Per- and polyfluoroalkyl substances (PFAS) in river discharge: Modeling loads upstream and downstream of a PFAS manufacturing plant in the Cape Fear watershed, North Carolina

Evaluation and prediction of anthropogenic impacts on long-term multimedia fate and health risks of PFOS and PFOA in the Elbe River Basin

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have aroused great concern owing to their widespread occurrence and toxic effects. However, their long-term trends and multimedia fate remain largely unknown. Here, we investigate the spatiotemporal characteristics and periodic oscillations of PFOS and PFOA in the Elbe River between 2010 and 2021. Anthropogenic emission inventories and multimedia fugacity model were developed to analyse their historical and future transport fates and quantify related human risks in each medium for the three age groups. The results show that average PFOS and PFOA concentrations in the Elbe River were 4.08 and 3.41 ng/L, declining at the annual rate of 7.36% and 4.98% during the study period, respectively. Periodic oscillations of their concentrations and mass fluxes were most pronounced at 40-60 and 20-40 months. The multimedia fugacity model revealed that higher concentrations occurred in fish (PFOS: 14.29, PFOA: 0.40 ng/g), while the soil was their dominant sink (PFOS: 179, PFOA: 95 tons). The exchange flux between water and sediment was the dominant pathway in multimedia transportation (397 kg/year). Although PFOS and PFOA concentrations are projected to decrease by 22.41% and 50.08%, respectively, from 2021 to 2050, the hazard quotient of PFOS in fish is a low hazard. This study provides information for the assessment of PFOS and PFOA pollution in global watersheds and the development of related mitigation policies, such as banning fish predation in polluted rivers, to mitigate their risks.

Structure-specific variation in per- and polyfluoroalkyl substances toxicity among genetically diverse Caenorhabditis elegans strains

Background

There are >14,500 structurally diverse per- and polyfluoroalkyl substances (PFAS). Despite knowledge that these "forever chemicals" are in 99% of humans, mechanisms of toxicity and adverse health effects are incompletely known. Furthermore, the contribution of genetic variation to PFAS susceptibility and health consequences is unknown.

Objectives

We determined the toxicity of a structurally distinct set of PFAS in twelve genetically diverse strains of the genetic model system Caenorhabditis elegans.

Methods

Dose-response curves for four perfluoroalkyl carboxylic acids (PFNA, PFOA, PFPeA, and PFBA), two perfluoroalkyl sulfonic acids (PFOS and PFBS), two perfluoroalkyl sulfonamides (PFOSA and PFBSA), two fluoroether carboxylic acids (GenX and PFMOAA), one fluoroether sulfonic acid (PFEESA), and two fluorotelomers (6:2 FCA and 6:2 FTS) were determined in the C. elegans laboratory reference strain, N2, and eleven genetically diverse wild strains. Body length was quantified by image analysis at each dose after 48 hr of developmental exposure of L1 arrest-synchronized larvae to estimate effective concentration values (EC50).

Results

There was a significant range in toxicity among PFAS: PFOSA > PFBSA ≈ PFOS ≈ PFNA > PFOA > GenX ≈ PFEESA > PFBS ≈ PFPeA ≈ PFBA. Long-chain PFAS had greater toxicity than short-chain, and fluorosulfonamides were more toxic than carboxylic and sulfonic acids. Genetic variation explained variation in susceptibility to PFBSA, PFOS, PFBA, PFOA, GenX, PFEESA, PFPeA, and PFBA. There was significant variation in toxicity among C. elegans strains due to chain length, functional group, and between legacy and emerging PFAS.

Conclusion

C. elegans respond to legacy and emerging PFAS of diverse structures, and this depends on specific structures and genetic variation. Harnessing the natural genetic diversity of C. elegans and the structural complexity of PFAS is a powerful New Approach Methodology (NAM) to investigate structure-activity relationships and mechanisms of toxicity which may inform regulation of other PFAS to improve human and environmental health.

Per-and polyfluoroalkyl (PFAS) eternal pollutants: Sources, environmental impacts and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have become a growing environmental concern due to their tangible impacts on human health. However, due to the large number of PFAS compounds and the analytical difficulty to identify all of them, there are still some knowledge gaps not only on their impact on human health, but also on how to manage them and achieve their effective degradation. PFAS compounds originate from man-made chemicals that are resistant to degradation because of the presence of the strong carbon-fluorine bonds in their chemical structure. This review consists of two parts. In the first part, the environmental effects of fluorinated compound contamination in water are covered with the objective to highlight how their presence in the environment adversely impacts the human health. In the second part, the focus is put on the different techniques available for the degradation and/or separation of PFAS compounds in different types of waters. Examples of removal/treatment of PFAS present in either surface or ground water are presented.

