Short-chain Perfluoroalkyl Carboxylic Acids Research Articles

The effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana pipiens) tadpole development

Short-chain perfluoroalkyl carboxylic acids (PFCAs) have been detected in the environment globally. The presence and persistence of these compounds in the environment may lead to chronic wildlife exposure. We used northern leopard frog (Rana pipiens) tadpoles to investigate the chronic toxicity and the bioconcentration of two short-chain PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA). We exposed Gosner stage 25 tadpoles to PFBA and PFHxA (as individual chemicals) at nominal concentrations of 0.1, 1, 10, 100, and 1000 µg/L for 43–46 days. Tadpoles exposed to 0.1 to 100 µg/L of PFBA and PFHxA had significantly higher mean snout-to-vent lengths, mean masses, and scaled mass indexes than control tadpoles. These results indicate that exposure to short-chain PFCAs influences tadpole growth. Further investigation into the mechanism(s) causing the observed changes in tadpole growth is warranted. We observed a significantly higher proportion of males in the PFBA 1 µg/L treatment group, however further histological analyses are required to confirm visual sex identification before making concrete conclusions on the effects of PFCAs on amphibian sex ratios. PFBA concentrations in tissues were higher than PFHxA concentrations; a pattern that contrasts with previously published studies using fish, suggesting potential differences between taxa in PFBA and PFHxA bioconcentration. Bioconcentration factors were <10 L/kg wet weight, indicating low bioconcentration potential in tadpoles. Our results suggest that PFBA and PFHxA may have effects at environmentally-relevant concentrations (0.1–10 µg/L) and further investigation is required before these compounds can be deemed a “safe” alternative to their long-chain counterparts.

Background concentrations and spatial distribution of PFAS in surface waters and sediments of the greater Melbourne area, Australia

A survey of per- and polyfluoroalkyl substances (PFAS) was conducted in Melbourne, Australia to determine background concentrations in residential, industrial, municipal wastewater treatment plants, and rural land uses. Surface water and sediment samples collected from 65 sites with different catchment land uses were analysed for thirty-three PFAS. Twenty-two out of thirty-three targeted PFAS were detected, with at least one PFAS species was detected in 98% water samples and 8% sediment samples. One site was determined to have point-source pollution from an airport (surface water Σ33PFAS = 4261 ng/L) and was excluded from statistical analyses. The median Σ33PFAS concentration in surface water was 63.5 ng/L and the average was 78.6 ng/L (range < DL-526 ng/L). PFAS species with the highest median concentrations were PFBA (11.3 ng/L), PFHxA (9.2 ng/L), PFOA (8.3 ng/L), PFOS (8.0 ng/L), PFPeA (7.5 ng/L), PFHpA (3.2 ng/L), and PFHxS (2.9 ng/L).The average Σ4PFAS in sediments was 0.35 ng/g d.w. (range = <DL-6.7 ng/g) and the congeners detected were PFOS, N-MeFOSAA, N-EtFOSAA, and N-EtFOSE. Significantly higher concentrations of all PFAS were found in urban areas than rural, except for PFBA which was evenly dispersed throughout all areas. Short-chain perfluoroalkyl carboxylic acids (PFCAs), PFBA, PFPeA, PFHxA, PFHpA, and the PFSA, PFBS were evenly dispersed throughout urban and industrial areas. PFOA, PFNA, and PFDA were higher, but not significantly, in residential catchments than industrial catchments. Industrial areas had significantly higher concentrations of perfluoroalkyl sulfonic acids (PFSAs), PFPeS, PFHxS, and PFOS, and 6:2 FTS than other urbanised areas. The distribution of PFAS throughout catchment types in this study displayed similar trends to other studies including findings of PFBA in background areas. Ongoing monitoring of defined catchments is recommended to improve understanding of PFAS sources and changes in environmental profiles, and to assess the implications of its occurrence throughout the environment.

