during waste treatment. Except for perfluorooctane sulfonate, the size-segregated distributions of particulate PFAS exhibited heterogeneity across sampling sites, particularly in the WMIs, implying combined effects of sorption affinity and emission sources. A preliminary daily air emission estimation revealed that landfill was a relatively important source of PFAS relative to the wastewater treatment plant. A simplified International Commission on Radiological Protection model was used to estimate lung depositional fluxes, and the results showed that inhaled particulate PFAS were mainly deposited in the head airway while fine and ultrafine particles carried PFAS deeper into the lung alveoli. The cumulative daily inhalation dose of gaseous and particulate PFAS ranged from 81.9 to 265 pg/kg/d. In-depth research is required to understand the health effect of airborne PFAS on workers at WMIs.

Neutral Per- and Polyfluoroalkyl Substances, Butyl Carbitol, and Organic Corrosion Inhibitors in Aqueous Film-Forming Foams: Implications for Vapor Intrusion and the Environment

Per- and polyfluoroalkyl substances (PFAS), butyl carbitol, and corrosion inhibitors are components of aqueous film-forming foams (AFFFs). Volatile (neutral) fluorotelomerization (FT)- and electrochemical fluorination (ECF)-based PFAS, butyl carbitol, and organic corrosion inhibitors were quantified in 39 military specification (MilSpec), non-MilSpec, and alcohol resistant-AFFF concentrates (undiluted) from 1974 to 2010. Fluorotelomer alcohols were found only in FT-based AFFFs and N-methyl- and N-ethyl-perfluoroalkyl sulfonamides, and sulfonamido ethanols were found only in ECF-based AFFFs. Neutral PFAS and benzotriazole, 4-methylbenzotriazole, and 5-methybenzotriazole occurred at mg/L levels in the AFFFs, while butyl carbitol occurred at g/L levels. Neutral PFAS concentrations in indoor air due to vapor intrusion of a nearby undiluted AFFF release are estimated to be anywhere from 2 to >10 orders of magnitude higher than documented background indoor air concentrations. Estimated butyl carbitol and organic corrosion inhibitor concentrations were lower than and comparable to indoor concentrations recently measured, respectively. The wide range of neutral PFAS concentrations and Henry's law constants indicate that field, soil-gas measurements are needed to validate the estimations. Co-discharged butyl carbitol likely contributes to oxygen depletion in AFFF-impacted aquifers and may hinder the natural PFAS aerobic biotransformation. Organic corrosion inhibitors in AFFFs indicate that these are another source of corrosion inhibitors in the environment.

Foliar uptake overweighs root uptake for 8:2 fluorotelomer alcohol in ryegrass (Lolium perenne L.): A closed exposure chamber study

Fluorotelomer alcohols (FTOHs) are a kind of volatile monomers that can be released from FTOH-based products and their ubiquitous occurrence raises concerns for their plant uptake. To study plant uptake pathway, translocation, and transformation characteristics of 8:2 FTOH, ryegrass (Lolium perenne L.) was selected as a model plant for 8:2 FTOH exposure via air and/or soil uptake for 4 weeks in custom-built closed exposure chambers. The bio-degradation of spiked 8:2 FTOH in the soil led to the production of C6-C8 perfluoroalkyl carboxylic acids (PFCAs) and other intermediates, and perfluorooctanoic acid (PFOA) was the main product (54.9%-88.9%). In the ryegrass, foliar uptake of 8:2 FTOH contributed 78.1% ± 3.4% to the total shoot accumulation while PFOA in shoot was mainly from root uptake of PFOA and the further biotransformation of other unmonitored intermediates biodegraded from 8:2 FTOH in the soil (83.7% ± 7.3%). The results in this study provides the first laboratory evidences that foliar uptake of airborne 8:2 FTOH can be a major pathway over root uptake and its subsequent biotransformation contribute to the burden of PFCA accumulation in plants.

Development of a PFAS reaction library: identifying plausible transformation pathways in environmental and biological systems

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are used in many consumer applications due to their stain repellency, surfactant properties, ability to form water-proof coatings and use in fire suppression. The production, application, transport, use and disposal of PFAS and PFAS-treated products have resulted in their wide-spread occurrence in environmental and biological systems. Concern over exposure to PFAS and their transformation products and metabolites has necessitated the development of tools to predict the transformation of PFAS in environmental systems and metabolism in biological systems. We have developed reaction libraries for predicting transformation products and metabolites in a variety of environmental and biological reaction systems. These reaction libraries are based on generalized reaction schemes that encode the process science of PFAS reported in the peer-reviewed literature. The PFAS reaction libraries will be executed through the Chemical Transformation Simulator, a web-based tool that is available to the public. These reaction libraries are intended for predicting the environmental transformation and metabolism of PFAS only.

Fate of Per- and Polyfluoroalkyl Substances from Durable Water-Repellent Clothing during Use

To make outdoor clothing water- or dirt-repellent, durable water-repellent (DWR) coatings based on side-chain fluorinated polymers (SFPs) are used. During use of outdoor clothing, per- and polyfluoroalkyl substances (PFASs) can be emitted from the DWR to the environment. In this study, the effects of aging, washing, and tumble drying on the concentration of extractable PFASs in the DWR of perfluorohexane-based short-chain SFPs (FC-6 chemistry) and of perfluorooctane-based long-chain SFPs (FC-8 chemistry) were assessed. For this purpose, polyamide (PA) and polyester (PES) fabrics were coated with FC-6- and FC-8-based DWRs. Results show that aging of the coated fabrics causes an increase in concentration and formation of perfluoroalkyl acids (PFAAs). The effect of aging on the volatile PFASs depends on the type of fabric. Washing causes a decrease in PFAA concentrations, and in general, volatile PFASs are partly washed out of the textiles. However, washing can also increase the extractable concentration of volatile PFASs in the fabrics. This effect becomes stronger by a combination of aging and washing. Tumble drying does not affect the PFAS concentrations in textiles. In conclusion, aging and washing of fabrics coated with the DWR based on SFPs release PFASs to the environment.

