Historical human exposure to perfluoroalkyl acids in the United States and Australia reconstructed from biomonitoring data using population-based pharmacokinetic modelling

Human biomonitoring follow-up study on PFOA contamination and investigation of possible influencing factors on PFOA exposure in a German population originally exposed to emissions from a fluoropolymer production plant

BACKGROUND

In the past, perfluorooctanoic acid (PFOA) was produced and applied as an emulsifier in a fluoropolymer production plant in the Altötting district, southern Bavaria (Germany). This chemical was released directly into the environment, resulting in the contamination of the local drinking water. During a human biomonitoring (HBM) survey in 2018, increased median PFOA blood serum levels, compared to a normally exposed control group with no known source of PFOA exposure from Munich, Germany, were detected in the resident population (23.18 μg/l in the general population, 20.71 μg/l in the children's group). The follow-up study aimed to investigate whether purification of the drinking water as the main PFOA exposure source has been successful in reducing internal PFOA exposure and to estimate the association of internal PFOA exposure with possible influencing factors.

METHODS

Only individuals who had already participated in the HBM study in 2018 were included. For the determination of the PFOA serum concentration, 5 ml of blood was drawn from each participating person. Blood samples were collected in the period from June to August 2022. Furthermore, information on sociodemographic characteristics, health status, dietary behaviour and other lifestyle factors were collected by means of a self-administered questionnaire. To examine the association of PFOA blood serum levels with possible influencing factors, such as age, gender and consumption of fish and game meat, a logistic regression model with a PFOA value > 10 μg/l as outcome was used.

RESULTS

A total of 764 individuals participated in the follow-up study in 2022. Analyses were performed separately for the general population (n = 559), women of reproductive age (15-49 years old) (n = 120), and children under 12 years old (n = 30). Median PFOA blood levels have decreased by 56.9% in the general population, by 59.8% in the group of women of reproductive age and by 73.4% in the group of children under 12 years old. In the general population, a higher probability of a PFOA value > 10 μg/l was found for those aged 40-59 years (Odds ratio (OR) = 2.33 (95%CI: 1.23 to 4.43, p = 0.01) and those aged 60 years and older (OR = 5.32, 95%CI: 2.78 to 10.19, p < 0.001).

CONCLUSIONS

In all study groups, the median PFOA serum levels decreased as expected after a half-life of four years, which confirms that contamination via drinking water has ceased. Furthermore, our study identified age as a significant predictor of internal PFOA exposure, while no influence was found for the consumption of fish and game meat. Further investigations are needed to quantify in a more detailed way the influence of dietary habits on PFOA exposure.

Estimation of per- and polyfluoroalkyl substances (PFAS) half-lives in human studies: a systematic review and meta-analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) constitute a heterogeneous group of synthetic compounds widely used in industrial applications. The estimation of PFAS half-life (t1/2) is essential to quantify their persistence, their toxicity and mechanism of action in humans.

OBJECTIVES

The purpose of this review is to summarize the evidence on PFAS half-lives in humans from the available literature, and to investigate the limitations and uncertainties characterizing half-life estimation.

METHODS

The search was conducted on PubMed, Scopus, and Embase databases up to July 03, 2023 and was aimed at identifying all papers that estimated PFAS half-life in human populations. We excluded studies on temporal trends or providing estimates of half-life based solely on renal clearance. As persistent and ongoing exposures can influence half-life estimation, we decided to include only studies that were conducted after the main source of exposure to PFAS had ceased. A random-effects meta-analysis was conducted on studies that reported perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) or perfluorohexanesulfonic acid (PFHxS) half-life estimation. Risk of bias was evaluated using the OHAT tool.

RESULTS

A total of 13 articles were included in the review, with 5 studies conducted in exposed general populations and 8 studies conducted in exposed workers; the estimated mean half-life ranged from 1.48 to 5.1 years for PFOA, from 3.4 to 5.7 years for total PFOS, and from 2.84 to 8.5 years for PFHxS. High heterogeneity among studies was observed; potential reasons include the variability among the investigated populations, discrepancies in considering ongoing exposures, variability in PFAS isomeric compositions, accounting for background exposure, time since exposure stopped and methods used for half-life estimation.

DISCUSSION

Despite the efforts made to better understand PFAS toxicokinetics, further studies are needed to identify important characteristics of these persistent chemicals. Biomonitoring studies should focus on persistent and unaccounted sources of exposure to PFAS and on individual characteristics potentially determining half-life, to ensure accurate estimates.

Elevated Levels of Ultrashort- and Short-Chain Perfluoroalkyl Acids in US Homes and People

Per- and polyfluoroalkyl substances (PFAS) make up a large group of fluorinated organic compounds extensively used in consumer products and industrial applications. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), the two perfluoroalkyl acids (PFAAs) with 8 carbons in their structure, have been phased out on a global scale because of their high environmental persistence and toxicity. As a result, shorter-chain PFAAs with less than 8 carbons in their structure are being used as their replacements and are now widely detected in the environment, raising concerns about their effects on human health. In this study, 47 PFAAs and their precursors were measured in paired samples of dust and drinking water collected from residential homes in Indiana, United States, and in blood and urine samples collected from the residents of these homes. Ultrashort- (with 2 or 3 carbons [C2-C3]) and short-chain (with 4-7 carbons [C4-C7]) PFAAs were the most abundant in all four matrices and constituted on average 69-100% of the total PFAA concentrations. Specifically, trifluoroacetic acid (TFA, C2) and perfluoropropanoic acid (PFPrA, C3) were the predominant PFAAs in most of the samples. Significant positive correlations (n = 81; r = 0.23-0.42; p < 0.05) were found between TFA, perfluorobutanoic acid (PFBA, C4), and perfluoroheptanoic acid (PFHpA, C7) concentrations in dust or water and those in serum, suggesting dust ingestion and/or drinking water consumption as important exposure pathways for these compounds. This study demonstrates that ultrashort- and short-chain PFAAs are now abundant in the indoor environment and in humans and warrants further research on potential adverse health effects of these exposures.

Biomonitoring equivalents for perfluorooctanoic acid (PFOA) for the interpretation of biomonitoring data

BACKGROUND

Perfluorooctanoic acid (PFOA) is detected in the blood of virtually all biomonitoring study participants. Assessing health risks associated with blood PFOA levels is challenging because exposure guidance values (EGVs) are typically expressed in terms of external dose. Biomonitoring equivalents (BEs) consistent with EGVs could facilitate health-based interpretations.

OBJECTIVE

To i) derive BEs for serum/plasma PFOA corresponding to non-cancer EGVs of the U.S. Environmental Protection Agency (U.S. EPA), the Agency for Toxic Substances and Disease Registry (ATSDR) and Health Canada, and ii) compare with PFOA concentrations from national biomonitoring surveys.

METHODS

Starting from EGV points of departure, we employed pharmacokinetic data/models and uncertainty factors. Points of departure in pregnant rodents (U.S. EPA 2016, ATSDR) were converted into fetus and pup serum concentrations using an animal gestation/lactation pharmacokinetic model, and equivalent human fetus and child concentrations were converted into BEs in maternal serum using a human gestation/lactation model. The point of departure in adult rodents (Health Canada) was converted into a BE using experimental data. For epidemiology-based EGVs (U.S. EPA 2023, draft), BEs were directly based on epidemiological data or derived using a human gestation/lactation pharmacokinetic model. BEs were compared with Canadian/U.S. biomonitoring data.

RESULTS

Non-cancer BEs (ng/mL) were 684 (Health Canada, 2018) or ranged from 15 to 29 (U.S. EPA, 2016), 6-10 (ATSDR, 2021) and 0.2-0.8 (U.S. EPA, 2023, draft). Ninety-fifth percentiles of serum levels from the 2018-2019 Canadian Health Measures Survey (CHMS) and the 2017-2018 National Health and Nutrition Examination Survey (NHANES) were slightly below the BE for ATSDR, and geometric means were above the non-cancer BEs for the U.S. EPA (2023, draft).

CONCLUSION

Non-cancer BEs spanned three orders of magnitude. The lowest BEs were for EGVs based on developmental endpoints in epidemiological studies. Concentrations in Canadian/U.S. national surveys were higher than or close to BEs for the most recent non-cancer EGVs.

