Fate and redistribution of perfluoroalkyl acids through AFFF-impacted groundwater

Impacts of Perfluoroalkyl Substances on Aqueous and Nonaqueous Phase Liquid Dechlorination by Sulfidized Nanoscale Zerovalent Iron

Per- and poly fluoroalkyl substances (PFASs) are often encountered with nonaqueous phase liquid (NAPL) in the groundwater at fire-fighting and military training sites. However, it is unclear how PFASs affect the dechlorination performance of sulfidized nanoscale zerovalent iron (S-nFe0), which is an emerging promising NAPL remediation agent. Here, S-nFe0 synthesized with controllable S speciation (FeS or FeS2) were characterized to assess their interactions with PFASs and their dechlorination performance for trichloroethylene NAPL (TCE-NAPL). Surface-adsorbed PFASs blocked materials' reactive sites and inhibited aqueous TCE dechlorination. In contrast, PFASs-adsorbed particles with improved hydrophobicity tended to enrich at the NAPL-water interface, and the reactive sites were re-exposed after the PFASs accumulation into the NAPL phase to accelerate dechlorination. This PFASs-induced phenomenon allowed the materials to present a higher reactivity (up to 1.8-fold) with a high electron efficiency (up to 99%) for TCE-NAPL dechlorination. Moreover, nFe0-FeS2 with a higher hydrophobicity was more readily enriched at the NAPL-water interface and more reactive and selective than nFe0-FeS, regardless of coexisting PFASs. These results unveil that a small amount of yet previously overlooked coexisting PFASs can favor selective reductions of TCE-NAPL by S-nFe0, highlighting the importance of materials hydrophobicity and transportation induced by S and PFASs for NAPL remediation.

Per- and polyfluoroalkyl substances (PFAS) as contaminants in groundwater resources - A comprehensive review of subsurface transport processes

Per- and polyfluorinated alkyl substances (PFAS) are persistent contaminants in the environment. An increased awareness of adverse health effects related to PFAS has further led to stricter regulations for several of these substances in e.g. drinking water in many countries. Groundwater constitutes an important source of raw water for drinking water production. A thorough understanding of PFAS subsurface fate and transport mechanisms leading to contamination of groundwater resources is therefore essential for management of raw water resources. A review of scientific literature on the subject of processes affecting subsurface PFAS fate and transport was carried out. This article compiles the current knowledge of such processes, mainly focusing on perfluoroalkyl acids (PFAA), in soil- and groundwater systems. Further, a compilation of data on transport parameters such as solubility and distribution coefficients, as well as, insight gained and conclusions drawn from the reviewed material are presented. As the use of certain fire-fighting foams has been identified as the major source of groundwater contamination in many countries, research related to this type of pollution source has been given extra focus. Uptake of PFAS in biota is outside the scope of this review. The review showed a large spread in the magnitude of distribution coefficients and solubility for individual PFAS. Also, it is clear that the influence of multiple factors makes site-specific evaluation of distribution coefficients valuable. This article aims at giving the reader a comprehensive overview of the subject, and providing a base for further work.

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

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

Pore size distribution and Al oxide content significantly regulated the effects of humic acid on perfluorooctanoic acid transport in natural soils

The ubiquity of dissolved organic matter (DOM) makes it encounter the released perfluorooctanoic acid (PFOA) in subsurface environment. However, the effect of DOM (e.g., humic acid, HA) on PFOA transport in soils and the critical influencing factors and mechanisms remain obscure. Column experiments were conducted to explore PFOA transport with the presence of different concentrations of HA in three types of soils and two types of Al oxide coated sand. Results revealed soil properties significantly regulate the effects of HA on PFOA transport, for which pore size distribution, minerals content (e.g., Al oxide) and pH were critical influencing soil-properties. For soil with large mesopore volume, pore blockage caused by HA controlled the effect of HA on PFOA transport. Large mesopore volume significantly alleviated pore blockage of HA, and led to insignificant effects of HA on PFOA transport. For soil exhibited minimum mesopore volume, Al oxide content and pH dominated the effect of HA on PFOA transport. Results from Al oxide coated sand (low mesopore volume) columns further proved that higher Al oxide content and lower pH caused more significant facilitating effect of HA on PFOA transport via site competition. Results highlighted the importance of considering pore size distribution and Al oxide content when assessing PFOA mobility capacity with co-transport with DOM in soils.

Association of per- and polyfluoroalkyl substances (PFAS) with periodontitis: the mediating role of sex hormones

OBJECTIVES

To investigate the association between serum per- and polyfluoroalkyl substances (PFAS) and periodontitis, and further explore the possible mediating role of sex hormones in this association.

METHODS

We extracted data from National Health and Nutrition Examination Survey (NHANES) 2009-2014. Univariable and multivariable logistic regression models were performed to investigate the association between serum levels of seven PFASs and periodontitis. Bayesian kernel machine regression (BKMR) was conducted to assess the joint effect of PFASs in mixtures. Mediation analyses were used to explore the potential mediating role of sex hormones.

RESULTS

Participants with periodontitis had higher concentrations of serum perfluorooctane sulfonate (PFOS) and perfluorononanoic acid (PFNA) than those without periodontitis (both P < 0.05). In fully adjusted models, high serum concentrations of PFOS and PFNA were positively associated with periodontitis (tertile 3 vs. tertile 1: prevalence ratio (PR) = 1.19 for PFOS, 95% CI: 1.01-1.39; PR = 1.17 for PFNA, 95% CI: 1.02-1.34). The results from the BKMR models consistently showed a positive association between PFAS mixtures and periodontitis. Of note, testosterone and the ratio of testosterone to estradiol significantly mediated the relationship between high level of PFOS and periodontitis, accounting for 16.5% and 31.7% of the total effect, respectively. Sensitivity analyses yielded similar results when using periodontal clinical indices (mean loss of attachment, mean periodontal probing depth, and the number of teeth) as dependent variables.

CONCLUSIONS

These findings provide evidence to support a positive association between certain PFASs and periodontitis, which might be partially mediated by sex hormones.

New PFASs Identified in AFFF Impacted Groundwater by Passive Sampling and Nontarget Analysis

Monitoring contamination from per- and polyfluoroalkyl substances (PFASs) in water systems impacted by aqueous film-forming foams (AFFFs) typically addresses a few known PFAS groups. Given the diversity of PFASs present in AFFFs, current analytical approaches do not comprehensively address the range of PFASs present in these systems. A suspect-screening and nontarget analysis (NTA) approach was developed and applied to identify novel PFASs in groundwater samples contaminated from historic AFFF use. A total of 88 PFASs were identified in both passive samplers and grab samples, and these were dominated by sulfonate derivatives and sulfonamide-derived precursors. Several ultrashort-chain (USC) PFASs (≤C3) were detected, 11 reported for the first time in Australian groundwater. Several transformation products were identified, including perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfinates (PFASis). Two new PFASs were reported (((perfluorohexyl)sulfonyl)sulfamic acid; m/z 477.9068 and (E)-1,1,2,2,3,3,4,5,6,7,8,8,8-tridecafluorooct-6-ene-1-sulfonic acid; m/z 424.9482). This study highlights that several PFASs are overlooked using standard target analysis, and therefore, the potential risk from all PFASs present is likely to be underestimated.

Impact of Variable Water Chemistry on PFOS-Goethite Interactions: Experimental Evidence and Surface Complexation Modeling

Perfluorooctanesulfonate (PFOS) has become a major concern due to its widespread occurrence in the environment and severe toxic effects. In this study, we investigate PFOS sorption on goethite surfaces under different water chemistry conditions to understand the impact of variable groundwater chemistry. Our investigation is based on multiple lines of evidence, including (i) a series of sorption experiments with varying pH, ionic strength, and PFOS initial concentration, (ii) IR spectroscopy analysis, and (iii) surface complexation modeling. PFOS was found to bind to goethite through a strong hydrogen-bonded (HB) complex and a weaker outer-sphere complex involving Na+ coadsorption (OS-Na+). The pH and ionic strength of the solution had a nontrivial impact on the speciation and coexistence of these surface complexes. Acidic conditions and low ionic strength promoted hydrogen bonding between the sulfonate headgroup and protonated hydroxo surface sites. Higher electrolyte concentrations and pH values hindered the formation of strong hydrogen bonds upon the formation of a ternary PFOS-Na+-goethite outer-sphere complex. The findings of this study illuminate the key control of variable solution chemistry on PFOS adsorption to mineral surfaces and the importance to develop surface complexation models integrating mechanistic insights for the accurate prediction of PFOS mobility and environmental fate.

