Characterizing direct emissions of perfluoroalkyl substances from ongoing fluoropolymer production sources: A spatial trend study of Xiaoqing River, China

Legacy and alternative per- and polyfluoroalkyl substances spatiotemporal distribution in China: Human exposure, environmental media, and risk assessment

In recent decades, China's rapid development has led to significant environmental pollution from the widespread use of chemical products. Per- and polyfluoroalkyl substances (PFAS) are among the most concerning pollutants due to their persistence and bioaccumulation. This article assesses PFAS exposure levels, distribution, and health risks in Chinese blood, environment, and food. Out of 4037 papers retrieved from November 2022 to December 31, 2023, 351 articles met the criteria. Findings show perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) as the main PFAS in both Chinese populations and the environment. The highest PFOA levels in Chinese populations were in Shandong (53.868 ng/mL), while Hubei had the highest PFOS levels (43.874 ng/mL). Similarly, water samples from Sichuan (2115.204 ng/L) and Jiangsu (368.134 ng/L) had the highest PFOA and PFOS levels, respectively. Although localized areas showed high PFAS concentrations. Additionally, developed areas had higher PFAS contamination. The researches conducted in areas such as Qinghai and Hainan remain limited, underscoring the imperative for further investigation. Temporal analysis indicates declining levels of some PFAS, but emerging alternatives require more research. Limited studies on PFAS concentrations in soil, atmosphere, and food emphasize the need for comprehensive research to mitigate human exposure.

Intense Turbulent Bursts Promote the Release of Perfluoroalkyl Acids from Sediments at High Flow Velocity

Despite frequent detection of high levels of perfluoroalkyl acids (PFAAs) in sediments, research on the environmental fate of PFAAs in sediments, particularly under hydrodynamic conditions, is rather limited, challenging effective management of PFAA loadings. Therefore, this study investigated the release and transport of 15 PFAAs in sediments under environmentally relevant flow velocities using recirculating flumes and revealed the underlying release mechanisms by identifying related momentum transfer. An increased velocity enhanced the release magnitude of total PFAAs by a factor of 3.09. The release capacity of short-chain PFAAs was notably higher than that of long-chain PFAAs, and this pattern was further amplified by flow velocity. Pore-water drainage was the major pathway for PFAA release, with the release amount predominantly determined by flow velocity-induced release intensity and depth, as well as affected by the perfluorocarbon chain length and sediment size. The weak anion exchanger-diffusion gradients in the thin-film technique confirmed that the release depth of PFAAs increased with flow velocity. Quadrant analysis revealed that the rise in the frequency and intensity of turbulent bursts driven by sweeps and ejections at high flow velocity was the underlying cause of the increased release magnitude and depth of PFAAs.

Per- and polyfluoroalkyl substances (PFASs) in bivalve molluscs from Shandong Province, China: Occurrence, distribution, and implications for human consumption

We examined the occurrence and levels of 19 legacy and emerging per- and polyfluoroalkyl substances (PFASs) in 7 species of marine bivalve molluscs collected from four coastal cities of Shandong Province, China. Perfluorooctanoic acid (PFOA) was the most prevalent component, accounting for 68.1 % of total PFASs. The total PFASs in bivalve molluscs ranged from 0.86 to 6.55 ng/g wet weight, with the highest concentration found in Meretrix meretrix L. The concentration of total PFASs in bivalve molluscs showed the following trend: clams > scallops > oysters > mussels. Estimation on the human intake of PFASs from consumption of bivalve molluscs resulted in hazard ratios (HR) ranging from 0.12 to 6.40. Five of the seven species had HR >1, indicating high exposure risks associated with PFASs. Therefore, the occurrence of PFASs in marine biota is particularly concerning and further investigations on the sources of PFASs in Shandong are warranted.

Constraining global transport of perfluoroalkyl acids on sea spray aerosol using field measurements

Perfluoroalkyl acids (PFAAs) are highly persistent anthropogenic pollutants that have been detected in the global oceans. Our previous laboratory studies demonstrated that PFAAs in seawater are remobilized to the air in sea spray aerosols (SSAs). Here, we conducted field experiments along a north-south transect of the Atlantic Ocean to study the enrichment of PFAAs in SSA. We show that in some cases PFAAs were enriched >100,000 times in the SSA relative to seawater concentrations. On the basis of the results of the field experiments, we estimate that the secondary emission of certain PFAAs from the global oceans via SSA emission is comparable to or greater than estimates for the other known global sources of PFAAs to the atmosphere from manufacturing emissions and precursor degradation.

Per- and polyfluoroalkyl substances (PFASs) in Chinese surface water: Temporal trends and geographical distribution

PFAS, recognized as persistent organic pollutants, present risks to both the ecological environment and human health. Studying PFASs in surface water yields insights into pollution dynamics. However, existing research on PFASs surface water pollution in China often focuses on specific regions, lacking comprehensive nationwide analyses. This study examined 48 research papers covering PFAS pollution in Chinese surface water, involving 49 regions and 1338 sampling sites. The results indicate widespread PFAS contamination, even in regions like Tibet. Predominant PFAS types include PFOA and PFOS, and pollution is associated with the relocation of industries from developed to developing countries post-2010. The shift from long-chain to short-chain PFASs aligns with recent environmental policy proposals. Geographic concentration of PFAS pollution correlates with industry distribution and economic development levels. Addressing point source pollution, especially from wastewater plant tailwater, is crucial for combating PFAS contamination. Greater emphasis should be placed on addressing short-chain PFASs.

Legacy and alternative per-and polyfluoroalkyl substances (PFASs) in the Bohai Bay Rim: Occurrence, partitioning behavior, risk assessment, and emission scenario analysis

The use of alternative per- and polyfluoroalkyl substances (PFASs) has been practiced because of the restrictions on legacy PFASs. However, knowledge gaps exist on the ecological risks of alternatives and relationships between restrictions and emissions. This study systematically analyzed the occurrence characteristics, water-sediment partitioning behaviors, ecological risks, and emissions of legacy and alternative PFASs in the Bohai Bay Rim (BBR). The mean concentration of total PFASs was 46.105 ng/L in surface water and 6.125 ng/g dry weight (dw) in sediments. As an alternative for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (GenX) had a concentration second only to PFOA in surface water. In sediments, perfluorobutyric acid (PFBA) and GenX were the two predominant contaminants. In the water-sediment partitioning system, GenX, 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (F-53B), and 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (8:2 Cl-PFESA) tended to be enriched towards sediments. The species sensitivity distribution (SSD) models revealed the low ecological risks of PFASs and their alternatives in the BBR. Moreover, predicted no-effected concentrations (PNECs) indicated that short-chain alternatives like PFBA and perfluorobutane sulfonate (PFBS) were safer for aquatic ecosystems, while caution should be exercised when using GenX and F-53B. Due to the incremental replacement of PFOA by GenX, cumulative emissions of 1317.96 kg PFOA and 667.22 kg GenX were estimated during 2004-2022, in which PFOA emissions were reduced by 59.2 % due to restrictions implemented since 2016. If more stringent restrictions are implemented from 2023 to 2030, PFOA emissions will further decrease by 85.0 %, but GenX emissions will increase by an additional 21.3 %. Simultaneously, GenX concentrations in surface water are forecasted to surge by 2.02 to 2.45 times in 2023. This study deepens the understanding of PFAS alternatives and assists authorities in developing policies to administer PFAS alternatives.

Occurrence and transport of novel and legacy poly- and perfluoroalkyl substances in coastal rivers along the Laizhou Bay, northern China

The pollution profiles of 25 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in the estuaries along the Laizhou Bay, northern China were investigated to better understand the new structure of PFASs under international regulations and to estimate the mass loadings of PFASs in coastal rivers. About 39.87 kg/d of PFASs were discharged into the Laizhou Bay by the Xiaoqing, Mi and Zhimai Rivers. Total PFAS concentrations in the Xiaoqing River decreased notably in recent years, but were still greater than the levels in 2011. Contribution of replacement substances exhibited an increasing trend in recent years. However, the long-chain chemicals were still the larger contributors of PFASs. Perfluoromethoxypropionic acid (PFMPA) was first detected with high concentrations ranging from 165.3 to 586.3 ng/L in the Xiaoqing River. The results of this study provided baseline data for ecological risk assessment, environmental management and corresponding development of pollution treatment technology.

Molecular Cu Electrocatalyst Escalates Ambient Perfluorooctanoic Acid Degradation

Groundwater reservoirs contaminated with perfluoroalkyl and polyfluoroalkyl substances (PFASs) need purifying remedies. Perfluorooctanoic acid (PFOA) is the most abundant PFAS in drinking water. Although different degradation strategies for PFOA have been explored, none of them disintegrates the PFOA backbone rapidly under mild conditions. Herein, we report a molecular copper electrocatalyst that assists in the degradation of PFOA up to 93% with a 99% defluorination rate within 4 h of cathodic controlled-current electrolysis. The current-normalized pseudo-first-order rate constant has been estimated to be quite high for PFOA decomposition (3.32 L h-1 A-1), indicating its fast degradation at room temperature. Furthermore, comparatively, rapid decarboxylation over the first 2 h of electrolysis has been suggested to be the rate-determining step in PFOA degradation. The related Gibbs free energy of activation has been calculated as 22.6 kcal/mol based on the experimental data. In addition, we did not observe the formation of short-alkyl-chain PFASs as byproducts that are typically found in chain-shortening PFAS degradation routes. Instead, free fluoride (F-), trifluoroacetate (CF3COO-), trifluoromethane (CF3H), and tetrafluoromethane (CF4) were detected as fragmented PFOA products along with the evolution of CO2 using gas chromatography (GC), ion chromatography (IC), and gas chromatography-mass spectrometry (GC-MS) techniques, suggesting comprehensive cleavage of C-C bonds in PFOA. Hence, this study presents an effective method for the rapid degradation of PFOA into small ions/molecules.

