Non-targeted metabolomics and associations with per- and polyfluoroalkyl substances (PFAS) exposure in humans: A scoping review

Neurotoxic effects of per- and polyfluoroalkyl substances (PFAS) mixture exposure in mice: Accumulations in brain and associated changes of behaviors, metabolome, and transcriptome

Humans are exposed to complex per- and polyfluoroalkyl substances (PFAS) mixtures, yet their neurotoxicity and mechanisms remains unclear. This study exposed male mice to 17 PFAS mixtures at low levels (0.2-20 µg/L) for 49 days via drinking water. Perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), 6:2 fluorotelomer sulfonic acid (6:2 FTS), and perfluorooctane Sulfonate (PFOS) accumulated in brain tissues, with brain/plasma ratios of 2.03-5.87, 2.94-12.88, 1.90-3.19, and 0.62-0.93, respectively. Electroencephalogram (EEG) results showed significant alterations, including a reduction in beta spectral edge (21.47-13.85 Hz) and an increase in gamma spectral edge (57.64-79.07 Hz). Histopathological analysis revealed necrosis in the hippocampus, contributing to the observed anxiety-like behaviors and memory impairments in exposed mice. Plasma metabolomics highlighted disrupted osmoprotectants, impaired glutamatergic synapse function, and tryptophan metabolism. Brain metabolomics demonstrated suppression of purine metabolism and activation of arachidonic acid metabolism, suggesting involvement in neurotoxic effects. Transcriptomic profiling further identified dysregulation in neuroactive ligand-receptor interactions, cholinergic and GABAergic synapses, and calcium signaling pathways, with oxytocin signaling highlighted as a critical mechanism. This study, for the first time, links PFAS mixture to neurotoxicity via neurotransmitter-related pathways, underscoring the need for public health policies and preventive strategies to mitigate PFAS exposure risks.

Celecoxib as a potential treatment for hepatocellular carcinoma in populations exposed to high PFAS levels

Per- and polyfluoroalkyl substances (PFAS), including perfluorooctane sulfonate and perfluorooctanoic acid, are associated with adverse human effects. However, few studies have assessed the effects of PFAS mixtures on hepatocellular carcinoma (HCC). In this study, we systematically investigated the effects and underlying mechanisms of PFAS mixtures on the proliferation, migration, and invasion of HCC cells (JHH-7 and Li-7) in vitro using a combination of biological techniques and high-coverage untargeted metabolomics. A six day exposure to a 5 μM PFAS mixture significantly enhanced the malignant progression of HCC in vitro. Metabolomic analysis identified the upregulation of prostaglandin E2 (PGE2) as a key factor associated with these effects. This hypothesis was further validated using celecoxib, a PGE2 inhibitor, which reduced PGE2 levels in HCC cells, consequently slowing their migration and invasion. Additionally, mice treated with celecoxib exhibited reduced tumor volumes compared with those treated with PFAS alone. These results suggest that PFAS exposure enhances HCC malignancy through the PI3K/AKT signaling pathway via increased PGE2 production. In conclusion, a 5 μM PFAS mixture accelerates HCC proliferation and invasion; moreover, celecoxib demonstrates potential as a therapeutic agent that inhibits these effects.

Exposure range matters: considering nonlinear associations in the meta-analysis of environmental pollutant exposure using examples of per- and polyfluoroalkyl substances and birth outcomes

Meta-analysis is a powerful analytic method for summarizing effect estimates across studies. However, conventional meta-analysis often assumes a linear exposure-outcome relationship and does not account for variability over the exposure ranges. In this work, we first used simulation techniques to illustrate that the linear-based meta-analytical approach may result in oversimplistic effect estimation based on 3 plausible nonlinear exposure-outcome curves (S-shape, inverted U-shape, and M-shape). We showed that subgroup meta-analysis that stratifies on exposure levels can investigate nonlinearity and identify the consistency of effect magnitudes in these simulated examples. Next, we examined the heterogeneity of effect estimates across exposure ranges in 2 published linear-based meta-analyses of prenatal exposure to per- and polyfluoroalkyl substances (PFAS) on changes in mean birth weight or risk of preterm birth. The reanalysis found some varying effect sizes and potential heterogeneity when restricting to different PFAS exposure ranges, but findings were sensitive to the cut-off choices used to rank the exposure levels. Finally, we discussed methodological challenges and recommendations for detecting and interpreting potential nonlinear associations in meta-analysis. Using meta-analysis without accounting for exposure range could contribute to literature inconsistency for exposure-induced health effects and impede evidence-based policymaking. Therefore, investigating result heterogeneity by exposure range is recommended. This article is part of a Special Collection on Environmental Epidemiology.

Paternal and Maternal Exposures to Per- and Polyfluoroalkyl Substances and Child Behavioral Difficulties: A Parental Comparison Study

Per- and polyfluoroalkyl substances (PFAS) are widespread environmental pollutants with documented developmental toxicity. Prior research of prenatal PFAS exposure and offspring neurodevelopment did not consider the possible influence from paternal exposure. Using the INUENDO cohort, we studied 334 father-mother-singleton triads enrolled from antenatal clinics in Greenland, Poland, and Ukraine. We measured five PFAS in parental serum samples collected around the 31 weeks of gestation. We assessed child behavioral difficulties at ages 5-9 years by the parent-rated Strength and Difficulties Questionnaire using country- and sex-specific cut-offs (≥90th percentile). We performed analyses stratified by child's sex, coadjusting for maternal or paternal PFAS and other confounders and estimating PFAS mixture effects using quantile g-computation. In male children, multiple maternal PFAS, modeled as individual chemicals or a mixture, were associated with externalizing difficulties. Maternal perfluorononanoic acid (PFNA) was associated with internalizing difficulties in female children. In contrast, paternal exposure to individual PFAS or PFAS mixture was not associated with behavioral difficulties in children of either sex. In summary, maternal prenatal exposure to PFAS, but not paternal PFAS, was associated with mid-childhood behavioral difficulties in a sex-specific manner. Comparing the parent-specific PFAS associations strengthened evidence against confounding shared in the family.

Persistent pollutant exposure impacts metabolomic profiles in polar bears and ringed seals from the High Arctic and Hudson Bay, Canada

Metabolomics measures low molecular weight endogenous metabolites and changes linked to contaminant exposure in biota. However, few studies have explored the relationship between metabolomics and contaminants in Arctic wildlife. We analyzed 239 endogenous metabolites and ∼150 persistent organic pollutants (POPs), including total mercury (THg), in the liver of polar bears and their ringed seal prey harvested from low Canadian Arctic (western Hudson Bay; WHB) and high Arctic (HA) locations during 2015-2016. Polar bears from the HA had different metabolomic profiles compared to those from WHB, particularly in several phosphatidylcholines (PCs), with the HA bears having higher concentrations of longer chain PCs. Similarly, HA and WHB ringed seals also had metabolomic profile differences in five PCs related to fat catabolism and transport. The metabolites with the highest impact on discriminating metabolomic profiles between the two species, based on VIP scores, were: tauroursodeoxycholic Acid (TUDCA), histamine, serotonin, lithocholic acid (LCA), and taurolithocholic acid (TLCA). Higher TUDCA levels in polar bears likely reflect their blubber-rich diet, while higher histamine in seal liver may indicate inflammatory responses. Significant correlations were found between liver metabolites and several per- and polyfluoroalkyl substances (PFAS) in both species, including PFOA, PFNA, PFDA, PFEtCHxS, PFOS, and/or PFDS that moderately correlated to PCs. THg in seals and bears was negatively correlated with sarcosine. This study revealed significant correlations and differences in metabolite profiles of polar bears and ringed seals, suggesting that PFAS impacted several pathways related to lipid metabolism, bile acid synthesis, antioxidant defenses, arginine biosynthesis, histidine metabolism, and sphingolipid metabolism, with ringed seals showing greater sensitivity to PFAS. These results indicate that PFAS may influence metabolic processes in Arctic wildlife, although further research is needed to understand the full impact on Arctic wildlife health.

Critical role of pore size on perfluorooctanoic acid adsorption behaviors in carbonaceous sorbents

Per- and polyfluoroalkyl substances (PFAS) are an emergent threat to the environment due to their toxic, carcinogenic, and environmentally persistent nature. Commonly, these harmful micropollutants are removed from contaminated water sources through adsorption by porous sorbents such as activated carbon. While studies suggest a relationship between sorbent pore size and their PFAS remediation performance, the underlying mechanisms-particularly those related to sorbate morphology-have not been elucidated through direct experimental observations. This work investigates how pore size in carbonaceous sorbents impacts the morphology of adsorbed perfluorooctanoic acid (PFOA) aggregates and their sorption behavior, using microporous and mesoporous carbons as models. Contrast-matching small-angle neutron scattering (CM-SANS) is used to determine the structure of adsorbed PFOA molecules, supported by molecular dynamics simulations and physisorption experiments. Our findings reveal that the larger pore sizes in mesoporous sorbents enable the formation of PFOA assemblies during adsorption, which is hindered in microporous sorbents. Collectively, this work provides direct insights into the adsorption and assembly mechanisms of PFAS molecules within confined pores, offering important insights for the rational design of effective remediation systems.

PFOS-Induced Perturbations in Trophoblast Functions through the Oip5os1/miR-155/Rnd3 Axis in PE

The widespread use of perfluorooctanesulfonic acid (PFOS) has raised concerns regarding its potential on pregnant women, particularly in relation to the development of pre-eclampsia (PE). This study investigates the impact of PFOS exposure on the LncRNA/Rnd3 axis in pregnant mice and its association with trophoblast cell functions in PE. Bioinformatics analysis revealed PFOS-related gene alterations in PE, with pathways enriched in apoptotic signaling and cytokine interactions. Experimental findings showed the downregulation of Oip5os1 and Rnd3, along with the upregulation of miR-155, affecting trophoblast behavior. Animal experiments confirmed that PFOS-induced gene expression changes are linked to PE progression. PFOS exposure impairs trophoblast proliferation and migration via the Oip5os1/miR-155/Rnd3 axis, contributing to PE development.