Reductive degradation mechanism of perfluorooctanoic acid (PFOA) during vacuum ultraviolet (VUV) reactions combining with sulfite and iodide

In this study, PFOA removal and defluorination were examined during vacuum ultraviolet (VUV) photolysis in the presence of sulfite and sulfite/iodide conditions. PFOA (24 μM) degradation rate constant (kobs) and defluorination amount in VUV photolysis, and VUV/sulfite, and VUV/sulfite/iodide reactions under nitrogen-purging condition were 5.50 × 10−3, 7.26 × 10−2, 1.60 × 10−1 min−1, and 34.6, 72.7, 73.9% in 6 h, respectively. When tert-butanol (t-BuOH), NO2−, and NO3− ions were added as radical scavengers, hydrated electrons (eaq−) was confirmed as the main species responsible for degrading PFOA and mediating defluorination in VUV-based reactions. While, during VUV photolysis, short-chain perfluoroalkyl carboxylic acids (PFCAs), such as PFHpA, PFHxA, PFPeA, and PFBA, were mainly produced as transformation products (TPs) by the chain-shortening mechanism, additional 14 and 15 TPs were identified in the VUV/sulfite and VUV/sulfite/iodide reactions by LC-QTOF/MS, respectively. The main degradation mechanisms in these reactions are H–F exchange (e.g., TP395 (m/z = 394.9739) and TP377 (m/z = 376.9838)), •SO3−–F exchange (TP474, m/z = 474.9323), carbon double bond formation by defluorination (e.g., TP392 (m/z = 392.9455), TP410 (m/z = 410.9355), and TP436 (m/z = 436.9347)), and H–F exchange followed by hydration reaction (TP393, m/z = 392.9773), respectively. PFOA degradation pathways were proposed for these VUV-based reactions based on the identified TPs, their time profiles, and the density functional theory (DFT). Finally, the toxicity of PFOA and its TPs produced during three reactions were assessed using ECOSAR simulation.

Molecular interactions in short-chain perfluoroalkyl carboxylic acids and aqueous solutions.

The presence of short-chain per- and polyfluoroalkyl substances in water poses a major health and environmental challenge. Here, we have performed high-energy small- and wide-angle X-ray scattering measurements on CF3[CF2]nCOOH (where n = 1, 2, 3 represents the chain length) and their aqueous solutions at 10% mole concentrations to characterize their molecular interactions at the atomic and nanometer length scales. The experimental wide-angle structure factors have been modelled using Empirical Potential Structural Refinement. The oxygen-oxygen partial X-ray pair distribution functions show that the coordination number between the hydroxyl oxygen on the acid and surrounding oxygen water molecules increases significantly with acid chain length, rising from 3.2 for n = 1 to 4.1 for n = 3. The small-angle scattering is dominated by a sharp, high-intensity peak at Q1 ∼ 0.2 Å-1 and a smaller peak at Q2 = 1.2 Å-1 for n = 3, both of which decrease with decreasing chain length. The Q2 peak is attributed to groups of adjacent non-bonded acid molecules, and Q1 has contributions from both correlations between acid molecules and water-water interactions. In all cases, the models show nanoscale aggregation occurs in the form of denser channels of winding hydrogen-bonded chains, approximately 20 water molecules in length, surrounding clusters of acid molecules. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

Long-term removal of perfluoroalkyl substances via activated carbon process for general advanced treatment purposes

Granular or powdered activated carbon (GAC/PAC) processes are installed in full-scale drinking water treatment plants (DWTPs) to reduce disinfection byproduct precursors, odor, ammonia, and pesticides. This study investigated the ability of GAC/PAC processes in 23 DWTPs to remove per- and polyfluoroalkyl substances (PFASs). In the GAC process, filter breakthrough of perfluoroalkyl carboxylic acids (PFCAs) occurred faster as the PFCA chain length is decreased. During periods of high water temperatures (20−29 °C), the effluent concentration of two short-chain PFCAs (C4 and C5) surpassed that of the influent after the throughput reached 5,000−7,500 bed volumes (equivalent to 2−3 months) due to desorption. However, such desorption was not observed during periods of low water temperatures (5−19 °C). Meanwhile, long-chain PFCAs were consistently removed, as the GAC was replaced before breakthrough became noticeable. PFAS removal deteriorated at a remarkably fast rate after a partial breakthrough of several tens of percent. Biological activated carbon was proved ineffective in removing PFASs due to its diminished adsorption capacity after long-term use. The PAC process, however, exhibited a slight decrease in PFCA residual (10%) at higher water temperatures (15−30 °C). The PAC dose required for a certain residual ratio was lower with an increase in the hydrophobicity of PFAS; C8-PFCA only required 20 mg/L of PAC for 50% removal, while C4-PFCA required a significantly higher dose of 100−700 mg/L. Consequently, the activated carbon process, which removes organic contaminants in surface water, was inadequate in removing PFASs, particularly those with short chains. Thus, it is recommended that GAC filters be replaced more frequently (within two months) for short-chain PFAS removal. Further, the adsorption performance of PAC must be enhanced.