Identifying PFAS hotspots in surface waters of South Carolina using a new optimized total organic fluorine method and target LC-MS/MS

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of concern due to their long persistence in the environment, toxicity, and widespread presence in humans and wildlife. Knowledge regarding the extent of PFAS contamination in the environment is limited due to the need for analytical methods that can reliably quantify all PFAS, since traditional target methods using liquid chromatography (LC)-mass spectrometry (MS) fail to capture many. For a more comprehensive analysis, a total organic fluorine (TOF) method can be used as a screening tool. We combined TOF analysis with target LC-MS/MS analysis to create a statewide PFAS hotspot map for surface waters throughout South Carolina. Thirty-eight of 40 locations sampled contained detectable concentrations of organic fluorine (above 100 ng/L). Of the 33 target PFAS analyzed using LC-MS/MS, the most prevalent were perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA), and perfluorohexanesulfonate (PFHxS). On average, LC-MS/MS only accounted for 2 % of the TOF measured. Locations with high TOF did not necessarily correlate to high total quantified PFAS concentrations and vice-versa, demonstrating the limitations of target PFAS analysis and indicating that LC-MS may miss highly contaminated sites. Results suggest that future surveys should utilize TOF to more comprehensively capture PFAS in water bodies.

Non-Targeted PFAS Suspect Screening and Quantification of Drinking Water Samples Collected through Community Engaged Research in North Carolina's Cape Fear River Basin

A community engaged research (CER) approach was used to provide an exposure assessment of poly- and perfluorinated (PFAS) compounds in North Carolina residential drinking water. Working in concert with community partners, who acted as liaisons to local residents, samples were collected by North Carolina residents from three different locations along the Cape Fear River basin: upper, middle, and lower areas of the river. Residents collected either drinking water samples from their homes or recreational water samples from near their residence that were then submitted by the community partners for PFAS analysis. All samples were processed using weak anion exchange (WAX) solid phase extraction and analyzed using a non-targeted suspect screening approach as well as a quantitative approach that included a panel of 45 PFAS analytes, several of which are specific to chemical industries near the collection site locations. The non-targeted approach, which utilized a suspect screening list (obtained from EPA CompTox database) identified several PFAS compounds at a level two confidence rating (Schymanski scale); compounds identified included a fluorinated insecticide, a fluorinated herbicide, a PFAS used in polymer chemistry, and another that is used in battery production. Notably, at several locations, PFOA (39.8 ng/L) and PFOS (205.3 ng/L) were at levels that exceeded the mandatory EPA maximum contaminant level (MCL) of 4 ng/L. Additionally, several sites had detectable levels of PFAS that are unique to a local chemical manufacturer. These findings were communicated back to the community partners who then disseminated this information to the local residents to help empower and aid in making decisions for reducing their PFAS exposure.

Assessing Per- and Polyfluoroalkyl Substances (PFAS) in Fish Fillet Using Non-Targeted Analyses

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of man-made chemicals that are persistent and highly stable in the environment. Fish consumption has been identified as a key route of PFAS exposure for humans. However, routine fish monitoring targets only a handful of PFAS, and non-targeted analyses have largely only evaluated fish from heavily PFAS-impacted waters. Here, we evaluated PFAS in fish fillets from recreational and drinking water sources in central North Carolina to assess whether PFAS are present in these fillets that would not be detected by conventional targeted methods. We used liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) to collect full scan feature data, performed suspect screening using an in-house library of 100 PFAS for high confidence feature identification, searched for additional PFAS features using non-targeted data analyses, and quantified perfluorooctane sulfonic acid (PFOS) in the fillet samples. A total of 36 PFAS were detected in the fish fillets, including 19 that would not be detected using common targeted methods, with a minimum of 6 and a maximum of 22 in individual fish. Median fillet PFOS levels were concerningly high at 11.6 to 42.3 ppb, and no significant correlation between PFOS levels and number of PFAS per fish was observed. Future PFAS monitoring in this region should target more of these 36 PFAS, and other regions not considered heavily PFAS contaminated should consider incorporating non-targeted analyses into ongoing fish monitoring studies.

Occurrence, bioaccumulation, fate, and risk assessment of emerging pollutants in aquatic environments: A review

Significant concerns on a global scale have been raised in response to the potential adverse impacts of emerging pollutants (EPs) on aquatic creatures. We have carefully reviewed relevant research over the past 10 years. The study focuses on five typical EPs: pharmaceuticals and personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), drinking water disinfection byproducts (DBPs), brominated flame retardants (BFRs), and microplastics (MPs). The presence of EPs in the global aquatic environment is source-dependent, with wastewater treatment plants being the main source of EPs. Multiple studies have consistently shown that the final destination of most EPs in the water environment is sludge and sediment. Simultaneously, a number of EPs, such as PFASs, MPs, and BFRs, have long-term environmental transport potential. Some EPs exhibit notable tendencies towards bioaccumulation and biomagnification, while others pose challenges in terms of their degradation within both biological and abiotic treatment processes. The results showed that, in most cases, the ecological risk of EPs in aquatic environments was low, possibly due to potential dilution and degradation. Future research topics should include adding EPs detection items for the aquatic environment, combining pollution, and updating prediction models.