Applying newly suggested simultaneous analysis of metabolomics and lipidomics into perfluorooctanesulfonate-derived neurotoxicity mechanism in zebrafish embryos

Developing methodologies for performing multi-omics with one sample has been challenging in zebrafish toxicology; however, related studies are lacking. A new strategy for the simultaneous analysis of metabolomics and lipidomics in zebrafish embryos was proposed and applied to explore the neurotoxicity mechanisms of perfluorooctanesulfonate (PFOS). Metabolite and lipid profiled simultaneously with methyl tert-butyl ether (MTBE) were compared with individual results from other extraction solvents. Behavioral alterations were measured after the zebrafish embryos were exposed to 0.1-20 μM PFOS for 5 days. The metabolite-lipid profiles of the MTBE-based strategy analyzed with optimized larval pooling size of 30 were comparable to those of other extraction solvents, indicating the feasibility and efficiency of MTBE-based multi-omics analysis. Many metabolites and lipids, which were enriched more than those previously reported, completed the toxicity pathways involved in energy metabolism and sphingolipids, improving our understanding of PFOS-induced neurotoxicity mechanism manifested by increased movement under dark conditions. Our novel MTBE-based strategy enabled the multi-omics analysis of one sample with minimal use of zebrafish embryos, thereby improving data reliability on changes in multi-layered biomolecules. This study will advance multi-omics technologies that are critical to elucidating the toxicity mechanisms of toxic chemicals including per- and polyfluoroalkyl substances.

Serum metabolome associated with novel and legacy per- and polyfluoroalkyl substances exposure and thyroid cancer risk: A multi-module integrated analysis based on machine learning

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) may linked to thyroid cancer (TC) risk, but inconsistent findings and a lack of studies on mixed exposures exist, especially regarding novel PFAS compounds. Additionally, little is known about the potential mechanisms underlying the association.

OBJECTIVES

Explore the effects of PFAS exposure on the serum metabolome and its correlation with TC.

METHODS

A 1:1 age- and sex-matched case-control study was administered with 746 TC cases and healthy controls. Liquid chromatography-high resolution mass spectrometry determined serum 11 PFAS and untargeted metabolome profile. ENET and LightGBM models were used to explore the exposure patterns and perform variable selection. The mixed exposure effects were assessed using Weighted quantile sum regression and Bayesian kernel machine regression. Metabolome-wide association analyses were performed to assess metabolic dysregulation associated with PFAS, and a structural synthesis analysis was used to detect latent groups of individuals with TC based on PFAS levels and metabolite patterns.

RESULTS

Ten of the 11 PFAS were detected in > 80 % of the population. PFHxA and PFDoA exposure associated with increased TC risk, while PFHxS and PFOA associated with decreased TC risk in single compound models (all P < 0.05). Machine learning algorithms identified PFHxA, PFDoA, PFHxS, PFOA, and PFHpA as the key PFAS influencing the development of TC, and mixed exposures have an overall positive effect on TC risk, with PFHxA making the primary contribution. A novel integrative analysis identified a cluster of TC patients characterized by increased PFHxA, PFDoA, PFHpA and decreased PFOA, PFHxS levels, and altered metabolite patterns highlighted by the upregulation of free fatty acids.

CONCLUSIONS

PFAS exposure is linked to a higher risk of TC, possibly through changes in fatty acid metabolism. Larger, prospective studies are needed to confirm these findings, and the role of short-chain PFAS requires more attention.

Rewiring the nexus between urban traffic pollution-derived polycyclic aromatic hydrocarbon exposure and DNA injury via urinary metabolomics

Urban road traffic environmental stress impacts outdoor population health, with oxidative damage serving as an early indicator of xenobiotic exposure. Polycyclic aromatic hydrocarbons (PAHs) as priority carcinogens pose significant public health burden, yet knowledge remains limited regarding the endogenous metabolic alternations associated with oxidative DNA injury. This cross-sectional study focused on the cohort consisting of 109 sanitation workers ("traffic exposure group") and 112 demographics-matched common residents ("controls") in South China. The goal was to elucidate the occurrence of internal exposure to nine hydroxyl PAHs, and the interrelations with oxidative DNA damage (indicated by 8-hydroxy-2'-deoxyguanosine, 8-OHdG) by linear mixed-effect regression model. T-test and orthogonal partial least squares discriminant analysis were used to determine differential metabolites in non-targeted metabolomics. Results revealed outdoor workers suffered from the heavier PAH exposure burden and exhibited a stronger dose-dependent correlation with 8-OHdG, evidenced by the higher regression coefficient (0.244, 95% CI: 0.154-0.334) than controls (0.203, 95% CI: 0.079-0.328). In total 42 differential endogenous metabolites witnessed significant expression under traffic emission scenario, mainly implicated in phenylalanine, tyrosine and tryptophan biosynthesis. The down-expressed uric acid was the unique metabolite that inversely correlated with the increased intake of ∑8PAH especially in cases. Partially attributed to the traffic-derived PAHs, the dysregulated amino acid, nicotinamide, purine, and steroid hormones metabolic pathways encompassing 11 metabolites were determined as underlying biomarkers in mediating DNA damage. Notably, our findings proposed uric acid may act as a potential antioxidant, as evidenced by the negative correlation with 8-OHdG. The study illustrates outcomes of metabolomics can collaboratively indicate DNA oxidative damage caused by PAHs linked to urban traffic exposure, which holds significant implications for future toxicological research.

Early pregnancy serum PFAS are associated with alterations in the maternal lipidome

Per- and polyfluoroalkyl substances (PFAS) have been detected in the blood of humans and animals worldwide. Exposure to some PFAS are associated with multiple adverse pregnancy outcomes. Existing literature has identified a strong association with PFAS exposure and metabolic dysfunction in humans, including modification of lipid metabolism. Using a subset of the Michigan Mother-Infant Pairs cohort (n = 95), this study investigated associations between first trimester plasma levels of PFAS and maternal lipids and metabolites in the first trimester (T1), at the time of delivery (T3), and in the infant cord blood (CB) using untargeted shotgun lipidomics and metabolomics. Identifying PFAS-induced alterations in the maternal lipid- or metabolome at specific timepoints may help elucidate windows of susceptibility to adverse pregnancy outcomes. Out of 9 PFAS measured, 7 were detected in at least 20% of samples and were used for further analyses. PFOS and PFHxS were measured at the highest concentrations with medians of 5.76 ng/mL and 3.33 ng/mL, respectively. PFOA, PFNA, and PFDA had lower measured values with medians of <1.2 ng/mL. PFHxS concentrations were positively associated with monounsaturated sphingomyelins (SMs) in T1 maternal plasma in adjusted models, determined by an adjusted p-value (q) < 0.1. PFHxS was positively associated with saturated and polyunsaturated SMs and inversely associated with saturated diacylglycerols in T1. Following metabolite-specific analysis, two mono-unsaturated diacylglycerols with carbon chain lengths of 32 and 35 were inversely associated with PFHxS in T1. In T3, only the association between PFHxS and SMs remained, but was attenuated. In addition, PFDA was associated with an increase in polyunsaturated plasmenyl-phosphatidylethanolamines in T3. No associations were identified between PFAS and infant cord blood lipids. Continued research into PFAS associated disruptions in lipid metabolism at sensitive stages of gestation may provide insight into the mechanisms that lead to adverse birth and pregnancy outcomes.

Per- and poly-fluoroalkyl substances (PFAS) accelerate biological aging mediated by increased C-reactive protein

Unhealthy biological aging is related to higher incidence of varied age-related diseases, even higher all-cause mortality. Previous small sample size study suggested that Per- and poly-fluoroalkyl substances (PFAS) was associated with biological aging, but the evidence of exposure-response relationships, potential effect modifiers, and potential mediators were not investigated. Therefore, we conducted a cross-sectional analysis of national study including 14, 865 adults in the US from 8 survey cycles of NHANES from 2003 to 2018, to investigate the associations of PFAS compounds in body serum, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS), with biological aging. Generalized linear models showed that higher human exposure to PFAS was associated with accelerated biological aging. Importantly, human exposure to PFOA, PFOS, PFNA, and PFHxS with detected level (above 0.10 ng/mL) was associated with an average of 3.3 year (95 %CI: 2.7, 3.9, P < 0.001), 14.9 year (95 %CI: 7.2, 22.7, P < 0.001), 10.9 years (95 %CI: 3.9, 17.7, P < 0.001), and 8.8 years (95 %CI: 4.8, 12.9, P < 0.001) of biological aging acceleration. Cubic spline models indicated exposure-response relationships where there was no safe threshold of PFAS level regarding harms to human healthy aging. The weighted sum regression model found the significant associations of PFAS compound mixture with biological aging acceleration, and PFOA was the dominant contributor among 4 PFAS compounds. Mediation analysis suggested that C-reactive protein, one of the inflammation biomarkers, might play as mediator in PFAS-induced accelerated biological aging, but not Triglyceride-glucose index. In summary, our study suggests that the effects of PFAS on biological aging acceleration should be of concern and more action plans to address their negative impact on human health should be launched.

The potential mediating role of the gut microbiome and metabolites in the association between PFAS and kidney function in young adults: A proof-of-concept study

BACKGROUND

Chronic kidney disease (CKD) affects over 10 % of the global population and can lead to kidney failure and death. Exposure to per- and polyfluoroalkyl substances (PFAS) is associated with increased risk of CKD, yet studies examining the mechanisms linking PFAS and kidney function are lacking. In this exploratory study, we examined longitudinal associations of PFAS exposure with kidney function, and tested if associations were mediated by altered gut bacterial taxa or plasma metabolites using a multi-omics mediation analysis.

METHODS

Seventy-eight young adults from the Children's Health Study were included in this longitudinal cohort study. At baseline, seven plasma PFAS and untargeted plasma metabolomics were measured using liquid chromatography/mass-spectrometry. Baseline gut bacterial abundance was characterized using 16S rRNA sequencing and examined at the genus level. At follow-up, serum creatinine and cystatin-C concentrations were quantified to estimate glomerular filtration rate (eGFR). High-dimensional multi-omics analyses were conducted to assess the association between baseline PFAS exposure with follow-up eGFR, mediated by gut microbiome and circulating metabolite levels.

RESULTS

PFAS burden score, a variable developed to estimate exposure to chemical mixtures, was associated with kidney function. Each standard deviation increase in baseline PFAS burden score was associated with a 2.4 % lower eGFR at follow-up (95 % CI:[0.1 %,4.8 %]). Following high-dimensional mediation analyses with the microbiome and circulating metabolites, a joint component (characterized by reduced Lachnospiraceae and 17b-estradiol and increased succinate, retinoate and dodecanoic acid) and a metabolite component (characterized by increased hypotaurine and decreased D-pinitol and ureidopropionate) mediated 38 % and 50 % of the effect between PFAS burden score and eGFR, respectively.