Mechanistic Investigations of Thermal Decomposition of Perfluoroalkyl Ether Carboxylic Acids and Short-Chain Perfluoroalkyl Carboxylic Acids.

In this study, we investigated the thermal decomposition mechanisms of perfluoroalkyl ether carboxylic acids (PFECAs) and short-chain perfluoroalkyl carboxylic acids (PFCAs) that have been manufactured as replacements for phased-out per- and polyfluoroalkyl substances (PFAS). C-C, C-F, C-O, O-H, and C═C bond dissociation energies were calculated at the M06-2X/Def2-TZVP level of theory. The α-C and carboxyl-C bond dissociation energy of PFECAs declines with increasing chain length and the attachment of an electron-withdrawing trifluoromethyl (-CF3) group to the α-C. Experimental and computational results show that the thermal transformation of hexafluoropropylene oxide dimer acid to trifluoroacetic acid (TFA) occurs due to the preferential cleavage of the C-O ether bond close to the carboxyl group. This pathway produces precursors of perfluoropropionic acid (PFPeA) and TFA and is supplemented by a minor pathway (CF3CF2CF2OCFCF3COOH → CF3CF2CF2· + ·OCFCF3COOH) through which perfluorobutanoic acid (PFBA) is formed. The weakest C-C bond in PFPeA and PFBA is the one connecting the α-C and the β-C. The results support (1) the C-C scission in the perfluorinated backbone as an effective PFCA thermal decomposition mechanism and (2) the thermal recombination of radicals through which intermediates are formed. Additionally, we detected a few novel thermal decomposition products of studied PFAS.

Directly Fluorinated Containers as a Source of Perfluoroalkyl Carboxylic Acids

Direct fluorination of plastics is performed to impart chemical resistance via exposure of polyethylene to fluorine gas to produce a fluorine-modified surface layer. Leaching experiments were performed on a directly fluorinated container under various conditions and with different matrices, including foodstuffs. The average sum of per- and polyfluoroalkyl substances (PFAS) concentrations measured from extraction of a fluorinated container was 63.75 ± 13.2 ng/g plastic. Seven-day leaching experiments of fluorinated containers with water, methanol, and acetone produced sums of PFAS concentrations that ranged from 0.99 to 66.92 ng/g plastic. Leaching experiments with food matrices produced sums of PFAS concentrations ranging from 2.66 to 7.19 ng/g plastic. A subset of samples subjected to leaching at elevated temperatures generated sums of PFAS concentrations up to 830% higher. In all experiments, short-chain perfluoroalkyl carboxylic acids (PFCAs) were detected in the highest frequencies and concentrations with analyte concentration decreasing as chain length increased. An estimate for PFAS released into food ranged from 0.77 to 2.68 ng/kg body weight per week, showing ingestion of food stored in these containers could be a significant source of exposure. Based on the large number of applications where directly fluorinated containers find use, the observation of PFAS migration suggests use regulations are warranted, and future studies should explore their fate when disposed or recycled.

Phytoscreening for Per- and Polyfluoroalkyl Substances at a Contaminated Site in Germany.

The aim of this study was to perform a phytoscreening of per- and polyfluoroalkyl substances (PFAS) at a contaminated site in Germany, to investigate the applicability of this technique for PFAS contaminations. Foliage of three species, namely, white willow (Salix alba L.), black poplar (Populus nigra L.), and black alder (Alnus glutinosa L.), were sampled to evaluate seasonal and annual variations in PFAS concentrations. The results of the phytoscreening clearly indicated species and specific differences, with the highest PFAS sum concentrations ∑23 observed in October for white willow (0-1800 μg kg-1), followed by black poplar (6.7-32 μg kg-1) and black alder (0-13 μg kg-1). The bulk substances in leaves were highly mobile short-chain perfluoroalkyl carboxylic acids (PFCAs). In contrast, the PFAS composition in soil was dominated by long-chain PFCAs, perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA), as a result of the lower mobility with ∑23PFAS ranging between 0.18 and 26 μg L-1 (eluate) and between 66 and 420 μg kg-1 (solid). However, the PFAS composition in groundwater was comparable to the spectrum observed in leaves. Spatial interpolations of PFAS in groundwater and foliage correspond well and demonstrate the successful application of phytoscreening to detect and delineate the impact of the studied PFAS on groundwater.

