Per- and polyfluoroalkyl substances (PFAS) are common contaminants of drinking water globally. Due to their large number and diversity, extractable organofluorine (EOF) has been employed as a sum parameter measurement to capture known and unknown PFAS in environmental samples. However, current methods for determining drinking water EOF perform poorly for trifluoroacetic acid (TFA) and provide limited insights into the nature of unidentified fluorine occurring in samples. To address this, we developed and validated a solid-phase extraction procedure for EOF determination in drinking water with improved TFA recovery, which removes and/or accounts for different species of inorganic fluorine. The method produces two fractions: one containing mostly polar fluorinated substances (e.g., TFA, tetrafluoroborate, and trifluoromethanesulfonate) and another containing longer-chain PFAS. Hexafluorophosphate was distributed across both fractions. Application of the method to Stockholm drinking water revealed a closed fluorine mass balance in fraction I, predominantly (93%) consisting of TFA. In fraction II, however, 67% of the fluorine was unidentified, pointing to unknown fluorinated substance(s) with similar physical-chemical properties to PFAS in this fraction (e.g., perfluorooctanesulfonate). In addition to providing clues for identifying EOF, the method improves estimation of “PFAS Total” for comparison to limits under the European Drinking Water Directive.

Per- and polyfluoroalkyl substances (PFAS) have been detected worldwide, from the deep seas to polar regions. A previous review showed that PFAS are risk drivers of the chemical mixture present in human blood. This study focused on establishing the PFAS exposure of a Swedish subpopulation and investigated whether the exposure poses a risk of adverse health effects. Human serum from 60 blood donors in Stockholm, Sweden, was analyzed. A target method including 32 PFAS analytes and over 270 suspect features was used to detect and quantify PFAS. Twenty-six PFAS were quantified, and 7 suspect PFAS features (6 H-PFCAs and PFECHS) were semi-quantified. Nine mixture risk assessment (MRA) strategies were used to assess the risk of health outcomes. Fifteen effect levels were derived and used, along with 15 already established values. The certainty of various derivation techniques was discussed. The MRAs showed that the entire studied population exceeded some of the risk thresholds, with effects including high cholesterol and immune suppression. However, the certainty was lower when deriving these two effect levels. The MRA, using human biomonitoring guidance values (high certainty), concluded that for 63 % of the individuals, a risk for adverse health effects cannot be excluded. This study has demonstrated that there is a reason for concern regarding PFAS exposure in the general population of Sweden. To our knowledge, this is the first time the H-PFCAs have been semi-quantified in human blood using a reference standard.

Global warming increases the vegetation cover and leads to shifts in vegetation types in the Arctic. An increase in the vegetation cover might substantially enhance carbon dioxide (CO₂) emissions from northern permafrost soils, since root exudation of labile carbon and nitrogen can stimulate soil organic matter (SOM) decomposition via the rhizosphere priming effect. The current understanding of Arctic rhizosphere priming largely rests on soil incubation studies that simulate root exudation by adding various organic substrates in varying concentrations to soils. How the specific exudates of different plants influence rhizosphere priming is unclear as Arctic plant root exudate release rates and composition are largely unknown. Using targeted and non-targeted liquid chromatography–mass spectrometry, we compared the exudate composition and exudation rates of total organic carbon, 7 organic acids, 14 amino acids and 9 carbohydrates from three abundant and functionally different tundra plants (Betula glandulosa, Alnus viridis and Eriophorum vaginatum). While organic carbon and primary metabolites exudation were similar among the studied plants despite their different nitrogen acquisition strategies, distinct differences between the plant species were found in the overall root exudate composition. Between 80 and 94 % of the root exudate metabolome was not shared among the three plants. Our findings indicate that a change in vegetation types across the Arctic will primarily alter the release of secondary plant metabolites into the soil and thereby could alter soil microbial processes. Our observations further suggest that previous laboratory experiments studying priming frequently oversaturated microorganisms with labile substrates compared to natural conditions; this highlights the need for more realistic priming studies. Our data on root exudation provide critical background information for improving laboratory experiments.

