The association between per-/polyfluoroalkyl substances in serum and thyroid function parameters: A cross-sectional study on teenagers living near a Chinese fluorochemical industrial plant

Thyroid hormones (THs) play an important role in a wide range of crucial biological functions related to growth and development, and thyroid antibodies (TAs) can influence the biosynthesis of THs. Epidemiological studies have indicated that per- and polyfluoroalkyl substances (PFAS) could induce thyroid disruption, but studies on teenagers living in areas with high PFAS exposure are limited. This cross-sectional study focused on 836 teenagers (11- 15 years) living near a Chinese fluorochemical industrial plant. Decreased levels of free thyroxine (FT4, ﹤9.6 pmol/L, abnormal rate = 19.0 %) and elevated levels of free triiodothyronine (FT3, ﹥6.15 pmol/L, abnormal rate = 29.8 %) were observed. Correlations of serum PFAS concentrations and TAs/THs were analyzed. Increased PFOA was identified as a risk factor of decreased FT4 by using unadjusted (OR: 11.346; 95 % CI: 6.029, 21.352, p < 0.001) and adjusted (OR: 12.566; 95 % CI: 6.549, 24.115, p < 0.001) logistic regression models. In addition, significantly negative correlations were found between log10 transformed PFOA and FT4 levels using linear (unadjusted: β = -1.543, 95 % CI: -1.937, -1.148, p < 0.001; adjusted: β = -1.534, 95 % CI: -1.930, -1.137, p < 0.001) and BKMR models. For abnormal FT3, a significantly positive association between PFHxS and FT3 levels was observed in a regression model (unadjusted: β = -0.903, 95 % CI: -1.212, -0.595, p < 0.001; adjusted: β = -0.894, 95 % CI: -1.204, -0.583, p < 0.001), and PFHxS was identified as a risk factor (unadjusted: OR: 4.387; 95 % CI: 2.619, 7.346, p < 0.001; adjusted: OR: 4.527; 95 % CI: 2.665, 7.688, p < 0.001). Sensitivity analyses confirmed the robustness of the above results. This study reported the elevated PFAS exposure and thyroid function of teenagers living near a fluorochemical industrial plant from China.

Per- and Polyfluoroalkyl Substances: Impacts on Morphology, Behavior and Lipid Levels in Zebrafish Embryos

The presence of per- and polyfluoroalkyl substances (PFASs) in aquatic environments is often persistent and widespread. Understanding the potential adverse effects from this group of chemicals on aquatic communities allows for better hazard characterization. This study examines impacts on zebrafish (Danio rerio) embryo physiology, behavior, and lipid levels from exposure to perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), and heptadecafluorooctanesulfonic acid (PFOS). Embryos were exposed to lethal and sublethal levels of each chemical and monitored for alterations in physiological malformations, mortality, lipid levels, and behavior (only PFOA and PFHxS). The predicted 50% lethal concentrations for 120 hpf embryos were 528.6 ppm PFOA, 14.28 ppm PFHxS, and 2.14 ppm PFOS. Spine curvature and the inability of the 120 hpf embryos to maintain a dorsal-up orientation was significantly increased at 10.2 ppm PFHxS and 1.9 ppm PFOS exposure. All measured 120 hpf embryo behaviors were significantly altered starting at the lowest levels tested, 188 ppm PFOA and 6.4 ppm PFHxS. Lipid levels decreased at the highest PFAS levels tested (375 PFOA ppm, 14.4 PFHxS ppm, 2.42 ppm PFOS). In general, the PFAS chemicals, at the levels examined in this study, increased morphological deformities, embryo activity, and startle response time, as well as decreased lipid levels in 120 hpf zebrafish embryos.

The Association of Hypertension with Perfluoroalkyl and Polyfluoroalkyl Substances

Perfluoroalkyl and polyfluoroalkyl substance (PFAS) is a large group of fluorinated synthetic chemicals, e.g., perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorodecanoic acid (PFDA), and perfluorononanoic acid (PFNA). Many epidemiological studies have found that PFAS exposure is associated with hypertension risk, but others possess a different opinion. Overall, the relationship between PFASs and hypertension risk remains controversial. We sought to conduct a systematic review and meta-analysis to clarify the association between PFAS exposure and human risk of hypertension.We conducted a meta-analysis based on population-involving studies published from 1975 to 2023, which we collected from Web of Science, PubMed, and Embase databases. The odds ratio (OR) and standardized mean difference (SMD), with their 95% confidence interval (CI), were used to assess the risk of hypertension with PFAS exposure. The statistical heterogeneity among studies was assessed with the Q-test and I2 statistics. Research publications related to our meta-analysis topic were systematically reviewed.Fourteen studies involving 71,663 participants, in which 26,281 suffered hypertension, met the inclusion criteria. Our analyses suggest that exposure to general PFAS (OR = 1.09, 95% CI = 1.04-1.14) or PFOS (OR = 1.17, 95% CI = 1.05-1.30) is associated with hypertension risk. Specifically, elevated levels of general PFAS (SMD = 0.25, 95% CI = 0.08-0.42), PFHxS (SMD = 0.17, 95% CI = 0.07-0.27), and PFDA (SMD = 0.08, 95% CI = 0.02-0.13) are associated with a high risk of hypertension.Our meta-analysis indicates that PFAS exposure is a risk factor for hypertension, and increased hypertension risk is associated with higher PFAS levels. Further study may eventually provide a better and more comprehensive elucidation of the potential mechanism of this association.

Reproductive and immune effects emerge at similar thresholds of PFHxS in deer mice

Although perfluorohexane sulfonate (PFHxS) is structurally similar to perfluorooctane sulfonate (PFOS) and also widely detected in humans and the environment, comparatively fewer toxicity data exists on this 6-chain perfluoroalkyl sulfonic acid. In this study, repeated oral doses of PFHxS were administered to deer mice (Peromyscus maniculatus) to evaluate subchronic toxicity and potential effects on reproduction and development. Maternal oral exposure to PFHxS caused increased stillbirths, which is relevant for ecological risk assessment, and resulted in a benchmark dose lower limit (BMDL) of 5.72 mg/kg-d PFHxS. Decreased plaque formation, which is relevant for human health risk assessment, occurred in both sexes of adult animals (BMDL = 8.79 mg/kg-d PFHxS). These data are the first to suggest a direct link between PFHxS and decreased functional immunity in an animal model. Additionally, female animals exhibited increased liver:body weight and animals of both sexes exhibited decreased serum thyroxine (T4) levels. Notably, since reproductive effects were used to support 2016 draft health advisories and immune effects were used in 2022 drinking water health advisories released by the United States Environmental Protection Agency for PFOS and perfluorooctanoic acid (PFOA), these novel data can potentially support advisories for PFHxS because relevant points of departure emerge at similar thresholds in a wild mammal and corroborate the general understanding of per- and polyfluoroalkyl substances (PFAS).

Temporal decline in serum PFAS concentrations among metropolitan firefighters: Longitudinal study on post-exposure changes following PFAS foam cessation

Firefighters are at a high risk of exposure to per- and polyfluoroalkyl substances (PFAS) due to their frequent use of PFAS-containing foams in training and emergency situations. This longitudinal study aimed to investigate the changes in serum PFAS levels among firefighters following cessation of their exposure to PFAS-containing foams. The study involved 130 firefighters from the South Australian Metropolitan Fire Services (SAMFS), and serum samples were collected at two time points: baseline in 2018-19 and follow-up in 2021-22. Along with the collection of samples, a survey questionnaire was administered to gather information on firefighters' employment and demographic characteristics. Regression models were employed to assess the association between these factors and the outcome variable (annual percentage change in serum PFAS concentration). The results indicated a decline in serum PFAS concentrations over time, with the main contaminants being perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA). The median and Interquartile Range (IQR) of total PFAS (∑PFAS) concentration reduced from 21.5 ng/ml (IQR: 11 to 53 ng/ml) at baseline to 15 ng/ml (IQR: 8 to 33 ng/ml) at follow-up. On average, there was an annual reduction of 13%, 7%, and 4.4% in serum concentrations of PFOS, PFHxS, and PFOA, respectively. Firefighters under the age of 55, those who used PFAS in the past ten years, or those who had little to no frequency of PFAS exposure in their previous employment, encountered a significantly higher annual percentage reduction (P < 0.05) in both ∑PFAS and PFOS concentrations. None of the independent variables analysed could significantly predict the annual percentage change in PFOA and PFHxS. This study provides evidence for a declining temporal trend in serum PFAS concentrations among metropolitan firefighters following workplace interventions that involved the removal of PFAS-containing foams.

Developmental toxicity of perfluorohexane sulfonate at human relevant dose during pregnancy via disruption in placental lipid homeostasis

Perfluorohexyl sulfonate (PFHxS) is the third most abundant per- and polyfluoroalkyl substances and its developmental toxicity remains very poorly understood. Here, pregnant mice exposed to PFHxS at human relevant dose showed increased fetal death incidence in the high-dose PFHxS-H group (P < 0.01). Body distribution analyses suggested that PFHxS crossed the placental barrier reaching the fetus in a dose-dependent manner. Histopathological data demonstrated impairment in the placenta with reduced blood sinus volume, placental labyrinth area as well as thickness of labyrinthine layer. Further lipidomic and transcriptomic data together showed that PFHxS exposure caused significant disruption in placental lipid homeostasis, including total lipid accumulation in the placenta, and dysregulation in phospholipid and glycerol lipid metabolism. Gene expression analyses uncovered elevation in key placental fatty acid transporters including fabp2, whereas protein expression showed transporter specific disruptions following exposure. Together, gestational exposure to human relevant level of PFHxS may increase the incidence of fetal deaths and caused placental dysplasia via disruption in lipid metabolism homeostasis. These findings raise the concern regarding the highly prevalent and persistent chemical towards early sensitive developing stages and provide basis for further understanding of its effects on lipid metabolism and underlying mechanisms.

