Total Perfluoroalkyl Acids Research Articles

Legacy and alternative perfluoroalkyl acids in the Yellow River on the Qinghai-Tibet Plateau: Levels, spatiotemporal characteristics, and multimedia transport processes

The source region of the Yellow River (SRYR) located in the northeast of the Qinghai-Tibetan Plateau is not only the largest runoff-producing area in the Yellow River Basin, but also the most important freshwater-supply ecological function area in China. In this study, the short-term spatiotemporal distribution of selected legacy and alternative perfluoroalkyl acids (PFAAs) in the SRYR was first investigated in multiple environmental media. Total PFAA concentrations were in the range of 1.16-14.3 ng/L, 4.25-42.1 pg/L, and 0.21-13.0 pg/g dw in rainwater, surface water, and sediment, respectively. C4-C7 PFAAs were predominant in various environmental matrices. Spatiotemporal characteristics were observed in the concentrations and composition profiles. Particularly, the spatial distribution of rainwater and the temporal distribution of surface water exhibited highly significant differences (p<0.01). Indian monsoon, westerly air masses, and local mountain-valley breeze were the driving factors that contributed to the change of rainwater. Rainwater, meltwater runoff, and precursor degradation were important sources of PFAA pollution in surface water. Organic carbon content was a major factor influencing PFAA distribution in sediment. These results provide a theoretical basis for revealing the regional transport and fate of PFAAs, and are also important prerequisites for effectively protecting the freshwater resource and aquatic environment of the Qinghai-Tibetan Plateau.

Influence of age on the concentrations of perfluoroalkyl acids (PFAA) in the tissues of perch (Percafluviatilis)

Globally, perfluoroalkyl acids (PFAA) are ubiquitous due to their almost unlimited applications in industry and households and are detected in a wide variety of matrices.Aquatic ecosystems are of particular importance due to the spread of PFAA via water fluxes. The majority of published studies describe PFAA concentrations in fish or aquatic mammals, but not the dependence of PFAA concentrations in tissues and organs in fish of different ages. Since this is very important for understanding the accumulation behavior of these substances our study systematically investigates the influence of age on the PFAA concentration in the tissues of 74 perches (Perca fluviatilis), a very popular edible fish. Fish are particularly suitable as indicators of PFAA contamination of water because of their uptake via water (gills and skin) and food (predominantly piscivorous diet). The mean total PFAA concentrations (as the sum of the individual concentrations of 11 compounds) were: 114 μg/kg (kidney), 112 μg/kg (heart), 79.9 μg/kg (liver), 78.4 μg/kg (spleen), 64.6 μg/kg (gills) and 21.7 μg/kg (muscle), with longer-chain compounds accounting for 90% of the substances. Perfluorooctanesulfoic acid (PFOS) accounted for the largest percentage of the total PFAA concentration in all tissues at 43–63%. With the exception of the heart and spleen, a significant increase in total concentrations was observed with increasing age of the perch. The strongest correlation was observed for the kidney, followed by the liver and gills. With regard to their consumption as human nutrition the tolerable weekly PFAA intake of 4.4 ng/kg bodyweight and week for the sum of the 4 EFSA PFAA in adults and children was exceeded many times over (860% and 1600% respectively) with an average fish consumption per week. The maximum PFAA levels set in the E.U. since January 2023 were exceeded five times.

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

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

Field study on endogenous perfluoroalkyl acid release and their spatiotemporal distribution processes induced by inland navigation