The sources and bioaccumulation of per- and polyfluoroalkyl substances in animal-derived foods and the potential risk of dietary intake

Per- and polyfluoroalkyl substances (PFAS) have attracted increasing attention due to their environmental persistence and potential toxicity. Diet is one of the main routes of human exposure to PFAS, particularly through the consumption of animal-derived foods (e.g., aquatic products, livestock and poultry, and products derived from them). This review summarizes the source, bioaccumulation, and distribution of PFAS in animal-derived foods and key influential factors. In most environmental media, perfluorooctanoic acid and perfluorooctane sulfonate are the dominant PFAS, with the levels of short-chain PFAS such as perfluorobutyric acid and perfluorohexane sulfonate surpassing them in some watersheds and coastal areas. The presence of PFAS in environmental media is mainly influenced by suspended particulate matter, microbial communities as well as temporal and spatial factors, such as season and location. Linear PFAS with long carbon chains (C ≥ 7) and sulfonic groups tend to accumulate in organisms and contribute significantly to the contamination of animal-derived foods. Furthermore, PFAS, due to their protein affinity, are prone to accumulate in the blood and protein-rich tissues such as the liver and kidney. Species differences in PFAS bioaccumulation are determined by diet, variances in protein content in the blood and tissues and species-specific activity of transport proteins. Carnivorous fish usually show higher PFAS accumulation than omnivorous fish. Poultry typically metabolize PFAS more rapidly than mammals. PFAS exposures in the processing of animal-derived foods are also attributable to the migration of PFAS from food contact materials, especially those in higher-fat content foods. The human health risk assessment of PFAS exposure from animal-derived foods suggests that frequent consumption of aquatic products potentially engender greater risks to women and minors than to adult males. The information and perspectives from this review would help to further identify the toxicity and migration mechanism of PFAS in animal-derived foods and provide information for food safety management.

Target and nontarget analysis of per- and polyfluoroalkyl substances in surface water, groundwater and sediments of three typical fluorochemical industrial parks in China

The objectives of this study were to identify both legacy and emerging per- and polyfluoroalkyl substances (PFAS) from three typical fluoridated industrial parks (FIPs) in China, and to assess their environmental occurrence and fate. Complementary suspect target and nontarget screening were implemented, and a total of 111 emerging PFAS were identified. Based on the multi-mass scale analysis, 25 emerging PFAS were identified for the first time, including 24 per- and polyfluoroalkyl ether carboxylic acids (PFECAs) and 1 ultra-short chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs, C2), with a maximum percentage of 48.2 % in nontarget PFAS (exclude target PFAS). The composition of PFAS identified in different media was influenced by functional groups, carbon chain length, substituents and ether bond insertion, with poly-hydrogen substituted being preferably in water and a more diverse pattern of PFECAs in sediments. The patterns of PFAS homologs revealed distinct differences among the three typical FIPs in the shift of PFAS production patterns. The C4-PFAS and short-chain carboxylic acids (≤C6) were the main PFAS in the Fuxin and Changshu, respectively. In contrast, perfluorooctanoic acid (PFOA, C8) remained dominant in Zibo, and the highest point concentrations in water and sediment were up to 706 µg/L and 553 µg/g, respectively.

Legacy per- and polyfluoroalkyl substances (PFASs) especially alternative PFASs in shellfish from Shandong Province, China: Distribution, sources, and health risk

We investigated the distribution of 8 per- and polyfluoroalkyl substances (PFASs) in 321 shellfish samples collected from four coastal cities along the Yellow Sea and Bohai Sea of Shandong Province, China. The concentrations of total PFASs (∑PFASs) were in the range of 0.061-178.259 ng/g wet weight (ww). Two legacy long-chain compounds were dominant. Three emerging compounds and two short-chain alternatives were also observed with higher concentration and detection frequency than in previous studies, whereas 4, 8-dioxa-3H-perfluorononanoate acid (ADONA) was not detected. There were differences in concentrations and composition profiles of PFASs among different species, as well as among different sampling cities. According to scores of principal component analysis, metal plating plants, textile treatments, and fluoropolymer products were considered as the main sources of PFAS contamination in shellfish. Furthermore, a potential health risk of perfluorooctanoic acid should be highly considered for local residents that frequently consume crabs and molluscs.

Evidence of large-scale deposition of airborne emissions of per- and polyfluoroalkyl substances (PFASs) near a fluoropolymer production plant in an urban area

Airborne emissions of per- and polyfluoroalkyl substances (PFASs) from fluoropolymer manufacturing facilities-especially those producing polyvinylidene (PVDF)-have rarely been investigated. Once PFASs are released into the air from the facility stacks, they settle in the surrounding environment, contaminating all surfaces. Human beings living in close proximity to these facilities can be exposed through air inhalation and ingestion of contaminated vegetables, drinking water or dust. In this study, we collected nine surface soil and five outdoor settled dust samples within 200 m of the fence line of a PVDF and fluoroelastomer production site near Lyon (France). Samples were collected in an urban area including a sports field. High concentrations of long-chain perfluoroalkyl carboxylic acids (PFCAs) (C ≥ 9) were found at sampling points downwind of the facility. Perfluoroundecanoic acid (PFUnDA) was the predominant PFAS in surface soil (12-245 ng/g dw), whereas perfluorotridecanoic acid (PFTrDA) was in outdoor dust (<0.5-59 ng/g dw). The PFAS profiles observed in soil and dust samples very likely originate from the processing aids used for PVDF and fluoroelastomer production. To our knowledge, long-chain PFCA concentrations as high as reported herein have never been found outside the perimeter fencing of a fluoropolymer plant. PFAS concentrations in other environmental compartments (such as air, vegetables or groundwater) should be monitored to assess all potential pathways to exposure of nearby residents before carrying out human biomonitoring.

Per- and polyfluoroalkyl substances in Chinese surface waters: A review

The contamination of surface waters in China with Per- and polyfluoroalkyl (PFASs) has been extensively studied in recent decades, however, almost all studies have been conducted in small areas and/or limited samples, which are not representative of the nationwide contamination of surface water environments with PFASs. In this study, attempt was made to provide a comprehensive report about PFASs pollution in Chinese surface water based on the PRISMA. By analyzing 111 papers published between 2006 and 2022, we provide a systematic review of the pollution of PFASs in surface water environments in China. The results show that 26 PFASs contaminants were detected at least once in China's surface water environment and were mainly concentrated in the eastern part of China. Most surface water environments in China had mean PFASs concentrations below 100 ng/L. The most polluted place was the Xiaoqing River, where sampling results in 2020 showed PFASs concentrations as high as 25,429 ng/L, followed by the Tangxun Lake, the Xi River, the Daling River, the Majia River, the Baiyangdian Lake, the Liuxi River, the Jiaolai River, the Tuo River and the Zhimai River. The Xiaoqing River also has the highest concentration of the novel pollutant, with concentrations of HFPO-TA and HFPO-DA as high as 1039 ng/L and 164 ng/L. Based on the source analysis, fluoropolymer manufacturing plants are the main source of PFASs pollutants in surface water. The results of the base risk analysis using risk quotients value (RQ) method show that the RQ values of the Xiaoqing River, the surface water near Bohai Bay, the Majia River and the Tuo River PFOA are 36.9, 7.7, 3.6 and 2.1 respectively, which are high risk areas and require enhanced control. This study provides information on surface waters contaminated by PFASs nationwide, and the results can be used as a reference for the development of pollution control and management strategies for PFASs in surface waters in China.

Lithium-ion battery recycling: a source of per- and polyfluoroalkyl substances (PFAS) to the environment?

Recycling of lithium-ion batteries (LIBs) is a rapidly growing industry, which is vital to address the increasing demand for metals, and to achieve a sustainable circular economy. Relatively little information is known about the environmental risks posed by LIB recycling, in particular with regards to the emission of persistent (in)organic fluorinated chemicals. Here we present an overview on the use of fluorinated substances - in particular per- and polyfluoroalkyl substances (PFAS) - in state-of-the-art LIBs, along with recycling conditions which may lead to their formation and/or release to the environment. Both organic and inorganic fluorinated substances are widely reported in LIB components, including the electrodes and binder, electrolyte (and additives), and separator. Among the most common substances are LiPF6 (an electrolyte salt), and the polymeric PFAS polyvinylidene fluoride (used as an electrode binder and a separator). Currently the most common LIB recycling process involves pyrometallurgy, which operates at high temperatures (up to 1600 °C), sufficient for PFAS mineralization. However, hydrometallurgy, an increasingly popular alternative recycling approach, operates under milder temperatures (<600 °C), which could favor incomplete degradation and/or formation and release of persistent fluorinated substances. This is supported by the wide range of fluorinated substances detected in bench-scale LIB recycling experiments. Overall, this review highlights the need to further investigate emissions of fluorinated substances during LIB recycling and suggests that substitution of PFAS-based materials (i.e. during manufacturing), or alternatively post-treatments and/or changes in process conditions may be required to avoid formation and emission of persistent fluorinated substances.

