Repeated Aqueous Film-Forming Foams Applications: Impacts on Polyfluoroalkyl Substances Retention in Saturated Soil

Historical practices at firefighter-training areas involved repeated aqueous film-forming foams (AFFFs) applications, resulting in source zones characterized by high concentrations of perfluoroalkyl and polyfluoroalkyl substances (PFAS). Repeated applications of AFFF composed of 14 anionic and 23 zwitterionic perfluoroalkyl substances (PFAS) were conducted on a single one-dimensional saturated soil column to quantify PFAS retention. An electrofluorination-based (3M) Milspec AFFF, which was above the mixture's critical micelle concentration (CMC), was at application strength (3%, v/v). Retention and retardation of PFAS mass increased with each successive AFFF addition, although the PFAS concentration profiles for subsequent applications differed from the initial. Greater degree of mass retention and retardation correlated with longer PFAS carbon-fluorine chain length and charged-headgroup type and as a function of AFFF application number. Anionic PFAS were increasingly retained with each subsequent AFFF application, while zwitterionic PFAS exhibited an alternating pattern of sorption and desorption. Surfactant-surfactant adsorption and competition during repeat AFFF applications that are at concentrations above the CMC resulted in adsorbed PFAS from the first application, changing the nature of the soil surface with preferential sorption of anionic PFAS and release of zwitterionic PFAS due to competitive elution. Applying a polyparameter quantitative structure-property relationship developed to describe sorption of AFFF-derived PFAS to uncontaminated, saturated soil was attempted for our experimental conditions. The model had been derived for data where AFFF is below the apparent CMC and our experimental conditions that included the presence of mixed micelles (aggregates consisting of different kinds of surfactants that exhibit characteristics properties different from micelles composed of a single surfactant) resulted in overall PFAS mass retained by an average of 27.3% ± 2.7% (standard error) above the predicted values. The correlation was significantly improved by adding a "micelle parameter" to account for cases where the applied AFFF was above the apparent CMC. Our results highlight the importance of interactions between the AFFF components that can only be investigated by employing complex PFAS mixtures at concentrations present in actual AFFF at application strength, which are above their apparent CMC. In firefighter-training areas (AFFF source zones), competitive desorption of PFAS may result in downgradient PFAS retention when desorbed PFAS become resorbed to uncontaminated soil.

Target and suspect per- and polyfluoroalkyl substances in fish from an AFFF-impacted waterway

A major source of toxic per- and polyfluoroalkyl substances (PFAS) is aqueous film-forming foams (AFFF) used in firefighting and training at airports and military installations, however, PFAS have many additional sources in consumer products and industrial processes. A field study was conducted on fish tissues from three reaches of the Columbia Slough, located near Portland International Airport, OR, that are affected by AFFF and other PFAS sources. Fishes including largescale sucker (Catostomus macrocheilus), goldfish (Carassius auratus), and largemouth bass (Micropterus salmoides) were collected in 2019 and 2020. Fish blood, liver, and fillet (muscle) were analyzed for target and suspect PFAS by liquid chromatography high resolution mass spectrometry (LC-HRMS). Data were analyzed for patterns by fish species, tissue type, and river reach. Thirty-three out of 50 target PFAS and additional suspect compounds were detected at least once during the study, at concentrations up to 856 ng/g. Seven carboxylic acids (PFOA, PFNA, PFDA, PFUdA, PFDoA, PFTrDA, PFTeDA), three sulfonates (PFHxS, PFOS, PFDS), three electrofluorination-based compounds (FBSA, FHxSA, FOSA), and two fluorotelomer-based compounds (8:2 FTS, 10:2 FTS) were the most frequently detected compounds in all tissue types. The C6 (PFHxS) to C10 (PFDS) homologs were detected with PFOS and FHxSA at concentrations 1-3 orders of magnitude greater than the other PFAS detected. This is the first report of Cl-PFOS, FPeSA, and FHpSA detected in fish tissue. In all fish samples, fillet concentrations of PFAS were the lowest, followed by liver, and blood concentrations of PFAS were the highest. Differences in PFAS concentrations were driven primarily by tissue types and to a lesser extent fish species, but weakly by river reach. The Oregon Health Authority modified an existing fish consumption advisory on the Columbia Slough to recommend no whole-body consumption of most fish to avoid elevated levels of PFOS in fish liver. Measured PFAS concentrations in fish tissues indicate the potential for adverse ecological effects.

Ecotoxicity and Accumulation of Perfluorononanoic Acid in the Fathead Minnow (Pimephales promelas) and an Approach to Developing Protective Thresholds in the Aquatic Environment Through Species Sensitivity Distribution

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment. Locations where PFAS-containing aqueous film-forming foam (AFFF) has been used or accidentally released have resulted in persistently high concentrations of PFAS, including in surface water that may be adjacent to release sites. Perfluorooctane sulfonic acid (PFOS) is most frequently measured near AFFF release sites; however, other PFAS are being quantified more frequently and, of those, perfluorononanoic acid (PFNA) is common. The goal of our study was to fill data gaps on PFNA toxicity to freshwater fish using the fathead minnow (Pimephales promelas). We aimed to understand how PFNA may impact apical endpoints following a 42-day exposure to mature fish and a 21-day exposure to second-generation larval fish. Exposure concentrations were 0, 124, 250, 500, and 1000 µg/L for both adult (F0) and larval (F1) generations. The most sensitive endpoint measured was development in the F1 generation at concentrations of ≥250 µg/L. The 10% and 20% effective concentration of the tested population for the F1 biomass endpoint was 100.3 and 129.5 µg/L, respectively. These data were collated with toxicity values from the primary literature on aquatic organisms exposed to PFNA for subchronic or chronic durations. A species sensitivity distribution was developed to estimate a screening-level threshold for PFNA. The resulting hazard concentration protective of 95% of the freshwater aquatic species was 55 µg PFNA/L. Although this value is likely protective of aquatic organisms exposed to PFNA, it is prudent to consider that organisms experience multiple stressors (including many PFAS) simultaneously; an approach to understand screening-level thresholds for PFAS mixtures remains an uncertainty within the field of ecological risk assessment. Environ Toxicol Chem 2023;42:2229-2236. © 2023 SETAC.

Target and Suspect Screening Integrated with Machine Learning to Discover Per- and Polyfluoroalkyl Substance Source Fingerprints

This study elucidates per- and polyfluoroalkyl substance (PFAS) fingerprints for specific PFAS source types. Ninety-two samples were collected from aqueous film-forming foam impacted groundwater (AFFF-GW), landfill leachate, biosolids leachate, municipal wastewater treatment plant effluent (WWTP), and wastewater effluent from the pulp and paper and power generation industries. High-resolution mass spectrometry operated with electrospray ionization in negative mode was used to quantify up to 50 target PFASs and screen and semi-quantify up to 2,266 suspect PFASs in each sample. Machine learning classifiers were used to identify PFASs that were diagnostic of each source type. Four C5-C7 perfluoroalkyl acids and one suspect PFAS (trihydrogen-substituted fluoroethernonanoic acid) were diagnostic of AFFF-GW. Two target PFASs (5:3 and 6:2 fluorotelomer carboxylic acids) and two suspect PFASs (4:2 fluorotelomer-thia-acetic acid and N-methylperfluoropropane sulfonamido acetic acid) were diagnostic of landfill leachate. Biosolids leachates were best classified along with landfill leachates and N-methyl and N-ethyl perfluorooctane sulfonamido acetic acid assisted in that classification. WWTP, pulp and paper, and power generation samples contained few target PFASs, but fipronil (a fluorinated insecticide) was diagnostic of WWTP samples. Our results provide PFAS fingerprints for known sources and identify target and suspect PFASs that can be used for source allocation.