The EU's Per- and Polyfluoroalkyl Substances (PFAS) Ban: A Case of Policy over Science

The proposal by the European Chemicals Agency (ECHA) to ban over 12,000 per- and polyfluoroalkyl substances (PFAS) has sparked a debate about potential consequences for the economy, industry, and the environment. Although some PFAS are known to be harmful, a blanket ban may lead to significant problems in attempting to replace PFAS-based materials for environmental transition, as well as in medical devices and everyday products. Alternative materials may potentially be less safe, as a rush to replace PFAS would reduce the time needed for toxicological analyses. Studies have shown that PFAS exhibit a diverse range of mechanisms of action, biopersistence, and bioaccumulation potential, and should thus not be treated as a single group. This is particularly true for the class of fluoropolymers. A targeted approach that considers the specific risks and benefits of each chemical may be more effective. Moreover, the proposed ban may also have unintended consequences for the environment as PFAS use is also associated with benefits such as reducing greenhouse-gas emissions and improving energy efficiency. Policymakers must carefully weigh up the potential consequences before making a final decision on the ban.

A State-of-the-Science Review of Interactions of Per- and Polyfluoroalkyl Substances (PFAS) with Renal Transporters in Health and Disease: Implications for Population Variability in PFAS Toxicokinetics

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and have been shown to cause various adverse health impacts. In animals, sex- and species-specific differences in PFAS elimination half-lives have been linked to the activity of kidney transporters. However, PFAS molecular interactions with kidney transporters are still not fully understood. Moreover, the impact of kidney disease on PFAS elimination remains unclear.

OBJECTIVES

This state-of-the-science review integrated current knowledge to assess how changes in kidney function and transporter expression from health to disease could affect PFAS toxicokinetics and identified priority research gaps that should be addressed to advance knowledge.

METHODS

We searched for studies that measured PFAS uptake by kidney transporters, quantified transporter-level changes associated with kidney disease status, and developed PFAS pharmacokinetic models. We then used two databases to identify untested kidney transporters that have the potential for PFAS transport based on their endogenous substrates. Finally, we used an existing pharmacokinetic model for perfluorooctanoic acid (PFOA) in male rats to explore the influence of transporter expression levels, glomerular filtration rate (GFR), and serum albumin on serum half-lives.

RESULTS

The literature search identified nine human and eight rat kidney transporters that were previously investigated for their ability to transport PFAS, as well as seven human and three rat transporters that were confirmed to transport specific PFAS. We proposed a candidate list of seven untested kidney transporters with the potential for PFAS transport. Model results indicated PFOA toxicokinetics were more influenced by changes in GFR than in transporter expression.

DISCUSSION

Studies on additional transporters, particularly efflux transporters, and on more PFAS, especially current-use PFAS, are needed to better cover the role of transporters across the PFAS class. Remaining research gaps in transporter expression changes in specific kidney disease states could limit the effectiveness of risk assessment and prevent identification of vulnerable populations. https://doi.org/10.1289/EHP11885.

The variable associations between PFASs and biological aging by sex and reproductive stage in NHANES 1999-2018

BACKGROUND

Per- and polyfluoroalkyl substances (PFASs) are endocrine disrupting chemicals that have myriad effects on human physiology. Estrogenic PFASs may influence biological aging by mimicking the activity of endogenous estrogens, which can decrease inflammation and oxidative stress and enhance telomerase activity. We hypothesized that PFAS exposure would be differentially associated with measures of biological aging based on biological sex and reproductive stage.

METHODS

We analyzed associations between serum PFAS levels and measures of biological aging for pre- and postmenopausal women and men (n = 3193) using data from the 2003 to 2018 waves of the National Health and Nutrition Examination Survey. Examining PFASs both individually and in mixture models, we investigated four measures of clinical aging (Homeostatic Dysregulation, the Klemera-Doubal Method, Phenotypic Age Acceleration, and Allostatic Load), oxidative stress, and telomere length.

RESULTS

PFOA and PFOS were negatively associated with Phenotypic Age Acceleration (e.g. decelerated aging) for men B = -0.22, 95% CI: -0.32, -0.12; B = -0.04, 95% CI: -0.06, -0.03) , premenopausal women (B = -0.58, 95% CI: -0.83, -0.32; B = -0.15, 95% CI: -0.20, -0.09), and postmenopausal women (B= -0.22, 95% CI: -0.43, -0.01; B = -0.05, 95% CI: -0.08, -0.02). In mixture models, we found net negative effects for Phenotypic Age Acceleration and Allostatic Load for men, premenopausal women, and postmenopausal women. We also found significant mixture effects for the antioxidants bilirubin and albumin among the three sample groups. We found no evidence to support effects on telomere length.

DISCUSSION

Our findings suggest that PFAS exposure may be inversely associated with some measures of biological aging at the relatively low levels of exposure in this sample, regardless of reproductive stage and sex, which does not support our hypothesis. This research provides insights into how PFAS exposure may variably influence aging measures depending on the physiological process investigated.

Mixtures of per- and poly-fluoroalkyl substances (PFAS) reduce the in vitro activation of human T cells and basophils

In the last decades, per- and poly-fluoroalkyl substances (PFAS), widely used industrial chemicals, have been in the center of attention because of their omnipotent presence in water and soils worldwide. Although efforts have been made to substitute long-chain PFAS towards safer alternatives, their persistence in humans still leads to exposure to these compounds. PFAS immunotoxicity is poorly understood as no comprehensive analyses on certain immune cell subtypes exist. Furthermore, mainly single entities and not PFAS mixtures have been assessed. In the present study we aimed to investigate the effect of PFAS (short-chain, long-chain and a mixture of both) on the in vitro activation of primary human immune cells. Our results show the ability of PFAS to reduce T cells activation. In particular, exposure to PFAS affected T helper cells, cytotoxic T cells, Natural Killer T cells, and Mucosal associated invariant T (MAIT) cells, as assessed by multi-parameter flow cytometry. Furthermore, the exposure to PFAS reduced the expression of several genes involved in MAIT cells activation, including chemokine receptors, and typical proteins of MAIT cells, such as GZMB, IFNG and TNFSF15 and transcription factors. These changes were mainly induced by the mixture of both short- and long-chain PFAS. In addition, PFAS were able to reduce basophil activation induced by anti-FcεR1α, as assessed by the decreased expression of CD63. Our data clearly show that the exposure of immune cells to a mixture of PFAS at concentrations mimicking real-life human exposure resulted in reduced cell activation and functional changes of primary innate and adaptive human immune cells.

Estimating historical exposure to perfluoroalkyl acids in Security, Fountain, and Widefield Colorado: use of water-infrastructure blending and toxicokinetic models

Drinking water can be a major source of poly- and perfluoroalkyl substance (PFAS) exposure for humans. The lack of historic data on PFAS drinking-water concentrations and consumption patterns are a limiting factor for developing estimates of past exposure. Here, in contribution to a community-scale PFAS health effects study near fire training facilities that contaminated a local aquifer with PFASs, we present a novel water-infrastructure, mass-balance mixing model coupled to a non-steady state, single-compartment toxicokinetic model that used Monte Carlo simulations to estimate the start of PFAS exposure in drinking water for individuals within three PFAS-impacted communities in El Paso County, Colorado. Our modeling focused on perfluorohexane sulfonic acid (PFHxS) because median serum PFHxS concentrations in a sample of local residents (n = 213) were twelve times the median observed in the U.S. National Health and Nutrition Examination Survey (2015-2016). Modeling results for study participants were grouped according to their community of residence, revealing a median start of exposure for the town of Fountain of 1998 (25-75% interquartile range [IQR], 1992 to 2010), 2006 (IQR 1995 to 2012) for Security, and 2009 (IQR 1996-2012) for Widefield. Based on the towns' locations relative to an identified hydraulically upgradient PFAS source, the modeled exposure sequencing does not completely align with this conceptual flow model, implying the presence of an additional PFAS source for the groundwater between Widefield and Fountain.

Co-variate adjusted associations between serum concentrations of selected perfluoroalkyl substances and urinary concentrations of selected arsenic species

Data from National Health and Nutrition Examination Survey for 2011-2012 were used to estimate associations of the serum concentrations of perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluoroundecanoic acid (PFUnDA), and 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (Me-PFOSA) with urinary concentrations of total arsenic (UAS), inorganic arsenic (IAS), arsenobetaine (UAB), and dimethyl arsinic acid (UDMA) among US adults aged >  = 20 years. Concentrations of PFNA were positively associated with all four arsenic variables but statistical significance was observed for IAS only (β = 0.33364, P = 0.04). Concentrations of PFDA were positively associated with UAS (β = 0.20688, P = 0.01), IAS (β = 0.23712, P = 0.02), and UAB (β = 0.26049, P = 0.02). Concentrations of PFUnDA were positively associated with UAS (β = 0.49946, P < 0.01), IAS (β = 0.51782, P < 0.01), UAB (β = 0.62924, P < 0.01), and UDMA (β = 0.26375, P < 0.01). Concentrations of Me-PFOSA with PFAS were inversely associated with every PFAS but statistical significance was observed for UDMA only (β =  - 0.05613, P = 0.03). PFOA, PFHxS, and PFOS were, in general, negatively associated with concentrations of all four arsenic variables but without reaching statistical significance. Positive associations of PFDA, PFNA, and PFUnDA with arsenic necessitate investigation about impact of the co-exposure of these PFAS with arsenic and their impact on health. Fluorinated carbon chain length > 8 as opposed to ≤ 8 may have a role in defining associations of PFAS with arsenic.