CONCLUSION

Our proof-of-concept analysis provides the first evidence that reduced short-chain fatty acid-producing bacteria and anti-inflammatory metabolites may link PFAS exposure with impaired kidney function. This study raises the possibility of future targeted interventions that can alter gut microbiome or circulating metabolite profiles to prevent PFAS induced kidney damage.

Untargeted serum metabonomic reveals alleviated ovalbumin-induced asthma by Baijin Pingchuan through primary bile acid biosynthesis

OBJECTIVE

To investigate the effect of baijinpingchuan (, BJPC) on the asthma rat model and identify differential metabolites and disturbed metabolic pathways.

METHODS

The rats were categorized into six groups: control, dexamethasone (DEX), ovalbumin (OVA), and low-, median-, and high-dose BJPC. The rats, except for the control group, were initially treated with OVA to develop the asthma model, which was then activated using DEX, OVA, and low-, median-, and high-dose BJPC. Enzyme-linked immunosorbent assay kit was used to detect the expression of interleukin (IL)-33, IL-25, thymic stromal lymphopoietin (TSLP), and transforming growth factor-beta 1 (TGF-β1). Hematoxylin and eosin staining were performed to observe the pathological condition of the lung. Untargeted serum metabonomic analysis was conducted to identify differential metabolites and disturbed metabolic pathways.

RESULTS

High-dose BJPC significantly inhibited the expression of IL-33, IL-25, TSLP, and TGF-β1 (P < 0.0001). Further, high-dose BJPC improved inflammatory cell infiltration, which plays a similar role in asthma as DEX. OVA-induced and BJPC-treated rats were identified through 17 differential metabolites, especially cholic acid. Furthermore, primary bile acid biosynthesis was a significantly differential pathway in the mechanism of BJPC for treating asthma.

CONCLUSIONS

BJPC plays an anti-inflammation role in asthma, which might be a promising therapy through mediating primary bile acid biosynthesis.

Cord plasma metabolomic signatures of prenatal per- and polyfluoroalkyl substance (PFAS) exposures in the Boston Birth Cohort

BACKGROUND

Prenatal per- and polyfluoroalkyl substance (PFAS) exposures are associated with adverse offspring health outcomes, yet the underlying pathological mechanisms are unclear. Cord blood metabolomics can identify potentially important pathways associated with prenatal PFAS exposures, providing mechanistic insights that may help explain PFAS' long-term health effects.

METHODS

The study included 590 mother-infant dyads from the Boston Birth Cohort. We measured PFAS in maternal plasma samples collected 24-72 h after delivery and metabolites in cord plasma samples. We used metabolome-wide association studies and pathway enrichment analyses to identify metabolites and pathways associated with individual PFAS, and quantile-based g-computation models to examine associations of metabolites with the PFAS mixture. We used False Discovery Rate to account for multiple comparisons.

RESULTS

We found that 331 metabolites and 18 pathways were associated with ≥ 1 PFAS, and 38 metabolites were associated with the PFAS mixture, predominantly amino acids and lipids. Amino acids such as alanine and lysine and their pathways, crucial to energy generation, biosynthesis, and bone health, were associated with PFAS and may explain PFAS' effects on fetal growth restriction. Carnitines and carnitine shuttle pathway, associated with 7 PFAS and the PFAS mixture, are involved in mitochondrial fatty acid β-oxidation, which may predispose higher risks of fetal and child growth restriction and cardiovascular diseases. Lipids, such as glycerophospholipids and their related pathway, can contribute to insulin resistance and diabetes by modulating transporters on cell membranes, participating in β-cell signaling pathways, and inducing oxidative damage. Neurotransmission-related metabolites and pathways associated with PFAS, including cofactors, precursors, and neurotransmitters, may explain the PFAS' effects on child neurodevelopment. We observed stronger associations between prenatal PFAS exposures and metabolites in males.

CONCLUSIONS

This prospective birth cohort study contributes to the limited literature on potential metabolomic perturbations for prenatal PFAS exposures. Future studies are needed to replicate our findings and link prenatal PFAS associated metabolomic perturbations to long-term child health outcomes.

Metabolic changes associated with PFAS exposure in firefighters: A pilot study

This pilot study investigated the association between occupational exposure to per- and polyfluoroalkyl substances (PFASs) and metabolic profiles among two groups of aviation firefighters (n = 37), with an average of 6 and 31 years of working experience (here referred as junior and senior firefighters) at airports across Australia, with samples collected in 2013. PFAS levels in serum were determined in a previous study to be >17 times higher in the senior firefighter group, reflecting the difference in their occupational exposure to fluorosurfactants among the groups. The aim was to examine metabolic patterns across a broad range of PFAS exposure by comparing metabolic differences and their associations with PFAS levels. In this cross-sectional study, the length of firefighting experience and PFAS levels in serum were both further associated with changes in several classes of metabolites, including free fatty acids, bile acids, amino acids, lipids and metabolites related to gut microbial metabolism. The metabolites associated with the length of firefighting experience showed similarities with the metabolites associated with PFAS levels. A non-monotonic response to PFAS concentrations, particularly in saturated fatty acids, was also observed. In the junior firefighter group, the PFAS concentrations were positively associated with saturated fatty acids, i.e., the saturated fatty acid levels increased with increased PFAS levels. In the senior firefighter group, the trend was opposite, with saturated fatty acids decreasing with increasing levels of PFAS. Accounting for potential confounding factors such as BMI and age could not explain the results. While the study population was small, our results plausibly indicate that PFAS exposure can lead to a metabolic compensation strategy that is disrupted at high, long-term exposures. Our study also suggests that serum metabolites serve as better effect-based markers of the impact of exposure than the traditional clinical measurements alone, such as total triglycerides or total cholesterol.

Per- and polyfluoroalkyl substances (PFAS) and cancer: Detection methodologies, epidemiological insights, potential carcinogenic mechanisms, and future perspectives

Per- and polyfluoroalkyl substances (PFAS), known as "forever chemicals," are synthetic chemicals which have been used since the 1940s. Given their remarkable thermostability and chemical stability, PFAS have been widely utilized in commercial products, including textiles, surfactants, food packages, nonstick coatings, and fire-fighting foams. Thus, PFAS are widely distributed worldwide and have been detected in human urine, blood, breast milk, tissues and other substances. Growing concerns over the risks of PFAS, including their toxicity and carcinogenicity, have attracted people's attention. Recent reviews have predominantly emphasized advancements in the detection, adsorption, and degradation of PFAS through their chemical structures and toxic properties; however, further examination of the literature is needed to determine the link between PFAS exposure and cancer risk. Here, we introduced different PFAS detection methods based on sensors and liquid chromatography-mass spectrometry (LC-MS). Then, we discussed epidemiological investigations on PFAS levels and cancer risks in recent years, as well as the mechanisms underlying the carcinogenesis. Finally, we proposed the "4C principles" for ongoing exploration and refinement in this field. This review highlights PFAS-cancer associations to fill knowledge gaps and provide evidence-based strategies for future research.

Forever chemicals don't make hero mutant ninja turtles: Elevated PFAS levels linked to unusual scute development in newly emerged freshwater turtle hatchlings (Emydura macquarii macquarii) and a reduction in turtle populations

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants known to pose significant risks to human and wildlife health. Freshwater turtles (Emydura macquarii macquarii), as long-lived species inhabiting aquatic ecosystems, are particularly vulnerable to PFAS bioaccumulation. This study investigated the multifaceted impact of PFAS contamination on these turtles, focusing on metabolic disruptions, reproductive success, hatchling health, and population impacts. Comprehensive analyses, including proteomics, lipidomics, metabolomics, and histopathology, were conducted on turtles from PFAS-impacted, control, and reference sites. The findings reveal significant metabolic disruptions in PFAS-exposed turtles, with alterations in amino acid and lipid metabolism, energy production, and oxidative stress responses. Proteomic analysis identified several health biomarkers indicative of early disease progression. Despite high levels of PFAS in tissues and organs, no gross or histopathological phenotypical abnormalities were directly linked to PFAS exposure. Gravid females from contaminated sites exhibited altered egg composition, particularly in magnesium to calcium ratios, potentially affecting eggshell strength. Biochemical profiles of egg albumin and yolk indicated significant differences in metabolites and lipids between contaminated and reference sites, suggesting potential impacts on embryo development. Hatchling deformities were notably higher and with increased frequency in terms of the types of deformities at the PFAS-impacted sites, with common defects including abnormal intergular scale shapes and marginal scale counts. Furthermore, the demographic profile of the turtle population showed a lack of juvenile turtles at contaminated sites, indicating reduced recruitment and potential long-term population declines. This indicates a field-based demonstration of an Adverse Outcome Pathway, from elevated levels of PFAS in the turtles, to biochemical perturbations within the animals, and finally population effects. These findings underscore the urgent need for regulatory measures to address PFAS contamination and its detrimental effects on wildlife.

Analytical challenges and opportunities in the study of endocrine disrupting chemicals within an exposomics framework

Exposomics aims to measure human exposures throughout the lifespan and the changes they produce in the human body. Exposome-scale studies have significant potential to understand the interplay of environmental factors with complex multifactorial diseases widespread in our society and whose origin remain unclear. In this framework, the study of the chemical exposome aims to cover all chemical exposures and their effects in human health but, today, this goal still seems unfeasible or at least very challenging, which makes the exposome for now only a concept. Furthermore, the study of the chemical exposome faces several methodological challenges such as moving from specific targeted methodologies towards high-throughput multitargeted and non-targeted approaches, guaranteeing the availability and quality of biological samples to obtain quality analytical data, standardization of applied analytical methodologies, as well as the statistical assignment of increasingly complex datasets, or the identification of (un)known analytes. This review discusses the various steps involved in applying the exposome concept from an analytical perspective. It provides an overview of the wide variety of existing analytical methods and instruments, highlighting their complementarity to develop combined analytical strategies to advance towards the chemical exposome characterization. In addition, this review focuses on endocrine disrupting chemicals (EDCs) to show how studying even a minor part of the chemical exposome represents a great challenge. Analytical strategies applied in an exposomics context have shown great potential to elucidate the role of EDCs in health outcomes. However, translating innovative methods into etiological research and chemical risk assessment will require a multidisciplinary effort. Unlike other review articles focused on exposomics, this review offers a holistic view from the perspective of analytical chemistry and discuss the entire analytical workflow to finally obtain valuable results.