Dynamic exposure and body burden models for per- and polyfluoroalkyl substances (PFAS) enable management of food safety risks in cattle

With increasing global focus on planetary boundaries, food safety and quality, the presence of per- and polyfluoroalkyl substances (PFAS) in the food chain presents a challenge for the sustainable production and supply of quality assured food. Consumption of food is the primary PFAS exposure route for the general population. At contaminated sites, PFAS have been reported in a range of agricultural commodities including cattle. Consumer exposure assessments are complicated by the lack of validated modelling approaches to estimate PFAS bioaccumulation in cattle. Previous studies have shown that PFAS bioaccumulation in livestock is influenced by environmental, spatial and temporal factors that necessitate a dynamic modelling approach. This work presents an integrated exposure and population toxicokinetic (PopTK) model for cattle that estimates serum and tissue concentrations of PFAS over time. Daily exposures were estimated from intakes of water, pasture, and soil, and considered animal growth, seasonal variability (pasture moisture content and temperature) and variable PFAS concentrations across paddocks. Modelled serum and tissue estimates were validated against monitoring data from Australian and Swedish cattle farms. The models were also used to develop and test practical management options for reducing PFAS exposure and to prioritise remediation for farms. Model outputs for exposure management scenarios (testing cattle rotation and targeted supplementation of feed and water) showed potential for marked reductions in consumer exposures from cattle produce.

Novel Per- and Polyfluoroalkyl Substances Discovered in Cattle Exposed to AFFF-Impacted Groundwater

The leaching of per- and polyfluoroalkyl substances (PFASs) from Australian firefighting training grounds has resulted in extensive contamination of groundwater and nearby farmlands. Humans, farm animals, and wildlife in these areas may have been exposed to complex mixtures of PFASs from aqueous film-forming foams (AFFFs). This study aimed to identify PFAS classes in pooled whole blood (n = 4) and serum (n = 4) from cattle exposed to AFFF-impacted groundwater and potentially discover new PFASs in blood. Thirty PFASs were identified at various levels of confidence (levels 1a-5a), including three novel compounds: (i) perfluorohexanesulfonamido 2-hydroxypropanoic acid (FHxSA-HOPrA), (ii) methyl((perfluorohexyl)sulfonyl)sulfuramidous acid, and (iii) methyl((perfluorooctyl)sulfonyl)sulfuramidous acid, belonging to two different classes. Biotransformation intermediate, perfluorohexanesulfonamido propanoic acid (FHxSA-PrA), hitherto unreported in biological samples, was detected in both whole blood and serum. Furthermore, perfluoroalkyl sulfonamides, including perfluoropropane sulfonamide (FPrSA), perfluorobutane sulfonamide (FBSA), and perfluorohexane sulfonamide (FHxSA) were predominantly detected in whole blood, suggesting that these accumulate in the cell fraction of blood. The suspect screening revealed several fluoroalkyl chain-substituted PFAS. The results suggest that targeting only the major PFASs in the plasma or serum of AFFF-exposed mammals likely underestimates the toxicological risks associated with exposure. Future studies of AFFF-exposed populations should include whole-blood analysis with high-resolution mass spectrometry to understand the true extent of PFAS exposure.

Perfluorohexanesulfonic acid (PFHxS) induces oxidative stress and causes developmental toxicities in zebrafish embryos

Perfluorohexanesulfonic acid (PFHxS) is a short-chain perfluoroalkyl substance widely used to replace the banned perfluorooctanesulfonic acid (PFOS) in different industrial and household products. It has currently been identified in the environment and human bodies; nonetheless, the possible toxicities are not well-known. Zebrafish have been used as a toxicant screening model due to their fast and transparent developmental processes. In this study, zebrafish embryos were exposed to PFHxS for five days, and various experiments were performed to monitor the developmental and cellular processes. Liquid chromatography-mass spectrometry (LC/MS) analysis confirmed that PFHxS was absorbed and accumulated in the zebrafish embryos. We reported that 2.5 µM or higher PFHxS exposure induced phenotypic abnormalities, marked by developmental delay in the mid-hind brain boundary and yolk sac edema. Additionally, larvae exposed to PFHxS displayed facial malformation due to the reduction of neural crest cell expression. RNA sequencing analysis further identified 4643 differentiated expressed transcripts in 5 µM PFHxS-exposed 5-days post fertilization (5-dpf) larvae. Bioinformatics analysis revealed that glucose metabolism, lipid metabolism, as well as oxidative stress were enriched in the PFHxS-exposed larvae. To validate these findings, a series of biological experiments were conducted. PFHxS exposure led to a nearly 4-fold increase in reactive oxygen species, possibly due to hyperglycemia and impaired glutathione balance. The Oil Red O' staining and qPCR analysis strengthens the notions that lipid metabolism was disrupted, leading to lipid accumulation, lipid peroxidation, and malondialdehyde formation. All these alterations ultimately affected cell cycle events, resulting in S and G2/M cell cycle arrest. In conclusion, our study demonstrated that PFHxS could accumulate and induce various developmental toxicities in aquatic life, and such data might assist the government to accelerate the regulatory policy on PFHxS usage.

Spatial and temporal variability of per- and polyfluoroalkyl substances (PFAS) in environmental media of a small pond: Toward an improved understanding of PFAS bioaccumulation in fish

Per- and polyfluoroalkyl substances (PFAS) are highly fluorinated compounds with many industrial applications, for instance as ingredients in fire-suppressing aqueous film-forming foams (AFFF). Several PFAS have been demonstrated to be persistent, bioaccumulative and toxic. This study better characterizes the bioaccumulation of PFAS in freshwater fish through a spatial and temporal analysis of surface water and sediment from a stormwater pond in a former Naval air station (NAS) with historic AFFF use. We sampled environmental media from four locations twice per week for five weeks and sampled fish at the end of the sampling effort. The primary PFAS identified in surface water, sediment, and biota were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) followed by perfluorooctanoic acid (PFOA) in environmental media and perfluoroheptane sulfonate (PFHpS) in biota. We observed significant temporal variability in surface water concentrations at the pond headwaters following stochastic events such as heavy rainfall for many compounds, particularly PFHxS. Sediment concentrations varied most across sampling locations. In fish, liver tissue presented the highest concentrations for all compounds except PFHxS, which was highest in muscle tissue, suggesting the influence of fine-scale aqueous PFAS fluctuations on tissue distribution. Calculated log bioaccumulation factors (BAFs) ranged from 0.13 to 2.30 for perfluoroalkyl carboxylates (PFCA) and 0.29-4.05 for perfluoroalkane sulfonates (PFSA) and fluctuated greatly with aqueous concentrations. The variability of PFAS concentrations in environmental media necessitates more frequent sampling efforts in field-based studies to better characterize PFAS contamination in aquatic ecosystems as well as exercising caution when considering single time-point BAFs due to uncertainty of system dynamics.

Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium Is Not Inhibited by Perfluoroalkyl Acids (PFAAs) at Field-Relevant Concentrations

Perfluoroalkyl acids (PFAAs) have been shown to inhibit biodegradation (i.e., organohalide respiration) of chlorinated ethenes. The potential negative impacts of PFAAs on microbial species performing organohalide respiration, particularly Dehalococcoides mccartyi (Dhc), and the efficacy of in situ bioremediation are a critical concern for comingled PFAA-chlorinated ethene plumes. Batch reactor (no soil) and microcosm (with soil) experiments, containing a PFAA mixture and bioaugmented with KB-1, were completed to assess the impact of PFAAs on chlorinated ethene organohalide respiration. In batch reactors, PFAAs delayed complete biodegradation of cis-1,2-dichloroethene (cis-DCE) to ethene. Maximum substrate utilization rates (a metric for quantifying biodegradation rates) were fit to batch reactor experiments using a numerical model that accounted for chlorinated ethene losses to septa. Fitted values for cis-DCE and vinyl chloride biodegradation were significantly lower (p < 0.05) in batch reactors containing ≥50 mg/L PFAAs. Examination of reductive dehalogenase genes implicated in ethene formation revealed a PFAA-associated change in the Dhc community from cells harboring the vcrA gene to those harboring the bvcA gene. Organohalide respiration of chlorinated ethenes was not impaired in microcosm experiments with PFAA concentrations of 38.7 mg/L and less, suggesting that a microbial community containing multiple strains of Dhc is unlikely to be inhibited by PFAAs at lower, environmentally relevant concentrations.