A systematic review on distribution, sources and sorption of perfluoroalkyl acids (PFAAs) in soil and their plant uptake

Perfluoroalkyl acids (PFAAs) are ubiquitous in environment, which have attracted increasing concerns in recent years. This study collected the data on PFAAs concentrations in 1042 soil samples from 15 countries and comprehensively reviewed the spatial distribution, sources, sorption mechanisms of PFAAs in soil and their plant uptake. PFAAs are widely detected in soils from many countries worldwide and their distribution is related to the emission of the fluorine-containing organic industry. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are found to be the predominant PFAAs in soil. Industrial emission is the main source of PFAAs contributing 49.9% of the total concentrations of PFAAs (Ʃ PFAAs) in soil, followed by activated sludge treated by wastewater treatment plants (WWTPs) (19.9%) and irrigation of effluents from WWTPs, usage of aqueous film-forming foam (AFFFs) and leaching of leachate from landfill (30.2%). The adsorption of PFAAs by soil is mainly influenced by soil pH, ionic strength, soil organic matter and minerals. The concentrations of perfluoroalkyl carboxylic acids (PFCAs) in soil are negatively correlated with the length of carbon chain, log K_ow, and log K_oc. The carbon chain lengths of PFAAs are negatively correlated with the root-soil concentration factors (RCFs) and shoot-soil concentration factors (SCFs). The uptake of PFAAs by plant is influenced by physicochemical properties of PFAAs, plant physiology and soil environment. Further studies should be conducted to make up the inadequacy of existing knowledge on the behavior and fate of PFAAs in soil-plant system.

Variations of the Level, Profile, and Distribution of PFAS around POSF Manufacturing Facilities in China: An Overlooked Source of PFCA

The occurrence of per- and polyfluoroalkyl substances (PFAS) was investigated inside two manufacturing facilities in China. Levels, profiles, and spatial distribution of the detected PFAS were found to be distinctly site-specific and influenced by the area's historic function, production structure of the plant, downpour-induced accidental pollution, and variations in the adsorption and transport of compounds. Very high concentrations of PFAS [mainly C4 and C8 perfluoroalkyl sulfonic acids (PFSAs)] were found in topsoil and groundwater from both plants, with the highest values of 4.89 × 10⁶ μg/kg dw and 1.10 × 10⁴ μg/L, respectively. Elevated concentrations of perfluoroalkyl carboxylic acids (PFCAs) in this study were attributed to their unintentional formation during the electrochemical fluorination process, which might be an overlooked source of PFCA. PFAS generally showed decreasing trends from shallow layers to the bottom of the soil core and demonstrated some downward migrations at different soil depths with time, and C4-C8 PFAS presented a deeper seepage than their long-chain homologues. Total organic carbon appeared to be more important for PFAS sorption to the topsoil than to the soil core. Workers were at potential risk of exposure to perfluorooctanesulfonic acid via soil at production and storage related sites. This study provides a critical reference for the systematic control of PFAS pollution around manufacturing facilities and a proof for an overlooked source of PFCA.

Tolerance and recovery of aerobic granular sludge: Impact of perfluorooctanoic acid

The widespread use of perfluorooctanoic acid (PFOA) has rendered its frequent detection in wastewater. The tolerance and recovery of aerobic granular sludge (AGS) to PFOA were investigated in short-term (Phase Ⅰ) and long-term (Phase Ⅱ, operation strategy adjustment: shortening aeration time and prolonging anaerobic and anoxic time). Results showed that in Phase Ⅰ, the performance of R2 reactor (0.05 mg/L PFOA) was slightly negatively affected, while 0.5 and 2.0 mg/L PFOA in R3 and R4 reactors significantly damaged the key enzyme activities of AGS, leading to deterioration of nutrients removal. TN and TP removal efficiencies decreased correspondingly from 79.32% to 78.41% on day 0 to 74.66% and 74.14% in R2 and 68.57% and 67.80% in R3 and 56.94% and 57.47% in R4 on day 7, respectively. In Phase Ⅱ, the key enzyme activities of AGS were obviously renewed dependent on operation strategy adjustment and AGS self-regulation. The performance of AGS in R2 (continuously dosing 0.05 mg/L PFOA) and R4 (stopping dosing PFOA) recovered quite good, while the long-term adverse effects of 0.5 mg/L PFOA on AGS in R3 were still more difficult to be alleviated. In end of Phase Ⅱ (69-97days), the average TN and TP removal efficiencies correspondingly reached 83.31% and 82.09% in R1 (control), 80.67% and 79.62% in R2, 76.38% and 74.27% in R3, and 79.01% and 78.25% in R4, respectively. Further analysis revealed that the effect of PFOA on proteins in extracellular polymeric substances (EPS) was greater than that on polysaccharides. Specifically, short-term dosage of PFOA mainly affected loosely bound EPS, while long-term dosage of PFOA affected tightly bound EPS. Although AGS is severely inhibited by short exposure to 2.0 mg/L PFOA (in R4), after the operation strategy adjustment, EPS content decreased, nutrient and oxygen transport channels of AGS were re-established, which contributed to the recovery of AGS.

Legacy and emerging airborne per- and polyfluoroalkyl substances (PFAS) collected on PM2.5 filters in close proximity to a fluoropolymer manufacturing facility

Large fluoropolymer manufacturing facilities are major known sources of per- and polyfluoroalkyl substances (PFAS), many of which accumulate in groundwater, surface water, crops, wildlife, and people. Prior studies have measured high PFAS concentrations in groundwater, drinking water, soil, as well as dry and wet deposition near fluoropolymer facilities; however, much less is known about near-source PFAS air concentrations. We measured airborne PFAS on PM2.5 filters in close proximity to a major fluoropolymer manufacturing facility (Chemours' Fayetteville Works) located near Fayetteville, North Carolina, USA. Weekly PM2.5 filter samples collected over a six-month field campaign using high-volume air samplers at locations 3.7 km apart, north-northeast and south-southwest of the facility were analyzed for thirty-four targeted ionic PFAS species by liquid chromatography coupled to electrospray ionization tandem mass spectrometry. Twelve emerging and ten legacy PFAS compounds were detected. Thirteen PFAS were found at higher concentrations in these nearfield samples than at regional background sites, suggesting a local source for these compounds. Five emerging and five legacy PFAS compounds had maximum concentrations exceeding 1 pg m-3. PFBA, PFHxA, PFHxDA, PFOS, PMPA, NVHOS, PFO5DoA, and Nafion BP1 contributed the most to the total (legacy + emerging) PFAS concentration (86%). Six PFAS, specifically PFBA, PFOS, PFO5DoA, Nafion BP1, Nafion BP2, and Nafion BP4, provide a consistent representative profile of elevated species across the two sites (with detection frequency >50%). To our knowledge, this is the first study to report both legacy and emerging ionic PFAS in air in close proximity to a U.S. fluoropolymer manufacturing facility.

Phosphorus distribution in the water and sediment of Laizhou Bay and sediment phosphorus release potential

Phosphorus is an integral component of marine biogeochemistry. This research investigated the environmental behavior of P in Laizhou Bay using high-resolution sampling, P fractionation, and isotherm adsorption. The total dissolved P (TDP) concentration ranged from 8.4 to 61.0 μg/L in the bay water, while total P (TP) concentration ranged from 311.6 to 654.5 mg/kg in the sediment. The TDP concentration in the water was high in the estuarine area of the Yellow River and the southwestern bay under the combined effects of riverine inputs, direct wastewater discharge, and limited water exchange ability. High TP concentrations in the sediment were observed near the mouth of the Yellow River and central bay, mainly due to the movement and settlement of fine suspended particles under the influence of ocean currents. The P in the bay sediment was predominantly in the calcium-bound fraction and was associated with small particles such as silt and clay. The equilibrium P concentration (EPC₀) ranged from 1.6 to 131.4 μg/L, and P partition coefficient or buffer intensity (K_d) ranged from 104 L/kg to 880 L/kg. The EPC₀ decreased from the northeastern to southwestern area, while K_d showed an inverse distribution; therefore, the southwestern bay sediment had high buffer intensity for external P loads. Additionally, ECP₀ increased linearly, and K_d decreased with exchangeable P (Exc-P) and Fe-bound P (Fe-P) concentrations in the sediment, demonstrating that P sediment-water exchange in LZB was dominated by contributions from Exc-P and Fe-P. These results can aid the understanding of the P sources and geochemistry of coastal ecosystems, particularly sediment P release potential.