Interactions of Potential Endocrine-Disrupting Chemicals with Whole Human Proteome Predicted by AlphaFold2 Using an In Silico Approach

Binding with proteins is a critical molecular initiating event through which environmental pollutants exert toxic effects in humans. Previous studies have been limited by the availability of three-dimensional (3D) protein structures and have focused on only a small set of environmental contaminants. Using the highly accurate 3D protein structure predicted by AlphaFold2, this study explored over 60 million interactions obtained through molecular docking between 20,503 human proteins and 1251 potential endocrine-disrupting chemicals. A total of 66,613,773 docking results were obtained, 1.2% of which were considered to be high binding, as their docking scores were lower than -7. Monocyte to macrophage differentiation factor 2 (MMD2) was predicted to interact with the highest number of environmental pollutants (526), with polychlorinated biphenyls and polychlorinated dibenzofurans accounting for a significant proportion. Dimension reduction and clustering analysis revealed distinct protein profiles characterized by high binding affinities for perfluoroalkyl and polyfluoroalkyl substances (PFAS), phthalate-like chemicals, and other pollutants, consistent with their uniquely enriched pathways. Further structural analysis indicated that binding pockets with a high proportion of charged amino acid residues, relatively low α-helix content, and high β-sheet content were more likely to bind to PFAS than others. This study provides insights into the toxicity pathways of various pollutants impacting human health and offers novel perspectives for the establishment and expansion of adverse outcome pathway-based models.

Metabolic Perturbations Associated with both PFAS Exposure and Perinatal/Antenatal Depression in Pregnant Individuals: A Meet-in-the-Middle Scoping Review

PURPOSE OF REVIEW

Depression during the perinatal or antenatal period affects at least 1 in 10 women worldwide, with long term health implications for the mother and child. Concurrently, there is increasing evidence associating maternal exposure to per- and poly-fluoroalkyl substances (PFAS) to adverse pregnancy outcomes. We reviewed the body of evidence examining both the associations between PFAS exposure and perturbations in the maternal metabolome, and the associations between the maternal metabolome and perinatal/antenatal depression. Through this, we sought to explore existing evidence of the perinatal metabolome as a potential mediation pathway linking PFAS exposure and perinatal/antenatal depression.

RECENT FINDINGS

There are few studies examining the metabolomics of PFAS exposure-specifically in pregnant women-and the metabolomics of perinatal/antenatal depression, let alone studies examining both simultaneously. Of the studies reviewed (N = 11), the majority were cross sectional, based outside of the US, and conducted on largely homogenous populations. Our review identified 23 metabolic pathways in the perinatal metabolome common to both PFAS exposure and perinatal/antenatal depression. Future studies may consider findings from our review to conduct literature-derived hypothesis testing focusing on fatty acid metabolism, alanine metabolism, glutamate metabolism, and tyrosine metabolism when exploring the biochemical mechanisms conferring the risk of perinatal/antenatal depression due to PFAS exposure. We recommend that researchers also utilize heterogenous populations, longitudinal study designs, and mediation approaches to elucidate key pathways linking PFAS exposures to perinatal/antenatal depression.

PFAS Levels, Early Life Factors, and Mammographic Breast Density in Premenopausal Women

BACKGROUND

Mammographic breast density (MBD) is a strong risk factor and an intermediate phenotype for breast cancer, yet there are limited studies on how environmental pollutants are associated with MBD.

OBJECTIVE

We investigated associations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonate (PFHxS) levels with measures of MBD and evaluated if early life factors modified any associations.

METHODS

Metabolon performed metabolomics analysis using ultrahigh-performance liquid chromatography/tandem accurate mass spectrometry in fasting blood from 705 premenopausal women completing their annual screening mammogram in St. Louis, Missouri. We calculated least square means (LSM) of mammographic volumetric percent density (VPD), dense volume (DV), and nondense volume (NDV) by quartiles (Q) of PFOS, PFOA, and PFHxS from multivariable linear regression modeling overall and stratified by recruitment period, race, age at menarche, and body shape at age 10. Models were adjusted for age, age at menarche, body fat percentage, race, family history of breast cancer, oral contraceptive use, alcohol consumption, parity/age at first birth, and body shape at age 10.

RESULTS

PFOS, PFOA, and PFHxS were not significantly associated with VPD or NDV. PFHxS was significantly positively associated with DV (Q 1 = 67.64   cm 3 , Q 2 = 69.91   cm 3 , Q 3 = 69.06   cm 3 , Q 4 = 75.79   cm 3 ; p -trend = 0.03 ). PFOS was positively associated with DV (Q 1 = 65.45   cm 3 , Q 2 = 70.74   cm 3 , Q 3 = 73.31   cm 3 , Q 4 = 73.52   cm 3 ; p -trend = 0.06 ) with DV being 8.1%, 12%, and 12.3% higher in Q2, Q3, and Q4 compared to Q1. Among women who were underweight/normal weight at age 10, PFOS was positively associated with VPD (Q 1 = 9.02 % , Q 2 = 9.11 % , Q 3 = 9.48 % , Q 4 = 9.92 % ; p -trend = 0.04 ) while there was an inverse association among women who were overweight/obese at age 10 (Q 1 = 7.46 % , Q 2 = 6.94 % , Q 3 = 6.78 % , Q 4 = 5.47 % ; p -trend = 0.005 ) (p -interaction = 0.04 ).

DISCUSSION

We report novel associations of PFHxS and PFOS with DV in premenopausal women. PFOS, PFOA, and PFHxS were not associated with VPD and NDV. In addition, body shape at age 10 may modify the associations of PFOS with MBD. Further studies are needed to validate our findings and to evaluate the associations of other per- and polyfluoroalkyl substances (PFAS), as well as mixtures of PFAS, with MBD. https://doi.org/10.1289/EHP14065.

PFAS and their association with the increased risk of cardiovascular disease in postmenopausal women

Cardiovascular diseases (CVDs) are one of the major causes of death globally. In addition to traditional risk factors such as unhealthy lifestyles (smoking, obesity, sedentary) and genetics, common environmental exposures, including persistent environmental contaminants, may also influence CVD risk. Per- and polyfluoroalkyl substances (PFASs) are a class of highly fluorinated chemicals used in household consumer and industrial products known to persist in our environment for years, causing health concerns that are now linked to endocrine disruptions and related outcomes in women, including interference of the cardiovascular and reproductive systems. In postmenopausal women, higher levels of PFAS are observed than in premenopausal women due to the cessation of menstruation, which is crucial for PFAS excretion. Because of these findings, we explored the association between perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorobutanesulfonic acid in postmenopausal women from our previously established CVD study. We used liquid chromatography with tandem mass spectrometry, supported by machine learning approaches, and the detection and quantification of serum metabolites and proteins. Here, we show that PFOS can be a good predictor of coronary artery disease, whereas PFOA can be an intermediate predictor of coronary microvascular disease. We also found that the PFAS levels in our study are significantly associated with inflammation-related proteins. Our findings may provide new insight into the potential mechanisms underlying the PFAS-induced risk of CVDs in this population. This study shows that exposure to PFOA and PFOS is associated with an increased risk of cardiovascular disease in postmenopausal women. PFOS and PFOA levels correlate with amino acids and proteins related to inflammation. These circulating biomarkers contribute to the etiology of CVD and potentially implicate a mechanistic relationship between PFAS exposure and increased risk of cardiovascular events in this population.

Exploring the Chemical Space of the Exposome: How Far Have We Gone?

Around two-thirds of chronic human disease can not be explained by genetics alone. The Lancet Commission on Pollution and Health estimates that 16% of global premature deaths are linked to pollution. Additionally, it is now thought that humankind has surpassed the safe planetary operating space for introducing human-made chemicals into the Earth System. Direct and indirect exposure to a myriad of chemicals, known and unknown, poses a significant threat to biodiversity and human health, from vaccine efficacy to the rise of antimicrobial resistance as well as autoimmune diseases and mental health disorders. The exposome chemical space remains largely uncharted due to the sheer number of possible chemical structures, estimated at over 1060 unique forms. Conventional methods have cataloged only a fraction of the exposome, overlooking transformation products and often yielding uncertain results. In this Perspective, we have reviewed the latest efforts in mapping the exposome chemical space and its subspaces. We also provide our view on how the integration of data-driven approaches might be able to bridge the identified gaps.

Hunting Metabolic Biomarkers for Exposure to Per- and Polyfluoroalkyl Substances: A Review

Per- and polyfluoroalkyl substances (PFAS) represent a class of persistent synthetic chemicals extensively utilized across industrial and consumer sectors, raising substantial environmental and human health concerns. Epidemiological investigations have robustly linked PFAS exposure to a spectrum of adverse health outcomes. Altered metabolites stand as promising biomarkers, offering insights into the identification of specific environmental pollutants and their deleterious impacts on human health. However, elucidating metabolic alterations attributable to PFAS exposure and their ensuing health effects has remained challenging. In light of this, this review aims to elucidate potential biomarkers of PFAS exposure by presenting a comprehensive overview of recent metabolomics-based studies exploring PFAS toxicity. Details of PFAS types, sources, and human exposure patterns are provided. Furthermore, insights into PFAS-induced liver toxicity, reproductive and developmental toxicity, cardiovascular toxicity, glucose homeostasis disruption, kidney toxicity, and carcinogenesis are synthesized. Additionally, a thorough examination of studies utilizing metabolomics to delineate PFAS exposure and toxicity biomarkers across blood, liver, and urine specimens is presented. This review endeavors to advance our understanding of PFAS biomarkers regarding exposure and associated toxicological effects.

Cross-Sectional Associations between Prenatal Per- and Poly-Fluoroalkyl Substances and Bioactive Lipids in Three Environmental Influences on Child Health Outcomes (ECHO) Cohorts

Prenatal per- and poly-fluoroalkyl substances (PFAS) exposure may influence gestational outcomes through bioactive lipids─metabolic and inflammation pathway indicators. We estimated associations between prenatal PFAS exposure and bioactive lipids, measuring 12 serum PFAS and 50 plasma bioactive lipids in 414 pregnant women (median 17.4 weeks' gestation) from three Environmental influences on Child Health Outcomes Program cohorts. Pairwise association estimates across cohorts were obtained through linear mixed models and meta-analysis, adjusting the former for false discovery rates. Associations between the PFAS mixture and bioactive lipids were estimated using quantile g-computation. Pairwise analyses revealed bioactive lipid levels associated with PFDeA, PFNA, PFOA, and PFUdA (p < 0.05) across three enzymatic pathways (cyclooxygenase, cytochrome p450, lipoxygenase) in at least one combined cohort analysis, and PFOA and PFUdA (q < 0.2) in one linear mixed model. The strongest signature revealed doubling in PFOA corresponding with PGD2 (cyclooxygenase pathway; +24.3%, 95% CI: 7.3-43.9%) in the combined cohort. Mixture analysis revealed nine positive associations across all pathways with the PFAS mixture, the strongest signature indicating a quartile increase in the PFAS mixture associated with PGD2 (+34%, 95% CI: 8-66%), primarily driven by PFOS. Bioactive lipids emerged as prenatal PFAS exposure biomarkers, deepening insights into PFAS' influence on pregnancy outcomes.