Hydrochar coupled with iodide for efficient photodegradation of perfluorooctanoic acid and perfluorooctane sulfonic acid under ultraviolet light

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are typical emerging persistent organic pollutants that are raising concerns regarding their environmental persistence. The photodegradation of these chemicals in water can be promoted by generating hydrated electrons (eaq−). The present work demonstrates a highly efficient process combining ultraviolet (UV) radiation, hydrochar (H-BC) and KI that is capable of decomposing PFOA and PFOS. After 60 min of photolysis using this technique, 99.5 % and 94.1 % of the initial amounts of PFOA and PFOS in aqueous solution were degraded, respectively, with corresponding defluorination percentages of 87.8 % and 71.7 %, respectively. These degradation values were higher than the sum of those obtained using UV radiation with only H-BC or KI, implying a synergistic effect from the combination of H-BC and KI. This effect can be attributed to the unique structure and numerous oxygen-containing functional groups of the H-BC. This material was able to absorb PFOA and PFOS, reduce iodide oxidation products back to I−, act as an electron shuttle and shorten the diffusion distance to the target substrate. These factors all increased the probability of reactions between the contaminants and eaq−. Analyses by liquid chromatography/electrospray ionization/tandem mass spectrometry showed that short-chain perfluoroalkyl carboxylic acids with less than seven carbons were the primary degradation intermediates, suggesting that the photodegradation proceeded stepwise. These results confirmed the cooperative effect of the H-BC and iodide, leading to effective eaq− generation. This work is expected to facilitate the development of new strategies for the treatment of water systems contaminated with PFOA and PFOS.

Occurrence and implications of per and polyfluoroalkyl substances in animal feeds used in laboratory toxicity testing

The exceptional thermal and chemical stability and the amphiphilicity of per- and polyfluoroalkyl substances (PFAS) have resulted in widespread use and subsequent contamination in environmental media and biota. Concerns surrounding toxicity have led to numerous animal-based toxicity studies. Due to the ubiquity of PFAS and the low parts per trillion (ppt) health advisory levels for drinking water, several contamination elimination protocols have been implemented. In addition, it is urgently necessary to perform low-dose experiments, but due to unknown pathways for entry of unwanted PFAS, low-dose studies are extremely challenging to conduct. However, animal feed sources are a likely route that could introduce unwanted PFAS into experiments, yet investigations of PFAS in common animal feeds are lacking. Here, we report the examination of PFAS levels in eighteen different animal feeds, representing a range of diets fed to diverse taxa. We evaluated whether PFAS levels in feeds were correlated with ingredient composition (plant versus animal-based) or dietary habits of lab animals (amphibian, fish, invertebrate, mammal). PFOS, PFHxS, PFOA, and short-chain perfluoroalkyl carboxylic acids had the highest detection levels and frequencies across all samples. Different food ingredients led to different PFAS profiles. No meaningful levels of PFAS precursors were detected. We demonstrate that PFAS contamination in animal feed is pervasive. Reducing food-sourced PFAS is a critical, albeit challenging task to improve interpretability of in vivo exposures.

Electrochemical Advanced Oxidation of Perfluorooctanoic Acid: Mechanisms and Process Optimization with Kinetic Modeling.

Electrochemical advanced oxidation processes (EAOPs) are promising technologies for perfluorooctanoic acid (PFOA) degradation, but the mechanisms and preferred pathways for PFOA mineralization remain unknown. Herein, we proposed a plausible primary pathway for electrochemical PFOA mineralization using density functional theory (DFT) simulations and experiments. We neglected the unique effects of the anode surface and treated anodes as electron sinks only to acquire a general pathway. This was the essential first step toward fully revealing the primary pathway applicable to all anodes. Systematically exploring the roles of valence band holes (h+), hydroxyl radicals (HO•), and H2O, we found that h+, whose contribution was previously underestimated, dominated PFOA mineralization. Notably, the primary pathway did not generate short-chain perfluoroalkyl carboxylic acids (PFCAs), which were previously thought to be the main degradation intermediates, but generated other polyfluorinated alkyl substances (PFASs) that were rapidly degraded upon formation. Also, we developed a simplified kinetic model, which considered all of the main processes (mass transfer with electromigration included, surface adsorption/desorption, and oxidation on the anode surface), to simulate PFOA degradation in EAOPs. Our model can predict PFOA concentration profiles under various current densities, initial PFOA concentrations, and flow velocities.