Global performance and trends of research on per- and polyfluoroalkyl substances (PFASs) between 2001 and 2018 using bibliometric analysis

Per- and polyfluoroalkyl substances (PFASs) are widely used in food packaging, non-stick pots, and surfactants. However, their persistence in the environment, hazardous nature, and potential for bioaccumulation and long-range transport have alarmed an increasing number of scholars and research institutions. Although several literature reviews on PFASs research exist, only a few of them have considered bibliometric indices. In this study, 3,373 PFASs-related articles published between 2001 and 2018 were analyzed using a bibliometric analysis method based on the Science Citation Index (SCI) Expanded. The software tools for mapping knowledge domain (MKD) (VOSviewer and Science of Science (Sci2)) were used to analyze the performance of contributors and PFASs research topics, hotspots, and trends. Our results reveal that the number of PFASs-related articles published annually has increased significantly, with most originating from the United States (followed by those from China). The Chinese Academy of Sciences has published the most articles. A comprehensive analysis of title, keywords, and keywords plus showed that PFASs research hotspots include humans, precursors, and detection methods, with the main focuses being environmental science, toxicology, and environmental engineering. The four main research topics of PFASs were identified, and a literature review was carried out for each one. Overall, this study can supply researchers with a deeper understanding of the development of PFASs studies and provide a comprehensive data reference for researchers to further grasp the research direction in this field.

Microbial Defluorination of Unsaturated Per- and Polyfluorinated Carboxylic Acids under Anaerobic and Aerobic Conditions: A Structure Specificity Study

The recently discovered microbial reductive defluorination of two C₆ branched and unsaturated fluorinated carboxylic acids (FCAs) provided valuable insights into the environmental fate of per- and polyfluoroalkyl substances (PFASs) and potential bioremediation strategies. However, a systematic investigation is needed to further demonstrate the role of C═C double bonds in the biodegradability of unsaturated PFASs. Here, we examined the structure-biodegradability relationships of 13 FCAs, including nine commercially available unsaturated FCAs and four structurally similar saturated ones, in an anaerobic defluorinating enrichment and an activated sludge community. The anaerobic and aerobic transformation/defluorination pathways were elucidated. The results showed that under anaerobic conditions, the α,β-unsaturation is crucial for FCA biotransformation via reductive defluorination and/or hydrogenation pathways. With sp² C-F bonds being substituted by C-H bonds, the reductive defluorination became less favorable than hydrogenation. Moreover, for the first time, we reported enhanced degradability and defluorination capability of specific unsaturated FCA structures with trifluoromethyl (-CF₃) branches at the α/β-carbon. Such FCA structures can undergo anaerobic abiotic defluorination in the presence of reducing agents and significant aerobic microbial defluorination. Given the diverse applications and emerging concerns of fluorochemicals, this work not only advances the fundamental understanding of the fate of unsaturated PFASs in natural and engineered environments but also may provide insights into the design of readily degradable fluorinated alternatives to existing PFAS compounds.

Per- and Polyfluoroalkyl Substances (PFAS) in Facemasks: Potential Source of Human Exposure to PFAS with Implications for Disposal to Landfills

Facemasks are important tools for fighting against disease spread, including Covid-19 and its variants, and some may be treated with per- and polyfluoroalkyl substances (PFAS). Nine facemasks over a range of prices were analyzed for total fluorine and PFAS. The PFAS compositions of the masks were then used to estimate exposure and the mass of PFAS discharged to landfill leachate. Fluorine from PFAS accounted only for a small fraction of total fluorine. Homologous series of linear perfluoroalkyl carboxylates and the 6:2 fluorotelomer alcohol indicated a fluorotelomer origin. Inhalation was estimated to be the dominant exposure route (40%-50%), followed by incidental ingestion (15%-40%) and dermal (11%-20%). Exposure and risk estimates were higher for children than adults, and high physical activity substantially increased inhalation exposure. These preliminary findings indicate that wearing masks treated with high levels of PFAS for extended periods of time can be a notable source of exposure and have the potential to pose a health risk. Despite modeled annual disposal of ~29-91 billion masks, and an assuming 100% leaching of individual PFAS into landfill leachate, mask disposal would contribute only an additional 6% of annual PFAS mass loads and less than 11 kg of PFAS discharged to U.S. wastewater.

Bioremediation of Perfluoroalkyl Substances (PFAS) by Anaerobic Digestion: Effect of PFAS on Different Trophic Groups and Methane Production Accelerated by Carbon Materials

Per- and polyfluoroalkyl substances (PFAS) are recalcitrant pollutants which tend to persist in soils and aquatic environments and their remediation is among the most challenging with respect to organic pollutants. Anaerobic digestion (AD) supplemented with low amounts of carbon materials (CM), acting as electron drivers, has proved to be an efficient process for the removal of organic compounds from wastewater. This work explores the impact of PFAS on different trophic groups in anaerobic communities, and the effect of carbon nanotubes (CNT), activated carbon (AC), and oxidized AC (AC-HNO₃), as electron shuttles on the anaerobic bioremoval of these compounds, based on CH₄ production. The inhibition of the specific methanogenic activity (SMA) exerted by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), at a concentration of 0.1 mg L⁻¹, was below 10% for acetoclastic and below 15%, for acetogenic communities. Hydrogenotrophic methanogens were not affected by the presence of PFAS. All CM reduced the negative impact of PFAS on the CH₄ production rate, but AC was the best. Moreover, the methanization percentage (MP) of sewage sludge (SS) increased 41% in the presence of PFOS (1.2 g L⁻¹) and AC. In addition, AC fostered an increase of 11% in the MP of SS+PFOS, relative to the condition without AC. AC promoted detoxification of PFOA- and PFOS-treated samples by 51% and 35%, respectively, as assessed by Vibrio fischeri assays, demonstrating the advantage of bringing AD and CM together for PFAS remediation.

Per- and polyfluoroalkyl substances in the environment

Over the past several years, the term PFAS (per- and polyfluoroalkyl substances) has grown to be emblematic of environmental contamination, garnering public, scientific, and regulatory concern. PFAS are synthesized by two processes, direct fluorination (e.g., electrochemical fluorination) and oligomerization (e.g., fluorotelomerization). More than a megatonne of PFAS is produced yearly, and thousands of PFAS wind up in end-use products. Atmospheric and aqueous fugitive releases during manufacturing, use, and disposal have resulted in the global distribution of these compounds. Volatile PFAS facilitate long-range transport, commonly followed by complex transformation schemes to recalcitrant terminal PFAS, which do not degrade under environmental conditions and thus migrate through the environment and accumulate in biota through multiple pathways. Efforts to remediate PFAS-contaminated matrices still are in their infancy, with much current research targeting drinking water.

