Evaluation of PFO formation from the biodegradation of a fluorotelomer-based urethane polymer product in aerobic soils

Impact of tightening environmental regulations against long-chain perfluoroalkyl acids on composition of durable water repellents containing side-chain fluorinated polymers

Tightening of environmental regulations against long-chain perfluoroalkyl acids (PFAAs) since the 2000s may have led to significant increases in the occurrence of short-chain PFAAs in the environment. Understanding the impact of the regulations on composition of durable water repellents (DWRs) is imperative to guide implementation of pragmatic actions during their use and end-of-life treatment. Substantial decreases in the frequencies of detection and concentrations of long-chain PFAAs and long-chain PFAA-precursors, and substantial increases in those of short-chain PFAAs and short-chain PFAA-precursors, have been observed in the impurities and hydrolysis products of side-chain fluorinated polymers (SCFPs). Comparison of profiles among the DWRs containing fluorinated ingredients in 2011 indicated that DWRs containing C8F17- and C10F21-SCFPs were the dominant products and accounted for 90 % of the samples, whereas DWRs containing C4F9- and C6F13-SCFPs were the dominant products and accounted for 70 % of the samples collected in 2021. Tightening of the regulations have caused decreasing applications of long-chain SCFPs and increasing use of short-chain SCFPs in DWRs containing fluorinated ingredients. The ingredients of one DWR were changed from PFAS-free alternatives to short-chain SCFPs, whereas those of another DWR were changed from short-chain SCFPs to PFAS-free alternatives. The presence of unexplained extractable organic fluorine has been observed in DWRs containing fluorinated ingredients, which may be difficult to be hydrolyzed and form known compounds. A historical series of DWRs available from before and after the tightening of regulations and a multifaceted analytical technique consisting of combustion ion chromatographic and mass spectrometric approaches combined with two extraction techniques involving ultrasonic treatment and alkaline hydrolysis revealed the impact of tightening regulations on composition of DWRs.

The environmental degradability of DEMNUM, a typical PFPE polymer

The three environmental degradation tests of hydrolysis, indirect photolysis and Zahn-Wellens microbial degradation were conducted according to the OECD and the US EPA guidelines on DEMNUM, a typical linear perfluoropolyether polymer. Low mass degradation products that formed in each test were structurally characterized and indirectly quantified by liquid chromatography mass spectrometry (LC/MS) using a reference compound and an internal standard of similar structure. The degradation of the polymer was assumed to directly correlate with the appearance of lower mass species. The hydrolysis experiment at 50 °C showed the appearance of less than a dozen low mass species with increasing pH but at the negligible total estimated amount of ∼2 ppm relative to polymer. A dozen low mass perfluoro acid entities also appeared following the indirect photolysis experiment in synthetic humic water. Their maximum total amount was at ∼150 ppm relative to polymer. The largest amount of low mass species formed during the Zahn-Wellens biodegradation test amounted to only ∼80 ppm relative to polymer. The Zahn-Wellens conditions tended to produce larger low mass molecules than the ones formed under photolysis. The results from all three tests indicate that the polymer is stable and non-degradable in the environment.

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.

Per- and polyfluoroalkyl substances (PFAS) in sludge from wastewater treatment plants in Sweden - First findings of novel fluorinated copolymers in Europe including temporal analysis

Thousands of per- and polyfluoroalkyl substances (PFAS) are on the global market, while only a minor proportion is monitored regularly in the environment. Wastewater treatment plants (WWTPs) have been suggested to be a point source for PFAS to the environment due to emission of effluent and sludge. In this study, 81 PFAS including two rarely studied perfluoroalkyl sulfonamide-based (FASA) copolymers were analyzed in sludge samples to understand the usage of PFAS in the society. Sludge samples (n = 28) were collected at four WWTPs in Sweden between 2004 and 2017. The total levels of 79 measured PFAS were between 50 and 1124 ng/g d.w. All sludge samples showed detectable levels of both C8- and C4-FASA-based copolymers. The concentrations of the FASA-based copolymers were proposed to be reported in fluorinated side-chain equivalents (FSC eq.), in order to compare the levels of the copolymers with the other neutral and anionic PFAS, as no authentic standards were available. The concentrations of the FASA-based copolymers in sludge were between 1.4 and 22 ng FSC eq./g d.w. A general predomination of precursor and intermediate compounds was observed. A lower contribution of perfluoroalkyl carboxylic acids was noted for the WWTPs more influenced by domestic emission when compared with more influenced by industrial emission. An overall declining trend in the total PFAS concentration was seen between the years 2004 and 2017. The present study observed a shift from the C8-based chemistry toward shorter chain lengths, included a declining trend for C8-FASA-based copolymer over the entire study period. These findings further demonstrate the occurrence of side-chain fluorinated copolymers in Sweden and that sludge is a useful matrix to reflect the usage of PFAS in society and the potential for environmental exposure.

Depolymerizable semi-fluorinated polymers for sustainable functional materials

Chemically recyclable semi-fluorinated polymers are demonstrated for the first time, and the hydrophobicity, self-assembly, and post-polymerization functionalization of these polymers are explored.

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

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

Fate and transport of per- and polyfluoroalkyl substances (PFASs) in the vadose zone

Per- and polyfluoroalkyl substances (PFASs) are a heterogeneous group of persistent organic pollutants that have been detected in various environmental compartments around the globe. Emerging research has revealed the preferential accumulation of PFASs in shallow soil horizons, particularly at sites impacted by firefighting activities, agricultural applications, and atmospheric deposition. Once in the vadose zone, PFASs can sorb to soil, accumulate at interfaces, become volatilized, be taken up in biota, or leach to the underlying aquifer. At the same time, polyfluorinated precursor species may transform into highly recalcitrant perfluoroalkyl acids, changing their chemical identity and thus transport behavior along the way. In this review, we critically discuss the current state of the knowledge and aim to interconnect the complex processes that control the fate and transport of PFASs in the vadose zone. Furthermore, we identify key challenges and future research needs. Consequently, this review may serve as an interdisciplinary guide for the risk assessment and management of PFAS-contaminated sites.