Biological effects of perfluoroalkyl substances on running water ecosystems: A case study in Beiluo River, China

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that pose a threat to the biodiversity of the Beiluo River, a polluted watercourse on the Loess Plateau impacted by diverse human activities. However, the occurrence, spatial distribution, and substitution characteristics of PFASs in this region remain unclear. This study aimed to unravel PFAS distribution patterns and their impact on the aquatic ecosystems of the Beiluo River Basin. The total PFAS concentration in the area ranged from 16.64-35.70 ng/L, with predominantly perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), collectively contributing 94%. The Mantel test revealed threats to aquatic communities from both legacy long-chain (perfluorooctanoic acid and sodium perfluorooctane sulfonic acid) and emerging (6:2 fluorotelomer sulfonic acid, 2-Perfluorohexyl ethanoic acid, and hexafluoropropylene oxide dimer acid (Gen-X)) PFSAs. The canonical correspondence analysis ordination indicated that trace quantities of emerging PFASs, specifically 2-Perfluorohexyl ethanoic acid and hexafluoropropylene oxide dimer acid (Gen-X), significantly influenced geographical variations in aquatic communities. In conclusion, this study underscores the importance of comprehensively exploring the ecological implications and potential risks associated with PFASs in the Beiluo River Basin.

Comparison of the PFAS and physical-chemical parameter fluctuations between an ash landfill and a MSW landfill

Studies of per- and polyfluoroalkyl substances (PFAS) fluctuations at landfills have focused on municipal solid waste (MSW) leachate. Few studies exist that evaluate fluctuations (defined by the coefficient of variation, CV) in MSW incinerator ash (MSWA) landfill leachate and that evaluate PFAS fluctuations in stormwater, groundwater, and treated liquids on-site. In this study, aqueous landfill samples (leachate, treated leachate, stormwater, gas condensate, ambient groundwater, and effluent from a groundwater remediation system) were collected from a MSW and an MSWA landfill geographically located within close proximity (less than 40 km). The objective of this study was to compare the leachate compositions between these two landfill types and to evaluate temporal variations. Results indicated that the CV of total detected PFAS concentrations in leachate was higher for the MSW landfill (CV = 43 %) compared to the MSWA landfill (CV = 16 %). The total detected PFAS concentration in MSW leachate samples (mean: 9641 ng/L) was higher than in MSWA leachate samples (mean: 2621 ng/L) (p < 0.05). Within a landfill, PFAS concentrations were correlated (rs > 0.6, p < 0.05) with alkalinity, total organic carbon (TOC), and ammonia. Results from the on-site leachate treatment system at the MSW landfill indicated reductions in COD, TOC, and ammonia; however, the ∑26PFAS concentration increased 3 % after the treatment. Overall, results demonstrated that differences between landfill types and fluctuations in PFAS within landfills should be considered when designing landfill leachate collection and treatment systems to remove PFAS. The comparative analysis in this study can provide insights into optimizing leachate management for MSW and MSWA landfills.

Investigating the applicability and assumptions of the regression relationship between flow discharge and nitrogen concentrations for load estimation

The regression relationship between water discharge rates and nutrient concentrations can provide a quick and straightforward way to estimate nutrient loads. However, recent studies indicated that the relationship might produce large biases in load estimates and, therefore, may not be applicable in certain types of cases. The goal of this study is to explore the theoretical reasons behind the selective applicability of the regression relationship between flow rates and nitrate + nitrite concentrations. For this study, we examined daily flow and nitrate + nitrite concentration observations made at the outlets of 22 watersheds monitored by the Heidelberg Tributary Loading Program (HTLP). The statistical relationship between the flow rates and concentrations was explored using regression equations offered by the LOAD ESTimator (LOADEST). Results demonstrated that the use of the regression equations provided nitrate + nitrite load estimates at acceptable accuracy levels (N S E ≥ 0.35 and | P B I A S | ≤ 30.0 %) in 14 watersheds (64 % of 22 study watersheds). The regression relationships provided highly biased results at eight watersheds (36 %), implying their limited applicability. The heteroscedasticity of the residuals led to the high bias and resulting inaccurate regression, which was commonly found in watersheds where low flow had high nitrate + nitrite concentration variations. Conversely, the regression relationships provided acceptable accuracy for watersheds that had a relatively constant variance of the nitrate + nitrite concentrations. The results indicate that the homoscedasticity of residuals is the key assumption to be satisfied to estimate nitrate + nitrite loads from a statistical regression between flow discharge and nitrate + nitrite concentrations. The transport capacity (capacity-limited) concept implicitly assumed in the regression relationship between flow discharge and nitrate + nitrite concentrations is not always applicable, especially to agricultural areas in which nitrate + nitrite loads are highly variable depending on management practices (supply-limited). The findings suggest that the regression relationship should be carefully applied to areas in which intensive agricultural activities, including crop management and conservation practices, are implemented. Thus, the transport capacity concept is reasonably regarded to contribute to the homoscedasticity of residuals.