A Scoping Assessment of Implemented Toxicokinetic Models of Per- and Polyfluoro-Alkyl Substances, with a Focus on One-Compartment Models

Toxicokinetic (TK) models have been used for decades to estimate concentrations of per-and polyfluoroalkyl substances (PFAS) in serum. However, model complexity has varied across studies depending on the application and the state of the science. This scoping effort seeks to systematically map the current landscape of PFAS TK models by categorizing different trends and similarities across model type, PFAS, and use scenario. A literature review using Web of Science and SWIFT-Review was used to identify TK models used for PFAS. The assessment covered publications from 2005-2020. PFOA, the PFAS for which most models were designed, was included in 69 of the 92 papers, followed by PFOS with 60, PFHxS with 22, and PFNA with 15. Only 4 of the 92 papers did not include analysis of PFOA, PFOS, PFNA, or PFHxS. Within the corpus, 50 papers contained a one-compartment model, 17 two-compartment models were found, and 33 used physiologically based pharmacokinetic (PBTK) models. The scoping assessment suggests that scientific interest has centered around two chemicals-PFOA and PFOS-and most analyses use one-compartment models in human exposure scenarios.

Longitudinal measurements of per- and poly-fluoroalkyl substances (PFAS) in archived human serum samples between 1975 and 1995 in Australia

Per- and poly-fluoroalkyl substances (PFAS) are a group of manmade compounds produced since the 1950 s and used in a range of industrial processes and consumer products. In Australia, PFAS serum concentrations have been measured in the general population since 2002. However, few studies have retrospectively measured PFAS concentrations in serum samples representative of a general population prior to 2000, none of which have been conducted in Australia. To understand the general population's exposure to PFAS prior to 2002, longitudinal PFAS serum concentration measurements are required. In the current study, we accessed 'The Busselton Health Study Data Bank' to analyse archived serum samples for PFAS. Repeat serum samples collected in 1975, 1981 and 1995 were obtained from 17 participants. Of the 35 PFAS analysed, 13 PFAS were detected in the serum samples collected in 1975. Both the detection frequency and ∑PFAS serum concentrations increased between 1975 and 1995. Median ∑PFAS serum concentration increased over 7-fold; from 3.3 ng/mL in 1975-26 ng/mL in 1995. The increase in serum concentrations reflects the global production history of these PFAS during this period in time.

Perfluoroalkyl and polyfluoroalkyl substances in cord serum of newborns and their potential factors

The demonstrated developmental and reproductive toxicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), coupled with the increasing production and use of emerging per- and polyfluoroalkyl substances (PFASs) has resulted in progressively higher human exposure levels. This has raised concerns about PFAS exposure levels in the fetus, which is highly susceptible to the potential effects of hazardous environmental chemicals. However, in utero exposure to PFASs and health implications have not been fully characterized in China. To fill this gap, we analyzed 19 PFASs in umbilical cord serum samples (n = 66). Information about the mothers and newborns was obtained through questionnaires. Associations between maternal characteristics and neonatal birth weight and PFAS concentrations were analyzed using nonparametric tests. As results, PFOA was detected in all serum samples. The highest median concentration of PFOS in umbilical serum was 1.092 ng·mL^-1, followed by perfluoropentanoic acid (median: 0.633 ng·mL^-1). Trifluroacetic acid and perfluoropropanoic acid were detected in cord serum for the first time, and their median concentrations were 0.229 and 0.266 ng·mL^-1, respectively. Neonatal birth weight was negatively correlated with long-chain PFOS (r = -0.319, P < 0.05), and the concentrations of perfluoroundecanoic acid and perfluorododecanoic acid were significantly different between the birth weight groups. Maternal age, maternal education, diet, and nutritional supplementation during pregnancy can all affect umbilical serum exposure to PFASs. These results demonstrate that legacy PFASs remain major contributors to the composition of human PFASs, while the concentration levels of emerging short-chain alternatives have increased significantly. Modifying the mother's diet may reduce the risk of intrauterine PFAS exposure. Special attention to exposure to highly novel PFASs and confirmation of potential determinants should be taken as a priority in the plan for risk management and actions in this area.

Computational estimates of daily aggregate exposure to PFOA/PFOS from 2011 to 2017 using a basic intake model

BACKGROUND

Human exposure to per- and polyfluoroalkyl substances has been modeled to estimate serum concentrations. Given that the production and use of these compounds have decreased in recent years, especially PFOA and PFOS, and that additional concentration data have become available from the US and other industrialized countries over the past decade, aggregate median intakes of these two compounds were estimated using more recent data.

METHODS

Summary statistics from secondary sources were collected, averaged, and mapped for indoor and outdoor air, water, dust, and soil for PFOA and PFOS to estimate exposures for adults and children. European dietary intake estimates were used to estimate daily intake from food.

RESULTS

In accordance with decreased concentrations in media, daily intake estimates among adults, i.e., 40 ng/day PFOA and 40 ng/day PFOS, are substantially lower than those reported previously, as are children's estimates of 14 ng/day PFOA and 17 ng/day PFOS. Using a first-order pharmacokinetic model, these results compare favorably to the National Health and Nutrition Examination Survey serum concentration measurements.

CONCLUSION

Concomitant blood concentrations support this enhanced estimation approach that captures the decline of PFOA/PFOS serum concentration over a decade.

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.

Enhanced toxicity effects of iron particles together with PFOA in drinking water

Iron particles present in drinking water distribution systems (DWDSs) could cause discoloration, while organic pollutants in DWDSs, such as perfluorooctanoic acid (PFOA), could be enriched by iron particles. However, little is known about the enhanced effects of PFOA and iron particles in DWDSs. To fill in these knowledge gaps, herein, iron-PFOA (FEP) particles were generated using residual chlorine as an oxidant in drinking water conditions and then separated into different sizes (ranging from small to large: FEP-S, FEP-M ，and FEP-L). FEP-S harbored the greatest cytotoxicity among the sizes. Interestingly, our data revealed that the PFOA released from FEP particles transformed into PFOS (perfluorooctane sulfonate) upon digestion in the gastrointestinal environment (GI), and FEP-L bored the strongest transformation, showing a toxicity profile that was distinct from that of FEP-S. Furthermore, mechanistic studies revealed that FEP per se should be accountable for the conversion of PFOA to PFOS dependent on the generation of hydroxyl radicals (·OH) in GI, and that FEP-L revealed the greatest production of ·OH. Collectively, these results showed how iron particles and PFOA could result in enhanced toxicity effects in drinking water: (i) PFOA could increase the toxicity of iron particles by reducing particle size and inducing higher generation of ·OH; (ii) iron particles could induce the transformation of PFOA into more toxic PFOS through digestion.

Associations between the concentrations of α-klotho and selected perfluoroalkyl substances in the presence of eGFR based kidney function and albuminuria: Data for US adults aged 40-79 years

Exposures to per- and polyfluoroalkyl substances (PFAS) cause oxidative stress, a risk factor for tissue damage leading to kidney and cardiovascular diseases. The antiaging protein klotho is known to act as an anti-oxidative agent, and how klotho homeostasis interacts with PFAS has not been reported. This study among 3981 US adults aged 40-79 years old evaluated relationships of internal PFAS contamination to α-klotho across stages of estimated glomerular filtration rate or eGFR-based kidney function and albuminuria defined as urinary albumin creatinine ratio of >30 mg/g creatinine. In the absence of albuminuria and when eGFR based kidney function was in stage GF-1 (eGFR ≥ 90 mL/min/1.73 m²), statistically significant inverse associations between α-klotho and PFNA (β = -0.04930, p < 0.01), PFDA (β = -0.03307, p = 0.02), and PFUnDA (β = -0.03451, p = 0.01), PFHxS (β = -0.03011, p = 0.04) and PFOS (β = -0.03126, p = 0.03) were noted. No associations between α-klotho and PFAS were observed when kidney function was in stages GF-2 (60 ≤ eGFR < 90 mL/min/1.73 m²) or GF-3A (45 ≤ eGFR < 60 mL/min/1.73 m²) in the presence or absence of albuminuria. Unexpectedly, however, in the absence of albuminuria, with kidney function in stage GF-3B/4 (15 ≤ eGFR < 45 mL/min/1.73 m²), associations were positive between α-klotho and PFOA (β = 0.20989, p < 0.01), PFNA (β = 0.18373, p < 0.1), PFDA (β = 0.20413, p < 0.01), PFUnDA (β = 0.17660, p < 0.01), and PFOS (β = 0.14267, p < 0.01). The inverse relationship of PFAS to the antioxidant protein α-klotho in those with healthy kidney function has not been previously reported and should be evaluated in other populations.