Most known per- and polyfluoroalkyl substances (PFAS) bioaccumulate by binding to proteins or partitioning to phospholipids, leading to their prevalence in liver and blood. However, the recent discovery of high concentrations of unidentified extractable organofluorine (EOF) in the blubber of a killer whale (Orcinus orca) from Greenland suggests that some fluorinated substances preferentially bioaccumulate in storage lipids. To further investigate this, the present work examined blubber from 4 killer whales (3 from Greenland, 1 from Sweden) via gas chromatography-atmospheric pressure chemical ionization-ion mobility mass spectrometry. Using collision cross sections, we prioritized features suspected to be highly fluorinated and then selected 5 for manual annotation. Custom synthesized standards confirmed 10:2 and 12:2 fluorotelomer methylsulfone, 10:2 and 12:2 fluorotelomer chloromethylsulfone, and 6:2 bisfluorotelomer sulfone in all blubber samples from Greenland at concentrations ranging from <0.4 to 72.5 ng/g, explaining 34–75% of blubber EOF, but none in the Swedish sample. None of these substances were observable in liver, suggesting preferential accumulation in storage lipids. To the best of our knowledge, this is the first report of neutral fluorotelomer sulfones in wildlife and the first identification of lipophilic, highly fluorinated PFAS.

Per- and polyfluoroalkyl substance (PFAS)-contaminated drinking water has been a significant source of human exposure to PFAS in Uppsala, Sweden. Herein, we investigated temporal trends of PFAS in serum samples collected three weeks after delivery from first-time mothers in Uppsala (1996–2022; n = 869), to determine whether efforts to remediate drinking water contamination have reduced maternal PFAS exposure. In addition, the impact of fish/seafood consumption as an exposure source was evaluated. PFAS were analysed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and temporal trends were evaluated using adjusted cubic spline models.

Linear (lin) and branched (br) perfluorooctane sulfonate (PFOS) and perfluoroctanoate (PFOA) showed declining temporal trends, likely due to international regulation and phase-out initiatives. Later initiatives to restrict use and emissions of perfluorononanoate (PFNA), perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnDA) likely explained the initial increased concentrations by 3–7% per year, up to 2007 or 2010, followed by decreasing trends, on average 2–3% per year. Drinking water contamination was likely responsible for the increase in serum br and lin perfluorohexanesulfonate (PFHxS) concentrations early in the study period, followed by a decline over the last decade associated with remediation of the drinking water contamination around 2012. However, even after remediation, drinking water appeared to contribute to perfluoropentanesulfonate (PFPeS) and PFHxS. Fish/seafood consumption was significantly associated with serum levels of lin PFOS, PFNA, PFDA, and PFUnDA.

Overall, PFAS exposure among first-time mothers in Uppsala has declined, resulting in a marked reduction in the proportion of mothers exceeding the serum reference value established by the European Food Safety Authority. Nevertheless, 54% of the mothers sampled from 2018 to 2022 still exceeded this level, showing that efforts to reduce PFAS exposure must continue for many years to come.

The unique properties of per- and polyfluoroalkyl substances (PFAS) have led to their extensive use in consumer products, including ski wax. Based on the risks associated with PFAS, and to align with PFAS regulations, the international ski federation (FIS) implemented a ban on products containing “C8 fluorocarbons/perfluorooctanoate (PFOA)” at all FIS events from the 2021/2022 season, leading manufactures to shift their formulations towards short-chain PFAS chemistries. To date, most studies characterising PFAS in ski waxes have measured a suite of individual substances using targeted analytical approaches. However, the fraction of total fluorine (TF) in the wax accounted for by these substances remains unclear. In this study, we sought to address this question by applying a multi-platform, fluorine mass balance approach to a total of 10 commercially available ski wax products. Analysis of TF by combustion ion chromatography (CIC) revealed concentrations of 1040–51700 μg F g−1 for the different fluorinated waxes. In comparison, extractable organic fluorine (EOF) determined in methanol extracts by CIC (and later confirmed by inductively-coupled plasma-mass spectrometry and 19F- nuclear magnetic resonance spectroscopy) ranged from 92 to 3160 μg g−1, accounting for only 3–8.8 % of total fluorine (TF). Further characterisation of extracts by cyclic ion mobility-mass spectrometry (IMS) revealed 15 individual PFAS with perfluoroalkyl carboxylic acid concentrations up to 33 μg F g−1, and 3 products exceeding the regulatory limit for PFOA (0.025 μg g−1) by a factor of up to 100. The sum of all PFAS accounted for only 0.01–1.0 % of EOF, implying a high percentage of unidentified PFAS, thus, pyrolysis gas chromatography-mass spectrometry was used to provide evidence of the nature of the non-extractable fluorine present in the ski wax products.