Dense populations and industries in regions with developed inland waterways have caused the significant discharge of perfluoroalkyl acids (PFAAs) into surrounding waterways. Despite being the dominant energy input in the waterways, the impact of ship navigation on endogenous PFAA release is unclear. In this study, a field experiment was carried out in the Wangyu River (Taihu Basin, China) to investigate the spatiotemporal distribution processes of PFAAs in the water column after passage of ships with different tonnages, speeds, and draughts. The results showed that the PFAA contents did not decrease continuously with time but increased with a lag after the passing ship triggered a transient massive dissolution of PFAAs into the overlying water. In addition, PFAA contents in suspended particulate matter (SPM) exhibited a fluctuating downward trends after their peak at the moment of ship passage. Vertically, the PFAA concentrations among the layers of overlying water were relatively homogeneous, whereas SPM exhibited substantial heterogeneity in its distribution and adsorption of PFAAs. Moreover, the differences in jet scouring velocity (u), disturbance duration (t), and draught (h) of ships resulted in large variability in PFAA contents in the water column. Variance partitioning analysis further quantified the effects of u, t, and h on total PFAAs in the water column, with individual contributions of 53 %, 12 %, and 6 %, respectively. Furthermore, the release of endogenous PFAAs induced by ship passage involved rapid and slow processes, the former determining the overall PFAA release and the latter affecting PFAA concentration recovery in the water column. The findings provide in-situ observational data on spatiotemporal variations of PFAAs in multiphase media following ship passage, enhancing our understanding of endogenous pollution in inland waterways.

Factors affecting the occurrence and accumulation of perfluoroalkyl acids in indoor dust in Tainan, Taiwan

Perfluoroalkyl acids (PFAAs) are environmentally and biologically persistent chemicals. In this study, we investigated the concentrations of six PFAAs in dust samples collected from different indoor environments in a college campus in Tainan, Taiwan, and assessed the health risk of PFAAs exposure to college students. We also analyzed the effects of dust characteristics (total organic carbon, moisture content, and dust content) on PFAAs levels. With regard to the space type, the median of total PFAAs concentrations were in the order of laboratories (528.9 μg kg−1) > offices (304.2 μg kg−1) > dormitories (180.1 μg kg−1) > classrooms (105.1 μg kg−1). With regard to the height from the ground, the median total PFAAs concentrations were in the order of dust near the floors (>2 m; 383.6 μg kg−1) > near the ceiling (0–2 m; 202.5 μg kg−1) > on the ground (0 m; 145.6 μg kg−1). The main species of PFAAs, perfluorooctane sulfonate and short-chain perfluoroalkyl carboxylates, accounted for respectively 30%–60% and ∼20%–37% of total PFAAs pollution in the indoor space types and sampling heights under consideration. The average daily intake (ADI) values of six PFAAs for college students were found to be 0.059–0.126 ng kg−1 BW day−1 (BW: body weight), with dormitories and workplaces (i.e., laboratories and offices) accounting for over 40% and ∼50% of the ADI, respectively. The estimated hazard quotient ranged from 0.0029 to 0.0063, three orders of magnitude lower than 1, suggesting relatively low risks for college students exposed to the six PFAAs monitored in indoor dust. The analysis of dust characteristics revealed that total organic carbon did not have a significant effect on PFAAs levels as we expected. In contrast, dust moisture and cation content dominated PFAAs accumulation.

Per- and polyfluoroalkyl substances in water treatment residuals: Occurrence and desorption.

Per- and polyfluoroalkyl substances (PFAS) in surface and ground waters supplying municipal drinking water are a growing concern. However, PFAS concentrations in water treatment residuals (WTRs)-a solid by-product of water treatment-have yet to be explored. In a first of its kind assessment, we examine PFAS occurrence in seven calcium (Ca)-, iron-, and aluminum-based drinking water treatment residuals (DWTRs) and one wastewater effluent treatment residual (WWETR) produced using aluminum chlorohydrate (ACH). Only perfluoroalkyl acids (PFAAs) were detected, with total PFAA concentrations in the seven DWTRs produced from naturally recharged water sources ranging from 0 to ∼3.3μg kg-1 ; no PFAS were detected in either of the Ca-DWTRs. The ACH-WWETR contained the highest number and concentration of PFAAs (34μg kg-1 ). Desorption of resident PFAAs from the WTRs was negligible for the carboxylates (PFCAs). Some desorption of the sulfonates (PFSAs) was detected, particularly for PFOS which had the highest concentration among all resident PFAAs. The ACH-WWETR was further evaluated for its potential to attenuate additional PFAAs (3500μg mL-1 total PFAAs) in a biosolid-derived porewater matrix. Sorption was highest for long-chain PFAAs and subsequent desorption of the adsorbed PFAAs ranged from 0% to no more than 26%, with the WWETR mass added strongly affecting both PFSA and PFCA sorption/desorption. These findings suggest that WTRs, if introduced into the environment, are unlikely to be a major source of PFAS. Also, the use of particular WTRs as amendments may provide a beneficial reduction in PFAS mobility.