Determinants of maternal and neonatal PFAS concentrations: a review

Per- and polyfluoroalkyl substances (PFAS) are used for their properties such as stain and water resistance. The substances have been associated with adverse health outcomes in both pregnant mothers and infants, including pre-eclampsia and low birthweight. A growing body of research suggests that PFAS are transferred from mother to fetus through the placenta, leading to in utero exposure. A systematic review was performed using the PubMed database to search for studies evaluating determinants of PFAS concentrations in blood matrices of pregnant mothers and neonates shortly after birth. Studies were included in this review if an observational study design was utilized, exposure to at least one PFAS analyte was measured, PFAS were measured in maternal or neonatal matrices, at least one determinant of PFAS concentrations was assessed, and results such as beta estimates were provided. We identified 35 studies for inclusion in the review and evaluated the PFAS and determinant relationships among the factors collected in these studies. Parity, breastfeeding history, maternal race and country of origin, and household income had the strongest and most consistent evidence to support their roles as determinants of certain PFAS concentrations in pregnant mothers. Reported study findings on smoking status, alcohol consumption, and pre-pregnancy body mass index (BMI) suggest that these factors are not important determinants of PFAS concentrations in pregnant mothers or neonates. Further study into informative factors such as consumer product use, detailed dietary information, and consumed water sources as potential determinants of maternal or neonatal PFAS concentrations is needed. Research on determinants of maternal or neonatal PFAS concentrations is critical to estimate past PFAS exposure, build improved exposure models, and further our understanding on dose-response relationships, which can influence epidemiological studies and risk assessment evaluations. Given the potential for adverse outcomes in pregnant mothers and neonates exposed to PFAS, it is important to identify and understand determinants of maternal and neonatal PFAS concentrations to better implement public health interventions in these populations.

Perfluorohexane sulfonate (PFHxS) disturbs the estrous cycle, ovulation rate, oocyte cell communication and calcium homeostasis in mice

Perfluoroalkyl substances are man-made chemicals with ample consumer and industrial applications. They are widely used and are resistant to environmental and metabolic degradation. Several studies have evaluated the effects of Perfluorohexane sulfonate on reproduction. However, there are few reports exploring the cell and molecular mechanisms of its toxicity in the ovary. The aim of this study was to investigate the effects of PFHxS exposure on the estrous cycle, ovulation rate, and the underlying mechanisms of action in female mice in vivo. The animals received a single sub-lethal dose of PFHxS (25.1 mg/kg, 62.5 mg/kg) or vehicle and were stimulated to obtain immature cumulus cell-oocyte complexes (COCs) from the ovaries, or superovulated to develop mature COCs. To evaluate oocyte physiology, Gap-junction intercellular communication (GJIC) was analyzed in immature COCs and calcium homeostasis was evaluated in mature oocytes. PFHxS exposure prolonged the estrous cycle and decreased ovulation rate in female mice. Connexins, Cx43 and Cx37, were downregulated and GJIC was impaired in immature COCs, providing a possible mechanism for the alterations in the estrous cycle and ovulation. No morphological abnormalities were observed in the mature PFHxS-exposed oocytes, but calcium homeostasis was affected. This effect is probably due, at least partially, to deregulation of the endoplasmic reticulum calcium modulator, Stim1. These mechanisms of ovarian injury could explain the reported correlation among PFHxS levels and subfertility in women undergoing fertility treatments.

A comprehensive untargeted metabolomics study in zebrafish embryos exposed to perfluorohexane sulfonate (PFHxS)

Perfluorohexane sulfonate (PFHxS) is one of the short-chain perfluoroalkyl substances (PFASs), and frequently detected in the environment, humans, and wildlife, but a detailed mechanism of toxicity has been not studied yet. In this study, a comprehensive set of polar metabolites was determined in i) the developing zebrafish embryo (4, 24, 48, 72, and 120 h post fertilization (hpf)), and ii) in the developing zebrafish after exposure to four concentrations of PFHxS (0.3, 1, 3, and 10 μM) from 24to 120 hpf. The temporal (developmental stages) distribution of individual metabolites (541 metabolites) in zebrafish provided comprehensive information about the biological roles of various metabolites in developing vertebrates such as genetic processes, energy metabolism, protein metabolism, and glycerophospholipid metabolism. PFHxS in zebrafish embryo showed time- and concentration- dependent bioaccumulation, and no baseline toxicity was expected at the test concentrations. However, effects on many metabolites were already observed at the lowest tested concentration (0.3 μM), and these effects were more pronounced at later stages of developmental (72 and 120 hpf). In addition to oxidative stress, the effects of PFHxS on zebrafish embryos were related to the disruption of the fatty acid oxidation (FAO), sugar metabolism, and other metabolic pathways. This study gave new and comprehensive information on the underlying mechanism of the toxicity of PFHxS.

Perfluoroalkyl substances exposure in firefighters: Sources and implications

Firefighters are at risk of occupational exposure to long-chain per- and poly-fluoroalkyl substances (PFASs), most notably from PFASs present in Class B aqueous film-forming foam (AFFF). Firefighters have been found to have elevated serum levels of long-chain PFASs. Due to the persistence of PFAS chemicals in the human body and their ability to bioaccumulate, firefighters experience the latent and cumulative effects of PFAS-containing AFFF exposure that occurs throughout their careers. This article summarizes the history of AFFF use by firefighters and current AFFF use practices. In addition, this paper describes PFAS levels in firefighter serum, PFAS serum removal pathways, PFAS exposure pathways, and occupational factors affecting PFAS levels in firefighters. International, national, and state agencies have concluded that PFOA, a long-chain PFAS, is potentially carcinogenic and that carcinogens have an additive effect. From the cancer types that may be associated with PFAS exposure, studies on cancer risk among firefighters have shown an elevated risk for thyroid, kidney, bladder, testicular, prostate, and colon cancer. Thus, exposure to PFAS-containing AFFF may contribute to firefighter cancer risk and warrants further research.

Per- and polyfluoroalkyl substances (PFAS) in breast milk and infant formula: A global issue

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are transferred from mother to infants through breastfeeding, a time when children may be particularly vulnerable to PFAS-mediated adverse health effects. Infants can also be exposed to PFAS from infant formula consumption. Our recent literature-based scoping of breast milk levels reported that four PFAS often exceeded the United States Agency for Toxic Substances and Disease Registry (ATSDR) children's drinking water screening levels in both the general population and highly impacted communities in the U.S. and Canada. This work presents a comparison of global breast milk and infant formula PFAS measurements with the only reported health-based drinking water screening values specific to children.

METHODS

We focused on four PFAS for which ATSDR has developed children's drinking water screening values: PFOA (perfluorooctanoic acid), PFOS (perfluorooctanesulfonic acid), PFHxS (perfluorohexanesulfonic acid), and PFNA (perfluorononanoic acid). Published literature on PFAS levels in breast milk and infant formula were identified via PubMed searches. Data were compared to children's drinking water screening values.

DISCUSSION

Breast milk concentrations of PFOA and PFOS often exceed children's drinking water screening values, regardless of geographic location. The limited information on infant formula suggests its use does not necessarily result in lower PFAS exposures, especially for formulas reconstituted with drinking water containing PFAS. Unfortunately, individuals generally cannot know whether their infant's exposures exceed children's drinking water screening values. Thus, it is essential that pregnant and lactating women and others, especially those having lived in PFAS-contaminated communities, have data required to make informed decisions on infant nutrition. An international monitoring effort and access to affordable testing are needed for breast milk, drinking water and infant formula to fully understand infant PFAS exposures. Currently, our understanding of demonstrable methods for reducing exposures to emerging PFAS is limited, making this research and the communications surrounding it even more important.

Calibration of Perfluorinated Alkyl Acid Uptake Rates by a Tube Passive Sampler in Water

Per- and polyfluoroalkyl substances (PFAS) are a group of 4000+ man-made compounds of great concern due to their environmental ubiquity and adverse effects. Despite a general interest, few reliable detection tools for integrative passive sampling of PFAS in water are available. A microporous polyethylene tube with a hydrophilic-lipophilic balance sorbent could serve as a flow-resistant passive sampler for PFAS. The tube's sampling rate, Rs, was predicted based on either partitioning and diffusion, or solely diffusion. At 15 °C, the laboratory measured Rs for perfluorohexanoic acid of 100+/-81 mL day-1 were better predicted by a partitioning and diffusion model (48+/-1.8 mL day-1) across 10-60 cm s-1 water flow speeds (15+/-4.2 mL day-1 diffusion only). For perfluorohexane sulfonate, Rs at 15°C were similarly different (110+/-60 mL day-1 measured, 120+/- 63 versus 12+/-3.4 mL day-1 in respective models). Rs values from field deployments were in-between these estimates (46 +/-40 mL day-1 for perfluorohexanoic acid). PFAS uptake was not different for previously biofouled membranes in the laboratory, suggesting the general applicability of the sampler in environmental conditions. This research demonstrates that the polyethylene tube's sampling rates are sensitive to the parameterization of the models used here and partitioning-derived values should be used.

