Perfluorooctane Sulfonate Concentrations Research Articles

Contamination of per- and polyfluoroalkyl substances in the water source from a typical agricultural area in North China

There is limited information on contaminations of per- and polyfluoroalkyl substances (PFASs) in the water source affected by agricultural activities. The contamination of PFASs was investigated in the sources of agricultural groundwater and nearby surface water from an important vegetable production base supply for Beijing and Tianjin, located in North China. Σ13PFAS concentrations ranged from 0.321 to 8.285 ng/L, with an average concentration of 2.022 ng/L in the groundwater and 19.673 ng/L in the surface water. With the increase in the carbon chain length, the mean concentrations of PFASs in groundwater generally showed a decreasing trend. The dominated congeners of short-chain perfluorobutanesulfonate and perfluorooctanoate acid (PFOA) were detected in all groundwater samples, with mean concentrations of 0.944 and 0.654 ng/L. The difference was that PFOA and perfluorooctanesulfonate (PFOS) were the dominant congeners in nearby surface water, with concentrations of 7.585 and 3.421 ng/L. Thus, the concentrations of PFOA and PFOS in the surface water were about 8.5 times higher than those in the groundwater, indicating that Σ13PFAS concentrations might decrease with the water migration from the overground to the underground. In addition, significant correlations were observed between PFASs and DOC/TN related to agricultural activities, suggesting a certain relationship existed between PFAS conger distributions and organic carbon/nutrients in water. Health risk assessment indicated that the PFAS exposure caused insignificantly immediate harm to residents in the studied area. This survey provided information on the sources, spatial distribution, and potential migration characteristics of PFASs in a typical agricultural area of North China.

Synthesis and characterization of PCN-222 metal organic framework and its application for removing perfluorooctane sulfonate from water

Poly- and perfluoro alkyl substances (PFAS) are a group of man-made, notoriously persistent, and highly toxic contaminants in the environment reported worldwide. Many adsorbents including granular activated carbon, graphene, biochar, zeolites, and clay minerals have been tested for PFAS removal from water, but most of these materials suffer from high cost and/or poor removal performance. Here, we synthesized, characterized, and examined the efficiency of PCN-222(Fe), a new porous metal organic framework (MOF) with high water stability, for adsorptive removal of a frequently occurring PFAS, perfluorooctane sulfonate (PFOS), from water. The adsorption isotherm and kinetic studies revealed high PFOS adsorption capacity of PCN-222 (2257 mg/g), with rapid PFOS removal rate (within 30 min). The structure of PCN-222 was unaffected in water in the pH range of 2–10 but disintegrated and lost its PFOS removal ability at pH > 10. The PFOS adsorption on PCN-222 was an endothermic reaction. Electrostatic attraction was a dominant mechanism for PFOS adsorption at < 1694 mg/g PFOS concentration, while hydrophobic interaction accompanied with hydrogen-bonding was responsible at ≥ 1694 mg/g PFOS concentration. The interlayer morphology of PCN-222 did not change due to increasing PFOS loading. The findings of this study demonstrated superior features of PCN-222 over other conventional adsorbents for its potential application in removing PFOS from contaminated water to reduce PFOS transfer from water to living organisms.

Understanding PFOS Adsorption on a Pt Electrode for Electrochemical Sensing Applications

AbstractPer‐ and polyfluroalkyl substances (PFAS) are drawing increasing attention in the research community due to their wide spread applications and their toxicity to animals and humans. Effective early detection method of PFAS chemicals in aqueous environment is important to reduce exposure and mitigate the potential toxic effects. This study focuses on the electrochemical detection of per‐fluoro octane sulfonate (PFOS) with differential pulse voltammetry and electrochemical impedance spectroscopy on a bare platinum electrode. We observe three distinct regions of adsorption behaviors with respect to PFOS concentration from 0–1000 nM, reflecting changes in the modes of adsorption due to different adsorbate‐adsorbate interactions on a bare electrode. The adsorption isotherm constant for PFOS adsorption on a Pt electrode is calculated to be 1.6×1012 cm3 mol−1 from fitting the electrochemical data with a modified Langmuir isotherm model.