Spatio-temporal trends in livestock exposure to per- and polyfluoroalkyl substances (PFAS) inform risk assessment and management measures

The migration of per- and polyfluoroalkyl substances (PFAS) onto agricultural properties has resulted in the accumulation of PFAS in livestock. The environmental determinants of PFAS accumulation in livestock from the grazing environment are poorly understood, resulting in limited capacity to manage livestock exposure and subsequent transfer of PFAS through the food chain. Analytical- (n = 978 samples of soil, water, pasture, and serum matrices), farm management/practice- and livestock physiology data were collated and interrogated from environmental PFAS investigations across ten farms, from four agro-ecological regions of Victoria (Australia). Statistical analysis identified perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) as key analytes of concern for livestock bioaccumulation. PFOS and PFHxS concentrations in livestock drinking water were positively correlated with serum concentrations while other intake pathways (pasture and soil) had weaker correlations. Seasonal trends in PFAS body burden (serum concentrations) were identified and suggested to be linked to seasonal grazing behaviours and physiological water requirements. The data showed for the first time that livestock exposure to PFAS is dynamic and with relatively short elimination half-lives, there is opportunity for exposure management. Meat from cattle, grazed on PFAS impacted sites, may exceed health-based guideline values for PFAS, especially for markets with low limits (like the European Commission Maximum Limits or EC MLs). This study found that sites with mean livestock drinking water concentrations as low as 0.003 μg PFOS/L may exceed the EC ML for PFOS in cattle meat. Risk assessment can be used to prioritise site cleanup and development of management plans to reduce PFAS body burden by considering timing of stock rotation and/or supplementation of primary exposure sources.

Using foam fractionation to estimate PFAS air-water interface adsorption behaviour at ng/L and µg/L concentrations

PFAS are biologically recalcitrant compounds that are persistent in the environment and have subsequently contaminated groundwater, landfill leachate and surface water. Due to their persistence and toxicity, there are environmental concentration limits imposed on some PFAS compounds that extend down to a few nanograms per litre and even proposals for reducing these to picogram per litre levels. Since PFAS concentrates at water-air interfaces as a result of their amphiphilic nature, this characteristic is important for the successful modelling and prediction of transport behaviour of PFAS through various systems. Here we present a procedure for using a foam fractionation method to experimentally determine the PFAS adsorption behaviour at ng/L and µg/L concentrations in the presence of salts. The equilibrium air-water adsorption coefficients for PFHxS and PFOA at different salinities and concentrations are experimentally shown to be constant across the range of PFAS concentrations investigated (approx. 0.1-100 µg/L). The adsorption isotherms may consequently be modelled by Henry or Langmuir style equations at these low concentrations.

Preferential Retention and Transport of Perfluorooctanesulfonic Acid in a Dolomite Aquifer

Per- and polyfluoroalkyl substances (PFAS) can represent a significant human health risk if present in aquifers used as a drinking water source. Accurate assessment of PFAS exposure risks requires an improved understanding of field-scale PFAS transport in groundwater. Activities at a former firefighter training site in University Park, Pennsylvania introduced perfluorooctanesulfonic acid (PFOS) to the underlying dolomite aquifer. Groundwater sampling from 2015 to 2018 delineated a PFOS plume with two concentration maxima located approximately 20 and approximately 220 m downgradient of the training site, separated by a zone of lower concentrations. We use a combination of analytical and numerical models, informed by independent measurements of aquifer porosity, hydraulic conductivity, and organic carbon content, to interpret the field observations. Our analysis demonstrates that preferential retention and transport resulting from simple heterogeneity in bedrock sorption, as caused by organic carbon (OC) content variability, provides a plausible explanation for plume separation. Dissolved PFOS partitions strongly to organic solids (high K_oc ), so even a small OC (<1 wt%) significantly retards PFOS transport, whereas zones with little to no OC allow for transport rates that approximate those of a conservative solute. Our work highlights an important consideration for modeling the groundwater transport of PFOS, and other compounds with high K_oc . In aquifers with discrete layers of varying OC, models using a uniform site-average OC will underestimate transport distances, thereby misrepresenting exposure risks for downgradient communities.

The efficacy of soil washing for the remediation of per- and poly-fluoroalkyl substances (PFASs) in the field

This paper aims to describe the performance of a soil washing plant (SWP) for remediating a per- and poly-fluoroalkyl substances (PFASs)-contaminated soil with a high clay content (61%). The SWP used both physical and chemical processes; fractionation of the soil particles by size and partitioning of PFASs into the aqueous phase to remove PFASs from the soil. Contaminated water was treated in series with granulated activated carbon (GAC) and ion-exchange resin and reused within the SWP. Approximately 2200 t (dry weight) of PFAS-contaminated soil was treated in 25 batches of 90 t each, with a throughput of approximately 11 t soil/hr. Efficiency of the SWP was measured by observed decreases in total and leachable concentrations of PFASs in the soil. Average removal efficiencies (RE) were up to 97.1% for perfluorocarboxylic acids and 94.9% for perfluorosulfonic acids. REs varied among different PFASs depending on their chemistry (functional head group, carbon chain length) and were independent of the total PFAS concentrations in each soil batch. Mass balance analysis found approximately 90% of the PFAS mass in the soil was transferred to the wash solution and > 99.9% of the PFAS mass in the wash solution was transferred onto the GAC without any breakthrough.

Effect of different co-foaming agents on PFAS removal from the environment by foam fractionation

Per- and poly-fluoroalkyl substances (PFAS) are recalcitrant, synthetic chemicals that are ubiquitous in the environment because of their widespread use in a variety of consumer and industrial products. PFAS contamination has become an increasing issue in recent years, which needs to be urgently addressed. Foam fractionation is emerging as a potential remediation option that removes PFAS by adsorption to the surface of rising air bubbles which are removed from the system as a foam. PFAS concentrations in the environment are often not sufficient to allow for formation of a foam by itself and often a co-foaming agent is required to be added to enhance the foamability of the solution. In this study, the effect of different classes of co-foaming agents, anionic, non-ionic, zwitterionic and cationic surfactants on the removal of PFAS with varying fluorocarbon chain length from 3 to 8 in a foam fractionation process have been investigated. Evaluation of the air-water interface partitioning coefficient (k') in addition with surface tension and PFAS removal results support the contention that using a co-foaming agent with the opposite charge to the PFAS in question significantly facilitates the adsorption of PFAS to the air-water interface, enhancing the efficiency of the process. Using the non-ionic surfactant (no headgroup electrostatic interaction with PFAS), as a reference, it was observed, in terms of PFAS separation and rate of PFAS removal, that anionic co-surfactant performed worst, zwitterionic was better, and cationic co-surfactant performed best. All of the PFAS species were able to be removed below the limit of detection (0.05 µg/L) after 45 minutes of foaming time with the cationic surfactant.

Longitudinal measurements of per- and poly-fluoroalkyl substances (PFAS) in archived human serum samples between 1975 and 1995 in Australia

Per- and poly-fluoroalkyl substances (PFAS) are a group of manmade compounds produced since the 1950 s and used in a range of industrial processes and consumer products. In Australia, PFAS serum concentrations have been measured in the general population since 2002. However, few studies have retrospectively measured PFAS concentrations in serum samples representative of a general population prior to 2000, none of which have been conducted in Australia. To understand the general population's exposure to PFAS prior to 2002, longitudinal PFAS serum concentration measurements are required. In the current study, we accessed 'The Busselton Health Study Data Bank' to analyse archived serum samples for PFAS. Repeat serum samples collected in 1975, 1981 and 1995 were obtained from 17 participants. Of the 35 PFAS analysed, 13 PFAS were detected in the serum samples collected in 1975. Both the detection frequency and ∑PFAS serum concentrations increased between 1975 and 1995. Median ∑PFAS serum concentration increased over 7-fold; from 3.3 ng/mL in 1975-26 ng/mL in 1995. The increase in serum concentrations reflects the global production history of these PFAS during this period in time.

Relative rates of cancers and deaths in Australian communities with PFAS environmental contamination associated with firefighting foams: A cohort study using linked data

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants that are potentially harmful to health. We examined if rates of selected cancers and causes of deaths were elevated in three Australian communities with local environmental contamination caused by firefighting foams containing PFAS. The affected Australian communities were Katherine in Northern Territory, Oakey in Queensland and Williamtown in New South Wales.

METHODS

All residents identified in the Medicare Enrolment File (1983-2019)-a consumer directory for Australia's universal healthcare-who ever lived in an exposure area (Katherine, Oakey and Williamtown), and a sample of those who ever lived in selected comparison areas, were linked to the Australian Cancer Database (1982-2017) and National Death Index (1980-2019). We estimated standardised incidence ratios (SIRs) for 23 cancer outcomes, four causes of death and three control outcomes, adjusting for sex, age and calendar time of diagnosis.