Perfluoroalkyl acids (PFAAs) in water along the entire coastal line of China: Spatial distribution, mass loadings, and worldwide comparisons

Perfluoroalkyl acids (PFAAs) have been ubiquitously distributed in water environment worldwide for a long time, especially in the estuaries and coastal areas. In this study, the distribution characteristics of 12 PFAAs in 91 main river estuaries along the entire coast of China were analyzed for the first time, and the riverine PFAAs fluxes into the coastal marine environment were estimated. Based on a mini-review, the PFAAs pollution in the coast of China at a global scale was evaluated, which was intended to reveal the overall level of PFAAs and to provide a science basis for strengthening environmental management along the coast of China. The results showed that perfluorooctanoic acid (PFOA), perfluorobutanoic acid (PFBA), and perfluorobutane sulfonic acid (PFBS) were dominant in the whole coastal region, which indicated the usage of PFAAs was changing from long-chain PFAAs to short-chain substitutes in China. With regard to the spatial distribution, the high PFAAs concentrations were found in the coastal areas of south Bohai Sea, Shandong Province from the north while those in the south were generally lower when taking the Qinling Mountain and Huaihe River as a dividing line. The estimated PFAAs riverine mass loading in the whole coastal region was 131 tons per year, and the discharge flux of the Yangtze River accounted for more than half (73.5 tons). In comparison with global data, PFAAs concentrations in the coast of China was at a moderate level, and the detected hotspots of high levels were strongly influenced by fluorochemical industries. However, the mass loading of PFAAs was diversified due to geographical differences and abundant river discharges.

Spatiotemporal distribution, ecological risk assessment and source analysis of legacy and emerging Per- and Polyfluoroalkyl Substances in the Bohai Bay, China

The Bohai Sea is one of the most polluted hotspots by per- and Polyfluoroalkyl substances (PFASs) in the world and studies on the vertical distribution of PFASs at different water layers and phase partitioning between water and suspended particulate matter (SPM) were still limited. 23 legacy and emerging PFASs were investigated in seawater and SPM throughout the Bay in this study. The average concentrations of ∑PFASs in seawater were 48.21 ng/L and 52.71 ng/L during the periods of wet and normal water, respectively. In general, the concentrations of ∑PFASs in surface water were higher than that in deep water. Legacy PFASs in seawater were dominated by PFOA and short-chain PFASs, while the emerging alternative HFPO-DA was detected in the whole water layer of the Bohai Bay with an average concentration of 1.09 ng/L. The spatial distribution showed that ∑PFASs were higher nearshore than inside the bay and higher in the south than that in the north of the bay. The average concentration of ∑PFASs in SPM was 9.02 ng/g. Long-chain PFASs and the emerging alternative 6:2 Cl-PFESA accounted for the major contaminants. The partition coefficients log K_d and φ_spm-w showed a linear positive correlation with carbon chain length. Preliminary risk assessments revealed that the ecological risk of common PFASs in the Bohai Bay was low, while PFOA was at moderate risk. The principal component analysis demonstrated that the production process of traditional fluorochemical factories, fire-fighting and emerging electroplating industries were the main sources of PFASs. This was the first comprehensive survey of emerging PFASs in different water depths and in SPM of the Bohai Bay during different seasons, which provided important scientific data for studying the ecological risks and pollution prevention of PFASs.

Occurrence of per- and polyfluoroalkyl substances (PFASs) in raw milk and feed from nine Chinese provinces and human exposure risk assessment

The per- and polyfluoroalkyl substances (PFASs) are substantially produced and applied in industrial and domestic products, which have recently aroused great public concern for their potential toxicity to humans. In the present study, raw milk (n = 107) and cow feed samples (n = 70) were collected across nine Chinese provinces, in order to investigate the occurrence of PFASs in milk and feed, and the human exposure risk to milk. The concentrations of PFASs are in the range of < method detection limit -9.82 ng/g dw (average: 1.03 ng/g dw) for milk and 0.99-144 ng/g dw (7.68 ng/g dw) for feed. Perfluorobutanoic acid (34.0%) dominates in feed, while perfluorooctanesulfonic acid (67.5%) dominates in milk. No significant positive correlations of PFASs are observed between paired feed and milk (p > 0.05). However, feeds collected around fluorination production area show relatively higher PFAS levels than those from other areas, which also increase PFAS levels in milk. Risk assessment of PFASs through milk consumption is carried out according to evolving reference doses (RfDs). The hazard quotient is more than one for both adults and children when the strictest RfDs are applied. The Monte Carlo Simulation shows that children face higher PFAS exposure risk than adults.

Emissions, Isomer-Specific Environmental Behavior, and Transformation of OBS from One Major Fluorochemical Manufacturing Facility in China

Sodium p-perfluorous nonenoxybenzenesulfonate (OBS), a novel alternative to perfluorooctane sulfonic acid (PFOS), has been widely used in various fields in China and has certain toxic effects similar to PFOS. This study monitored OBS and 15 legacy PFASs in surface water, sediment, soil, and crucian carp near a fluorochemical manufacturing factory (FMF) in Suqian, China, focusing on the emission, isomer-specific environmental fate, and transformation of OBS. One to four orders of magnitude higher concentrations of OBS than other polyfluoroalkyl substances (PFASs) in all samples indicate that industrial emission is an important point source of OBS in the surrounding environment. The concentrations of OBS in surface water, sediment, and soil decreased exponentially as the distance from the FMF increases. The proportions of OBS-c, the dominant isomer, increased in the order: water (75.5 ± 6.4%), sediment (85.7 ± 10%), fish (muscle: 94.1 ± 0.99%; blood: 93.5 ± 1.4%), suggesting its preferential accumulation in sediment and fish than other isomers. Mono-hydroxylated transformation products of OBS were first identified in water, sediment, and fish, suggesting its hydroxylation may exist in the real environment. The transformation of OBS may explain its significantly lower bioaccumulation than PFOS in fish. However, considering the higher BAF of OBS than the regulatory bioaccumulation criterion and the possible stronger toxicity of its transformation products, further studies on its bioaccumulation and transformation are warranted.

Serum concentrations of per-/polyfluoroalkyl substances and its association with renal function parameters among teenagers near a Chinese fluorochemical industrial plant: A cross-sectional study

Currently, studies on the association between per-/polyfluoroalkyl substances (PFAS) concentrations and the renal function of residents, especially teenagers, living near fluorochemical industrial plants, are relatively rare, and not all these studies suggested associations. In this cross-sectional study, 775 local teenagers (11-15 years old) were included, and serum concentrations of 18 PFAS were measured. Perfluorooctanoic acid (PFOA) was found to be the dominant PFAS with a concentration of 22.3-3310 ng/mL (mean = 191 ng/mL), accounting for 71.5-99.1% of ΣPFAS. Statistical analyses demonstrated that internal exposure of perfluoroalkyl carboxylic acids (PFCA, C8-C10) was related to the plant. In addition, the prevalence rate of chronic kidney disease (CKD) (35.0%) in the participants was relatively high. A significantly positive association was observed between the increase in PFOA concentration and increasing risk of CKD (OR = 1.741; 95% CI: 1.004, 3.088; p = 0.048) by adjusting for gender, age, body mass index (BMI), and household income. Similar positive correlation was also observed in PFHpA with CKD (OR = 1.628, 95% CI: 1.031, 2.572; p = 0.037). However, no significant correlation was observed for concentrations of other PFAS and CKD (p > 0.05). Furthermore, linear regression analyses demonstrated that none of the PFAS concentrations were significantly correlated with estimated glomerular filtration rate (eGFR) or urine albumin/urine creatinine ratio (ACR) (p > 0.05). However, a significantly negative correlation was observed between PFOA concentration and abnormal ACR (β = -0.141, 95% CI: -0.283, 0.001; p = 0.048) after stratifying by CKD. Sensitivity analyses further confirmed these results. This cross-sectional study is the first, to our knowledge, to investigate the association between PFAS concentrations and renal function in teenagers living near a Chinese industrial plant. Further prospective and metabonomic studies are needed to interpret the results and clarify the biological mechanisms underlying this association.

Associations between Novel and Legacy Per- and Polyfluoroalkyl Substances in Human Serum and Thyroid Cancer: A Case and Healthy Population in Shandong Province, East China

Per- and polyfluoroalkyl substances (PFASs) are widely detected in the environment and may cause adverse human health effects after exposure. Studies on the effect of PFASs on some health end points, including cancer, are still limited and show inconsistent results. In this research, 319 participants were recruited from Shandong Province, East China, consisting of patients with thyroid cancer and healthy controls. Seven novel and legacy PFASs were frequently detected (detection rate > 75%) in the serum samples of the participants. The concentrations of perfluorooctanoic acid (PFOA) were the highest in the case and control groups. Males showed significantly higher concentrations of PFASs than females. Exposure to PFASs was inversely associated with the risk of thyroid cancer. In the control group, we identified significant positive associations between PFASs and free thyroxine (FT4) as well as between PFOA and thyroid stimulating hormone (TSH) in females. A significant negative association between perfluorononanoic acid (PFNA) and triiodothyronine (T3) was observed in males. Our results suggest that exposure to certain PFASs could interfere with thyroid function. To our knowledge, this is the first case-control study demonstrating associations between novel and legacy PFASs in human and thyroid cancer.

