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This review article summarizes the results obtained from the combined efforts of a joint academic and industrial initiative to solve the real-life challenge of determining low levels of peptide-related impurities (typically 0.05–1% of the drug substance) in the presence of the related biologically active peptide at a high concentration. A rational screening strategy for pharmaceutically important peptides has been developed that uses combinations of reversed‑phase ultrahigh-pressure liquid chromatography (UHPLC) columns and mobile phases that exhibit complementary reversed-phase chromatographic selectivity using either UV- or mass spectrometry (MS)-compatible conditions. Numerous stationary and mobile phases were categorized using the chemometric tool of principal component analysis (PCA), employing a novel characterization protocol utilizing specifically designed peptide probes. This was successfully applied to the development of a strategy for the detection of impurities (especially isomers) in peptide drug substances using two-dimensional liquid chromatography coupled with MS detection (2D-LC–MS).

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 (

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

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.

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

Proposed workflow for down-selection of sorbents in synthetic and real stormwaters for optimized heavy metal and PFAS removal.

Terrestrial toxicology data are limited for comprehensive ecotoxicological risk assessment (ERA) of ecosystems contaminated by per- and polyfluoroalkyl substances (PFAS) partly due to 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 (ADI) CTV of 0.0149 and 0.0082 µg x kg bw-1 x d-1 , respectively. Neither no-observable-adverse-effect-level (NOAEL) threshold and representative CTVs nor a dose-response and predicted effective concentration (ECx ) values could be established for these two response variables. The findings indicate that reaction(s) occur among the individual PFAS components present in the mixture to alter the potential toxicity, demonstrating that mixture effects 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. This article is protected by copyright. All rights reserved.

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 functional head group classes, and 2 mixtures, at a single, low concentration 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 hours post fertilization (hpf) and with larval photomotor response (LPR) and larval startle response (LSR) 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 functional head group classes 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 (PFOA) and perfluorononanoic acid (PFNA), and did not induce aberrant EPR. All PFCAs, except for longer-chain perfluorododecanoic acid (PFDoA) induced 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.

This study describes the first reported development of a rapid, generic gradient Ultra-High Performance Liquid Chromatography (UHPLC) methodology with targeted triple quadrupole MS/MS using electrospray positive ionisation to detect and unambiguously confirm the identity of 33 substituted 1, 2-diarylethamine (or diphenidine) derivatives in solid drug samples. The in-house synthesised library included a range of derivatives possessing either electron donating/withdrawing substituents, commonly included in combinatorial libraries, of varying size and lipophilicity on the phenyl ring. These test probes were used to investigate if their order of elution and that of their regioisomers were dependent on the position and type of the substituent on the phenyl ring. In addition, investigations into the retention mechanism of the diphenidines under reverse-phase UHPLC conditions were undertaken. Common adulterants found within seized bulk samples were assessed to prove that the methodology was specific, and the developed UHPLC-MS/MS (t G = 10 min) protocol was applied to confirm the identity of the psychoactive components within four seized bulk samples provided by law enforcement.

Concentrations of per- and polyfluoroalkyl substance (PFAS) remain orders of magnitude greater than health advisory levels in groundwater in “source” zones where military firefighters repeatedly ap...

A simple, rapid and robust protocol for the characterisation of strong cation exchange columns for the analysis of small molecular weight bases is described. A range of ten different phases were characterised, and the resultant selectivity and retention factors analysed using Principal Component Analysis. The score plots for the first and second principal components described 83% of the variability within the dataset. Score plots highlighted the large chromatographic differences observed between the phases, the validity of which was established using a larger range of bases. All the strong cation exchange materials demonstrated a synergistic mixed mode (i.e. ion exchange and hydrophobic) retention mechanism. Principal Component Analysis also highlighted the potential difficulty in locating suitable strong cation exchange “back-up” columns for the analysis of small molecular weight bases in that the characterised columns all displayed very different selectivities. The robustness of the protocol was confirmed by a factorial design experiment.

It is important that sample collection and shipping for monitoring perfluoroalkyl and polyfluoroalkyl substances (PFAS) in groundwater and soil do not contribute to PFAS concentrations in samples. ...

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.

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

Bench-scale experiments were performed to evaluate poly- and perfluoroalkyl substance (PFAS) desorption from vadose zone soils collected at a site historically impacted with aqueous film-fo...