Perfluoroalkyl and polyfluoroalkyl substances in cord serum of newborns and their potential factors

The demonstrated developmental and reproductive toxicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), coupled with the increasing production and use of emerging per- and polyfluoroalkyl substances (PFASs) has resulted in progressively higher human exposure levels. This has raised concerns about PFAS exposure levels in the fetus, which is highly susceptible to the potential effects of hazardous environmental chemicals. However, in utero exposure to PFASs and health implications have not been fully characterized in China. To fill this gap, we analyzed 19 PFASs in umbilical cord serum samples (n = 66). Information about the mothers and newborns was obtained through questionnaires. Associations between maternal characteristics and neonatal birth weight and PFAS concentrations were analyzed using nonparametric tests. As results, PFOA was detected in all serum samples. The highest median concentration of PFOS in umbilical serum was 1.092 ng·mL-1, followed by perfluoropentanoic acid (median: 0.633 ng·mL-1). Trifluroacetic acid and perfluoropropanoic acid were detected in cord serum for the first time, and their median concentrations were 0.229 and 0.266 ng·mL-1, respectively. Neonatal birth weight was negatively correlated with long-chain PFOS (r = −0.319, P < 0.05), and the concentrations of perfluoroundecanoic acid and perfluorododecanoic acid were significantly different between the birth weight groups. Maternal age, maternal education, diet, and nutritional supplementation during pregnancy can all affect umbilical serum exposure to PFASs. These results demonstrate that legacy PFASs remain major contributors to the composition of human PFASs, while the concentration levels of emerging short-chain alternatives have increased significantly. Modifying the mother's diet may reduce the risk of intrauterine PFAS exposure. Special attention to exposure to highly novel PFASs and confirmation of potential determinants should be taken as a priority in the plan for risk management and actions in this area.

Acute toxicity and risk assessment of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in tropical cladocerans Moina micrura

Per- and polyfluoroalkyl substances (PFAS) are gaining worldwide attention because of their toxicity, bioaccumulative and resistance to biological degradation in the environment. PFAS can be categorised into endocrine disrupting chemicals (EDCs) and identified as possible carcinogenic agents for the aquatic ecosystem and humans. Despite this, only a few studies have been conducted on the aquatic toxicity of PFAS, particularly in invertebrate species such as zooplankton. This study evaluated the acute toxicity of two main PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), by using freshwater cladocerans (Moina micrura) as bioindicators. This study aimed to assess the adverse effects at different levels of organisations such as organ (heart size and heart rate), individual (individual size and mortality) and population (lethal concentration, LC50). PFOA was shown to be more hazardous than PFOS, with the LC50 values (confidence interval) of 474.7 (350.4–644.5) μg L−1 and 549.6 (407.2–743.9) μg L−1, respectively. As the concentrations of PFOS and PFOA increased, there were declines in individual size and heart rate as compared to the control group. The values of PNECs acquired by using the AF method (PNECAF) for PFOA and PFOS were 0.4747 and 0.5496 μg L−1, respectively. Meanwhile, the PNEC values obtained using the SSD method (PNECSSD) were 1077.0 μg L−1 (PFOA) and 172.5 μg L−1 (PFOS). PNECAF is more protective and conservative compared to PNECSSD. The findings of this study have significant implications for PFOS and PFOA risk assessment in aquatic environments. Thus, it will aid freshwater sustainability and safeguard the human dependency on water resources.

