Non-Target and Suspect Screening of Per- and Polyfluoroalkyl Substances in Airborne Particulate Matter in China

Target and Nontarget Screening of PFAS in Biosolids, Composts, and Other Organic Waste Products for Land Application in France

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFAS) are increasingly reported in terrestrial and aquatic environments, but their inputs to agricultural lands are not fully understood. Here, we characterized PFAS in 47 organic waste products (OWP) applied in agricultural fields of France, including historical and recent materials. Overall, 160 PFAS from 42 classes were detected from target screening and homologue-based nontarget screening. Target PFAS were low in agriculture-derived wastes such as pig slurry, poultry manure, or dairy cattle manure (median ∑₄₆PFAS: 0.66 μg/kg dry matter). Higher PFAS levels were reported in urban and industrial wastes, paper mill sludge, sewage sludge, or residual household waste composts (median ∑₄₆PFAS: 220 μg/kg). Historical municipal biosolids and composts (1976-1998) were dominated by perfluorooctanesulfonate (PFOS), N-ethyl perfluorooctanesulfonamido acetic acid (EtFOSAA), and cationic and zwitterionic electrochemical fluorination precursors to PFOS. Contemporaneous urban OWP (2009-2017) were rather dominated by zwitterionic fluorotelomers, which represented on average 55% of ∑₁₆₀PFAS (max: 97%). The fluorotelomer sulfonamidopropyl betaines (X:2 FTSA-PrB, median: 110 μg/kg, max: 1300 μg/kg) were the emerging class with the highest occurrence and prevalence in contemporary urban OWP. They were also detected as early as 1985. The study informs for the first time that urban sludges and composts can be a significant repository of zwitterionic and cationic PFAS.

Per- and Polyfluoroalkyl Substances in Outdoor and Indoor Dust from Mainland China: Contributions of Unknown Precursors and Implications for Human Exposure

Per- and polyfluoroalkyl substances (PFASs) were analyzed in outdoor (n = 101) and indoor dust (n = 43, 38 paired with outdoors) samples across mainland China. From 2013 to 2017, the median concentration of ∑PFASs in outdoor dust tripled from 63 to 164 ng/g with an elevated contribution of trifluoroacetic acid and 6:2 fluorotelomer alcohol. In 2017, the indoor dust levels of ∑PFASs were in the range 185-913 ng/g, which were generally higher than the outdoor dust levels (105-321 ng/g). Emerging PFASs were found at high median levels of 5.7-97 ng/g in both indoor and outdoor dust samples. As first revealed by the total oxidized precursors assay, unknown perfluoroalkyl acid (PFAA)-precursors contributed 37-67 mol % to the PFAS profiles in indoor dust samples. A great proportion of C8 PFAA-precursors were precursors for perfluorooctanesulfonic acid, while C6 and C4 PFAA-precursors were mostly fluorotelomer based. Furthermore, daily perfluorooctanoic acid (PFOA) equivalent intakes of PFAAs (C4-C12) mixtures via indoor dust were first estimated at 1.3-1.5 ng/kg b.w./d for toddlers at high scenarios, which exceeds the derived daily threshold of 0.63 ng/kg b.w./d. from the European Food Safety Authority (EFSA). On this basis, an underestimation of 56%-69% likely remains without considering potential risks due to the biotransformation of unknown PFAA-precursors.

Degradation of OBS (Sodium p-Perfluorous Nonenoxybenzenesulfonate) as a Novel Per- and Polyfluoroalkyl Substance by UV/Persulfate and UV/Sulfite: Fluorinated Intermediates and Treatability in Fluoroprotein Foam

Sodium p-perfluorous nonenoxybenzenesulfonate (OBS) is a novel fluorosurfactant used as the alternative to perfluorooctanesulfonic acid (PFOS) in several applications such as fire-fighting foams and chemical enhanced oil recovery ("EOR") in China, with the annual production capacity of about 3,500 t. Here, for the first time, we investigated the degradability of OBS under the conditions of UV/persulfate (UV/PS) and UV/sulfite (UV/SF) as typical redox processes. A higher reaction rate (1.05 min^-1) and total organic carbon (TOC) reduction (46.9%) but a low defluorination rate (27.6%) along with the formation of a series of fluorinated intermediates were found in UV/PS, while a high defluorination rate (87.7%) was realized in UV/SF. In particular, a nontargeted workflow using high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC/Q-TOF-MS) was established to detect fluorinated intermediates. Combined with the theoretical calculation, the distinctive degradation pathways in both oxidation and reduction processes were proposed. The degradation mechanism of OBS in UV/SF was proposed to be H/F exchange and subsequent HF elimination. Furthermore, the diluted OBS-based fluoroprotein (FP) foam was used to investigate the degradation of OBS, which confirms the treatability using the redox approach. This work provides insights into the degradability of OBS, fluorinated intermediate search, and proper treatment of related contamination.

Beyond the Tip of the Iceberg: Suspect Screening Reveals Point Source-Specific Patterns of Emerging and Novel Per- and Polyfluoroalkyl Substances in German and Chinese Rivers

Only a few dozens of the several thousand existing per- and polyfluoroalkyl substances (PFAS) are monitored using conventional target analysis. This study employed suspect screening to examine patterns of emerging and novel PFAS in German and Chinese river water affected by industrial point sources. In total, 86 PFAS were (tentatively) identified and grouped into 18 structure categories. Homologue patterns revealed distinct differences between fluoropolymer production sites of the two countries. In the Chinese Xiaoqing River Basin, the C₈ homologue was the most prevalent compound of the emerging series of chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs) and perfluoroalkylether carboxylic acids (PFECAs). In contrast, C₆ and shorter homologues were dominant in the German Alz River. This indicates that the phaseout of long-chain compounds in Europe and their ongoing production in Asian countries also apply to unregulated emerging PFAS classes. Additional characteristics to differentiate the point sources were the peak area ratio of perfluorobutane sulfonic acid (PFBS) versus the emerging compound hydro-substituted PFBS (H-PFBS) as well as the occurrence of byproducts of the sulfonated tetrafluoroethylene-based polymer Nafion. The large number of identified unregulated PFAS underlines the importance of a grouping approach on a regulatory level, whereas the revealed contamination patterns can be used to estimate, prioritize, and minimize contributions of specific sources.

Per- and polyfluoralkyl substances (PFAS) in drinking water system: Target and non-target screening and removal assessment

The massive use and the persistence of per- and polyfluoroalkyl substances (PFAS) have led to their frequent detection in aquatic environments, which may further threaten drinking water safety. So far, our knowledge about the occurrence of PFAS in drinking water system is still very limited. Here we investigated the occurrence and removal of PFAS in a drinking water system using non-target, suspect and target screening strategies. Sampling was performed in three seasons in the drinking water system including a water source, two drinking water treatment plants, and tap water in five households. The results showed detection of 17 homologous series with 51 homologues in non-target screening and 50 potential PFAS detected in suspect screening. Probable structures were proposed for 15 PFAS with high confidence levels (the first three of the five levels), with seven of them being reported for the first time in drinking water system. Semi-quantification was performed on seven homologous series based on target PFAS, the estimated total concentrations for non-target PFAS ranged between 4.10 and 17.6 ng/L. Nine out of 50 target PFAS were found and precisely quantified (<LOQ-13.4 ng/L) with predominance of perfluorocarboxylic acids (PFCA) and perfluorosulfonic acids (PFSA). All target and non-target PFAS were detected in tap water with similar concentrations in all three seasons. Removal efficiency for the detected PFAS in each processing unit was almost zero, indicating the recalcitrance of these chemicals to the conventional treatment process. The findings from this study clearly show the wide presence of PFAS in the whole drinking water treatment process, and suggest an urgent need for effective removal technology for this group of chemicals.