Concentration, distribution, and bioconcentration of short- and long-chain perfluoroalkyl substances in the water, suspended particulate matter, and surface sediment of a typical semi-enclosed bay

This study investigated per- and polyfluoroalkyl substances (PFAS) levels in the surface water, suspended particulate matter (SPM), sediment, and fishes in the Laizhou Bay (LZB) and its inflow river estuaries in dry, normal, and wet seasons. The results demonstrated that the short-chain perfluoroalkyl acids (PFAA) accounted for about 60 % of the total PFAA (∑PFAA) concentration in water, while long-chain PFAA were the dominant compounds in the sediment and SPM. The levels of the ∑PFAA and their precursors decreased from the estuaries to the bay, which implied that terrigenous input (pollutant in land flowed into sea) was the main pollution source of PFAA in the LZB. The PFAAs levels in surface water were ranked as the order of dry > normal > wet season. The distribution coefficients of PFAA showed that the long-chain PFAA were more prone to be adsorbed by sediment and SPM than short-chain PFAA. The increase of ∑PFAA concentrations was in the range of 0.32–36.7 ng·L−1 after the oxidation conversion of water samples. Precursors were the important source of the PFAA in the surface water. The perfluorooctane sulfonate (PFOS) was the dominant compound in fish tissues. These results provide hints for understanding PFAS pollution in LZB.

Mechanisms of propeller jet-induced migration, release, and distribution of perfluoroalkyl acids in sediment–water systems

Perfluoroalkyl acids (PFAAs) are continuously accumulated in surface sediments due to extensive and long-term application. However, the mechanisms through which disturbances induced by ship propeller jets at the riverbed cause secondary release of PFAAs from sediments remain unclear. In this study, the effects of different propeller rotational speeds on PFAA migration, release, and distribution in multiphase media were investigated by performing indoor flume experiments combined with particle tracking velocimetry. Moreover, key factors influencing PFAA migration and distribution were identified, and partial least squares regression (PLS) method was applied to develop quantitative prediction models of relationships among hydrodynamics, physicochemical parameters, and PFAA distribution coefficients. The total PFAA concentrations (ΣPFAAs) in overlying water under propeller jet action exhibited transient characteristics and hysteresis with time after the disturbance. In contrast, the ΣPFAAs in suspended particulate matter (SPM) exhibited an upward trend throughout the process with consistent characteristics. The spatial distribution trends of PFAAs in overlying water and SPM at different propeller rotational speeds featured vertical variability and axial consistency. Furthermore, PFAA release from sediments was driven by axial flow velocity (Vx) and Reynolds normal stress Ryy, while PFAA release from porewater was inextricably linked to Reynolds stresses Rxx, Rxy, and Rzz (p < 0.05). PLS regression models showed that variations in Vorticity, dissolved organic carbon, and pH influenced the decreases in PFAA distribution coefficients between SPM and overlying water (KD-SW) as propeller rotational speed increased, except for very long-chain PFAAs (C > 10). The increases in PFAA distribution coefficients between sediment and porewater (KD-SP) were mainly determined by physicochemical parameters of sediments, and the direct effect of hydrodynamics was relatively weak. Our study provides valuable information regarding the migration and distribution of PFAAs in multiphase media under propeller jet disturbance (both during and after disturbance).