Aerobic biotransformation of a novel highly functionalized polyfluoroether-based surfactant using activated sludge from a wastewater treatment plant

A replacement fluorosurfactant has been recently introduced to the European market as an alternative to other per- and polyfluoroalkyl substances (PFAS) that have been phased-out or banned. Here, we incubated this novel fluorosurfactant (diFESOS, [F₇C₃OCHFCF₂SCH₂CH₂OC(O)]₂C₂H₃SO₃^-) which contains ether and thioether insertions, and its known polyfluoroalkyl degradation products, an alcohol (FESOH) and carboxylic acid (FESCA), with activated sludge from a wastewater treatment plant under sulfur-limited conditions. Dosed chemicals and their transformation products were monitored using ultra-high performance liquid chromatography-tandem mass spectrometry, and gas chromatography-mass spectrometry. In addition to FESOH and FESCA, two smaller metabolites were identified: C₃F₇OCHFCOO^- (2H-3:2 PFECA) and perfluoropropanoic acid (PFPrA). 2H-3:2 PFECA presumably was a result of S-dealkylation of FESCA, which then resulted in the abiotic cleavage of two C-F bonds; no S-oxygenation was observed. Overall, the terminal products of this biotransformation likely have lower bioaccumulation potential than the parent fluorosurfactant based on comparison to other similar PFAS.

Per- and poly-fluoroalkyl substance remediation from soil and sorbents: A review of adsorption behaviour and ultrasonic treatment

Per- and poly-fluoroalkyl substances (PFAS) are xenobiotics, present at variable concentrations in soils and groundwater worldwide. Some of the current remediation techniques being researched or applied for PFAS-impacted soils involve solidification-stabilisation, soil washing, excavation and disposal to landfill, on site or in situ smouldering, thermal desorption, ball milling and incineration. Given the large volumes of soil requiring treatment, there is a need for a more environmentally friendly technique to remove and treat PFASs from soils. Sorbents such as granular/powdered activated carbon, ion exchange resins and silicas are used in water treatment to remove PFAS. In this work, PFAS adsorption mechanisms and the effect of pore size, pH and organic matter on adsorption efficacy are discussed. Then, adsorption of PFAS to soils and sorbents is considered when assessing the viability of remediation techniques. Sonication-aided treatment was predicted to be an effective removal technique for PFAS from a solid phase, and the effect of varying frequency, power and particle size on the effectiveness of the desorption process is discussed. Causes and mitigation strategies for possible cavitation-induced particle erosion during ultrasound washing are also identified. Following soil remediation, degrading the extracted PFAS using sonolysis in a water-organic solvent mixture is discussed. The implications for future soil remediation and sorbent regeneration based on the findings in this study are given.

Structure-Specific Aerobic Defluorination of Short-Chain Fluorinated Carboxylic Acids by Activated Sludge Communities

Per- and polyfluoroalkyl substances (PFAS) are a large group of manmade chemicals that impose emerging environmental concerns. Among them, short-chain per- and polyfluorinated carboxylic acids represent an important subgroup used as building blocks of biologically active chemicals and functional materials. Some are also considered PFAS alternatives, and some could be byproducts of the physicochemical treatment of PFAS. However, little is known about the environmental fate of short-chain fluorinated carboxylic acids (FCAs) and their defluorination/transformation by microorganisms. To fill the knowledge gap, we investigated the structure-reactivity relationships in the aerobic defluorination of C₃-C₅ FCAs by activated sludge communities. Four structures exhibited greater than 20% defluorination, with 3,3,3-trifluoropropionic acid being almost completely defluorinated. We further analyzed the defluorination/transformation pathways and inferred the structures susceptible to aerobic microbial defluorination. We also demonstrated that the defluorination was via cometabolism. The findings advance the fundamental understanding of aerobic microbial defluorination and help assess the environmental fate of PFAS. Since some short-chain PFAS, such as 3,3,3-trifluoropropionic acid, are the incomplete defluorination byproducts of advanced reduction processes, their defluorination by activated sludge communities sheds light on the development of cost-effective chemical-biological PFAS treatment train systems.

Cross-Linking Strategies for Fluorine-Containing Polymer Coatings for Durable Resistant Water- and Oil-Repellency

Functional coatings for application on surfaces are of growing interest. Especially in the textile industry, durable water and oil repellent finishes are of special demand for implementation in the outdoor sector, but also as safety-protection clothes against oil or chemicals. Such oil and chemical repellent textiles can be achieved by coating surfaces with fluoropolymers. As many concerns exist regarding (per)fluorinated polymers due to their high persistence and accumulation capacity in the environment, a durable and resistant coating is essential also during the washing processes of textiles. Within the present study, different strategies are examined for a durable resistant cross-linking of a novel fluoropolymer on the surface of fibers. The monomer 2-((1,1,2-trifluoro-2-(perfluoropropoxy)ethyl)thio)ethyl acrylate, whose fluorinated side-chain is degradable by treatment with ozone, was used for this purpose. The polymers were synthesized via free radical polymerization in emulsion, and different amounts of cross-linking reagents were copolymerized. The final polymer dispersions were applied to cellulose fibers and the cross-linking was induced thermally or by irradiation with UV-light. In order to investigate the cross-linking efficiency, tensile elongation studies were carried out. In addition, multiple washing processes of the fibers were performed and the polymer loss during washing, as well as the effects on oil and water repellency were investigated. The cross-linking strategy paves the way to a durable fluoropolymer-based functional coating and the polymers are expected to provide a promising and sustainable alternative to functional coatings.