Methods for the analysis of endocrine disrupting chemicals in selected environmental matrixes

Endocrine disrupting chemicals (EDCs) are heterogenous in structure, chemical and physical properties, and their capacity to partition into various environmental matrixes. In many cases, these chemicals can disrupt the endocrine systems of vertebrate and invertebrate organisms when present at very low concentrations. Therefore, sensitive and varied analytical methods are required to detect these compounds in the environment. This review summarizes the analytical methods and instruments that are most used to monitor for EDCs in selected environmental matrixes. Only those matrixes for which there is a clear link between exposures and endocrine effects are included in this review. Also discussed are emerging methods for sample preparation and advanced analytical instruments that provide greater selectivity and sensitivity.

Legacy and Emerging Per- and Polyfluoroalkyl Substances Behave Distinctly in Spatial Distribution and Multimedia Partitioning: A Case Study in the Pearl River, China

Per- and polyfluoroalkyl substances (PFASs) have attracted worldwide attention due to their ubiquitous occurrence, bioaccumulation, and toxicological effects, yet the fate of PFASs in a lotic ecosystem is largely unknown. To elucidate spatial distribution and multimedia partitioning of legacy and emerging PFASs in a lotic river flowing into an estuary, PFASs were synchronously analyzed in water, suspended particulate matter (SPM), sediment, and biota samples collected along Guangzhou reach of the Pearl River, South China. Geographically, the concentrations of PFASs in the water phase showed a decreasing trend from the upper and middle sections (urban area) to the down section (suburban area close to estuary) of the river. While perfluorooctanoic acid predominated in water and SPM, more diverse compositions were observed in sediment and biota with the increase in contributions of long-chain PFASs. Field-derived sediment-water partitioning coefficients (K_d) and bioaccumulation factors (BAFs) of PFASs increased with the increase in perfluorinated carbons. Besides hydrophobicity, water pH and salinity significantly affected the multimedia partitioning of PFASs in a lotic ecosystem. In addition, 87 homologues (63 classes) were identified as emerging PFASs in four media using suspect analysis. Interestingly, K_d and BAF of the emerging PFASs were often higher than legacy PFASs containing the same perfluorinated carbons, raising a special concern on the environmental risk of emerging PFASs.

Recent advances in mass spectrometry analytical techniques for per- and polyfluoroalkyl substances (PFAS)

The ubiquitous presence of per- and polyfluoroalkyl substances (PFAS) in various environments has led to increasing concern, and these chemicals have been confirmed as global contaminants. Following the chemical regulatory restrictions imposed, PFAS alternatives that are presumed to be less toxic have been manufactured to replace the traditional ones in the market. However, owing to the original release and alternative usage, continuous accumulation of PFAS has been reported in environmental and human samples, with uncertain consequences for ecosystem and human health. It is crucial to promote and improve existing analytical techniques to facilitate the detection of trace amounts of PFAS in diverse environmental matrices. This review summarizes analytical methods that have been applied to and advanced for targeted detection and suspect screening of PFAS, which mainly include (i) sampling and sample preparation methods for various environment matrices and organisms, and quality assurance/quality control during the analysis process, and (ii) quantitative methods for targeted analysis and automated suspect screening strategies for non-targeted PFAS analysis, together with their applications, advantages, shortcomings, and need for new method development.

Per- and polyfluoroalkyl substances in the atmospheric total suspended particles in Karachi, Pakistan: Profiles, potential sources, and daily intake estimates

Per- and polyfluoroalkyl substances (PFAS) have received continuous attention; however, there is limited understanding of their sources in the atmosphere and related human exposure risks. This study measured PFAS in the atmospheric total suspended particles collected from Karachi, Pakistan, during the winter. Among the quantified PFAS, perfluorobutanoic acid (PFBA) showed the highest average concentration (3.11 ± 2.64 pg/m³), accounting for 32% of the total PFAS. Wind speed was positively correlated with perfluorohexanoic acid (PFHxA) and N-ethyl perfluorooctanesulfonamide (N-EtFOSA), while relative humidity was negatively correlated with perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Weighted potential source contribution function (WPSCF) and concentration weighted trajectory (WCWT) analyses suggested that northwestern Pakistan and western Afghanistan areas were highly associated with the long-range atmospheric transport of PFAS. We also calculated the daily intake of PFAS via inhalation, which were in the range of 0.07-3.98 and 0.01-0.33 pg/kg bw/d for children and adults, respectively. The calculated hazard quotient (HQ) of PFOS and PFOA was significantly lower than 1, indicating less or unlikely to cause non-carcinogenic effect via inhalation exposure. Overall, this study contributes to the understanding of geographic origins and human inhalation risks of airborne PFAS on a regional scale.

Sample preparation techniques for suspect and non-target screening of emerging contaminants

The progress in sensitivity and resolution in mass spectrometers in recent years provides the possibility to detect a broad range of organic compounds in a single procedure. For this reason, suspect and non-target screening techniques are gaining attention since they enable the detection of hundreds of known and unknown emerging contaminants in various matrices of environmental, food and human sources. Sample preparation is a critical step before analysis as it can significantly affect selectivity, sensitivity and reproducibility. The lack of generic sample preparation protocols is obvious in this fast-growing analytical field, and most studies use those of traditional targeted analysis methods. Among them, solvent extraction and solid phase extraction (SPE) are widely used to extract emerging contaminants from solid and liquid sample types, respectively. Sequential solvent extraction and a combination of different SPE sorbents can cover a broad range of chemicals in the samples. Gel permeation chromatography (GPC) and adsorption chromatography, including acidification, are typically used to remove matrix components such as lipids from complex matrices, but usually at the expense of compound losses. Ideally, the purification of samples intended for non-target analysis should be selective of matrix interferences. Recent studies have suggested quality assurance/quality control measures for suspect and non-target screening, based on expansion and extrapolation of target compound lists, but method validations remain challenging in the absence of analytical standards and harmonized sample preparation approaches.

Legacy and emerging poly- and perfluorochemicals in seawater and sediment from East China Sea

Following the global phase out of perfluorooctane sulfate (PFOS), chlorinated polyfluoroalkyl ether sulfonates (Cl-PFAESs) and p-perfluorous nonenoxybenzenesulfonate (PFNOBS) have emerged as novel PFOS substitutes. However, until now, limited data is available on their occurrence and environmental behaviors in the marine environment. Here, seawater and sediment samples were collected from East China Sea and analyzed for Cl-PFAESs, PFNOBS, and perfluoroalkyl acids (PFAAs; including their branched isomers) to investigate their concentrations, potential sources, and sediment-seawater partitioning behaviors. Perfluorooctanoate (PFOA) and PFOS were consistently the predominant PFAAs in seawaters and sediments. Branched PFOA and PFOS isomers were consistently much less frequently detected in sediments than that in seawaters. Linear PFOA contributed 92-95% of total PFOA in seawaters, suggesting the great contribution of telomerization PFOA. 6:2 Cl-PFAES was detected in all seawaters (concentration, 0.58-47 pg/L) and in the majority of sediments (<LOD-28 pg/g). PFNOBS was observed in 46% of seawater samples (concentration, <LOD-5.2 pg/L) and 66% of sediment samples (<LOD-1.7 pg/g). Spatial distribution trend suggested the riverine input as an important source of PFAAs and 6:2 Cl-PFAES in this sampling area. 6:2 Cl-PFAES (log K_oc, 2.6 ± 0.36) and PFNOBS (2.7 ± 0.33) had comparable mean log-transformed sediment-seawater partitioning coefficients (log K_oc) to PFOA (2.5 ± 0.32) or PFOS (2.8 ± 0.49), indicating their long-range transport potential in global oceans with ocean currents. Overall, this study provides the first data on occurrence and partitioning behaviors of 6:2 Cl-PFAES and PFNOBS in the marine environment.