Investigation of Sources of Fluorinated Compounds in Private Water Supplies in an Oil and Gas-Producing Region of Northern West Virginia

Per- and polyfluoroalkyl substances (PFASs) are a class of toxic organic compounds that have been widely used in consumer applications and industrial activities, including oil and gas production. We measured PFAS concentrations in 45 private wells and 8 surface water sources in the oil and gas-producing Doddridge, Marshall, Ritchie, Tyler, and Wetzel Counties of northern West Virginia and investigated relationships between potential PFAS sources and drinking water receptors. All surface water samples and 60% of the water wells sampled contained quantifiable levels of at least one targeted PFAS compound, and four wells (8%) had concentrations above the proposed maximum contaminant level (MCL) for perfluorooctanoic acid (PFOA). Individual concentrations of PFOA and perfluorobutanesulfonic acid exceeded those measured in finished public water supplies. Total targeted PFAS concentrations ranged from nondetect to 36.8 ng/L, with surface water concentrations averaging 4-fold greater than groundwater. Semiquantitative, nontargeted analysis showed concentrations of emergent PFAS that were potentially higher than targeted PFAS. Results from a multivariate latent variable hierarchical Bayesian model were combined with insights from analyses of groundwater chemistry, topographic characteristics, and proximity to potential PFAS point sources to elucidate predictors of PFAS concentrations in private wells. Model results reveal (i) an increased vulnerability to contamination in upland recharge zones, (ii) geochemical controls on PFAS transport likely driven by adsorption, and (iii) possible influence from nearby point sources.

Uncovering per- and polyfluoroalkyl substances (PFAS) with nontargeted ion mobility spectrometry-mass spectrometry analyses

Because of environmental and health concerns, legacy per- and polyfluoroalkyl substances (PFAS) have been voluntarily phased out, and thousands of emerging PFAS introduced as replacements. Traditional analytical methods target a limited number of mainly legacy PFAS; therefore, many species are not routinely assessed in the environment. Nontargeted approaches using high-resolution mass spectrometry methods have therefore been used to detect and characterize unknown PFAS. However, their ability to elucidate chemical structures relies on generation of informative fragments, and many low concentration species are not fragmented in typical data-dependent acquisition approaches. Here, a data-independent method leveraging ion mobility spectrometry (IMS) and size-dependent fragmentation was developed and applied to characterize aquatic passive samplers deployed near a North Carolina fluorochemical manufacturer. From the study, 11 PFAS structures for various per- and polyfluorinated ether sulfonic acids and multiheaded perfluorinated ether acids were elucidated in addition to 36 known PFAS. Eight of these species were previously unreported in environmental media, and three suspected species were validated.

Extracellular Vesicles altered by a Per- and Polyfluoroalkyl Substance Mixture: In Vitro Dose-Dependent Release, Chemical Content, and MicroRNA Signatures involved in Liver Health

Per- and polyfluoroalkyl substances (PFAS) have emerged as high priority contaminants due to their ubiquity and pervasiveness in the environment. Numerous PFAS co-occur across sources of drinking water, including areas of North Carolina (NC) with some detected concentrations above the Environmental Protection Agency's health advisory levels. While evidence demonstrates PFAS exposure induces harmful effects in the liver, the involvement of extracellular vesicles (EVs) as potential mediators of these effects has yet to be evaluated. This study set out to evaluate the hypothesis that PFAS mixtures induce dose-dependent release of EVs from liver cells, with exposures causing differential loading of microRNAs (miRNAs) and PFAS chemical signatures. To test this hypothesis, a defined PFAS mixture was prioritized utilizing data collected by the NC PFAS Testing Network. This mixture contained three substances, PFOS, PFOA, and PFHxA, selected based upon co-occurrence patterns and the inclusion of both short-chain (PFHxA) and long-chain (PFOA and PFOS) substances. HepG2 liver cells were exposed to equimolar PFAS, and secreted EVs were isolated from conditioned media and characterized for count and molecular content. Exposures induced a dose-dependent release of EVs carrying miRNAs that were differentially loaded upon exposure. These altered miRNA signatures were predicted to target mRNA pathways involved in hepatic fibrosis and cancer. Chemical concentrations of PFOS, PFOA, and PFHxA were also detected in both parent HepG2 cells and their released EVs, specifically within a 15-fold range after normalizing for protein content. This study therefore established EVs as novel biological responders and measurable endpoints for evaluating PFAS-induced toxicity.