Atmospheric particulate represents a source of C8-C12 perfluoroalkyl carboxylates and 10:2 fluorotelomer alcohol in tree bark

In this study, we analyzed 30 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in paired atmospheric particulate and bark samples collected around a Chinese fluorochemical manufacturing park (FMP), with the aim to explore the sources of PFASs in tree bark. The results showed that PFASs in atmospheric particulate and tree bark samples were consistently dominated by perfluorooctanoate (mean 73 ng/g; 44 pg/m3), perfluorohexanoate (47 ng/g; 36 pg/m3), perfluorononanoate (9.1 ng/g; 8.8 pg/m3), and 10:2 fluorotelomer alcohol (10:2 FTOH; 5.6 ng/g; 12 pg/m3). Spatially, concentrations of C8-C12 perfluoroalkyl carboxylates (PFCAs) and 10:2 FTOH all showed a similar and exponentially decreased trend in both bark and atmospheric particulate samples with the increasing distance from the FMP. For the first time, we observed strongly significant (Spearman's correlation coefficient = 0.53-0.79, p < 0.01) correlations between bark and atmospheric particulate concentrations for C8-C12 PFCAs and 10:2 FTOH over 1-2 orders of magnitude, suggesting that the continues trapping of atmospheric particulates resulted in the accumulation of these compounds in bark. Overall, this study provides the first evidence that atmospheric particulate is an obvious source of C8-C12 PFCAs and 10:2 FTOH in tree bark. This result may further contribute to the application of tree bark as an indicator of certain PFASs in atmospheric particulate.

Fluorotelomer Alcohols' Toxicology Correlates with Oxidative Stress and Metabolism

Fluorotelomer alcohols (FTOHs) are widely used as industrial raw materials due to their unique hydrophobic and oleophobic properties. However, because of accidental exposure to products containing FTOHs or with the widespread use of FTOHs, they tend to contaminate the water and the soil. There are reports demonstrating that FTOHs can cause various harmful effects in animals and humans (for example, neurotoxicity, hepatotoxicity, nephrotoxicity, immunotoxicity, endocrine-disrupting activity, and developmental and reproductive toxicities). Oxidative stress is related to a variety of toxic effects induced by FTOHs. To date, few reviews have addressed the relationship between the toxicity of FTOHs and oxidative stress. This article summarises research demonstrating that the toxicity induced by FTOHs correlates with oxidative stress and metabolism. Furthermore, during the metabolic process of FTOHs, a number of cytochrome P450 enzymes (CYP450) are involved and many metabolites are produced by these enzymes, which can induce oxidative stress. This is also reviewed.

Biotransformation and tissue bioaccumulation of 8:2 fluorotelomer alcohol in broiler by oral exposure

In order to examine whether 8:2 FTOH exposure would lead to a contamination risk of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in broiler derived food, the biotransformation, and tissue distribution and accumulation of 8:2 FTOH following oral exposure in male broilers were investigated. The main metabolites of 8:2 FTOH in plasma and six tissues (muscle, liver, kidney, fat, heart, and lungs) identified by LC-Q-TOF were 2-perfluorooctyl ethanoic acid (8:2 FTCA), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 3-perfluoroheptyl propanoic acid (7:3 FTCA), perfluoropentanoic acid (PFPeA), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluorononanoic acid (PFNA), 8:2 FTOH glucuronide conjugate, and 8:2 FTOH sulfate conjugate. The tissue distribution and bioaccumulation of 8:2 FTOH and its unconjugated metabolites were determinated by LC-MS/MS. 8:2 FTOH was quickly depleted in plasma and all six tested tissues, while PFOA, PFNA, and 7:3 FTCA showed strong accumulation in blood and all six examined tissues and were eliminated more slowly than the other metabolites. The tissues with the highest accumulation levels for 8:2 FTOH and its metabolites were heart, kidneys and liver, and the tissue with the lowest accumulation levels was muscle. The elimination half-lifes of PFNA in kidney and 7:3 FTCA in lung were longer compared to those of other metabolites in all six determined tissues. Thus, PFNA and 7:3 FTCA can be selected as potential biomonitoring markers after 8:2 FTOH exposure. This study has improved our understanding of 8:2 FTOH biotransformation and tissue bioaccumulation in broilers, which will help us monitor human exposure risk via food derived from broilers polluted by 8:2 FTOH.

Microbial Cleavage of C-F Bonds in Two C6 Per- and Polyfluorinated Compounds via Reductive Defluorination

The C-F bond is one of the strongest single bonds in nature. Although microbial reductive dehalogenation is well known for the other organohalides, no microbial reductive defluorination has been documented for perfluorinated compounds except for a single, nonreproducible study on trifluoroacetate. Here, we report on C-F bond cleavage in two C₆ per- and polyfluorinated compounds via reductive defluorination by an organohalide-respiring microbial community. The reductive defluorination was demonstrated by the release of F^- and the formation of the corresponding product when lactate was the electron donor, and the fluorinated compound was the sole electron acceptor. The major dechlorinating species in the seed culture, Dehalococcoides, were not responsible for the defluorination as no growth of Dehalococcoides or active expression of Dehalococcoides-reductive dehalogenases was observed. It suggests that minor phylogenetic groups in the community might be responsible for the reductive defluorination. These findings expand our fundamental knowledge of microbial reductive dehalogenation and warrant further studies on the enrichment, identification, and isolation of responsible microorganisms and enzymes. Given the wide use and emerging concerns of fluorinated organics (e.g., per- and polyfluoroalkyl substances), particularly the perfluorinated ones, the discovery of microbial defluorination under common anaerobic conditions may provide valuable insights into the environmental fate and potential bioremediation strategies of these notorious contaminants.

Fluorochemicals biodegradation as a potential source of trifluoroacetic acid (TFA) to the environment

The anthropogenic release of trifluoroacetic acid (TFA) into the environmental media is not limited to photochemical oxidation of CFC alternatives and industrial emissions. Biological degradation of some fluorochemicals is expected to be a potential TFA source. For the first time, we assess if the potential precursors [6:2 fluorotelomer alcohol (6:2 FTOH), 4:2 fluorotelomer alcohol (4:2 FTOH), acrinathrin, trifluralin, and 2-(trifluoromethyl)acrylic acid (TFMAA)] can be biologically degraded to TFA. Results show that 6:2 FTOH was terminally transformed to 5:3 polyfluorinated acid (5:3 FTCA; 12.5 mol%), perfluorohexanoic acid (PFHxA; 2.0 mol%), perfluoropentanoic acid (PFPeA; 1.6 mol%), perfluorobutyric acid (PFBA; 1.7 mol%), and TFA (2.3 mol%) by day 32 in the landfill soil microbial culture system. 4:2 FTOH could remove multiple -CF₂ groups by microorganisms and produce PFPeA (2.6 mol%), PFBA (17.4 mol%), TFA (7.8 mol%). We also quantified the degradation products of TFMAA as PFBA (1.3 mol%) and TFA (6.3 mol%). Furthermore, we basically analyzed the biodegradation contribution of short-chain FTOH as raw material residuals in commercial products to the TFA burden in the environmental media. We estimate global emission of 3.9-47.3 tonnes of TFA in the period from 1961 to 2019, and project 3.8-46.4 tonnes to be emitted from 2020 to 2040 via the pathway of 4:2 and 6:2 FTOH biodegradation (0.6-7.1 and 0.6-7.0 tonnes in China, respectively). Direct evidence of the experiments indicates that biodegradation of fluorochemicals is an overlooked source of TFA and there are still some unspecified mechanisms of TFA production pathways.