Prenatal PFAS exposure, gut microbiota dysbiosis, and neurobehavioral development in childhood

Studies on the role of the gut microbiota in the associations between per- and polyfluoroalkyl substance (PFAS) exposure and adverse neurodevelopment are limited. Umbilical cord serum and faeces samples were collected from children, and the Strengths and Difficulties Questionnaire (SDQ) was conducted. Generalized linear models, linear mixed-effects models, multivariate analysis by linear models and microbiome regression-based kernel association tests were used to evaluate the associations among PFAS exposure, the gut microbiota, and neurobehavioural development. Perfluorohexane sulfonic acid (PFHxS) exposure was associated with increased scores for conduct problems and externalizing problems, as well as altered gut microbiota alpha and beta diversity. PFHxS concentrations were associated with higher relative abundances of Enterococcus spp. but lower relative abundances of several short-chain fatty acid-producing genera (e.g., Ruminococcus gauvreauii group spp.). PFHxS exposure was also associated with increased oxidative phosphorylation. Alpha and beta diversity were found significantly associated with conduct problems and externalizing problems. Ruminococcus gauvreauii group spp. abundance was positively correlated with prosocial behavior scores. Increased alpha diversity played a mediating role in the associations of PFHxS exposure with conduct problems. Our results suggest that the gut microbiota might play an important role in PFAS neurotoxicity, which may have implications for PFAS control.

Suspect, Nontarget Screening, and Toxicity Prediction of Per- and Polyfluoroalkyl Substances in the Landfill Leachate

Landfills are the final stage of urban wastes containing perfluoroalkyl and polyfluoroalkyl substances (PFASs). PFASs in the landfill leachate may contaminate the surrounding groundwater. As major environmental pollutants, emerging PFASs have raised global concern. Besides the widely reported legacy PFASs, the distribution and potential toxic effects of numerous emerging PFASs remain unclear, and unknown PFASs still need discovery and characterization. This study proposed a comprehensive method for PFAS screening in leachate samples using suspect and nontarget analysis. A total of 48 PFASs from 10 classes were identified; nine novel PFASs including eight chloroperfluoropolyether carboxylates (Cl-PFPECAs) and bistriflimide (HNTf2) were reported for the first time in the leachate, where Cl-PFPECA-3,1 and Cl-PFPECA-2,2 were first reported in environmental media. Optimized molecular docking models were established for prioritizing the PFASs with potential activity against peroxisome proliferator-activated receptor α and estrogen receptor α. Our results indicated that several emerging PFASs of N-methyl perfluoroalkyl sulfonamido acetic acids (N-MeFASAAs), n:3 fluorotelomer carboxylic acid (n:3 FTCA), and n:2 fluorotelomer sulfonate (n:2 FTSA) have potential health risks that cannot be ignored.

Assessing the performance of a targeted absolute quantification isotope dilution liquid chromatograhy tandem mass spectrometry assay versus a commercial nontargeted relative quantification assay for detection of three major perfluoroalkyls in human blood

Isotope dilution ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) is commonly used for trace analysis of polyfluoroalkyl and perfluoroalkyl substances (PFAS) in difficult matrices. Commercial nontargeted analysis of major PFAS where relative concentrations are obtained cost effectively is rapidly emerging and is claimed to provide comparable results to that of absolute quantification using matrix matched calibration and isotope dilution UHPLC-MS/MS. However, this remains to be demonstrated on a large scale. We aimed to assess the performance of a targeted absolute quantification isotope dilution LC-MS/MS assay versus a commercial nontargeted relative quantification assay for detection of three major PFAS in human blood. We evaluated a population-based cohort of 503 individuals. Correlations were assessed using Spearman's rank correlation coefficients (rho). Precision and bias were assessed using Bland-Altman plots. For perfluorooctane sulfonic acid, the median concentrations were 5.10 ng/mL (interquartile range [IQR] 3.50-7.24 ng/mL), the two assays correlated with rho 0.83. For perfluorooctanoic acid, the median concentrations were 2.14 ng/mL (IQR 1.60-3.0 ng/mL), the two assays correlated with rho 0.92. For perfluorohexanesulfonate, the median concentrations were 5.5 ng/mL (IQR 2.50-11.61 ng/mL), the two assays correlated with rho 0.96. The Bland-Altman statistical test showed agreement of the mean difference for the majority of samples (97-98%) between the two assays. Absolute plasma concentrations of PFAS obtained using matrix matched calibration and isotope dilution UHPLC-MS/MS show agreement with relative plasma concentrations from a nontargeted commercial platform by Metabolon. We observed striking consistency between the two assays when examining the associations of the three PFAS with cholesterol, offering additional confidence in the validity of utilizing the nontargeted approach for correlations with various health phenotypes.

Kynurenic Acid Plays a Protective Role in Hepatotoxicity Induced by HFPO-DA in Male Mice

Following its introduction as an alternative to perfluorooctanoic acid, hexafluoropropylene oxide dimer acid (HFPO-DA) has been extensively detected in various environmental matrices. Despite this prevalence, limited information is available regarding its hepatotoxicity biomarkers. In this study, toxicokinetic simulations indicated that under repeated treatment, HFPO-DA in mice serum reached a steady state by the 4th day. To assess its subacute hepatic effects and identify potential biomarkers, mice were administered HFPO-DA orally at doses of 0, 0.1, 0.5, 2.5, 12.5, or 62.5 mg/kg/d for 7 d. Results revealed that the lowest observed adverse effect levels were 0.5 mg/kg/d for hepatomegaly and 2.5 mg/kg/d for hepatic injury. Serum metabolomics analysis identified 34, 58, and 118 differential metabolites in the 0.1, 0.5, and 2.5 mg/kg/d groups, respectively, compared to the control group. Based on weighted gene coexpression network analysis, eight potential hepatotoxicity-related metabolites were identified; among them, kynurenic acid (KA) in mouse serum exhibited the highest correlation with liver injury. Furthermore, liver-targeted metabolomics analysis demonstrated that HFPO-DA exposure induced metabolic migration of the kynurenine pathway from KA to nicotinamide adenine dinucleotide, resulting in the activation of endoplasmic reticulum stress and the nuclear factor kappa-B signaling pathway. Notably, pretreatment with KA significantly attenuated liver injury induced by HFPO-DA exposure in mice, highlighting the pivotal roles of KA in the hepatotoxicity of HFPO-DA.

Per- and polyfluoroalkyl substances and cardiometabolic diseases: A review

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent and widespread environmental pollutants that represent a high concern for human health. They have been shown to be associated with several important physiological processes such as lipid metabolism and the immune system. Consequently, PFAS are suspected to play a role in cardiometabolic disease development. However, the evidence regarding associations between PFAS and overt cardiovascular disease and type 2 diabetes remains limited and inconsistent. To address this, we conducted a review of the epidemiological evidence. A deeper understanding of potential underlying molecular mechanisms may help to explain inconsistencies in epidemiological findings. Thus, to gain more mechanistic insight, we also summarized evidence from omics and laboratory studies into an adverse outcome pathway framework. Our observations indicate the potential for associations of PFAS with multiple molecular pathways that could have opposite associations with disease risk, which could be further modified by mixture composition, lifestyle factors or genetic polymorphisms. This identifies the need for exposome studies considering mixture effects, the use of multi-omics data to gain insight in relevant pathways and the integration of epidemiological and laboratory studies to enhance mechanistic understanding and causal inference. Improved comprehension is essential for environmental health risk assessments.

Comparative Toxicological Effects of Perfluorooctane Sulfonate and Its Alternative 6:2 Chlorinated Polyfluorinated Ether Sulfonate on Earthworms

High levels of 6:2 chlorinated polyfluorinated ether sulfonate (F-53B), which is a substitute for perfluorooctane sulfonate (PFOS), are detected in various environmental matrices, wildlife, and humans. Chlorinated polyfluorinated ether sulfonate has received increased attention due to its potential risk to ecosystems. However, its toxicity in the soil organisms remains unclear. In the present study, a comparative investigation was conducted on the toxicities of 6:2 Chlorinated polyfluorinated ether sulfonate (F-53B) and PFOS to the earthworm Eisenia. fetida. F-53B was significantly more acutely toxic to earthworms than PFOS, with median lethal concentrations of 1.43 and 1.83 mmol/kg dry soil (~816 and 984 mg/kg dry soil), respectively. Although both F-53B and PFOS, at 0.4 mmol/kg dry soil (=228 and 215 mg/kg dry soil) caused oxidative stress in earthworms, as evidenced by increased superoxide dismutase, peroxidase, and catalase activities as well as malondialdehyde level, the stress caused by F-53B was higher than that caused by PFOS. In transcriptomic and metabolomic studies, negative effects of PFOS and F-53B were observed on several metabolic processes in earthworms, including protein digestion and amino acid absorption, lipid metabolism, and the immune response. Compared with PFOS, F-53B exhibited a weaker disruption of lipid metabolism, comparable potency for toxicity to the immune response, and a stronger potency in extracellular matrix destruction along with apoptosis and ferroptosis induction. Hence, our data suggest that F-53B is more toxic than PFOS to earthworms. The findings provide some new insights into the potential toxicity of F-53B to soil organisms. Environ Toxicol Chem 2024;43:170-181. © 2023 SETAC.