Bioaccumulation of perfluoroalkyl substances in the Lake Erie food web

The bioaccumulation and biomagnification of perfluoroalkyl substances (PFAS) in the Lake Erie food web was investigated by analyzing surface water and biological samples including 10 taxa of fish species, 2 taxa of benthos and zooplankton. The carbon (δ13C) and nitrogen (δ15N) isotopic composition and fatty acids profiles of biological samples were used to evaluate the food web structure and assess the biomagnification of PFAS. Perfluorooctane sulfonate (PFOS) dominated the total PFAS (ΣPFAS) concentration (50–90% of ΣPFAS concentration), followed by C9–C11 perfluorinated carboxylic acids (PFCAs). The highest PFOS concentrations (79 ± 4.8 ng/g, wet weight (wwt)) and ΣPFAS (88 ± 5.2 ng/g, wwt) were detected in yellow perch (Perca flavescens). The C8–C14 PFAS biomagnification factors (BMFs) between apex piscivorous fish and prey fish were found to be generally greater than 1, indicative of PFAS biomagnification, while biodilution (BMF<1) was observed between planktivorous fish and zooplankton. Trophic magnification factors (TMFs) of C8–C14 PFCA were not correlated with perfluoroalkyl chain length. The C4–C9 PFAS were detected in the surface water of Lake Erie, and PFBA was found to have the highest concentrations (2.1–2.8 ng/L) among all PFAS detected. The log of bioaccumulation factor (BAF) was found to generally increase with increasing log Kow for C6, 8, and 9 PFAS in all selected species from three tropic levels.

Temporal trends in PFAS concentrations in livers of a terrestrial raptor (common buzzard; Buteo buteo) collected in Belgium during the period 2000–2005 and in 2021

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have been globally distributed. Biological time series data suggest variation in temporal PFAS concentrations due to regulations and the phase-out of multiple PFAS analytes. Nonetheless, biomonitoring temporal trends of PFAS concentrations in raptors has only been done sporadically in Europe at a national scale. In the present study, we examined the concentrations of 28 PFAS in livers of common buzzard (Buteo buteo) collected in Belgium in the period 2000–2005 and in 2021. Despite the regulations and phase-out, the ΣPFAS concentrations remained similar in the livers over the past 20 years. However, over time the abundance of perfluorooctane sulfonate (PFOS), dominant in livers collected in 2000–2005, to the ΣPFAS concentration decreased from 46% to 27%, whereas the abundance of perfluorotetradecanoic acid (PFTeDA), dominant in 2021, increased from 19% to 43%. The PFOS concentrations in the present study did not exceed the Toxicity Reference Values (TRVs), which were determined in liver on the characteristics of an avian top predator. The absence of temporal changes in PFAS concentrations is hypothesized to be due to a lagged response in environmental concentrations compared to atmospheric concentrations.

Sex-specific associations between legacy and novel per- and polyfluoroalkyl substances and telomere length in newborns in Wuhan, China: Mixture and single pollutant associations

Telomere length (TL) at birth predicts later life TL and is related to health. Prenatal exposure to environmental pollutants might affect TL, but the associations between intrauterine per- and polyfluoroalkyl substances (PFASs) exposure and neonatal TL remained inconclusive. This study aimed to explore the single pollutant and mixture associations between legacy and novel PFASs and TL in newborns. In 908 mother-newborn pairs from Wuhan, China, thirteen PFASs were measured in cord serum, and TL was determined in cord leukocytes. Weighted quantile sum (WQS) regression and generalized linear model (GLM) were utilized to analyze the associations between PFASs mixture and single PFASs and TL in newborns. Furthermore, stratified and interaction analyses were performed to evaluate if there were sex-specific associations. The concentrations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) ranked the highest (geometric mean, 4.12, 1.61, and 0.77 ng/mL, respectively) among the 13 measured PFASs. Each unit increase in WQS index of PFASs mixture was associated with −5.19 % change (95% CI, −9.44, −0.73) of neonatal TL, and 8:2 Cl-PFESA contributed most (32.59 %) to the mixture association. In stratified analyses by neonatal sex, PFOS (−4.73 % change, 95% CI, −8.40, −0.93 for per doubling concentration) and 8:2 Cl-PFESA (−4.52 % change, 95% CI, −8.20, −0.70) were negatively associated with neonatal TL in male newborns, but no significant association appeared in females. In summary, intrauterine exposure to PFASs in mixture was associated with shorter neonatal TL, and the negative associations of 8:2 Cl-PFESA and PFOS with neonatal TL were observed only in boys. Future risk assessments are needed to pay more attention to the health effects of novel PFASs.