Effects of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) on Soil Microbial Community

The extensive application of perfluoroalkyl and polyfluoroalkyl substances (PFASs) causes their frequent detection in various environments. In this work, two typical PFASs, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are selected to investigate their effects on soil microorganisms. Microbial community structure and microbe-microbe relationships were investigated by high-throughput sequencing and co-occurrence network analysis. Under 90 days of exposure, the alpha-diversity of soil microbial communities was increased with the PFOS treatment, followed by the PFOA treatment. The exposure of PFASs substantially changed the compositions of soil microbial communities, leading to the enrichment of more PFASs-tolerant bacteria, such as Proteobacteria, Burkholderiales, and Rhodocyclales. Comparative co-occurrence networks were constructed to investigate the microbe-microbe interactions under different PFASs treatments. The majority of nodes in the PFOA and PFOS networks were associated with the genus Azospirillum and Hydrogenophaga, respectively. The LEfSe analysis further identified a set of biomarkers in the soil microbial communities, such as Azospirillum, Methyloversatilis, Hydrogenophaga, Pseudoxanthomonas, and Fusibacter. The relative abundances of these biomarkers were also changed by different PFASs treatments. Functional gene prediction suggested that the microbial metabolism processes, such as nucleotide transport and metabolism, cell motility, carbohydrate transport and metabolism, energy production and conversion, and secondary metabolites biosynthesis transport and catabolism, might be inhibited under PFAS exposure, which may further affect soil ecological services.

Review on Per- and Poly-Fluoroalkyl Substances’ (PFASs’) Pollution Characteristics and Possible Sources in Surface Water and Precipitation of China

In recent years, due to the production and use of per- and poly-fluoroalkyl substances (PFASs), the research on the pollution characteristics and sources of PFASs in surface water and precipitation in China has attracted increasing attention. In this study, the related published articles with sampling years from 2010 to 2020 were reviewed, and the concentration levels, composition characteristics and possible sources of PFASs in surface water (rivers and lakes) and precipitation in China were summarized, including those in the Tibetan Plateau region. The results show that the concentrations of PFASs in surface water in different areas of China vary greatly, ranging from 0.775 to 1.06 × 106 ng/L. The production processes of fluorinated manufacturing facilities (FMFs) and sewage discharge from wastewater treatment plants (WWTPS) were the main sources of PFASs in surface water in China, and the concentrations of PFASs in water flowing through cities with high urbanization increased significantly compared with those before water flowed through cities with high urbanization. The compositions of PFASs in surface water gradually changed from long-chain PFASs, such as per-fluoro-octanoic acid (PFOA) and per-fluoro-octanesulfonic acid (PFOS) to short-chain PFASs, such as per-fluorobutanoic acid (PFBA), per-fluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA) and per-fluoropentanoic acid (PFPeA). The concentrations of PFASs in precipitation in China ranged from 4.2 to 191 ng/L, which were lower than those of surface water. The precipitation concentrations were relatively high around a fluorination factory and in areas with high urbanization levels. PFASs were detected in the surface water and precipitation in the Tibetan Plateau (TP), which is the global “roof of the world”, but the concentrations were low (0.115–6.34 ng/L and 0.115–1.24 ng/L, respectively). Local human activities and surface runoff were the main sources of PFASs in the surface water of the Tibetan Plateau. In addition, under the influence of the Southeast Asian monsoon in summers, marine aerosols from the Indian Ocean and air pollutants from human activities in Southeast Asia and South Asia will also enter the water bodies through dry and wet depositions. With the melting of glaciers caused by global warming, the concentration of PFASs in the surface water of the TP was higher than that before the melting of glaciers flowed into the surface water of the TP. Generally, this study summarized the existing research progress of PFAS studies on surface water and precipitation in China and identified the research gaps, which deepened the researchers’ understanding of this field and provided scientific support for related research in the future. The concentrations of PFASs in the water bodies after flowing through FMFs were significantly higher than those before water flowed through FMFs, so the discharge of the FMF production process was one of the main sources of PFASs in surface water.

Multiple pollutants stress the coastal ecosystem with climate and anthropogenic drivers

Coastal ecosystem health is of vital importance to human well-being. Field investigations of major pollutants along the whole coast of China were carried out to explore associations between coastal development activities and pollutant inputs. Measurements of target pollutants such as PFAAs and PAHs uncovered notable levels in small estuary rivers. The Yangtze River was identified to deliver the highest loads of these pollutants to the seas as a divide for the spatial distribution of pollutant compositions. Soil concentrations of the volatile and semi-volatile pollutants showed a cold-trapping effect in pace with increasing latitudinal gradient. The coastal ecosystem is facing high ecological risks from metal pollution, especially copper (Cu) and zinc (Zn), while priority pollutants of high risks vary for different kinds of protected species, and the ecological risks were influenced by both climate and physicochemical properties of environmental matrices, which should be emphasized to protect and restore coastal ecosystem functioning.

Plant uptake of perfluoroalkyl substances in freshwater environments (Dongzhulong and Xiaoqing Rivers, China)

This study provides new knowledge on the mobility, behavior, and partitioning of 17 perfluoroalkyl substances (PFASs) in the water-sediment-plant system along the Dongzhulong and Xiaoqing Rivers. The fate of PFASs in these rivers is also discussed. The study area is affected by the industrial production of perfluorooctanoic acid (PFOA). The ∑PFASs in water and sediments close to the industrial discharge were 84,000 ± 2000 ng/L and 2300 ± 200 ng/g dw, respectively, with the concentrations decreasing along the river due to dilution. PFOA was the dominant compound (74-97% of the ∑PFASs), although other PFASs were identified close to urban areas. Principal component analysis and solid-liquid distribution coefficients revealed that long-chain PFASs accumulated in the sediment whereas short-chain PFASs remained in the water all along the river. PFASs were taken up by plants and remobilized to different plant compartments according to shoot concentration factors (SCFs), root concentration factors (RCF), and transfer factors (TFs). Among the four plant species studied, floating plants absorbed high levels of PFASs, while rooted species translocated short-chain PFASs from the roots to the shoots. Therefore, floating species, due to their high uptake capacity and large proliferation rate, could eventually be used for phytoremediation.

Addressing Urgent Questions for PFAS in the 21st Century

Despite decades of research on per- and polyfluoroalkyl substances (PFAS), fundamental obstacles remain to addressing worldwide contamination by these chemicals and their associated impacts on environmental quality and health. Here, we propose six urgent questions relevant to science, technology, and policy that must be tackled to address the "PFAS problem": (1) What are the global production volumes of PFAS, and where are PFAS used? (2) Where are the unknown PFAS hotspots in the environment? (3) How can we make measuring PFAS globally accessible? (4) How can we safely manage PFAS-containing waste? (5) How do we understand and describe the health effects of PFAS exposure? (6) Who pays the costs of PFAS contamination? The importance of each question and barriers to progress are briefly described, and several potential paths forward are proposed. Given the diversity of PFAS and their uses, the extreme persistence of most PFAS, the striking ongoing lack of fundamental information, and the inequity of the health and environmental impacts from PFAS contamination, there is a need for scientific and regulatory communities to work together, with cooperation from PFAS-related industries, to fill in critical data gaps and protect human health and the environment.

Spatial and Temporal Trends of Perfluoroalkyl Substances in Global Ocean and Coastal Waters

Per- and polyfluoroalkyl substances (PFAS) have been widely detected in global surface waters since the early 2000s. Here, we have compiled and analyzed the published data for perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in surface waters of coastal seas, the Great Lakes, and open oceans to examine temporal and geospatial trends. Mass discharges from major rivers were also estimated. A large number of measurements of individual PFAS have been made in these surface waters (29 500 values), with seven C4-C10 PFSAs and nine C4-C12 PFCAs accounting for 83% of all data. However, most results (85% for PFSAs; 80% for PFCAs) were for the coastal seas of Western Europe, China, Korea, and Japan, while results were limited for coastal North America and lacking for South America and Africa. Highest median concentrations of PFCAs and PFSAs were reported in the Bohai and Yellow Seas region of China as well as in the North and Baltic seas in Europe. Significant declines in median PFSAs and C7-C12 PFCAs were also observed for the period 2012-2018 in these same regions, and for 2004-2017 in the Great Lakes. Mass discharge estimates indicated continued substantial riverine emissions of long chain (C7-C12) PFCAs in the period 2015-2019 for the coastal seas of China and reductions in emissions for Western European rivers compared to earlier time periods.

A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants

Poly- and perfluoroalkyl substances (PFAS) comprise more than 4,000 anthropogenically manufactured compounds with widescale consumer and industrial applications. This critical review compiles the latest information on the worldwide distribution of PFAS and evaluates their fate in wastewater treatment plants (WWTPs). A large proportion (>30%) of monitoring studies in WWTPs were conducted in China, followed by Europe (30%) and North America (16%), whereas information is generally lacking for other parts of the world, including most of the developing countries. Short and long-chain perfluoroalkyl acids (PFAAs) were widely detected in both the influents (up to 1,000 ng/L) and effluents (15 to >1,500 ng/L) of WWTPs. To date, limited data is available regarding levels of PFAS precursors and ultra-short chain PFAS in WWTPs. Most WWTPs exhibited low removal efficiencies for PFAS, and many studies reported an increase in the levels of PFAAs after wastewater treatment. The analysis of the fate of various classes of PFAS at different wastewater treatment stages (aerobic and/aerobic biodegradation, photodegradation, and chemical degradation) revealed biodegradation as the primary mechanism responsible for the transformation of PFAS precursors to PFAAs in WWTPs. Remediation studies at full scale and laboratory scale suggest advanced processes such as adsorption using ion exchange resins, electrochemical degradation, and nanofiltration are more effective in removing PFAS (~95-100%) than conventional processes. However, the applicability of such treatments for real-world WWTPs faces significant challenges due to the scaling-up requirements, mass-transfer limitations, and management of treatment by-products and wastes. Combining more than one technique for effective removal of PFAS, while addressing limitations of the individual treatments, could be beneficial. Considering environmental concentrations of PFAS, cost-effectiveness, and ease of operation, nanofiltration followed by adsorption using wood-derived biochar and/or activated carbons could be a viable option if introduced to conventional treatment systems. However, the large-scale applicability of the same needs to be further verified.