Vermont-wide assessment of anthropogenic background concentrations of perfluoroalkyl substances in surface soils

Shallow surface soils from 66 suburban sampling locations across Vermont were analyzed for 17 different perfluoroalkyl acids (PFAA). PFAA were detected in all 66 surface soils, with a total concentration of PFAA ranging from 540 to 36,000 ng/kg dry soil weight (dw). Despite the complexity of site-specific factors, some general trends and correlations in PFAA concentrations were observed. For instance, perfluoro-1-octanesulfonate (PFOS) dominated in all soil samples while seven other PFAA, including perfluoro-n-nonanoic acid, perfluoro-n-octanoic acid, perfluoro-n-hexanoic acid, perfluoro-n-heptanoic acid, perfluoro-n-decanoic acid, perfluoro-n-undecanoic acid, perfluoro-1-butanesulfonate, and perfluoro-1-hexanesulfonate (PFNA, PFOA, PFHxA, PFHpA, PFDA, PFUnDA, and PFBS, respectively), were identified at more than 50 % of the locations. Perfluoroalkyl carboxylic acids (PFCA) showed a positive correlation with total organic carbon, whereas no clear correlation was observed for perfluoroalkyl sulfonate acids (PFSA). In addition, variations in geographical distributions of PFAA were observed, with relatively higher total PFAA in northern regions when compared to Southern Vermont. Moreover, PFHxA, PFNA, PFDA, PFUnDA, PFOS, and total PFAA were positively correlated to land-use types in Northern Vermont. These results are useful for understanding unique behaviors of PFCA vs. PFSA in geospatially distributed surface soils and for providing anthropogenic background data for setting PFAS cleanup standards for surface soils.

Perfluoroalkyl acids in sediment and water surrounding historical fire training areas at Barksdale Air Force Base.

Perfluoroalkyl acids (PFAAs) are environmentally persistent components of surfactants that consist of fully fluorinated carbon chains and a terminal sulfonate or carboxylate polar head moiety. Due to their unique amphiphilic properties, PFAAs are used in the manufacturing of products such as aqueous film forming foams (AFFF). There is cause for concern for PFAA contamination resulting from runoff and groundwater infiltration of AFFF that were used during fire training. This study analyzed water and sediment samples that were collected over a 13-month sampling period from bayous upstream and downstream of two former fire training areas located near Barksdale Air Force Base (BAFB); the occurrence and magnitude of PFAAs supported an aquatic ecological risk assessment of potential impacts of PFAAs at the site. Liquid chromatography coupled with mass spectrometry was used for determination of 6 PFAAs listed under the third Unregulated Contaminant Monitoring Rule (UCMR 3). Total PFAA concentrations in surface water and sediment samples ranged from 0 (ND) −7.1 ng/mL and 0 (ND) −31.4 ng/g, respectively. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the predominant PFAAs detected. In general, perfluorosulfonates were quantified more frequently and at higher concentrations than perfluorocarboxylates. The perfluoroalkyl chain length of PFAAs also showed significant influence on PFAA concentrations when analyzed by Spearman’s rank correlation analysis. Some contamination we observed in surface water and sediment samples from reference locations could be a result of local runoff from the use of commercial products containing per- and poly-fluoroalkyl substances (PFAS), but AFFF appears to be the primary source given the close proximity of the historical fire training areas.

Perfluoroalkyl acids (PFAAs) in the aquatic food web of a temperate urban lake in East China: Bioaccumulation, biomagnification, and probabilistic human health risk

The bioaccumulation and biomagnification of perfluoroalkyl acids (PFAAs) in temperate urban lacustrine ecosystems is poorly understood. We investigated the occurrence and trophic transfer of and probabilistic health risk from 15 PFAAs in the food web of Luoma Lake, a temperate urban lake in East China. The target PFAAs were widely distributed in the water (∑PFAA: 77.09 ± 9.07 ng/L), suspended particulate matter (SPM) (∑PFAA: 284.07 ± 118.05 ng/g dw), and sediment samples (∑PFAA: 67.77 ± 17.96 ng/g dw) and occurred in all biotic samples (∑PFAA: 443.27 ± 124.89 ng/g dw for aquatic plants; 294.99 ± 90.82 for aquatic animals). PFBA was predominant in water and SPM, with 40.11% and 21.35% of the total PFAAs, respectively, while PFOS was the most abundant in sediments (14.11% of the total PFAAs) and organisms (14.33% of the total PFAAs). Sediment exposure may be the major route of biological uptake of PFAAs. The PFAA accumulation capacity was the highest in submerged plants, followed by emergent plants > bivalves > crustaceans > fish > floating plants. Long-chain PFAAs were biomagnified, and short-chain PFAAs were biodiluted across the entire lacustrine food web. PFOS exhibited the greatest bioaccumulation and biomagnification potential among the target PFAAs. However, biomagnification of short-chain PFAAs was also observed within the low trophic-level part of the food web. Human health risk assessment indicated that perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) posed health risks to all age groups, while the other PFAAs were unlikely to cause immediate harm to consumers in the region. This study fills a gap in the knowledge of the transfer of PFAAs in the food webs of temperate urban lakes.