Gestational per- and polyfluoroalkyl substances exposure and infant body mass index trajectory in the New Hampshire Birth Cohort Study

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent, potential metabolic disruptors of concern for infants. Mothers participating in the New Hampshire Birth Cohort Study (NHBCS) provided a plasma sample during pregnancy to measure concentrations of seven PFAS, and infant weight and length were abstracted from well-child visits between birth and 12 months.Sex-specific growth patterns of child body mass index (BMI) were fit using a growth mixture model (GMM) and the relative risk ratios (RRR) and 95% Confidence Intervals (95% CI) for the association of maternal plasma PFAS with BMI growth patterns during infancy were estimated by using multinomial logistic model for the group probabilities in the GMM.Four growth patterns were identified: Group 1) a steep increase in BMI during the first 6 months, then a leveling off; Group 2) a gradual increase in BMI across the year; Group 3) a steep increase in BMI during months 1–3, then stable BMI; and Group 4) a gradual increase in BMI with plateau around 3 months (reference group). For boys, higher maternal pregnancy perfluorooctanoate concentrations were associated with a 60% decreased chance of being in group 3 as compared to group 4, after adjusting for potential confounding variables (RRR = 0.4; 95% CI: 0.1, 0.9). For girls, higher maternal perfluorooctane sulfonate (PFOS) concentrations during pregnancy were associated with a higher likelihood of following the growth pattern of groups 2 (RRR = 2.5; 95% CI: 1.0, 6.1) and 3 (RRR = 2.8; 95% CI: 1.0, 7.6) as compared to group 4, adjusting for potential confounding variables.In this cohort, sex-specific associations of maternal plasma PFAS concentrations during pregnancy with growth patterns during the first year of life were observed, with greater BMI growth observed among infant girls born to mothers with higher pregnancy concentrations of PFOS.

Exposure Trends and Half-lives of Per- and Polyfluoroalkyl Substances (PFAS) in Australian Firefighters

BACKGROUND AND AIM: Per- and polyfluoroalkyl substances (PFASs) are persistent manmade compounds used in aqueous film forming foam (AFFF). The extensive use of AFFF has led to widespread environmental PFAS contamination and exposures to firefighters. The aim of this study is to determine PFAS blood serum concentration trends and apparent serum elimination half-lives in firefighters after the replacement of AFFF. METHODS: Current and former employees of an Australian corporation providing aviation firefighting services, where AFFF had been used in the past, were recruited to participate in this study. Special focus was placed on re-recruiting participants who had provided blood samples five years prior. Participants were asked to provide a blood sample and complete a questionnaire. Serum samples were analysed for 40 different PFASs using HP LC-MS/MS. RESULTS: A total of 799 participants provided blood samples. Of these, 130 previously provided blood serum five years prior. Mean serum concentrations of perfluorooctane sulfonate (PFOS, 27 ng/mL), perfluoroheptane sulfonate (PFHpS, 1.7 ng/mL) and perfluorohexane sulfonate (PFHxS, 14 ng/mL) were significantly higher than the levels in the general Australian population. Serum concentrations were associated with the use of PFOS/PFHxS based AFFF. Participants who commenced service after the replacement of this foam had serum concentrations similar to those in the general Australian population. Average individual apparent half-lives were estimated to be 5.0 years (perfluorooctanoic acid (PFOA)), 7.8 years (PFHxS), 7.4 years (PFHpS) and 6.5 years (PFOS). CONCLUSIONS: This study shows how workplace interventions such as replacement of AFFF, can benefit employees at risk of occupational exposure. KEYWORDS: Biological Monitoring Occupational Exposure Firefighters Follow-Up Studies Half-Life

Elevated exposure to long-chain perfluoroalkyl and polyfluoroalkyl substances (PFAS) in Inuit from Nunavik, Arctic Canada: a call for global action