High-resolution mass spectrometry (HRMS)-based suspect and nontarget screening has identified a growing number of novel per- and polyfluoroalkyl substances (PFASs) in the environment. However, without analytical standards, the fraction of overall PFAS exposure accounted for by these suspects remains ambiguous. Fortunately, recent developments in ionization efficiency (IE) prediction using machine learning offer the possibility to quantify suspects lacking analytical standards. In the present work, a gradient boosted tree-based model for predicting log IE in negative mode was trained and then validated using 33 PFAS standards. The root-mean-square errors were 0.79 (for the entire test set) and 0.29 (for the 7 PFASs in the test set) log IE units. Thereafter, the model was applied to samples of liver from pilot whales (n = 5; East Greenland) and white beaked dolphins (n = 5, West Greenland; n = 3, Sweden) which contained a significant fraction (up to 70%) of unidentified organofluorine and 35 unquantified suspect PFASs (confidence level 2–4). IE-based quantification reduced the fraction of unidentified extractable organofluorine to 0–27%, demonstrating the utility of the method for closing the fluorine mass balance in the absence of analytical standards.

A growing number of studies have reported that routinely monitored per- and polyfluoroalkyl substances (PFAS) are not sufficient to explain the extractable organic fluorine (EOF) measured in human blood. In this study, we address this gap by screening pooled human serum collected over 3 decades (1986-2015) in Tromsø (Norway) for >5000 PFAS and >300 fluorinated pharmaceuticals. We combined multiple analytical techniques (direct infusion Fourier transform ion cyclotron resonance mass spectrometry, liquid chromatography-Orbitrap-high-resolution mass spectrometry, and total oxidizable precursors assay) in a three-step suspect screening process which aimed at unequivocal suspect identification. This approach uncovered the presence of one PFAS and eight fluorinated pharmaceuticals (including some metabolites) in human serum. While the PFAS suspect only accounted for 2-4% of the EOF, fluorinated pharmaceuticals accounted for 0-63% of the EOF, and their contribution increased in recent years. Although fluorinated pharmaceuticals often contain only 1-3 fluorine atoms, our results indicate that they can contribute significantly to the EOF. Indeed, the contribution from fluorinated pharmaceuticals allowed us to close the organofluorine mass balance in pooled serum from 2015, indicating a good understanding of organofluorine compounds in humans. However, a portion of the EOF in human serum from 1986 and 2007 still remained unexplained.

Nontargeted screening (NTS) utilizing liquid chromatography electrospray ionization high-resolution mass spectrometry (LC/ESI/HRMS) is increasingly used to identify environmental contaminants. Major differences in the ionization efficiency of compounds in ESI/HRMS result in widely varying responses and complicate quantitative analysis. Despite an increasing number of methods for quantification without authentic standards in NTS, the approaches are evaluated on limited and diverse data sets with varying chemical coverage collected on different instruments, complicating an unbiased comparison. In this interlaboratory comparison, organized by the NORMAN Network, we evaluated the accuracy and performance variability of five quantification approaches across 41 NTS methods from 37 laboratories. Three approaches are based on surrogate standard quantification (parent-transformation product, structurally similar or close eluting) and two on predicted ionization efficiencies (RandFor-IE and MLR-IE). Shortly, HPLC grade water, tap water, and surface water spiked with 45 compounds at 2 concentration levels were analyzed together with 41 calibrants at 6 known concentrations by the laboratories using in-house NTS workflows. The accuracy of the approaches was evaluated by comparing the estimated and spiked concentrations across quantification approaches, instrumentation, and laboratories. The RandFor-IE approach performed best with a reported mean prediction error of 15× and over 83% of compounds quantified within 10× error. Despite different instrumentation and workflows, the performance was stable across laboratories and did not depend on the complexity of water matrices.

The large number and diversity of organohalogen compounds(OHCs)occurring in the environment poses a grand challenge to analyticalchemists. Since no single targeted method can identify and quantifyall OHCs, the size of the OHC iceberg may be underestimated.We sought to address this problem in municipal wastewater treatmentplant (WWTP) sludge by quantifying the unidentified fraction of theOHC iceberg using targeted analyses of major OHCs together with measurementsof total and extractable (organo)halogen (TX and EOX, respectively;where X = F, Cl, or Br). In addition to extensive method validationvia spike/recovery and combustion efficiency experiments, TX and/orEOX were determined in reference materials (BCR-461 and NIST SRMs2585 and 2781) for the first time. Application of the method to WWTPsludge revealed that chlorinated paraffins (CPs) accounted for most(similar to 92%) of the EOCl, while brominated flame retardants and per-and polyfluoroalkyl substances (PFAS) accounted for only 54% of theEOBr and 2% of the EOF, respectively. Moreover, unidentified EOF innonpolar CP extracts points to the existence of organofluorine(s)with physical-chemical properties unlike those of target PFAS.This study represents the first multihalogen mass balance in WWTPsludge and offers a novel approach to prioritization of sample extractsfor follow-up investigation. A multihalogenmass balance experiment in WWTP sludge revealedhigh levels of unidentified organofluorine and organobromine. Organochlorinewas characterized mainly by chlorinated paraffins.