Remediation of poly-and perfluoroalkyl substances (PFAS) contaminated soil using gas fractionation enhanced technology

This study investigated a gas fractionation enhanced soil washing method for poly-and perfluoroalkyl substances (PFAS) removal from contaminated soil. With the assistance of gas fractionation, PFAS removal was increased by a factor of 9, compared to the conventional soil washing method. Pre-extraction (pre-treatment) of the soil with water before gas fractionation enhanced PFAS removal from soil. The optimum extraction time varied based on the soil particle size, since it will change the swelling time of the soil. The influence of various operational conditions such as water to soil mass ratio (W:S ratio), gas type in fractionation, gas flowrate, fractionation time and soil pre-treatment condition have been studied to identify the critical influencing factors. Among various W:S ratios (2, 4, 5, 6, 8, and 10) studied, higher W:S ratio resulted in better PFAS removals, but PFAS removal began to plateau as the W:S ratio increased. PFAS removal could be improved by repeated treatment with low water consumption. Air, oxygen, and ozone generated by air and oxygen were used, in which ozone generated by oxygen achieved the highest PFAS removals of 55.9%. Among different fractionation times (10 min, 20 min and 30 min), a fractionation time of 20 min achieved better total PFAS removal for studied soil, because PFOS was the dominant species in the total PFAS. However, the removal of some PFAS species, such as PFHxS, would be increased with extended fractionation time. With constant fractionation time (10 min), PFAS removal performance improved with the increasing gas flowrate.

Human exposure pathways to poly- and perfluoroalkyl substances (PFAS) from indoor media: A systematic review

BACKGROUND

Human exposure to per- and polyfluoroalkyl substances (PFAS) has been primarily attributed to contaminated food and drinking water. There is information indicating other sources and pathways of exposure in residential environments, but few studies report relationships between these indoor media and human biomonitoring measurements.

METHODS

This study adapts existing systematic review tools and methodologies to synthesize evidence for PFAS exposure pathways from indoor environment media including consumer products, household articles, cleaning products, personal care products, and indoor air and dust. Studies were identified using innovative machine learning approaches and pathway-specific search strings to reduce time needed for literature search and screening. The included studies and systematic review were evaluated using tools modified specifically for exposure studies. The systematic review was conducted following a previously published protocol (DeLuca et al., 2021) that describes the systematic review methodology used in detail.

RESULTS

Only 7 studies were identified that measured the targeted subset of 8 PFAS chemicals in concordant household media (primarily house dust) and participant serum. Data extracted from the included studies were used to calculate exposure intake rates and estimate a percentage of occupant serum concentrations that could be attributed to the indoor exposure pathways. These calculations showed that exposure to PFOA, PFOS, PFNA, and PFHxS from contaminated house dust could account for 13%, 3%, 7%, and 25% of serum concentrations, respectively. Inhalation of PFAS in indoor air could account for less than 4% of serum PFOA concentrations and less than 2% of serum PFOS and PFNA concentrations. A risk of bias was identified due to participant profiles in most of the studies being skewed towards white, female, and higher socioeconomic status.

CONCLUSIONS

Along with synthesizing evidence for estimated contributions to serum PFAS levels from indoor exposure media, this systematic review also identifies a consistent risk of bias across exposure study populations that should be considered in future studies. It highlights a major research gap and need for studies that measure concordant data from both indoor exposure media and participant serum and the need for continued research on exposure modeling parameters for many PFAS chemicals.

Short-term exposure to perfluorotetradecanoic acid affects the late-stage regeneration of Leydig cells in adult male rats

Perfluorotetradecanoic acid (PFTeDA) is one of perfluoroalkyl substances widely found in the environment. PFTeDA may cause the dysfunction of male reproductive system. However, whether PFTeDA affects the regeneration of Leydig cells remains unclear. The objective of this study was to examine the effects of short-term exposure of PFTeDA on the late-stage maturation of Leydig cells. Fifty-four adult Sprague-Dawley male rats were daily gavaged with PFTeDA (0, 10, or 20 mg/kg body weight) for 10 days, and then were injected intraperitoneally with ethylene dimethane sulfonate (EDS, 75 mg/kg body weight/once) to ablate Leydig cells to induce their regeneration. On day 21 (early stage) and 56 (late stage) after EDS, hormone levels, gene expression, and protein levels were measured. PFTeDA did not affect the early stage of Leydig cell regeneration, because it had no effect on serum testosterone, luteinizing hormone, and follicle-stimulating hormone levels, Leydig cell number, and its gene and protein expression. PFTeDA significantly reduced serum testosterone level and down-regulated the expression of Leydig cell genes (Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Hsd11b1, and Insl3) and their proteins (CYP11A1, HSD3B1, CYP17A1, HSD17B3, and INSL3), decreased the phosphorylation of AKT1 and ERK1/2, as well as lowered sperm count in the epididymis at 20 mg/kg. In conclusion, short-term exposure to PFTeDA blocks the late-stage maturation of Leydig cells.

Chlorinated polyfluoroalkyl ether sulfonic acids in fish, dust, drinking water and human serum: From external exposure to internal doses

Exposure to per- and polyfluoroalkyl substances (PFASs) has raised significant public health concerns due to their persistence and toxicity in the human body. Here, we aimed to investigate the characteristics of exposure to chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) and legacy PFASs and the relative contribution from different external pathways to human exposure. Three Cl-PFESAs and fourteen legacy PFASs were detected in human serum, fish, indoor dust and drinking water collected from Shijiazhuang, China. Results showed that 6:2 Cl-PFESA was the third most predominant compound, with an average concentration of 2.70 ng/mL in serum, which was lower than those of perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) (14.79 and 4.91 ng/mL). The estimated daily intake of 6:2 Cl-PFESA via dust ingestion (mean: 0.008 ng/kg bw/day) was found to be highest among all detected PFASs, while the highest value via fish and drinking water was found for PFOS and PFOA (0.438-9.799 and 0.034-0.155 ng/kg bw/day), respectively. The similar composition of PFASs between serum and fish suggests that fish consumption is a major contributor to human exposure to PFASs. However, the increasing ratios of EDI_{indoor dust}/EDI_fish for PFOS, PFOA and 6:2 Cl-PFESA indicated that the contribution of dust ingestion for PFASs, especially 6:2 Cl-PFESA, could not be ignored. The modeled serum concentrations of 6:2 Cl-PFESA higher than its observed levels hint at its gradually increasing exposure levels in the general population. Combined with the lower modeled levels of PFOS than the observed levels, the substituent with 6:2 Cl-PFESA for PFOS is obvious in China. Therefore, further studies on contributions from more detailed external sources and risk assessments of Cl-PFESAs are recommended, especially for some vulnerable subpopulations, considering their widespread exposure and similar environmental behaviors compared with those of their predecessors.

The Dilemma of perfluorooctanoate (PFOA) human half-life

Disparity in the results from human observational and clinical studies is not uncommon, but risk assessment efforts often judge one set of data more relevant with the loss of valuable information. The assessment for perfluorooctanoate (PFOA) is a good example of this problem. The estimation of its safe dose is disparate among government groups due in part to differences in understanding of its half-life in humans. These differences are due in part to incomplete information on sources of exposure in the human observational half-life studies, which have been routinely acknowledged, but until recently not well understood. Exposure information is thus critical in understanding, and possibly resolving, this disparity in PFOA safe dose, and potentially for disparities with similar chemistries when both human observational and clinical findings are available. We explore several hypotheses to explain this disparity in PFOA half-life from human observational studies in light of findings of a clinical study in humans and relevant exposure information from a recent international meeting of the Society of Toxicology and Environmental Chemistry (SETAC). Based on information from both human observational studies and clinical data, we proposed a range for the half-life for PFOA of 0.5-1.5 years, which would likely raise many existing regulatory safe levels if all other parameters stayed the same.