BACKGROUND AND AIM: The Inuit of Nunavik are exposed to perfluoroalkyl acids (PFAAs) via long-rang transport from southern to northern latitudes and biomagnification of PFAAs in Arctic food webs. Our objective was to document plasma PFAAs levels and compare them to previously documented levels and the general Canadian population. METHODS: The study included 1326 Nunavimmiut aged 16-82 years from the population representative survey, Qanuilirpitaa? 2017 Nunavik Inuit Health Survey. Concentrations of nine PFAAs were assessed, including perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUdA). Concentrations were compared to Nunavik levels in 2004, other Arctic regions, and the Canadian Health Measures Survey (CHMS) Cycle 5 2016-2017. Multiple linear regression analyses compared concentrations by demographics and lifestyle. RESULTS: There were elevated concentrations of various PFAAs congeners compared to CHMS, including PFOS, and long-chain PFAS congeners, PFNA, PFDA, and PFUnDA. PFNA and PFUdA concentrations were 7-fold higher than the CHMS concentrations, and PFDA concentrations were almost 4-fold higher than the CHMS concentrations. Short-chain congeners were largely undetected. Concentrations differed by sex, age, region, and indicators of seafood and marine mammal consumption. Males had higher concentrations of PFOA and PFHxS, whereas females had higher concentrations of PFDA and PFUdA. PFAAs concentrations increased with age and were highest among those aged 50+ years, such that serum PFOS concentrations were 2.5 times higher in those aged 50+ years compared to those aged 16-29 years. PFNA concentrations followed a U-shaped curve with increasing age. CONCLUSIONS: Our findings indicate a decrease in older PFAAs, but concentrations of many PFAAs in Nunavik remain several-fold higher compared to the general Canadian population. Evidence also points to an increase in exposure to long-chain PFAAs, which are an emerging public health concern in the Arctic. KEYWORDS: PFAS, Indigenous, Environmental justice, Exposure

Serum concentration trends and apparent half-lives of per- and polyfluoroalkyl substances (PFAS) in Australian firefighters.

Per- and polyfluoroalkyl substances (PFASs) are persistent manmade compounds used in aqueous film forming foam (AFFF). The extensive use of AFFF has led to widespread environmental PFAS contamination and exposures of firefighters. To determine PFAS blood serum concentration trends and apparent serum half-lives in firefighters after the replacement of AFFF. Current and former employees of an Australian corporation providing firefighting services, where AFFF formulations had been used since the 1980s up until 2010, were recruited in 2018-2019 to participate in this study. Special focus was put on re-recruiting participants who had provided blood samples five years prior (2013-2014). Participants were asked to provide a blood sample and fill in a questionnaire. Serum samples were analysed for 40 different PFASs using HP LC-MS/MS. A total of 799 participants provided blood samples in 2018-2019. Of these, 130 previously provided blood serum in 2013-2014. In 2018-2019, mean (arithmetic) serum concentrations of perfluorooctane sulfonate (PFOS, 27ng/mL), perfluoroheptane sulfonate (PFHpS, 1.7ng/mL) and perfluorohexane sulfonate (PFHxS, 14ng/mL) were higher than the levels in the general Australian population. Serum concentrations were associated with the use of PFOS/PFHxS based AFFF. Participants who commenced service after the replacement of this foam had serum concentrations similar to those in the general population. Mean (arithmetic) individual apparent half-lives were estimated to be 5.0 years (perfluorooctanoic acid (PFOA)), 7.8 years (PFHxS), 7.4 years (PFHpS) and 6.5 years (PFOS). This study shows how workplace interventions such as replacement of AFFF can benefit employees at risk of occupational exposure.

Glioma is associated with exposure to legacy and alternative per- and polyfluoroalkyl substances

Data on the occurrences of legacy and alternative per- and polyfluoroalkyl substances (PFASs) in glioma are scarce. It remains unclear if PFASs exposure is related to the prevalence of glioma. A total of 137 glioma and 40 non-glioma brain tissue samples from patients recruited from the Nanfang Hospital, South China were analyzed for 17 PFAS compounds. Perfluorohexanoic acid, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (FOSA), and 6:2 chlorinated polyfluorinated ether sulfonate were frequently detected (> 60 %) in glioma. The total concentrations (range; median) of 17 PFASs in glioma (0.20–140; 3.1 ng g−1) were slightly higher than those in non-glioma (0.35–32; 2.2 ng g−1), but without statistical significance. The PFAS concentrations in males were statistically higher (p < 0.05) than those in females. Elevated glioma grades were associated with higher concentrations of PFOA, PFOS, and FOSA. Positive correlations were observed between PFAS concentrations (especially for PFOA) and Ki-67 or P53 expression, pathological molecular markers of glioma. Our findings suggested that exposure to PFASs might increase the probability to develop glioma. This is the first case study demonstrating associations between PFASs exposure and brain cancer. More evidences and potential pathogenic mechanisms warranted further investigations.