The Effects of Halogenated Compounds on the Anaerobic Digestion of Macroalgae

The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, unlike terrestrial plants, produce a range of halogenated secondary metabolites, especially chlorinated and brominated compounds. Some orders of brown seaweeds also accumulate iodine, up to 1.2% of their dry weight. Fluorine remains rather unusual within the chemical structure. Halogenated hydrocarbons have moderate to high toxicities. In addition, halogenated organic compounds constitute a large group of environmental chemicals due to their extensive use in industry and agriculture. In recent years, concerns over the environmental fate and release of these halogenated organic compounds have resulted in research into their biodegradation and the evidence emerging shows that many of these compounds are more easily degraded under strictly anaerobic conditions compared to aerobic biodegradation. Biosorption via seaweed has become an alternative to the existing technologies in removing these pollutants. Halogenated compounds are known inhibitors of methane production from ruminants and humanmade anaerobic digesters. The focus of this paper is reviewing the available information on the effects of halogenated organic compounds on anaerobic digestion.

Nontargeted identification of per- and polyfluoroalkyl substances in human follicular fluid and their blood-follicle transfer

The female reproductive toxicity of per- and polyfluoroalkyl substances (PFAS) has raised concerns, but knowledge about their human preconception exposure is limited. In this study, 15 emerging PFAS were identified in follicular fluid samples from healthy women by using high-resolution mass spectrometry, and Cl-substituted perfluoroalkyl ether sulfonates (Cl-PFESAs) including 4:2, 5:2, 6:2, and 8:2 Cl-PFESAs, 4:4 C₈ perfluoroalkyl ether sulfonate (PFESA), C₈ perfluoroalkyl ether carboxylate (PFECA), and C₈ polyether PFECA (Po-PFECA) were detected in over 50% of 28 follicular fluid samples. Ten legacy PFAS were also detected, and the geometric mean concentration of PFOS was the highest (4.82 ng/mL), followed by PFOA (4.60 ng/mL), 6:2 Cl-PFESA (1.09 ng/mL), PFHxS (0.515 ng/mL), PFNA (0.498 ng/mL), and C₈ PFECA (0.367 ng/mL). The blood-follicle transfer efficiencies for PFCAs decreased with increasing chain length (0.96 for PFHpA, 0.56 for PFTriDA), and the transfer efficiencies of C₈ PFECA (0.78) was significantly higher than that of PFOA (0.76). The transfer efficiencies of 4:2 Cl-PFESA (0.73), 6:2 Cl-PFESA (0.75) and 8:2 Cl-PFESA (0.91) were significantly higher than that (0.70) of PFOS (p = 0.028, 0.026 and 0.002, respectively). This study constitutes the first report of the human oocyte exposure to emerging PFAS and their blood-follicle transfer abilities.

The effect of weathering on per- and polyfluoroalkyl substances (PFASs) from durable water repellent (DWR) clothing

To assess the effects of weathering on per- and polyfluoroalkyl substances (PFASs) from durable water repellent (DWR) clothing, thirteen commercial textile samples were exposed to elevated ultra violet (UV) radiation, humidity, and temperature in an aging device for 300 h, which mimics the lifespan of outdoor clothing. Before and after aging, the textile samples were extracted and analysed for the ionic PFASs (perfluoroalkyl acids (PFAAs), perfluorooctane sulfonamide (FOSA)) and volatile PFASs (fluorotelomer alcohols (FTOHs), acrylates (FTACs) and methacrylates (FTMACs)). Results showed that weathering can have an effect on PFASs used in DWR of outdoor clothing, both on the PFAS profile and on the measured concentrations. In most weathered samples the PFAA concentrations increased by 5- to more than 100-fold, while PFAAs not detected in the original textiles were detected in the weathered samples. DWR chemistries are based on side-chain fluorinated polymers. A possible explanation for the increase in concentration of the PFAAs is hydrolysis of the fluorotelomer based polymers (FTPs), or degradation of the FTOHs, which are used in the manufacturing of the FTPs. The concentrations of volatile PFASs also increased, by a factor up to 20. Suggested explanations are the degradation of the DWR polymers, making non-extractable fluorines extractable, or the transformation or degradation of unknown precursors. Further research is needed to unravel the details of these processes and to determine the transformation routes. This study shows that setting maximum tolerance limits only for a few individual PFASs is not sufficient to control these harmful substances in outdoor clothing.

Comparison of fluorotelomer alcohol emissions from wastewater treatment plants into atmospheric and aquatic environments

Recent studies have revealed that wastewater treatment plants (WWTPs) are an important source of fluorotelomer alcohols (FTOHs) in the environment. However, it remains unclear whether volatilization to the atmosphere or discharge with wastewater effluent into receiving water bodies is the dominant pathway through which FTOHs enter the environment; it also remains unclear how the relative importance of these two emission pathways varies among seasons and homologs. Here, we estimated the emissions of 6:2 and 8:2 FTOHs through these two pathways from a typical WWTP in Beijing, China, by measuring height-dependent air concentrations above the wastewater surface; we also measured wastewater concentrations among the four annual seasons. Our results showed that atmospheric emissions dominate total annual FTOH emissions, but are not dominant in every single season. Emission to the aquatic environment is dominant during seasons with less wind (i.e., summer and fall). While the abundance of 6:2 FTOH has increased in recent years, 8:2 FTOH remains the major FTOH homolog released into the environment in China. This study provides comprehensive information regarding FTOH emissions from WWTPs to the environment and practical guidance for future monitoring practices.