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

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

Distribution of perfluoroalkyl acids in fish species from the Baltic Sea and freshwaters in Finland

Occurrence and distribution of perfluoroalkyl acids (PFAAs), a sub-category of per- and polyfluoroalkyl substances (PFASs), is widespread in the environment. Food, especially fish meat, is a major pathway via which humans are exposed to PFAAs. As fish is an integral part of Nordic diet, therefore, in this study, several fish species, caught in selected Baltic Sea basins and freshwater bodies of Finland, were analysed for PFAAs. Perfluorooctane sulfonate (PFOS) was detected in all Baltic Sea fish samples and in >80% fish samples from freshwaters. PFOS contributed between 46 and 100% to the total PFAA concentration in Baltic Sea fish samples and between 19 and 28% in fish samples from freshwaters. Geographically, concentration ratios of PFOS to other PFAAs differed between fish from the Baltic Sea and Finnish lakes suggesting that distribution of PFAAs differ in these environments. Results were compared with current safety thresholds – environmental quality standard for biota (EQSbiota) set by the European Commission and a group tolerable weekly intake (TWI) for the sum of four PFASs (∑PFAS-4) i.e. perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS) and PFOS, recommended by the European Food Authority (EFSA). EQSbiota compliance was observed for PFOS in all species except smelt caught in the Baltic Sea and also in the River Aurajoki, where smelt had migrated from the Baltic Sea for spawning. Moderate consumption of most Baltic fishes (200 g week−1) results in an exceedance of the new TWI (4.4 ng kg−1 body weight week−1) for ∑PFAS-4.

Laboratory and Semi-Pilot Scale Study on the Electrochemical Treatment of Perfluoroalkyl Acids from Ion Exchange Still Bottoms

The ubiquitous presence of perfluoroalkyl acids (PFAAs) in the environment remains a serious environmental concern. In this study, the electrochemical oxidation (EO) of PFAAs from the waste of ion exchange (IX) still bottoms was assessed at the laboratory and semi-pilot scales, using full boron-doped diamond (BDD) electrochemical cells. Multiple current densities were evaluated at the laboratory scale and the optimum current density was used at the semi-pilot scale. The results at the laboratory scale showed &gt;99% removal of total PFAAs with 50 mA/cm2 after 8 h of treatment. PFAAs treatment at the semi-pilot scale showed 0.8-fold slower pseudo-first-order degradation kinetics for total PFAAs removal compared to at the laboratory scale, and allowed for &gt;94% PFAAs removal. Defluorination values, perchlorate (ClO4−) generation, coulombic efficiency (CE), and energy consumption were also assessed for both scales. Overall, the results of this study highlight the benefits of a tandem concentration/destruction (IX/EO) treatment approach and implications for the scalability of EO to treat high concentrations of PFAAs.

Occurrence and transport of perfluoroalkyl acids (PFAAs) in a Yangtze River water diversion project during water diversion and flooding