Efficient decomposition of perfluorooctane sulfonate by hydrated electrons: Performance, mechanism, and carbon emission reduction

Perfluorooctane sulfonate (PFOS) is a typical perfluorinated compound, and the presence of sulfonic groups makes it difficult to decompose. In this study, ultraviolet photolysis of iodide (UV/KI) was conducted to generate hydrated electrons for PFOS decomposition, the key factors affecting the decomposition efficiency were investigated and the possible decomposition pathways were hypothesized. These results imply that the UV/KI system can effectively promote the decomposition and defluorination of PFOS. When the PFOS and KI concentrations were 0.03 mmol L−1 and 0.3 mmol L−1, respectively, the decomposition and defluorination efficiencies of PFOS at pH 10 reached 99.5 % and 94.8 % after 12 h of reaction, respectively. With the increase in KI concentration from 0.1 to 0.5 mmol L−1, the decomposition and defluorination efficiencies of PFOS increased; however, a further increase in KI will lead to a decrease in the performance. Weak and strong alkaline conditions are more favorable for PFOS decomposition than acidic conditions. Compared with the UV/Sulfite system, this system can be conducted under a lower concentration of hydrated electron source chemicals and a wider pH range. Kinetic analysis implied that PFOS decomposition followed the pseudo-first-order model with a reaction rate constant of 1.004 h−1, which was higher than most PFOS decomposition processes. Intermediate analysis and mass balance indicated that there were three PFOS decomposition pathways: desulfonation, H/F exchange, and CC bond dissociation. The main products were environmentally friendly fluoride ions, formic acid, and acetic acid, suggesting that the UV/KI system for PFOS decomposition is a relatively mild and green process.

Bioaccumulation and trophic transfer of perfluorinated alkyl substances (PFAS) in marine biota from the Belgian North Sea: Distribution and human health risk implications

Per- and polyfluorinated alkyl substances (PFAS) are highly persistent chemicals, which pose a potential risk for aquatic wildlife due to their bioaccumulative behaviour and toxicological effects. Although the distribution of PFAS in marine environments has been studied worldwide, little is known on the contamination of PFAS in the southern North Sea. In the present study, the bioaccumulation and trophic transfer of Perfluoroalkyl acids (PFAAs) was studied in liver and muscle tissue of seven fish species and in whole-body tissue of two crustacean species, collected at 10 sites in the Belgian North Sea. Furthermore, the human and ecological health risks were examined.Overall, perfluorooctane sulfonate (PFOS) was predominant in all matrices and other long-chain PFAS were frequently detected. Mean PFOS concentrations ranged from <LOQ to 107 ng/g (ww) in fish liver, from <LOQ to 24 ng/g ww in fish muscle and from 0.29 to 5.6 ng/g ww in crustaceans. Elevated perfluorotridecanoic acid (PFTrDA) concentrations were detected in fish liver from the estuarine and coastal region (<LOQ-116 ng/g ww), indicating a specific point source of this compound. Based on stable isotope analysis, no distinctive trophic transfer patterns of PFAS could be identified which implies that the bioconcentration of PFAS from the surrounding abiotic environment is most likely dominating over the biomagnification in the studied biota. The consumption of commercially important species such as the brown shrimp (Crangon crangon), plaice (Pleuronecta platessa), sole (Solea solea) and whiting (Merlangus merlangus) might pose potential health risks if it exceeds 17 g/day, 18 g/day, 26 g/day and 43 g/day respectively. Most PFOS measurements did not exceed the QSbiota,hh of 9.1 ng/g ww, however, the benchmark of 33 ng/g ww targeting the protection of wildlife from secondary poisoning was exceeded for 43% and 28% of the samples in plaice and sole.