Associations between perfluoroalkyl acids in serum and lead and mercury in whole blood among US children aged 3-11 years

Data for 639 US children aged 3-11 years who participated in the National Health and Nutrition Examination Survey during 2013-2014 were analyzed by fitting regression models with log10-transformed values of blood lead and methyl and total mercury as dependent variables and log10-transformed values of perfluoroalkyl acids (PFAA) as one of the independent variables. PFAAs considered were 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (MPAH), linear isomer of perfluorooctanoic acid (NPFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), linear isomer of perfluorooctane sulfonic acid (NPFOS), and monomethyl branch isomer of perfluorooctane sulfonic acid (MPFOS). Adjusted regression slopes (β) indicating associations between the concentrations of PFAAs with blood lead and mercury were estimated. Statistically significant associations between concentrations of each PFAA and blood lead were observed. For 10% increases in concentrations of MPAH, NPFOA, PFNA, PFDA, PFHxS, NPFOS, and MPFOS, percent increases in the concentrations of blood lead were 0.45%, 1.59%, 0.78%, 0.32%, 0.65%, 1.32%, and 0.89% respectively. For 10% increases in concentrations of MPAH, PFNA, PFDA, and NPFOS, percent increases in the concentrations of total mercury in the blood were 1.62%, 1.44%, and 3.24% respectively. For 10% increases in concentrations of PFDA and NPFOS, percent increases in the concentrations of methyl mercury in the blood were 2.07% and 4.57% respectively. While concentrations of each of the seven PFAAs were positively associated with the concentrations of blood lead, concentrations of only PFDA and NPFOS were positively associated with increases in total and methyl mercury. PFAAs having positive associations with lead and mercury imply co-exposure and/or co-existence of high concentrations of PFAAs and lead/mercury. Since PFAAs as well as lead/mercury are known to be neurotoxic, nephrotoxic, and endocrine disruptors, their co-existence/co-exposure may lead to neurodevelopmental deficits that are additive/synergistic than neurodevelopmental deficits associated with exposures to PFAAs and lead/mercury alone. Future studies are needed to investigate additive/synergistic neurodevelopmental deficits associated with co-exposures to PFAAs and lead/mercury.

Associations between concentrations of selected perfluoroalkyl acids and concentrations of blood cadmium, lead, and total mercury

Data (N = 2552) from National Health and Nutrition Examination Survey for US adults aged ≥ 20 years for 2011-2016 were analyzed to estimate the associations between the concentrations of blood cadmium, lead, and total mercury and the concentrations of seven perfluoroalkyl acids (PFAA), namely, 2-(N-Methyl-perfluorooctane sulfonamido) acetic acid (MPAH), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS). Concentrations of blood cadmium were negatively associated with the concentrations of PFHxS (β = - 0.05428, p < 0.01) and PFOS (β = - 0.0212, p = 0.02). Concentrations of blood lead were positively associated with the concentrations of MPAH (β = 0.03301, p < 0.01), PFOA (β = 0.04783, p = 0.01), PFNA (β = 0.11761, p < 0.01), PFDA (β = 0.08007, p < 0.01), PFUA (β = 0.11382, p < 0.01), and PFOS (β = 0.04996, p = 0.02). Percent increases in the concentration of blood lead were 0.32%, 0.46%, 1.13%, 0.77%, 1.09%, and 0.48% for 10% increases in the concentrations of MPAH, PFOA, PFNA, PFDA, PFUA, and PFOS, respectively. Concentrations of blood total mercury were positively associated with the concentrations of PFNA (β = 0.37105, p < 0.01), PFDA (β = 0.46875, p < 0.01), PFUA (β = 0.56934, p < 0.01), and PFOS (β = 0.17557, p < 0.01). Percent increases in the concentration of blood total mercury were 3.6%, 4.57%, 5.58%, and 1.69% for 10% increases in the concentrations of PFNA, PFDA, PFUA, and PFOS, respectively. Associations between the concentrations of PFAAs with blood total mercury were substantially stronger than the concentrations with blood lead. Higher the carbon chain length for PFAAs, stronger were the associations between PFAAs with lead and mercury.

Impact of kidney hyperfiltration on concentrations of selected perfluoroalkyl acids among US adults for various disease groups

Data from the National Health and Nutrition Examination Survey (N = 6141) for the years 2003-2016 for US adults were analyzed to evaluate the impact of glomerular hyperfiltration on the observed concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid, perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) for several disease groups. Hyperfiltrators were defined as having an estimated glomerular filtration rate (eGFR) ≥ 110 mL/min/1.73 m², and normal filtrators were defined as those having an eGFR between 90 and 110 mL/min/1.73 m². The seven disease groups for which the data were analyzed were as follows: those (i) without any diseases; (ii) with hypertension only; (iii) with albuminuria only; (iv) with anemia only; (v) with diabetes only; (vi) with hypertension and one or more of diabetes, anemia, and albuminuria; and (vii) with two or more of diabetes, anemia, and albuminuria without hypertension. For almost every PFAA, for all seven disease groups except the albuminuria only group, hyperfiltrators had lower adjusted geometric means (AGM) than normal filtrators. For example, for the disease group with hypertension only, for PFOS, the AGMs for hyperfiltrators and normal filtrators were 8.3 and 10.6 ng/mL, respectively, for the total population. For the group with albuminuria only, normal filtrators were found to have higher AGMs than hyperfiltrators for the total population and males. For example, for PFHxS, the AGMs for normal and hyperfiltrators were 0.98 and 1.05 ng/mL, respectively, for the total population. For females, these AGMs for normal and hyperfiltrators were 0.96 and 0.86 ng/mL respectively. Males usually had higher AGMs than females, but the reverse was also true occasionally. Usually, male-female differences were substantially narrower for normal filtrators than hyperfiltrators. Irrespective of the filtration status, the disease group with hypertension only had the highest AGMs for every PFAA. AGMs for the anemia only group were the lowest for every PFAA as compared with other disease groups among hyperfiltrators.

Per- and Polyfluoroalkyl Substances in Human Serum Samples of Selected Populations from Ghana

The aims of this study were to assess serum concentrations of per- and polyfluoroalkyl substances (PFASs) in selected populations from Ghana, including workers engaged in the repair of electronic equipment (ERWs), and to elucidate PFAS concentrations in relation to blood mercury concentrations (B-Hg) as a biomarker of seafood consumption. In all, 219 participants were recruited into the study, of which 26 were women and 64 were ERWs. Overall, the PFAS concentrations were low. The most abundant components were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS). Women had generally lower PFAS concentration than men. The ERWs had statistically significantly higher concentrations of perfluorooctanoate (PFOA), which was associated with the concentration of tin in urine. This could indicate exposure during soldering. The concentration of B-Hg was associated with several of the PFASs such as PFOA, PFOS and perfluoroheptane sulfonate (PFHpS). Additionally, the concentrations of perfluorodecanoic acid (PFDA) and perfluoroundecanoate (PFUnDA) were highly associated with the concentrations of B-Hg. It is noteworthy that the linear isomer of PFHxS was strongly associated with B-Hg while the branched isomers of PFHxS were not. In conclusion, the PFAS concentrations observed in the present study are low compared to other populations previously investigated, which also reflects a lower PFAS exposure within the Ghanaian cohorts. ERWs had significantly higher PFOA concentrations than the other participants. Several PFASs were associated with B-Hg, indicating that seafood consumption may be a source of PFAS exposure.

Environmental and dietary exposure of perfluorooctanoic acid and perfluorooctanesulfonic acid in the Nakdong River, Korea

This study performed the first environmental and dietary exposure assessment to explore plant uptake of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from agricultural soil and irrigation water in the Nakdong River delta, South Korea. Annual average concentrations of total PFOA and PFOS ranged from 0.026 to 0.112 µg L^-1 (irrigation water), and from 0.818 to 1.364 µg kg^-1 (soil), respectively. PFOA and PFOS hotspots were identified downstream of the Nakdong River and were influenced by seasonal climatic variations. The observed average biennial concentration of the sum of PFOA and PFOS decreased in irrigation water, from 0.112 µg L^-1 in 2013 to 0.026 µg L^-1 in 2015, suggests that the 2013 Persistent Organic Pollutants Control Act may have helped to reduce levels of PFAS at this location. This study calculated some of the highest plant uptake factors reported to date, with values ranging from 0.962 in green onions to < 0.004 in plums. Leafy vegetables and rice are important components of the Korean diet; these groups had the largest contribution to the estimated dietary intake of PFOA and PFOS, which was calculated at 0.449 and 0.140 ng kg _bw ^-1 day^-1, respectively. This corresponded to 66.4% for PFOA and 7.9% for PFOS of the EFSA reference dose (RfD). The dietary intake of PFOA and PFOS from crops alone did not exceed the RfD. However, when the estimated daily intake (EDI) from other sources such as tap water, meat, fish, dairy, and beverages was included in the exposure risk assessment, both of the EDIs to PFOA and PFOS exceeded the RfDs, indicating that there may be a risk to human health. This study concludes that consumption of crops might, therefore, be a significant and underappreciated pathway for human exposure to PFAS.