Aerobic biotransformation of fluorotelomer compounds in landfill leachate-sediment

Consumer products containing fluorotelomer polymers are a source of fluorotelomer compounds to the environment following their disposal at landfills. The fate and transformation of fluorotelomer compounds are unknown in landfill leachates. This study investigates the aerobic biotransformation of 8:2 fluorotelomer alcohol (FTOH) and 6:2 fluorotelomer sulfonate (FTS) in landfill leachate-sediment microcosms using batch tests. Spiked 8:2 FTOH, 6:2 FTS and their known biotransformation products were quantified in sediment-leachate and headspace over 90 days under aerobic conditions. 8:2 FTOH and 6:2 FTS biotransformation was slow (half-life >>30 d) in landfill leachate-sediment microcosm, suggesting persistence of fluorotelomer compounds under the conditions investigated. Significant volatilization (>20%) of 8:2 FTOH was observed in the microcosm headspace after 90 days. C6 - C8 and C4 - C6 perfluorocarboxylic acids (PFCAs) were the most abundant products for 8:2 FTOH and 6:2 FTS, respectively. PFCAs accounted for 4-9 mol% of the initially spiked parent compounds at 90 days. Perfluorooctanoic acid (PFOA) was the single most abundant product of 8:2 FTOH (>2.8 mol% at 90 days). The unaccounted mass (20 to 35 mol%) of the initially spiked parent compounds indicated formation of fluorotelomer intermediates and sediment-bound residue. Overall the findings suggest that aerobic biotransformation of fluorotelomer compounds acts as a secondary source of long- and short-chain (≤C7) PFCAs in the environment. Partitioning of semi-volatile fluorotelomer compounds (e.g., 8:2 FTOH) to the gas-phase indicates possible long-range transport and subsequent release of PFCAs in pristine environments. Short-chain fluorotelomer replacements (e.g., 6:2 FTS) result in a higher abundance of short-chain PFCAs in landfill leachate. Future research is needed to understand the long-term exposure effects of short-chain PFCAs to humans, aquatic life and biota.

Formation of perfluorocarboxylic acids from 6:2 fluorotelomer sulfonate (6:2 FTS) in landfill leachate: Role of microbial communities

Fluorotelomer compounds in landfill leachate can undergo biotransformation under aerobic conditions and act as a secondary source of perfluorocarboxylic acids (PFCAs) to the environment. Very little is known about the role of various microbial communities towards fluorotelomer compounds biotransformation. Using an inoculum prepared from the sediment of a leachate collection ditch, 6:2 fluorotelomer sulfonate (6:2 FTS) biotransformation experiments were carried out. Specific substrates (i.e., glucose, ammonia) and ammonia-oxidizing inhibitor (allylthiourea) were used to produce two experimental runs with heterotrophic (HET) growth only and heterotrophic with ammonia-oxidizing and nitrite- oxidizing bacteria (HET + AOB + NOB). After 10 days, ∼20% of the spiked 6:2 FTS removal was observed in HET + AOB + NOB, compared to ∼7% under HET condition. Higher 6:2 FTS removal in HET + AOB + NOB likely resulted from ammonia monooxygenase enzyme that catalyzes the first step of ammonia oxidation. The HET + AOB + NOB condition also showed higher PFCA (C4-C6) formation (∼2% of initially spiked 6:2 FTS), possibly due to higher overall bioactivity. Microbial community analysis through 16s rRNA sequencing confirmed that Proteobacteria and Bacteroidetes were the most abundant phyla (>75% relative abundance) under all experimental conditions. High abundance of Actinobacteria (>17%) was observed under the HET + AOB + NOB condition on day 7. Since Actinobacteria can synthesize a wide range of enzymes including monooxygenases, they likely play an important role in 6:2 FTS biotransformation and PFCA production.

Spatiotemporal distribution, sources and ecological risks of perfluorinated compounds (PFCs) in the Guanlan River from the rapidly urbanizing areas of Shenzhen, China

Limited studies have demonstrated the environmental concerns of perfluorinated compounds (PFCs) in the rivers flowing through the rapidly urbanizing areas. Therefore, this study aims to investigate the spatial and temporal distribution, major sources and ecological risks of PFCs in the surface water samples, collecting from the Guanlan River, Shenzhen, China. The concentrations of ∑PFCs ranged from 11.3 to 384 ng/L, with a mean value of 81.8 ng/L in the dry season, and ranged from 6.90 to 619 ng/L, with a mean value of 339 ng/L in the wet season. Short-chain PFCs such as perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS) were detected as the predominant compounds. Further, the spatiotemporal distribution revealed significantly higher levels of PFCs in the wet season than those in the dry season, and relatively higher levels in the tributaries than those in the mainstream. Source apportionment highlighted the industrial discharges, domestic wastewater, precipitation, and wastewater treatment plants as the major sources of PFCs. Moreover, the population density and associated urban sewage emissions observed as important indicators for PFCs uneven distribution in the area. The ecological risk assessment revealed perfluorotetradecanoic acid (PFTA, C14) posed high ecological risks to the aquatic organisms (especially for mysid) in the Guanlan River. Taken all together, this study not only unveiled the characteristics of PFCs contamination in the rapidly urbanizing catchment, but also provided the baseline data for policy makers to protect the ecological environment of the urban rivers in the rapidly growing area.

Treatment train approaches for the remediation of per- and polyfluoroalkyl substances (PFAS): A critical review

Per- and polyfluoroalkyl substances (PFAS) have recently drawn great attention due to their ubiquitous presence in aquatic environments and potential toxicity to human health and the environment. A number of recent studies have demonstrated that "passive" removal approaches, such as adsorption, filtration, and reverse osmosis or "active" degradation technologies, such as enhanced photolysis, electrochemical oxidation, and sonochemical destruction, are all able to individually conduct remedial measures for PFAS contamination at some level. However, drawbacks, specifically high energy consumption, low cost-efficiency, and extreme operating conditions, are commonly observed from these studies which significantly suppress the future for commercialization of these innovative technologies. Since 2015, a new trend of PFAS remediation has emerged that uses multiple synergetic technologies simultaneously (known as treatment train processes) to effectively achieve in-situ remediation of PFAS. This paper provides new insight of the recently reported treatment train studies selected from approximately 150 different publications with regards to the remediation of PFAS and discusses their innovative designs, remediation performances, present limits, and possible improvements. Based on a comprehensive review of the current treatment train studies, this review work proposes a new design that consists of three individual technologies, namely, nanofiltration, electrochemical anodic oxidation, and electro-Fenton degradation, to maximize economic and environmental benefits of PFAS remedial measures.