Low power degradation of perfluorooctane sulfonate (PFOS) in water using a nanosecond pulsed atmospheric pressure plasma

The prevalence and persistence of perfluoroalkyl substances (PFAS) has led to significant concerns over the damage they can have on human health and the environment, particularly when they contaminate bodies of water. In this work, a plasma driven with high-voltage (20 kV) pulses of varying duration (50–400 ns) and frequency (0.5–10 kHz) is investigated for degrading perfluorooctane sulfonate (PFOS) in water. The concentration of PFOS in solution decreased with repeated passes through the reactor. Increasing the power consumption of the plasma, either by increasing the pulse width or the frequency, improved the rate of PFOS loss but decreased the energy efficiency. For instance, reducing the frequency of the pulse from 10 kHz to 500 Hz decreased the power consumption by over an order of magnitude while requiring about twice as much time to reduce 50% of the PFOS signal. Time-averaged emission spectroscopy showed that increasing the frequency decreased the average electron density of the plasma while infrared measurements indicate only a modest increase to the temperature of the reactor. In contrast, increasing the pulse width from 50 ns to 400 ns did not have a significant impact on the average electron density or the reactor temperature. Spectroscopy revealed the presence of photons with energies >5 eV which could contribute to PFOS loss. This work shows that the main factor determining PFOS loss is the contact time between the plasma reactor and the solution, which implies the most energy efficient operating parameters for PFOS degradation comes from minimizing the duration and frequency of the high-voltage pulses to reduce power consumption.

Cobalt-embedded nitrogen-doped carbon nanosheets with enhanced oxidase-like activity for detecting perfluorooctane sulfonate

In this study, we used leaf-like zeolitic imidazolate framework (ZIF-L) as the precursor, CoAc2⋅4H2O as the Co source, and 1,10-phenanthroline (Phen) as the N source to synthesize the cobalt-embedded nitrogen-carbon nanosheet (CoNCN) with enhanced enzyme-like activity. A variety of characterizations proved that the ultra-thin two-dimensional nanosheet structure of the CoNCN with both micropores and mesopores exposes more Co-Nx active sites, which makes it easier for the colorimetric substrate to contact the CoNCN’s surface. Compared with the Co-NC (the synthesized product without using Phen) and NC (the synthesized product without using CoAc2⋅4H2O) controls, the optimized CoNCN nanozyme exhibits 2.3-fold and 12.3-fold enhancement of oxidase-like activity, and 1.3-fold and 25.0-fold enhancement of catalase-like activity, respectively. In addition, the CoNCN has a high affinity for TMB, with a Km value of 0.53 mM and a Vmax value of 3.24 × 10-7 M s−1. The mechanism investigation indicated that the •OH, O2•− and 1O2 were reactive oxygen species responsible for the oxidase-like activity of CoNCN. The perfluorooctane sulfonate (PFOS) can fade the blue oxTMB. Based on this, an analytical method based on a colorimetric strategy coupled to classical univariate calibration was established for the sensitive detection of PFOS, with a linear range of 0.01 to 100 μM, and the limit of detection (LOD) of 20 nM according to modern IUPAC definition. The proposed method was successfully used to determine the concentration of PFOS in actual water samples.

Perfluorooctane sulfonate (PFOS) enhanced polystyrene particles uptake by human colon adenocarcinoma Caco-2 cells

As microplastics and nanoplastics (MNPs) are widely distributed in the environment and can be transferred to human body through food chain, their potential impact on human health is of great concern. Perfluorooctane sulfonate (PFOS) is persistent, bioaccumulative and can be adsorbed by MNPs. However, there are few studies on the combined human health effects of MNPs with PFOS. In this study, the effects of polystyrene (PS) particles and PFOS on human colon adenocarcinoma cell Caco-2 were investigated in vitro to explore the combined toxicity from cellular level, and the toxic mechanism was further illustrated. Results showed that the presence of PFOS significantly increased the cell uptake of PS nanoparticles by >30 %, which is related to variations of the surface properties of PS particles, including the decrease of hydration kinetic diameter, the rise of surface potential and the adsorption of hydrophobic PFOS molecules. The toxic effect of PFOS was weakened in the presence of PS particles under low PFOS concentration (10 μg/mL), which is because the bioavailability of PFOS was reduced after adsorption. PS particles with small particle size (20 nm) showed higher cell uptake and ROS production, while PS particles with large particle size (1 μm) led to higher lipid oxidation degree and related membrane damage as well as mitochondrial stress. This study provides the first evaluation of combined toxicity of MNPs and PFOS on human intestinal cells, in order to support the risk assessment of combined pollution of MNPs and PFOS on human health.