Degradation and Plant Transfer Rates of Seven Fluorotelomer Precursors to Perfluoroalkyl Acids and F-53B in a Soil-Plant System with Maize (Zea mays L.).

Fluorotelomer precursors in soil constitute a reservoir for perfluoroalkyl acids (PFAAs) in the environment. In the present study, precursor degradation and transfer rates of seven fluorotelomer precursors and F-53B (chlorinated polyfluoroalkyl ether sulfonates) were investigated in pot experiments with maize plants (Zea mays L.). The degradation of fluorotelomer precursors to perfluoroalkyl carboxylic acids (PFCAs) and their uptake spectra corresponded to those of fluorotelomer alcohol (FTOH) in terms of the number of perfluorinated carbon atoms. Short-chain PFCAs were translocated into the shoots (in descending order perfluoropentanoic, perfluorobutanoic, and perfluorohexanoic acid), whereas long-chain PFCAs mainly remained in the soil. In particular, fluorotelomer phosphate diesters (diPAPs) were retained in the soil and showed the highest degradation potential including evidence of α-oxidative processes. F-53B did not degrade to PFAAs and its constituents were mainly detected in the roots with minor uptake into the shoots. The results demonstrate the important role of precursors as an entry pathway for PFCAs into the food chain.

Occurrence, distribution, and input pathways of per- and polyfluoroalkyl substances in soils near different sources in Shanghai

Per- and polyfluoroalkyl substances (PFAS) are complex emerging pollutants that are widely distributed in soils. The compositions of PFAS vary according to the emission sources. However, the soil distributions of PFAS from different sources are still poorly understood. In this study, the concentrations and compositions of 18 PFAS in soils close to potential sources (industrial areas, airports, landfills, fire stations and agricultural areas) were investigated in Shanghai. The total PFAS concentrations varied from 0.64 to 294 μg kg−1d.w.. Among the sites, the highest PFAS concentration was found near the fire station (average = 57.9 μg kg−1d.w.), followed by the industrial area (average = 8.53 μg kg−1d.w.). The detection frequencies of the 18 PFAS ranged from 47.5% to 100%. Perfluorooctanoic acid (PFOA) and perfluoroheptanoic acid (PFHpA) were detected in all samples. The detection frequencies of PFAS near the fire station were higher than those near other sources. The PFAS in soils were mainly composed of short-chain perfluoroalkyl carboxylic acids (C ≤ 8). Elevated concentrations of long-chain perfluoroalkyl carboxylic acids (C > 12) were found in industrial area. Principal component analysis revealed that long-chain PFAS had different factor loadings compared to short-chain PFAS. With the exception of agricultural soils, the correlations between individual PFAS were more positive than negative. Strong positive correlations were found within three groups of perfluoroalkyl carboxylic acids (C5–C7, C9–C12, and C14–C18), suggesting their similar inputs and transportation pathways. The PFAS in soils around the fire station were likely directly emitted from a point source. In contrast, the PFAS in soils near the other sites had multiple input pathways, including both direct emission and precursor degradation.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs’ effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 – 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs’ PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

Co-occurrence and correlations of PFASs and chlorinated volatile organic compounds (cVOCs) in subsurface in a fluorochemical industrial park: Laboratory and field investigations

Fluorochemical industrial park (FIP) represents an important source of per- and polyfluoroalkyl substances (PFASs) and chlorinated volatile organic compounds (cVOCs). Exploring the co-occurrence and correlations of PFASs and cVOCs is a key step towards the understanding their distributions in the field. In this study, perfluorooctanoic acid (PFOA) was the dominant compound in groundwater and aquifer solids, and elevated concentrations of short-chain perfluoroalkyl carboxylic acids (PFCAs) and hexafluoropropylene oxide oligomers were also detected in the field, suggesting their wide applications as substitutes for PFOA. Correlation analyses between PFASs and cVOCs suggested that cVOCs had a significant influence on the distribution and composition of PFASs in the field. In addition, the presence of cVOCs in the form of dense non-aqueous-phase organic liquids (DNAPL) affected the distribution and migration of PFASs at various depths, as evidenced by the relatively high PFASs concentrations (204 μg/L) and PFOA abundance (85.4%) in the deep aquifer, likely due to DNAPL-water interfaces sorption or partition into bulk DNAPL. The log Kd values, determined in the laboratory, were found to increase in the presence of DNAPL, especially for PFOA, with more than one time higher than those of perfluorobutanoic acid (PFBA) and hexafluoropropylene oxide dimer acid (HFPO-DA). This conclusion further demonstrated that PFOA had a higher potential to participate into DNAPL, which can migrate with DNAPL to the deep aquifer, supporting the higher abundance of PFOA in the deep aquifer mentioned above. However, the log Kd-field values of PFBA and HFPO-DA in the field were higher than that of PFOA, and no significant correlations (p > 0.05) were found between log Kd-field values and the chain-length of PFCAs at various depths, suggesting that the phenomena observed in the field are a result of composite influencing factors.