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.

Role of Mineral-Organic Interactions in PFAS Retention by AFFF-Impacted Soil

A comprehensive, generalized approach to predict the retention of per- and polyfluoroalkyl substances (PFAS) from aqueous film-forming foam (AFFF) by a soil matrix as a function of PFAS molecular and soil physiochemical properties was developed. An AFFF with 34 major PFAS (12 anions and 22 zwitterions) was added to uncontaminated soil in one-dimensional saturated column experiments and PFAS mass retained was measured. PFAS mass retention was described using an exhaustive statistical approach to generate a poly-parameter quantitative structure-property relationship (ppQSPR). The relevant predictive properties were PFAS molar mass, mass fluorine, number of nitrogens in the PFAS molecule, poorly crystalline Fe oxides, organic carbon, and specific (BET-N2) surface area. The retention of anionic PFAS was nearly independent of soil properties and largely a function of molecular hydrophobicity, with the size of the fluorinated side chain as the main predictor. Retention of nitrogen-containing zwitterionic PFAS was related to poorly crystalline metal oxides and organic carbon content. Knowledge of the extent to which a suite of PFAS may respond to variations in soil matrix properties, as developed here, paves the way for the development of reactive transport algorithms with the ability to capture PFAS dynamics in source zones over extended time frames.

Evaluating Neutral PFAS for Potential Dermal Absorption from the Gas Phase

Exposures to per- and polyfluoroalkyl substances (PFAS) are of increasing concern. Assessments typically focus only on ingestion and inhalation exposure due to a lack of generally accepted approaches for estimating dermal absorption. Prior work indicates limited dermal absorption of ionic PFAS, but absorption of neutral PFAS has not been examined from the liquid vehicle or from vapor. Partitioning of semivolatile organic compounds from the gas phase to the skin surface (i.e., stratum corneum) is well known, but the potential for partitioning of neutral PFAS from the gas phase to the stratum corneum has yet to be estimated. The SPARC-estimated physicochemical properties were used to calculate transdermal permeability coefficients (k_{p_g}) and dermal-to-inhalation (D/I) exposure ratios for two groups of neutral PFAS, including those on a U.S. Environmental Protection Agency PFAS list. 11 neutral PFAS gave calculated D/I ratios >5, indicating that direct transdermal absorption may be an important exposure pathway compared to inhalation. Data on consumer products or indoor air is needed for the 11 neutral PFAS, followed by possible biomonitoring to experimentally verify dermal absorption from air. Additional PFAS should be estimated by the protocol used here as they are identified in commercial products.

Paints: A Source of Volatile PFAS in Air─Potential Implications for Inhalation Exposure

Paints are widely used in indoor settings yet there are no data for volatile per- and polyfluoroalkyl substances (PFAS) for paints or knowledge if paints are potentially important sources of human exposure to PFAS. Different commercial paints (n = 27) were collected from local hardware stores and analyzed for volatile PFAS by gas chromatography-mass spectrometry (GC-MS), nonvolatile PFAS by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qTOF), and total fluorine by ¹⁹F nuclear magnetic resonance spectroscopy (NMR). Diluted paint required clean up to remove 6:2 fluorotelomer phosphate diester (diPAP), which thermally transforms into 6:2 FTOH at 280 °C (GC inlet temperature). Only 6:2 FTOH (0.9-83 μg/g) and 6:2 diPAP (0.073-58 μg/g) were found in five exterior and nine interior paints and only accounted for a maximum of 17% of total fluorine. Upon drying, 40% of the FTOH mass was lost, and the loss was verified by measurements of the cumulative FTOH mass measured in the air of a small, confined space over a 3 h period. Based on the liquid paint results, the ConsExpo model was used for potential exposure assessment and one commercial paint exceeded the chosen reference dose (5 μg/kg-day) for children and adults, indicating the potential for human exposure during painting.

Tools for Understanding and Predicting the Affinity of Per- and Polyfluoroalkyl Substances for Anion-Exchange Sorbents

Anion-exchange (AE) sorbents are gaining in popularity for the remediation of anionic per- and polyfluoroalkyl substances (PFAS) in water. However, it is unclear how hydrophobic and electrostatic interactions contribute to anionic PFAS retention. The goal of this study was to understand the effects of PFAS chain length and head group on electrostatic interactions between PFAS and an aminopropyl AE phase. Liquid chromatography-mass spectrometry (LC-MS) was used with an aminopropyl AE guard column to find relative retention times. The average electrostatic potential (EP_avg) of each PFAS was calculated, which correlated positively with the PFAS chromatographic retention time, demonstrating the value of EP_avg as a proxy for predicting electrostatic interactions between PFAS and the aminopropyl AE phase. The order of greatest to lowest PFAS AE affinity for an aminopropyl column based on chromatographic retention times and electrostatic interactions was n:3 fluorotelomer carboxylic acids (n:3 FtAs) > n:2 fluorotelomer carboxylic acids (n:2 FtAs) > perfluoroalkyl carboxylates (PFCAs) > perfluoroalkyl sulfonamides (FASAs) ∼ n:2 fluorotelomer sulfonates (n:2 FtSs) > perfluoroalkyl sulfonates (PFSAs). This study introduces a methodology for qualitatively characterizing electrostatic interactions between PFAS and AE phases and highlights that electrostatic interactions alone cannot explain the affinity of PFAS for AE resins in water treatment/remediation scenarios.

Enrichment of poly- and perfluoroalkyl substances (PFAS) in the surface microlayer and foam in synthetic and natural waters

Bench-scale experiments were performed to interrogate poly- and perfluoroalkyl substance (PFAS) enrichment in the water surface microlayer (SML). In initial experiments using electrolyte-only solutions, the perfluorooctane sulfonate (PFOS) and perfluorooctane carboxylate (PFOA) enrichment in the SML were reasonably (with a factor of 2) described by the Gibbs adsorption equation coupled with a Freundlich-based interfacial adsorption model. Enrichment in the SML among perfluorinated sulfonates and perfluorinated carboxylates of varying chain lengths was proportional to their surface activity. The PFOS enrichment factor (EF), defined as the PFAS concentration in the SML divided by the concentration in the bulk water, was 18 in a 200 mg/l NaCl solution. The presence of elevated organic carbon levels in synthetic surface waters inhibited PFAS accumulation in the SML, with resulting EF values of approximately 1 for all PFAS. However, in the presence of elevated organic levels coupled with foam, PFAS enrichment in the foam was observed, with a foam EF of 25 measured for PFOS in synthetic surface waters. PFAS EF values measured in several natural surface waters without foam showed little variation among the waters tested, with PFOS EF values ranging between 6 and 10. Together, these results suggest that PFAS accumulation in the SML is largely controlled by PFAS sorption at the air-water interface for the conditions examined in this study, and the presence of foam with natural organics enhances PFAS uptake at the water surface.