The association between prenatal per-and polyfluoroalkyl substance levels and Kawasaki disease among children of up to 4 years of age: A prospective birth cohort of the Japan Environment and Children's study

Kawasaki disease (KD) is common among pediatric patients and is associated with an increased risk of later cardiovascular complications, though the precise pathophysiology of KD remains unknown. Per- and polyfluoroalkyl substances (PFAS) have gathered notoriety as the causal pathogens of numerous diseases as well as for their immunosuppressive effects. The present epidemiological study aims to assess whether PFAS may affect KD risk. We evaluated research participants included in the ongoing prospective nationwide birth cohort of the Japan Environment and Children's Study (JECS). Among the over 100,000 pregnant women enrolled in the JECS study, 28 types of PFAS were measured in pregnancy in a subset of participants (N = 25,040). The JECS followed their children born between 2011 and 2014 (n total infants = 25,256; n Kawasaki disease infants = 271), up to age four. Among the 28 types of PFAS, those which were detected in >60 % of participants at levels above the method reporting limit (MRL) were eligible for analyses. Multivariable logistic regressions were implemented on the seven eligible PFAS, adjusting for multiple comparison effects. Finally, we conducted Weighted Quantile Sum (WQS) and Bayesian kernel machine regression (BKMR) to assess the effects of the PFAS mixture on KD. Therefore, we ran the BKMR model using kernel mechanical regression equations to examine PFAS exposure and the outcomes of KD. Upon analysis, the adjusted multivariable regression results did not reach statistical significance for the seven eligible substances on KD, while odds ratios were all under 1.0. WQS regression was used to estimate the mixture effect of the seven eligible PFAS, revealing a negative correlation with KD incidence; similarly, BKMR implied an inverse association between the PFAS mixture effect and KD incidence. In conclusion, PFAS exposure was not associated with increased KD incidence.

Overall and individual associations between per- and polyfluoroalkyl substances and liver function indices and the metabolic mechanism

Per- and polyfluoroalkyl substances (PFAS) can disrupt liver homeostasis. Studies have shown that a single exposure to PFAS may provoke abnormal liver function; however, few studies have investigated the overall effect of PFAS mixtures. We aimed to investigate associations between exposure to PFAS mixtures and liver function indices and explore the relevant mechanisms. This study included 278 adult males from Guangzhou, China. Serum metabolite profiles were analyzed using untargeted metabolomics. We applied weighted quantile sum (WQS) regression as well as Bayesian kernel machine regression (BKMR) to analyze the association of nine PFAS mixtures with 14 liver function indices. PFAS mixtures were positively associated with apolipoprotein B (APOB) and gamma-glutamyltransferase (GGT) and negatively associated with direct bilirubin (DBIL) and total bilirubin (TBIL) in both the WQS and BKMR analyses. In addition, Spearman's correlation test showed individual PFAS correlated with APOB, GGT, TBIL, and DBIL, while there's little correlation between individual PFAS and other liver function indices. In linear regression analysis, PFHxS, PFOS, PFHpS, PFNA, PFDA, and PFUdA were associated with APOB; PFOA, PFDA, PFOS, PFNA, and PFUdA were associated with GGT. Subsequently, a metabolome-wide association study and mediation analysis were combined to explore metabolites that mediate these associations. The mechanisms linking PFAS to APOB and GGT are mainly related with amino acid and glycerophospholipid metabolism. High-dimensional mediation analysis showed that glycerophospholipids are the main markers of the association between PFAS and APOB, and that (R)-dihydromaleimide, Ile Leu, (R)-(+)-2-pyrrolidone-5-carboxylic acid, and L-glutamate are the main markers of the association between PFAS and GGT. In summary, overall associations between PFAS and specific indices of liver function were found using two statistical methods; the metabolic pathways and markers identified here may serve to prompt more detailed study in animal-based systems, as well as a similar detailed analysis in other populations.

In utero exposures to perfluoroalkyl substances and the human fetal liver metabolome in Scotland: a cross-sectional study

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances are classed as endocrine disrupting compounds but continue to be used in many products such as firefighting foams, flame retardants, utensil coatings, and waterproofing of food packaging. Perfluoroalkyl exposure aberrantly modulates lipid, metabolite, and bile acid levels, increasing susceptibility to onset and severity of metabolic diseases, such as diabetes and metabolic dysfunction-associated steatotic liver disease. To date, most studies in humans have focused on perfluoroalkyl-exposure effects in adults. In this study we aimed to show if perfluoroalkyls are present in the human fetal liver and if they have metabolic consequences for the human fetus.

METHODS

In this cross-sectional study, human fetal livers from elective termination of pregnancies at the Aberdeen Pregnancy Counselling Service, Aberdeen, UK, were analysed by both targeted (bile acids and perfluoroalkyl substances) and combined targeted and untargeted (lipids and polar metabolites) mass spectrometry based metabolomic analyses, as well as with RNA-Seq. Only fetuses from normally progressing pregnancies (determined at ultrasound scan before termination), terminated for non-medical reasons, from women older than 16 years, fluent in English, and between 11 and 21 weeks of gestation were collected. Women exhibiting considerable emotional distress or whose fetuses had anomalies identified at ultrasound scan were excluded. Stringent bioinformatic and statistical methods such as partial correlation network analysis, linear regression, and pathway analysis were applied to this data to investigate the association of perfluoroalkyl exposure with hepatic metabolic pathways.

FINDINGS

Fetuses included in this study were collected between Dec 2, 2004, and Oct 27, 2014. 78 fetuses were included in the study: all 78 fetuses were included in the metabolomics analysis (40 female and 38 male) and 57 fetuses were included in the RNA-Seq analysis (28 female and 29 male). Metabolites associated with perfluoroalkyl were identified in the fetal liver and these varied with gestational age. Conjugated bile acids were markedly positively associated with fetal age. 23 amino acids, fatty acids, and sugar derivatives in fetal livers were inversely associated with perfluoroalkyl exposure, and the bile acid glycolithocholic acid was markedly positively associated with all quantified perfluoroalkyl. Furthermore, 7α-hydroxy-4-cholesten-3-one, a marker of bile acid synthesis rate, was strongly positively associated with perfluoroalkyl levels and was detectable as early as gestational week 12.

INTERPRETATION

Our study shows direct evidence for the in utero effects of perfluoroalkyl exposure on specific key hepatic products. Our results provide evidence that perfluoroalkyl exposure, with potential future consequences, manifests in the human fetus as early as the first trimester of gestation. Furthermore, the profiles of metabolic changes resemble those observed in perinatal perfluoroalkyl exposures. Such exposures are already linked with susceptibility, initiation, progression, and exacerbation of a wide range of metabolic diseases.

FUNDING

UK Medical Research Council, Horizon Europe Program of the European Union, Seventh Framework Programme of the European Union, NHS Grampian Endowments grants, European Partnership for the Assessment of Risks from Chemicals, Swedish Research Council, Formas, Novo Nordisk Foundation, and the Academy of Finland.

Neonatal per- and polyfluoroalkyl substance exposure in relation to retinoblastoma

BACKGROUND

Neonatal per- and polyfluoroalkyl substance (PFAS) exposure can disrupt hormonal homeostasis and induce neuro- and immunotoxicity in children. In this exploratory study, we investigated associations between PFAS levels in neonatal dried blood spots and retinoblastoma risk.

MATERIALS AND METHODS

This study included 501 retinoblastoma cases born from 1983 to 2011 and 899 controls frequency-matched by birth year (20:1 matching ratio), born to 755 US-born and 366 Mexico-born mothers in California. Perfluorooctanesulfonic acid (PFOS), perflurooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) feature intensities were identified from neonatal blood spots from California newborn Genetic Disease Screening Program. Using logistic regression, we assessed whether an interquartile range (IQR) increase of PFAS levels or having above-mean levels of PFAS in blood affects retinoblastoma risk overall or its subtypes (i.e., unilateral, bilateral). We assessed children of US-born and Mexico-born mothers, separately.

RESULTS AND DISCUSSION

Among all children, above-mean PFOS levels at birth increased the odds of retinoblastoma overall by 29% (95% Confidence Interval (CI): 1.00, 1.67) and unilateral retinoblastoma by 42% (95% CI: 1.03, 1.97). For children of Mexico-born mothers, we estimated the highest odds of retinoblastoma overall (adjusted odds ratio (aOR): 1.67; 95% CI: 1.06, 2.66) and bilateral retinoblastoma (aOR: 2.06; 95% CI: 1.12, 3.92) with above-mean PFOS levels. Among children of US-born mothers, higher PFOS levels increased the odds of unilateral retinoblastoma by 15% (95% CI: 0.99, 1.35) for each IQR increase and by 71% among children with above-mean PFOS levels (95% CI: 1.04, 2.90). In addition, for children of US-born mothers, PFOA increased the odds of retinoblastoma overall (aOR: 1.41; 95% CI: 1.00, 2.02 for above-mean levels, aOR: 1.06; 95% CI: 0.98, 1.16 per IQR increase). PFNA was not associated with retinoblastoma risk.

CONCLUSIONS

Our results suggested that PFOS and PFOA might contribute to retinoblastoma risk in children born in California.

Metabolic and Microbial Profiling of Soil Microbial Community under Per- and Polyfluoroalkyl Substance (PFAS) Stress

Per- and polyfluoroalkyl substances (PFAS) represent significant stress to organisms and are known to disrupt microbial community structure and function. Nevertheless, a detailed knowledge of the soil microbial community responding to PFAS stress at the metabolism level is required. Here we integrated UPLC-HRMS-based metabolomics data with 16S rRNA and ITS amplicon data across soil samples collected adjacent to a fluoropolymer production facility to directly identify the biochemical intermediates in microbial metabolic pathways and the interactions with microbial community structure under PFAS stress. A strong correlation between metabolite and microbial diversity was observed, which demonstrated significant variations in soil metabolite profiles and microbial community structures along with the sampling locations relative to the facility. Certain key metabolites were identified in the metabolite-PFAS co-occurrence network, functioning on microbial metabolisms including lipid metabolism, amino acid metabolism, and secondary metabolite biosynthesis. These results provide novel insights into the impacts of PFAS contamination on soil metabolomes and microbiomes. We suggest that soil metabolomics is an informative and useful tool that could be applied to reinforce the chemical evidence on the disruption of microbial ecological traits.