Characterizing the long-term occurrence and anthropogenic drivers of per- and polyfluoroalkyl substances in surface water of the Rhine River

Per- and polyfluoroalkyl substances (PFAS) raise significant concerns due to their persistence, bioaccumulation potential, and toxicity to both ecosystems and human health. However, the long-term trends of PFAS in aquatic environments remain inadequately explored. In this study, we systematically assessed the spatiotemporal distribution, periodic fluctuations, source apportionment, and risk evaluation of 12 PFAS in the Rhine River based on the long-term measuring data collected from 2007 to 2019. The study revealed that the mean concentration and mass flux of total PFAS during this period were 32.83 ng L-1 and 6.36 × 104 μg s-1, declining at an annual rate of 3.70% and 3.82%, respectively. Wavelet analysis demonstrated that the most prominent periodic oscillation of PFAS was 40-60 months. Regarding the sources of PFAS, we employed the self-organizing map (SOM) and the positive matrix factorization (PMF) model for source apportionment. The results indicated that the primary sources of PFAS were agrochemical, pharmaceutical and textile industries, accounting for 38.1% of the total concentration. The contribution from household contamination, tannery industry, and coating materials has increased annually. In contrast, the share of electrochemical fluorination and chemical recycling has shown a continuous decline. The risk quotient (RQ) and hazard quotient (HQ) calculations for three age groups indicated that PFAS exposure did not pose a significant risk to ecological or human health. Implementing source-oriented mitigation strategies is crucial to effectively reduce the ecological and human health risks of PFAS in receiving waters.

PFAS levels in paired drinking water and serum samples collected from an exposed community in Central North Carolina

The community of Pittsboro, North Carolina has been documented to have extensive per- and polyfluoroalkyl substances (PFAS) contamination in its drinking water source, the Haw River, over the last 20 years. However, a detailed exposure assessment has never been conducted. In this study, we sought to characterize the PFAS in paired drinking water and blood samples collected from a small cohort of Pittsboro residents (n = 49). Drinking water and serum from blood were collected from adults in late 2019 and early 2020 and were analyzed to quantify 13 PFAS analytes. In order to explore potential health effects of PFAS exposure, serum was further analyzed for clinical chemistry endpoints that could be potentially associated with PFAS (e.g., cholesterol, liver function biomarkers). PFAS were detected in all serum samples, and some serum PFAS concentrations were 2 to 4 times higher than the median U.S. serum concentrations reported in the general U.S. population. Of the 13 PFAS in drinking water, perfluorohexanoic acid (PFHxA) was measured at the highest concentrations. PFAS levels in the current drinking water were not associated with current serum PFAS, suggesting that the serum PFAS in this cohort likely reflects historical exposure to PFAS with long half-lives (e.g., PFOS and PFOA). However, one PFAS with a shorter half-life (PFHxA) was observed to increase in serum, reflecting the temporal variability of PFHxA in river and drinking water. Statistical analyses indicated that serum PFOA and PFHxS were positively associated with total cholesterol and non-HDL cholesterol. No serum PFAS was associated with HDL cholesterol. In the clinical chemistry analyses, serum PFHxA was found to be negatively associated with electrolytes and liver enzymes (e.g., AST and ALT), and serum PFOS was found to be positively associated with the ratio of blood urea nitrogen to creatinine (BUN:Cre). While small in size, this study revealed extensive exposure to PFAS in Pittsboro and associations with clinical blood markers, suggesting potential health impacts in community residents.

Domestic Dogs and Horses as Sentinels of Per- and Polyfluoroalkyl Substance Exposure and Associated Health Biomarkers in Gray's Creek North Carolina

Central North Carolina (NC) is highly contaminated with per- and polyfluoroalkyl substances (PFAS), in part due to local fluorochemical production. Little is known about the exposure profiles and long-term health impacts for humans and animals that live in nearby communities. In this study, serum PFAS concentrations were determined using liquid chromatography high-resolution mass spectrometry and diagnostic clinical chemistry endpoints were assessed for 31 dogs and 32 horses that reside in Gray's Creek NC at households with documented PFAS contamination in their drinking water. PFAS were detected in every sample, with 12 of the 20 PFAS detected in ≥50% of samples from each species. The average total PFAS concentrations in horses were lower compared to dogs who had higher concentrations of PFOS (dogs 2.9 ng/mL; horses 1.8 ng/mL), PFHxS (dogs 1.43 ng/mL, horses < LOD), and PFOA (dogs 0.37 ng/mL; horses 0.10 ng/mL). Regression analysis highlighted alkaline phosphatase, glucose, and globulin proteins in dogs and gamma glutamyl transferase in horses as potential biomarkers associated with PFAS exposure. Overall, the results of this study support the utility of companion animal and livestock species as sentinels of PFAS exposure differences inside and outside of the home. As in humans, renal and hepatic health in domestic animals may be sensitive to long-term PFAS exposures.