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

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

Biotransformation of 6:2 Fluorotelomer Thioether Amido Sulfonate in Aqueous Film-Forming Foams under Nitrate-Reducing Conditions

Despite the prevalence of nitrate reduction in groundwater, the biotransformation of per- and polyfluoroalkyl substances (PFAS) under nitrate-reducing conditions remains mostly unknown compared with aerobic or strong reducing conditions. We constructed microcosms under nitrate-reducing conditions to simulate the biotransformation occurring at groundwater sites impacted by aqueous film-forming foams (AFFFs). We investigated the biotransformation of 6:2 fluorotelomer thioether amido sulfonate (6:2 FtTAoS), a principal PFAS constituent of several AFFF formulations using both quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) and qualitative high-resolution mass spectrometry analyses. Our results reveal that the biotransformation rates of 6:2 FtTAoS under nitrate-reducing conditions were about 10 times slower than under aerobic conditions, but about 2.7 times faster than under sulfate-reducing conditions. Although minimal production of 6:2 fluorotelomer sulfonate and the terminal perfluoroalkyl carboxylate, perfluorohexanoate was observed, fluorotelomer thioether and sulfinyl compounds were identified in the aqueous samples. Evidence for the formation of volatile PFAS was obtained by mass balance analysis using the total oxidizable precursor assay and detection of 6:2 fluorotelomer thiol by gas chromatography-mass spectrometry. Our results underscore the complexity of PFAS biotransformation and the interactions between redox conditions and microbial biotransformation activities, contributing to the better elucidation of PFAS environmental fate and impact.

Neutral Per- and Polyfluoroalkyl Substances, Butyl Carbitol, and Organic Corrosion Inhibitors in Aqueous Film-Forming Foams: Implications for Vapor Intrusion and the Environment

Per- and polyfluoroalkyl substances (PFAS), butyl carbitol, and corrosion inhibitors are components of aqueous film-forming foams (AFFFs). Volatile (neutral) fluorotelomerization (FT)- and electrochemical fluorination (ECF)-based PFAS, butyl carbitol, and organic corrosion inhibitors were quantified in 39 military specification (MilSpec), non-MilSpec, and alcohol resistant-AFFF concentrates (undiluted) from 1974 to 2010. Fluorotelomer alcohols were found only in FT-based AFFFs and N-methyl- and N-ethyl-perfluoroalkyl sulfonamides, and sulfonamido ethanols were found only in ECF-based AFFFs. Neutral PFAS and benzotriazole, 4-methylbenzotriazole, and 5-methybenzotriazole occurred at mg/L levels in the AFFFs, while butyl carbitol occurred at g/L levels. Neutral PFAS concentrations in indoor air due to vapor intrusion of a nearby undiluted AFFF release are estimated to be anywhere from 2 to >10 orders of magnitude higher than documented background indoor air concentrations. Estimated butyl carbitol and organic corrosion inhibitor concentrations were lower than and comparable to indoor concentrations recently measured, respectively. The wide range of neutral PFAS concentrations and Henry's law constants indicate that field, soil-gas measurements are needed to validate the estimations. Co-discharged butyl carbitol likely contributes to oxygen depletion in AFFF-impacted aquifers and may hinder the natural PFAS aerobic biotransformation. Organic corrosion inhibitors in AFFFs indicate that these are another source of corrosion inhibitors in the environment.

Dietary Perfluorohexanoic Acid (PFHxA) Exposures in Juvenile Zebrafish Produce Subtle Behavioral Effects across Generations

Ubiquitous anthropogenic contaminants of concern, per- and polyfluoroalkyl substances (PFAS) are frequently detected in the environment and human populations around the world. Diet is a predominate route of human exposure, and PFAS are frequently measured in food. Manufacturing trends have shifted from legacy PFAS to shorter-chain alternatives that are suggested to be safer, such as perfluorohexanoic acid (PFHxA). However, the current amount of data to support safety assessments of these alternatives is not yet sufficient. The present study investigated the effects of a 42-day dietary exposure to 1, 10, or 100 ng/g PFHxA in juvenile zebrafish. The zebrafish model was leveraged to interrogate morphometrics, fecundity, and numerous behavior endpoints across multiple generations. Dietary PFHxA exposure did not result in measurable body burden and did not affect growth, fecundity, adult social perception behavior, or associative learning. PFHxA exposure did induce abnormal adult anxiety behaviors in the F0 generation that persisted transgenerationally in the F1 and F2. Abnormal larval and juvenile behavior was observed in the F1 generation, but not in the F2. PFHxA juvenile dietary exposure induced subtle and multigenerational behavior effects that warrant further investigation of this and other alternative short-chain PFAS.

Communicating Confidence of Per- and Polyfluoroalkyl Substance Identification via High-Resolution Mass Spectrometry

Per- and polyfluoroalkyl substances (PFASs) are important environmental contaminants, yet relatively few analytical reference standards exist for this class. Nontarget analyses performed by means of high-resolution mass spectrometry (HRMS) are increasingly common for the discovery and identification of PFASs in environmental and biological samples. The certainty of PFAS identifications made via HRMS must be communicated through a reliable and harmonized approach. Here, we present a confidence scale along with identification criteria specific to suspect or nontarget analysis of PFASs by means of nontarget HRMS. Confidence levels range from level 1a-"Confirmed by Reference Standard," and level 1b-"Indistinguishable from Reference Standard," to level 5-"Exact Masses of Interest," which are identified by suspect screening or data filtering, two common forms of feature prioritization. This confidence scale is consistent with general criteria for communicating confidence in the identification of small organic molecules by HRMS (e.g., through a match to analytical reference standards, library MS/MS, and/or retention times) but incorporates the specific conventions and tools used in PFAS classification and analysis (e.g., detection of homologous series and specific ranges of mass defects). Our scale clarifies the level of certainty in PFAS identification and, in doing so, facilitates more efficient identification.

Systematic developmental toxicity assessment of a structurally diverse library of PFAS in zebrafish

Per- and polyfluoroalkyl substances (PFAS) are a class of widely used chemicals with limited human health effects data relative to the diversity of structures manufactured. To help fill this data gap, an extensive in vivo developmental toxicity screen was performed on 139 PFAS provided by the US EPA. Dechorionated embryonic zebrafish were exposed to 10 nominal water concentrations of PFAS (0.015-100 µM) from 6 to 120 h post-fertilization (hpf). The embryos were assayed for embryonic photomotor response (EPR), larval photomotor response (LPR), and 13 morphological endpoints. A total of 49 PFAS (35%) were bioactive in one or more assays (11 altered EPR, 25 altered LPR, and 31 altered morphology). Perfluorooctanesulfonamide (FOSA) was the only structure that was bioactive in all 3 assays, while Perfluorodecanoic acid (PFDA) was the most potent teratogen. Low PFAS volatility was associated with developmental toxicity (p < 0.01), but no association was detected between bioactivity and five other physicochemical parameters. The bioactive PFAS were enriched for 6 supergroup chemotypes. The results illustrate the power of a multi-dimensional in vivo platform to assess the developmental (neuro)toxicity of diverse PFAS and in the acceleration of PFAS safety research.

Per- and Polyfluoroalkyl Substances (PFAS) in Facemasks: Potential Source of Human Exposure to PFAS with Implications for Disposal to Landfills

Facemasks are important tools for fighting against disease spread, including Covid-19 and its variants, and some may be treated with per- and polyfluoroalkyl substances (PFAS). Nine facemasks over a range of prices were analyzed for total fluorine and PFAS. The PFAS compositions of the masks were then used to estimate exposure and the mass of PFAS discharged to landfill leachate. Fluorine from PFAS accounted only for a small fraction of total fluorine. Homologous series of linear perfluoroalkyl carboxylates and the 6:2 fluorotelomer alcohol indicated a fluorotelomer origin. Inhalation was estimated to be the dominant exposure route (40%-50%), followed by incidental ingestion (15%-40%) and dermal (11%-20%). Exposure and risk estimates were higher for children than adults, and high physical activity substantially increased inhalation exposure. These preliminary findings indicate that wearing masks treated with high levels of PFAS for extended periods of time can be a notable source of exposure and have the potential to pose a health risk. Despite modeled annual disposal of ~29-91 billion masks, and an assuming 100% leaching of individual PFAS into landfill leachate, mask disposal would contribute only an additional 6% of annual PFAS mass loads and less than 11 kg of PFAS discharged to U.S. wastewater.