Biomarkers, matrices and analytical methods targeting human exposure to chemicals selected for a European human biomonitoring initiative

The major purpose of human biomonitoring is the mapping and assessment of human exposure to chemicals. The European initiative HBM4EU has prioritized seven substance groups and two metals relevant for human exposure: Phthalates and substitutes (1,2-cyclohexane dicarboxylic acid diisononyl ester, DINCH), bisphenols, per- and polyfluoroalkyl substances (PFASs), halogenated and organophosphorous flame retardants (HFRs and OPFRs), polycyclic aromatic hydrocarbons (PAHs), arylamines, cadmium and chromium. As a first step towards comparable European-wide data, the most suitable biomarkers, human matrices and analytical methods for each substance group or metal were selected from the scientific literature, based on a set of selection criteria. The biomarkers included parent compounds of PFASs and HFRs in serum, of bisphenols and arylamines in urine, metabolites of phthalates, DINCH, OPFRs and PAHs in urine as well as metals in blood and urine, with a preference to measure Cr in erythrocytes representing Cr (VI) exposure. High performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was the method of choice for bisphenols, PFASs, the HFR hexabromocyclododecane (HBCDD), phenolic HFRs as well as the metabolites of phthalates, DINCH, OPFRs and PAHs in urine. Gas chromatographic (GC) methods were selected for the remaining compounds, e.g. GC-low resolution MS with electron capture negative ionization (ECNI) for HFRs. Both GC-MS and LC-MS/MS were suitable for arylamines. New developments towards increased applications of GC-MS/MS may offer alternatives to GC-MS or LC-MS/MS approaches, e.g. for bisphenols. The metals were best determined by inductively coupled plasma (ICP)-MS, with the particular challenge of avoiding interferences in the Cd determination in urine. The evaluation process revealed research needs towards higher sensitivity and non-invasive sampling as well as a need for more stringent quality assurance/quality control applications and assessments.

Impact of the co-occurrence of obesity with diabetes, anemia, hypertension, and albuminuria on concentrations of selected perfluoroalkyl acids

Data (N = 10644) for US adults aged ≥20 years for 2003-2016 from National Health and Nutrition Examination Survey were analyzed to evaluate the impact of co-occurrence of obesity with diabetes, anemia, albuminuria, and hypertension on concentrations of five perfluoroalkyl acids (PFAA), namely, perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA). For the total population, males, and females, co-occurrence of obesity with hypertension, albuminuria, anemia, and diabetes was found to be associated with lower adjusted geometric means (AGM) than nonobese for every PFAA. For example for females, for PFOS, AGMs for obese with no diseases, hypertension, albuminuria, anemia, and diabetes were 8.2, 10.8, 5.8, 4.6, and 7.7 ng/mL respectively. In comparison, for PFOS, for nonobese females, AGMs for those with no diseases, hypertension, albuminuria, anemia, and diabetes were found to be 8.9, 13.4, 7.7, 6.0, and 10.2 ng/mL respectively. This implies obesity is associated with higher excretion rates. Females, in general, had lower AGMs than males for both obese and nonobese for every PFAA for every disease group. For example, percent ratios of obese females to males AGMs for PFOA were 66.7%, 87.1%, 88.2%, 70.6%, and 90% for those with no diseases, hypertension, albuminuria, anemia, and diabetes respectively. The ratios of obese to nonobese AGMs for females were lower than males for every PFAA for those with no diseases and hypertension only. For example, for PFOA for those with no diseases, obese to nonobese AGM ratios were 87% for females and 100% for males. Thus, additional excretion of certain PFAAs due to obesity is higher in females than males for those with no diseases and hypertension only.

Effect of Perfluorooctanoic Acid on the Epigenetic and Tight Junction Genes of the Mouse Intestine

Perfluorooctanoic acid (PFOA) has been implicated in various toxicities including neurotoxicity, genotoxicity, nephrotoxicity, epigenetic toxicity, immunotoxicity, reproductive toxicity, and hepatotoxicity. However, information on the accumulation of PFOA in the intestine and its toxic effects on intestinal epigenetics and tight junction (TJ) genes is sparse. CD1 mice were dosed with PFOA (1, 5, 10, or 20 mg/kg/day) for 10 days, and its accumulation and induced alterations in the expression of epigenetic and tight junction genes in the small intestine and colon were evaluated using LC-MS and qPCR techniques. PFOA reduced the expression levels of DNA methyltransferases (Dnmt1, Dnmt3a, Dnmt3b) primarily in the small intestine whereas, in the colon, a decrease was observed only at high concentrations. Moreover, ten-eleven translocation genes (Tet2 and Tet3) expression was dysregulated in the small intestine, whereas in the colon Tets remained unaffected. The tight junction genes Claudins (Cldn), Occludin (Ocln), and Tight Junction Protein (Tjp) were also heavily altered in the small intestine. TJs responded differently across the gut, in proportion to PFOA dosing. Our study reveals that PFOA triggers DNA methylation changes and alters the expression of genes essential for maintaining the physical barrier of intestine, with more profound effects in the small intestine compared to the colon.

Associations between selected perfluoroalkyl acids in serum and hemoglobin in whole blood, a biomarker of anemia: Impact of deteriorating kidney function

Data (N = 11251) from National Health and Nutrition Examination Survey (NHANES) for 2003-2016 for US adults aged ≥20 years were stratified by gender and anemia and analyzed to evaluate the associations between the concentrations of whole blood hemoglobin (WBHGB) and selected perfluoroalkyl acids (PFAAs) in serum by stages of glomerular filtration (GF). Investigated PFAAs were perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA). Females with whole blood hemoglobin concentrations <12 g/dL and males with whole blood hemoglobin concentrations <13 g/dL were classified as being anemic. Regression models with log10 transformed concentrations of whole blood hemoglobin as dependent variable and age, poverty income ratio, body mass index, serum cotinine, daily alcohol intake, survey year, and log10 concentrations of one of the PFAA as independent variables were fitted. For anemic females, association between WBHGB and PFAA concentrations were uniformly positive across worsening stages of renal failure and percent increases for 10% increases in PFAAs varied between 0.03% and 0.39%. For anemic males, association between WBHGB and PFAA concentrations were positive except at GF-3A (45 ≤ eGFR<60 mL/min/1.73 m²) and percent increases for 10% increases in PFAAs varied between 0.02% and 0.53%. Thus, more often than not, presence of positive associations between WBHGB and PFAA among anemics imply elevated levels of PFAA are associated with higher levels of WBHGB. Similar results were observed for non-anemic males and females, however strengths of associations between whole blood hemoglobin and PFAAs were several fold higher among anemic compared to non-anemic participants. Hemoglobin is consistently associated with serum PFAAs.

Determinants of serum concentrations of perfluoroalkyl acids (PFAAs) in school children and the contribution of low-level PFAA-contaminated drinking water

Little is known about the demographic/life-style/physiological determinants explaining the variation of serum perfluoroalkyl acid (PFAA) concentrations in children. We identified significant determinants in children and investigated the influence of low-level PFAA-contaminated drinking water (DW) (<10 ng L-1 of single PFAAs) on serum concentrations. Four perfluorosulfonic acids (PFSAs) and 11 perfluorocarboxylic acids (PFCAs) were analyzed in serum from 5th grade children from 11 Swedish schools (N = 200; average age: 12 years) using liquid chromatography-tandem-mass-spectrometry. Data on demography and life-style/physiological factors were obtained by questionnaires. PFAA concentrations in raw and drinking water (DW) were obtained from the water works supplying DW to the schools. In multiple regression analyses school was the determinant contributing most to the variation in PFAA concentrations, with the lowest contribution for PFHpA (10%) and the highest for PFHxS (81%). Girls had lower adjusted mean concentrations of PFHxS, PFOS, PFNA and PFDA than boys, but a higher concentration of PFHxA. Girls reporting onset of menstruation had lower PFHxS and PFOA concentrations than other girls, suggesting menstrual bleeding elimination. Children born by mothers from less industrialized countries had lower mean concentrations of both PFSAs and PFCAs than children with mothers from highly industrialized countries, suggesting differences in early-life exposure. Life-style factors associated with paternal education levels appeared to influence PFAA concentrations differently than maternal education level. Already at an average DW PFHxS concentration of 2 ng L-1, children had a significantly higher adjusted mean serum PFHxS concentration than at an average DW concentration of <1.6 ng PFHxS L-1. Similar results were observed for PFOS and PFOA. The DW variable explained 16% (PFOA) to 78% (PFHxS) of the variation in serum PFAA concentrations, suggesting that low-level-contaminated DW is a significant source of exposure for children in Sweden. Although some of the associations, especially those with menstruation and maternal birth country, should be interpreted with extra caution due to the small size of the study, the results contribute to future work on identifying populations of children at risk of elevated PFAA exposures.