Background per- and polyfluoroalkyl substances (PFAS) in laboratory fish diet: Implications for zebrafish toxicological studies

Current attention is focused on determining the potential for per- and polyfluoroalkyl substances (PFAS) to adversely impact human health. Zebrafish are a popular biological model because they share early development pathways with humans. A dietary exposure paradigm is growing in popularity in the zebrafish model because the outcomes often translate to humans. To create a diet of known composition, it is crucial to understand background PFAS levels present in zebrafish diet. Background PFAS, if present, potentially confounds interpretation of toxicological data. To date, no studies document the PFAS background levels in laboratory fish diet and there is only limited information on some pet foods. The objective of this study was to develop and validate an analytical method for up to 50 target PFAS in high lipid and protein content laboratory fish diets and pet foods. Long-chain perfluoroalkyl carboxylic acids (C9-C13) and perfluorooctane sulfonate (PFOS) were quantified in 11 out of 16 laboratory fish diets and in three out of five pet fish foods. Foods for pet birds, lizards, and dogs were below the limit of detection for all PFAS. In two of the laboratory fish diets, PFOS concentrations were >1.3 ng/g and the total PFAS for the three laboratory fish diets exceeded 1.0 ng/g. Hundreds of biomedical laboratories across the world utilize these commercial laboratory fish diets, and these results indicate that numerous zebrafish colonies may be inadvertently receiving significant dietary PFAS exposures. In light of this new information, it is critical to design PFAS studies with appropriate controls with measured background PFAS concentrations in the diet and to urge caution when interpreting the results.

Coupling effects of tide and salting-out on perfluorooctane sulfonate (PFOS) transport and adsorption in a coastal aquifer

The adsorption of perfluorooctane sulfonate (PFOS) on sediments is thought to be enhanced by the ‘salting-out effect’ (SOE), which reduces contaminant solubility as water salinity increases. The process of salting-out has been observed for PFOS in surface estuaries and likely operates in ‘subterranean estuaries’, where tide-induced groundwater circulation creates a dynamic saltwater-freshwater mixing zone in the aquifer adjacent to the ocean. The presence of this dynamic interface between dense seawater and fresh groundwater modifies the flow path of land-derived organic contaminants. However, it is unclear how SOE combined with tidal forcing of salt water, affects the transport and fate of these contaminants in a subterranean estuary. Numerical studies of groundwater dynamics in a coastal aquifer are carried out using a modified version of SUTRA to investigate the behavior of PFOS, as it moves through an aquifer-ocean interface. Three adsorption scenarios are investigated: no adsorption and linear adsorption with a constant coefficient (Kd) and a salinity-dependent Kd (due to SOE). Without adsorption, point-injected PFOS moves and spreads as a plume around the margin of the tide-induced upper saline plume (USP). This is in agreement with previous studies showing that a contaminant plume follows the freshwater discharge path and exits the aquifer around the USP in the intertidal zone. The increase of tidal amplitude enlarges the USP, forcing the discharge points of freshwater and PFOS seaward. In the case of a constant Kd, PFOS concentration decreases in the groundwater as expected with an increase of PFOS residence time in the aquifer. The spatial distribution of the contaminant plume is similar to that of the ‘no adsorption’ case. In the case with the SOE, which enhances the solute adsorption in the saltwater zone, PFOS tends to be intercepted by the USP, concentrated at its center, and subsequently discharged with the tide-induced saltwater circulation. SOE reduces both peak PFOS discharge rate and plume dispersion. In addition, the PFOS flow path moves upward and the PFOS discharges above the USP. The findings highlight the potential importance of investigating the SOE of organic contaminants for benthic organisms when considering their transport and fate in tidally influenced coastal aquifers.