Sulfonamide functional head on short-chain perfluorinated substance drives developmental toxicity

Per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in environmental and biological samples and cause adverse health effects. Studies have predominately focused on long-chain PFAS, with far fewer addressing short-chain alternatives. This study leveraged embryonic zebrafish to investigate developmental toxicity of a short-chain series: perfluorobutane sulfonate (PFBS), perfluoropentanoic acid (PFPeA), perfluorobutane sulfonamide (FBSA), and 4:2 fluorotelomer sulfonic acid (4:2 FTS). Following static exposures at 8 h postfertilization (hpf) to each chemical (1-100 μM), morphological and behavioral endpoints were assessed at 24 and 120 hpf. Only FBSA induced abnormal morphology, while exposure to all chemicals caused aberrant larval behavior. RNA sequencing at 48 hpf following 47 μM exposures revealed only FBSA significantly disrupted normal gene expression. Measured tissue concentrations were FBSA > PFBS > 4:2 FTS > PFPeA. This study demonstrates functional head groups impact bioactivity and bioconcentration.

Mass-Labeled Fluorotelomer Alcohol Fragmentation Gives "False Positive" for Nonlabeled Fluorotelomer Alcohols with Implications for Consumer Product Analysis

Volatile per- and polyfluoroalkyl substances (PFAS) are detected in various consumer goods, raising concerns over environmental fate and human exposure. Volatile PFAS are commonly analyzed by gas chromatography-chemical ionization-mass spectrometry. Mass-labeled standards are used for quantitative analysis of volatile PFAS and to ensure quality control. However, mass-labeled fluorotelomer alcohol (FTOH) analyzed in positive chemical ionization produces signals corresponding to nonlabeled (native) FTOH ions, resulting in false positives. This observation was attributed to deuterium or hydrogen abstraction of mass-labeled standards. Deuterium abstraction of deuterated standards, including d₄-4:2 FTOH, ¹³C₂-d₂-6:2 FTOH, ¹³C₂-d₂-10:2 FTOH, and hydrogen abstraction of ¹³C-labeled standard ¹³C₂-8:2 FTOH are ionization artifacts that yielded responses for native FTOH m/z values. False positives for native (nonlabeled) FTOHs caused by the introduction of a mass-labeled surrogate can be controlled by blank subtracting or decreasing mass-labeled standard concentrations. Alternatively, different mass-labeled standards can also be used in sample analysis.

Disposition of Fluorine on New Firefighter Turnout Gear

Firefighter turnout gear is essential for reducing occupational exposure to hazardous chemicals during training and fire events. Per-and polyfluoroalkyl substances (PFASs) are observed in firefighter serum, and possible occupational sources include the air and dust of fires, aqueous film-forming foam, and turnout gear. Limited data exist for nonvolatile and volatile PFASs on firefighter turnout gear and the disposition of fluorine on the individual layers of turnout gear. Further implications for exposure to fluorine on turnout gear are not well understood. Three unused turnout garments purchased in 2019 and one purchased in 2008, were analyzed for 50 nonvolatile and 15 volatile PFASs by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS) and gas chromatography-mass spectrometry (GC-MS), respectively. Particle-induced gamma ray emission (PIGE), a surface technique, and instrumental neutron activation analysis (INAA), a bulk technique, were used to measure total fluorine. Bulk characterization of the layers by pyrolysis-GC/MS (py-GC/MS) was used to differentiate fluoropolymer (e.g., PTFE) films from textile layers finished with side-chain polymers. The outer layer, moisture barrier, and thermal layers of the turnout gear all yielded measured concentrations of volatile PFASs that exceeded nonvolatile PFAS concentrations, but the summed molar concentrations made up only a small fraction of total fluorine (0.0016-6.7%). Moisture barrier layers comprised a PTFE film, as determined by py-GC-MS, and gave the highest individual nonvolatile (0.159 mg F/kg) and volatile PFAS (20.7 mg F/kg) as well as total fluorine (122,000 mg F/kg) concentrations. Outer and thermal layers comprised aromatic polyamide-based fibers (aramid) treated with side-chain fluoropolymers and had lower levels of individual nonvolatile and volatile PFASs. Equal concentrations of total fluorine by both PIGE and INAA on the outer and thermal layers is consistent with treatment with a side-chain fluoropolymer coating. New turnout gear should be examined as a potential source of firefighter occupational exposure to nonvolatile and volatile PFASs in future assessments.

Chronic Reproductive Toxicity Thresholds for Northern Bobwhite Quail (Colinus virginianus) Exposed to Perfluorohexanoic Acid (PFHxA) and a Mixture of Perfluorooctane Sulfonic Acid (PFOS) and PFHxA

Terrestrial toxicology data are limited for comprehensive ecotoxicological risk assessment of ecosystems contaminated by per- and polyfluoroalkyl substances (PFAS) partly because of their existence as mixtures in the environment. This complicates logistical dose-response modeling and establishment of a threshold value characterizing the chronic toxicity of PFAS to ecological receptors. We examined reproduction, growth, and survival endpoints using a combination of hypothesis testing and logistical dose-response modeling of northern bobwhite quail (Colinus virginianus) exposed to perfluorohexanoic acid (PFHxA) alone and to PFHxA in a binary mixture with perfluorooctane sulfonic acid (PFOS) via the drinking water. The exposure concentration chronic toxicity value (CTV) representative of the lowest-observable-adverse effect level (LOAEL) threshold for chronic oral PFAS toxicity (based on reduced offspring weight and growth rate) was 0.10 ng/mL for PFHxA and 0.06 ng/mL for a PFOS:PFHxA (2.7:1) mixture. These estimates corresponded to an adult LOAEL average daily intake CTV of 0.0149 and 0.0082 µg × kg body weight^-1  × d^-1 , respectively. Neither no-observable-adverse effect level threshold and representative CTVs nor dose-response and predicted effective concentration values could be established for these 2 response variables. The findings indicate that a reaction(s) occurs among the individual PFAS components present in the mixture to alter the potential toxicity, demonstrating that mixture affects avian PFAS toxicity. Thus, chronic oral PFAS toxicity to avian receptors represented as the sum of the individual compound toxicities may not necessarily be the best method for assessing chronic mixture exposure risk at PFAS-contaminated sites. Environ Toxicol Chem 2021;40:2601-2614. © 2021 SETAC.