Side-chain fluorotelomer-based polymers in children car seats

Fabric and foam samples from popular children car seats marketed in the United States during 2018 were tested for fluorine content by particle-included gamma ray emission spectroscopy (PIGE, n = 93) and X-ray photoelectron spectroscopy (XPS, n = 36), as well as for per- and polyfluoroalkyl substances (PFAS) by liquid and gas chromatography mass spectrometry (LC/MS and GC/MS, n = 36). PFAS were detected in 97% of the car seat samples analyzed with MS, with total concentrations of 43 PFAS (∑PFAS) up to 268 ng/g. Fabric samples generally had greater ∑PFAS levels than foam and laminated composites of foam and fabric. The three fabric samples with the highest total fluorine content as represented by the highest PIGE signal were also subjected to ultraviolet (UV) irradiation and the total oxidizable precursor (TOP) assay. Results from these treatments, as well as the much higher organofluorine levels measured by PIGE compared to LC/MS and GC/MS, suggested the presence of side-chain fluorotelomer-based polymers (FTPs), which have the potential to readily degrade into perfluoroalkyl acids (PFAAs) under UV light. Furthermore, fluorotelomer (meth)acrylates were found to be indicators for the presence of (meth)acrylate-linked FTPs in consumer products, and thus confirmed that at least half of the tested car seats had FTP-treated fabrics. Finally, extraction of selected samples with synthetic sweat showed that ionic PFAS, particularly those with fluorinated carbons ≤8, can migrate from fabric to sweat, suggesting a potential dermal route of exposure.

Toward a Comprehensive Global Emission Inventory of C4-C10 Perfluoroalkanesulfonic Acids (PFSAs) and Related Precursors: Focus on the Life Cycle of C8-Based Products and Ongoing Industrial Transition

Here a new global emission inventory of C₄-C₁₀ perfluoroalkanesulfonic acids (PFSAs) from the life cycle of perfluorooctanesulfonyl fluoride (POSF)-based products in 1958-2030 is presented. In particular, we substantially improve and expand the previous frameworks by incorporating missing pieces (e.g., emissions to soil through land treatment, overlooked precursors) and updating parameters (e.g., emission factors, degradation half-lives). In 1958-2015, total direct and indirect emissions of perfluorooctanesulfonic acid (PFOS) are estimated as 1228-4930 tonnes, and emissions of PFOS precursors are estimated as 1230-8738 tonnes and approximately 670 tonnes for x-perfluorooctanesulfonamides/sulfonamido ethanols (xFOSA/Es) and POSF, respectively. Most of these emissions occurred between 1958 and 2002, followed by a substantial decrease. This confirms the positive effect of the ongoing transition to phase out POSF-based products, although this transition may still require substantial time and cause substantial additional releases of PFOS (8-153 tonnes) and xFOSA/Es (4-698 tonnes) in 2016 to 2030. The modeled environmental concentrations obtained by coupling the emission inventory and a global multimedia mass-balance model generally agree well with reported field measurements, suggesting that the inventory captures the actual emissions of PFOS and xFOSA/Es for the time being despite remaining uncertainties. Our analysis of the key uncertainties and open questions of and beyond the inventory shows that, among others, degradation of side-chain fluorinated polymers in the environment and landfills can be a long-term, (potentially) substantial source of PFOS.

Degradation of Fluorotelomer-Based Polymers Contributes to the Global Occurrence of Fluorotelomer Alcohol and Perfluoroalkyl Carboxylates: A Combined Dynamic Substance Flow and Environmental Fate Modeling Analysis

Using coupled dynamic substance flow and environmental fate models, CiP-CAFE and BETR-Global, we investigated whether the degradation of side-chain fluorotelomer-based polymers (FTPs), mostly in waste stocks (i.e., landfills and dumps), serves as a long-term source of fluorotelomer alcohols (FTOHs) and perfluoroalkyl carboxylates (PFCAs) to the global environment. The modeling results indicate that, in the wake of the worldwide transition from long-chain to short-chain products, in-use stocks of C8 FTPs will peak and decline afterward, while the in-use stocks of C6 FTPs, and the waste stocks of both FTPs will generally grow. FTP degradation in waste stocks is making an increasing contribution to FTOH generation, the bulk of which readily migrates from waste stocks and degrades into PFCAs in the environment; the remaining part of the generated FTOHs degrade in waste stocks, which makes those stocks reservoirs that slowly release PFCAs into the environment over the long run because of the low leaching rate and extreme persistence of PFCAs. Short-chain FTPs have higher relative release rates of PFCAs from waste stocks than long-chain ones. Estimates of in-use and waste stocks of FTPs were more sensitive to the selected lifespan of finished products, while those of the emissions of FTOHs and PFCAs were more sensitive to the degradation half-life of FTPs in waste stocks. Our preliminary calculations highlight the need for environmentally sound management of obsolete FTP-containing products into the foreseeable future.