Plasma and Skin Per- and Polyfluoroalkyl Substance (PFAS) Levels in Dairy Cattle with Lifetime Exposures to PFAS-Contaminated Drinking Water and Feed

Plasma and ear notch samples were removed from 164 Holstein cows and heifers, which had lifetime exposures to per- and polyfluoroalkyl substances (PFAS) through consumption of contaminated feed and water sources. A suite of nine PFAS including five perfluoroalkyl carboxylic acids (PFCA) and four perfluoroalkyl sulfonic acids (PFSA) was quantified in plasma and ear notch samples by liquid chromatography-mass spectrometry. Bioaccumulation of four- to nine-carbon PFCAs did not occur in plasma or skin, but PFSAs longer than four carbons accumulated in both plasma and skin. Exposure periods of at least 1 year were necessary for PFSAs to reach steady-state concentrations in plasma. Neither parity (P = 0.76) nor lactation status (P = 0.30) affected total PFSA concentrations in mature cow plasma. In contrast, lactation status greatly affected (P < 0.0001) total PFSA concentrations in ear notch samples. Skin samples could be used for biomonitoring purposes in instances when on-farm blood collection and plasma preparation are not practical.

Reduced Birth Weight and Exposure to Per- and Polyfluoroalkyl Substances: A Review of Possible Underlying Mechanisms Using the AOP-HelpFinder

Prenatal exposure to per- and polyfluorinated substances (PFAS) may impair fetal growth. Our knowledge of the underlying mechanisms is incomplete. We used the Adverse Outcome Pathway (AOP)-helpFinder tool to search PubMed for studies published until March 2021 that examined PFAS exposure in relation to birth weight, oxidative stress, hormones/hormone receptors, or growth signaling pathways. Of these 1880 articles, 106 experimental studies remained after abstract screening. One clear finding is that PFAS are associated with oxidative stress in in vivo animal studies and in vitro studies. It appears that PFAS-induced reactive-oxygen species (ROS) generation triggers increased peroxisome proliferator-activated receptor (PPAR)γ expression and activation of growth signaling pathways, leading to hyperdifferentiation of pre-adipocytes. Fewer proliferating pre-adipocytes result in lower adipose tissue weight and in this way may reduce birth weight. PFAS may also impair fetal growth through endocrine effects. Estrogenic effects have been noted in in vivo and in vitro studies. Overall, data suggest thyroid-damaging effects of PFAS affecting thyroid hormones, thyroid hormone gene expression, and histology that are associated in animal studies with decreased body and organ weight. The effects of PFAS on the complex relationships between oxidative stress, endocrine system function, adipogenesis, and fetal growth should be further explored.

Predicting Exposure to Perfluorinated Alkyl Substances (PFAS) among US Infants

PFASs have been detected in nearly every serum sample collected over the last two decades from US adults as part of the National Health and Nutrition Examination Survey (NHANES) and are commonly found in other data sets from around the world. However, less is known about infant PFAS exposures, primarily because the collection of infant serum samples is less common and frequently avoided. Cord blood samples are often preferred for chemical exposure assessments because this is thought to provide a good representation of infant serum concentrations, at least at the time of birth. In this paper, we will provide a statistical and probabilistic analysis of what can be expected for infants living in the US using NHANES from 2007 to 2008, which contains a rare subset of infant data. Regulatory efforts that require estimation of exposures among the very youth can be challenging, both because of a lack of data in general and because variability among this most vulnerable population can be uncertain. We report that US infant exposures are extremely common and that serum concentrations remain fairly constant, despite infant growth rates and relatively high caloric and fluid intake, with the possible exception of PFOS. Infant serum PFOS concentrations between months 1 and 3 are consistently higher than at less than one month, even though healthy infants at 1 and 2 months weigh more than they did at birth. This suggests that the babies are exposed to greater concentrations of PFOS after birth or that excretion kinetics differ for this PFAS.

Agonistic and potentiating effects of perfluoroalkyl substances (PFAS) on the Atlantic cod (Gadus morhua) peroxisome proliferator-activated receptors (Ppars)

Toxicity mediated by per- and polyfluoroalkyl substances (PFAS), and especially perfluoroalkyl acids (PFAAs), has been linked to activation of peroxisome proliferator-activated receptors (Ppar) in many vertebrates. Here, we present the primary structures, phylogeny, and tissue-specific distributions of the Atlantic cod (Gadus morhua) gmPpara1, gmPpara2, gmPparb, and gmPparg, and demonstrate that the carboxylic acids PFHxA, PFOA, PFNA, as well as the sulfonic acid PFHxS, activate gmPpara1 in vitro, which was also supported by in silico analyses. Intriguingly, a binary mixture of PFOA and the non-activating PFOS produced a higher activation of gmPpara1 compared to PFOA alone, suggesting that PFOS has a potentiating effect on receptor activation. Supporting the experimental data, docking and molecular dynamics simulations of single and double-ligand complexes led to the identification of a putative allosteric binding site, which upon binding of PFOS stabilizes an active conformation of gmPpara1. Notably, binary exposures of gmPpara1, gmPpara2, and gmPparb to model-agonists and PFAAs produced similar potentiating effects. This study provides novel mechanistic insights into how PFAAs may modulate the Ppar signaling pathway by either binding the canonical ligand-binding pocket or by interacting with an allosteric binding site. Thus, individual PFAAs, or mixtures, could potentially modulate the Ppar-signaling pathway in Atlantic cod by interfering with at least one gmPpar subtype.

Using comprehensive lipid profiling to study effects of PFHxS during different stages of early zebrafish development

PFHxS (Perfluorohexane sulfonic acid) is one of the short-chain perfluoroalkyl substances (PFASs) which are widely used in many industrial and consumer applications. However, limited information is available on the molecular mechanism of PFHxS toxicity (e.g. lipid metabolism). This study provides in-depth information on the lipid regulation of zebrafish embryos with and without PFHxS exposure. Lipid changes throughout zebrafish development (4 to 120 h post fertilization (hpf)) were closely associated with lipid species and lipid composition (fatty acyl chains). A comprehensive lipid analysis of four different PFHxS exposures (0, 0.3, 1, 3, and 10 μM) at different zebrafish developmental stages (24, 48, 72, and 120 hpf) was performed. Data on exposure concentration, lipids, and developmental stage showed that all PFHxS concentrations dysregulated the lipid metabolism and these were developmental-dependent. The pattern of significantly changed lipids revealed that PFHxS caused effects related to oxidative stress, inflammation, and impaired fatty acid β-oxidation. Oxidative stress and inflammation caused the remodeling of glycerophospholipid (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)), with increased incorporation of omega-3 PUFA and a decreased incorporation of omega-6 PUFA.

High in Utero Exposure to Perfluoroalkyl Substances from Drinking Water and Birth Weight: A Cohort Study among Infants in Ronneby, Sweden

In 2013, the drinking water for one-third of the households in Ronneby, Sweden, was found to be contaminated by perfluorinated alkyl substances (PFAS, >10,000 ng/L) from Aqueous Film Forming Foam (AFFF). In utero PFAS exposure can influence birth weight, but little is known about the effects at very high levels. This study aimed to examine the association between in utero PFAS exposure and birth weight. Infants with mothers from Ronneby exposed to contaminated water at home (high exposure) and infants with mothers from Ronneby not exposed to contaminated water at home (low exposure) were compared to infants with mothers from Blekinge county excluding Ronneby (referents). All infants born in Blekinge county 1995–2013 were included (n = 30,360). Differences in birth weight were only seen among infants born after 2005. For boys, Ronneby high exposure had a lower mean birth weight than referents (−54 g, 95% CI −97; −11). For girls, Ronneby high exposure had a higher mean birth weight than referents (47 g, 95% CI 4; 90). There were no differences in birth weight between referents and Ronneby low exposure. In conclusion, high exposure to PFAS may influence birth weight in a sex-specific way, although the effect estimates were relatively small.

Perfluoroalkyl substances (PFAS) in drinking water and risk for polycystic ovarian syndrome, uterine leiomyoma, and endometriosis: A Swedish cohort study

BACKGROUND

Perfluorinated substances (PFAS) are chemicals with endocrine disruptive properties that may interfere with the female reproductive system. However, few studies have explored the association between benign gynecological diseases and high PFAS exposure.

OBJECTIVES

The aim of this study was to investigate the possible associations between PFAS exposure and subsequent diagnosis of polycystic ovarian syndrome (PCOS), uterine leiomyoma (fibroids), and endometriosis in a cohort exposed to PFAS through drinking water.

MATERIAL AND METHODS

In 2013, high levels (with sum of PFAS above 10,000 ng/L), dominated by perfluorooctanesulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS), were found in the drinking water from one of the two waterworks in Ronneby, Sweden. The contamination came from firefighting foams used at a nearby airfield. Females of all ages (n = 29,106) who had ever resided in the municipality between 1985 and 2013 formed a cohort. Individual exposure was assessed based on municipality waterworks distribution data linked to annual residential address data; 27% of the females had ever lived at an address with PFAS-contaminated water. Gynecological health outcomes were retrieved from the Swedish National Patient Register. The Cox proportional hazards model was used to estimate the association between exposure and each diagnosis.

RESULTS

There were in all 161 cases of PCOS, 1,122 cases of uterine leiomyoma, and 373 cases of endometriosis. In women aged 20-50 years (n = 18,503), those with the highest estimated PFAS exposure had increased hazard ratios (HR) for PCOS (HR = 2.18; 95% confidence interval (CI) 1.43, 3.34) and uterine leiomyoma (HR = 1.28; 95% CI 0.95, 1.74). No increased HR for endometriosis was found (HR = 0.74; 95% CI 0.42, 1.29).