Dietary characteristics associated with plasma concentrations of per- and polyfluoroalkyl substances among adults with pre-diabetes: Cross-sectional results from the Diabetes Prevention Program Trial

Diet is assumed to be the main source of exposure to per- and polyfluoroalkyl substances (PFAS) in non-occupationally exposed populations, but studies on the diet-PFAS relationship in the United States are scarce. We extracted multiple dietary variables, including daily intakes of food group, diet scores, and dietary patterns, from self-reported dietary data collected at baseline (1996-1999) from adults with pre-diabetes enrolled in the Diabetes Prevention Program, and used linear regression models to evaluate relationships of each dietary variable with plasma concentrations of six PFAS (perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid (EtFOSAA), 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (MeFOSAA), perfluorononanoic acid (PFNA) adjusting for covariates. Participants (N = 941, 65% female, 58% Caucasian, 68% married, 75% with higher education, 95% nonsmoker) had similar PFAS concentrations compared to the general U.S. population during 1999-2000. Using a single food group approach, fried fish, other fish/shellfish, meat and poultry had positive associations with most PFAS plasma concentrations. The strongest effect estimate detected was between fried fish and PFNA [13.6% (95% CI: 7.7, 19.9) increase in median concentration per SD increase]. Low-carbohydrate and high protein diet score had positive association with plasma PFHxS. Some food groups, mostly vegetables and fruits, and the Dietary Approaches to Stop Hypertension diet score had inverse associations with PFOS and MeFOSAA. A vegetable diet pattern was associated with lower plasma concentrations of MeFOSAA, while high-fat meat and low-fiber and high-fat grains diet patterns were associated with higher plasma concentrations of PFOS, PFHxS, MeFOSAA and PFNA. We summarized four major dietary characteristics associated with variations in PFAS plasma concentrations in this population. Specifically, consuming more meat/fish/shellfish (especially fried fish, and excluding Omega3-rich fish), low-fiber and high-fat bread/cereal/rice/pasta, and coffee/tea was associated with higher plasma concentrations while dietary patterns of vegetables, fruits and Omega-3 rich fish were associated with lower plasma concentrations of some PFAS.

Multiple pathways of human exposure to poly- and perfluoroalkyl substances (PFASs): From external exposure to human blood

Exposure to PFASs may result in adverse health effects. This study aimed to characterise the exposure to PFASs from diet, house dust, indoor air, and dermal contact and the relative contribution from different external exposure pathways to human serum concentrations. Daily intakes of 18 perfluoroalkyl acids (PFAAs) and 12 PFAA precursors from diet, dust ingestion, inhalation of indoor air and dermal absorption were estimated using a comprehensive dataset comprising 61 adults from the Oslo area, Norway. Concentrations of PFAAs and PFAA precursors in house dust, indoor air, hand wipes, foods and drinks were utilised to estimate the daily intakes. Perfluorooctanesulfonate (PFOS) was the predominant PFAS in serum for this study group. On a median level, perfluorooctanoate (PFOA) contributed most to the total estimated daily intake of PFAAs, with a median intake of 280 (range: 72-1810) pg·kg bw^-1·day^-1, covering both direct and indirect (precursors) exposure. Out of this, only 3% (range: <1-48%) of the total PFOA intake came from indirect exposure. Dietary exposure from ingestion of food and drinks was in general the predominant exposure pathway, followed by exposure from ingestion of house dust, inhalation of indoor air, and dermal absorption, but considerable variations were observed among individuals. House dust ingestion and indoor air inhalation contributed most to the total intakes for some participants, for which most of them were among the 20% participants with the highest total estimated intakes. Some statistical significant associations between concentrations of PFASs measured in serum and estimated intakes were observed. Measured serum concentrations and modelled serum concentrations based on external exposure estimates were in the same order of magnitude for PFOS, PFHxS, PFOA, and PFNA, but only PFOA concentrations were comparable, 1.9 and 2.0 ng mL^-1 for observed and modelled serum concentrations, respectively. The estimated daily intakes of PFASs in this study were lower than the health-based guidance values, e.g. the tolerable weekly intakes derived by EFSA. This study underlines the importance of performing studies considering multiple exposure pathways on an individual basis.

Perfluoroalkyl acids and thyroid hormones across stages of kidney function

Data for US adults aged ≥20 years for 2007-2012 (N = 7020) were used to study concentrations of thyroid stimulating hormone (TSH), free (FT3) and total triiodothyronine (TT3), free (FT4) total thyroxine (TT4), and thyroglobulin (TGN) across stages of glomerular function (GF). Data for 2007-2008 and 2011-2012 (N = 2549) were used to study associations between thyroid hormone biomarkers and five serum perfluoroalkyl acids (PFAAs). We report how thyroid hormone biomarkers vary in human serum across stages of GF. Stages considered were: GF-1 (normal, eGFR >90 mL/min/1.73 m²), GF-2 (60 ≤ eGFR≤90 mL/min/1.73 m²), GF-3A (45 ≤eGFR<60 mL/min/1.73 m²), and GF-3B/4 (15 ≤ eGFR<45 mL/min/1.73 m²). Regression models stratified by GF stages were fitted to evaluate associations between the concentrations of selected PFAAs and thyroid hormones and to evaluate the variability in concentrations of thyroid hormones across the stages of GF. Adjusted geometric means (AGM) for TSH sharply increased from GF-1 (1.34 μIU/mL) to GF-2 (1.58 μIU/mL) and then remained relatively stable. AGMs of FT3 and TT3 decreased consistently from GF-1 to GF-3B/4; from 3.24 to 2.79 pg/mL for FT3 and from 115.7 to 96.4 ng/dL for TT3. AGMs for FT4 increased from GF-2 onward. TGN increased as glomerular filtration worsened from GF-1 through GF-3B/4. In contrast to strong relationships of thyroid hormone markers to stages of renal function, only scattered, inconsistent findings characterized relationship of PFAAs to thyroid markers across stages of kidney disease. For example, TSH was positively associated with PFOA at GF-2 (β = 0.08522, p < 0.01) but negatively associated at GF-3A (β = - 0.22926, p = 0.04). Thus, associations between kidney disease and thyroid hormone are clear, but the relationships between PFAAs and thyroid hormones vary inconsistently from stage to stage and reveal no trend. For thyroid hormone investigations, we conclude stratification by glomerular function stage is likely not needed.

Children's exposure to perfluoroalkyl acids - a modelling approach

Adults are mainly exposed to per- and polyfluoroalkyl substances (PFASs) via ingestion of food, inhalation of air and ingestion of dust, whereas for children the exposure to PFASs is largely unknown. This study aimed to reconstruct the serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) in children after infancy up to 10.5 years of age and to test if dietary intake is the major exposure pathway for children to PFOA, PFOS and PFHxS after infancy. For this work, a dataset from a Finnish child cohort study was available, which comprised serum concentrations of the studied perfluoroalkyl acids (PFAAs) and PFAS concentration measurements in dust and air samples from the children's bedrooms. The calculated PFAA intakes were used in a pharmacokinetic model to reconstruct the PFAA serum concentrations from 1 to 10.5 years of age. The calculated PFOA and PFOS intakes were close to current regulatory intake thresholds and diet was the major exposure medium for the 10.5 year-olds. The one-compartment PK model reconstructed median PFOA and PFOS serum concentrations well compared to corresponding measured median serum concentrations, while the modelled PFHxS serum concentrations showed a constant underestimation. The results imply that children's exposure to PFOA and PFOS after breastfeeding and with increasing age resembles the exposure of adults. Further, the children in the Finnish cohort experienced a rather constant exposure to PFOA and PFOS between 1 and 10.5 years of age. The PFHxS exposure sources and respective pharmacokinetic parameter estimations need further investigation.

Prenatal Exposure to Per- and Polyfluoroalkyl Substances (PFASs) and Association between the Placental Transfer Efficiencies and Dissociation Constant of Serum Proteins-PFAS Complexes

Information on placental transfer and adverse outcomes of short-chain per- and polyfluoroalkyl substance (PFASs) is limited, and factors responsible for PFAS placental transfer are still unclear. In the present study, concentrations of 21 PFASs were analyzed in 132 paired maternal and cord serum samples collected from residents in Beijing, China, and the placental transfer efficiency (PTE) of each PFAS was calculated. PTEs of short-chain perfluoroalkyl acids (PFAAs), including PFBA (146%), PFBS (97%), PFPeA (118%), and PFHxA (110%), were first reported, and a complete U-shaped trend of PTEs from C4 to C13 of perfluoroalkyl carboxylic acids (PFCAs) was obtained. Positive association between maternal weight and PTE of perfluorooctanesulfonate (PFOS) ( p < 0.05) and negative association between maternal PFBA concentration and birth length ( p < 0.01) were observed. Using in vitro experiments, we further determined equilibrium dissociation constants ( K_ds) of human serum albumin (HSA)-PFAS complexes ( K_d-HP), serum proteins-PFAS complexes ( K_d-SP), and liver-fatty acid binding protein (L-FABP)-PFAS complexes ( K_d-LP) and found that they were all significantly correlated with PTEs of PFASs. The correlation coefficient was 0.92, 0.89, and 0.86, respectively ( p < 0.01 in all three tests), suggesting that K_ds of protein (serum)-PFAS complexes can play an important role in trans-placental transfer of PFASs in human and K_d-HP plays a pivotal role.