FINDINGS

We observed higher rates of prostate cancer (SIR=1·76, 95 % confidence interval (CI) 1·36-2·24) in Katherine; laryngeal cancer (SIR=2·71, 95 % CI 1·30-4·98), kidney cancer (SIR=1·82, 95 % CI 1·04-2·96) and coronary heart disease (CHD) mortality (SIR=1·81, 95 % CI 1·46-2·33) in Oakey; and lung cancer (SIR=1·83, 95 % CI 1·39-2·38) and CHD mortality (SIR=1·22, 95 % CI 1·01-1·47) in Williamtown. We also saw elevated SIRs for control outcomes. SIRs for all other outcomes and overall cancer were similar across exposure and comparison areas.

INTERPRETATION

There was limited evidence to support an association between living in a PFAS exposure area and risks of cancers or cause-specific deaths.

Boosting degradation and defluorination efficiencies of PFBS in a vacuum-ultraviolet/S(Ⅳ) process with iodide involvement

Perfluorobutane sulfonate (PFBS) is considered to be a promising alternative of perfluorooctane sulfonates (PFOS), while it is also hazardous. The UV/S (Ⅳ) system has been confirmed to be effective for PFOS removal from water, while it is inefficient for PFBS decomposition. A hybrid vacuum-ultraviolet (VUV)/S (Ⅳ)/KI process was investigated for the degradation of PFBS in aqueous solution. With KI involvement, the degradation rate of PFBS was boosted from 1.8802 μg h^-1 up to 3.5818 μg h^-1 in the VUV/S (Ⅳ) process. Alkaline conditions significantly increased the degradation efficiency of PFBS, which can be explained that S (Ⅳ) was dominated by SO₃^2- rather than HSO₃^- and H₂SO₃ in alkaline conditions. Cl^-, HCO₃^-, NO₃^-, NO₂^-, and HA would inhibit the performance of the VUV/S (Ⅳ)/KI process via various reactions. In addition, the toxicity of PFBS was significantly reduced by the VUV/S (Ⅳ)/KI process. Even in actual waters, the VUV/S (Ⅳ)/KI process also presented a satisfying performance in the degradation of PFBS.

PFASs in Soil: How They Threaten Human Health through Multiple Pathways and Whether They Are Receiving Adequate Concern

Per- and polyfluoroalkyl substances (PFASs) have been mass-produced and widely applied in consumer and industrial products, resulting in their widespread presence in the environment. Features such as environmental persistence, bioaccumulation, and high toxicity even at low doses have made PFASs an increasing concern. This brief review focuses on soil PFASs, especially the effect of soil PFASs on other environmental media and their potential threats to human health through daily diet. Specifically, soil PFASs contamination caused by different pathways was first investigated. Soil pollution from application of aqueous film-forming foams (AFFFs) is generally more severe than that from fluorochemical manufacturing plants, followed by biosolid land use, landfill, and irrigation. Factors, such as carbon chain length of PFASs, wastewater treatment technology, geographical conditions, and regional development level, are related to soil PFASs' pollution. Then, the migration, bioaccumulation, and toxicity characteristics of soil PFASs were analyzed. Short-chain PFASs have higher solubility, mobility, and bioavailability, while long-chain PFASs have higher bioaccumulation potential and are more toxic to organisms. Factors such as soil texture, solution chemistry conditions, enzymes, and fertilization conditions also influence the environmental behavior of PFASs. The risk of human exposure to PFASs through agricultural and animal products is difficult to control and varies depending on living region, age, eating habits, lifestyle, ethnicity, etc. Soil PFASs threaten drinking water safety, affect soil function, and enter food webs, threatening human health. Knowledge gaps and perspectives in these research fields are also included in current work to assist future research to effectively investigate and understand the environmental risks of soil PFASs, thereby reducing human exposure.

Plasma and Skin Per- and Polyfluoroalkyl Substance (PFAS) Levels in Dairy Cattle with Lifetime Exposures to PFAS-Contaminated Drinking Water and Feed

Plasma and ear notch samples were removed from 164 Holstein cows and heifers, which had lifetime exposures to per- and polyfluoroalkyl substances (PFAS) through consumption of contaminated feed and water sources. A suite of nine PFAS including five perfluoroalkyl carboxylic acids (PFCA) and four perfluoroalkyl sulfonic acids (PFSA) was quantified in plasma and ear notch samples by liquid chromatography-mass spectrometry. Bioaccumulation of four- to nine-carbon PFCAs did not occur in plasma or skin, but PFSAs longer than four carbons accumulated in both plasma and skin. Exposure periods of at least 1 year were necessary for PFSAs to reach steady-state concentrations in plasma. Neither parity (P = 0.76) nor lactation status (P = 0.30) affected total PFSA concentrations in mature cow plasma. In contrast, lactation status greatly affected (P < 0.0001) total PFSA concentrations in ear notch samples. Skin samples could be used for biomonitoring purposes in instances when on-farm blood collection and plasma preparation are not practical.

Global distributions, source-type dependencies, and concentration ranges of per- and polyfluoroalkyl substances in groundwater

A meta-analysis was conducted of published literature reporting concentrations of per- and polyfluoroalkyl substances (PFAS) in groundwater for sites distributed in 20 countries across the globe. Data for >35 PFAS were aggregated from 96 reports published from 1999 to 2021. The final data set comprises approximately 21,000 data points after removal of time-series and duplicate samples as well as non-detects. The reported concentrations range over many orders of magnitude, from ng/L to mg/L levels. Distinct differences in concentration ranges are observed between sites located within or near sources versus those that are not. Perfluorooctanoic acid (PFOA), ranging from <0.03 ng/L to ~7 mg/L, and perfluorooctanesulfonic acid (PFOS), ranging from 0.01 ng/L to ~5 mg/L, were the two most reported PFAS. The highest PFAS concentration in groundwater is ~15 mg/L reported for the replacement-PFAS 6:2 fluorotelomer sulfonate (6:2 FTS). Maximum reported groundwater concentrations for PFOA and PFOS were compared to concentrations reported for soils, surface waters, marine waters, and precipitation. Soil concentrations are generally significantly higher than those reported for the other media. This accrues to soil being the primary entry point for PFAS release into the environment for many sites, as well as the generally significantly greater retention capacity of soil compared to the other media. The presence of PFAS has been reported for all media in all regions tested, including areas that are far removed from specific PFAS sources. This gives rise to the existence of a "background" concentration of PFAS that must be accounted for in both regional and site-specific risk assessments. The presence of this background is a reflection of the large-scale use of PFAS, their general recalcitrance, and the action of long-range transport processes that distribute PFAS across regional and global scales. This ubiquitous distribution has the potential to significantly impact the quality and availability of water resources in many regions. In addition, the pervasive presence of PFAS in the environment engenders concerns for impacts to ecosystem and human health.

Per- and polyfluoroalkyl substance (PFAS) retention by colloidal activated carbon (CAC) using dynamic column experiments

Developing effective remediation methods for per- and polyfluoroalkyl substance (PFAS)-contaminated soils is a substantial step towards counteracting their widespread occurrence and protecting our ecosystems and drinking water sources. Stabilisation of PFAS in the subsurface using colloidal activated carbon (CAC) is an innovative, yet promising technique, requiring better understanding. In this study, dynamic soil column tests were used to assess the retardation of 10 classical perfluoroalkyl acids (PFAAs) (C₅-C₁₁ perfluoroalkyl carboxylic acids (PFCAs) and C₄, C₆, C₈ perfluoroalkane sulfonates (PFSAs)) as well as two alternative PFAS (6:2 and 8:2 fluorotelomer sulfonates) using CAC at 0.03% w/w, to investigate the fate and transport of PFAS under CAC treatment applications. Results showed high retardation rates for long-chain PFAS and eight times higher retardation for the CAC-treated soil compared to the non-treated reference soil for the ∑PFAS. Replacement of shorter chain perfluorocarboxylic acids (PFCAs), such as perfluoropentanoic acid (PFPeA), by longer chained PFAS was observed, indicating competition effects. Partitioning coefficients (K_d values) were calculated for the CAC fraction at ∼10³-10⁵ L kg^-1 for individual PFAS, while there was a significant positive correlation (p < 0.05) between perfluorocarbon chain length and K_d. Mass balance calculations showed 37% retention of ∑PFAS in treated soil columns after completion of the experiments and 99.7% higher retention rates than the reference soil. Redistribution and elution of CAC were noticed and quantified through organic carbon analysis, which showed a 23% loss of carbon during the experiments. These findings are a step towards better understanding the extent of CAC's potential for remediation of PFAS-contaminated soil and groundwater and the limitations of its applications.

