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.

Endocrine disruptors (EDs) pose a serious threat to human health and the environment and require a comprehensive evaluation to be identified. The identification of EDs require a substantial amount of data, both in vitro and in vivo, due to the current scientific criteria in the EU. At the same time, the EU strives to reduce animal testing due to concerns regarding animal welfare and sensitivity of animal studies to adequately detect adverse effects relevant for human health. Perfluorooctane sulfonic acid (PFOS) is a persistent organic pollutant that is suspected to be an ED based on academic research, however it is not identified as such from a regulatory perspective. It has previously been shown that PFOS has the potential to cause neurotoxicity as well as affect the thyroid system, and it is known that specific thyroid hormone levels are critical in the development of the brain during. In this work, the aim was to evaluate a mechanism-based approach to identify ED properties of PFOS based on the Adverse Outcome Pathway (AOP) framework and using New Approach Methods (NAMs), by comparing this approach to an ED assessment based on the currently available guidance document. An AOP network (AOPN) was generated for the thyroid modality, and AOPs leading to developmental neurotoxicity (DNT) were identified. A literature search and screening process based on the AOPN, and systematic review methodology, was performed, followed by a rigorous Weight-of-Evidence (WoE) assessment. Evidence was mapped back onto the AOPN used for the literature search, to identify possible endocrine Modes-of-Action (MoAs) for PFOS and data gaps in the two assessments. It could be concluded that PFOS fulfils the criteria for ED classification in the standard ED assessment, but not in the mechanism-based assessment. The need for quantitative information, such as quantitative AOPs, for the mechanism-based approach is discussed. The possibility of a directly neurotoxic alternative MoA was also highlighted based on available in vitro data. Opportunities and challenges with implementing AOPs and NAMs into the regulatory assessment of EDs, and assessing hazard in the Next Generation Risk Assessment, is discussed. This case study exploring the mechanism-based approach to ED identification represents an important step toward more accurate and predictive assessment of EDs based on AOPs and NAMs, and to the Next Generation Risk Assessment (NGRA) concept.

Identification of stereo- and positional isomers detected with high-resolution mass spectrometry (HRMS) is often challenging due to near-identical fragmentation spectra (MS2), similar retention times, and collision cross-section values (CCS). Here we address this challenge on the example of hydroxylated polychlorinated biphenyls (OH-PCBs) with the aim to (1) distinguish between isomers of OH-PCBs using two-dimensional ion mobility spectrometry (2D-IMS) and (2) investigate the structure of the fragments of OH-PCBs and their fragmentation mechanisms by ion mobility spectrometry coupled to high-resolution mass spectrometry (IMS-HRMS). The MS2 spectra as well as CCS values of the deprotonated molecule and fragment ions were measured for 18 OH-PCBs using flow injections coupled to a cyclic IMS-HRMS. The MS2 spectra as well as the CCS values of the parent and fragment ions were similar between parent compound isomers; however, ion mobility separation of the fragment ions is hinting at the formation of isomeric fragments. Different parent compound isomers also yielded different numbers of isomeric fragment mobilogram peaks giving new insights into the fragmentation of these compounds and indicating new possibilities for identification. For spectral interpretation, Gibbs free energies and CCS values for the fragment ions of 4 '-OH-CB35, 4 '-OH-CB79, 2-OH-CB77 and 4-OH-CB107 were calculated and enabled assignment of structures to the isomeric mobilogram peaks of [M-H-HCl](-) fragments. Finally, further fragmentation of the isomeric fragments revealed different fragmentation pathways depending on the isomeric fragment ions.

The number of chemicals in the anthroposphere is increasing and some of them end up in humans. A literature search was made to assess which anthropogenic organic contaminants (OCs) that have been analysed in blood from the general population. The reviewed articles were used to create a database of studies [human blood database (HBDB), containing 559 OCs] reporting blood analyses made worldwide. All studies analysing blood from the Swedish population were compiled into a second database [Swedish exposure database (SEDB), containing 166 OCs] listing blood concentrations of OCs. Data from the SEDB showed decreasing levels of regulated chemicals in blood over time, indicating that regulation had made an impact. The Hazard Index (HI) approach was used as a qualitative mixture risk assessment of the OCs with established human biomonitoring guidance values (HBM-GVs) and blood levels in the SEDB. Nine HBM-GVs were found and the HI of the corresponding OCs/groups of OCs showed that a risk of adverse effects in the general population could not be excluded, which is a cause for concern considering that only a fraction of the analysed OCs in the SEDB were included. This study presents the OCs identified in human blood and concentration time trends. The study highlights the lack of HBM-GVs needed for mixture risk assessments to assess the combined risk of chemical exposure to the general population. 