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.

The paper describes a simple and rapid reversed-phase UHPLC method development screening strategy for the purity determination of peptide-based pharmaceuticals. The protocol utilises five disparate column and six volatile or non-volatile mobile phases (i.e., 30 combinations). The method development strategy has been demonstrated to be highly effective in identifying conditions which generate complementary selectivity and good peak shape. Columns with varying degrees of charge (positive and negative), in addition to their differing hydrophobic character, were used in combination with mobile phases within the pH range of 2.3 to 5.1. The novel ion-pair / chaotropic reagent ammonium hexafluorophosphate at pH 2.3 was shown to be an extremely useful mobile phase additive in that it produced excellent complementary separation and good peak shape. Methanesulfonic acid was demonstrated to be a good alternative to the ubiquitously employed trifluoroacetic acid which failed to generate optimum separation for the peptides investigated highlighting the importance of screening disparate mobile phase additives. Both ammonium hexafluorophosphate and methanesulfonic acid were shown not to adversely affect the stability of C18 columns or demonstrated any irreversible adsorption / memory effects. No pH hysteresis effects were demonstrated with any of the stationary phases on mobile phase pH cycling. No major problems have been observed with the novel mobile phase additives ammonium hexafluorophosphate and methanesulfonic acid, however, it is recommended that they be used with caution until long-term routine use has been established.

The US military, municipal fire stations, airports, and the petroleum-processing industry have used aqueous film forming foam (AFFF) to extinguish hydrocarbon-based fires. Repeat uses of AFFF during firefighting activities resulted in per- and polyfluoroalkyl substance (PFAS) contamination of groundwater. Granular activated carbon (GAC) adsorption is a frequently selected technology for remediating water containing organic contaminants, including PFASs. A pilot study conducted over nine months at a military fire-fighting training area employed two GAC vessels in a lead–lag configuration to evaluate PFAS removal. Breakthrough was quantified for branched and/or linear isomers of 15 PFASs identified by liquid chromatography tandem mass spectrometry (LC-MS/MS) including perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, perfluoroalkyl sulfonamides, and fluorotelomer sulfonates. The total oxidizable precursor (TOP) assay was used to provide information on precursors in the influent and to quantify precursor breakthrough. Individual PFASs quantified by LC-MS/MS accounted for 76% of the PFASs in influent as quantified by the TOP assay. The influent PFAS profile was used to infer the nature of the AFFFs used at the site. Breakthrough of shorter-chain PFAS and branched isomers occurred before breakthrough of longer-chain PFAS and linear isomers. For PFAS with equal perfluoroalkyl chain length, adsorbability for different head groups was in the order –COO− < –SO3− < –CH2CH2SO3− < –SO2NH. TOP assay results further showed that precursors of perfluoroalkyl carboxylic acids (PFCAs) broke through GAC in addition to commonly measured PFCAs and perfluoroalkylsulfonic acids. Chromatographic retention times of PFAS obtained from a single analysis of influent groundwater can be used to predict the relative order of breakthrough for other PFASs at the pilot scale on GAC.

Widespread disposal of landfill leachate to municipal sewer infrastructure in the United States calls for an improved understanding of the relative organic-chemical contributions to the wastewater treatment plant (WWTP) waste stream and associated surface-water discharge to receptors in the environment. Landfill leachate, WWTP influent, and WWTP effluent samples were collected from three landfill-WWTP systems and compared with analogous influent and effluent samples from two WWTPs that did not receive leachate. Samples were analyzed for 73 per-/poly-fluoroalkyl substances (PFAS), 109 pharmaceuticals, and 21 hormones and related compounds. PFAS were detected more frequently in leachate (92%) than in influent (55%). Total PFAS concentrations in leachate (93 100 ng L−1) were more than 10 times higher than in influent (6950 ng L−1) and effluent samples (3730 ng L−1). Concentrations of bisphenol A; the nonprescription pharmaceuticals cotinine, lidocaine, nicotine; and the prescription pharmaceuticals amphetamine, carisoprodol, pentoxifylline, and thiabendazole were an order of magnitude higher in landfill leachate than WWTP influent. Leachate load contributions for PFAS (0.78 to 31 g d−1), bisphenol A (0.97 to 8.3 g d−1), and nonprescription (2.0 to 3.1 g d−1) and prescription (0.48 to 2.5 g d−1) pharmaceuticals to WWTP influent were generally low (

Bench-scale experiments were performed to assess uptake of poly- and perfluoroalkyl substances (PFAS), both single compounds and mixtures, at the air-water interface. The focus was on evaluating uptake at field-relevant PFAS concentrations (

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.

