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.

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.

Of the thousands of per- and polyfluoroalkyl substances (PFAS) known to exist, only a small fraction (≤1%) are commonly monitored in humans. This discrepancy has led to concerns that human exposure may be underestimated. Here, we address this problem by applying a comprehensive fluorine mass balance (FMB) approach, including total fluorine (TF), extractable organic fluorine (EOF), total oxidizable precursors (TOP), and selected target PFAS, to human serum samples collected over a period of 28 years (1986, 2007, and 2015) in Tromsø, Norway. While concentrations of TF did not change between sampling years, EOF was significantly higher in 1986 compared to 2007 and 2015. The ∑₁₂PFAS concentrations were highest in 2007 compared to 1986 and 2015, and unidentified EOF (UEOF) decreased from 1986 (46%) to 2007 (10%) and then increased in 2015 (37%). While TF and EOF were not influenced by sex, women had higher UEOF compared to men, opposite to target PFAS. This is the first FMB in human serum to include TOP, and it suggests that precursors with >4 perfluorinated carbon atoms make a minor contribution to EOF (0–4%). Additional tools are therefore needed to identify substances contributing to the UEOF in human serum.

Temporal and spatial trends of 15 per- and polyfluoroalkyl substances (PFAS) were determined in white-tailed sea eagle (WTSE) eggs (Haliaeetus albicilla) from two inland and two coastal regions of Sweden between 1969 and 2021. PFAS concentrations generally increased from ∼1969 to ∼1990s–2010 (depending on target and site) and thereafter plateaued or declined, with perfluorooctane sulfonamide (FOSA) and perfluorooctane sulfonate (PFOS) declining faster than most perfluoroalkyl carboxylic acids (PFCAs). The net result was a shift in the PFAS profile from PFOS-dominant in 1969–2010 to an increased prevalence of PFCAs over the last decade. Further, during the entire period higher PFAS concentrations were generally observed in coastal populations, possibly due to differences in diet and/or proximity to more densely populated areas. Fluorine mass balance determination in pooled samples from three of the regions (2019–2021) indicated that target PFAS accounted for the vast majority (i.e. 81–100%) of extractable organic fluorine (EOF). Nevertheless, high resolution mass-spectrometry-based suspect screening identified 55 suspects (31 at a confidence level [CL] of 1–3 and 24 at a CL of 4–5), of which 43 were substances not included in the targeted analysis. Semi-quantification of CL ≤ 2 suspects increased the identified EOF to >90% in coastal samples. In addition to showing the impact of PFAS regulation and phase-out initiatives, this study demonstrates that most extractable organofluorine in WTSE eggs is made up of known (legacy) PFAS, albeit with low levels of novel substances.

Fluorine mass balance studies have shown that monomeric per- and polyfluoroalkyl substances (PFAS) with perfluoroalkyl chain lengths of ∼5–14 carbon atoms (i.e., “conventional” PFAS) account for a fraction (∼2%) of the extractable organic fluorine (EOF) in municipal wastewater treatment plant (WWTP) sludge. The identity of the remaining EOF has thus far been unclear but may be partly attributable to fluorine-containing pharmaceuticals and pesticides used throughout society. To test this hypothesis, we applied high resolution mass spectrometry-based suspect screening to samples of municipal WWTP sludge which had been previously subjected to a fluorine mass balance. Sixteen pharmaceutical substances (including transformation products [TPs]), one pesticide, and thirteen conventional PFAS were confirmed at confidence levels 1–4 and (semi)quantified, revealing concentrations ranging from 0.07 to 155 ng/g dw. Notably, eight pharmaceutical substances did not meet the OECD definition of PFAS. When converted to fluorine equivalents, the newly detected organofluorine substances increased the percentage of known EOF from ∼2% to ∼27%, of which ∼22% was attributed to pharmaceutical and pesticide substances, with the greatest contributions from ticagrelor TP (4.0%), ezetimibe (3.9%), and bicalutamide (3.5%). These data highlight the importance of considering both unconventional and non-PFAS organofluorine substances in addition to conventional PFAS when closing the organofluorine mass balance in WWTP sludge.