Environmental and health impacts of PFAS: Sources, distribution and sustainable management in North Carolina (USA)

Poly- and perfluoroalkyl substances (PFAS) are a class of manufactured chemicals that have recently attracted a great deal of attention from environmental regulators and the general public because of their high prevalence, resistance to degradation, and potential toxicity. This review summarizes the current state of PFAS and its effects on the environment of North Carolina, USA. Specific emphasis has been placed to identify i) the sources of PFAS in North Carolina ii) distribution of PFAS in different environmental segments of North Carolina, including surface water, groundwater, air, and sediment iii) drinking water contamination iv) impact of PFAS on human health v) PFAS accumulation in fish and other biota vi) status of PFAS removal from drinking water and finally vi) socioeconomic impact of PFAS uncertainties. Continuous discharges of PFAS occur in the North Carolina environment from direct and indirect sources, including manufacturing sites, firefighting foam, waste disposal and treatment plants, landfill leachate, and industrial emissions. PFAS are widespread in many environmental segments of North Carolina. They are more likely to be detected in surface and groundwater sediments and can enter aquatic bodies through direct discharge and wet and dry deposition of emissions. Eventually, some adverse effects of PFAS have already been reported in North Carolina residents who could have been exposed to the chemicals through contaminated drinking water. Furthermore, PFAS were also found in blood samples from fish and alligators. PFAS were confirmed to be present in water, sediment, organic compounds, and aquatic species at all levels of the food web. However, there is still a substantial amount of work to be done to understand the actual contamination by PFAS in North Carolina comprehensively.

70 analyte PFAS test method highlights need for expanded testing of PFAS in drinking water

In this community-led pilot study we sought to investigate the utility of expanded per- and polyfluoroalkyl substances (PFAS) testing for drinking water, using a targeted analysis for 70 PFAS and the Total Oxidizable Precursor (TOP) Assay which can indicate the presence of precursor PFAS. PFAS were detected in 30 out of 44 drinking water samples across 16 states; 15 samples would exceed US EPA's proposed maximum contaminant levels for six PFAS. Twenty-six unique PFAS were identified, including 12 not covered by either US EPA Methods 537.1 or 533. An ultrashort chain PFAS, PFPrA, had the highest frequency of detection, occurring in 24 of 30 samples. It was also the PFAS reported at the highest concentration in 15 of these samples. We created a data filter to model how these samples would be reported under the upcoming fifth Unregulated Contaminant Monitoring Rule (UCMR5) requirements. All of the 30 samples with PFAS quantified by the 70 PFAS test had one or more PFAS present that would not be captured if the UCMR5 reporting requirements were followed. Our analysis suggests the upcoming UCMR5 will likely underreport PFAS in drinking water, due to limited coverage and higher minimum reporting limits. Results were inconclusive on the utility of the TOP Assay for monitoring drinking water. The results from this study provide important information to community participants regarding their current PFAS drinking water exposure. In addition, these results suggest gaps that need to be addressed by regulatory and scientific communities, in particular, the need for expanded targeted analysis of PFAS, the development of a sensitive, broad spectrum PFAS test, and further investigation into ultrashort chain PFAS.

Locomotion and brain gene expression exhibit sex-specific non-monotonic dose-response to HFPO-DA during Drosophila melanogaster lifespan

BACKGROUND

Legacy per- and polyfluoroalkyl substances (PFAS), known for their environmental persistence and bio-accumulative properties, have been phased out in the U.S. due to public health concerns. A newer polymerization aid used in the manufacture of some fluoropolymers, hexafluoropropylene oxide-dimer acid (HFPO-DA), has lower reported bioaccumulation and toxicity, but is a potential neurotoxicant implicated in dopaminergic neurodegeneration.

OBJECTIVE

We investigated HFPO-DA's bio-accumulative potential and sex-specific effects on lifespan, locomotion, and brain gene expression in fruit flies.

METHODS

We quantified bioaccumulation of HFPO-DA in fruit flies exposed to 8.7×10⁴µg/L of HFPO-DA in the fly media for 14 days via UHPLC-MS. Long-term effect on lifespan was determined by exposing both sexes to 8.7×10² - 8.7×10⁵µg/L of HFPO-DA in media. Locomotion was measured following 3, 7, and 14 days of exposures at 8.7×10¹ - 8.7×10⁵µg/L of HFPO-DA in media, and high-throughput 3'-end RNA-sequencing was used to quantify gene expression in fly brains across the same time points.

RESULTS

Bioaccumulation of HFPO-DA in fruit flies was not detected. HFPO-DA-induced effects on lifespan, locomotion, and brain gene expression, and lowest adverse effect level (LOAEL) showed sexually dimorphic patterns. Locomotion scores significantly decreased in at least one dose at all time points for females and only at 3-day exposure for males, while brain gene expression exhibited non-monotonic dose-response. Differentially expressed genes correlated to locomotion scores revealed sex-specific numbers of positively and negatively correlated genes per functional category.

CONCLUSION

Although HFPO-DA effects on locomotion and survival were significant at doses higher than the US EPA reference dose, the brain transcriptomic profiling reveals sex-specific changes and neurological molecular targets; gene enrichments highlight disproportionately affected categories, including immune response: female-specific co-upregulation suggests potential neuroinflammation. Consistent sex-specific exposure effects necessitate blocking for sex in experimental design during HFPO-DA risk assessment.