Toxicological Response of Chironomus dilutus in Single-Chemical and Binary Mixture Exposure Experiments with 6 Perfluoralkyl Substances

Few studies have determined the toxicity of perfluoralkyl substances (PFAS) to aquatic invertebrates. We exposed Chironomus dilutus to 6 different PFAS to assess single-chemical toxicity and relative or proportional toxicity among substances. A 10-d range-finding test was conducted to inform 20-d assays for the following PFAS: perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluoroheptanoic acid (PFHpA). A 20-d binary mixture study of PFOS+PFHxS followed the single-chemical tests. Measurement endpoints for 20-d tests included larval survival and biomass. Log-logistic concentration response models were used to estimate 10, 20, and 50% effect concentrations (EC20, EC50) for PFOS, PFHxS, and PFOA. Survival EC50s for PFOS, PFHxS, and PFOA were 2.49, 3860, and 192 000 µg/L, respectively, whereas survival EC20s were 1.70, 913, and 119 000 µg/L for PFOS, PFHxS, and PFOA, respectively. Biomass as a combined survival and growth endpoint resulted in EC20s of 1.89, 896, and 137 000 µg/L for PFOS, PFHxS, and PFOA, respectively. Maximum concentrations tested (no-observed-effect concentrations) for PFNA, PFBS, and PFHpA were 2 to 3 orders of magnitude greater than the PFOS EC50s and showed no toxicity to C. dilutus, even at exposure concentrations well above what would be considered environmentally relevant. The binary mixture of 2.5 µg/L PFOS+1000 µg/L PFHxS showed reduced survival compared to controls and some indication of potential additive or synergistic interaction between PFOS and PFHxS. Overall, the present study supports previous studies showing PFOS to be the most toxic PFAS to aquatic life and suggests that PFOS could be more toxic to the freshwater midge than previously reported. Environ Toxicol Chem 2021;40:2319-2333. © 2021 SETAC.

Environmental Source Tracking of Per- and Polyfluoroalkyl Substances within a Forensic Context: Current and Future Techniques

The source tracking of per- and polyfluoroalkyl substances (PFASs) is a new and increasingly necessary subfield within environmental forensics. We define PFAS source tracking as the accurate characterization and differentiation of multiple sources contributing to PFAS contamination in the environment. PFAS source tracking should employ analytical measurements, multivariate analyses, and an understanding of PFAS fate and transport within the framework of a conceptual site model. Converging lines of evidence used to differentiate PFAS sources include: identification of PFASs strongly associated with unique sources; the ratios of PFAS homologues, classes, and isomers at a contaminated site; and a site's hydrogeochemical conditions. As the field of PFAS source tracking progresses, the development of new PFAS analytical standards and the wider availability of high-resolution mass spectral data will enhance currently available analytical capabilities. In addition, multivariate computational tools, including unsupervised (i.e., exploratory) and supervised (i.e., predictive) machine learning techniques, may lead to novel insights that define a targeted list of PFASs that will be useful for environmental PFAS source tracking. In this Perspective, we identify the current tools available and principal developments necessary to enable greater confidence in environmental source tracking to identify and apportion PFAS sources.

Behavior Effects of Structurally Diverse Per- and Polyfluoroalkyl Substances in Zebrafish

Per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in the environment, and some pose significant human and environmental health concerns globally. While some PFAS induce adverse health effects, relatively few toxicological studies adequately address the broad structural diversity of this chemical class. In the current study, we evaluated 58 individual PFAS spanning 14 structural subclasses and 2 mixtures at single concentrations for developmental toxicity in zebrafish using highly sensitive behavior endpoints. Following developmental exposure to PFAS, zebrafish were assessed for mortality and challenged with an embryonic photomotor response (EPR) assay at 24 h postfertilization (hpf) and with larval photomotor response (LPR) and larval startle response assays at 120 hpf. We found that none of the tested PFAS exposures elicited significant mortality or aberrant EPR; however, exposure to 21 individual PFAS from multiple structural subclasses and 1 mixture induced aberrant larval behavior. We then evaluated developmental toxicity across a concentration range of 0-100 μM for 10 perfluoroalkyl carboxylic acids (PFCAs; 4-carbon perfluorobutanoic acid through the 13-carbon perfluorotridecanoic acid). Exposure to the PFCAs did not cause significant mortality or morphological effects, with the exception of perfluorooctanoic acid and perfluorononanoic acid, and did not induce aberrant EPR. All PFCAs, except for longer-chain perfluorododecanoic acid caused abnormal LPR following exposure to at least one concentration. In this study, we evaluated a broad set of PFAS not previously assessed for in vivo sublethal behavior endpoints and confirmed previous findings that exposure to some PFAS induces abnormal behavior in developing zebrafish. The data from this study will guide the selection of PFAS for which to investigate modes of toxic action.

Key Considerations for Accurate Exposures in Ecotoxicological Assessments of Perfluorinated Carboxylates and Sulfonates

Toxicity reference values for per- and polyfluoroalkyl substances (PFAS) vary even when the same test organism is studied. Although the need to confirm dosing solution concentrations is widely accepted, there are no experimental data to inform best practices when PFAS solutions are prepared. Laboratory data indicate that dissolution time of PFAS solids causes statistically significant deviations between nominal and measured concentrations. Mixing times for select PFAS varied between 2 and 5 h, depending on carbon fluorine chain-length. Environ Toxicol Chem 2021;40:677-688. © 2020 SETAC.

Spatial Trends of Anionic, Zwitterionic, and Cationic PFASs at an AFFF-Impacted Site

Soil and groundwater from an aqueous film-forming foam (AFFF)-impacted site were sampled at high resolution (n = 105 for soil, n = 58 for groundwater) and analyzed for an extensive list of anionic, zwitterionic, and cationic poly- and perfluoroalkyl substances (PFASs). Spatial trends for perfluoroalkyl acids and many precursors enabled a better understanding of PFAS composition, transport, and transformation. All PFASs without analytical standards were semi-quantified. Summed PFAS and individual PFAS concentrations were often higher at depth than near the surface in soil and groundwater. Zwitterionic and cationic compounds composed a majority of the total PFAS mass (up to 97%) in firefighter training area (FTA) soil. Composition of PFAS class, chain length, and structural isomers changed with depth and distance from the FTA, suggesting in situ transformation and differential transport. The percentage of branched perfluorooctane sulfonate increased with depth, consistent with differential isomeric transport. However, linear perfluorooctanoic acid (PFOA) was enriched, suggesting fluorotelomer precursor transformation to linear PFOA. Perfluorohexane sulfonamide, a potential transformation product of sulfonamide-based PFASs, was present at high concentrations (maximum 448 ng/g in soil, 3.4 mg/L in groundwater). Precursor compounds may create long-term sources of perfluoroalkyl acids, although many pathways remain unknown; precursor analysis is critical for PFAS fate and transport understanding.

PFAS and Dissolved Organic Carbon Enrichment in Surface Water Foams on a Northern U.S. Freshwater Lake

Information is needed on the concentration of per- and polyfluoroalkyl substances (PFAS) in foams on surface waters impacted by aqueous film-forming foam (AFFF). Nine pairs of foam and underlying bulk water were collected from a single freshwater lake impacted by PFAS and analyzed for PFAS by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF) and for dissolved organic carbon (DOC). The DOC of two foam:bulk water pairs was characterized by ¹H NMR. Foams were comprised of 16 PFAS with concentrations as high as 97 000 ng/L (PFOS) along with longer-chain, more hydrophobic PFAS. Only five PFAS (PFOS and shorter chain lengths) were quantified in underlying bulk waters. Enrichment factors (foam:bulk water) ranged from 10 (PFHxA) up to 2830 (PFOS). Foams impacted by AFFF gave the greatest concentrations and number of PFAS classes with PFOS concentrations exceeding the EPA health advisory level (70 ng/L). PFAS concentrations were significantly below published critical micelle concentrations and constituted <0.1% of overall DOC concentrations in foam, indicating that PFAS are a minor fraction of DOC and that DOC likely plays a central role in foam formation. Estimates indicate that foam ingestion is a potentially important route of exposure for children and adults when they are in surface waters where foam is present.