Current and future federal and state sampling guidance for per- and polyfluoroalkyl substances in environmental matrices

Per- and polyfluoroalkyl substances (PFAS) are a class of emerging contaminants composed of an estimated 5000 to 10,000 human-made, fluorinated, organic chemicals. Due to the complexity of PFAS, the need for multiple environmental matrix considerations and the absence of a promulgated federal standard for environmental sampling and analysis, U.S. states have begun developing health-based regulatory and/or guidance values for a limited number of PFAS in environmental matrices. As there is a growing body of science to inform PFAS sampling guidance standard development, it is important to understand which U.S. states are implementing sampling guidelines and how they plan to handle emerging PFAS. This critical review discusses the current and impending federal and state sampling guidelines for PFAS in environmental matrices, the data gaps surrounding PFAS sampling guidance in U.S. states, and the future impacts of impending guidance documents and regulations. Ten federal guidance documents are available for PFAS sampling guidance and analysis. The maximum number of PFAS covered in these guidance documents is 25 analytes spanning across 8 unique media. While the EPA has developed several different sampling and analytical guidelines for PFAS, there is no formal regulation of PFAS or requirements of states to enforce these guidelines. As a result, only 31 states have informally adopted sampling guidelines, while the other 19 states have no guidance documentation in place for PFAS. The introduction of new PFAS sampling guidelines by the EPA, as well as updated analytical guidelines that target more PFAS or total organofluoride, is expected to continuously shift the landscape of federal and state guidance for PFAS sampling moving forward.

Persistent organic pollutants in foods, their interplay with gut microbiota and resultant toxicity

Persistent Organic Pollutants (POPs) have become immensely prevalent in the environment as a result of their unique chemical properties (persistent, semi-volatile and bioaccumulative nature). Their occurrence in the soil, water and subsequently in food has become a matter of concern. With food being one of the major sources of exposure, the detrimental impact of these chemicals on the gut microbiome is inevitable. The gut microbiome is considered as an important integrant for human health. It participates in various physiological, biochemical and immunological activities; thus, affects the metabolism and physiology of the host. A myriad of studies have corroborated an association between POP-induced gut microbial dysbiosis and prevalence of disorders. For instance, ingestion of polychlorinated biphenyls, polybrominated diphenyl ethers or organochlorine pesticides influenced bile acid metabolism via alteration of bile salt hydrolase activity of Lactobacillus, Clostridium or Bacteroides genus. At the same time, some chemicals such as DDE have the potential to elevate Proteobacteria and Firmicutes/Bacteriodetes ratio influencing their metabolic activity leading to enhanced short-chain fatty acid synthesis, ensuing obesity or a pre-diabetic state. This review highlights the impact of POPs exposure on the gut microbiota composition and metabolic activity, along with an account of its corresponding consequences on the host physiology. The critical role of gut microbiota in impeding the POPs excretion out of the body resulting in their prolonged exposure and consequently, enhanced degree of toxicity is also emphasized.

Efficient decomposition of perfluorooctane sulfonate by electrochemical activation of peroxymonosulfate in aqueous solution: Efficacy, reaction mechanism, active sites, and application potential

The electrochemical oxidation method is a promising technology for the degradation of perfluorooctane sulfonate (PFOS). However, the elimination processes of PFOS are still unknown, including the electron transfer pathway, key reactive sites, and degradation mechanism. Here, we fabricated diatomite and cerium (Ce) co-modified Sb₂O₃ (D-Ce/Sb₂O₃) anode to realize efficient degradation of PFOS via peroxymonosulfate (PMS) activation. The transferred electron and the generated hydroxyl radical (•OH) can high-effectively decompose PFOS. The electron can be rapidly transferred from the highest occupied molecular orbital of the PFOS to the lowest unoccupied molecular orbital of the PMS via the D-Ce/Sb₂O₃ driven by a potential energy difference under electrochemical process. The active site of Ce-O in the D-Ce/Sb₂O₃ can greatly reduce the migration distance of the electron and the •OH, and thus improving the catalytic activity for degrading various organic micropollutants with high stability. In addition, the electrochemical process shows strong resistance and tolerance to the changing pH, inorganic ions, and organic matter. This study offers insights into the electron transfer pathway and PMS activation mechanism in PFOS removal via electrochemical oxidation, paving the way for its potential application in water purification.

Assessment of Mobilization Potential of Per- and Polyfluoroalkyl Substances for Soil Remediation

This study investigated the mobilization of a wide range of per- and polyfluoroalkyl substances (PFASs) present in aqueous film-forming foams (AFFFs) in water-saturated soils through one-dimensional (1-D) column experiments with a view to assessing the feasibility of their remediation by soil desorption and washing. Results indicated that sorption/desorption of most of the shorter-carbon-chain PFASs (C ≤ 6) in soil reached greater than 99% rapidly─after approximately two pore volumes (PVs) and were well predicted by an equilibrium transport model, indicating that they will be readily removed by soil washing technologies. In contrast, the equilibrium model failed to predict the mobilization of longer-chain PFASs (C ≥ 7), indicating the presence of nonequilibrium sorption/desorption (confirmed by a flow interruption experiment). The actual time taken to attain 99% sorption/desorption was up to 5 times longer than predicted by the equilibrium model (e.g., ∼62 PVs versus ∼12 PVs predicted for perfluorooctane sulfonate (PFOS) in loamy sand). The increasing contribution of hydrophobic interactions over the electrostatic interactions is suggested as the main driving factor of the nonequilibrium processes. The inverse linear relationship (R² = 0.6, p < 0.0001) between the nonequilibrium mass transfer rate coefficient and the Freundlich sorption coefficient could potentially be a useful means for preliminary evaluation of potential nonequilibrium sorption/desorption of PFASs in soils.

Electrochemical oxidation processes for PFAS removal from contaminated water and wastewater: fundamentals, gaps and opportunities towards practical implementation

Electrochemical oxidation (EO) is emerging as one of the most promising methods for the degradation of recalcitrant per- and poly-fluoroalkyl substances (PFASs) in water and wastewater, as these compounds cannot be effectively treated with conventional bio- or chemical approaches. This review examines the state of the art of EO for PFASs destruction, and comprehensively compares operating parameters and treatment performance indicators for both synthetic and real contaminated water and wastewater media. The evaluation shows the need to use environmentally-relevant media to properly quantify the effectiveness/efficiency of EO for PFASs treatment. Additionally, there is currently a lack of quantification of sorption losses, resulting in a likely over-estimation of process' efficiencies. Furthermore, the majority of experimental results to date indicate that short-chain PFASs are the most challenging and need to be prioritized as environmental regulations become more stringent. Finally, and with a perspective towards practical implementation, several operational strategies are proposed, including processes combining up-concentration followed by EO destruction.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in groundwater: current understandings and challenges to overcome

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been frequently detected in groundwater globally. With the phase-out of perfluorooctane sulfonate (PFOS) and perfluorooctanate (PFOA) due to their risk to the ecosystem and human population, various novel PFASs have been used as replacements and detected in groundwater. In order to summarize the current understanding and knowledge gaps on PFASs in groundwater, we reviewed the studies about environmental occurrence, transport, and risk of legacy and novel PFASs in groundwater published from 1999 to 2021. Our review suggests that PFOS and PFOA could still be detected in groundwater due to the long residence time and the retention in the soil-groundwater system. Firefighting training sites, industrial parks, and landfills were commonly hotspots of PFASs in groundwater. More novel PFASs have been detected via nontarget analysis using high-resolution mass spectrometry. Some novel PFASs had concentrations comparable to that of PFOS and PFOA. Both legacy and novel PFASs can pose a risk to human population who rely on contaminated groundwater as drinking water. Transport of PFASs to groundwater is influenced by various factors, i.e., the compound structure, the hydrochemical condition, and terrain. The exchange of PFASs between groundwater and surface water needs to be better characterized. Field monitoring, isotope tracing, nontarget screening, and modeling are useful approaches and should be integrated to get a comprehensive understanding of PFASs sources and behaviors in groundwater.

Field-Based Distribution and Bioaccumulation Factors for Cyclic and Aliphatic Per- and Polyfluoroalkyl Substances (PFASs) in an Urban Sedentary Waterbird Population

The field-based distribution and bioaccumulation factor (BAF) for per- and polyfluoroalkyl substances (PFASs) were determined in residential Black Swans (Cygnus atratus) from an urban lake (Melbourne, Australia). The concentrations of 46 aliphatic and cyclic PFASs were determined by HPLC-MS/MS in serum and excrement from swans, and water, sediment, aquatic macrophytes, soil, and grass samples in and around the lake. Elevated concentrations of ∑₄₆PFASs were detected in serum (120 ng mL^-1) and excrement (110 ng g^-1 dw) were strongly related indicating a potential noninvasive sampling methodology. Environmental concentrations of PFASs were consistent with a highly impacted ecosystem and notably high concentrations of perfluoro-4-ethylcyclohexanesulfonate (PFECHS, 67584-42-3; C₈HF₁₅SO₃) were detected in water (27 ng L^-1) and swan serum (16 ng mL^-1). In the absence of credible putative alternative sources of PFECHS input to the lake, we propose that the use of high-performance motorsport vehicles is a likely source of contamination to this ecosystem. The BAF of perfluorocarboxylic acids increased with each additional CF₂ moiety from PFOA (15.7 L kg^-1 ww) to PFDoDA (3615 L kg^-1 ww). The BAF of PFECHS was estimated as 593 L kg^-1 ww, which is lower compared with that of PFOS (1097 L kg^-1 ww).

Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foam (AFFF) comprise some perfluoroalkyl substances but a larger variety of polyfluoroalkyl substances. Despite their abundance in AFFF, information is lacking on the potential transformation of these polyfluoroalkyl substances. Due to the biological and chemical stability of the repeating perfluoroalkyl -(CF₂)_n- moiety common to all known AFFF-derived PFASs, it is not immediately evident whether the microbial biotransformation mechanisms observed for other organic contaminants also govern the microbial biotransformation of polyfluoroalkyl substances. Herein, we aim to: 1) review the literature on the aerobic or anaerobic microbial biotransformation of AFFF-derived polyfluoroalkyl substances in environmental media; 2) compile and summarize proposed microbial biotransformation pathways for major classes of polyfluoroalkyl substances; 3) identify the dominant biotransformation intermediates and terminal biotransformation products; and 4) discuss these findings in the context of environmental monitoring and source allocation. This analysis revealed that much more is currently known about aerobic microbial biotransformation of polyfluoroalkyl substances, as compared to anaerobic biotransformation. Further, there are some similarities in microbial biotransformations of fluorotelomer and electrochemical fluorination-derived polyfluoroalkyl substances, but differences may be largely due to head group composition. Dealkylation, oxidation, and hydrolytic reactions appear to be particularly important for microbial biotransformation of AFFF-derived polyfluoroalkyl substances, and these biotransformations may lead to formation of some semi-stable intermediates. Finally, this review discusses key knowledge gaps and opportunities for further research.

Forward-Looking Roadmaps for Long-Term Continuous Water Quality Monitoring: Bottlenecks, Innovations, and Prospects in a Critical Review

Long-term continuous monitoring (LTCM) of water quality can bring far-reaching influences on water ecosystems by providing spatiotemporal data sets of diverse parameters and enabling operation of water and wastewater treatment processes in an energy-saving and cost-effective manner. However, current water monitoring technologies are deficient for long-term accuracy in data collection and processing capability. Inadequate LTCM data impedes water quality assessment and hinders the stakeholders and decision makers from foreseeing emerging problems and executing efficient control methodologies. To tackle this challenge, this review provides a forward-looking roadmap highlighting vital innovations toward LTCM, and elaborates on the impacts of LTCM through a three-hierarchy perspective: data, parameters, and systems. First, we demonstrate the critical needs and challenges of LTCM in natural resource water, drinking water, and wastewater systems, and differentiate LTCM from existing short-term and discrete monitoring techniques. We then elucidate three steps to achieve LTCM in water systems, consisting of data acquisition (water sensors), data processing (machine learning algorithms), and data application (with modeling and process control as two examples). Finally, we explore future opportunities of LTCM in four key domains, water, energy, sensing, and data, and underscore strategies to transfer scientific discoveries to general end-users.

Global occurrence and probabilistic environmental health hazard assessment of per- and polyfluoroalkyl substances (PFASs) in groundwater and surface waters

Per- and polyfluoroalkyl substances (PFASs) have been used in consumer and military products since the 1950s but are increasingly scrutinized worldwide because of inherent chemical properties, environmental contamination, and risks to public health and the environment. The United States Environmental Protection Agency (USEPA) identified 24 PFASs of interest for further study and possible regulation. We examined 371 peer-reviewed studies published since 2001 to understand the occurrence and distribution of 24 priority PFASs in global surface waters and groundwater. We identified 77,541 and 16,246 data points for surface waters and groundwater, respectively, with total PFAS concentrations ranging from low pg/L to low mg/L levels. Most data were from Asia, Europe, and North America with some reports from Oceania. PFAS information from other geographic regions is lacking. PFASs levels are consistently higher in rivers and streams followed by lakes and reservoirs and then coastal and marine systems. When sufficient data were available, probabilistic environmental hazard assessments (PEHAs) were performed from environmental exposure distributions (EEDs) to identify potential exceedances of available guideline values for each compound by matrix, region, and aquatic system. Specifically, exceedances of USEPA drinking water lifetime health advisory levels were up to 74% for PFOS in groundwater from Oceania and 69% for PFOA in North American groundwater. Our findings support selection of environmentally relevant experimental treatment levels for future toxicology, ecotoxicology and bioaccumulation studies, and potable source water exposure investigations, while highlighting PFASs and major geographic locations requiring additional study and inclusion in global monitoring and surveillance campaigns.

Background release and potential point sources of per- and polyfluoroalkyl substances to municipal wastewater treatment plants across Australia

Wastewater treatment plants (WWTPs) are known to be significant sources of per- and polyfluoroalkyl substances (PFAS) to the environment. In this study, PFAS were measured in the influent of 76 municipal wastewater treatment plants (WWTPs) serving approximately 53% of the Australian population. Of fourteen target PFAS, twelve analytes including six C5-C10 perfluoroalkyl carboxylic acids (PFCAs), four C4-10 perfluoroalkyl sulfonic acids (PFSAs) and two fluorotelomer sulfonates (6:2 and 8:2 FTS) were detected. Of these, PFOS, PFHxS and PFHxA had the highest median concentrations. The per capita background release of Σ₁₂ PFAS to WWTP influent in Australia was estimated to be 8.1-24 μg/d/per person. The background release was supplemented by contributions from catchment specific point sources (i.e., industry, airports, military bases, and landfills), whereby the number of industrial sites positively correlated with the per capita mass load of Σ₁₂ PFAS (r = 0.5-0.63, p < 0.01). The per capita mass loads were extrapolated to the entire Australian population, with estimates suggesting that approximately 1 kg/d of Σ₁₂ PFAS reach WWTPs in Australia (300-400 kg annually), with more than half of the PFAS (∼59%) attributed to background release and the remaining (∼41%) to catchment specific point sources. These data provide insight into the release of major PFAS to wastewater at a national scale in Australia.

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

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

Coupled photocatalytic alkaline media as a destructive technology for per- and polyfluoroalkyl substances in aqueous film-forming foam impacted stormwater

The release of aqueous film forming foam (AFFF) from fuel fire events, fire training events, and other activities has resulted in the presence of persistent and recalcitrant per- and polyfluoroalkyl substances (PFAS) in soil and water nationwide. This study describes the degradation and defluorination of PFAS in stormwater collected from an AFFF-impacted site. Silica-based granular media (SGM) containing titanium dioxide was packed into a column reactor and placed between ultraviolet (UV) lamps to excite the photocatalyst within the SGM and generate free radicals to degrade PFAS present in water that was passed through the media. The system was amended with nucleophiles (hydroxyls) to facilitate the destruction of PFAS. Results showed rapid degradation of 17 identified PFAS, including perfluoroalkyl acid (PFAA) precursors, perfluorosulfonic acids (PFSAs), and perfluorocarboxylic acids (PFCAs). Significant defluorination was observed, indicating PFAS destruction as a result of the coupled photocatalytic and nucleophilic attack. Column reactor experiment findings indicate SGM in the presence of UV light passively degraded a mixture of PFAS in a concentrated waste stream at ambient conditions.

Distribution, source identification and health risk assessment of PFASs in groundwater from Jiangxi Province, China

There is an urgent need to investigate on the distribution and fate of short-chain analogues and emerging per- and polyfluoroalkyl substances (PFASs) in groundwater, and little research on their source apportionment and health risks through the drinking water exposure pathway has been carried out. In present study, the concentration and source of 22 PFASs, including five alternatives: 6:2 fluorotelomer sulfonate (6:2 FTS), potassium 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B), hexafluoropropylene oxide trimer acid (HFPO-TA), hexafluoropropylene oxide dimer acid (HFPO-DA) and ammonium 4, 8-dioxa-3H-perfluorononanoate (ADONA), were analyzed in 88 groundwater samples from wells in Jiangxi Province, southeastern China. The total PFASs concentration (Σ₁₈PFASs) in groundwater varied from 1.27 to 381.00 ng/L (mean 47.60 ng/L). Short-chain perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were the most abundant perfluorinated carboxylic acids (PFCAs), and short-chain perfluorobutanesulfonate (PFBS) was the most abundant perfluorinated sulfonic acids (PFSAs) in groundwater samples. The quantitative source apportionment by nonnegative matrix/tensor factorization coupled with k-means clustering (NMFk) model suggested that short-chain homologues and emerging alternatives have been used as substitutes for legacy PFOS and PFOA. Furthermore, the human risk assessment results showed that the estimated daily intakes (EDIs) for short-chain PFCAs were higher than that of PFOA, whereas the EDIs of PFBS, 6:2 FTS and F-53B were comparable to that of PFOS.