Water diversion is increasingly utilized for water supply, flood control, irrigation, and water quality improvement in many water bodies globally. Our findings indicate that micropollutants such as perfluoroalkyl acids (PFAAs) can be transported via dual-source water diversion projects during water diversion and flood discharge, which may negatively impact both receiving water bodies. However, the sources, spatiotemporal variations, and fluxes of PFAAs under water diversion projects remain unclear. Here we report patterns of 18 PFAA compounds in the surface water at 14 sites of a dual-source water diversion project (Wangyu River) connecting the Yangtze River and Taihu Lake in China. We found multiple contamination hotspots with PFHxA and PFOA dominantly originating from industrial and domestic sources during water diversion from the Yangtze River to Taihu Lake. During the severe flooding in summer 2020, PFAA concentrations ranged from 82.0 to 114.0 ng L−1, while the concentrations and relative contributions of individual perfluoroalkane sulfonic acids (PFSAs) increased along the mainstream due to the tributaries’ contribution and high contamination level in the lake. Based on the spatiotemporal patterns of PFAA pollution, the flux of total PFAAs including both dissolved-phase and SS-phase into Taihu Lake was estimated as 26.6 kg in January 2020 as a reference value for water diversion. To our knowledge, this is the first report to describe the sources, occurrences, and transport of PFAAs in a dual-source water diversion project during water diversion and flooding. The results provide a novel perspective regarding the ecological safety of dual-source water diversion projects.

Occurrence, distribution, and risk assessment of perfluoroalkyl acids in drinking water sources from the lower Yangtze River

The occurrence, spatial distribution, potential sources, and risk assessment of 14 perfluoroalkyl acids (PFAAs), including 11 perfluoroalkyl carboxylic acids and 3 perfluoroalkyl sulfonates acids, were investigated in 21 drinking water sources from the lower Yangtze River in November 2019. The total PFAAs (∑PFAAs) concentrations ranged from 39.3 to 220.3 ng/L, and perfluorooctanoic acid and perfluorooctanesulfonate were predominant with average concentrations of 19.4 and 15.4 ng/L, respectively. The higher ∑PFAAs concentrations in the southern shore and downstream could be attributed to industrial development and surface runoff/tide currents, respectively. Principal component analysis-multiple linear regression revealed that the primary sources of PFAAs were fluororesin coatings/metal plating, surface runoff/textile, effluent discharge/food packaging, and leather/fabrics. Human intake risks of PFAAs were assessed by target hazard quotient (THQ), which showed that human health risks of PFAAs decreased with increasing age, excluding 13–17 years age group. Moreover, the total exposure risks of PFOA/PFOS in all sampling sites to people aged over 18 years calculated based on contribution from drinking water were noted to be at safe level. The results obtained were helpful for improving our understanding of human health risks of PFAAs, and expanding our knowledge on PFAAs in drinking water.

A flow-through cell for the electrochemical oxidation of perfluoroalkyl substances in landfill leachates

A novel boron-doped diamond (BDD) flow-through cell was used to evaluate the electrochemical oxidation of perfluoroalkyl acids (PFAAs) in landfill leachates. Six different leachates with a concentration of individual PFAAs in the range of 102 − 104 ng/L were treated. The performance of the flow-through cell was assessed and compared with synthetic solutions for the oxidation of two representative PFAAs: perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Subsequently, the effect of current density and the variability of leachates composition was investigated for the electrochemical oxidation of PFAAs in real landfill leachates. Non-detect levels and >90% degradation was reached for PFOS and PFOA after 2 h of treatment for all leachates tested. Decreasing trends for perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), and perfluorohexanesulphonic acid (PFHxS), and increasing trends for perfluoropentanoic (PFPeA), perfluorobutanoic (PFBA), and perfluorobutanesulphonic acid (PFBS) were observed. The total PFAAs removal ranged from −138.6 to 73.5%. Correlations between the composition of the leachates and PFAAs removal percentages were determined. Overall, the results show the potential of electrochemical oxidation to oxidize PFAAs present in high strength water such as landfill leachates.

The Impact of Smoking on the Association between Perfluoroalkyl Acids (PFAS) and Thyroid Hormones: A National Health and Nutrition Examination Survey Analysis.