Transport and environmental risks of perfluoroalkyl acids in a large irrigation and drainage system for agricultural production.

The quality of irrigation water and drainage water is essential for local ecosystem and human health in agricultural regions. In this study, the transport analysis, source identification, and environmental risk assessment of perfluoroalkyl acids (PFAAs) were conducted in the largest irrigation area in northern China. The concentrations of the total PFAAs (ΣPFAA) ranged from 41.5 to 263ng/L in surface water, and the short-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluorooctanoic acid (PFOA), were dominant with a total contribution of 94%. Generally, the ΣPFAA levels increased from irrigation waters to drainage and receiving lake waters. PFOA showed the highest increase, with potential emission sources located in the catchment of the sub main drainage ditch D5. More PFOA (36.8kg/y) was outflowed from Ulansuhai Lake to the Yellow River than that inflowed from the Yellow River to the irrigation district (6.15kg/y). The results of a risk assessment indicated that avian wildlife living in Ulansuhai Lake were threatened by the PFOA and perfluorobutane sulfonate (PFBS) pollution. The estimated daily intakes (EDIs) of the sum of the PFOA, perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS) through aquatic food consumption for people with the different aquatic food preferences accounted for 6-42% (urban) and 4-27% (rural) of the strictest tolerant daily intake (TDI) value. The results of this study highlight the impact of local emissions of PFAS on massive irrigation and drainage systems, and ultimately, the ecosystem and human health.

Per- and Polyfluoroalkyl Substances (PFAS) in Street Sweepings.

One hundred and seventeen street sweeping samples were collected and analyzed for per- and polyfluoroalkyl substances (PFAS). Fifty-six samples were collected in one city (Gainesville, Florida) allowing for an in-depth city-wide characterization. Street sweepings from five other urban areas, (Orlando, n = 15; Key West, n = 15; Pensacola, n = 12; Tampa, n = 13; and Daytona Beach, n = 6) were analyzed to provide a city-to-city comparison of PFAS. Within our analytical workflow, 37 PFAS were quantified across all samples, while the maximum number of PFAS quantified at one site was 26. Of those PFAS quantified in Gainesville, 60% were perfluoroalkyl acids (PFAAs) and 33% were precursors to PFAA. Among the PFAAs, short-chain perfluoroalkyl carboxylic acids (PFCAs) were the dominant class representing 26% of the total PFAS by concentration. In the comparison across different urban cities, the dominant compound by concentration and frequency of detection varied; however, perfluorooctanoic acid (PFOA) and linear perfluorooctanesulfonic acid (PFOSlin) were the two PFAS that were detected the most frequently. This study documents the first-time detection of hexadecafluorosebacic acid and perfluoro-3,6,9-trioxaundecane-1,11-dioic acid within environmental samples.

Role of hydrogenated moiety in redox treatability of 6:2 fluorotelomer sulfonic acid in chrome mist suppressant solution