CONCLUSIONS

Exposure to high levels of PFAS in drinking water was associated with increased risk of PCOS and possibly uterine leiomyoma, but not endometriosis. The findings for PCOS are consistent with prior studies reporting positive associations between PCOS and PFAS exposure at background levels.

Multi- and trans-generational disturbances of perfluorobutane sulfonate and perfluorohexane sulfonate on lipid metabolism in Caenorhabditis elegans

Short-chained perfluorobutane sulfonate (PFBS, four-carbon) and perfluorohexane sulfonate (PFHxS, six-carbon) are widely employed to substitute long-chained per- and poly-fluoroalkyl substances (PFASs). Recent studies showed the potential persistence of PFBS and PFHxS, and also reported their correlation with obesity. However, the long-term outcome and underlying mechanisms remained poorly understood. Presently, the effects of PFBS and PFHxS were studied on C. elegans with multi- and trans-generational experiments. The multi-generational effects were measured in continuous four generational exposure (i.e., F1 to F4). Results showed that PFBS did not stimulate the fat content in F1 but in F4 with continuous but different disturbances on the lipid metabolism and the insulin and insulin-like (IIS) pathway. PFHxS stimulated the fat content in F1 and F4 with similar disturbances on the lipid metabolism and IIS pathway. The trans-generational results showed that the effects of PFBS and PFHxS on the lipid metabolism and IIS pathway were not totally recovered in the offspring of F1 (i.e., T1-T3) and F4 (i.e., T1'-T3') which were not continuously exposed. PFHxS showed a common pattern to up-regulate daf-7 in both multi- and trans-generational effects. The long-term consequences of the short-chained PFASs substitutes should be concerned and epigenetic regulations should be considered in future mechanism studies.

Serum concentrations of per-/polyfluoroalkyl substances and risk of type 2 diabetes: A case-control study

Per-/polyfluoroalkyl substances (PFASs), as a group of synthetic chemicals, have been extensively detected in human samples. Recently, epidemiological investigations have reported relationships between exposure to PFASs with risk of type 2 diabetes mellitus (T2DM), but with contradictory results. In this study, a case-control study was conducted to explore associations between serum PFASs and T2DM risk among 252 T2DM cases and 252 controls, who were both diagnosed according to fasting glucose and glycosylated hemoglobin levels. Besides, dose-response relationships were analyzed to clarify effects of PFAS exposure on T2DM risk at different exposure levels. Multivariable logistic regression models showed that compared to the lowest tertiles, elevated odds of T2DM risk were observed in the middle tertiles of perfluorohexane sulfonic acid (PFHxS) [odds ratio (OR): 4.09; 95% confidence interval (CI): 2.23, 7.50; p < 0.01] and perfluorohexane sulfonic acid (PFHpA) (OR: 1.87; 95% CI: 1.06, 3.29; p = 0.03), but not in the highest tertiles, and the restricted cubic spline regression models presented inverted U-shaped dose-response relationships for exposure to PFHxS and PFHpA with T2DM risk, indicating non-monotonic dose-response effect and low-dose effect. Most other PFASs were inversely associated with risk of T2DM, especially at higher exposure levels. Our findings suggested that there are associations between exposure to PFASs and risk of T2DM. Further mechanism research is worthy to be conducted to elucidate the mode of action of different PFASs on T2DM at different exposure levels.

Occurrence, spatiotemporal distribution, seasonal and annual variation, and source apportionment of poly- and perfluoroalkyl substances (PFASs) in the northwest of Tai Lake Basin, China

Poly- and perfluoroalkyl substances (PFASs) have attracted mounting attention due to their potential harmful effects and degradation-resistant property. This study continuously monitored the concentration of PFASs for four seasons in two years in the northwest of Tai Lake Basin. The occurrence, spatiotemporal distribution, seasonal and annual variation, and source apportionment of 13 PFASs were investigated in 60 surface water sampling sites and 33 emission sources. The average concentrations of the total PFASs were 205.6 ng L^-1 and 171.9 ng L^-1 in 2018 and 2019, respectively. This improvement could be mainly attributed to the local industrial restructuring. Furthermore, principal component analysis and heat map-hierarchical cluster analysis were employed to analyze distribution characteristics and the possible sources of PFASs pollution. It showed that perfluorooctane sulfonate (PFOA) mainly originated from the effluents of chemical plants, while the potential source of perfluorohexane sulfonate (PFHxS) included all the three types of emission sources. Besides, two indicators were adopted to evaluate the impact of non-point sources and the result showed the effect of runoff was obvious while the effect of atmospheric deposition was weak. A systematic mass balance calculation showed that the total riverine input flux from Wujin District to Tai Lake was 126.5 kg/a.

Perfluorooctanesulfonic Acid and Perfluorohexanesulfonic Acid Alter the Blood Lipidome and the Hepatic Proteome in a Murine Model of Diet-Induced Obesity

Perfluoroalkyl substances (PFAS) represent a family of environmental toxicants that have infiltrated the living world. This study explores diet-PFAS interactions and the impact of perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic (PFHxS) on the hepatic proteome and blood lipidomic profiles. Male C57BL/6J mice were fed with either a low-fat diet (10.5% kcal from fat) or a high fat (58% kcal from fat) high carbohydrate (42 g/l) diet with or without PFOS or PFHxS in feed (0.0003% wt/wt) for 29 weeks. Lipidomic, proteomic, and gene expression profiles were determined to explore lipid outcomes and hepatic mechanistic pathways. With administration of a high-fat high-carbohydrate diet, PFOS and PFHxS increased hepatic expression of targets involved in lipid metabolism and oxidative stress. In the blood, PFOS and PFHxS altered serum phosphatidylcholines, phosphatidylethanolamines, plasmogens, sphingomyelins, and triglycerides. Furthermore, oxidized lipid species were enriched in the blood lipidome of PFOS and PFHxS treated mice. These data support the hypothesis that PFOS and PFHxS increase the risk of metabolic and inflammatory disease induced by diet, possibly by inducing dysregulated lipid metabolism and oxidative stress.

Sequestration and potential release of PFAS from spent engineered sorbents

Per- and poly-fluoroalkyl substances (PFAS) have contaminated land and water at numerous sites worldwide that now require remediation. The most common approach for treating contaminated water currently relies on removal of PFAS by sorption. The spent sorbents loaded with PFAS can potentially be disposed of at landfills, provided the sorbed contaminants remain sequestered and certain risk criteria are met. Hence, it is essential that remediation sorbents (i) rapidly adsorb a large variety of PFAS under varying water chemistry conditions, and (ii) do not release the adsorbed PFAS in due course. This review aims at establishing the current state of knowledge about the potential release of PFAS that may occur during and after treatment. The scientific literature currently provides data for a very restricted range of long-chain PFAS. Our knowledge of the dynamics of PFAS adsorption processes on engineered sorbents is limited, and even less is known about their desorption processes. The sorption of PFAS can be strongly affected by changes in the solution pH, ionic strength and dissolved organic matter content, and the process is also subject to complex competition mechanisms in the presence of other PFAS as well as organic contaminants and inorganic salts. Several studies suggest that changes in one or several of these factors may trigger the release of PFAS from engineered sorbents. This phenomenon is more likely to occur for PFAS with shorter carbon chain lengths (<C8), at high pH and in the presence of other PFAS or other anionic sorbates. The release of PFAS from spent sorbent materials, stored or deposited under conditions that vary over time, is highly undesirable, as they can potentially become a secondary source of PFAS in the environment. Our analysis identifies a number of knowledge-gaps that should be urgently addressed in order to design sustainable remediation solutions, including an improved management of spent sorbent materials.

Associations between perfluoroalkyl substances and thyroid hormones after high exposure through drinking water

BACKGROUND

The reported associations for several per- and polyfluoroalkyl substance (PFAS) with thyroid hormones are inconsistent in epidemiological studies. The purpose of the current study was to investigate the possible association of thyroid hormones in relation to serum levels of perfluorohexane sulfonate, perfluorooctane sulfonate and perfluorooctanoic acid, in a Swedish general population, highly exposed through contaminated drinking water, and if the associations with PFAS remained in a comparison to a reference group based only on residency in areas with contrasting PFAS levels.

METHOD

3297 participants from Ronneby, a municipality with drinking water highly contaminated by PFAS (exposed group), and a reference group (N = 226) from a nearby municipality with non-contaminated drinking water supply were included. Regression analysis was used to investigate the associations between PFAS exposure, assessed as exposure groups (Ronneby and reference groups) and measured serum PFAS levels, and thyroid hormone levels, with adjustments for age, sex and BMI.

RESULT

No cross-sectional associations were found between PFAS and thyroid hormones in adults and seniors except for a positive association between PFAS and fT4 in males over 50. Higher thyroid hormone levels were found in the preteen children from Ronneby compared to the reference group. In contrast, within Ronneby, there was weak evidence of associations between increased PFAS levels and decreased fT3 in preteen boys, and decreased TSH in teenage males. No such pattern was found in preteen and teenage girls.

CONCLUSION

The present study found no consistent evidence to support association of PFAS with thyroid hormones.