Exposure to legacy and novel perfluoroalkyl substance disturbs the metabolic homeostasis in pregnant women and fetuses: A metabolome-wide association study

BACKGROUND

Perfluoroalkyl substances (PFASs) exist extensively and several of these have been verified to be toxic. Prenatal exposure to PFASs has attracted much attention. Metabolome-wide association analyses can be used to explore the toxicity mechanisms of PFASs by identifying associated biomarkers.

OBJECTIVES

To evaluate associations between the metabolites in maternal and cord serum and internal exposure to several common PFASs.

METHODS

Paired maternal and cord serum samples were collected from 84 pregnant women who gave birth between 2015 and 2016. Seven legacy and two novel PFASs were measured. A nontarget metabolomic method and an iterative metabolite annotation based on metabolic pathways were applied to characterize the metabolic profiles. Linear regression adjusted with the false discovery rate and covariates was used to indicate the associations.

RESULTS

A total of 279 features in maternal serum and 338 features in cord serum were identified as metabolites associated with PFAS exposure. Perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) were two PFASs associated with more metabolites, while the two novel chlorinated polyfluorinated ether sulfonic acids (Cl-PFESAs) showed less relevance to the metabolome. With pathway enrichment analysis, we found that three fatty acid metabolisms and retinol metabolism were correlated with PFAS exposure in maternal blood, and that sterol metabolism showed the correlation in both maternal serum and cord serum.

CONCLUSIONS

We identified metabolites and pathways in pregnant women and fetuses associated with the exposure to several PFAS, indicating a promising application for metabolome-wide association studies. Additional research is needed to confirm causation.

Increased disinfection byproducts in the air resulting from intensified disinfection during the COVID-19 pandemic

Intensified use of disinfectants to control COVID-19 could unintentionally increase the disinfection byproducts (DBPs) in the environment. In indoor spaces, it is critical to determine the optimal disinfection practice to prevent the spread of the virus while keeping DBPs at relatively low levels in the air. The formation of DBPs exceed 0.1 μg/mg while hypochlorite dosed at >10 mg/m³. The total DBP concentrations in highly disinfected places (100-200 mg/m³ hypochlorite) were as high as 66.8 μg/m³, and the Hazard Index (HI) was up to 0.84, and both values were much higher than those in less disinfected places (<10 mg/m³ hypochlorite). Taking into account the HI, formation yields and the origin of the DBPs, we recommended 10 mg/m³ as the suggested hypochlorite dose to minimize DBPs generation during routine disinfection for controlling the coronavirus. DBPs in indoor air could be eliminated by ventilation, reducing the usage of personal care products, and wiping the solid surface with water before or after disinfection. These results highlighted the necessity to control air-borne DBPs and their associated health risks arising from intensified disinfection, and will guide the further development of evidence-based regulation on DBP exposure during disinfection and improve public health protection.

LC-HRMS screening of per- and polyfluorinated alkyl substances (PFAS) in impregnated paper samples and contaminated soils

High per- and polyfluorinated alkyl substance (PFAS) concentrations have been detected in agricultural soils in Southwest Germany. Discharges of PFAS-contaminated paper sludge and compost are suspected to be the cause of the contamination. Perfluorinated carboxylic acids (PFCAs) have been detected also in groundwater, drinking water, and plants in this area. Recently, previously unknown compounds have been identified by high-resolution mass spectrometry (HRMS). Major contaminants were polyfluorinated dialkylated phosphate esters (diPAPs) and N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diester (diSAmPAP). In this study, HRMS screening for PFAS was applied to 14 soil samples from the contaminated area and 14 impregnated paper samples which were from a similar period than the contamination. The paper samples were characterized by diPAPs (from 4:2/6:2 to 12:2/12:2), fluorotelomer mercapto alkyl phosphates (FTMAPs; 6:2/6:2 to 10:2/10:2), and diSAmPAP. In soil samples, diPAPs and their transformation products (TPs) were the major contaminants, but also FTMAPs, diSAmPAP, and their TPs occurred. The distribution patterns of the carbon chain lengths of the precursor PFAS in soil samples were shown to resemble those in paper samples. This supports the hypothesis that paper sludge is a major source of contamination. The presence of major degradation products like PFCAs, FTSAs, or PFOS and their distribution of carbon chain lengths indicate the activity of biotic or abiotic degradation processes and selective leaching processes from the upper soil horizons.

Suspect and non-target screening: the last frontier in environmental analysis

Suspect and non-target screening (SNTS) techniques are arising as new analytical strategies useful to disentangle the environmental occurrence of the thousands of exogenous chemicals present in our ecosystems. The unbiased discovery of the wide number of substances present over environmental analysis needs to find a consensus with powerful technical and computational requirements, as well as with the time-consuming unequivocal identification of discovered analytes. Within these boundaries, the potential applications of SNTS include the studies of environmental pollution in aquatic, atmospheric, solid and biological samples, the assessment of new compounds, transformation products and metabolites, contaminant prioritization, bioremediation or soil/water treatment evaluation, and retrospective data analysis, among many others. In this review, we evaluate the state of the art of SNTS techniques going over the normalized workflow from sampling and sample treatment to instrumental analysis, data processing and a brief review of the more recent applications of SNTS in environmental occurrence and exposure to xenobiotics. The main issues related to harmonization and knowledge gaps are critically evaluated and the challenges of their implementation are assessed in order to ensure a proper use of these promising techniques in the near future.

Suspect Screening, Prioritization, and Confirmation of Environmental Chemicals in Maternal-Newborn Pairs from San Francisco

Our proof-of-concept study develops a suspect screening workflow to identify and prioritize potentially ubiquitous chemical exposures in matched maternal/cord blood samples, a critical period of development for future health risks. We applied liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-QTOF/MS) to perform suspect screening for ∼3500 industrial chemicals on pilot data from 30 paired maternal and cord serum samples (n = 60). We matched 662 suspect features in positive ionization mode and 788 in negative ionization mode (557 unique formulas overall) to compounds in our database, and selected 208 of these for fragmentation analysis based on detection frequency, correlation in feature intensity between maternal and cord samples, and peak area differences by demographic characteristics. We tentatively identified 73 suspects through fragmentation spectra matching and confirmed 17 chemical features (15 unique compounds) using analytical standards. We tentatively identified 55 compounds not previously reported in the literature, the majority which have limited to no information about their sources or uses. Examples include (i) 1-(1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl)-3-dodecylpyrrolidine-2,5-dione (known high production volume chemical) (ii) methyl perfluoroundecanoate and 2-perfluorooctyl ethanoic acid (two PFAS compounds); and (iii) Sumilizer GA 80 (plasticizer). Thus, our workflow demonstrates an approach to evaluating the chemical exposome to identify and prioritize chemical exposures during a critical period of development.