6:2 Fluorotelomer sulfonic acid (6:2 FTS) is used as alternative to perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) for different purposes such as chrome mist suppressant (CMS) and active ingredient in fire-fighting foams. In this study, degradability of 6:2 FTS under ultraviolet/persulfate (UV/PS) and ultraviolet/sulfite (UV/SF), which are typical technologies for advanced oxidation and reduction, were investigated respectively. Due to the hydrogenated moiety, 6:2 FTS was decomposed completely by UV/PS within 10 min, forming a mixture of short-chain perfluoroalkyl carboxylic acids with variable chain length (2-7 carbon atoms). Such oxidation products account for > 50% organofluorine of 6:2 FTS unmineralized portion. 6:2 FTS degradability under reductive UV/SF system was dramatically slowed down by the hydrogenated moiety, which lowered electron affinity and, consequently, reactivity with aqueous electron (eaq‾) produced by UV/SF. Fluorine mass balance showed that degradation intermediates were almost negligible: most of decomposed 6:2 FTS fluorine was converted to fluoride. A real 6:2 FTS-based CMS solution prepared from a commercial product was also tested. Both types of treatment were effective and in good agreement with the trends observed for tests with sole 6:2 FTS. Moreover, experimental results highlighted a remarkable amount of identifiable (like 4:2 FTS, 8:2 FTS and other per-/polyfluoroalkyl substances) and unidentifiable components in the CMS mixture. Indeed, fluoride concentration under UV/SF (73.8 mg/L) and UV/PS (44.9 mg/L) treatment were both higher than the estimated total concentration (<23 mg/L, according to 6:2 FTS concentration). Results strongly suggest that an oxidation pretreatment followed by reduction might be a better way to degrade and defluorinate 6:2 FTS and other precursors with non-fluorinated moieties, rather than employing single reduction or oxidation technology.

Atmospheric diffusion of perfluoroalkyl acids emitted from fluorochemical industry and its associated health risks

The fluorochemical industry is an important emission source of atmospheric perfluoroalkyl acids (PFAAs). In this study, air samples were collected through active high-volume air samplers coupled with Tissuquartz™ filters around a fluorochemical manufacturer, and analyzed for PFAAs levels. Perfluorooctanoic acid (PFOA) was dominant with concentrations as high as 9730 pg/m3, followed by short chain perfluoroalkyl carboxylic acids (PFCAs). The PFAAs in the air were compared to those measured in outdoor dust and rain collected in the same area. Short chain PFCAs had a greater distribution in air, while PFOA was more distributed in dust and rain. With increasing concentrations, a significant decreasing trend for PFOA was observed in rain (P < 0.05). The estimated daily intake (EDI) of PFOA via indoor air inhalation by five age groups were calculated in two scenarios, and compared to the strictest tolerable daily intake (TDI) of PFOA (≤0.63 ng/kg bw/day). Potential health risk occurred in the best-case scenario, while the EDI from the worst-case scenario was comparable to that via indoor dust ingestion, indicating a notable health risk. This suggests that in terms of PFOA exposure and health risks, air inhalation may be as important as dust ingestion. These results highlight the impacts of PFAAs emissions from the fluorochemical industry to the atmosphere and ultimately, human health.

Subacute dermal toxicity of perfluoroalkyl carboxylic acids: comparison with different carbon-chain lengths in human skin equivalents and systemic effects of perfluoroheptanoic acid in Sprague Dawley rats

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are used in various fields but raise concerns regarding human health and environmental consequences. Among PFASs, perfluorooctanoic acid (PFOA) and short-chain perfluoroalkyl carboxylic acids (SC PFCAs) are detectable in skin-contact consumer products and have dermal absorption potential. Here, we investigated the effects of dermal exposure to PFOA and SC PFCAs using in vitro and in vivo models. Human skin equivalents were topically treated with 0.25mM and 2.5mM PFOA and SC PFCAs (perfluoropentanoic acid, PFPeA; perfluorohexanoic acid, PFHxA; and perfluoroheptanoic acid, PFHpA) for 6days, and cell viability, interleukin (IL)-1α, oxidative stress markers (malondialdehyde, MDA; and 8-hydroxydeoxyguanosine, 8-OHdG), and histopathology were examined. MDA levels were significantly higher in the PFASs groups than in controls. Compared with SC PFCAs, 2.5mM PFOA caused more IL-1α (p < 0.001) release, decreased skin thickness and microscopic abnormalities. To evaluate systemic effects, Sprague Dawley (SD) rats were dermally treated with 250 and 1000mg/kg PFHpA for 2weeks and clinical and anatomic pathology were assessed. At 1000mg/kg, 83% of the rats died, with severe ulcerative dermatitis at the application site. Adverse PFHpA-treated systemic changes were observed in the kidney, liver and testes, and histopathologic lesions such as renal tubular necrosis, hepatocellular necrosis, and germ cell degeneration were seen at 250 and 1000mg/kg. Our study suggests that SC PFCAs have fewer effects on the skin than PFOA, but SC PFCAs can have adverse effects on major organs with systemic exposure at high concentrations.