Indoor environmental pollutants are a threat to human health. In the current study, we analysed 25 per- and polyfluoroalkyl substances (PFASs) in seven different size fraction of house dust including the two relevant for exposure via ingestion and inhalation. The highest PFAS concentration is found in the inhalable particulate fraction which is explained by the increased surface area as the particulate's sizes decrease. The estimated daily intake (EDI) of the individual PFAS and exposure pathways were calculated for children and adults. In addition, the total EDI for PFOA and its precursors was estimated. The polyfluoroalkyl phosphoric acid diesters (diPAP), followed by PFOA and PFHxA fluortelomer, showed the highest concentrations of PFAS analysed. The cumulative EDI of PFAS for children was 3.0 ng/kg bw per day, a worst-case scenario, which is 17 times higher than the calculated EDI for adults. For children, ingestion of dust was found to result in 800 times higher PFOA exposure than via inhalation. The contribution from PFOA precursors corresponded to only 1% of the EDI from dust indicating PFOA as the main source of exposure. The EDI's of PFOA and PFOS from dust were lower than the calculated EDI's from food ingestion reported by the Swedish Food Agency. Our data indicate that the EDI for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS from dust intake alone is close to the established tolerable weakly intake of 4.4 ng/kg bw in children, set by European Food Safety Authority (EFSA) in 2020. The combined EDI levels PFOA and PFOS from both dust and food exceeded the EFSA TWI for both children and adults. This study demonstrates that dust is a relevant exposure pathway for PFAS intake and that analysis of relevant particle size fractions is important for evaluation of dust as an exposure pathway.

Hydroxylated PCBs are an important class of metabolites of the widely distributed environmental contaminants polychlorinated biphenyls (PCBs). However, the absence of authentic standards is often a limitation when subject to detection, identification, and quantification. Recently, new strategies to quantify compounds detected with non-targeted LC/ESI/HRMS based on predicted ionization efficiency values have emerged. Here, we evaluate the impact of chemical space coverage and sample matrix on the accuracy of ionization efficiency-based quantification. We show that extending the chemical space of interest is crucial in improving the performance of quantification. Therefore, we extend the ionization efficiency-based quantification approach to hydroxylated PCBs in serum samples with a retraining approach that involves 14 OH-PCBs and validate it with an additional four OH-PCBs. The predicted and measured ionization efficiency values of the OH-PCBs agreed within the mean error of 2.1 × and enabled quantification with the mean error of 4.4 × or better. We observed that the error mostly arose from the ionization efficiency predictions and the impact of matrix effects was of less importance, varying from 37 to 165%. The results show that there is potential for predictive machine learning models for quantification even in very complex matrices such as serum. Further, retraining the already developed models provides a timely and cost-effective solution for extending the chemical space of the application area.

To make outdoor clothing water- or dirt-repellent, durable water-repellent (DWR) coatings based on side-chain fluorinated polymers (SFPs) are used. During use of outdoor clothing, per- and polyfluoroalkyl substances (PFASs) can be emitted from the DWR to the environment. In this study, the effects of aging, washing, and tumble drying on the concentration of extractable PFASs in the DWR of perfluorohexane-based short-chain SFPs (FC-6 chemistry) and of perfluorooctane-based long-chain SFPs (FC-8 chemistry) were assessed. For this purpose, polyamide (PA) and polyester (PES) fabrics were coated with FC-6- and FC-8-based DWRs. Results show that aging of the coated fabrics causes an increase in concentration and formation of perfluoroalkyl acids (PFAAs). The effect of aging on the volatile PFASs depends on the type of fabric. Washing causes a decrease in PFAA concentrations, and in general, volatile PFASs are partly washed out of the textiles. However, washing can also increase the extractable concentration of volatile PFASs in the fabrics. This effect becomes stronger by a combination of aging and washing. Tumble drying does not affect the PFAS concentrations in textiles. In conclusion, aging and washing of fabrics coated with the DWR based on SFPs release PFASs to the environment.