A Matrix-Correction Approach to Estimate the Bioaccumulation Potential of Emerging PFASs

Recent studies employing high-resolution mass spectrometry have discovered numerous emerging per- and polyfluoroalkyl substances (PFASs) in the environment, but the lack of authentic standards for these contaminants hampers quantitative evaluation of hazard properties. Here, we tested a matrix-correction methodology for determining the bioaccumulation potential of emerging PFASs based on peak area in crucian carp from Xiaoqing river, China. Fortification experiments of emerging PFASs extracted from surface water and sediment samples demonstrated that the quantification bias in fish tissues was <34% for analytes detected in fish and water. Tissue distribution ratios (TBRs) and whole-body bioaccumulation factors (BAFs) were subsequently calculated by correcting for analyte- and tissue-specific matrix effects. A model evaluation set including seven reference PFASs demonstrated that peak area-based TBRs and BAFs were strongly correlated with those calculated from quantified concentrations (p < 0.05, adjusted r² > 0.91, slope: 0.99-1.34). Among the detected substances, the trimer acid of hexafluoropropylene oxide and C9 monoether per- and polyfluoroalkyl ether carboxylic acid (PFECA) were identified as bioaccumulative substances. C8 PFECA and C8 monochlorine-substituted perfluoroalkyl carboxylic acid displayed similar BAFs value compared to perfluorooctanoic acid. Overall, the proposed methodology provides a rapid hazard screening tool that could be used to assess emerging contaminants without access to authentic standards.

On the Ability of Perfluorohexane Sulfonate (PFHxS) Bioaccumulation by Two Pseudomonas sp. Strains Isolated from PFAS-Contaminated Environmental Matrices

PFASs (perfluoroalkyl and polyfluoroalkyl substances) are highly fluorinated, aliphatic, synthetic compounds with high thermal and chemical stability as well as unique amphiphilic properties which make them ingredients in a range of industrial processes. PFASs have attracted consideration due to their persistence, toxicity and bioaccumulation tendency in the environment. Recently, attention has begun to be addressed to shorter-chain PFASs, such as perfluorohexane sulfonate [PFHxS], apparently less toxic to and more easily eliminated from lab animals. However, short-chain PFASs represent end-products from the transformation of fluorotelomers whose biotic breakdown reactions have not been identified to date. This means that such emergent pollutants will tend to accumulate and persist in ecosystems. Since we are just learning about the interaction between short-chain PFASs and microorganisms, this study reports on the response to PFHxS of two Pseudomonas sp. strains isolated from environmental matrices contaminated by PFASs. The PFHxS bioaccumulation potential of these strains was unveiled by exploiting different physiological conditions as either axenic or mixed cultures under alkanothrofic settings. Moreover, electron microscopy revealed nonorthodox features of the bacterial cells, as a consequence of the stress caused by both organic solvents and PFHxS in the culturing substrate.

Occurrence and partitioning behavior of perfluoroalkyl acids in wastewater effluent discharging into the Long Island Sound

Perfluoroalkyl acids (PFAAs) were measured in aqueous and suspended particulate matter (SPM) fractions in the final effluents from 12 wastewater treatment facilities located around the Connecticut shoreline. Aqueous phase concentrations ranged from 53 to 198 ng/L for ∑PFAAs with ≤7 perfluorinated carbons (CF₂) and 2-73 ng/L for >7 CF₂ PFAAs. Predominant PFAAs associated with effluent derived SPM were perfluorodecanoic acid and perflurorooctane sulfonic acid, detected in 48% and 52% of samples in concentrations ranging from <LOQ-1770 ng/g and <LOQ-2750 ng/g respectively. Based on the range of concentrations detected and the average flow of final effluent to the Long Island Sound (LIS), average total annual PFAA mass loads from wastewater treatment facilities to the LIS is estimated in the range of 70-315 kg/year, with 4-100 kg/year consisting of >7 CF₂ PFAAs. Partitioning coefficients (log K_OC) derived for effluent water and SPM phases (4.2 ± 0.3, 4.4 ± 0.4, 5.1 ± 0.2 and 5.3 ± 0.2 for PFOA, PFNA PFDA and PFUnA; 4.5 ± 0.2 and 5.2 ± 0.2 for PFOS and PFHsX respectively) were found to be of similar magnitude to aeration tank particles, though 0.5 to 2 log units greater than sludge solids and to natural system particulates including riverine SPM, estuarine SPM and sediments. Results from this study suggest that effluent derived suspended particulate matter could be an effective vector in the transport of long-chained PFAAs through wastewater treatment into receiving waters, and a potential vector to the local food chain.

A pilot-scale investigation of disinfection by-product precursors and trace organic removal mechanisms in ozone-biologically activated carbon treatment for potable reuse

Although granular activated carbon (GAC) has been broadly applied in ozone-biologically activated carbon filtration (O₃/BAC) systems for potable reuse of municipal wastewater, the mechanisms of various pollutant removal remain largely unknown as the regenerated GAC develops microbial populations resulting in biofiltration but loses significant adsorption capacity as it becomes spent GAC. Therefore, pilot-scale parallel performance comparisons of spent and regenerated GAC, along with a range of pre-oxidant ozone doses, were used to shed light on the mechanisms responsible for the removal of various types of treatment byproduct precursors and trace organic compounds. It was confirmed from this pilot-study that ozone alone can effectively degrade chlorinated trihalomethane (THM) and haloacetic acid (HAA) precursors, chloramine-reactive N-nitrosodimethylamine (NDMA) precursors, and 29 PPCPs. In contrast, biodegradation by microbial population on spent or regenerated GAC can remove NDMA and 22 PPCPs, while the adsorption by regenerated GAC can remove chlorinated THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs. The results of this pilot study are intended to provide those interested in potable reuse with an example of the simultaneous removal capabilities and mechanisms that can be anticipated for treating a complex mixture of organics present in real municipal wastewater effluent.