Chronic Reproductive Toxicity of Perfluorooctane Sulfonic Acid and a Simple Mixture of Perfluorooctane Sulfonic Acid and Perfluorohexane Sulfonic Acid to Northern Bobwhite Quail (Colinus virginianus)

Per- and poly-fluoroalkyl substances (PFAS) are a broad class of environmentally persistent chemicals that include thousands of potentially toxic synthetic organic molecules. Some PFAS have been shown to cause adverse health effects including decreased total cholesterol, birth weight, and reproductive success in laboratory animals; however, a lack of chronic toxicity data exists for PFAS in avian ecological receptors. The present study reports on the chronic toxicity of perfluorooctane sulfonic acid (PFOS) and a mixture of PFOS and perfluorohexane sulfonic acid (PFHxS) to northern bobwhite quail (Colinus virginianus) via oral exposure from drinking water. Female weight gain was adversely affected at an average daily intake (ADI) of 3.10 × 10^-3  ± 0.15 × 10^-3  mg PFOS:PFHxS (1.2:1) mixture × kg^-1 body weight × d^-1 . Successful liberation from the shell once pipped was adversely affected at an ADI of 2.45 × 10^-3  ± 0.01 × 10^-3  mg PFOS x kg^-1 body weight × d^-1 . These values are comparatively much lower than the current dietary avian toxicity reference value (TRV) derived from birds that were exposed via feed, suggesting the need for updated avian TRVs. Relationships between test chemical (PFOS) and test substance (PFOS:PFHxS) showed that PFOS and PFHxS have possible interacting effects in avian receptors and likely differing mechanisms of toxicity depending on chemical co-occurrence and dose. Both the single-chemical and mixture exposures produced similar and possibly additive toxicity values. Environ Toxicol Chem 2020;39:1101-1111. © 2020 SETAC.

Suspect Screening of Hydrocarbon Surfactants in AFFFs and AFFF-Contaminated Groundwater by High-Resolution Mass Spectrometry

Aqueous film-forming foams (AFFFs) are proprietary mixtures containing hydrocarbon surfactants and per- and polyfluoroalkyl substances (PFASs) that are used to extinguish hydrocarbon-based fuel fires. There is limited information on hydrocarbon surfactants in AFFFs and AFFF-contaminated groundwater even though hydrocarbon surfactants are more abundant (5-10% w/w) than PFASs (0.9-1.5% w/w) in AFFFs. Eight commercial AFFFs manufactured between 1988 and 2012 and 10 AFFF-contaminated groundwaters collected from near source zones of fire-fighter training areas were analyzed for suspect hydrocarbon surfactants by liquid chromatography quadrupole time-of-flight mass spectrometry. A suspect list and a homologous series detection computational tool, enviMass, were combined to screen for hydrocarbon surfactants. Nine classes of hydrocarbon surfactants were detected in AFFFs including octylphenol polyethoxylates, linear alcohol ethoxylates, ethoxylated cocoamines, alkyl ether sulfates, alkyl amido dipropionates, linear alkyl benzenesulfonates, alkyl sulfates, and polyethylene glycols. Of those, six were also found in groundwater along with diethanolamines and alkyl amido betaines, which were not found in the eight archived AFFFs. This indicates that although aerobically biodegradable, hydrocarbon surfactants likely persist in groundwater due to anaerobic aquifer conditions. To the best of our knowledge, this is the first screening for hydrocarbon surfactants in AFFFs and in AFFF-contaminated groundwater.

In-Vial Extraction Large Volume Gas Chromatography Mass Spectrometry for Analysis of Volatile PFASs on Papers and Textiles

Volatile per- and polyfluorinated alkyl substances (PFASs) are found in consumer goods that contribute to human exposure to PFASs. Volatile PFAS precursors transform to perfluorinated carboxylates (PFCAs) and sulfonates (PFSAs) in both humans and the environment. Established methods for volatile PFASs in consumer goods exist, but higher sample throughput and greener sample preparation methods are needed to minimize analyte loss, while maintaining sensitivity. New analytical methodology was developed where a 1.5 × 1.5 cm piece of paper or textile is placed into an autosampler vial with solvent and mass-labeled internal standards, sonicated for 30 min, and directly injected without removal of material from the autosampler vial. Large volume injection (20 μL) gas chromatography mass spectrometry was applied for the quantification for 21 individual PFASs from five classes: fluorotelomer alcohols (FTOHs), fluorinated sulfonamides (N-MeFASA, N-EtFASA), and fluorinated sulfonamidoethanols (N-MeFASE, N-EtFASE). Nontargeted analysis revealed additional C₂-C₇ homologues of N-MeFASE and N-EtFASE, which accounted for 14-18% of the total volatile PFASs on three textiles. Overlooking short-chain (≤C₇) N-MeFASE, N-EtFASE, and long-chained (10:2-14:2) FTOHs on older textiles from the 1980s leads to an underestimation of human and environmental exposure to volatile PFAS.

Biodegradation of Crude Oil and Corexit 9500 in Arctic Seawater

The need to understand the biodegradation of oil and chemical dispersants in Arctic marine environments is increasing alongside growth in oil exploration and transport in the region. We chemically quantified biodegradation and abiotic losses of crude oil and Corexit 9500, when present separately, in incubations of Arctic seawater and identified microorganisms potentially involved in biodegradation of these substrates based on shifts in bacterial community structure (16S rRNA genes) and abundance of biodegradation genes (GeoChip 5.0 microarray). Incubations were performed over 28-day time courses using surface seawater collected from near-shore and offshore locations in the Chukchi Sea. Within 28 days, the indigenous microbial community biodegraded 36% (k = 0.010 day^-1) and 41% (k = 0.014 day^-1) of oil and biodegraded 77% and 33% (k = 0.015 day^-1) of the Corexit 9500 component dioctyl sodium sulfosuccinate (DOSS) in respective near-shore and offshore incubations. Non-ionic surfactants (Span 80, Tween 80, and Tween 85) present in Corexit 9500 were non-detectable by 28 days due to a combination of abiotic losses and biodegradation. Microorganisms utilized oil and Corexit 9500 as growth substrates during the incubation, with the Corexit 9500 stimulating more extensive growth than oil within 28 days. Taxa known to include oil-degrading bacteria (e.g., Oleispira, Polaribacter, and Colwellia) and some oil biodegradation genes (e.g., alkB, nagG, and pchCF) increased in relative abundance in response to both oil and Corexit 9500. These results increase our understanding of oil and dispersant biodegradation in the Arctic and suggest that some bacteria may be capable of biodegrading both oil and Corexit 9500.

Biotransformation of AFFF Component 6:2 Fluorotelomer Thioether Amido Sulfonate Generates 6:2 Fluorotelomer Thioether Carboxylate under Sulfate-Reducing Conditions

The fate of per and polyfluoroalkyl substances (PFASs) in aqueous filmforming foams (AFFFs) under anaerobic conditions has not been well characterized, leaving major gaps in our understanding of PFAS fate and transformation at contaminated sites. In this study, the biotransformation of 6:2 fluorotelomer thioether amido sulfonate (6:2 FtTAoS), a component of several AFFF formulations, was investigated under sulfate-reducing conditions in microcosms inoculated with either pristine or AFFF-impacted solids. To identify the transformation products, we used high-resolution mass spectrometry and employed suspect-screening and nontargeted compound identification methods. These analyses demonstrated that 6:2 FtTAoS was transformed primarily to a stable polyfluoroalkyl compound, 6:2 fluorotelomer thioether propionate (6:2 FtTP). It did not undergo further reactions to produce the perfluoroalkyl carboxylates and fluorotelomer sulfonates and carboxylates that were observed during aerobic transformations. Here, the 6:2 FtTP was recalcitrant to biotransformation, indicating the stability of the thioether group under sulfate reducing conditions. The total oxidizable precursor (TOP) assay was used to assess the presence of other PFASs. Although nearly all of the PFAS mass initially present was recovered from the pristine microcosms, only 67% of the initial PFAS mass was recovered from the contaminated microcosms, suggesting the formation of volatile biotransformation products or those that could not be detected by the TOP assay.