Per- and polyfluoroalkyl substances in water and wastewater: A critical review of their global occurrence and distribution

Per- and polyfluoroalkyl substances (PFAS) are a family of fluorinated organic compounds of anthropogenic origin. Due to their unique chemical properties, widespread production, environmental distribution, long-term persistence, bioaccumulative potential, and associated risks for human health, PFAS have been classified as persistent organic pollutants of significant concern. Scientific evidence from the last several decades suggests that their widespread occurrence in the environment correlates with adverse effects on human health and ecology. The presence of PFAS in the aquatic environment demonstrates a close link between the anthroposphere and the hydrological cycle, and concentrations of PFAS in surface and groundwater range in value along the ng L^-1-μg L^-1 scale. Here, we critically reviewed the research published in the last decade on the global occurrence and distribution of PFAS in the aquatic environment. Ours is the first paper to critically evaluate the occurrence of PFAS at the continental scale and the evolving global regulatory responses to manage and mitigate the adverse human health risks posed by PFAS. The review reports that PFAS are widespread despite being phased out-they have been detected in different continents irrespective of the level of industrial development. Their occurrence far from the potential sources suggests that long-range atmospheric transport is an important pathway of PFAS distribution. Recently, several studies have investigated the health impacts of PFAS exposure-they have been detected in biota, drinking water, food, air, and human serum. In response to the emerging information about PFAS toxicity, several countries have provided administrative guidelines for PFAS in water, including Canada, the United Kingdom, Sweden, Norway, Germany, and Australia. In the US, additional regulatory measures are under consideration. Further, many PFAS have now been listed as persistent organic pollutants. This comprehensive review provides crucial baseline information on the global occurrence, distribution, and regulatory framework of PFAS.

Reduced bioaccumulation of fluorotelomer sulfonates and perfluoroalkyl acids in earthworms (Eisenia fetida) from soils amended with modified clays

Soils contaminated by per- and polyfluoroalkyl substances (PFAS) pose long-term sources to adjacent water bodies and soil invertebrates. The study investigated the stabilization using a modified clay adsorbent (FLUORO-SORB100®) in reducing the bioaccumulation of 13 anionic PFAS by earthworms (Eisenia fetida), as compared to coal-based granular activated carbon. The target PFAS included four perfluoroalkyl sulfonates such as perfluorooctane sulfonate (PFOS), six perfluoroalkyl carboxylates (e.g., perfluorooctanoate PFOA), and three (X:2) fluorotelomer sulfonates. Laboratory-spiked surface soil and the soil collected from a site contaminated by aqueous film-forming foams were examined. Both adsorbents resulted in reduced earthworm PFAS body burdens at the end of the 28-day uptake phase. The highest adsorbent amendment concentration (4 w/w%) was most effective, achieving >95% reduction of PFAS body burden. Soil leaching tests indicated better immobilization performance by the clay adsorbent for most analytes; in comparison, the activated carbon performed better at reducing total PFAS body burdens, possibly owing to the avoidance of larger-sized particles by earthworms. Strong positive logarithm relationships were observed between leachate concentrations and earthworm body burdens for most PFAS in the spiked soil. The study demonstrated that stabilization of PFAS using modified clay adsorbents can achieve concurrent benefits of lowering leachability and reducing bioaccumulation.

PFAS Molecules: A Major Concern for the Human Health and the Environment

Per- and polyfluoroalkyl substances (PFAS) are a group of over 4700 heterogeneous compounds with amphipathic properties and exceptional stability to chemical and thermal degradation. The unique properties of PFAS compounds has been exploited for almost 60 years and has largely contributed to their wide applicability over a vast range of industrial, professional and non-professional uses. However, increasing evidence indicate that these compounds represent also a serious concern for both wildlife and human health as a result of their ubiquitous distribution, their extreme persistence and their bioaccumulative potential. In light of the adverse effects that have been already documented in biota and human populations or that might occur in absence of prompt interventions, the competent authorities in matter of health and environment protection, the industries as well as scientists are cooperating to identify the most appropriate regulatory measures, substitution plans and remediation technologies to mitigate PFAS impacts. In this review, starting from PFAS chemistry, uses and environmental fate, we summarize the current knowledge on PFAS occurrence in different environmental media and their effects on living organisms, with a particular emphasis on humans. Also, we describe present and provisional legislative measures in the European Union framework strategy to regulate PFAS manufacture, import and use as well as some of the most promising treatment technologies designed to remediate PFAS contamination in different environmental compartments.

Field-Scale Demonstration of PFAS Leachability Following In Situ Soil Stabilization

A field-scale validation is summarized comparing the efficacy of commercially available stabilization amendments with the objective of mitigating per- and polyfluoroalkyl substance (PFAS) leaching from aqueous film-forming foam (AFFF)-impacted source zones. The scope of this work included bench-scale testing to evaluate multiple amendments and application concentrations to mitigate PFAS leachability and the execution of field-scale soil mixing in an AFFF-impacted fire-training area with nearly 2.5 years of post-soil mixing monitoring to validate reductions in PFAS leachability. At the bench scale, several amendments were evaluated and the selection of two amendments for field-scale evaluation was informed: FLUORO-SORB Adsorbent (FS) and RemBind (RB). Five ∼28 m³ test pits (approximately 3 m wide by 3 m long by 3 m deep) were mixed at a site using conventional construction equipment. One control test pit (Test Pit 1) included Portland cement (PC) only (5% dry weight basis). The other four test pits (Test Pits 2 through 5) compared 5 and 10% ratios (dry weight basis) of FS and RB (also with PC). Five separate monitoring events included two to three sample cores collected from each test pit for United States Environmental Protection Agency (USEPA) Method 1315 leaching assessment. After 1 year, a mass balance for each test pit was attempted comparing the total PFAS soil mass before, during, and after leach testing. Bench-scale and field-scale data were in good agreement and demonstrated >99% decrease in total PFAS leachability (mass basis; >98% mole basis) as confirmed by the total oxidizable precursor assay, strongly supporting the chemical stabilization of PFAS.

Biochar sorption of perfluoroalkyl substances (PFASs) in aqueous film-forming foams-impacted groundwater: Effects of PFASs properties and groundwater chemistry

The widespread use of per- and polyfluoroalkyl substances (PFASs)-related products such as aqueous film-forming foams (AFFF) has led to increasing contamination of groundwater systems. The concentration of PFASs in AFFF-impacted groundwater can be several orders of magnitude higher than the drinking water standard. There is a need for a sustainable and effective sorbent to remove PFASs from groundwater. This work aims to investigate the sorption of PFASs in groundwater by biochar column. The specific objectives are to understand the influences of PFASs properties and groundwater chemistry to PFASs sorption by biochar. The PFASs-spiked Milli-Q water (including 19 PFASs) and four aqueous film-forming foams (AFFF)-impacted groundwater were used. The partitioning coefficients (log K_d) of long chain PFASs ranged from 0.77 to 4.63 while for short chain PFASs they remained below 0.68. For long chain PFASs (C ≥ 7), log K_d increased by 0.5 and 0.8 for each CF₂ moiety of PFCAs and PFSAs, respectively. Dissolved organic matter (DOM) was the most influential factor in PFASs sorption over pH, salinity, and specific ultraviolet absorbance (SUVA). DOM contained hydrophobic compounds and metal ions which can form DOM-PFASs complexes to provide more sorption sites for PFASs. The finding is useful for executing PFASs remediation by biochar filtration column, especially legacy long chain PFASs, for groundwater remediation.

Environmental occurrence and remediation of emerging organohalides: A review

As replacements for "old" organohalides, such as polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), "new" organohalides have been developed, including decabromodiphenyl ethane (DBDPE), short-chain chlorinated paraffins (SCCPs), and perfluorobutyrate (PFBA). In the past decade, these emerging organohalides (EOHs) have been extensively produced as industrial and consumer products, resulting in their widespread environmental distribution. This review comprehensively summarizes the environmental occurrence and remediation methods for typical EOHs. Based on the data collected from 2015 to 2021, these EOHs are widespread in both abiotic (e.g., dust, air, soil, sediment, and water) and biotic (e.g., bird, fish, and human serum) matrices. A significant positive correlation was found between the estimated annual production amounts of EOHs and their environmental contamination levels, suggesting the prohibition of both production and usage of EOHs as a critical pollution-source control strategy. The strengths and weaknesses, as well as the future prospects of up-to-date remediation techniques, such as photodegradation, chemical oxidation, and biodegradation, are critically discussed. Of these remediation techniques, microbial reductive dehalogenation represents a promising in situ remediation method for removal of EOHs, such as perfluoroalkyl and polyfluoroalkyl substances (PFASs) and halogenated flame retardants (HFRs).