Hydrothermal Alkaline Treatment for Destruction of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam

The widespread use of aqueous film-forming foam (AFFF) for firefighting activities (e.g., fire training to extinguish fuel-based fires at aircraft facilities) has led to extensive groundwater and soil contamination by per- and polyfluoroalkyl substances (PFASs) that are highly recalcitrant to destruction using conventional treatment technologies. This study reports on the hydrothermal alkaline treatment of diverse PFASs present in AFFFs. Quantitative and semiquantitative high-resolution mass spectrometry analyses of PFASs demonstrate a rapid degradation of all 109 PFASs identified in two AFFFs (sulfonate- and fluorotelomer-based formulations) in water amended with an alkali (e.g., 1-5 M NaOH) at near-critical temperature and pressure (350 °C, 16.5 MPa). This includes per- and polyfluoroalkyl acids and a range of acid precursors. Most PFASs were degraded to nondetectable levels within 15 min, and the most recalcitrant perfluoroalkyl sulfonates were degraded within 30 min when treated with 5 M NaOH. ¹⁹F NMR spectroscopic analysis and fluoride ion analysis confirm the near-complete defluorination of PFASs in both dilute and concentrated AFFF mixtures, and no stable volatile organofluorine species were detected in reactor headspace gases by the gas chromatography-mass spectrometry analysis. These findings indicate a significant potential for application of hydrothermal treatment technologies to manage PFAS waste streams, including on-site treatment of unused AFFF chemical stockpiles, investigation-derived wastes, and concentrated source zone materials.

PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding

We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on 2 to 5 legacy PFAS, and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly, and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine measurements complemented by suspect screening using high-resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids. Available data suggest that diet is the major human exposure pathway for some PFAS, but there is large variability across populations and PFAS compounds. Additional data on total fluorine in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, for the general population, exposures from dust, personal care products, indoor environments, and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a reevaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations. Environ Toxicol Chem 2021;40:631-657. © 2020 SETAC.

Identification of organosiloxanes in ambient fine particulate matters using an untargeted strategy via gas chromatography and time-of-flight mass spectrometry

Organosilicons are widely used in consumer products and are ubiquitous in living environments. However, there is little systemic information on this group of pollutants in ambient particles. This study proposes a novel untargeted strategy based mainly on the mass difference of three silicon isotopes to screen organosilicon compounds from 2-year PM_2.5 samples of Beijing using gas chromatography and high-resolution time-of-flight mass spectrometry. 61 organosilicons were filtered from 1019 peaks, and 35 ones were identified as organosiloxanes including 17 methylsiloxanes and 18 phenylmethylsiloxanes, of which 6 and 3 species were confirmed using reference standards, respectively. These organosiloxanes could be clustered into three groups: low-silicon-number methylsiloxanes, high-silicon-number methylsiloxanes, and phenylmethylsiloxanes. Low-silicon-number methylsiloxanes showed high abundance in the heating season but low abundance in the non-heating season, whereas high-silicon-number methylsiloxanes showed the opposite seasonal variation. This study provides a promising strategy for screening organosilicon compounds through an untargeted approach and gives insights for further investigation of the sources and health risks of organosiloxanes.

Photodegradation of carbon dots cause cytotoxicity

Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.

Carbon dots have attracted much attention for biomedical applications but potential degradation and associated toxicity are still poorly understood. Here, the authors report on a study into the photo-degradation of carbon dots, the products produced and associated cytotoxicity.

Suspect and Nontarget Screening Revealed Class-Specific Temporal Trends (2000-2017) of Poly- and Perfluoroalkyl Substances in St. Lawrence Beluga Whales

The global use of >3000 per- and polyfluoroalkyl substances (PFASs) has given rise to chemical regulatory action. However, limited information exists regarding current and historical emissions for the majority of PFASs under currently implemented regulations. This study employed suspect and nontarget screening to examine the temporal trends of legacy and unregulated PFASs in liver of the endangered beluga whale (Delphinapterus leucas) population from the St. Lawrence Estuary in Canada collected from 2000 to 2017. A suite of 54 PFASs were tentatively identified, and were grouped into nine structurally distinct classes. Single-hydrogenated perfluoro carboxylic acids (H-PFCAs), single-hydrogenated sulfonamides (H-Sulfonamides), as well as other select sulfonamides were detected for the first time in wildlife. Greater concentrations of the majority of PFASs were determined in newborns and juveniles than in adults, suggesting effective placental and lactational transfer of PFASs. Legacy per- and polyfluoroalkyl acids and perfluorooctane sulfonamide in beluga whale liver were found to significantly decrease in concentration between 2000 and 2017, while unregulated short-chain PFAS alternatives, H-PFCAs, and odd-chain FTCAs were found to increase over time. The implementation of suspect and nontarget screening revealed class-specific temporal trends of PFASs in SLE beluga whales, and supported continuous emissions of unregulated PFASs into the environment.

Non-targeted identification of per- and polyfluoroalkyl substances at trace level in surface water using fragment ion flagging

The extent of unidentified Per- and Poly-fluoroalkyl substances (PFASs) found in environmental samples has led to the development of non-targeted screening methods. The study presented here reports the use of liquid chromatography hyphenated with high resolution mass spectrometry to detect and identify unknown and unexpected PFASs by fragment ion flagging (FIF). By exploring all ion fragmentation spectra for several characteristic fragments including C_nF_2n+1^-, C_nF_2n-1^-, C_nF_2n-3^-, C_nF_2n-7^-, C_nF_2n-11^- and C_nF_2n+1O^- the presence of widely different PFAS species can be anticipated without the need for targeted screening methods. These fragments are then related to their precursor ion by retention time matching and subsequently identified. With this methodology 40 PFASs were (tentatively) identified in four surface water samples sampled throughout the Netherlands. To the best of the authors' knowledge, four PFASs found through FIF are newly discovered species and have not been mentioned in any database or literature. This methodology eliminates the dependence on commonly reported full scan feature selection techniques such as mass defect filtering, homologous series detection and intensity threshold filtering, allowing the identification of PFASs at trace levels. Additionally, eight of the (tentatively) identified PFASs are not part of homologous series, stressing the shortcomings of commonly reported non-targeted PFASs screening methods and demonstrating the importance of more effective identification strategies such as FIF. Moreover, we like to emphasise that this approach is applicable to real-life environmental samples with PFASs at background concentration levels.

Target, Nontarget, and Suspect Screening and Temporal Trends of Per- and Polyfluoroalkyl Substances in Marine Mammals from the South China Sea

Per- and polyfluoroalkyl substances (PFASs) have been manufactured and widely used for over 60 years. Currently, there are thousands of marketed PFASs, but only dozens of them are routinely monitored. This work involved target, nontarget, and suspect screening of PFASs in the liver of Indo-Pacific humpback dolphin (Sousa chinensis) and finless porpoise (Neophocaena phocaenoides), two resident marine mammals in the South China Sea, stranded between 2012 and 2018. Among the 21 target PFASs, perfluorooctane sulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) predominated in the samples, accounting for 46 and 30% of the total PFASs, respectively. Significantly higher total target PFAS concentrations (p < 0.05) were found in dolphin liver samples [3.23 × 10³ ± 2.63 × 10³ ng/g dry weight (dw)] than in porpoise liver samples (2.63 × 10³ ± 1.10 × 10³ ng/g dw). Significant increasing temporal trends (p < 0.05) were found in the concentrations of two emerging PFASs, perfluoroethylcyclohexane sulfonate and 2,3,3,3-tetrafluoro-2-propanoate in porpoises, indicating increasing pollution by these emerging PFASs. Forty-four PFASs from 9 classes were additionally identified by nontarget and suspect screening, among which 15 compounds were reported for the first time in marine mammals. A primary risk assessment showed that the emerging PFAS 6:2 Cl-PFESA could have possible adverse effects in terms of reproductive injury potential on most of the investigated cetaceans.