Defluorination of perfluoroalkyl acids is followed by production of monofluorinated fatty acids

We investigated the capability of microorganisms isolated from environments polluted with perfluoroalkyl acids (PFAAs) to conduct biotransformation of these emerging pollutants. Two different microbial consortia (chemoorganoheterotrophic bacteria and total yeast and molds) were isolated from two river sediments in Saitama and Osaka, Japan, known for long term pollution with perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). The microbial consortia were incubated in the presence of added PFOS and PFOA, and decreases in concentrations of these compounds were between 46-69% and 16-36%, respectively. Decreases in concentrations were, in part, due to sorption on biomass, but defluorinated PFOS and PFOA products were not detected. However, untargeted analysis suggested the presence of several metabolites found only in samples from consortia with PFOS and PFOA but not in the control samples. Molecular formula candidates were narrowed down to two options, C₁₈H₂₈O₅F and C₂₁H₂₇O₄. It was assumed that these formulas were associated with unsaturated monofluorinated fatty acids and hydrocarbons with multiple unsaturated bonds or ring structures.

Anaerobic biodegradation of 8:2 fluorotelomer alcohol in anaerobic activated sludge: Metabolic products and pathways

The anaerobic biodegradability and metabolic pathways of 8:2 fluorotelomer alcohol (8:2 FTOH) were investigated in anaerobic activated sludge. The biodegradation was well described by a double exponential decay model. 8:2 FTOH was biodegraded to poly- and perfluorinated metabolites with the release of fluoride ion. All polyfluorinated metabolites were intermediate metabolic products and could be further transformed to other metabolites, while perfluorinated metabolites were terminal products. 2H-perfluoro-2-decenoic acid (8:2 FTUA) and perfluorooctanoic acid (PFOA) were verified as the most abundant poly- and perfluorinated metabolites, respectively. Two shorter-chain perfluorinated metabolites, perfluoropentanoic acid (PFPeA) and perfluorobutyric acid (PFBA), were first reported in the biodegradation of 8:2 FTOH. However, the total molar recovery of 8:2 FTOH decreased with increasing incubation time, indicating that there might be some unknown metabolites. Thus, the anaerobic biodegradation pathways were proposed as follows: 8:2 FTOH was oxidized to 8:2 FTUA and 2-perfluorooctyl ethanoic acid (8:2 FTCA) via 2-perfluorooctyl acetaldehyde (8:2 FTAL), and then 8:2 FTUA and 8:2 FTCA were further transformed to 1-perfluoroheptyl ethanol (7:2 sFTOH) via 3-perfluoroheptyl propionic acid (7:3 acid) or/and 3-perfluoroheptyl acrylic acid (7:3 Uacid), and eventually 7:2 sFTOH was further biodegraded to PFOA and other perfluorocarboxylates containing less than eight carbons.

Enhanced generation of perfluoroalkyl carboxylic acids (PFCAs) from fluorotelomer alcohols (FTOHs) via ammonia-oxidation process

With the phase-out of persistent, bioaccumalative, and toxic perfluoroalkyl carboxylic acids (PFCAs), it is needed to explore the potential release of PFCAs from precursors being emitted into the environment. Biotransformation of fluorotelomer alcohols (FTOHs) via biological processes in wastewater treatment plants (WWTPs) leads to discharge of PFCAs into receiving waters. However, the commonly existed microbial activity that can impact on FTOHs biodegradation in WWTPs remains unclear. The objective of present research was to explore the relationship between ammonia-oxidation process and the enhanced PFCAs generation from FTOHs biodegradation under aerobic activated sludge. The obtained results indicate that the cometabolism process performed by nitrifying microorganisms (NMs) was responsible for enhanced PFCAs generation. Among NMs, the ammonia-oxidation bacteria that can express non-specific enzyme of ammonia monooxygenases resulted in the enhanced PFCAs generation from FTOHs. Meanwhile, the different addition amount of ammonia contributed to different defluorination efficiency of FTOHs. The present study further correlated the enhanced PFCAs generation from FTOHs biodegradation with ammonia-oxidation process, which can provide practical information on effective management of PFCAs generation in WWTPs.

Effects of microbial activity on perfluorinated carboxylic acids (PFCAs) generation during aerobic biotransformation of fluorotelomer alcohols in activated sludge

Biotransformation of fluorotelomer alcohols (FTOHs) in wastewater treatment plants (WWTPs) can release toxic intermediates and perfluorinated carboxylic acids (PFCAs) to the aqueous environment. However, little information is known about the role of relevant microbial activity (i.e., autotrophs and/or heterotrophs) in biotransformation of FTOHs. Additionally, the dynamics of microbial community in sludge after exposure to FTOHs remain unclear. In the present research, using domestic and industrial WWTP sludge, we performed lab-scale batch experiments to characterize the FTOHs biodegradation property under aerobic condition. Both heterotrophs and the autotrophs were associated with FTOHs biotransformation. However, the microbial activity influenced PFCAs generation efficiency. Autotrophs based on ammonia oxidation (50mgN/L) resulted in more effective generation of PFCAs than heterotrophs based on glucose (200mgC/L) metabolism. Moreover, autotrophs generated more amounts of short-chain PFCAs (carbon number ≤7) than the heterotrophs. The ammonia monooxygenase (AMO) in ammonia oxidizing microorganisms (AOMs) are suggested as responsible for the enhanced generation of PFCAs during FTOHs biotransformation. In the sludge that had been exposed to poly- and perfluorinated alkyl substances in an industrial WWTP, Chlorobi was the predominant microorganisms (36.9%), followed by Proteobacteria (20.2%), Bacteroidetes (11.1%), Chloroflexi (6.2%), Crenarchaeota (5.6%), Planctomycetes (4.2%), and Acidobacteria (3.5%). In the present research, the dosed 8:2 FTOH (12.1mg/L) and its biotransformation products (intermediates and PFCAs) could force a shift in microbial community composition in the sludge. After 192h, Proteobacteria significantly increased and dominated. These results provide knowledge for comprehending the effects of microbial activity on FTOHs biodegradation and the information about interaction between microbial community and the exposure to FTOHs in activated sludge.