New insight into PFOS transformation pathways and the associated competitive inhibition with other perfluoroalkyl acids via photoelectrochemical processes using GOTiO2 film photoelectrodes

The global distribution and environmental persistence of perfluoroalkyl acids (PFAAs) has been considered a critical environmental concern. In this work, we successfully fabricated a graphene oxide-titanium dioxide (GOTiO₂) photoelectrode for perfluorooctane sulfonate (PFOS) degradation in a photoelectrochemical (PEC) system. The results reveal that a 5 wt.% GOTiO₂ anode possesses the optimal PEC performance, with a band gap (E_g) of 2.42 eV, specific surface area (S_BET) of 72.6 m² g^-1 and specific capacitance (Cs) of 4.63 mF cm^-2. In the PEC system, PFOS can be efficiently removed within 4 h of reaction time, with a pseudo-first-order rate constant of 0.0124 min^-1, under the optimized conditions of current density = 20 mA cm^-2, electrode distance = 5 mm, solution pH = 5.64, [PFOS]₀= 0.5 µM and NaClO₄ electrolyte concentration = 50 mM. The electron transfer pathway, hydroxyl radicals and superoxide radicals are all responsible for PFOS decomposition/transformation. New degradation pathways were identified; a total of 25 PFOS byproducts are reported in this work; and perfluoroalkane sulfonates (PFSAs), perfluorinated aldehydes (PFALs) and hydrofluorocarbons (HFCs) were identified for the first time. PFOS degradation involves the desulfonation pathway as the first step, followed by oxidation and subsequent defluorination, decarboxylation, decarbonylation, sulfonation, defluorination and hydroxylation. The results from this work also show that the reactivity of PFAAs is related to their carbon chain length, with shorter-chain PFAAs exhibiting a lower degradation rate. In a PFAA mixture, a decline in the degradation rate was observed for the shorter-chain-length PFAAs, suggesting stronger competitive inhibition and indicating stronger environmental recalcitrance during the treatment process. Novelty statement: Although many efforts have been made to identify perfluorooctane sulfonate (PFOS) degradation byproducts, previous studies were only able to identify byproducts that are related to perfluorinated carboxylic acids (PFCAs). This is the first study to elucidate the new PFOS degradation pathway; furthermore, this is the first report to identify byproducts containing sulfonate groups (perfluoroalkane sulfonates, PFSAs), aldehyde groups (perfluorinated aldehydes, PFALs), and hydrofluorocarbons (HFCs). This study further systematically explores how perfluoroalkyl acid (PFAA) degradation may be affected in the mixture system: shorter-chain-length PFAAs suffer stronger competitive inhibition in the photoelectrochemical (PEC) system. By utilizing the graphene oxide-titanium dioxide (GOTiO₂) photoelectrode fabricated in this work, PFOS can be successfully decomposed during the PEC process for the first time.

Occurrence of per- and polyfluoroalkyl substances (PFASs) in wastewater of major cities across China in 2014 and 2016

China produced and consumed a large amount of per- and polyfluoroalkyl substances (PFASs). whose persistency and possible toxicity to organisms have raised public health concerns. Analyzing influent wastewater could help to assess the composition and mass load of PFASs discharged into a wastewater treatment plant (WWTP) from its catchment. In this study, we analyzed 27 PFASs in wastewater samples collected from 42 WWTPs across China in 2014 and 2016. Results indicated that perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were the most common PFASs in wastewater. Population normalized mass loads of PFOA and PFOS were higher in Eastern China than in the other three regions, possibly due to their higher usage. Although the concentrations of PFASs in Central and West areas were showed lower than in East area, Wuhan (in Central area) and Lanzhou (in West area) were hotspots of PFASs pollution because of their industry structure. Population density and per capita Gross Domestic Product (GDP) have positive correlations with the concentration of PFBA, PFOA, PFHxA, and ∑PFASs in wastewater. The estimated annual release of PFASs to WWTPs in our study is much lower than the total emission to the environment. Our results suggest that although there was some reduction in the production volume, certain legacy PFASs were still released into wastewater and their composition and concentration vary among WWTPs.

Enhanced Recovery of Per- and Polyfluoroalkyl Substances (PFASs) from Impacted Soils Using Heat Activated Persulfate

Varying transport potential of cationic, zwitterionic, and anionic per- and polyfluoroalkyl substances (PFASs) may pose challenges for remediation of aqueous film forming foam (AFFF) impacted sites, particularly during groundwater extraction. Slow desorption of stronger sorbing, zwitterionic, and cationic PFASs may cause extended remediation times and rebound in aqueous PFAS concentrations. Persulfate oxidation has the potential to convert a complex mixture of PFASs into a simpler and more recoverable mixture of perfluoroalkyl acids (PFAAs). AFFF-impacted soils were treated with heat-activated persulfate in batch reactors and subjected to 7-day leaching experiments. Soil and water were analyzed using a combination of targeted and high resolution liquid chromatography mass spectrometry techniques as well as the total oxidizable precursors assay. Following oxidation, total PFAS composition showed the expected shift to a higher fraction of PFAAs, and this led to higher total PFAS leaching in pretreated reactors (108-110%) vs control reactors (62-90%). In both pretreated and control soils, precursors that remained following leaching experiments were 61-100% cationic and zwitterionic. Results suggest that persulfate pretreatment of soils has promise as an enhanced recovery technique for remediation of total PFASs in impacted soils. They also demonstrate that PFAS distribution may have been altered at sites where in situ chemical oxidation was applied to treat co-occurring contaminants of concern.

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Dagang Oilfield: Multimedia distribution and contributions of unknown precursors

A systematic survey was conducted on twenty-six per- and polyfluoroalkyl substances (PFASs) in fifty-one paired samples of surface water, sediment, and soil from Dagang Oilfield, Tianjin, China. Perfluorooctanoic acid, perfluorooctane sulfonic acid, p-perfluorous nonenoxybenzenesulfonate (OBS), and 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) were ubiquitous in the oilfield with field log K_d of 1.3-2.2, indicating a high partition potential from surface water to sediment. Total petroleum hydrocarbons (TPH) are a predictor for PFAS contamination at oilfield. The concentrations of OBS and 6:2 FTAB were higher in surface water and sediment with elevated TPH level. With total oxidizable precursor assay, unknown precursors for C2-C3 perfluoroalkyl carboxylic acids (PFCAs) (57-99 mol%) contributed more than those for C4-C12 PFCAs in the three mediums. The unknown C4-, C6-, and C8-based precursors tended to be precursors for perfluoroalkyl sulfonates at the oilfield, and C8 fluorotelomer-based precursors particularly occurred in the surface water. The concentrations of C4- and C8-based precursors were found positively correlated with TPH levels (r = 0.67-0.72, p < 0.05), while C6 precursors may also come from other sources. Further studies are necessary to clarify the mass balance and risk assessment for unknown PFASs.

Sorbent assisted immobilisation of perfluoroalkyl acids in soils - effect on leaching and bioavailability

Contamination of soils and groundwater with perfluoroalkyl acids (PFAAs) is widespread due to their use in aqueous film-forming foams (AFFF). In this study the effectiveness of RemBind®, a sorbent containing activated carbon and aluminium oxyhydroxides was tested, as a tool to reduce the leaching and bioavailability of 12 PFAAs in soils, by amending contaminated soils with 5-30% (by weight) of the sorbents. Batch tests were used to determine the leaching of PFAAs. Their bioavailability to earthworms and wheat grass was assessed in greenhouse microcosms. Leaching and bioavailability of PFOS was reduced by up to 99.9%, at most sorbent application rates. Lowest reduction of leaching was found for shorter perfluoroalkyl chain length chemicals. The specific formulation of RemBind®, which is available in a basic and superior formulation, as well as the application rate were parameters for increasing effectiveness of the treatment. Furthermore, differences in leaching as well as bioavailability were seen depending on the perfluoroalkyl chain length. A preliminary assessment of the long-term stability of the treatment, assessed after a three-year curing period, suggested that the sorbent continued to be effective in reducing PFAAs in leachates, thus showing the potential of this sorbent to hinder further environmental contamination.