Data-independent acquisition with ion mobility mass spectrometry for suspect screening of per- and polyfluoroalkyl substances in environmental water samples

Per- and polyfluoroalkyl substances (PFASs) have environmentally persistent, and the various types of PFASs have been detected in water environments. Many previous studies have performed data-dependent acquisition (DDA) of mass spectra from an environmental sample by high-resolution mass spectrometry to identify PFAS suspects individually. In comparison, the data-independent acquisition (DIA) of comprehensive mass spectra of the sample is a technology which enables to know the occurrences of suspects and non-targets simultaneously. However, it is difficult to associate the fragment ions of targeted precursor ions by retention time only, because of the existence of co-eluting ions derived from environmental samples. Since the separation of ions is not enough with only the conventional DIA method, here, we attempted to support it using ion mobility mass spectrometry (IMS) to distinguish the relevant ions from co-eluting ions by drift time. Firstly, suspect screening of PFASs with eternal database resulted in determining 32-96 PFAS suspects in firefighting foam impacted groundwater samples (n = 8) by suspect screening. Among all the pairs of respective precursor ions and fragment ions of the PFAS suspects, 5%-19% (4-9 PFASs) of them were associated without considering the drift time of IMS, while 37%-49% (15-43 PFASs) of them were associated with considering the drift time. The consideration of the drift time increased the association ratios in all samples. In a sample, most precursor ions could be associated with their fragment ions (41 of 43 PFASs) because at least one probable fragment ion was observed among three of maximum intensity fragment ions. Thus, the method improved the identification by excluding the unrelated co-eluting ions by IMS. Moreover, the method can acquire a certain reliable MS/MS spectra of suspects in environmental samples in one analysis. It is not essential to conduct instrumental analyses again for samples stored for a long time even when the data sets and/or methodologies of data analyses are modified (e.g., the original database, screening list, or statistical filtering/data cleaning approach). It will be particularly useful for studies that must analyze a large number of environmental samples.

Atmospheric particulate represents a source of C8-C12 perfluoroalkyl carboxylates and 10:2 fluorotelomer alcohol in tree bark

In this study, we analyzed 30 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in paired atmospheric particulate and bark samples collected around a Chinese fluorochemical manufacturing park (FMP), with the aim to explore the sources of PFASs in tree bark. The results showed that PFASs in atmospheric particulate and tree bark samples were consistently dominated by perfluorooctanoate (mean 73 ng/g; 44 pg/m3), perfluorohexanoate (47 ng/g; 36 pg/m3), perfluorononanoate (9.1 ng/g; 8.8 pg/m3), and 10:2 fluorotelomer alcohol (10:2 FTOH; 5.6 ng/g; 12 pg/m3). Spatially, concentrations of C8-C12 perfluoroalkyl carboxylates (PFCAs) and 10:2 FTOH all showed a similar and exponentially decreased trend in both bark and atmospheric particulate samples with the increasing distance from the FMP. For the first time, we observed strongly significant (Spearman's correlation coefficient = 0.53-0.79, p < 0.01) correlations between bark and atmospheric particulate concentrations for C8-C12 PFCAs and 10:2 FTOH over 1-2 orders of magnitude, suggesting that the continues trapping of atmospheric particulates resulted in the accumulation of these compounds in bark. Overall, this study provides the first evidence that atmospheric particulate is an obvious source of C8-C12 PFCAs and 10:2 FTOH in tree bark. This result may further contribute to the application of tree bark as an indicator of certain PFASs in atmospheric particulate.

Rapid Characterization of Emerging Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foams Using Ion Mobility Spectrometry-Mass Spectrometry

Aqueous film-forming foams (AFFF) are mixtures formulated with numerous hydrocarbon- and fluoro-containing surfactants. AFFF use leads to environmental releases of unknown per- and polyfluoroalkyl substances (PFAS). AFFF composition is seldom disclosed, and their use elicits concerns from both regulatory agencies and the public because PFAS are persistent in the environment and potentially associated with adverse health effects. In this study, we demonstrate the use of coupled liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) to rapidly characterize both known and unknown PFAS in AFFF. Ten AFFF formulations from seven brands were analyzed using LC-IMS-MS in both negative and positive ion modes. Untargeted analysis of the formulations was followed by feature identification of PFAS-like features utilizing database matching, mass defect and homologous series evaluation, and MS/MS fragmentation experiments. Across the tested AFFF formulations, we identified 33 homologous series; only ten of these homologous series have been previously reported. Among tested AFFF, the FireStopper (n = 85) contained the greatest number of PFAS-like features and Phos-Check contained zero. This work demonstrates that LC-IMS-MS-enabled untargeted analysis of complex formulations, followed by feature identification using data-processing algorithms, can be used for rapid exposure characterization of known and putative PFAS during fire suppression-related contamination events.

Per- and Polyfluoroalkyl Substances in the Air Particles of Asia: Levels, Seasonality, and Size-Dependent Distribution

Information regarding the size-dependent distribution of per- and polyfluoroalkyl substances (PFAS) in atmospheric particulate matter (PM) is very limited. In this study, 248 size-specific PM samples were collected from 9 Asian cities using a portable 4-stage cascade impactor for the analysis of PFAS. Of the 34 investigated PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were the major compounds. In particular, the emerging PFAS, hexafluoropropylene oxide dimer acid, was quantified in the PM for the first time, with concentrations ranging from <0.086 to 21.5 pg/m³. Spatially, PFOA and PFOS were the predominant compounds in China, while precursors, emerging PFAS, and short-chain PFAS dominated in India, Japan, and South Korea, respectively. Seasonal variations of PFAS may be controlled by regional climate, local or seasonal emission sources, and long-range transport of air masses. Size-dependent distribution was investigated, showing that the majority of PFAS predominantly affiliated in fine particles, while PFOS and its alternatives tended to attach on coarser particles. Moreover, PFOS distributed on specific sizes exhibited seasonal and regional dependency, while no such patterns were observed for PFOA. These findings will provide useful information on the geographical and size-dependent distribution of PFAS in the atmospheric PM.

Occurrence and Distribution of Per- and Polyfluoroalkyl Substances in Tianjin, China: The Contribution of Emerging and Unknown Analogues

Tianjin, located in Bohai Bay, China, constitutes a relevant study area to investigate emerging per- and polyfluoroalkyl substances (PFASs) due to its high population density, clustering of chemical and aircraft industries, as well as international airports, harbors, and oil rigs. In this study, 53 anionic, zwitterionic, and cationic PFASs were monitored in river surface water, groundwater, seawater, and sediments in this area (overall n = 226). 6:2 chlorinated polyfluorinated ether sulfonic acid (Cl-PFESA), perfluorooctanoic acid, and perfluorooctane sulfonic acid were generally the predominant PFASs. 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) was also widespread (occurrence >86%), with the highest concentration (1300 ng/L) detected at contamination hot spots impacted by wastewater effluents. The aqueous film-forming foam (AFFF)-related PFASs with sulfonamide betaine, amine oxide, amine, or quaternary ammonium moieties are also reported for the first time in river water and seawater samples. Fifteen classes of infrequently reported PFASs, including n:2 FTABs and n:2 fluorotelomer sulfonamide amines, hydrogen-substituted PFESA homologues, and p-perfluorous nonenoxybenzenesulfonate (OBS), were also identified in the water and sediment samples using suspect screening. Field-derived sediment-water distribution coefficients (K_d) of these emerging PFASs are provided for the first time, confirming that cationic and zwitterionic PFASs tend to be strongly associated with sediments.