Data on toxic effects are at large missing the prevailing understanding of the risks of industrial chemicals. Thyroid hormone (TH) system disruption includes interferences of the life cycle of the thyroid hormones and may occur in various organs. In the current study, high-throughput screening data available for 14 putative molecular initiating events of adverse outcome pathways, related to disruption of the TH system, were used to develop 19 in silico models for identification of potential thyroid hormone system-disrupting chemicals. The conformal prediction framework with the underlying Random Forest was used as a wrapper for the models allowing for setting the desired confidence level and controlling the error rate of predictions. The trained models were then applied to two different databases: (i) an in-house database comprising xenobiotics identified in human blood and ii) currently used chemicals registered in the Swedish Product Register, which have been predicted to have a high exposure index to consumers. The application of these models showed that among currently used chemicals, fewer were overall predicted as active compared to chemicals identified in human blood. Chemicals of specific concern for TH disruption were identified from both databases based on their predicted activity.

Per- and polyfluoroalkyl substances (PFASs) are used in a wide range of products and have been found ubiquitously in our indoor environment, and there is evidence that exposure to PFAS can lead to adverse endocrine effects, such as thyroid hormone disruption. Pet cats have a high dust intake due to their grooming behavior and have been shown to be a suitable sentinel species for assessment of toddler's exposure. Here we used paired household dust (n=46) and cat serum (n=27) samples to establish whether dust is a relevant exposure pathway to PFASs. An analytical method for PFAS analysis was optimized using a low volume of cat serum samples, combining solid-phase extraction and online sample cleanup. Dust was extracted with methanol by sonication and cleaned up by addition of active carbon. In total, 27 PFASs were analyzed by liquid chromatography/mass spectrometry analysis. The correlation between PFAS levels in dust and serum, serum lipids and thyroid hormone levels, and PFAS levels in dust between different rooms were statistically evaluated. PFOS and PFDA could be quantified in all cat serum samples (median 2300 pg/mL and 430 pg/mL, respectively), followed by PFOA (median 1100 pg/mL), quantified in 96% of the samples. The levels of 6:2 and 8:2 diPAPs were determined in 65% and 92% of the serum samples, respectively, and were an order of magnitude lower (1.4-160 pg/mL). Household dust on the other hand was dominated by 6:2 and 8:2 diPAPs, with a median of 65 ng/g dust and 49 ng/g dust, respectively. PFOS (median 13 ng/g dust) and PFOA (median 9 ng/g dust) were quantified in 93% of the dust samples. Only eight PFASs were detected (>LOD) in at least 50% of the samples of both matrices and could be paired. Significant correlations between cat serum and dust were found for PFOA (r(S)=0.32, p<0.049) and PFUnDA (r(S)=0.55, p<0.001). Significant positive correlations were found between serum total thyroxine (r(S)=0.11, p<0.05) and PFNA and between serum cholesterol and PFHpA (r(S)=0.46, p<0.01), PFUnDA (r(S)=0.40, p<0.05), PFDoDA (r(S)=0.44, p<0.01), and sum PFAS (r(S)=0.48, p<0.01). In conclusion, this study confirmed that dust is a relevant exposure pathway for the ingestion of some PFASs for cats, and the serum levels of PFASs could be of relevance for the cat's health.

Carbamazepine (CBZ) is an anticonvulsant medication with highly persistent properties in the aquatic environment, where it has the potential to affect nontarget biota. Because CBZ and many other pharmaceuticals are not readily removed in conventional sewage treatment plants (STP), additional STP effluent treatment technologies are being evaluated and implemented. Whole effluent ozonation is a prospective method to remove pharmaceuticals such as CBZ, yet knowledge on the toxicity of CBZ ozonation byproducts (OBPs) is lacking. This study presents, for the first time, in vivo individual and mixture toxicity of four putative OBPs, that is, carbamazepine 10,11-epoxide, 10,11-Dihydrocarbamazepine, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM), and 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD) in developing zebrafish (Danio rerio) embryos. BQM and BQD were isolated from the ozonated solution as they were not commercially available. The study confirmed that the OBP mixture caused embryotoxic responses comparable to that of ozonated CBZ. Individual compound embryotoxicity assessment further revealed that BQM and BQD were the drivers of embryotoxicity. OBP chemical stability in ozonated CBZ water solution during 2 week dark storage at 22 degrees C was also assessed. The OBP concentrations remained over time, except for BQD which decreased by 94%. Meanwhile, ozonated CBZ persistently induced embryotoxicity over 2 week storage, potentially illustrating environmental concern.