Endocrine Disruptor Potential of Short- and Long-Chain Perfluoroalkyl Substances (PFASs)-A Synthesis of Current Knowledge with Proposal of Molecular Mechanism

Endocrine disruptors are a group of chemical compounds that, even in low concentrations, cause a hormonal imbalance in the body, contributing to the development of various harmful health disorders. Many industry compounds, due to their important commercial value and numerous applications, are produced on a global scale, while the mechanism of their endocrine action has not been fully understood. In recent years, per- and polyfluoroalkyl substances (PFASs) have gained the interest of major international health organizations, and thus more and more studies have been aimed to explain the toxicity of these compounds. PFASs were firstly synthesized in the 1950s and broadly used in the industry in the production of firefighting agents, cosmetics and herbicides. The numerous industrial applications of PFASs, combined with the exceptionally long half-life of these substances in the human body and extreme environmental persistence, result in a common and chronic exposure of the general population to their action. Available data have suggested that human exposure to PFASs can occur during different stages of development and may cause short- or/and long-term health effects. This paper synthetizes the current literature reports on the presence, bioaccumulation and, particularly, endocrine toxicity of selected long- and short-chain PFASs, with a special emphasis on the mechanisms underlying their endocrine actions.

Prenatal exposure and transplacental transfer of perfluoroalkyl substance isomers in participants from the upper and lower reaches of the Yangtze River

Data on gestational exposure characteristics and transplacental transfer are quite limited for perfluoroalkyl substance (PFAS) isomers, especially those from large-scale comparative studies. To fill this gap, we examined isomers of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in matched maternal and cord serum from Mianyang and Hangzhou, which are located in the upper and lower reaches of the Yangtze River, China, respectively. These data were compared with those from our previous study on Wuhan in the middle reach. The average ΣPFAS concentration increased from upstream to downstream (Mianyang (4.44 ng/mL) < Wuhan (9.88 ng/mL) < Hangzhou (19.72 ng/mL)) and may be related to the per capita consumption expenditure of each city. The ln-transformed PFAS concentrations showed significant differences between Mianyang and Hangzhou after adjusting confounding factors (p < 0.05). The percentages of linear PFOS and PFOA in maternal and cord serum from these cities all exceeded those in electrochemical fluorination products. The isomer profiles of PFASs in maternal and cord serum might be greatly influenced by local production processes of PFASs and residents' dietary habits. The transplacental transfer efficiencies decreased significantly with increasing concentrations in maternal serum for ΣPFAS, ΣPFOS, ΣPFOA, ΣPFHxS, n-PFOS, iso-PFOS, 4m-PFOS, 1m-PFOS, n-PFOA, n-PFHxS, and br-PFHxS (Spearman rank correlation coefficients (r) = 0.373-0.687, p < 0.01). These findings support an understanding of the regional characteristics in maternal exposure to PFASs along the Yangtze River, isomeric profiles of PFASs in these regions, and the transplacental transfer processes of PFAS isomers.

Serum perfluoroalkyl substances in residents following long-term drinking water contamination from firefighting foam in Ronneby, Sweden

BACKGROUND

In December 2013, it was discovered that drinking water supplied to one third of the households in Ronneby, southern Sweden, was highly contaminated by PFAS (sum level >10,000 ng/L) originated from firefighting foams used at a nearby military airport.

OBJECTIVES

To report serum PFAS levels of Ronneby residents participating in a biomonitoring program, and to describe the variation by age, sex and calendar period for residential exposure. In addition, a reference group living in a neighboring municipality without PFAS contaminated drinking water was examined.

METHODS

Blood samples and demographic data were collected for 3297 Ronneby residents and 226 individuals from the reference group. Yearly residence addresses were available for 3086 Ronneby residents from the national population registry. Serum concentrations of PFHxS, PFOS and PFOA were determined in all participants, with additional PFHpA, PFNA and PFDA in subsets of the participants.

RESULTS

The population geometric means for serum PFHxS, PFOS and PFOA were 114, 135 and 6.8 ng/mL for all Ronneby residents, i.e.135, 35 and 4.5 times higher than for the reference group. Ronneby residents who resided in the area with contaminated water supply during 2005-2013 showed much higher PFAS levels in 2014 than those exposed only before 2005. Ronneby residents who never resided in the area with contaminated water supply also had higher serum PFAS levels than the reference group. All three PFAS were highly correlated (r_s > 0.9 for each pair). Serum PFAS levels were lowest in teenage years and then increased with age. Adult females had lower PFAS levels on average than males under the age of 60 but higher above 60.

DISCUSSION

The results reveal high serum PFAS levels dominated by PFHxS and PFOS in the Ronneby residents highly exposed to PFAS originated from firefighting foams. The PFAS exposure in Ronneby permits studies of associations to a range of health parameters, as well as studies of the toxicokinetics of PFAS exposure.

Perfluorooctane Sulfonate (PFOS) and Perfluorohexane Sulfonate (PFHxS) Alters Protein Phosphorylation, Increase ROS Levels and DNA Fragmentation during In Vitro Capacitation of Boar Spermatozoa

Simple Summary

Perfluorinated compounds are synthetic chemicals, with a wide variety of applications like firefighting foams, food packaging, additives in paper and fabrics to avoid dyes. Perfluorooctane sulfonate and perfluorohexane sulfonate are globally distributed, and contaminates air, water, food, and dust, have toxic effects and bioaccumulate. Significant levels of these compounds have found in blood serum, breast milk, and semen of occupationally exposed and unexposed people, as well as in blood serum and organs of the domestic, farm, and wild animals. The present study seeks to analyze the toxic effects and possible alterations caused by the presence of these compounds in boar sperm during the in vitro capacitation, due to their toxicity, worldwide distribution, and lack of information in spermatozoa physiology during pre-fertilization processes.

Abstract

Perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) are toxic and bioaccumulative, included in the Stockholm Convention’s list as persistent organic pollutants. Due to their toxicity, worldwide distribution, and lack of information in spermatozoa physiology during pre-fertilization processes, the present study seeks to analyze the toxic effects and possible alterations caused by the presence of these compounds in boar sperm during the in vitro capacitation. The spermatozoa capacitation was performed in supplemented TALP-Hepes media and mean lethal concentration values of 460.55 μM for PFOS, and 1930.60 μM for PFHxS were obtained. Results by chlortetracycline staining showed that intracellular Ca²⁺ patterns bound to membrane proteins were scarcely affected by PFOS. The spontaneous acrosome reaction determined by FITC-PNA was significantly reduced by PFOS and slightly increased by PFHxS. Both toxic compounds significantly alter the normal capacitation process from 30 min of exposure. An increase in ROS production was observed by flow cytometry and considerable DNA fragmentation by the comet assay. The immunocytochemistry showed a decrease of tyrosine phosphorylation in proteins of the equatorial and acrosomal zone of the spermatozoa head. In conclusion, PFOS and PFHxS have toxic effects on the sperm, causing mortality and altering vital parameters for proper sperm capacitation.

Distribution and effects of branched versus linear isomers of PFOA, PFOS, and PFHxS: A review of recent literature

Perfluorinated alkyl substances (PFAS) have come to attention recently due to their widespread presence in the environment, recalcitrance, and potential negative health associations. Because of the long-term production of PFAS using ECF, which created branched isomers as byproducts in addition to the intended linear product, branched isomers of PFAS account for a significant portion of PFAS load in the environment. The distribution of isomers is not consistent in the environment, however. Geographic location appears to be a major factor in determining the isomer makeup of PFAS in surface and groundwater as well as in humans and animals. This is largely to differences in production methods; a region that produced PFAS via ECF for many years would have a higher ratio of branched isomers than one that produces PFAS using telomerization. In addition, the different structures of branched PFAS isomers as compared to linear PFAS appear to affect transport in the environment. Research suggests that linear PFAS sorb preferentially to soil and sediments, whereas branched isomers are more likely to remain in water. The higher polarity of the branched structure explains this difference. Studies in humans and animals show that most animals preferentially accumulate the linear PFOS isomer, but humans appear to preferentially accumulate the branched isomers as they are often found in human serum at percentages higher than that of ECF product. In addition, some studies have indicated that linear and branched PFAS isomers have some unique negative health associations. Very few studies, however, account for linear and branched PFAS separately.

Mechanochemical degradation of perfluorohexane sulfonate: Synergistic effect of ferrate(VI) and zero-valent iron

Perfluorohexane sulfonate (PFHxS) has been newly recommended to be added into the Stockholm Convention on persistent organic pollutants (POPs). As one of the major perfluoroalkyl pollutants, its long half-time in human serum and neurotoxicity are cause for significant concern. Although mechanochemical degradation has been evaluated as a promising ecofriendly technology to treat pollutants, the extraordinary stability of poly- and perfluoroalkyl substances (PFASs) raises harsh requirements for co-milling reagents. In the present study, zero-valent iron (ZVI) and ferrate(VI) were for the first time used as the co-milling reagents to degrade PFHxS. When ZVI and ferrate(VI) were used alone, both the degradation and defluorination efficiencies were low. However, after milling at the optimum ratio (ferrate(VI):ZVI = 1:2) for 4 h, the synergistic effect of ZVI and ferrate(VI) resulted in almost complete degradation (100%) and defluorination (95%). Two points can account for this excellent performance: (1) the mechanochemical energy input in the system initiates and prominently promotes related reactions; and (2) the active species generated from the reactions among ZVI, ferrate(VI) and other high-valent iron species will accelerate the process of electron transfer. The sulfonate group comprises the favorable attack sites, as corroborated by both the identified intermediates and quantum chemical calculations. The homolysis of the C-S bond is not only the triggering step, but also the rate-limiting step. In summary, the present work confirms the feasibility and underlying mechanism of the ZVI-ferrate(VI) co-milling system to defluorinate PFHxS, which might be a promising technology to treat PFASs in solid wastes.