Occurrence of perfluorinated carboxylic acids in Mexico City's wastewater: A monitoring study in the sewerage and a mega wastewater treatment plant

An analytical method based on liquid chromatography coupled to mass spectrometry was validated to quantify five perfluorinated carboxylic acids (PFCA) namely, perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), and perfluoroundecanoic acid (PFUnA), in wastewater produced in a megacity. Sampling was performed on a monthly basis, obtaining samples from the undergrounded sewerage system and the main open-air canal transporting wastewater out the city. Steady levels of the sum of the target PFCA (ƩPFCA) were determined on both sites through the study: 419.4 ± 24.3 ng L^-1 in undergrounded sewage and 591.1 ± 39 ng L^-1 in the open-air canal. Short-chain PFCA (PFBA, PFHxA, and PFHpA) were abundant, while concentrations of PFOA and PFUnA remained lower in both sampling sites. The open-air canal was transected in four sampling points, which were sampled throughout the monitoring campaign, finding that furtive discharges of municipal and industrial wastewater increased the levels of short-chain PFCA, while those of PFOA and PFUnA were depleted. Relevant concentrations of PFBA (176.9 ± 3.3 ng L^-1), PFHxA (133.4 ± 2.5 ng L^-1), PFHpA (116.6 ± 3.9 ng L^-1), PFOA (133.1 ± 3.5 ng L^-1), and PFUnA (23.5 ± 6.5 ng L^-1) were found 60 km downstream, where the wastewater transported by the open-air canal is used in irrigation. A fraction of sewage is treated in a conventional wastewater treatment plant. The concentration of short-chain PFCA increased in effluent, adding extra loads of PFBA, PFHxA, and PFHpA to the environment.

Perfluoroalkyl acids in rapidly developing coastal areas of China and South Korea: Spatiotemporal variation and source apportionment

Polyfluoroalkyl substances (PFASs) are recognized as emerging contaminants that have captured worldwide attention. They are primarily transported in environments and spread around the globe due to their persistent and bioaccumulative characteristics. In this study, 15 PFASs were detected in major rivers of the rapidly developing coastal areas of China and South Korea. The concentrations and compositions of these PFASs varied greatly between different regions along the coastline. The total concentrations ranged from 14.9 to 16,500 ng L^-1, and the mean concentrations of Σ₁₅PFASs in Liaodong Bay, Bohai Bay, Laizhou Bay, and the west coast of South Korea were 124 ng L^-1, 81.4 ng L^-1, 1550 ng L^-1, and 36.2 ng L^-1, respectively. In Laizhou Bay, the relatively high perfluorooctanoic acid (PFOA) was due to the high usage and manufacturing of PFOA-containing products and contributed 59% of the total compounds. In Liaodong Bay and Bohai Bay, PFBA and PFOA were the most abundant compounds, accounting for >55% of the total compounds. Along the west coast of South Korea, PFBA and PFPeA were the most prevalent compounds, contributing 28% and 24% of the total compounds, respectively. The data collected in the last decade were analyzed to investigate the temporal trends of selected PFASs. The total concentration of Σ₁₀ PFASs decreased in both China and South Korea, while the proportion of short-chain PFASs increased. The proportion of C₄-C₇ PFCAs in South Korea rapidly increased from 46% to 79% but decreased from 49% to 43% in China. The positive matrix factorization (PMF) model successfully addressed the site-specific source apportionment, which showed that 53% of the PFASs in Laizhou Bay were due to fluorine manufacturing. The results of this study provide novel insights into elucidating the spatiotemporal distribution and complicated sources of PFASs over a large area and provide a clear message for all stakeholders, water and coastal managers, and scientists.

Legacy and novel perfluoroalkyl and polyfluoroalkyl substances in industrial wastewater and the receiving river water: Temporal changes in relative abundances of regulated compounds and alternatives

Concentrations of 28 novel and legacy perfluoroalkyl and polyfluoroalkyl substances (PFASs) in wastewater from 77 industrial plants in the largest industrial complex in Korea were determined. The industrial plants were of eight types (advanced electronic, battery, chemical, general electronic, glass and ceramic, metal, polymer, and textile). PFAS concentrations in river water receiving the wastewater were determined to assess the impact of wastewater from the industrial complex. Only 19 and nine target PFASs were detected in untreated industrial wastewater and river water, respectively. Novel PFASs such as F53B (6:2 chlorinated polyfluoroalkyl ether sulfonate) were not detected. The mean PFASs concentration in industrial wastewater treatment plant effluent was 5.18 µg/L. The mean total PFASs concentration was highest in advanced electronic plant effluent, second highest in general electronic plant effluent, and lowest in battery and chemical plant effluents. Perfluorohexane sulfonate was the dominant homolog, being detected in effluent from plants of all classes and contributing 96% of total discharged PFASs by mass. Perfluorooctane sulfonate (included in the Stockholm Convention) use has decreased markedly since previous studies. Perfluorooctane sulfonate has largely been replaced by PFASs with fewer than seven carbon atoms. A similar change was found for river water receiving industrial wastewater.

PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding

We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on 2 to 5 legacy PFAS, and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly, and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine measurements complemented by suspect screening using high-resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids. Available data suggest that diet is the major human exposure pathway for some PFAS, but there is large variability across populations and PFAS compounds. Additional data on total fluorine in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, for the general population, exposures from dust, personal care products, indoor environments, and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a reevaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations. Environ Toxicol Chem 2021;40:631-657. © 2020 SETAC.

Challenges and Current Status of the Biological Treatment of PFAS-Contaminated Soils

Per- and polyfluoroalkyl substances (PFAS) are Synthetic Organic Compounds (SOCs) which are of current concern as they are linked to a myriad of adverse health effects in mammals. They can be found in drinking water, rivers, groundwater, wastewater, household dust, and soils. In this review, the current challenge and status of bioremediation of PFAs in soils was examined. While several technologies to remove PFAS from soil have been developed, including adsorption, filtration, thermal treatment, chemical oxidation/reduction and soil washing, these methods are expensive, impractical for in situ treatment, use high pressures and temperatures, with most resulting in toxic waste. Biodegradation has the potential to form the basis of a cost-effective, large scale in situ remediation strategy for PFAS removal from soils. Both fungal and bacterial strains have been isolated that are capable of degrading PFAS; however, to date, information regarding the mechanisms of degradation of PFAS is limited. Through the application of new technologies in microbial ecology, such as stable isotope probing, metagenomics, transcriptomics, and metabolomics there is the potential to examine and identify the biodegradation of PFAS, a process which will underpin the development of any robust PFAS bioremediation technology.

Isomers of emerging per- and polyfluoroalkyl substances in water and sediment from the Cape Fear River, North Carolina, USA

Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous environmental contaminants found in many parts of the globe and in all environmental compartments. The phase out of legacy C8 PFAS has led to an increase in functionality of the carbon backbone chain to include ether linkages and branching points. With the increased production of functionalized PFAS, there remains a paucity of information regarding the occurrence of constitutional isomers in the environment. In this study, a series of novel PFAS constitutional isomers were detected by high resolution mass spectrometry and characterized by MS/MS in river water collected weekly over 40 weeks. Constitutional isomers of C₄H₂F₈O₄S₁ (-1.8 ± 2.5 ppm) were detected for the first time in 83% of the samples analyzed and the MS/MS fragmentation patterns clearly indicated there were two coeluting isomers present. Two chromatographically resolved peaks with deprotonated molecular formula C₇H₁F₁₄O₅S₁ (1.9 ± 2.7 and 2.2 ± 3.1 ppm) were detected in 85% of the samples measured. MS/MS fragmentation patterns and a standard provided by a fluorochemical manufacturer confirmed the two isomers. A series of novel chlorinated PFAS were detected (M-1: C₁₁H₁Cl₁F₂₀O₅ 0.9 ± 2.7 ppm and C₁₄H₁Cl₁F₂₆O₆ 2.1 ± 2.6 ppm) in 34% of the water samples analyzed. The exact structure is not confirmed. River sediment collected below the water sample location contained several of the compounds detected in the water column illustrating the connectivity between the environmental compartments. Results highlight the need for further studies on the occurrence of isomers and authentic standards to confirm structures.