Perfluorooctanesulfonic Acid and Perfluorooctanoic Acid Promote Migration of Three-Dimensional Colorectal Cancer Spheroids

Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are persistent environmental contaminants that are of increasing public concern worldwide. However, their relationship with colorectal cancer (CRC) is poorly understood. This study aims to comprehensively investigate the effect of PFOS and PFOA on the development and progression of CRC in vitro using a series of biological techniques and metabolic profiling. Herein, the migration of three-dimensional (3D) spheroids of two CRC cell lines, SW48 KRAS wide-type (WT) and SW48 KRAS G12A, were observed after exposure to PFOS and PFOA at 2 μM and 10 μM for 7 days. The time and dose-dependent migration phenotype induced by 10 μM PFOS and PFOA was further confirmed by wound healing and trans-well migration assays. To investigate the mechanism of action, derivatization-mass spectrometry-based metabolic profiles were examined from 3D spheroids of SW48 cell lines exposed to PFOS and PFOA (2 μM and 10 μM). Our findings revealed this exposure altered epithelial-mesenchymal transition related metabolic pathways, including fatty acid β-oxidation and synthesis of proteins, nucleotides, and lipids. Furthermore, this phenotype was confirmed by the downregulation of E-cadherin and upregulation of N-cadherin and vimentin. These findings show novel insight into the relationship between PFOS, PFOA, and CRC.

Prenatal exposures to endocrine disrupting chemicals: The role of multi-omics in understanding toxicity

Endocrine disrupting chemicals (EDCs) are a diverse group of toxicants detected in populations globally. Prenatal EDC exposures impact birth and childhood outcomes. EDCs work through persistent changes at the molecular, cellular, and organ level. Molecular and biochemical signals or 'omics' can be measured at various functional levels - including the epigenome, transcriptome, proteome, metabolome, and the microbiome. In this narrative review, we introduce each omics and give examples of associations with prenatal EDC exposures. There is substantial research on epigenomic modifications in offspring exposed to EDCs during gestation, and a growing number of studies evaluating the transcriptome, proteome, metabolome, or microbiome in response to these exposures. Multi-omics, integrating data across omics layers, may improve understanding of disrupted function pathways related to early life exposures. We highlight several data integration methods to consider in multi-omics studies. Information from multi-omics can improve understanding of the biological processes and mechanisms underlying prenatal EDC toxicity.

Per- and polyfluoroalkyl substances and sleep health in U.S. adults, NHANES 2005-2014

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that induce oxidative inflammatory responses and disrupt the endocrine and central nervous systems, all of which can influence sleep.

OBJECTIVE

To investigate the association between PFAS exposure and sleep health measures in U.S. adults.

METHODS

We analyzed serum concentration data of four PFAS [perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA)] reported for 8913 adults in NHANES 2005-2014. Sleep outcomes, including trouble sleeping, having a diagnosis of sleep disorder, and recent daily sleep duration classified as insufficient or excessive sleep (<6 or >9 h/day) were examined. Weighted logistic regression was used to estimate the association between the sleep outcomes and each PFAS modeled continuously (log2) or in exposure tertiles. We applied quantile g-computation to estimate the effect of the four PFAS as a mixture on the sleep outcomes. We conducted a quantitative bias analysis to assess the potential influence of self-selection and uncontrolled confounding.

RESULTS

We observed some inverse associations between serum PFAS and trouble sleeping or sleep disorder, which were more consistent for PFOS (e.g., per log2-PFOS (ng/ml) and trouble sleeping OR = 0.93, 95%CI: 0.89, 0.98; sleep disorder OR = 0.89, 95%CI: 0.83, 0.95). Per quartile increase of the PFAS mixture was inversely associated with trouble sleeping and sleep disorder. No consistent associations were found for sleep duration across analyses. Our bias analysis suggests that the finding on sleep disorder could be explained by a moderate level of self-selection and negative confounding effects.

CONCLUSIONS

We found no evidence to suggest exposure to four legacy PFAS worsened self-reported sleep health among U.S. adults. While some inverse associations between specific PFAS and sleep disorder were observed, self-selection and uncontrolled confounding biases may play a role in these findings.

Cross-sectional associations between prenatal maternal per- and poly-fluoroalkyl substances and bioactive lipids in three Environmental influences on Child Health Outcomes (ECHO) cohorts

Background

Per- and poly-fluoroalkyl substances (PFAS) exposure can occur through ingestion of contaminated food and water, and inhalation of indoor air contaminated with these chemicals from consumer and industrial products. Prenatal PFAS exposures may confer risk for pregnancy-related outcomes such as hypertensive and metabolic disorders, preterm birth, and impaired fetal development through intermediate metabolic and inflammation pathways.

Objective

Estimate associations between maternal pregnancy PFAS exposure (individually and as a mixture) and bioactive lipids.

Methods

Our study included pregnant women in the Environmental influences on Child Health Outcomes Program: Chemicals in our Bodies cohort (CiOB, n=73), Illinois Kids Developmental Study (IKIDS, n=287), and the ECHO-PROTECT cohort (n=54). We measured twelve PFAS in serum and 50 plasma bioactive lipids (parent fatty acids and eicosanoids derived from cytochrome p450, lipoxygenase, and cyclooxygenase) during pregnancy (median 17 gestational weeks). Pairwise associations across cohorts were estimated using linear mixed models and meta-analysis. Associations between the PFAS mixture and individual bioactive lipids were estimated using quantile g-computation.

Results

PFDeA, PFOA, and PFUdA were associated (p<0.05) with changes in bioactive lipid levels in all three enzymatic pathways (cyclooxygenase [n=6 signatures]; cytochrome p450 [n=5 signatures]; lipoxygenase [n=7 signatures]) in at least one combined cohort analysis. The strongest signature indicated that a doubling in PFOA corresponded with a 24.3% increase (95% CI [7.3%, 43.9%]) in PGD2 (cyclooxygenase pathway) in the combined cohort. In the mixtures analysis, we observed nine positive signals across all pathways associated with the PFAS mixture. The strongest signature indicated that a quartile increase in the PFAS mixture was associated with a 34% increase in PGD2 (95% CI [8%, 66%]), with PFOS contributing most to the increase.

Conclusions

Bioactive lipids were revealed as biomarkers of PFAS exposure and could provide mechanistic insights into PFAS' influence on pregnancy outcomes, informing more precise risk estimation and prevention strategies.

The plastic health map: A systematic evidence map of human health studies on plastic-associated chemicals

BACKGROUND

The global production and use of plastic materials has increased dramatically since the 1960s and there is increasing evidence of human health impacts related to exposure to plastic-associated chemicals. There is, however, no comprehensive, regulatory, post-market monitoring for human health effects of plastic-associated chemicals or particles and it is unclear how many of these have been investigated for effects in humans, and therefore what the knowledge gaps are.

OBJECTIVE

To create a systematic evidence map of peer-reviewed human studies investigating the potential effects of exposure to plastic-associated particles/chemicals on health to identify research gaps and provide recommendations for future research and regulation policy.

METHODS

Medline and Embase databases were used to identify peer-reviewed primary human studies published in English from Jan 1960 - Jan 2022 that investigated relationships between exposures to included plastic-associated particles/chemicals measured and detected in bio-samples and human health outcomes. Plastic-associated particles/chemicals included are: micro and nanoplastics, due to their widespread occurrence and potential for human exposure; polymers, the main building blocks of plastic; plasticizers and flame retardants, the two most common types of plastic additives with the highest concentration ranges in plastic materials; and bisphenols and per- or polyfluoroalkyl substances, two chemical classes of known health concern that are common in plastics. We extracted metadata on the population and study characteristics (country, intergenerational, sex, age, general/special exposure risk status, study design), exposure (plastic-associated particle/chemical, multiple exposures), and health outcome measures (biochemical, physiological, and/or clinical), from which we produced the interactive database 'Plastic Health Map' and a narrative summary.

RESULTS

We identified 100,949 unique articles, of which 3,587 met our inclusion criteria and were used to create a systematic evidence map. The Plastic Health Map with extracted metadata from included studies are freely available at https://osf.io/fhw7d/ and summary tables, plots and overall observations are included in this report.

CONCLUSIONS

We present the first evidence map compiling human health research on a wide range of plastic-associated chemicals from several different chemical classes, in order to provide stakeholders, including researchers, regulators, and concerned individuals, with an efficient way to access published literature on the matter and determine knowledge gaps. We also provide examples of data clusters to facilitate systematic reviews and research gaps to help direct future research efforts. Extensive gaps are identified in the breadth of populations, exposures and outcomes addressed in studies of potential human health effects of plastic-associated chemicals. No studies of the human health effects of micro and/or nanoplastics were found, and no studies were found for 26/1,202 additives included in our search that are of known hazard concern and confirmed to be in active production. Few studies have addressed recent "substitution" chemicals for restricted additives such as organophosphate flame retardants, phthalate substitutes, and bisphenol analogues. We call for a paradigm shift in chemical regulation whereby new plastic chemicals are rigorously tested for safety before being introduced in consumer products, with ongoing post-introduction biomonitoring of their levels in humans and health effects throughout individuals' life span, including in old age and across generations.

Bioaccumulation and metabolic impact of environmental PFAS residue on wild-caught urban wetland tiger snakes (Notechis scutatus)

PFAS contamination of urban waters is widespread but understanding the biological impact of its accumulation is limited to humans and common ecotoxicological model organisms. Here, we combine PFAS exposure and bioaccumulation patterns with whole organism responses and omics-based ecosurveillance methods to investigate the potential impacts of PFAS on a top predator of wetlands, the tiger snake (Notechis scutatus). Tiger snakes (18 male and 17 female) were collected from four wetlands with varying PFAS chemical profiles and concentrations in Perth, Western Australia. Tiger snake livers were tested for 28 known PFAS compounds, and Σ28PFAS in liver tissues ranged between 322 ± 193 μg/kg at the most contaminated site to 1.31 ± 0.86 μg/kg at the least contaminated site. The dominant PFAS compound detected in liver tissues was PFOS. Lower body condition was associated with higher liver PFAS, and male snakes showed signs of high bioaccumulation whereas females showed signs of maternal offloading. Biochemical profiles of snake muscle, fat (adipose tissue), and gonads were analysed using a combination of liquid chromatography triple quadrupole (QqQ) and quadrupole time-of-flight (QToF) mass spectrometry methodologies. Elevated PFAS was associated with enriched energy production and maintenance pathways in the muscle, and had weak associations with energy-related lipids in the fat tissue, and lipids associated with cellular genesis and spermatogenesis in the gonads. These findings demonstrate the bioavailability of urban wetland PFAS in higher-order reptilian predators and suggest a negative impact on snake health and metabolic processes. This research expands on omics-based ecosurveillance tools for informing mechanistic toxicology and contributes to our understanding of the impact of PFAS residue on wildlife health to improve risk management and regulation.