Per- and Polyfluoroalkyl Substances in Early Pregnancy and Risk for Preeclampsia: A Case-Control Study in Southern Sweden

Preeclampsia is one of the most common causes of perinatal and maternal morbidity/mortality. One suggested environmental risk factor is exposure to endocrine-disrupting pollutants such as per- and polyfluoroalkyl substances (PFAS). The present case-control study in southern Sweden aims to investigate the hypothesized association between serum concentrations of PFAS in early pregnancy and the risk of developing preeclampsia. The study included 296 women diagnosed with preeclampsia (cases) and 580 healthy pregnant women (controls). Maternal serum samples were obtained from a biobank of samples collected in early pregnancy in connection with screening for infections. Serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). Among primiparous women, there were no differences in PFAS concentrations in early pregnancy between the cases and the controls whereas among multipara women, the cases had significantly higher concentrations of PFNA (median concentrations were 0.44 and 0.38 ng/mL, p = 0.04). When individual PFAS were categorized into quartiles and adjustment for potential confounders was performed, the women in the highest quartiles had no significant increased risks of developing preeclampsia as compared with women in the lowest category. In conclusion, the present study provides limited support for the hypothesized association between PFAS and preeclampsia in a population with relatively low exposure levels.

Sorption behaviour of per- and polyfluoroalkyl substances (PFASs) as affected by the properties of coastal estuarine sediments

The sorption of three perfluoroalkyl substances (PFASs), namely perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS), was determined in 19 coastal sediments. There are currently limited data on the sorption behaviour of these chemicals in marine or estuarine sediments and the properties controlling their sorption have not been well established. The median average PFOS K_d value (30.4 L/kg) was >8 times that for PFOA (3.3 L/kg) and PFHxS (2.8 L/kg). Highly significant (P < .001) linear relationships were found between values for sorption coefficients (K_d) for all three chemicals (PFOS, PFOA and PFHxS) to the estuarine sediments and organic carbon (OC) content with r² values ranging from 0.87 to 0.91. The nature of the constituents of OC was determined by nuclear magnetic resonance (NMR) for a subset (10) of the sediments to assess whether the strong relationship between sorption and OC was due solely to an increasing amount of OC or to particular OC fractions. The NMR analysis could not provide strong evidence for one OC fraction type explaining the variation in sorption of the three PFASs. Further investigation using partial least squares of the whole spectra also did not show any particular OC components could explain the K_d variation. This data suggests that variation in sorption in these sediments was primarily due to the varying OC content and not its chemistry.

Prenatal perfluoroalkyl substances and newborn anogenital distance in a Canadian cohort

Exposure to the man-made chemicals perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonate (PFHxS) is widespread. These perfluoroalkyl substances (PFASs) have been associated with androgenic endocrine-disrupting properties; however, the evidence is equivocal and few human studies have examined the association between prenatal exposure to PFASs and markers of androgenic endocrine disruption such as changes in anogenital distance (AGD). In the MIREC cohort, PFOA, PFOS and PFHxS were analyzed in first trimester maternal plasma. AGD was measured in 205 male and 196 female newborns. The change in estimate procedure was used to identify confounders by sex and AGD in multiple linear regression models. Geometric mean plasma concentrations (95% CI) for PFOA, PFOS and PFHxS were 1.71 (1.61, 1.81), 4.40 (4.18, 4.64) and 1.15 (1.06, 1.25) μg/L, respectively. A one-unit increase in natural log transformed PFOA was associated with a 1.36 mm (95% CI 0.30, 2.41) increase in anoscrotal distance, adjusting for household income, active smoking status during pregnancy and gestational age. However, when examined by quartiles, a non-monotonic pattern was observed with wide confidence intervals. No consistent patterns were observed between maternal PFAS concentrations and female AGDs. This study found no clear evidence that maternal plasma concentrations of PFOS, PFOA or PFHxS were associated with shorter infant anogenital distance in males or any change in AGD in females. Whether the positive association observed between longer anoscrotal distance and PFOA is real or would have any long-lasting effect on the reproductive health of males is unknown and needs to be investigated further.

Sorption behaviour of per- and polyfluoroalkyl substances (PFASs) in tropical soils

The sorption behaviour of three perfluoroalkyl substances (PFASs), namely perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS), was determined on 28 tropical soils. Tropical soils are often highly weathered, richer in sesquioxides than temperate soils and may contain variable charge minerals. There are little data on sorption of PFASs in tropical soils. The highest K_d values were found for PFOS with mean values ranging from 0 to 31.6 L/kg. The K_d values for PFOA and PFHxS ranged from 0 to 4.9 L/kg and from 0 to 5.6 L/kg, respectively. While these values are in the range of literature sorption data, the average K_d values for PFOS and PFOA from the literature were 3.7 times and 3.6 times higher, respectively, than those measured in this study. Stepwise regression analysis did explain some of the variance, but with different explanatory variables for the different PFASs. The main soil properties explaining sorption for PFOS and PFOA were oxalate-extractable Al and pH, and for PFHxS was pH.

Perfluorinated substances in the Flemish population (Belgium): Levels and determinants of variability in exposure

Because of their dirt-, water- and oil-repelling properties, per- and polyfluoroalkyl substances (PFASs) are frequently used in a broad variety of consumer products. They have been detected in human samples worldwide. In Flanders, Belgium, the Flemish Environment and Health Studies (FLEHS) measured the levels of five PFAS biomarkers in four different age groups of the Flemish population and identified determinants of variability in exposure. Cord plasma or peripheric serum samples and questionnaire data were available for 220 mother-newborn pairs (2008-2009), 269 mother-newborn pairs (2013-2014), 199 adolescents (14-15 years old, 2010), 201 adults (20-40 years old, 2008-2009) and 205 adults (50-65 years old, 2014). Measured levels of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) in Flanders are in the middle or low range compared to concentrations reported in other Western countries. Levels of perfluorobutanesulfonic acid (PFBS) were below the quantification limit in 98%-100% of the samples. Despite decreasing levels in time for PFOS and PFOA, 77% of the adults (2014) had serum levels exceeding HBM-I values of 5 μg/L for PFOS and 2 μg/L for PFOA. Beside age, sex, fish consumption, parity and breastfeeding, the multiple regression models identified additionally consumption of offal and locally grown food, and use of cosmetics as possible exposures and menstruation as a possible route of elimination. Better knowledge on determinants of exposure is essential to lower PFASs exposure.

Inflammatory bowel disease and biomarkers of gut inflammation and permeability in a community with high exposure to perfluoroalkyl substances through drinking water

Perfluoroalkyl substances (PFAS) can act as surfactants and have been suggested to be capable of affecting gut mucosa integrity, a possible factor in the pathogenesis of inflammatory bowel disease (IBD). So far, only PFOA has been shown to have a positive association with ulcerative colitis. The present study aimed to investigate the association of PFAS and clinically diagnosed IBD in the Ronneby cohort, a population with high PFAS exposure (especially high PFOS and PFHxS) from Aqueous Film-Forming Foam through drinking water, using registry data. Additionally, to explore associations of PFAS with fecal zonulin and calprotectin, subclinical biomarkers of gut inflammation and permeability, in a sub-set of participants from Ronneby and Karlshamn (a nearby control municipality). The registry study included all people that ever resided in Ronneby municipality at least one year between 1980 and 2013. Yearly exposure to contaminated drinking water was assessed based on residential addresses and waterworks supply data, and the population classified by early, mid and late periods in ascending level of contamination. Diagnosed IBD cases were retrieved from the Swedish National Patient register and cause-of-death register. The Cox proportional hazards model was used to derive the hazard ratios (HRs) for diagnosed IBD. The biomarker study included 189 individuals who provided fecal samples. Serum PFAS were measured using LC-MS/MS. Fecal zonulin and calprotectin were measured using ELISA. Linear regression was used to assess the associations between measured PFAS and biomarker levels. In the registry study, no raised HRs for diagnosed IBD were found for cohort subjects with mid (1995-2004) or late period (2005-2013) exposure compared to never exposure. Early period exposure only (1985-1994) showed raised HRs for Crohn's disease (HR = 1.58, p = 0.048) and other non-specified IBD (HR = 1.38, p = 0.037). In the biomarker study, Karlshamn showed higher fecal calprotectin levels (median = 99.6 mg/kg in Karlshamn vs. 66.8 mg/kg in Ronneby, p = 0.04). A trend of decreased calprotectin with increased serum PFAS indicated higher PFAS was associated with lower degree of gut inflammation (p = 0.002). No association between serum PFAS and fecal zonulin was found. In conclusion, the present study found no consistent evidence to support PFAS exposure as a risk factor for IBD.

Strains Isolated from PFAS-Contaminated Environmental Matrices

PFASs (perfluoroalkyl and polyfluoroalkyl substances) are highly fluorinated, aliphatic, synthetic compounds with high thermal and chemical stability as well as unique amphiphilic properties which make them ingredients in a range of industrial processes. PFASs have attracted consideration due to their persistence, toxicity and bioaccumulation tendency in the environment. Recently, attention has begun to be addressed to shorter-chain PFASs, such as perfluorohexane sulfonate [PFHxS], apparently less toxic to and more easily eliminated from lab animals. However, short-chain PFASs represent end-products from the transformation of fluorotelomers whose biotic breakdown reactions have not been identified to date. This means that such emergent pollutants will tend to accumulate and persist in ecosystems. Since we are just learning about the interaction between short-chain PFASs and microorganisms, this study reports on the response to PFHxS of two Pseudomonas sp. strains isolated from environmental matrices contaminated by PFASs. The PFHxS bioaccumulation potential of these strains was unveiled by exploiting different physiological conditions as either axenic or mixed cultures under alkanothrofic settings. Moreover, electron microscopy revealed nonorthodox features of the bacterial cells, as a consequence of the stress caused by both organic solvents and PFHxS in the culturing substrate.