Endocrine disruption by PFAS: A major concern associated with legacy and replacement substances

Perand poly-fluorinated alkyl substances (PFAS) have been used for decades in a great variety of processes and products by virtue of their exceptional properties, versatility and chemical stability. Nevertheless, it is increasingly recognized that these substances can represent a serious hazard to human health and living organisms due to their persistence, long-range transport potential and tendency to accumulate in biota. For this reason, some efforts have been made across the EU to identify alternative molecules, with a shorter carbon chain and theoretically safer profile, that might replace the previous generation of legacy PFAS. Unfortunately, this strategy has not been entirely successful and serious concerns are still posed by PFAS in different human populations. Among others, an emerging aspect is represented by the adverse effects that both legacy and alternative PFAS can exert on the human endocrine system, with respect to vulnerable target subpopulations. In this review we will briefly summarize PFAS properties, uses and environmental fate, focusing on their effects on human reproductive capacity and fertility, body weight control and obesity as well as thyroid function.

Concentration, spatial distribution, and health risk assessment of PFASs in serum of teenagers, tap water and soil near a Chinese fluorochemical industrial plant

Discharges released from fluorochemical industrial plants lead to severe contamination of the environment with per- and polyfluoroalkyl substances (PFASs), which may pose risks to human health. In this study, 187 serum samples from teenagers (age = 14 years), 22 tap water samples and 40 soil samples were collected in areas within 0-11 km of a fluorochemical industrial plant in Huantai County, Shandong Province, and concentrations of 18 PFASs were quantified by UPLC-MS/MS. Perfluorooctanoic acid (PFOA) was found to be predominant, concentrations of which ranged from 40.4 to 845 ng/mL in serum, from 2.88 to 19.3 ng/L in tap water, from 4.40 to 189 ng/g in soil, and accounting for 84.1-98.6%, 15.9-79.8%, and 73.8-96.7% of the total PFASs, respectively. Statistical analysis demonstrated that concentrations of perfluorinated carboxylic acids (PFCAs) in soil (C5-C9) and serum (C8-C10) were associated with the industrial plant. And PFOA concentrations in tap water were not relevant to the industrial plant, which were comparable with the non-contaminated area and lower than the threshold value recommended by U.S. EPA (70 ng/mL), indicating that the contribution to the high concentration of serum PFOA of local teenagers by drinking water was limited. Moreover, PFCAs in soil only made a limited contribution to the serum PFCAs of local residents by direct inhalation and dermal exposure, but the potential health risk by the soil via food chain should be paid attention to. Furthermore, health risk assessment demonstrated that high concentrations of PFOA in serum could pose potential health risk to local teenagers. Therefore, effective measures should be taken to attenuate the health risks caused by the industrial plant to local residents, and further epidemiological studies should be carried out in the future.

Paper product production identified as the main source of per- and polyfluoroalkyl substances (PFAS) in a Norwegian lake: Source and historic emission tracking

The entirety of the sediment bed in lake Tyrifjorden, Norway, is contaminated by per- and polyfluoroalkyl substances (PFAS). A factory producing paper products and a fire station were investigated as possible sources. Fire station emissions were dominated by the eight carbon perfluoroalkyl sulfonic acid (PFSA), perfluorooctanesulfonic acid (PFOS), from aqueous film forming foams. Factory emissions contained PFOS, PFOS precursors (preFOS and SAmPAP), long chained fluorotelomer sulfonates (FTS), and perfluoroalkyl carboxylic acids (PFCA). Concentrations and profiles in sediments and biota indicated that emissions originating from the factory were the main source of pollution in the lake, while no clear indication of fire station emissions was found. Ratios of linear-to branched-PFOS increased with distance from the factory, indicating that isomer profiles can be used to trace a point source. A dated sediment core contained higher concentrations in older sediments and indicated that two different PFAS products have been used at the factory, referred to here as Scotchban and FTS mixture. Modelling, based on the sediment concentrations, indicated that 42-189 tons Scotchban, and 2.4-15.6 tons FTS mixture, were emitted. Production of paper products may be a major PFAS point source, that has generally been overlooked. It is hypothesized that paper fibres released from such facilities are important vectors for PFAS transport in the aquatic environment.

Per- and polyfluoroalkyl substances in Chinese and German river water - Point source- and country-specific fingerprints including unknown precursors

This study aimed at comparing source-specific fingerprints of per- and polyfluoroalkyl substances (PFASs) in river water from China and Germany, selected as countries with different histories of PFAS production. Samples were collected from up- and downstream of seven suspected point sources in autumn 2018. Amongst the 29 analyzed legacy and emerging PFASs, 24 were detected, with a sum ranging from 2.7 ng/L (Alz River) to 420,000 ng/L (Xiaoqing River). While mass flow estimates for the Xiaoqing River and Yangtze River (mean: 20 and 43 t/y, respectively) indicated ongoing high emissions of the legacy compound PFOA in China, its ether-based replacements HFPO-DA and DONA showed the highest contribution downstream of a German fluoropolymer manufacturing site (50% and 40% of ΣPFASs measured, respectively). In river water impacted by manufacturing sites for pharmaceutical and pesticide intermediates, the short-chain compound PFBS was the most prevalent substance in both countries. The German Ruhr River, receiving discharges from the electroplating industry, was characterized by the PFOS replacement 6:2 FTSA. Isomer profiling revealed a higher proportion of branched isomers in the Chinese Xi River and Xiaoqing River than in other rivers. This points to different synthesis routes and underlines the importance of differentiating between linear and branched isomers in risks assessments. Upon oxidative conversion in the total oxidizable precursor (TOP) assay, the increase of the short-chain compound PFBA was higher in German samples than in Chinese samples (88 ± 30% versus 12 ± 14%), suggesting the presence of a higher proportion of unknown precursors to PFBA in the German environment. Amongst the ether-based replacements, DONA and 6:2 Cl-PFESA were fully or partially degraded to non-targeted oxidation products, whereas HFPO-DA showed no degradation. This indicates that the inclusion of ether-based PFASs and their oxidation products in the TOP assay can help in capturing a larger amount of the unknown PFAS fraction.

Biomonitoring of chlorinated polyfluoroalkyl ether sulfonic acid in the general population in central and eastern China: Occurrence and associations with age/sex

Although chlorinated polyfluoroalkyl ether sulfonic acid (Cl-PFESA) has been reported to be widespread in different environmental matrices of China, its exposure data in the general Chinese population are very limited. In the present study, the serum-to-whole-blood ratio was first assessed for 6:2 Cl-PFESA (mean/median: 2.07/1.82) based on its paired concentrations (n = 36), which allows a comparison in different blood matrices. The exposure levels of Cl-PFESAs in the general population were investigated by collecting blood samples (n = 1516) from residents of seven cities in central and eastern China. 6:2 Cl-PFESA was observed as the third-highest contributing polyfluoroalkyl substance (PFAS) (8.69%), with the median concentration at 2.18 ng/mL, indicating its importance for assessing the human exposure risks of PFASs. The regional difference between 6:2 Cl-PFESA and perfluorooctane sulfonate (PFOS) can be explained by their use pattern in China. Overall, similar to PFOS, 6:2 Cl-PFESA displays significantly increasing levels with increasing age for both males and females, with significantly higher levels in males. However, a significant sex dependence was found for 6:2 Cl-PFESA in one specific age group (41-60), while there was no significance in the other groups although males display higher levels than females. Our study provides robust data regarding human exposure to 6:2 Cl-PFESA in the general population in central and eastern China.

Environment occurrence of perfluoroalkyl acids and associated human health risks near a major fluorochemical manufacturing park in southwest of China

Despite China being the largest global manufacturer of perfluoroalkyl acids (PFAAs), few studies have been carried out on the environmental occurrence and associated human health risks of PFAAs emitted from manufacturing sites in China. Here, river water, tap water, soil and leaf samples were collected around a major fluorochemical manufacturing park (FMP) in the southwest of China in 2019. High ΣPFAA concentrations (sum of 12 PFAAs) of 3817 ng/L, 3254 ng/L, 322-476 ng/g dw and 23401-33749 ng/g dw were measured near the FMP in river water, tap water, soil and leaves, respectively, indicating that the FMP is a point source of PFAAs. PFOA was the predominant PFAA in all samples (58.5-98.6 %) indicating the production or use of PFOA at the FMP. PFOA concentrations in most tap water samples (> 300 ng/L in 31 of 38 samples) exceeded the U.S. EPA health advisory. Proportions of branched PFOA isomers in all samples were in 5.9-47.4 %, suggesting the production or use of PFOA manufactured by electrochemical fluorination at the FMP. It is recommended to focus more attention on branched PFOA isomers in the future because otherwise health risks may be underestimated due to their relatively high proportions in China.