Sorption of Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and a Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil

During fire-fighter training, equipment testing, and emergency responses with aqueous film-forming foams (AFFFs), milligrams per liter concentrations of anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFASs) enter the environment. Because the behavior of zwitterionic and cationic PFASs in the subsurface is unknown, batch sorption experiments were conducted using National Foam AFFF, which contains anionic fluorotelomer sulfonates (FtSs), zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and cationic 6:2 fluorotelomer sulfonamido amine (FtSaAm). Sorption of the FtSs, FtSaBs, and 6:2 FtSaAm to six soils with varying organic carbon, effective cation-exchange capacity, and anion-exchange capacity was evaluated to determine sorption mechanisms. Due to the poor recovery of the FtSaBs and 6:2 FtSaAm with published PFAS soil extraction methods, a new soil extraction method was developed to achieve good (90-100%) recoveries. The 6:2 FtSaAm was depleted from the aqueous phase in all but one soil, which is attributed to electrostatic and hydrophobic interactions. Sorption of the FtSs was driven by hydrophobic interactions, while the FtSaBs behave more like cations that strongly associate with the solid phase relative to groundwater. Thus, the sorption mechanisms of the FtSs, FtSaBs, and 6:2 FtSaAm are more complex than expected and cannot be predicted by bulk soil properties.

Closing the Mass Balance on Fluorine on Papers and Textiles

Papers and textiles that are treated with per- and polyfluoroalkyl substances (PFASs) are sources of human and environmental exposure. Data for individual PFASs, such as perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA), are not placed into the context of total fluorine for papers and textiles. Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to quantify volatile and ionic PFASs, respectively, and the total oxidizable precursor (TOP) assay was used to quantify precursors that form perfluoroalkyl carboxylates. Molar sums of PFASs obtained by GC-MS, LC-MS/MS, and precursors were compared to total fluorine (nmol F/cm²) determined by particle-induced gamma ray emission (PIGE) spectroscopy, measured before and after extraction. Volatile and ionic PFASs and unknown precursors accounted for 0-2.2%, 0-0.41%, and 0.021-14%, respectively, of the total nmol F/cm² determined by PIGE. After extraction, papers and textiles retained 64 ± 28% to 110 ± 30% of the original nmol F/cm² as determined by PIGE, indicating that the majority of fluorine remains associated with the papers and textiles. The sum of PFASs in the volatile, ionic, and precursor fraction, and total fluorine after extraction indicate that mass balance was achieved (within analytical error) of the initial total fluorine measured by PIGE.

Multianalyte profiling of per- and polyfluoroalkyl substances (PFASs) in liquid commercial products

The chemical properties of poly- and perfluoroalkyl substances (PFASs) make them widespread for use in a number of industrial and commercial products to confer water and oil-repellency characteristics and to reduce surface tension e.g. in aqueous film-forming foams (AFFFs). Some PFASs, especially perfluoroctane sulfonate, and several perfluoroalkyl carboxylic acids, are known to cause significant human and environmental negative impact. Our knowledge on the content of PFASs in products remains scarce due to limited information available, thus impeding any precise assessment of human exposure and environmental release upon use. This study aimed at analyzing a wide variety of liquid products (n = 194) likely to contain PFASs, including impregnating agents, lubricants, cleansers, polishes, AFFFs and other industrial products. By means of LC- and GC-MS/MS analytical techniques, 24 PFASs (from 41 targeted PFASs) were detected and quantified in 55% of samples. PFAS quantification and profiling was found to be consumer product specific. PFASs were mostly detected in AFFF (90%) and impregnating agents (60%) with mainly ionic and neutral species, respectively. In particular, the fluorotelomer alcohols 6:2, 8:2 and 10:2 FTOHs were detected in 40-50% of impregnating agents. Further investigation by Fast Atom Bombardment Mass Spectrometry (FAB-MS) on a set of AFFF samples allowed the characterization of 8 different PFAS classes as major components in these formulations. Results demonstrated that numerous and diversified PFAS are currently used in specific commercial products, implying significant human exposure and environmental release that necessitate further research concerning their toxicological impact.

Discovery of 40 Classes of Per- and Polyfluoroalkyl Substances in Historical Aqueous Film-Forming Foams (AFFFs) and AFFF-Impacted Groundwater

Aqueous film-forming foams (AFFFs), containing per- and polyfluoroalkyl substances (PFASs), are released into the environment during response to fire-related emergencies. Repeated historical applications of AFFF at military sites were a result of fire-fighter training exercises and equipment testing. Recent data on AFFF-impacted groundwater indicates that ∼25% of the PFASs remain unidentified. In an attempt to close the mass balance, a systematic evaluation of 3M and fluorotelomer-based AFFFs, commercial products, and AFFF-impacted groundwaters from 15 U.S. military bases was conducted to identify the remaining PFASs. Liquid chromatography quadrupole time-of-flight mass spectrometry was used for compound discovery. Nontarget analysis utilized Kendrick mass defect plots and a "nontarget" R script. Suspect screening compared masses with those of previously reported PFASs. Forty classes of novel anionic, zwitterionic, and cationic PFASs were discovered, and an additional 17 previously reported classes were observed for the first time in AFFF and/or AFFF-impacted groundwater. All 57 classes received an acronym and IUPAC-like name derived from collective author knowledge. Thirty-four of the 40 newly identified PFAS classes derive from electrochemical fluorination (ECF) processes, most of which have the same base structure. Of the newly discovered PFASs found only in AFFF-impacted groundwater, 11 of the 13 classes are ECF-derived, and the remaining two classes are fluorotelomer-derived, which suggests that both ECF- and fluorotelomer-based PFASs are persistent in the environment.

National Estimate of Per- and Polyfluoroalkyl Substance (PFAS) Release to U.S. Municipal Landfill Leachate

Landfills are the final stage in the life cycle of many products containing per- and polyfluoroalkyl substances (PFASs) and their presence has been reported in landfill leachate. The concentrations of 70 PFASs in 95 samples of leachate were measured in a survey of U.S. landfills of varying climates and waste ages. National release of PFASs was estimated by coupling measured concentrations for the 19 PFASs where more than 50% of samples had quantifiable concentrations, with climate-specific estimates of annual leachate volumes. For 2013, the total volume of leachate generated in the U.S. was estimated to be 61.1 million m³, with 79% of this volume coming from landfills in wet climates (>75 cm/yr precipitation) that contain 47% of U.S. solid waste. The mass of measured PFASs from U.S. landfill leachate to wastewater treatment plants was estimated to be between 563 and 638 kg for 2013. In the majority of landfill leachate samples, 5:3 fluorotelomer carboxylic acid (FTCA) was dominant and variations in concentrations with waste age affected total estimated mass. There were six PFASs that demonstrated significantly higher concentrations in leachate from younger waste compared to older waste and six PFAS demonstrated significant variation with climate.