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.

The biological impacts of per- and polyfluorinated alkyl substances (PFAS) are linked to their protein interactions. Existing research has largely focused on serum albumin and liver fatty acid binding protein, and binding affinities determined with a variety of methods show high variability. Moreover, few data exist for short-chain PFAS, though their prevalence in the environment is increasing. We used molecular dynamics (MD) to screen PFAS binding to liver and intestinal fatty acid binding proteins (L- and I-FABPs) and peroxisome proliferator activated nuclear receptors (PPAR-α, -δ and -γ) with six perfluoroalkyl carboxylates (PFCAs) and three perfluoroalkyl sulfonates (PFSAs). Equilibrium dissociation constants, KDs, were experimentally determined via equilibrium dialysis (EqD) with liquid chromatography tandem mass spectrometry for protein-PFAS pairs. A comparison was made between KDs derived from EqD, both here and in literature, and other in vitro approaches (e.g., fluorescence) from literature. EqD indicated strong binding between PPAR-δ and perfluorobutanoate (0.044 ± 0.013 µM) and perfluorohexane sulfonate (0.035 ± 0.0020 µM), and between PPAR-α and perfluorohexanoate (0.097 ± 0.070 µM). Unlike binding affinities for L-FABP, which increase with chain length, KDs for PPARs showed little chain length dependence by either MD simulation or EqD. Compared with other in vitro approaches, EqD-based KDs consistently indicated higher affinity across different proteins. This is the first study to report PPARs binding with short-chain PFAS with KDs in the sub-micromolar range.

Bench-scale experiments were performed to measure and evaluate the desorption kinetics of poly- and perfluoroalkyl substances (PFAS) from a vadose zone soil exposed decades ago to aqueous f...

Supercritical Fluid Chromatography (SFC-UV) employing a carbon dioxide (CO 2) and 10 mM ammonium acetate in MeOH-water (95:5 v/v) gradient provides a rapid analysis (t G

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.

On reflection of how challenging the year 2020 was globally, it is testament to the commitment and dedication of the scientific research community around the world that Environmental Science& Technology (ES&T) continued to receive exceptional and outstanding quality research work during this period. In 2020, ES&T published approximately 1700 manuscripts, sharing novel and impactful research accomplishments across a broad and interdisciplinary range of environmental science and technology areas. The determination of our community to continue to research, innovate, and publish despite the many constraints is inspirational.

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

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.

Per- and polyfluoroalkyl substances (PFAS) have emerged as contaminants of environmental concern following release from industrial practices and use of aqueous film-forming foam (AFFF). Of the identified PFAS in surface water samples from known AFFF release sites, perfluorooctanesulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS) are frequently detected. The focus of the present study was to determine the effects of PFOS and PFHxS to the native (and common) fathead minnow, Pimephales promelas, over critical life stages of reproduction and development. Two separate, 42-d experiments were carried out using sexually mature fish, exposed to either PFOS or PFHxS. Measured exposure concentrations for PFOS and PFHxS were 0, 44, 88, 140, and 231 µg/L and 0, 150, 300, 600, and 1200 µg/L, respectively. At day 21 of the adult exposure, eggs were collected and reared for 21 d to determine the effects of PFOS or PFHxS on development, growth, and survival of larvae. The no-observable-effect concentration (NOEC) for PFOS was 44 µg/L, and the lowest-observable-effect concentration was 88 µg/L based on reduced growth in juvenile (F1) fish. Effects from PFOS exposures that did not follow a standard dose-response curve were reduced gonadosomatic index in adult males (at 44 µg/L) and reduced fecundity in females (at 140 µg/L). There was no toxicity on apical endpoints to report on adult or juvenile fish exposed to PFHxS up to 1200 µg/L. Importantly, we note that both PFOS and PFHxS accumulated in gonads and liver of adult fish following the respective exposures. The present study supports previous literature on PFOS toxicity and accumulation in fathead minnows but resulted in a lower NOEC than previously established for this species. Environ Toxicol Chem 2021;40:811-819. © 2020 SETAC.

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 C