A field-validated equilibrium passive sampler for the monitoring of per- and polyfluoroalkyl substances (PFAS) in sediment pore water and surface water

A simple equilibrium passive sampler, consisting of water in an inert container capped with a rate-limiting barrier, for the monitoring of per- and polyfluoroalkyl substances (PFAS) in sediment pore water and surface water was developed and tested through a series of laboratory and field experiments. The objectives of the laboratory experiments were to determine (1) the membrane type that could serve as the sampler's rate-limiting barrier, (2) the mass transfer coefficient of environmentally relevant PFAS through the selected membrane, and (3) the performance reference compounds (PRCs) that could be used to infer the kinetics of PFAS diffusing into the sampler. Of the membranes tested, the polycarbonate (PC) membrane was deemed the most suitable rate-limiting barrier, given that it did not appreciably adsorb the studied PFAS (which have ≤8 carbons), and that the migration of these compounds through this membrane could be described by Fick's law of diffusion. When employed as the PRC, the isotopically labelled PFAS M₂PFOA and M₄PFOS were able to predict the mass transfer coefficients of the studied PFAS analytes. In contrast, the mass transfer coefficients were underpredicted by Br^- and M₃PFPeA. For validation, the PC-based passive samplers consisting of these four PRCs, as well as two other PRCs (i.e., M₈PFOA and C₈H₁₇SO₃^-), were deployed in the sediment and water at a PFAS-impacted field site. The concentration-time profiles of the PRCs indicated that the samplers deployed in the sediment required at least 6 to 7 weeks to reach 90% equilibrium. If the deployment times are shorter (e.g., 2 to 4 weeks), PFAS concentrations at equilibrium could be estimated based on the concentrations of the PRCs remaining in the sampler at retrieval. All PFAS concentrations determined via this approach were within a factor of two compared to those measured in the mechanically extracted sediment pore water and surface water samples obtained adjacent to the sampler deployment locations. Neither biofouling of the rate-limiting barrier nor any physical change to it was observed on the sampler after retrieval. The passive sampler developed in this study could be a promising tool for the monitoring of PFAS in pore water and surface water.

Embryonic exposure to PFAS causes long-term, compound-specific behavioral alterations in zebrafish

Per- and polyfluoroalkyl substances (PFAS) are commonly used as surfactants and coatings for industrial processes and consumer products. These compounds have been increasingly detected in drinking water and human tissue, and concern over their potential effects on health and development is growing. However, relatively little data are available for their potential impacts on neurodevelopment and the degree to which different compounds within this class may differ from one another in their neurotoxicity. The present study examined the neurobehavioral toxicology of two representative compounds in a zebrafish model. Zebrafish embryos were exposed to 0.1-100uM perfluorooctanoic acid (PFOA) or 0.01-1.0uM perfluorooctanesulfonic acid (PFOS) from 5 to 122 h post-fertilization. These concentrations were below threshold for producing increased lethality or overt dysmorphologies, and PFOA was tolerated at a concentration 100× higher than PFOS. Fish were maintained to adulthood, with behavioral assessments at 6 days, 3 months (adolescence) and 8 months of age (adulthood). Both PFOA and PFOS caused behavioral changes in zebrafish, but PFOS and PFOS produced strikingly different phenotypes. PFOA was associated with increased larval motility in the dark (100uM), and enhanced diving responses in adolescence (100uM) but not adulthood. PFOS was associated with a reversed light-dark response in the larval motility test (0.1-1uM), whereby the fish were more active in the light than the dark. PFOS also caused time-dependent changes in locomotor activity in the novel tank test during adolescence (0.1-1.0uM) and an overall pattern of hypoactivity in adulthood at the lowest concentration (0.01uM). Additionally, the lowest concentration of PFOS (0.01uM) reduced acoustic startle magnitude in adolescence, but not adulthood. These data suggest that PFOS and PFOA both produce neurobehavioral toxicity, but these effects are quite distinct from one another.

Verification of In Vivo Estrogenic Activity for Four Per- and Polyfluoroalkyl Substances (PFAS) Identified as Estrogen Receptor Agonists via New Approach Methodologies

Given concerns about potential toxicological hazards of the thousands of data-poor per- and polyfluorinated alkyl substances (PFAS) currently in commerce and detected in the environment, tiered testing strategies that employ high-throughput in vitro screening as an initial testing tier have been implemented. The present study evaluated the effectiveness of previous in vitro screening for identifying PFAS capable, or incapable, of inducing estrogenic responses in fish exposed in vivo. Fathead minnows (Pimephales promelas) were exposed for 96 h to five PFAS (perfluorooctanoic acid [PFOA]; 1H,1H,8H,8H-perfluorooctane-1,8-diol [FC8-diol]; 1H,1H,10H,10H-perfluorodecane-1,10-diol [FC10-diol]; 1H,1H,8H,8H-perfluoro-3,6-dioxaoctane-1,8-diol [FC8-DOD]; and perfluoro-2-methyl-3-oxahexanoic acid [HFPO-DA]) that showed varying levels of in vitro estrogenic potency. In agreement with in vitro screening results, exposure to FC8-diol, FC10-diol, and FC8-DOD caused concentration-dependent increases in the expression of transcript coding for vitellogenin and estrogen receptor alpha and reduced expression of insulin-like growth factor and apolipoprotein eb. Once differences in bioconcentration were accounted for, the rank order of potency in vivo matched that determined in vitro. These results provide a screening level benchmark for worst-case estimates of potential estrogenic hazards of PFAS and a basis for identifying structurally similar PFAS to scrutinize for putative estrogenic activity.