Review on perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the Chinese atmospheric environment

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been manufactured and used for over 50 years, and now are worldwide distributed in the environment. The atmospheric environment is the main compartment for PFASs to be transported and transformed, and relevant research has highlighted the global occurrence and impacts of atmospheric PFASs in ecosystems and human health. With the phasing-out and restriction of eight‑carbon chain-length (C8) PFASs in developed countries, China has become the largest producer of C8 PFASs since 2004. Subsequently, a number of studies on PFASs in the Chinese atmospheric environment have been conducted in the recent decade. This review documented twenty-eight studies on PFASs in Chinese outdoor air published to date. Methods of sampling, extraction, cleanup, and instrumental analysis were summarized for both ionic and neutral PFASs. Levels, compositions, and spatial distribution of PFASs from different areas in China (i.e. source, urban, and remote regions, and north versus south China) were compared and discussed. Leaves and tree barks were proposed as effective bioindicators to reflect the contamination status of atmospheric PFASs. Special attention can be given to non-target screening for future research directions.

A profile analysis with suspect screening of per- and polyfluoroalkyl substances (PFASs) in firefighting foam impacted waters in Okinawa, Japan

Per- and polyfluoroalkyl substances (PFASs) are a group of persistent contaminants detected in firefighting foam impacted waters. Previous studies have performed suspect and non-target screening by high-resolution mass spectrometry (HRMS) to determine the composition of PFAS contamination and to discover unknown PFASs. Here, we performed a profile analysis with suspect screening against two lists in the NORMAN Suspect List Exchange in firefighting foam impacted environmental and drinking water (n = 18) collected in Okinawa, Japan, in April 2019. Samples were analyzed by liquid chromatography (LC) quadrupole time-of-flight (QTOF) MS in electron spray ionization mode. Suspect screening returned 116 candidate PFASs with their molecular weights, functional groups, and perfluoroalkyl chain lengths. Long-chain perfluoroalkyl acids (PFAAs) and some of their precursors were specifically found around the firefighting training area. Short-chain PFAAs were assumed to be formed from precursors by environmental processes. Perfluoroalkyl sulfonamide precursors were found to be transformed to perfluoroalkyl sulfonic acids (PFSAs) in the drinking water treatment process. In contrast, biological activated carbon filtration formed perfluoroalkyl carboxylic acids (PFCAs). The PFAS profile showed that a large number of different substances needs to be considered.

Non-target and suspect screening of per- and polyfluoroalkyl substances in Chinese municipal wastewater treatment plants

Wastewater treatment plant (WWTP) is one of the major sources of per- and polyfluoroalkyl substances (PFASs) to the aquatic environment. In this study, wastewater samples were collected from 17 WWTPs in 17 cities of China to investigate emerging PFASs in WWTPs. To comprehensively identify PFASs in the wastewater samples, an integrated suspect screening, homologue-based and fragment-based non-target screening method is proposed. Sixty-three PFASs from 13 classes (25 subclasses) were identified, including 14 legacy and 49 emerging PFASs, and this study is the first to report on 12 of these PFASs. We found that emerging PFASs concentration had a significantly positive correlation with the gross domestic product, indicating more substitution of legacy PFASs in the developed area of China. We also analyzed the removal of the 13 PFAS classes, and found that all discovered PFAS classes were not completely removed after the treatment process, whereas the class of perfluoroalkyl ether alcohols significantly increased. All of these results imply that the release of emerging or unknown PFASs from WWTPs is a universal but not negligible problem in China.

Tris(2,4-di-tert-butylphenyl)phosphate: An Unexpected Abundant Toxic Pollutant Found in PM2.5

A novel pollutant, tris(2,4-di-tert-butylphenyl)phosphate (I168O), was identified in urban fine particulate matter (PM_2.5) samples in a nontargeted screening based on mass spectrometry for the first time. I168O was detected in all samples collected from two typical cities far away from each other in China. The concentrations of I168O reached up to 851 (median: 153) ng/m³, indicating that it was a widespread and abundant pollutant in the air. The antioxidant Irgafos 168 [I168, tris(2,4-di-tert-butylphenyl)phosphite] popularly added in plastics was the most suspected source for the detected I168O. Simulation studies indicated that heating, UV radiation, and water contact might significantly (p < 0.05) transform I168 to I168O. In particular, I168O might be magnificently evaporated into the air at high temperatures. The outdoor inhalation exposure of I168O may exert substantial health risks.

Toward Comprehensive Per- and Polyfluoroalkyl Substances Annotation Using FluoroMatch Software and Intelligent High-Resolution Tandem Mass Spectrometry Acquisition

Thousands of per- and polyfluoroalkyl substances (PFAS) exist in the environment and pose a potential health hazard. Suspect and nontarget screening with liquid chromatography (LC)-high-resolution tandem mass spectrometry (HRMS/MS) can be used for comprehensive characterization of PFAS. To date, no automated open source PFAS data analysis software exists to mine these extensive data sets. We introduce FluoroMatch, which automates file conversion, chromatographic peak picking, blank feature filtering, PFAS annotation based on precursor and fragment masses, and annotation ranking. The software library currently contains ∼7 000 PFAS fragmentation patterns based on rules derived from standards and literature, and the software automates a process for users to add additional compounds. The use of intelligent data-acquisition methods (iterative exclusion) nearly doubled the number of annotations. The software application is demonstrated by characterizing PFAS in landfill leachate as well as in leachate foam generated to concentrate the compounds for remediation purposes. FluoroMatch had wide coverage, returning 27 PFAS annotations for landfill leachate samples, explaining 71% of the all-ion fragmentation (CF₂)_n related fragments. By improving the throughput and coverage of PFAS annotation, FluoroMatch will accelerate the discovery of PFAS posing significant human risk.

Novel and legacy poly- and perfluoroalkyl substances (PFASs) in indoor dust from urban, industrial, and e-waste dismantling areas: The emergence of PFAS alternatives in China

With the phase out of perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), the composition profiles of poly- and perfluoroalkyl substance (PFAS) in our living environment are unclear. In this study, 25 PFASs were analyzed in indoor dust samples collected from urban, industrial, and e-waste dismantling areas in China. PFOS alternatives, including 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (median: 5.52 ng/g) and 8:2 chlorinated polyfluorinated ether sulfonate (8:2 Cl-PFESA) (1.81 ng/g), were frequently detected. By contrast, PFOA alternatives, such as hexafluoropropylene oxide dimer acid (HPFO-DA, Gen-X) and ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA), were not found in any of the dust samples. As expected, all legacy PFASs were widely observed in indoor dust, and 4 PFAS precursors were also detected. Dust concentrations of 6:2 Cl-PFESA were strongly correlated (p < 0.05) with those of 8:2 Cl-PFESA regardless of sampling sites. 6:2 Cl-PFESA was also significantly associated with that of PFOS in industrial and e-waste (p < 0.01) areas. Association analysis suggested that the sources of PFOS and its alternatives are common or related. Although ∑Cl-PFESA concentration was lower than that of PFOS (17.4 ng/g), industrial areas had the highest 6:2 Cl-PFESA/PFOS ratio (0.63). Composition profiles of PFASs in the industrial area showed the forefront of fluorine change. Thus, the present findings suggested that Cl-PFESAs are widely used as PFOS alternatives in China, and high levels of human Cl-PFESA exposure are expected in the future. Short-chain PFASs (C4-C7) were the predominant PFASs found in dust samples, contributing to over 40% of ∑total PFASs. Furthermore, perfluoro-1-butanesulfonate/PFOS and perfluoro-n-butanoic acid (PFBA)/PFOA ratios were 2.8 and 0.72, respectively. These findings suggested shifting to the short-chain PFASs in the environment in China. To the authors knowledge this is the first study to document the levels of 6:2 Cl-PFESA, 8:2 Cl-PFESA in indoor dust.