Uptake, Translocation, and Metabolism of 8:2 Fluorotelomer Alcohol in Soybean (Glycine max L. Merrill)

Biotransformation of fluorotelomer alcohols (FTOHs) is widely considered as an additional source of perfluorocarboxylic acids (PFCAs) in environmental biota. Compared with the extensive studies conducted in animals and microbes, biotransformation pathways of FTOHs in plants are still unclear. In this study, a hydroponic experiment was conducted to investigate the uptake, translocation and metabolism of 8:2 FTOH in soybean (Glycine max L. Merrill) over 144 h. 8:2 FTOH and its metabolites were found in all parts of soybean plants. At the end of the exposure, 7:3 FTCA [F(CF2)7CH2CH2COOH] was the primary metabolite in roots and stems, while PFOA [F(CF2)7COOH] was predominant in leaves. PFOA and 7:3 FTCA in the soybean-solution system accounted for 6.01 and 5.57 mol % of the initially applied 8:2 FTOH, respectively. Low levels of PFHpA [F(CF2)6COOH] and PFHxA [F(CF2)5COOH] in solutions and soybean roots resulted from microbial metabolism and plant root uptake. Glutathione-conjugated metabolites in soybean tissues were also identified. The activities of alcohol dehydrogenase, aldehyde dehydrogenase, and glutathione S-transferase in soybean roots increased during the exposure, suggesting their roles in 8:2 FTOH metabolism in soybean. This study provides important information for a better understanding of the uptake and metabolism of FTOHs and fluorotelomer-based compounds in plants.

Properties, performance and associated hazards of state-of-the-art durable water repellent (DWR) chemistry for textile finishing

Following the phase-out of long-chain per- and polyfluoroalkyl substances (PFASs), the textile industry had to find alternatives for side-chain fluorinated polymer based durable water repellent (DWR) chemistries that incorporated long perfluoroalkyl side chains. This phase-out and subsequent substitution with alternatives has resulted in a market where both fluorinated and non-fluorinated DWRs are available. These DWR alternatives can be divided into four broad groups that reflect their basic chemistry: side-chain fluorinated polymers, silicones, hydrocarbons and other chemistries (includes dendrimer and inorganic nanoparticle chemistries). In this critical review, the alternative DWRs are assessed with regards to their structural properties and connected performance, loss and degradation processes resulting in diffuse environmental emissions, and hazard profiles for selected emitted substances. Our review shows that there are large differences in performance between the alternative DWRs, most importantly the lack of oil repellence of non-fluorinated alternatives. It also shows that for all alternatives, impurities and/or degradation products of the DWR chemistries are diffusively emitted to the environment. Our hazard ranking suggests that hydrocarbon based DWR is the most environmentally benign, followed by silicone and side-chain fluorinated polymer-based DWR chemistries. Industrial commitments to reduce the levels of impurities in silicone based and side-chain fluorinated polymer based DWR formulations will lower the actual risks. There is a lack of information on the hazards associated with DWRs, in particular for the dendrimer and inorganic nanoparticle chemistries, and these data gaps must be filled. Until environmentally safe alternatives, which provide the required performance, are available our recommendation is to choose DWR chemistry on a case-by-case basis, always weighing the benefits connected to increased performance against the risks to the environment and human health.

Aerobic biotransformation of polyfluoroalkyl phosphate esters (PAPs) in soil

Microbial transformation of polyfluoroalkyl phosphate esters (PAPs) into perfluorocarboxylic acids (PFCAs) has recently been confirmed to occur in activated sludge and soil. However, there lacks quantitative information about the half-lives of the PAPs and their significance as the precursors to PFCAs. In the present study, the biotransformation of 6:2 and 8:2 diPAP in aerobic soil was investigated in semi-dynamics reactors using improved sample preparation methods. To develop an efficient extraction method for PAPs, six different extraction solvents were compared, and the phenomenon of solvent-enhanced hydrolysis was investigated. It was found that adding acetic acid could enhance the recoveries of the diPAPs and inhibit undesirable hydrolysis during solvent extraction of soil. However 6:2 and 8:2 monoPAPs, which are the first breakdown products from diPAPs, were found to be unstable in the six solvents tested and quickly hydrolyzed to form fluorotelomer alcohols. Therefore reliable measurement of the monoPAPs from a live soil was not achievable. The apparent DT50 values of 6:2 diPAP and 8:2 diPAP biotransformation were estimated to be 12 and > 1000 days, respectively, using a double first-order in parallel model. At the end of incubation of day 112, the major degradation products of 6:2 diPAP were 5:3 fluorotelomer carboxylic acid (5:3 acid, 9.3% by mole), perfluoropentanoic acid (PFPeA, 6.4%) and perfluorohexanoic acid (PFHxA, 6.0%). The primary product of 8:2 diPAP was perfluorooctanoic acid (PFOA, 2.1%). The approximately linear relationship between the half-lives of eleven polyfluoroalkyl and perfluoroalkyl substances (PFASs, including 6:2 and 8:2 diPAPs) that biotransform in aerobic soils and their molecular weights suggested that the molecular weight is a good indicator of the general stability of low-molecular-weight PFAS-based compounds in aerobic soils.

Aerobic biodegradation of toluene-2,4-di(8:2 fluorotelomer urethane) and hexamethylene-1,6-di(8:2 fluorotelomer urethane) monomers in soils

Aerobic soil biodegradation of toluene-2,4-di(8:2 fluorotelomer urethane) (FTU) and hexamethylene-1,6-di(8:2 fluorotelomer urethane) (HMU) in a forest soil and FTU in an agricultural silty clay loam soil was monitored for up to 6 months. Fluorotelomer alcohols were measured in headspace and parent monomers and all metabolites in soil extracts. Negligible degradation of FTU biodegradation occurred in the agricultural soil with 94 ± 15% recovered at day 180. However, in the forest soil, both FTU and HMU degradation was evident with significant losses of 24% (117 d) and 27% (180 day), respectively, and concomitant increases in the terminal metabolite, perfluorooctanoic acid (PFOA) concentrations were well above what could result from residual 8:2 FTOH. Kinetic modeling estimated half-lives for FTU (aromatic backbone) and HMU (aliphatic backbone) in the forest soil to be 3-5 months and 15.9-22.2 months, respectively. The addition of a structurally similar non-fluorinated FTU analog, toluene-2,4-dicarbamic acid diethyl ester (TDAEE) enhanced production of terminal end products from 8:2 FTOH degradation. However, there was no clear evidence that TDAEE enhanced cleavage of the urethane bond, thus TDAEE appeared to just serve as an additional carbon source. TDAEE's half-life was ∼ one week. A second addition of TDAEE appeared to retard subsequent degradation of FTU exemplifying the microbial dynamics and diversity impacting degradation of polyfluoroalkyl substances. Enhanced degradation of HMU was observed upon re-aeration indicating oxygen may have been limiting during some periods although degradation of intermediate metabolites to terminal metabolites was still occurring, albeit at slower rates.