In vitro and in silico modeling of perfluoroalkyl substances mixture toxicity in an amphibian fibroblast cell line

Poly and perfluoroalkyl substances (PFAS) are a large group of emerging organic pollutants that can persist in the environment and bioaccumulate in biota. They are found in complex mixtures, and although the exact number of PFAS is unknown, it has been estimated to be in the thousands. The objective of this study was two-fold. First, we examined the cytotoxicity of PFAS singly and in binary mixtures using an amphibian fibroblast cell line. Second, we used this experimental data to develop quantitative structure-activity relationship (QSAR) models for single and binary mixtures. We tested the cytotoxicity of four common PFAS: perfluorooctane sulfonate (PFOS); perfluorooctanoic acid (PFOA); perfluorohexane sulfonate (PFHxS); and perfluorohexanoic acid (PFHxA). PFOS was the most toxic and PFHxA the least cytotoxic. Binary mixtures allowed for the construction of isobolograms to test for additivity, synergism, or antagonism. Using this data, QSAR modeling was used for predicting the toxicity of 24 single and 1380 binary mixtures (theoretically generated). Overall, our experimental and modeling results showed that mixtures were approximately additive, with the exception of PFOS and PFOA, which were found to be weakly synergistic. This data shows that certain mixtures of PFAS may have increased toxicity potential above what the simple sum of PFAS concentrations would suggest. More studies are needed that test the toxicity of PFAS mixtures.

First-trimester maternal concentrations of polyfluoroalkyl substances and fetal growth throughout pregnancy

BACKGROUND

Several studies have investigated the possible association between prenatal exposure to perfluoroalkyl substances (PFASs) and birth anthropometry. However, none has assessed fetal size longitudinally. We studied the possible association between PFASs and fetal biometry.

METHODS

In 1230 mother-child pairs of three cohorts from the Spanish INMA-Project, we analyzed perfluorohexanesulfonic acid (PFHxS), perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) in first-trimester maternal plasma (collection: 2003-2008). We measured abdominal circumference (AC), femur length (FL), biparietal diameter (BPD), and estimated fetal weight (EFW) by ultrasounds at 12, 20, and 34 gestational weeks. We conducted multivariable linear regression analyses between log₂-transformed (PFASs) and SD-scores of fetal parameters in each cohort and subsequent meta-analysis. We also assessed effect modification by sex and maternal smoking.

RESULTS

PFHxS, PFOA, PFOS, and PFNA medians were: 0.58, 2.35, 6.05, and 0.65 ng/mL, respectively. There were no associations for the whole population in any trimester of pregnancy. However, we found an indication that maternal smoking modified the effect in different directions depending on the PFAS. Among smokers (31%), we found negative associations between both PFOA and PFNA and FL or EFW at week 20 (% change ranging between -6.8% and -5.7% per twofold PFAS increase) and positive associations between PFHxS or PFOS and BPD at week 34 (6.8% and 6.3%, respectively).

CONCLUSIONS

Results did not suggest an overall association between prenatal PFASs and fetal growth. The results among smokers should be taken with caution and further studies are warranted to elucidate the possible role of smoking in this association.

Toxicokinetics of perfluorobutane sulfonate (PFBS), perfluorohexane-1-sulphonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS) in male and female Hsd:Sprague Dawley SD rats after intravenous and gavage administration

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In rats, the half-life of perfluoroalkyl sulfonic acids decreased with shorter chain lengths.

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Sex differences in kinetics were found for PFBS and PFHxS but not PFOS.

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Perfluoroalkyl sulfonic acids were highly present in the liver but not the brain.

Perfluorinated alkyl substances (PFAS) are persistent contaminants that have been detected in the environment and in humans. With the PFAS chemical class, there are perfluorinated alkyl acids, many of which have been associated with certain toxicities. Because toxicity testing cannot feasibly be conducted for each individual PFAS, the National Toxicology Program (NTP) designed studies to compare toxicities across different subclasses of PFAS and across PFAS of different chain lengths to better understand the structure-toxicity relationship. Pharmacokinetic studies were conducted in parallel to these toxicity studies to facilitate comparisons across PFAS and to provide context for human relevance. Here, the toxicokinetic parameters of perfluorobutane sulfonate (PFBS), perfluorohexane-1-sulphonic acid (PFHxS), or perfluorooctane sulfonate (PFOS) after a single intravenous or gavage administration in male and female Hsd:Sprague-Dawley rats are reported. Concentrations of these PFAS were measured in the liver, kidney, and brain. Plasma half-life increased with longer chain length after gavage administration: PFBS- males averaged 3.3 h, females 1.3 h; PFHxS- males averaged 16.3 days, females 2.1 days; PFOS- males and females averaged ˜ 20 days. There were dose-dependent changes in clearance and systemic exposure for all administered chemicals and the direction of change was different in PFOS compared to the others. Liver:plasma ratios of PFOS were the highest followed by PFHxS and PFBS, while brain:plasma ratios were low in all three sulfonates. Sex differences in plasma half-life and tissue distribution were observed for PFBS and PFHxS, but not PFOS. These data provide a direct comparison of the kinetics of three different perfluoroalkyl sulfonic acids and allow for the contextualization of toxicity data in rats for human risk assessment of this chemical class.

Subtle morphometric, behavioral and gene expression effects in larval zebrafish exposed to PFHxA, PFHxS and 6:2 FTOH

Recent studies of perfluoroalkylated substances (PFASs) have focused on the toxicity of long chain PFASs, such as PFOS or PFOA, which have been demonstrated to cause an array of developmental and behavioral effects. However, less is known about low molecular weight PFASs and alternatives. This study examined the morphometric and behavioral effects in zebrafish following developmental exposures of C6 PFASs: perfluorohexanoic acid, PFHxA, perfluorohexane sulfonate, PFHxS, and 6:2 fluorotelomer alcohol, 6:2 FTOH. Embryos were exposed to 0.02-20 μM concentrations of these compounds from the high stage (˜3 h post fertilization, hpf) until 120 hpf. Morphometric and gene expression endpoints were examined at 120 hpf. Genes selected for analysis were previously shown to be altered in zebrafish developmentally exposed to PFOS and PFOA. Additionally, exposed larvae were transferred to clean water and reared until 14 days post fertilization, dpf, when behavioral assays were completed and morphometric endpoints examined. While PFHxA was found to be the most acutely toxic at 120 hpf, few morphometric effects were observed. Gene expression was the most sensitive endpoint with significant increased tgfb1a, bdnf, and ap1s1 expression observed with PFHxA exposure. PFHxS exposure produced morphometric effects in the larvae, specifically increased length and yolk sac area at 2 and 20 μM. This phenotype persisted to the 14 dpf time point, where these larvae additionally displayed decreased distance traveled and crosses through the center of the arena of the behavioral assay. Exposure to 6:2 FTOH caused no morphometric effects at 120 hpf, and this compound was the least acutely toxic. However, expression of both tgfb1a and bdnf were increased by greater than 2 fold change at this time point. Effects also persisted to 14 dpf where a significant increase in distance traveled and velocity were observed in the behavioral assay. This study demonstrates effects on behavioral, morphometric and gene expression endpoints with developmental PFHxA, PFHxS, and 6:2 FTOH exposures in zebrafish.

Elevated concentrations of perfluorohexanesulfonate and other per- and polyfluoroalkyl substances in Baiyangdian Lake (China): Source characterization and exposure assessment

Novel 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and legacy PFASs, such as perfluorohexane sulfonate (PFHxS), have been used to replace perfluorooctane sulfonate (PFOS), a known persistent organic pollutant. Thus, it is critical to understand these PFOS alternatives regarding their sources and concentrations in the natural environment. In this study, 41 surface water samples as well as edible aquatic organisms were collected from Baiyangdian Lake, the largest freshwater lake in Hebei Province, China. Perfluorooctanoate acid (PFOA) and PFHxS were the predominant PFASs detected in the surface water, reaching concentrations of 8 397.23 ng/L and 1 478.03 ng/L, respectively, with PFHxS accounting for the greatest proportion (∼80.00%) in most water samples. PFHxS (mean: 87.53 ng/g) and PFOS (mean: 35.94 ng/g) were also the most prevalent compounds detected in aquatic organisms. Estimated daily intake (EDI) values of PFOS (16.56 ng/kg bw/d) and PFHxS (16.11 ng/kg bw/d) via aquatic food and drinking water were the highest among PFASs, indicating potential exposure risks to residents. In addition, fish product consumption was the important exposure pathway for residents to PFOA, PFHxS, PFOS, and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA). This study reports on the highest PFHxS levels ever recorded in surface water, suggesting that further quantification of PFHxS in human serum and assessment of its health risks to local residents are warranted and critical.

Perfluoroalkylsulfonic and carboxylic acids in earthworms (Eisenia fetida): Accumulation and effects results from spiked soils at PFAS concentrations bracketing environmental relevance

Effects of perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluoroheptanoic acid (PFHpA) on earthworms (Eisenia fetida) in soils contaminated with these compounds at 0.1, 1, 10, 1,000, and 100,000 μg kg^-1 dry weight, covering concentration levels found in background, biosolid-amended, and facility-surrounding soils, were investigated. Earthworms were exposed to spiked soil for 21 days. Concentrations of these compounds in earthworms after 21-d exposure ranged from below detection to 127 mg kg^-1 wet weight with the rank order of PFNA > PFHxS > PFHpA > PFBS; no mortality of earthworms was observed in all treatments including controls, except PFBS at 1,000 μg kg^-1 and all PFASs at 100,000 μg kg^-1. The highest weight loss (29%) was observed for earthworms exposed to PFNA at 100,000 μg kg^-1, which was significantly different from all other treatments except PFHpA at 100,000 μg kg^-1. These results are expected to fill some data gaps in toxicity of PFASs in terrestrial environments and provide helpful information on the potential for trophic transport of PFASs from soil to higher organisms.