Spatial distribution of phthalate acid esters in sediments of the Laizhou Bay and its relationship with anthropogenic activities and geochemical variables

Spatial distribution and ecological risks of phthalate acid esters (PAEs) in sediments of the Laizhou Bay were investigated, and the relationships of PAEs with human activities and geochemical variables were studied in this work. Thirteen detectable PAEs were widespread occurrence, and the total PAE concentrations ranged from 813.1 to 11,975.6 μg/kg dry weight in sediments of the Laizhou Bay. Di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) were predominant and accounted for 51.9% of ΣPAEs. The major sources of PAEs with their characteristic PAE congeners or composition could be classified as riverine runoff from catchments of the Yellow River and the rivers Xiaoqing & Zhimai, and direct discharge from the west coast and Binhai Zone, according to continuous PAE spatial distribution patterns generated by GIS techniques. The concentrations of most PAEs gradually decreased from west inshore to east offshore in inverted S shapes, which was consistent with the tide field of the Laizhou Bay. There are negative correlations between sediment depth and all PAEs, and nine PAEs exhibited negative correlations with salinity using Pearson correlation analysis. Depth and salinity exerted negative influence on PAEs (contributions of 55.8% and 32.0%, respectively) according to redundancy analysis. The DBP concentrations of 15.1% sites exceeded the ERLs and only one site had the DEHP concentration exceeded environmental risk limits. The DBP risk quotient values of 11.3% (for algae), 3.8% (for crustaceans) and 43.4% (for fish) sites exceeded 1, and most of these sites are near to four major sources. These results might benefit the implementation of effective environmental management and remediation practices.

Flows, Stock, and Emissions of Poly- and Perfluoroalkyl Substances in California Carpet in 2000-2030 under Different Scenarios

In this study, we present a holistic analysis of the stock and emissions of poly- and perfluoroalkyl substances (PFAS) in California carpet in 2000-2030. Our high estimate is that, in 2017, the total PFAS accumulated in in-use carpet stock and landfilled carpet are ∼60 and ∼120 tonnes, respectively, and the resultant PFAS emissions are ∼800 and ∼100 kg, respectively. Among the three subclasses (side-chain polymers, PFAA, and nonpolymeric precursors), side-chain polymers dominate the in-use stock and landfill accumulation, while nonpolymeric precursors dominate the resultant emissions. Our low estimate is typically 8-15% of the high estimate and follows similar trends and subclass breakdowns as the high estimate. California's new Carpet Stewardship Regulations (24% recycling of end-of-life carpet) will reduce the landfilled PFAS by 6% (7 tonnes) at the cost of increasing the in-use stock by 2% (2 tonnes) in 2030. Aggressive PFAS phase-out by carpet manufacturers (i.e., reduce PFAS use by 15% annually starting 2020) could reduce the in-use PFAS stock by 50% by 2030, but its impact on the total landfilled PFAS is limited. The shift toward short-chain PFAS will also significantly reduce the in-use stock of long-chain PFAS in carpet by 2030 (only 25% of the total PFAS will be long-chain). Among the data gaps identified, a key one is the current area-based PFAS emission reporting (i.e., g PFAS emitted/area carpet/time), which leads to the counterintuitive result that reducing the PFAS use in carpet production has no impact on the PFAS emissions from in-use stock and landfills. Future technical studies should either confirm this or consider a mass-based unit (e.g., g PFAS emitted/g PFAS used/time) for better integration into regional substance flow analysis. Other noticeable data gaps include the lack of time-series data on emissions from the in-use stock and on leaching of side-chain polymers from landfills.

Spatial and temporal variations of antibiotics in a tidal river

Estuary is an important route for the transport of terrestrial contaminants to the ocean. Its unique hydrodynamic properties may influence the fate and distribution of pollutants. Previous studies have shown that severe pollution because of antibiotics has occurred in many inland surface waterbodies; however, the behavior of antibiotic residuals remains poorly understood in estuarine environments. In this study, the occurrence and spatiotemporal distribution of seven selected antibiotics (i.e., sulfamethazine, sulfamethoxazole, trimethoprim, ofloxacin, ciprofloxacin, erythromycin, and roxithromycin) in a tidal river were investigated through one continuous and four synoptic sampling events. Results show that the concentrations of most antibiotics are in the nanogram per liter level, except for trimethoprim with the highest concentration up to 12,440 ng L^-1 during the wet season. Except for sulfamethazine, the other six antibiotics showed high concentrations (i.e., > 100 ng L^-1) in at least one sampling campaign. Different temporal distribution patterns of these antibiotics indicated that they were mainly controlled by source loading, flow condition, and discharge amounts. Spatial distribution indicated that the main pollution source of trimethoprim was located in lower reaches, while the other six antibiotics mainly came from the upstream sources. Based on the theoretical dilution line, erythromycin and roxithromycin degraded in the tidal river, whereas the other five types of antibiotics showed a conservative behavior. Tide has important effects on the spatial distribution of antibiotics, especially those with a wide concentration range, in estuarine environments. Furthermore, risk assessment based on the calculated risk quotients showed that five types of antibiotics pose high risks to aquatic organisms. These observations provided new insight into the distribution and transport of common antibiotics in estuarine environments.

Managing health risks of perfluoroalkyl acids in aquatic food from a river-estuary-sea environment affected by fluorochemical industry

Substantial perfluoroalkyl acids (PFAAs) production still occurs in China, and the consumption of aquatic products is a critical exposure pathway of PFAAs in humans. In this study, specimens of 16 freshwater and 40 marine species were collected in the river-estuary-sea environment affected by a mega fluorochemical industry park in China in 2015, and the edible tissues of these organisms were analyzed for PFAA levels. Perfluorooctanoic acid (PFOA) was the dominating contaminant with an overall contribution of more than 90%, and concentrations as high as 2161 ng/g wet weight (measured in the freshwater winkle). All species with the greatest PFOA levels were benthic. The trophic magnification factor (TMF) of PFOA was 1.10 for freshwater species and 1.28 for marine species, indicating that PFOA was slightly magnifying. Analysis of carbon source indicated that freshwater species were more benthic feeding, while marine species were more pelagic feeding. Aquatic food consumption screening values of PFOA were modified according to estimated daily intake (EDI) values, which generated recommendations for limited meal categories and the do-not-eat category. Thus, this study provides recommendations for mitigating the health risks of PFAA-contaminated aquatic food, ranging from food selection to consumption frequency and proper food processing.

Temporal Trends (1981-2013) of Per- and Polyfluoroalkyl Substances and Total Fluorine in Baltic cod (Gadus morhua)

Temporal trends from 1981 to 2013 of 28 per- and polyfluoroalkyl substances (PFASs) were investigated in liver tissue of cod (Gadus morhua) sampled near southeast Gotland, in the Baltic Sea. A total of 10 PFASs were detected, with ∑₂₈ PFAS geometric mean concentrations ranging from 6.03 to 23.9 ng/g ww. Perfluorooctane sulfonate (PFOS) was the predominant PFAS, which increased at a rate of 3.4% per year. Most long-chain perfluoroalkyl carboxylic acids increased at rates of 3.9 to 7.3% per year except for perfluorooctanoate (PFOA), which did not change significantly over time. The perfluoroalkyl acid precursors perfluorooctane sulfonamide (FOSA) and 6:2 fluorotelomer sulfonic acid were detected, of which the former (FOSA) declined at a rate of -4.4% per year, possibly reflecting its phase-out starting in 2000. An alternate time trend analysis from 2000 to 2013 produced slightly different results, with most compounds increasing at slower rates compared to the entire study period. An exception was perfluorohexane sulfonate (PFHxS), increasing at a faster rate of 3.7% measured from 2000 on, compared to the 3.0% per year measured starting from 1981. Analysis of the total fluorine content of the samples revealed large amounts of unidentified fluorine; however, its composition (organic or inorganic) remains unclear. Significant negative correlations were found between concentrations of individual PFASs (with the exception of PFOS) and liver somatic index. In addition, body length was negatively correlated with PFOA and perfluorononanoate, but positively correlated with perfluorododecanoate (PFDoDA) and FOSA. Additional studies on endocrine, immunological, and metabolic effects of PFAS in marine fish are essential to assess the environmental risk of these substances. Environ Toxicol Chem 2020;39:300-309. © 2019 SETAC.

Tissue distribution of 14C-labelled perfluorooctanoic acid in adult mice after 1-5 days of dietary exposure to an experimental dose or a lower dose that resulted in blood levels similar to those detected in exposed humans

Perfluorooctanoic acid (PFOA), a global environmental pollutant detected in both wildlife and human populations, has several pathophysiological effects in experimental animals, including hepatotoxicity, immunotoxicity, and developmental toxicity. However, details concerning the tissue distribution of PFOA, in particular at levels relevant to humans, are lacking, which limits our understanding of how humans, and other mammals, may be affected by this compound. Therefore, we characterized the tissue distribution of ¹⁴C-PFOA in mice in the same manner as we earlier examined its analogues perfluorooctanesulfonate (PFOS) and perfluorobutanesulfonate (PFBS) in order to allow direct comparisons. Following dietary exposure of adult male C57/BL6 mice for 1, 3 or 5 days to a low dose (0.06 mg/kg/day) or a higher experimental dose (22 mg/kg/day) of ¹⁴C-PFOA, both scintillation counting and whole-body autoradiography revealed the presence of PFOA in most of the 19 different tissues examined, demonstrating its ability to leave the bloodstream and enter tissues. There were no differences in the pattern of tissue distribution with the low and high dose and the tissue-to-blood ratios were similar. At both doses, PFOA levels were highest in the liver, followed by blood, lungs and kidneys. The body compartments estimated to contain the largest amounts of PFOA were the liver, blood, skin and muscle. In comparison with our identical studies on PFOS and PFBS, PFOA reached considerably higher tissue levels than PFBS, but lower than PFOS. Furthermore, the distribution of PFOA differed notably from that of PFOS, with lower tissue-to-blood ratios in the liver, lungs, kidneys and skin.