Perfluorinated carboxylic and sulphonic acids in surface water media from the regions of Tibetan Plateau: Indirect evidence on photochemical degradation?

Perfluorinated surfactants and repellents are synthetic substances that have found numerous industrial and customer applications. Due to their persistence, at least two groups of these substances-perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs)-are diffused widely in the environment. It is hypothesized that the Tibetan Plateau, is one of few unique places on the Earth, due to its topography, specifically the vast space and high elevation above sea level, geographic location, climate, high solar radiation, lack of industry, little urbanization and general lack of significant direct sources of pollution. There it is believed possible to gain an insight into atmospheric fate (possible photochemical degradation of higher molecular mass and formation of lower molecular mass PFCAs and PFSAs) of PFASs under un-disturbed environmental conditions. Ultratrace analytical method for PFCAs and PFSAs and use of transportation and field blanks, laboratory blanks and isotopically labelled surrogates for recovery control has allowed the determination of nine perfluorinated carboxylic acids and six perfluorinated sulfonic acids at ultra-trace levels in water based samples from the alpine dimension regions of the Tibetan Plateau, the eastern slope of Minya Konka peak at the eastern edge of the Tibetan Plateau, and also from the city of Chengdu from the lowland of the Sichuan Province in China. The specific compositional pattern of PFCAs and PFSAs and low levels of pollution with those compounds were observed in the central region of the Tibetan Plateau and in the region adjacent to the peaks of Minya Konka in the Eastern Tibetan Plateau. The fingerprint of the compositional pattern of PFCAs and PFSAs in water samples in the central region of the Tibetan Plateau and in the alpine region adjacent to the peaks of Minya Konka in the Eastern Tibetan Plateau may be explained by the result of photochemical degradation with dealkylation of longer chain compounds and formation of shorter chain compounds, which are more resistant to photochemical degradation.

Microbial transformation of 8:2 fluorotelomer acrylate and methacrylate in aerobic soils

Biotransformation of fluorotelomer (FT) compounds, such as 8:2 FT alcohol (FTOH) is now recognized to be a source of perfluorooctanoic acid (PFOA) as well as other perfluoroalkyl acids. In this study, microbially mediated hydrolysis of FT industrial intermediates 8:2 FT acrylate (8:2 FTAC) and 8:2 FT methacrylate (8:2 FTMAC) was evaluated in aerobic soils for up to 105d. At designated times, triplicate microcosms were sacrificed by sampling the headspace for volatile FTOHs followed by sequential extraction of soil for the parent monomers as well as transient and terminal degradation products. Both FTAC and FTMAC were hydrolyzed at the ester linkage as evidenced by 8:2 FTOH production. 8:2 FTAC and FTMAC degraded rapidly with half-lives ⩽5d and 15d, respectively. Maximum 8:2 FTOH levels were 6-13mol% within 3-6d. Consistent with the known biotransformation pathway of 8:2 FTOH, FT carboxylic acids and perfluoroalkyl carboxylic acids were subsequently generated including up to 10.3mol% of PFOA (105d). A total mass balance (parent plus metabolites) of 50-75mol% was observed on the last sampling day. 7:2 sFTOH, a direct precursor to PFOA, unexpectedly increased throughout the incubation period. The likely, but unconfirmed, concomitant production of acrylic acids was proposed as altering expected degradation patterns. Biotransformation of 8:2 FTAC, 8:2 FTMAC, and previously reported 8:2 FT-stearate for the same soils revealed the effect of the non-fluorinated terminus group linked to the FT chain on the electronic differences that affect microbially-mediated ester cleavage rates.

Are imported consumer products an important diffuse source of PFASs to the Norwegian environment?

The aim of this study was to measure perfluoroalkyl substances in a selection of imported consumer products (n = 45) and estimate population normalized emission rates during the use phase. 6:2 and 8:2 fluorotelomer alcohol (FTOH) were found in the highest concentrations ranging from <MDL to 374 and 163 μg m(-2) respectively. Concentrations of FTOHs were approximately 2-3 orders of magnitude higher than those of perfluoroalkyl carboxylic acids (PFCAs). Although perfluorooctane sulfonate (PFOS) was detected in one carpet sample at 1.7 μg m(-2), the majority of samples complied with regulatory limits for PFOS in the EU. Population normalized emission rates of perfluorooctanoic acid, 6:2 FTOH and 8:2 FTOH from imported consumer products were estimated to be 6.6, 2130 and 197 μg year(-1) capita(-1) respectively for the "intermediate" emission scenario. The results from this study suggest that emissions from imported products would have a small impact on the environmental concentrations of perfluoroalkyl acids on a regional scale.