Reproductive and developmental toxicity of potassium perfluorohexanesulfonate in CD-1 mice

Potassium perfluorohexanesulfonate (K⁺PFHxS) was evaluated for reproductive/developmental toxicity in CD-1 mice. Up to 3 mg/kg-d K⁺PFHxS was administered (n = 30/sex/group) before mating, for at least 42 days in F₀ males, and for F₀ females, through gestation and lactation. F₁ pups were directly dosed with K⁺PFHxS for 14 days after weaning. There was an equivocal decrease in live litter size at 1 and 3 mg/kg-d, but the pup-born-to-implant ratio was unaffected. Adaptive hepatocellular hypertrophy was observed, and in 3 mg/kg-d F₀ males, it was accompanied by concomitant decreased serum cholesterol and increased alkaline phosphatase. There were no other toxicologically significant findings on reproductive parameters, hematology/clinical pathology/TSH, neurobehavioral effects, or histopathology. There were no treatment-related effects on postnatal survival, development, or onset of preputial separation or vaginal opening in F₁ mice. Consistent with previous studies, our data suggest that the potency of PFHxS is much lower than PFOS in rodents.

Per- and polyfluoroalkyl substances (PFAS) in American Red Cross adult blood donors, 2000-2015

In 2015, thirteen per- and polyfluoroalkyl substances (PFAS), including perfluorohexanesulfonate (PFHxS), perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), and perfluorodecanoate (PFDA) were analyzed in human plasma that were collected from a total of 616 American Red Cross male and female blood donors (ages 20-69) at 6 regional blood collection centers. Plasma samples were analyzed using a validated solvent precipitation-isotope dilution direction-liquid chromatography tandem mass spectrometry method. The data were analyzed in conjunction with prior cross-sectional investigations [2000-2001 (n =645), 2006 (n =600), and 2010 (n =600)] to determine PFAS trends. Age- and sex-adjusted geometric mean serum (2000-2001) and plasma (2006, 2010, 2015) concentrations (ng/mL) were, respectively: PFHxS (2.3, 1.5, 1.3, 0.9); PFOS (35.1, 14.5, 8.4, 4.3); PFOA (4.7, 3.4, 2.4, 1.1); PFNA (0.6, 1.0, 0.8, 0.4); and PFDA (0.2, 0.3, 0.3, 0.1). The percentage decline in these geometric mean concentrations from 2000-2001 to 2015 were: PFHxS (61%); PFOS (88%); PFOA (77%); PFNA (33%); and PFDA (50%). The results indicate a continued decline of PFHxS, PFOS, and PFOA concentrations in American Red Cross blood donors. For the remaining PFAS measured in 2015, including the shorter chain perfluoroalkyls perfluorobutanesulfonate (PFBS) and perfluorohexanoate (PFHxA), the majority of samples were below the lower limit of quantitation.

Perfluoroalkyl substances with isomer analysis in umbilical cord serum in China

Perfluoroalkyl substances (PFASs) are a class of widely used chemicals that have been detected in the environment and general population. However, the isomer patterns in human are poorly characterized. Previous studies observed the isomer-specific maternal-fetal transfer of PFASs in human. In our current study, we first examined the profile of PFASs and isomers, including 17 linear PFASs and 10 branched PFOS/PFOA isomers by using isotopic internal standards in umbilical cord serum samples from Guangzhou, China. We collected a total of 321 of cord blood serum samples from July to October in 2013, and analyzed the PFASs concentration with isomer-specific PFASs analysis method. The results showed that 9 out of 17 PFASs (linear PFASs) were detected (>50% detection rate). Perfluorohexane sulfonate (PFHxS, median 3.87 ng/mL) was the predominant, followed by total PFOS (median 2.99 ng/mL) and total PFOA (median 1.23 ng/mL) in cord serum. In addition, 1m-, iso-, ∑3+4+5m-PFOS and iso-PFOA were the branched PFASs detected in the current study. The proportion of linear PFOS (n-PFOS) was 75.16% of ∑PFOS which was similar to the proportion of electrochemical fluorination that produces ca. 70% linear PFOS and 30% branched. On the contrary, linear PFOA (n-PFOA) accounted for 98.69% ∑PFOA in cord serum samples. Our finding indicates distinct PFASs and PFOS/PFOA isomer profile in cord serum, suggesting there might be a different exposure pathway and metabolism of PFASs.

Influence of cations on the partition behavior of perfluoroheptanoate (PFHpA) and perfluorohexanesulfonate (PFHxS) on wastewater sludge

The effects of different cations on the sorption behavior of PFHpA and PFHxS on two types of sludge were investigated in this study. The sodium and potassium ions did not significantly affect PFHpA and PFHxS sorption on different sludge. For calcium and magnesium, the sorption amount of PFAS increased with calcium and magnesium concentration increasing from 1 to 30 mM and then decreased with those increasing from 30 to 100 mM. The sorption level of PFHxS or PFHpA greatly increased with increasing Al3+ and Fe3+ cation concentrations due to the strong sorption and coagulation effects by the formation of aluminum hydroxide (or ferric hydroxide) colloids or precipitates. After the organics in sludge has been removed by thermal treatment, the PFAS sorption on sludge was greatly reduced. Such finding indicated that sorption to organic matter is more important for anionic PFASs than adsorption to mineral surfaces. However, due to the higher content of biological organics, a secondary activated sludge has higher affinity toward PFAS species than chemically enhanced primary treatment sludge. It indicated that the organic types in sludge were also crucial to the sorption levels of PFASs by sludge.

The effects of perfluorinated chemicals on adipocyte differentiation in vitro

The 3T3-L1 preadipocyte culture system has been used to examine numerous compounds that influence adipocyte differentiation or function. The perfluoroalkyl acids (PFAAs), used as surfactants in a variety of industrial applications, are of concern as environmental contaminants that are detected worldwide in human serum and animal tissues. This study was designed to evaluate the potential for PFAAs to affect adipocyte differentiation and lipid accumulation using mouse 3T3-L1 cells. Cells were treated with perfluorooctanoic acid (PFOA) (5-100 µM), perfluorononanoic acid (PFNA) (5-100 µM), perfluorooctane sulfonate (PFOS) (50-300 µM), perfluorohexane sulfonate (PFHxS) (40-250 µM), the peroxisome proliferator activated receptor (PPAR) PPARα agonist Wyeth-14,643 (WY-14,643), and the PPARγ agonist rosiglitazone. The PPARγ agonist was included as a positive control as this pathway is critical to adipocyte differentiation. The PPARα agonist was included as the PFAA compounds are known activators of this pathway. Cells were assessed morphometrically and biochemically for number, size, and lipid content. RNA was extracted for qPCR analysis of 13 genes selected for their importance in adipocyte differentiation and lipid metabolism. There was a significant concentration-related increase in cell number and decreased cell size after exposure to PFOA, PFHxS, PFOS, and PFNA. All four PFAA treatments produced a concentration-related decrease in the calculated average area occupied by lipid per cell. However, total triglyceride levels per well increased with a concentration-related trend for all compounds, likely due to the increased cell number. Expression of mRNA for the selected genes was affected by all exposures and the specific impacts depended on the particular compound and concentration. Acox1 and Gapdh were upregulated by all six compounds. The strongest overall effect was a nearly 10-fold induction of Scd1 by PFHxS. The sulfonated PFAAs produced numerous, strong changes in gene expression similar to the effects after treatment with the PPARγ agonist rosiglitazone. By comparison, the effects on gene expression were muted for the carboxylated PFAAs and for the PPARα agonist WY-14,643. In summary, all perfluorinated compounds increased cell number, decreased cell size, increased total triglyceride, and altered expression of genes associated with adipocyte differentiation and lipid metabolism.

Associations between serum perfluoroalkyl acids and LINE-1 DNA methylation

Perfluoroalkyl acids (PFAAs) are persistent, synthetic compounds that are used in a number of consumer products. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been associated with cardiovascular risk factors, and changes in gene expression and DNA methylation in animals and cellular systems. However, whether PFAA exposure is associated with LINE-1 DNA methylation, a potential marker of cardiovascular risk, in humans remains unknown. We sought to evaluate the cross-sectional associations between serum PFAAs and LINE-1 DNA methylation in a population highly exposed to PFOA. We measured serum PFAAs twice four to five years apart in 685 adult participants (47% male, mean age±SD=42±11years). We measured percent LINE-1 DNA methylation in peripheral blood leukocytes at the second time point (follow-up), and estimated absolute differences in LINE-1 methylation associated with an interquartile (IQR) shift in mean PFAA serum levels. IQR increases in mean serum PFOA, PFOS, perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) were associated with differences of -0.04 (p=0.16), 0.20 (p=0.001), 0.06 (p=0.19), and 0.02 (p=0.57), respectively, in % LINE-1 methylation at follow-up after adjustment for potential confounders. We observed a monotonic increase in LINE-1 DNA methylation across tertiles of PFOS and PFNA (ptrend=0.02 for both associations), but not across tertiles of PFOA or PFHxS (ptrend=0.71 and 0.44, respectively). In summary, serum PFOS was associated with LINE-1 methylation, while serum PFOA, PFHxS, and PFNA were not. Additional research is needed to more precisely determine whether these compounds are epigenetically active.