Emerging and legacy per- and polyfluoroalkyl substances in water, sediment, and air of the Bohai Sea and its surrounding rivers

Per- and polyfluoroalkyl substances (PFASs) contamination in the Bohai Sea and its surrounding rivers has attracted considerable attention in recent years. However, few studies have been conducted regarding the distribution of PFASs in multiple environmental media and their distributions between the suspended particles and dissolved phases. In this study, surface water, surface sediment, and air samples were collected at the Bohai Sea to investigate the concentration and distribution of 39 targeted PFASs. Moreover, river water samples from 35 river estuaries were collected to estimate PFAS discharge fluxes to the Bohai Sea. The results showed that total ionic compound (Σi-PFASs) concentrations ranged from 19.3 to 967 ng/L (mean 125 ± 152 ng/L) in the water and 0.70-4.13 ng/g dw (1.78 ± 0.76 ng/g) in surface sediment of the Bohai Sea, respectively. In the estuaries, Σi-PFAS concentrations were ranged from 10.5 to 13500 ng/L (882 ± 2410 ng/L). In the air, ΣPFAS (Σi-PFASs + Σn-PFASs) concentrations ranged from 199 to 678 pg/m³ (462 ± 166 pg/m³). Perfluorooctanoic acid (PFOA) was the predominant compound in the seawater, sediment, and river water; in the air, 8:2 fluorotelomer alcohol was predominant. Xiaoqing River discharged the largest Σi-PFAS flux to the Bohai Sea, which was estimated as 12,100 kg/y. Some alternatives, i.e., 6:2 fluorotelomer sulfonate acid (6:2 FTSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and chlorinated 6:2 polyfluorinated ether sulfonic acid (Cl-6:2 PFESA), showed higher levels than or comparable concentrations to those of the C8 legacy PFASs in some sampling sites. The particle-derived distribution coefficient in seawater was higher than that in the river water. Using high resolution mass spectrometry, 29 nontarget emerging PFASs were found in 3 river water and 3 seawater samples. Further studies should be conducted to clarify the sources and ecotoxicological effects of these emerging PFASs in the Bohai Sea area.

Suspect screening and risk assessment of pollutants in the wastewater from a chemical industry park in China

Owing to the production and use of chemicals in chemical industry parks (CIPs), these areas are considered to be highly polluted. However, the type of pollutants presents in the wastewater from CIPs and the risk posed to the environment due to the release of these pollutants remains unclear. In this study, suspect screening was combined with traceability analysis to determine the type of pollutants present in wastewaters at 9 chemical enterprises and wastewater treatment plants (WWTPs) in the CIPs. Additionally, the distribution of nine pollutants from the WWTPs' effluent stage and the risk they posed to the surrounding river was examined through target analysis. Upon conducting suspect analysis, the presence of 65 and 64 chemicals in the 9 chemical enterprises' wastewaters and WWTPs, respectively, was tentatively identified. Traceability analysis of the compounds screened in the effluent from the WWTPs determined that 41 substances were identified as characteristic pollutants of the chemical enterprises, indicating that the suspect screening strategy enabled relatively more efficient identification of the characteristic pollutants compared to traditional quantitative analysis. Targeting analysis combined with ecological risk assessment showed that metolachlor, carbendazim, atrazine, diuron, and chlorpyrifos posed relatively higher risks to aquatic organisms in the surrounding river. Therefore, the refined management of the wastewater treatment plant in the CIPs is necessary.

Nontarget Screening of Per- and Polyfluoroalkyl Substances Binding to Human Liver Fatty Acid Binding Protein

More than 1000 per- and polyfluoroalkyl substances (PFASs) have been discovered by nontarget analysis (NTA), but their prioritization for health concerns is challenging. We developed a method by incorporating size-exclusion column co-elution (SECC) and NTA, to screen PFASs binding to human liver fatty acid binding protein (hL-FABP). Of 74 PFASs assessed, 20 were identified as hL-FABP ligands in which eight of them have high binding affinities. Increased PFAS binding affinities correlate with stronger responses in electrospray ionization (ESI^-) and longer retention times on a C18 column. This is well explained by a mechanistic model, which revealed that both polar and hydrophobic interactions are crucial for binding affinities. Encouraged by this, we then developed an SECC method to identify hL-FABP ligands, and all eight high-affinity ligands were selectively captured from 74 PFASs. The method was further applied to an aqueous film-forming foam (AFFF) product in which 31 new hL-FABP ligands were identified. Suspect and nontargeted screening revealed these ligands as analogues of perfluorosulfonic acids and homologues of alkyl ether sulfates (C₈- and C₁₀/EO_n, C₈H₁₇(C₂H₄O)_nSO₄^-, and C₁₀H₂₁(C₂H₄O)_nSO₄^-). The SECC method was then applied to AFFF-contaminated surface waters. In addition to perfluorooctanesulfonic acid and perfluorohexanesulfonic acid, eight other AFFF chemicals were discovered as novel ligands, including four C₁₄- and C₁₅/EO_n. This study implemented a high-throughput method to prioritize PFASs and revealed the existence of many previously unknown hL-FABP ligands.

Novel and legacy per- and polyfluoroalkyl substances in bald eagle eggs from the Great Lakes region

Decades of large-scale production of per- and polyfluoroalkyl substances (PFASs) have resulted in their ubiquitous presence in the environment worldwide. Similarly to other persistent and bioaccumulative organic contaminants, some PFASs, particularly the long-chain congeners, can be biomagnified via food webs, making top predators vulnerable to elevated PFAS exposure. In this study, we measured seven classes of PFASs in bald eagle (Haliaeetus leucocephalus) eggs for the first time. The eggs (n = 22) were collected from the North American Great Lakes in 2000-2012. The ranges of total concentrations of perfluoroalkyl sulfonic acids (∑PFSAs) and perfluoroalkyl carboxylic acids (∑PFCAs) were 30.5-1650 and 5.4-216 ng/g wet weight (ww), respectively. In addition to these traditional PFAS compounds, 6:2 fluorotelomer sulfonic acid (6:2 FTS; median: 15.7 ng/g ww), perfluoro-4-ethylcyclohexanesulfonic acid (PFECHS; 0.22 ng/g ww), and 8-chloro-perfluorooctanesulfonic acid (Cl-PFOS, detected in wildlife for the first time; 0.53 ng/g ww) were also frequently detected. Bald eagle eggs from breeding areas located less than 8 km from a Great Lake shoreline or tributary had significantly greater total PFAS concentrations (∑PFASs) than those from breeding areas located further than 8 km (p < 0.05). In these samples, ∑PFASs rivalled the total concentration of brominated flame retardants, and were significantly greater than those of several other organic contaminants, such as dechlorane-related compounds, organophosphate esters, and flame retardant metabolites.