Decades-scale degradation of commercial, side-chain, fluorotelomer-based polymers in soils and water

Fluorotelomer-based polymers (FTPs) are the primary product of the fluorotelomer industry. Here we report on a 376-day study of the degradability of two commercial acrylate-linked FTPs in four saturated soils and in water. Using an exhaustive serial extraction, we report GC/MS and LC/MS/MS results for 50 species including fluorotelomer alcohols and acids, and perfluorocarboxylates. Modeling of seven sampling rounds, each consisting of ≥5 replicate microcosm treatments, for one commercial FTP in one soil yielded half-life estimates of 65–112 years and, when the other commercial FTP and soils were evaluated, the estimated half-lives ranged from 33 to 112 years. Experimental controls, consisting of commercial FTP in water, degraded roughly at the same rate as in soil. A follow-up experiment, with commercial FTP in pH 10 water, degraded roughly 10-fold faster than the circum-neutral control suggesting that commercial FTPs can undergo OH–-mediated hydrolysis. 8:2Fluorotelomer alcohol generated from FTP degradation in soil was more stable than without FTP present suggesting a clathrate guest–host association with the FTP. To our knowledge, these are the only degradability-test results for commercial FTPs that have been generated using exhaustive extraction procedures. They unambiguously show that commercial FTPs, the primary product of the fluorotelomer industry, are a source of fluorotelomer and perfluorinated compounds to the environment.

Investigating the biodegradability of a fluorotelomer-based acrylate polymer in a soil-plant microcosm by indirect and direct analysis

Fluorotelomer-based acrylate polymers (FTACPs) are a class of side-chain fluorinated polymers used for a variety of commercial applications. The degradation of FTACPs through ester hydrolysis, cleavage of the polymer backbone, or both could serve as a significant source of perfluoroalkyl carboxylates (PFCAs). The biodegradation of FTACPs was evaluated in a soil-plant microcosm over 5.5 months in the absence/presence of wastewater treatment plant (WWTP) biosolids using a unique FTACP determined to be a homopolymer of 8:2 fluorotelomer acrylate (8:2 FTAC). Although structurally different from commercial FTACPs, the unique FTACP possesses 8:2 fluorotelomer side chain appendages bound to the polymer backbone via ester moieties. Liberation and subsequent biodegradation of the 8:2 fluorotelomer appendages was indirectly determined by monitoring for PFCAs of varying chain lengths (C6-C9) and known fluorotelomer intermediates by liquid chromatography tandem mass spectrometry (LC-MS/MS). A FTACP biodegradation half-life range of 8-111 years was inferred from the 8:2 fluorotelomer alcohol (8:2 FTOH) equivalent of the unique FTACP and the increase of degradation products. The progress of FTACP biodegradation was also directly monitored qualitatively using matrix-assisted laser desorption/ionization (MALDI-TOF) time-of-flight mass spectrometry. The combination of indirect and direct analysis indicated that the model FTACP biodegraded predominantly to perfluorooctanoate (PFOA) in soils and at a significantly higher rate in the presence of a plant and WWTP biosolids.

Investigation of waste incineration of fluorotelomer-based polymers as a potential source of PFOA in the environment

In light of the widespread presence of perfluorooctanoic acid (PFOA) in the environment, a comprehensive laboratory-scale study has developed data requested by the U.S. Environmental Protection Agency (EPA) to determine whether municipal and/or medical waste incineration of commercial fluorotelomer-based polymers (FTBPs) at end of life is a potential source of PFOA that may contribute to environmental and human exposures. The study was divided into two phases (I and II) and conducted in accordance with EPA Good Laboratory Practices (GLPs) as described in the quality assurance project plan (QAPP) for each phase. Phase I testing determined that the PFOA transport efficiency across the thermal reactor system to be used in Phase II was greater than 90%. Operating at 1000°C over 2s residence time with 3.2-6.6mgdscm(-1) hydrogen fluoride (HF), corrected to 7% oxygen (O2), and continuously monitored exhaust oxygen of 13%, Phase II testing of the FTBP composites in this thermal reactor system yielded results demonstrating that waste incineration of fluorotelomer-based polymers does not result in the formation of detectable levels of PFOA under conditions representative of typical municipal waste combustor (MWC) and medical waste incinerator (MWI) operations in the U.S. Therefore, waste incineration of these polymers is not expected to be a source of PFOA in the environment.

Global emission inventories for C4-C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, Part I: production and emissions from quantifiable sources

We quantify global emissions of C4-C14 perfluoroalkyl carboxylic acid (PFCA) homologues during the life-cycle of products based on perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctane sulfonyl fluoride (POSF), and fluorotelomer compounds. We estimate emissions of 2610-21400 tonnes of C4-C14 PFCAs in the period from 1951 to 2015, and project 20-6420 tonnes to be emitted from 2016 to 2030. The global annual emissions steadily increased in the period 1951-2002, followed by a decrease and then another increase in the period 2002-2012. Releases from fluoropolymer production contributed most to historical PFCA emissions (e.g. 55-83% in 1951-2002). Since 2002, there has been a geographical shift of industrial sources (particularly fluoropolymer production sites) from North America, Europe and Japan to emerging Asian economies, especially China. Sources differ between PFCA homologues, sometimes considerably, and the relative contributions of each source change over time. For example, whereas 98-100% of historical (1951-2002) PFOA emissions are attributed to direct releases during the life-cycle of products containing PFOA as ingredients or impurities, a much higher historical contribution from PFCA precursor degradation is estimated for some other homologues (e.g. 9-78% for PFDA). We address the uncertainties of the PFCA emissions by defining a lower and a higher emission scenario, which differ by approximately a factor of eight.