Using wastewater-based epidemiology to estimate drug consumption-Statistical analyses and data presentation

AIM

Analysis of wastewater samples can be used to assess population drug use, but reporting and statistical issues have limited the utility of the approach for epidemiology due to analytical results that are below the limit of quantification or detection. Unobserved or non-quantifiable-censored-data are common and likely to persist as the methodology is applied to more municipalities and a broader array of substances. We demonstrate the use of censored data techniques and account for measurement errors to explore distributions and annual estimates of the daily mean level of drugs excreted per capita.

MEASUREMENTS

Daily 24-hour composite wastewater samples for 56days in 2009 were obtained using a random sample stratified by day of week and season for 19 municipalities in the Northwest region of the U.S.

METHODS

Methamphetamine, benzoylecgonine (cocaine metabolite), 3,4 methylenedioxymethamphetamine (MDMA), methadone, oxycodone and hydrocodone were identified and quantified in wastewater samples. Four statistical approaches (reporting censoring, Maximum Likelihood Estimation, Kaplan-Meier estimates, or complete data calculations) were used to estimate an annual average, including confidence bounds where appropriate, dependent upon the amount of censoring in the data.

FINDINGS

The proportion of days within a year with censored data varied greatly by drug across the 19 municipalities, with MDMA varying the most (4% to 94% of observations censored). The different statistical approaches each needed to be used given the levels of censoring of measured drug concentrations. Figures incorporating confidence bounds allow visualization of the data that facilitates appropriate comparisons across municipalities.

CONCLUSIONS

Results from wastewater sampling that are below detection or quantification limits contain important information and can be incorporated to create a more complete and valid estimate of drug excretion.

Trace Analysis of Surfactants in Corexit Oil Dispersant Formulations and Seawater

After the April 2010 explosion on the Deepwater Horizon oil rig, and subsequent release of millions of barrels of oil, two Corexit oil dispersant formulations were used in unprecedented quantities both on the surface and sub-surface of the Gulf of Mexico. Although the dispersant formulations contain four classes of surfactants, current studies to date focus on the anionic surfactant, bis-(2-ethylhexyl) sulfosuccinate (DOSS). Factors affecting the integrity of environmental and laboratory samples for Corexit analysis have not been systematically investigated. For this reason, a quantitative analytical method was developed for the detection of all four classes of surfactants, as well as the hydrolysis products of DOSS, the enantiomeric mixture of α- and β-ethylhexyl sulfosuccinate (α-/β-EHSS). The analytical method was then used to evaluate which practices for sample collection, storage, and analysis resulted in high quality data. Large volume, direct injection of seawater followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) minimized analytical artifacts, analysis time, and both chemical and solid waste. Concentrations of DOSS in the seawater samples ranged from 71 - 13,000 ng/L, while the nonionic surfactants including Span 80, Tween 80, Tween 85 were detected infrequently (26% of samples) at concentrations from 840 - 9100 ng/L. The enantiomers α-/β-EHSS were detected in seawater, at concentrations from 200 - 1,900 ng/L, and in both Corexit dispersant formulations, indicating α-/β-EHSS were applied to the oil spill and may be not unambiguous indicator of DOSS degradation. Best practices are provided to ensure sample integrity and data quality for environmental monitoring studies and laboratory that require the detection and quantification of Corexit-based surfactants in seawater.

Release of Per- and Polyfluoroalkyl Substances (PFASs) from Carpet and Clothing in Model Anaerobic Landfill Reactors

Discarded carpet and clothing are potential sources of per- and polyfluoroalkyl substances (PFASs) in landfill leachate, but little is known about their release when disposed in landfills. The concentrations of 70 PFASs in the aqueous phase of anaerobic model landfill reactors filled with carpet or clothing were monitored under biologically active and abiotic conditions. For carpet, total PFAS release was greater in live than abiotic reactors, with an average of 8.5 nmol/L and 0.62 nmol/L after 552 days, respectively. Release in live carpet reactors was primarily due to 5:3 fluorotelomer carboxylic acid (FTCA - 3.9 nmol/L) and perfluorohexanoic carboxylic acid (PFHxA - 2.9 nmol/L). For clothing, release was more dependent on sample heterogeneity than the presence of biological activity, with 0.63, 21.7, 2.6, and 6.3 nmol/L for two live and two abiotic reactors after 519 days, respectively. Release in the clothing reactors was largely due to perfluorooctatonic carboxylic acid (PFOA), with low relative concentrations of measured biotransformation precursors (FTCAs). For carpet and clothing reactors, the majority of PFAS release was not measured until after day 100. Results demonstrate that carpet and clothing are likely sources of PFASs in landfill leachate.

Physical and Biological Release of Poly- and Perfluoroalkyl Substances (PFASs) from Municipal Solid Waste in Anaerobic Model Landfill Reactors

A wide variety of consumer products that are treated with poly- and perfluoroalkyl substances (PFASs) and related formulations are disposed of in landfills. Landfill leachate has significant concentrations of PFASs and acts as secondary point sources to surface water. This study models how PFASs enter leachate using four laboratory-scale anaerobic bioreactors filled with municipal solid waste (MSW) and operated over 273 days. Duplicate reactors were monitored under live and abiotic conditions to evaluate influences attributable to biological activity. The biologically active reactors simulated the methanogenic conditions that develop in all landfills, producing ∼140 mL CH4/dry g refuse. The average total PFAS leaching measured in live reactors (16.7 nmol/kg dry refuse) was greater than the average for abiotic reactors (2.83 nmol/kg dry refuse), indicating biological processes were primarily responsible for leaching. The low-level leaching in the abiotic reactors was primarily due to PFCAs ≤C8 (2.48 nmol/kg dry refuse). Concentrations of known biodegradation intermediates, including methylperfluorobutane sulfonamide acetic acid and the n:2 and n:3 fluorotelomer carboxylates, increased steadily after the onset of methanogenesis, with the 5:3 fluorotelomer carboxylate becoming the single most concentrated PFAS observed in live reactors (9.53 nmol/kg dry refuse).

Aerobic Biotransformation of Fluorotelomer Thioether Amido Sulfonate (Lodyne) in AFFF-Amended Microcosms

The aerobic biotransformation pathways of 4:2, 6:2, and 8:2 fluorotelomer thioether amido sulfonate (FtTAoS) were characterized by determining the fate of the compounds in soil and medium microcosms amended with an aqueous film-forming foam (AFFF) solution. The biotransformation of FtTAoS occurred in live microcosms over approximately 40 days and produced 4:2, 6:2, and 8:2 fluorotelomer sulfonate (FtS), 6:2 fluorotelomer unsaturated carboxylic acid (FtUCA), 5:3 fluorotelomer carboxylic acid (FtCA), and C4 to C8 perfluorinated carboxylic acids (PFCAs). Two biotransformation products corresponding to singly and doubly oxygenated forms of 6:2 FtTAoS were also identified through high resolution mass spectrometry (MS) analysis and liquid chromatography tandem-MS. An oxidative assay was used to indirectly quantify the total concentration of polyfluorinated compounds and check the mass balance. The assay produced near complete mass recovery of FtTAoS after biotransformation, with 10% (mol/mol) of the amended FtTAoS accounted for in FtS, FtCA, and PFCA products. The transformation rates of identified products appear to be slow relative to FtTAoS, indicating that some intermediates may persist in the environment. This study confirms some of the sources of FtS and PFCAs in groundwater and soil at AFFF-impacted sites and suggests that fluorinated intermediates that are not routinely measured during the biotransformation of PFASs may accumulate.