Perfluoroalkyl acids (PFAS) are known endocrine disrupting chemicals, potentially affecting thyroid function. Smoking has been associated with PFAS levels as well as with thyroid function. The impact of smoking on the association between PFAS and thyroid function remains to be elucidated, so the objective was to assess the effect of PFAS exposure on thyroid function in the general population, stratified by smoking status, using the National Health and Nutrition Examination Survey (NHANES). NHANES adult participants who were part of the 2011–2012 laboratory subsample and had PFAS and thyroid function measured were included (n = 1325). Adjusted linear regression models and stratified analyses were performed. There was a significant positive association between perfluorooctanesulfonic acid (PFOS) (p = 0.003), perfluorononanoic acid (PFNA) (p = 0.014), total PFAS (p = 0.004) concentrations and free T4 (FT4). No significant associations were found between perfluorooctanoic acid (PFOA), PFOS, perfluorohexane sulfonate (PFHxS), PFNA, total PFAS and total T4 (TT4) or thyroid stimulating hormone (TSH). In non-smokers, a significant positive association was found between PFOS (p = 0.003), PFHxS (p = 0.034), PFNA (p = 0.012), total PFAS (p = 0.003) and FT4 while no significant associations were found in smokers. The present study showed that increased PFAS exposure was associated with increased FT4 in non-smokers, while no association was found in smokers. These results confirm that smoking modifies the association between PFAS exposure and thyroid function.

Characterizing and Comparing Per- and Polyfluoroalkyl Substances in Commercially Available Biosolid and Organic Non-Biosolid-Based Products.

There is increasing concern over the presence of per- and polyfluoroalkyl substances (PFAS) in biosolids, while sales in commercially available biosolid-based products used as soil amendments are also increasing. Here, the occurrence of 17 perfluoroalkyl acids (PFAAs) present in 13 commercially available biosolid-based products, six organic composts (manure, mushroom, peat, and untreated wood), and one food and yard waste compost were studied. The PFAA concentration ranges observed are as follows: biosolid-based products (9.0-199 μg/kg) > food and yard waste (18.5 μg/kg) > other organic products (0.1-1.1 μg/kg). Analysis of 2014, 2016, and 2018 bags produced from one product line showed a temporal decrease in the total PFAAs (181, 101, and 74 μg/kg, respectively). The total oxidizable precursor (TOP) assay revealed the presence of PFAA precursors in the biosolid-based products at much higher levels, when the soluble carbon was removed by the ENVI-Carb clean-up prior to the TOP assay. Time-of-flight mass spectrometry confirmed the presence of three sulfonamides, two fluorotelomer sulfonates, and several polyfluoroalkyl phosphate diesters. Pore-water concentrations of water-saturated products were primarily of short-chain PFAAs and increased with increasing PFAA concentrations in the products. A strong positive log-linear correlation between organic carbon (OC)-normalized PFAA partition coefficients and the number of CFn units indicates that OC is a good predictor of PFAA release concentrations.

Advanced PFAS precursor digestion methods for biosolids

Environmental contextThe majority of biosolids produced in Australia from wastewater treatment processes are applied to agricultural land for beneficial use. We have demonstrated, through improvements to the analytical method, that levels of PFAS in biosolids are significantly higher than historically understood. The land application of biosolids could result in sensitive environments being exposed to PFAS at levels higher than previously anticipated. AbstractThe current industry standard for per- and polyfluoroalkyl substances (PFAS) analysis is for the measurement of only 28 PFAS, even though there are greater than 4700 PFAS known to be in existence. The total oxidisable precursor (TOP) assay, originally published by Houtz and Sedlak, is widely used as an estimate of the total perfluoro alkyl acids (PFAA) content of a sample, particularly in wastewater and biosolid matrices. The total PFAA content is an important measure of potential environmental contamination, which assists in the inference of potential harm that may occur from both well characterised PFAS, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), as well as lesser known precursor compounds and their breakdown products. With the majority of Australian biosolids beneficially applied to land, it is important to understand the future PFAS capacity before they are land applied to maintain the preservation of our agricultural and environmental assets. Our investigation of the TOP method and its application to biosolids involves a comparison of the Houtz and Sedlak method with a modified version coupled with a hydrogen peroxide pretreatment. The underperformance of the previously published method is demonstrated by its inability to sufficiently digest PFAS within biosolids. Therefore, the Houtz and Sedlak method significantly underestimated the levels of PFAS compared with the modified method, which showed a 10-fold increase in the measured PFAS after digestion. Further improvement of this modified method may provide a greater degree of accuracy for the TOP assay. The significant underestimation of the total PFAS load and, therefore, potential environmental harm has significant implications for public and agricultural health and compliance with regulatory limits.