Global emission inventories for C4-C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, part II: the remaining pieces of the puzzle

We identify eleven emission sources of perfluoroalkyl carboxylic acids (PFCAs) that have not been discussed in the past. These sources can be divided into three groups: [i] PFCAs released as ingredients or impurities, e.g., historical and current use of perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA) and their derivatives; [ii] PFCAs formed as degradation products, e.g., atmospheric degradation of some hydrofluorocarbons (HFCs) and hydrofluoroethers (HFEs); and [iii] sources from which PFCAs are released as both impurities and degradation products, e.g., historical and current use of perfluorobutane sulfonyl fluoride (PBSF)- and perfluorohexane sulfonyl fluoride (PHxSF)-based products. Available information confirms that these sources were active in the past or are still active today, but due to a lack of information, it is not yet possible to quantify emissions from these sources. However, our review of the available information on these sources shows that some of the sources may have been significant in the past (e.g., the historical use of PFBA-, PFHxA-, PBSF- and PHxSF-based products), whereas others can be significant in the long-term (e.g., (bio)degradation of various side-chain fluorinated polymers where PFCA precursors are chemically bound to the backbone). In addition, we summarize critical knowledge and data gaps regarding these sources as a basis for future research.

Characterizing fluorotelomer and polyfluoroalkyl substances in new and aged fluorotelomer-based polymers for degradation studies with GC/MS and LC/MS/MS

Fluorotelomer-based polymers (FTPs), the dominant product of the fluorotelomer industry, are antistaining and antiwetting agents that permeate the products and surfaces of modern society. However, the degree to which these materials expose humans and the environment to fluorotelomer and perfluorinated compounds, including recalcitrant and toxic compounds such as perfluorooctanoic acid (PFOA), is ill-defined. The design intent of FTPs, to minimize interaction with other substances, including solvents, heretofore has stymied efforts to develop robust methods to characterize the content of monomers and associated compounds of new commercial FTPs, as well as commercial FTPs that have been aged in environmental media for degradation testing. Here we show that FTPs can be exhausted of these compounds and quantitated by (i) drying the FTP on a suitable substrate at elevated temperature to achieve low, constant monomer concentrations; (ii) serial extraction with MTBE for fluorotelomer-monomer analysis by GC/MS in PCI mode; followed by (iii) serial extraction with 90/10 ACN/H2O for polyfluorocompound analysis by LC/MS/MS in negative ESI mode. This approach yields exhaustive, internally consistent accounting of monomers and associated compounds for FTPs, either alone or in a soil matrix (representing an environmental medium), for both new and simulated-aged FTPs to allow degradation testing, and for fluorinated compounds at least as long as C12.

Biotransformation pathways of fluorotelomer-based polyfluoroalkyl substances: a review

The study reviews the current state of knowledge regarding the biotransformation of fluorotelomer-based compounds, with a focus on compounds that ultimately degrade to form perfluoroalkyl carboxylates (PFCAs). Most metabolism studies have been performed with either microbial systems or rats and mice, and comparatively few studies have used fish models. Furthermore, biotransformation studies thus far have predominately used the 8:2 fluorotelomer alcohol (FTOH) as the substrate. However, there have been an increasing number of studies investigating 6:2 FTOH biotransformation as a result of industry's transition to shorter-chain fluorotelomer chemistry. Studies with the 8:2 FTOH metabolism universally show the formation of perfluorooctanoate (PFOA) and, to a smaller fraction, perfluorononanoate (PFNA) and lower-chain-length PFCAs. In general, the overall yield of PFOA is low, presumably because of the multiple branches in the biotransformation pathways, including conjugation reactions in animal systems. There have been a few studies of non-FTOH biotransformation, which include polyfluoroalkyl phosphates (PAPs), 8:2 fluorotelomer acrylate (8:2 FTAC), and fluorotelomer carboxylates (FTCAs, FTUCAs). The PAPs compounds and 8:2 FTAC were shown to be direct precursors to FTOHs and thus follow similar degradation pathways.

Microbial degradation of polyfluoroalkyl chemicals in the environment: a review

Polyfluoroalkyl chemicals containing perfluoroalkyl moieties have been widely used in numerous industrial and commercial applications. Many polyfluoroalkyl chemicals are potential perfluoroalkyl acid (PFAA) precursors. When they are released to the environment, abiotic and microbial degradation of non-fluorinated functionalities, polyfluoroalkyl and perfluoroalkyl moieties can result in perfluoroalkyl carboxylic (PFCAs) and sulfonic acids (PFSAs), such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). These highly persistent and ubiquitously detected PFAAs are the subjects of many regulations and actions due to their toxic profiles. In order to confidently evaluate the environmental fate and effects of these precursors and their links to PFSAs and PFCAs, we present the review into the environmental biodegradability studies carried out with microbial culture, activated sludge, soil and sediment in the past decade. First, we propose that the knowledge gap caused by the lack of direct detection of precursor chemicals in environmental samples can be bridged by laboratory investigations of important precursors such as fluorotelomer-based compounds and perfluoroalkane sulfonamido derivatives. Then we evaluate the experimental setups and methodologies, sampling and sample preparation methods, and analytical techniques that have been successfully applied. Third, we provide the most updated knowledge on quantitative and qualitative relationships between precursors and PFSAs or PFCAs, microbial degradation pathways, half-lives of precursors, defluorination potential, and novel degradation intermediates and products. In the end, we identify knowledge gaps and suggest research directions with regard to future biodegradation studies, environmental monitoring and ecotoxicological assessment of perfluoroalkyl and polyfluoroalkyl chemicals.