Improved export coefficient model for identification of watershed environmental risk areas

As a complex system under the joint action of man and nature, land use/cover directly or indirectly affects the environmental quality of the freshwater ecosystem. Studying the response of water environment quality to land use/cover change was significant to accurately simulate lake water quality and effectively enhance the management level. As an empirical model, the classical export coefficient model has been widely used and developed in agricultural non-point source pollution research because of its simple structure and convenient application. However, it assumes that the export coefficient of a particular type of land use/cover was constant, ignoring the influence of surface runoff and interception on the output intensity of pollutants in pollutant migration. This study improved the classical export coefficient model by adding factors such as precipitation, surface cover, and topography, evaluated the contribution of land use/cover to total nitrogen load into the lake in Dianchi Lake Basin, and applied the pollution assessment results to the identification of watershed environmental risk areas. The results showed that the improved export coefficient model could better simulate the relationship between land use/cover and total nitrogen load into Dianchi Lake from the basin. At the same time, spatial characteristics of the total nitrogen load contribution of the terrestrial could be represented. The high-risk areas in the basin were mainly cultivated land and construction areas with low vegetation coverage around lakes or downstream. The contribution per unit area to the TN load into the lake from areas with a high risk was 14.28 t/km², which was 3.47 times that of medium-high-risk areas and 52.28 times that of the medium-risk area. Land use control measures in high-risk areas in the basin should be further strengthened, especially in the lakeside zone.

Swimming with PFAS in public and private pools

Per- and polyfluoroalkyl substances (PFAS) are a class of anthropogenic chemicals used to provide water and stain resistance in many consumer products. Their widespread use, nearly ubiquitous presence across multiple environments, and growing list of adverse health effects has raised concerns among communities. PFAS have been frequently detected and quantified globally in wastewater, groundwater, surface and drinking water; however, the presence of PFAS in swimming pool water - a unique matrix in which constituents may concentrate through evaporation and which also may present a high risk of direct human exposure - has not been reported. Here, ultra-high performance liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS) was used to monitor 92 PFAS in 54 water samples collected from city, apartment, hotel, and personal swimming pools in six Florida cities. In total, 14 PFAS were detected with six perfluoroalkyl acids - perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorobutane sulfonate (PFBS) - detected in every sample. PFHxA accounted for 49% of all PFAS quantified in this study. PFAS profiles were compared between sites as a function of pool type, rate of use, and geographic location. Total ΣPFAS concentrations were similar across pool types, with both the highest (633 ng/L) and lowest (1.9 ng/L) measurements found in public city pools. Between sites, higher PFAS levels were observed in city pools in Miami, Melbourne and Tampa compared to Naples, Orlando and Gainesville. Our findings highlight the potential exposure of PFAS in an underexplored and yet important exposure pathway in communities.

Simplifying Nontargeted Analysis of PFAS in Complex Food Matrixes

Background

Per- and polyfluoroalkyl substances (PFAS) are a class of toxic environmental contaminants that are characterized by their high chemical stability and enormous structural diversity.

Objective

The limited availability of PFAS reference standards is the main motivation for developing nontargeted analytical methods. Current concepts are complex and rely on multiple filtering steps (e.g., assumption of homologous series, detection of mass defects, generic fragments, and spectra obtained from web-based sources).

Method

High-resolution mass spectrometry (HRMS)–based chromatograms of fish liver extracts were deconvoluted. Based on the ion abundance between the monoisotopic and the first isotopic peak, the number of carbons (C) was estimated for each extracted feature. A mass over carbon (m/C) and mass defect over carbon (md/C) ratio was calculated.

Results

PFAS-related peaks are strongly discriminated from matrix peaks when plotting m/C versus md/C. This enables nontarget detection of PFAS present at low µg/kg concentration in complex food matrixes.

Conclusions

The proposed concept is highly selective by revealing a relatively small number of high-probability PFAS candidates (features). The small number of surviving candidates permits the MS/MS-based confirmation of each feature. This strategy led to the finding of one PFAS not present in the reference standard solution, as well as the detection of an unexpected set of PFAS adducts.

Highlights

The proposed concept of mass over carbon versus mass defect over carbon is suited for the nontarget detection of low amounts of PFAS in complex matrixes. It should be capable of detecting any PFAS (F/H ratio should be &gt;1:1) regardless of the ionization mode.