Ascertaining Hydrogen-Abstraction Reaction Efficiencies of Halogenated Organic Compounds in Electron Impact Ionization Processes by Gas Chromatography-High-Resolution Mass Spectrometry

H-Abstraction reactions occurring during electron impact ionization processes in electron ionization mass spectrometry (EI-MS) are a long-standing and crucial topic in MS research. Yet, some critical relevant mechanisms are controversial and ambiguous, and information about the EI-induced H-abstraction reactions of halogenated organic compounds (HOCs) is completely in the dark. This study provides a systematic investigation of H-abstraction reactions of HOCs taking place in the EI source using ¹³C₆-hexachlorobenzene (¹³C₆-HCB) and ¹³C₆-hexabromobenzene (¹³C₆-HBB) as exemplary compounds by gas chromatography (GC)-high-resolution mass spectrometry (GC-HRMS). The H-abstraction efficiencies were evaluated with the MS signal intensity ratios of ions with H-abstraction relative to the corresponding original ions (without H-abstraction). Ion source temperatures, EI energies, and numbers of heavy isotope atoms (³⁷Cl or ⁸¹Br) of isotopologues were investigated in terms of their effects on the H-abstraction efficiencies. The H-abstraction efficiencies of individual isotopologues generally decreased from the first to the last isotopologues of respective ions, and those of individual ions were different from each other, with the highest values of 0.017 and 0.444 for ¹³C₆-HCB and ¹³C₆-HBB, respectively. The overall H-abstraction efficiencies involving all measured ions of ¹³C₆-HCB and ¹³C₆-HBB were 0.004 and 0.128, respectively. With increasing ion source temperatures, the H-abstraction efficiencies first increased to a summit and then began to linearly decrease. EI energies and emission currents could impact the H-abstraction efficiencies but showed no certain tendency. The H-abstraction reactions were inferred to belong to ion-molecule reactions, and the siloxanes bleeding from the GC column might be a hydrogen source. Some strategies were proposed for eliminating or alleviating the interference triggered by the H-abstraction reactions in EI-MS in identification of halogenated organic pollutants (HOPs). Our findings provide a better understanding of the EI-induced H-abstraction reactions of HOCs and may benefit the identification of HOPs in environmental analysis, especially for novel HOPs.

Fluorine Mass Balance and Suspect Screening in Marine Mammals from the Northern Hemisphere

There is increasing evidence that the ∼20 routinely monitored perfluoroalkyl and polyfluoroalkyl substances (PFASs) account for only a fraction of extractable organofluorine (EOF) occurring in the environment. To assess whether PFAS exposure is being underestimated in marine mammals from the Northern Hemisphere, we performed a fluorine mass balance on liver tissues from 11 different species using a combination of targeted PFAS analysis, EOF and total fluorine determination, and suspect screening. Samples were obtained from the east coast United States (US), west and east coast of Greenland, Iceland, and Sweden from 2000 to 2017. Of the 36 target PFASs, perfluorooctane sulfonate (PFOS) dominated in all but one Icelandic and three US samples, where the 7:3 fluorotelomer carboxylic acid (7:3 FTCA) was prevalent. This is the first report of 7:3 FTCA in polar bears (∼1000 ng/g, ww) and cetaceans (<6-190 ng/g, ww). In 18 out of 25 samples, EOF was not significantly greater than fluorine concentrations derived from sum target PFASs. For the remaining 7 samples (mostly from the US east coast), 30-75% of the EOF was unidentified. Suspect screening revealed an additional 37 PFASs (not included in the targeted analysis) bringing the total to 63 detected PFASs from 12 different classes. Overall, these results highlight the importance of a multiplatform approach for accurately characterizing PFAS exposure in marine mammals.

Fluorine Mass Balance and Suspect Screening in Marine Mammals from the Northern Hemisphere

There is increasing evidence that the ∼20 routinely monitored perfluoroalkyl and polyfluoroalkyl substances (PFASs) account for only a fraction of extractable organofluorine (EOF) occurring in the environment. To assess whether PFAS exposure is being underestimated in marine mammals from the Northern Hemisphere, we performed a fluorine mass balance on liver tissues from 11 different species using a combination of targeted PFAS analysis, EOF and total fluorine determination, and suspect screening. Samples were obtained from the east coast United States (US), west and east coast of Greenland, Iceland, and Sweden from 2000 to 2017. Of the 36 target PFASs, perfluorooctane sulfonate (PFOS) dominated in all but one Icelandic and three US samples, where the 7:3 fluorotelomer carboxylic acid (7:3 FTCA) was prevalent. This is the first report of 7:3 FTCA in polar bears (∼1000 ng/g, ww) and cetaceans (<6-190 ng/g, ww). In 18 out of 25 samples, EOF was not significantly greater than fluorine concentrations derived from sum target PFASs. For the remaining 7 samples (mostly from the US east coast), 30-75% of the EOF was unidentified. Suspect screening revealed an additional 37 PFASs (not included in the targeted analysis) bringing the total to 63 detected PFASs from 12 different classes. Overall, these results highlight the importance of a multiplatform approach for accurately characterizing PFAS exposure in marine mammals.

Transplacental Transfer of Per- and Polyfluoroalkyl Substances Identified in Paired Maternal and Cord Sera Using Suspect and Nontarget Screening

Novel per- and polyfluoroalkyl substances (PFASs) in various environmental media have attracted increasing attention; however, the information regarding PFASs exposure in pregnant women and fetuses is insufficient. In this study, we built and applied suspect and nontarget screening strategies based on the mass difference of the CF₂, CF₂O, and CH₂CF₂ units to select potential novel PFASs from 117 paired maternal and cord sera. In total, 10 legacy PFASs and 19 novel PFASs from 10 classes were identified to be above confidence levels 3, among which 14 were not previously reported in human serum. Novel PFASs accounted for a considerable percentage of total PFASs in pregnant women and can be transferred to fetuses at non-negligible concentrations (i.e., 27.9% and 30.3% of total PFAS intensities in maternal and cord sera, respectively). The transplacental transfer efficiency (TTE) of PFASs showed a U-shape trend in the series of perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonic acids, and unsaturated perfluorinated alcohols. The TTE of novel PFASs is suggested to be structure-dependent, based on a flexible docking experiment. This study provides comprehensive TTE information on legacy and novel PFASs for the first time, and additional toxicity studies are needed to evaluate the risk of novel PFASs further.

Nontarget Discovery of Per- and Polyfluoroalkyl Substances in Atmospheric Particulate Matter and Gaseous Phase Using Cryogenic Air Sampler

Novel per- and polyfluoroalkyl substances (PFASs) have become a key issue in global environmental studies. Although several novel PFASs have been discovered in atmospheric particulate matter through nontarget analysis, information on the environmental occurrence of novel PFASs in atmospheric gaseous phases and conventional sampling techniques is somewhat deficient. Therefore, this Article describes a new type of air sampler, the cryogenic air sampler (CAS), which was used to collect all atmospheric components simultaneously. Nontarget analysis then was performed through PFASs homologue analysis. A total of 117 PFAS homologues (38 classes) were discovered, 48 of which (13 classes) were identified with confidence Level 4 or above. Eleven chlorinated perfluoropolyether alcohols (3 classes) and four chlorinated perfluoropolyether carboxylic acids (2 classes) have been reported for the first time in this Article. This Article is also the first report of 12 hydrosubstituted perfluoroalkyl carboxylates (H-PFCAs) in the atmosphere. H-PFCAs and chlorinated perfluoropolyether carboxylic acids were mainly distributed in the particular phase. These results are evidence that novel chlorinated polyether PFASs should be the focus of future study.

A framework to model exposure to per- and polyfluoroalkyl substances in indoor environments

Per- and polyfluoroalkyl substances (PFAS) include a wide range of halogenated chemicals, which have been used as water- and stain-resistant coatings for consumer products and industrial purposes. PFAS are persistent in the environment and several are bioaccumulative, and thus relevant for human and environmental health. Given their pervasiveness, we need to understand how we are exposed to PFAS, especially in indoor environments where many people spend most of their time. Research on indoor exposure to semivolatile organic compounds (SVOCs) has progressed rapidly in recent years. Because many PFAS can be considered SVOCs, much of what has been learned about SVOCs may be used to guide research on PFAS exposure in indoor environments. Here, we briefly review what has been done to assess indoor exposure to PFAS. Then, we propose a systematic indoor exposure framework for PFAS based on methods to estimate exposure to SVOCs. We illustrate how critical parameters such as partition coefficients for different media (particles, dust, surfaces, and clothing) for different types of PFAS could be measured, how these measurements can be used in exposure models for PFAS, and how fundamental, predictive relationships might be used to estimate necessary parameters for emerging compounds.