Aerobic soil biotransformation of 6:2 fluorotelomer iodide

6:2 FTI [F(CF2)6CH2CH2I] is a principal industrial raw material used to manufacture 6:2 FTOH [F(CF2)6CH2CH2OH] and 6:2 FTOH-based products and could enter aerobic environments from possible industrial emissions where it is manufactured. This is the first study to assess 6:2 FTI aerobic soil biotransformation, quantify transformation products, and elucidate its biotransformation pathways. 6:2 FTI biotransformation led to 6:2 FTOH as a key intermediate, which was subsequently biotransformed to other significant transformation products, including PFPeA [F(CF2)4COOH, 20 mol % at day 91], 5:3 acid [F(CF2)5CH2CH2COOH, 16 mol %], PFHxA [F(CF2)5COOH, 3.8 mol %], and 4:3 acid [F(CF2)4CH2CH2COOH, 3.0 mol %]. 6:2 FTI biotransformation also led to a significant level of PFHpA [F(CF2)6COOH, 16 mol % at day 91], perhaps via another putative intermediate, 6:2 FTUI [F(CF2)6CH ═ CHI], whose molecular identity and further biotransformation were not verified because of the lack of an authentic standard. Total recovery of the aforementioned per- and polyfluorocarboxylates accounted for 59 mol % of initially applied 6:2 FTI by day 91, in comparison to 56 mol % when soil was dosed with 6:2 FTOH, which did not lead to PFHpA. Thus, were 6:2 FTI to be released from its manufacture and undergo soil microbial biotransformation, it could form PFPeA, PFHpA, PFHxA, 5:3 acid, and 4:3 acid in the environment.

Oxidative conversion as a means of detecting precursors to perfluoroalkyl acids in urban runoff

A new method was developed to quantify concentrations of difficult-to-measure and unidentified precursors of perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acids in urban runoff. Samples were exposed to hydroxyl radicals generated by thermolysis of persulfate under basic pH conditions and perfluoroalkyl acid (PFAA) precursors were transformed to PFCAs of related perfluorinated chain length. By comparing PFCA concentrations before and after oxidation, the concentrations of total PFAA precursors were inferred. Analysis of 33 urban runoff samples collected from locations around the San Francisco Bay, CA indicated that PFOS (2.6-26 ng/L), PFOA (2.1-16 ng/L), and PFHxA (0.9-9.7 ng/L) were the predominant perfluorinated compounds detected prior to sample treatment. Following oxidative treatment, the total concentrations of PFCAs with 5-12 membered perfluoroalkyl chains increased by a median of 69%, or between 2.8 and 56 ng/L. Precursors that produced PFHxA and PFPeA upon oxidation were more prevalent in runoff samples than those that produced PFOA, despite lower concentrations of their corresponding perfluorinated acids prior to oxidation. Direct measurements of several common precursors to PFOS and PFOA (e.g., perfluorooctanesulfonamide and 8:2 fluorotelomer sulfonate) accounted for less than 25% of the observed increase in PFOA, which increased by a median value of 37%. Exposure of urban runoff to sunlight, advanced oxidation processes, or microbes could result in modest, but measurable, increases in concentrations of PFCAs and PFSAs.

Relationship between industrial discharges and contamination of raw water resources by perfluorinated compounds: part II: Case study of a fluorotelomer polymer manufacturing plant

In this study, the concentrations of 10 perfluorinated compounds (PFCs) were measured in effluents of a fluorotelomer polymer manufacturing plant and its wastewater treatment plant. A 50-fold increase between the two effluents mass flows was observed. The water quality of two drinking water treatment plants located downstream at 15 and 25 km from the manufacturing plant was examined. An increase of the sum of PFCs was observed between the river (30 ng/L) and an alluvial well (70 ng/L), and between the raw water (9 ng/L) and the outlet of a biological treatment (97 ng/L). These results indicate a possible degradation of fluorotelomers, occurring during wastewater treatment, sediment infiltration in the alluvial aquifer, and drinking water treatment.

Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins

The primary aim of this article is to provide an overview of perfluoroalkyl and polyfluoroalkyl substances (PFASs) detected in the environment, wildlife, and humans, and recommend clear, specific, and descriptive terminology, names, and acronyms for PFASs. The overarching objective is to unify and harmonize communication on PFASs by offering terminology for use by the global scientific, regulatory, and industrial communities. A particular emphasis is placed on long-chain perfluoroalkyl acids, substances related to the long-chain perfluoroalkyl acids, and substances intended as alternatives to the use of the long-chain perfluoroalkyl acids or their precursors. First, we define PFASs, classify them into various families, and recommend a pragmatic set of common names and acronyms for both the families and their individual members. Terminology related to fluorinated polymers is an important aspect of our classification. Second, we provide a brief description of the 2 main production processes, electrochemical fluorination and telomerization, used for introducing perfluoroalkyl moieties into organic compounds, and we specify the types of byproducts (isomers and homologues) likely to arise in these processes. Third, we show how the principal families of PFASs are interrelated as industrial, environmental, or metabolic precursors or transformation products of one another. We pay particular attention to those PFASs that have the potential to be converted, by abiotic or biotic environmental processes or by human metabolism, into long-chain perfluoroalkyl carboxylic or sulfonic acids, which are currently the focus of regulatory action. The Supplemental Data lists 42 families and subfamilies of PFASs and 268 selected individual compounds, providing recommended names and acronyms, and structural formulas, as well as Chemical Abstracts Service registry numbers.

Biology of fluoro-organic compounds

Investigations on diverse aspects of fluoro-organic compounds have rapidly increased during the past decades. Because natural sources of fluoro-organic compounds are extremely rare, the industrial synthesis of fluorinated organic compounds and production of fluorinated natural product derivatives have greatly expanded in recent years because of their increasing importance in the agrochemical and pharmaceutical industries. Due to structural complexity or instability, synthetic modification is often not possible, and various biofluorination strategies have been developed in recent years for applications in the anti-cancer, anti-viral and anti-infection fields. Despite the industrial importance of fluorinated compounds, there have been serious concerns worldwide over the levels and synthetic routes of certain fluorinated organic compounds, in particular perfluorinated chemicals (PFCs). PFCs are emerging and recalcitrant pollutants which are widely distributed in the environment and have been detected in humans and wildlife globally. PFCs have been demonstrated to be potentially carcinogenic, adversely affect the neuroendocrine and immune systems, and produce neurotoxicity, heptatotoxicity and endocrine disrupting effects in vertebrate animals. Here, we provide an overview of recent advances in our understanding of the biology of various fluoro-organic compounds and perspectives for new enzymes and metabolic pathways for bioremediation of these chemicals.