A metabolomic investigation of serum perfluorooctane sulfonate and perfluorooctanoate

BACKGROUND

Exposures to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), environmentally persistent chemicals detectable in the blood of most Americans, have been associated with several health outcomes. To offer insight into their possible biologic effects, we evaluated the metabolomic correlates of circulating PFOS and PFOA among 3,647 participants in eight nested case-control serum metabolomic profiling studies from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.

METHODS

Metabolomic profiling was conducted by Metabolon Inc., using ultra high-performance liquid chromatography/tandem accurate mass spectrometry. We conducted study-specific multivariable linear regression analyses estimating the associations of metabolite levels with levels of PFOS or PFOA. For metabolites measured in at least 3 of 8 nested case-control studies, random effects meta-analysis was used to summarize study-specific results (1,038 metabolites in PFOS analyses and 1,100 in PFOA analyses).

RESULTS

The meta-analysis identified 51 and 38 metabolites associated with PFOS and PFOA, respectively, at a Bonferroni-corrected significance level (4.8x10-5 and 4.6x10-5, respectively). For both PFOS and PFOA, the most common types of associated metabolites were lipids (sphingolipids, fatty acid metabolites) and xenobiotics (xanthine metabolites, chemicals). Positive associations were commonly observed with lipid metabolites sphingomyelin (d18:1/18:0) (P = 2.0x10-10 and 2.0x10-8, respectively), 3-carboxy-4-methyl-5-pentyl-2-furanpropionate (P = 2.7x10-15, 1.1x10-17), and lignoceroylcarnitine (C24) (P = 2.6x10-8, 6.2x10-6). The strongest positive associations were observed for chemicals 3,5-dichloro-2,6-dihydroxybenzoic acid (P = 3.0x10-112 and 6.8x10-13, respectively) and 3-bromo-5-chloro-2,6-dihydroxybenzoic acid (P = 1.6x10-14, 2.3x10-6). Other metabolites positively associated with PFOS included D-glucose (carbohydrate), carotene diol (vitamin A metabolism), and L-alpha-aminobutyric acid (glutathione metabolism), while uric acid (purine metabolite) was positively associated with PFOA. PFOS associations were consistent even after adjusting for PFOA as a covariate, while PFOA associations were greatly attenuated with PFOS adjustment.

CONCLUSIONS

In this large metabolomic study, we observed robust positive associations with PFOS for several molecules. Further investigation of these metabolites may offer insight into PFOS-related biologic effects.

Dose additive maternal and offspring effects of oral maternal exposure to a mixture of three PFAS (HFPO-DA, NBP2, PFOS) during pregnancy in the Sprague-Dawley rat

Simultaneous exposure to multiple per- and polyfluoroalkyl substances (PFAS) is common in humans across the globe. Individual PFAS are associated with adverse health effects, yet the nature of mixture effects after exposure to two or more PFAS remains unclear. Previously we reported that oral administration of hexafluoropropylene oxide-dimer acid (HFPO-DA, or GenX), Nafion byproduct 2 (NBP2), or perfluorooctane sulfonate (PFOS) individually during pregnancy produced maternal and F1 effects. Here, we hypothesized that responses to the combined exposure to these three PFAS would be dose additive. Pregnant Sprague-Dawley rats were exposed to a fixed-ratio equipotent mixture where the top dose contained each PFAS at their ED50 for neonatal mortality (100 % dose = PFOS 3 mg/kg; NBP2 10 mg/kg; HFPO-DA 110 mg/kg), followed by a dilution series (33.3, 10, 3.3, and 1 %) and vehicle controls (0 % dose). Consistent with the single chemical studies, dams were exposed from gestation day (GD)14-18 or from GD8-postnatal day (PND2). Fetal and maternal livers on GD18 displayed multiple significantly upregulated genes associated with lipid and carbohydrate metabolism at all dose levels, while dams displayed significantly increased liver weight (≥3.3 % dose) and reduced serum thyroid hormones (≥33.3 % dose). Maternal exposure from GD8-PND2 significantly reduced pup bodyweights at birth (≥33.3 % dose) and PND2 (all doses), increased neonatal liver weights (≥3.3 % dose), increased pup mortality (≥3.3 % dose), and reduced maternal bodyweights and weight gain at the top dose. Echocardiography of adult F1 males and females identified significantly increased left ventricular anterior wall thickness (~10 % increase), whereas other cardiac morphological, functional, and transcriptomic measures were unaffected. Mixture effects in maternal and neonatal animals conformed to dose addition using a relative potency factor (RPF) analysis. Results support dose addition-based cumulative assessment approaches for estimating combined effects of PFAS co-exposure.

PFAS Exposures and the Human Metabolome: A Systematic Review of Epidemiological Studies

Purpose of Review

There is a growing interest in understanding the health effects of exposure to per- and polyfluoroalkyl substances (PFAS) through the study of the human metabolome. In this systematic review, we aimed to identify consistent findings between PFAS and metabolomic signatures. We conducted a search matching specific keywords that was independently reviewed by two authors on two databases (EMBASE and PubMed) from their inception through July 19, 2022 following PRISMA guidelines.

Recent Findings

We identified a total of 28 eligible observational studies that evaluated the associations between 31 different PFAS exposures and metabolomics in humans. The most common exposure evaluated was legacy long-chain PFAS. Population sample sizes ranged from 40 to 1,105 participants at different stages across the lifespan. A total of 19 studies used a non-targeted metabolomics approach, 7 used targeted approaches, and 2 included both. The majority of studies were cross-sectional (n = 25), including four with prospective analyses of PFAS measured prior to metabolomics.

Summary

Most frequently reported associations across studies were observed between PFAS and amino acids, fatty acids, glycerophospholipids, glycerolipids, phosphosphingolipids, bile acids, ceramides, purines, and acylcarnitines. Corresponding metabolic pathways were also altered, including lipid, amino acid, carbohydrate, nucleotide, energy metabolism, glycan biosynthesis and metabolism, and metabolism of cofactors and vitamins. We found consistent evidence across studies indicating PFAS-induced alterations in lipid and amino acid metabolites, which may be involved in energy and cell membrane disruption.

Domestic Dogs and Horses as Sentinels of Per- and Polyfluoroalkyl Substance Exposure and Associated Health Biomarkers in Gray's Creek North Carolina

Central North Carolina (NC) is highly contaminated with per- and polyfluoroalkyl substances (PFAS), in part due to local fluorochemical production. Little is known about the exposure profiles and long-term health impacts for humans and animals that live in nearby communities. In this study, serum PFAS concentrations were determined using liquid chromatography high-resolution mass spectrometry and diagnostic clinical chemistry endpoints were assessed for 31 dogs and 32 horses that reside in Gray's Creek NC at households with documented PFAS contamination in their drinking water. PFAS were detected in every sample, with 12 of the 20 PFAS detected in ≥50% of samples from each species. The average total PFAS concentrations in horses were lower compared to dogs who had higher concentrations of PFOS (dogs 2.9 ng/mL; horses 1.8 ng/mL), PFHxS (dogs 1.43 ng/mL, horses < LOD), and PFOA (dogs 0.37 ng/mL; horses 0.10 ng/mL). Regression analysis highlighted alkaline phosphatase, glucose, and globulin proteins in dogs and gamma glutamyl transferase in horses as potential biomarkers associated with PFAS exposure. Overall, the results of this study support the utility of companion animal and livestock species as sentinels of PFAS exposure differences inside and outside of the home. As in humans, renal and hepatic health in domestic animals may be sensitive to long-term PFAS exposures.

Integrating -omics approaches into population-based studies of endocrine disrupting chemicals: A scoping review

Health effects of endocrine disrupting chemicals (EDCs) are challenging to detect in the general population. Omics technologies become increasingly common to identify early biological changes before the apparition of clinical symptoms, to explore toxic mechanisms and to increase biological plausibility of epidemiological associations. This scoping review systematically summarises the application of omics in epidemiological studies assessing EDCs-associated biological effects to identify potential gaps and priorities for future research. Ninety-eight human studies (2004-2021) were identified through database searches (PubMed, Scopus) and citation chaining and focused on phthalates (34 studies), phenols (19) and PFASs (17), while PAHs (12) and recently-used pesticides (3) were less studied. The sample sizes ranged from 10 to 12,476 (median = 159), involving non-pregnant adults (38), pregnant women (11), children/adolescents (15) or both latter populations studied together (23). Several studies included occupational workers (10) and/or highly exposed groups (11) focusing on PAHs, PFASs and pesticides, while studies on phenols and phthalates were performed in the general population only. Analysed omics layers included metabolic profiles (30, including 14 targeted analyses), miRNA (13), gene expression (11), DNA methylation (8), microbiome (5) and proteins (3). Twenty-one studies implemented targeted multi-assays focusing on clinical routine blood lipid traits, oxidative stress or hormones. Overall, DNA methylation and gene expression associations with EDCs did not overlap across studies, while some EDC-associated metabolite groups, such as carnitines, nucleotides and amino acids in untargeted metabolomic studies, and oxidative stress markers in targeted studies, were consistent across studies. Studies had common limitations such as small sample sizes, cross-sectional designs and single sampling for exposure biomonitoring. In conclusion, there is a growing body of evidence evaluating the early biological responses to exposure to EDCs. This review points to a need for larger longitudinal studies, wider coverage of exposures and biomarkers, replication studies and standardisation of research methods and reporting.

Effects of Perfluorooctanoic Acid on Gut Microbiota and Microbial Metabolites in C57BL/6J Mice

Perfluorooctanoic acid (PFOA) represents an increasing public health concern due to its persistence in the environment and its toxic effects. The gut microbiota is known to produce various metabolites that assist the host to maintain metabolic homeostasis. However, few studies have explored the effects of PFOA on gut-microbiota-related metabolites. In the present study, male C57BL/6J mice were exposed to 1 ppm of PFOA in drinking water for four weeks and integrative analysis of the gut microbiome and metabolome was performed to reveal the health effects of PFOA. Our results showed that PFOA disturbed both the gut microbiota composition and the metabolic profiles of the feces, serum, and liver in mice. A correlation was found between Lachnospiraceae UCG004, Turicibacter, Ruminococcaceae, and different fecal metabolites. Significant alterations of gut-microbiota-related metabolites were induced by PFOA exposure, including bile acids and tryptophan metabolites such as 3-indoleacrylic acid and 3-indoleacetic acid. The findings of this study are helpful to improve the understanding of the health effects of PFOA, which might be mediated through the gut microbiota and its related metabolites.