Concentrations, distribution, and persistence of fluorotelomer alcohols in sludge-applied soils near Decatur, Alabama, USA

Soil samples were collected for fluorotelomer alcohol (FTOH) analyses from six fields to which sludge had been applied and one "background" field that had not received sludge. Ten analytes in soil extracts were quantified using GC/MS. Sludge-applied fields had surface soil FTOH concentrations exceeding levels found in the background field. For 8:2nFTOH, which can degrade to perfluorooctanoic acid, impacted surface-soils ranged from 5 to 73 ng/g dry weight, clearly exceeding the background field in which 8:2nFTOH was not detected. The highest [FTOH] generally was 10:2nFTOH, which had concentrations of <5.6 to 166 ng/g. For the first time, we document the persistence of straight-chained primary FTOHs (n-FTOHs) and branch-chained secondary FTOHs (sec-FTOHs), which are transformation products of n-FTOHs, in field soils for at least five years after sludge application. Ratios of sec-FTOHs to n-FTOHs were highest for 7:2sFTOH/8:2nFTOH (∼50%) and decreased with increasing chain length to a minimum for the longest-chained analytes, 13:2sFTOH/14:2nFTOH (∼10%). Disappearance half-lives for FTOHs, calculated with these data, ranged from 0.85 to 1.8 years. These analytical results show that the practice of sludge application to land is a pathway for the introduction of FTOHs and, accordingly, their transformation products, perfluorocarboxylic acids, into the environment.

PFOS or PreFOS? Are perfluorooctane sulfonate precursors (PreFOS) important determinants of human and environmental perfluorooctane sulfonate (PFOS) exposure?

The extent to which perfluorooctanesulfonate precursors (PreFOS) play a role in human or environmental exposure to perfluorooctanesulfonate (PFOS) is not well characterized. The diversity of manufactured PreFOS and its degradation products (e.g. C(8)F(17)SO(2)R and C(8)F(17)SO(2)NR'R'', where R is H or F, and R' and R'' are various) has made it difficult to track their fate. Temporal trends of PFOS in both humans and wildlife are discrepant, thus it is difficult to predict future exposure, and hypotheses about the role of PreFOS have been raised. Although abiotic degradation of commercially important PreFOS materials requires further research, current data suggest that the yield of PFOS is negligible or minor. On the other hand, in vivo biotransformation of PreFOS yields PFOS as the major metabolite, and >32% yields have been observed. In Canadians, exposure to PreFOS was equivalent or greater than direct PFOS exposure prior to 2002. In most ocean water, PFOS is dominant to PreFOS, but in the oceans east of Greenland there may be more PreFOS than PFOS, consistent with the fact that whales and humans in this region also show evidence of substantial PreFOS exposure. Quantitative assessments of PFOS body-burdens coming from PreFOS are complicated by the fact that PreFOS partitions to the cellular fraction of blood, thus biomonitoring in serum under predicts PreFOS relative to PFOS. Many unknowns exist that prevent accurate modelling, thus analytical methods that can distinguish directly manufactured PFOS, from PFOS that has been biotransformed from PreFOS, should be applied in future human and environmental monitoring. Two new source tracking principles are presented and applied to human serum.

Aerobic biodegradation of [14C] 6:2 fluorotelomer alcohol in a flow-through soil incubation system

The aerobic biodegradation of [1,2-(14)C] 6:2 FTOH [F(CF(2))(6)(14)CH(2)(14)CH(2)OH] in a flow-through soil incubation system is described. Soil samples dosed with [1,2-(14)C] 6:2 FTOH were analyzed by liquid scintillation counting, LC/ARC (liquid chromatography/accurate radioisotope counting), LC/MS/MS, and thermal combustion to account for 6:2 FTOH and its transformation products over 84 d. Half of the [1,2-(14)C] 6:2 FTOH disappeared from soil in 1.3 d, undergoing simultaneous microbial degradation and partitioning of volatile transformation product(s) and the 6:2 FTOH precursor into the air phase. The overall (14)C (radioactivity) mass balance in live and sterile treatments was 77-87% over 84-d incubation. In the live test system, 36% of total (14)C dosed was captured in the airflow (headspace), 25% as soil-bound residues recovered via thermal combustion, and 16% as soil extractable. After 84 d, [(14)C] 5:2 sFTOH [F(CF(2))(5)CH(OH)(14)CH(3)] was the dominant transformation product with 16% molar yield and primarily detected in the airflow. The airflow also contained [1,2-(14)C] 6:2 FTOH and (14)CO(2) at 14% and 6% of total (14)C dosed, respectively. The other significant stable transformation products, all detected in soil, were 5:3 acid [F(CF(2))(5)CH(2)CH(2)COOH, 12%], PFHxA [F(CF(2))(5)COOH, 4.5%] and PFPeA [F(CF(2))(4)COOH, 4.2%]. Soil-bound residues as well as conjugates between fluorinated transformation products and dissolved soil components were only observed in the live test system and absent in the sterile soil, suggesting that such binding and complexation are microbially or enzymatically driven processes. At day 84, 5:3 acid is postulated to be the major transformation product in soil-bound residues, which may not be available for further biodegradation in soil environment.