Tap Water Contributions to Plasma Concentrations of Poly- and Perfluoroalkyl Substances (PFAS) in a Nationwide Prospective Cohort of U.S. Women

BACKGROUND

Between 2013 and 2015, concentrations of poly- and perfluoroalkyl substances (PFAS) in public drinking water supplies serving at least six million individuals exceeded the level set forth in the health advisory established by the U.S. Environmental Protection Agency. Other than data reported for contaminated sites, no systematic or prospective data exist on the relative source contribution (RSC) of drinking water to human PFAS exposures.

OBJECTIVES

This study estimates the RSC of tap water to overall PFAS exposure among members of the general U.S.

POPULATION

METHODS

We measured concentrations of 15 PFAS in home tap water samples collected in 1989-1990 from 225 participants in a nationwide prospective cohort of U.S. women: the Nurses' Health Study (NHS). We used a one-compartment toxicokinetic model to estimate plasma concentrations corresponding to tap water intake of PFAS. We compared modeled results with measured plasma PFAS concentrations among a subset of 110 NHS participants.

RESULTS

Tap water perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) were statistically significant predictors of plasma concentrations among individuals who consumed [Formula: see text] cups of tap water per day. Modeled median contributions of tap water to measured plasma concentrations were: PFOA 12% (95% probability interval 11%-14%), PFNA 13% (8.7%-21%), linear perfluorooctanesulfonic acid (nPFOS) 2.2% (2.0%-2.5%), branched perfluorooctanesulfonic acid (brPFOS) 3.0% (2.5%-3.2%), and perfluorohexanesulfonic acid (PFHxS) 34% (29%-39%). In five locations, comparisons of PFASs in community tap water collected in the period 2013-2016 with samples from 1989-1990 indicated increases in quantifiable PFAS and extractable organic fluorine (a proxy for unquantified PFAS).

CONCLUSIONS

Our results for 1989-1990 compare well with the default RSC of 20% used in risk assessments for legacy PFAS by many agencies. Future evaluation of drinking water exposures should incorporate emerging PFAS. https://doi.org/10.1289/EHP4093.

Perfluorooctanoic acid exposure induces apoptosis in SMMC-7721 hepatocellular cancer cells

To better understand the toxicological activities of perfluorooctanoic acid (PFOA), we examined the effects of PFOA on apoptosis and its molecular mechanism in SMMC-7721 hepatoma cells. Cell viability was evaluated by MTT assay and apoptosis was determined by flow cytometry. Western blot and quantitative real-time PCR were used to examine the protein and gene expressions of Bax and Bcl-2. Our results showed that PFOA inhibited SMMC-7721 cell growth and induced apoptosis. PFOA treatment increased Bax expression and increased Bcl-2 expression at both gene and protein levels. Our study demonstrated that PFOA had toxic effects on SMMC-7721 cells, such as inhibiting cell proliferation and inducing apoptosis. Furthermore, we showed that PFOA-mediated induction of apoptosis involved inducing Bax and decreasing Bcl-2 expression as a molecular mechanism of its toxicological effects.

Dynamics of associations between perfluoroalkyl substances and uric acid across the various stages of glomerular function

National Health and Nutrition Examination Survey 2007-2014 data (N = 6844) for adults aged ≥ 20 years were analyzed to estimate associations of perfluoroalkyl substances (PFAS), namely, PFOA, PFOS, PFDA, PFHxS, and PFNA with uric acid across stages of declining glomerular function. The population was stratified by the estimated glomerular filtration rates (eGFR) stages accompanying kidney disease: GF-1 with eGFR > 90 mL/min/1.73 m²; GF-2 with eGFR 60-89 mL/min/1.73 m²; GF-3A with eGFR 45-59 mL/min/1.73 m²; and GF-3B/4 with eGFR 15-44 mL/min/1.73 m². Adjusted and unadjusted geometric means of uric acid increased from GF-1 to GF-3B/4 for males and females. Adjusted geometric means for uric acid were higher for males by 1.38, 1.03, and 0.62 mg/dL for GF-1, GF2, and GF-3 respectively but for GF-3B/4, females had higher adjusted geometric means than males by 0.16 mg/dL, revealing narrowing of sex differences in uric acid as glomerular function declines. The direction of association between PFAS and uric acid was positive for GF-1 and GF-2 for males and for every PFAS except PFDA for females. For males for GF-3B/4, association between every PFAS except PFHxS and uric acid was found to be negative (p < 0.01). For females, only PFHxS actually reverses its relationship with increasing stages of renal disease. Uric acid associations with PFAS reverse in males with advanced renal failure. An implication is that previously reported association of PFAS exposure with uric acid is not due to renal failure. Understanding of other biomarkers associated with both PFAS exposure and renal failure may benefit from similar evaluation.

A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects

Here, we review present understanding of sources and trends in human exposure to poly- and perfluoroalkyl substances (PFASs) and epidemiologic evidence for impacts on cancer, immune function, metabolic outcomes, and neurodevelopment. More than 4000 PFASs have been manufactured by humans and hundreds have been detected in environmental samples. Direct exposures due to use in products can be quickly phased out by shifts in chemical production but exposures driven by PFAS accumulation in the ocean and marine food chains and contamination of groundwater persist over long timescales. Serum concentrations of legacy PFASs in humans are declining globally but total exposures to newer PFASs and precursor compounds have not been well characterized. Human exposures to legacy PFASs from seafood and drinking water are stable or increasing in many regions, suggesting observed declines reflect phase-outs in legacy PFAS use in consumer products. Many regions globally are continuing to discover PFAS contaminated sites from aqueous film forming foam (AFFF) use, particularly next to airports and military bases. Exposures from food packaging and indoor environments are uncertain due to a rapidly changing chemical landscape where legacy PFASs have been replaced by diverse precursors and custom molecules that are difficult to detect. Multiple studies find significant associations between PFAS exposure and adverse immune outcomes in children. Dyslipidemia is the strongest metabolic outcome associated with PFAS exposure. Evidence for cancer is limited to manufacturing locations with extremely high exposures and insufficient data are available to characterize impacts of PFAS exposures on neurodevelopment. Preliminary evidence suggests significant health effects associated with exposures to emerging PFASs. Lessons learned from legacy PFASs indicate that limited data should not be used as a justification to delay risk mitigation actions for replacement PFASs.

Characterization of age-based trends to identify chemical biomarkers of higher levels in children

BACKGROUND

Chemical biomarker concentrations are driven by complex interactions between chemical use patterns, exposure pathways, and toxicokinetic parameters such as biological half-lives. Criteria to differentiate legacy from current exposures are helpful for interpreting variation in age-based and time trends of chemical exposure and identifying chemicals to which children are highly exposed. A systematic approach is needed to study temporal trends for a wide range of chemicals in the US population.

OBJECTIVES

Using National Health and Nutrition Examination Survey (NHANES) data on measured biomarker concentrations for 141 chemicals from 1999 to 2014, we aim to 1) understand the influence of temporal determinants, in particular time trends, biological half-lives, and restriction dates on age-based trends, 2) systematically define an age-based pattern to identify chemicals with ongoing and high exposure in children, and 3) characterize how age-based trends for six Per- and Polyfluoroalkyl Substances (PFASs) are changing over time.

METHODS

We performed an integrated analysis of biological half-lives and restriction dates, compared distributions of chemical biomarker concentrations by age group, and then applied a series of regression models to evaluate the linear (β_age) and nonlinear (β_age²) relationships between age and chemical biomarker levels.

RESULTS

For restricted chemicals, a minimum persistence of 1 year in the human body is needed to observe substantial differences between the less exposed young population and historically exposed adults. We define a metric ( [Formula: see text] ) that identifies several phthalates, brominated flame retardants, pesticides, and metals such as lead and tungsten as elevated and ongoing exposures in children. While a substantial reduction in children's exposures was reflected in PFOS and PFOA, levels of PFNA and PFHxS in children were higher in 2013-2014 compared to those in 1999-2000.

CONCLUSIONS

Integrating a series of regression models with systemized stratified analyses by age group enabled us to define an age-based pattern to identify chemicals that are of higher levels in children.

Perfluoroalkyl acids in serum of Korean children: Occurrences, related sources, and associated health outcomes

Perfluoroalkyl acids (PFAAs) have been widely used in human environment, and their exposure among general population has been frequently reported. However, extent of PFAAs exposure and their potential effects among children are not well characterized. In this study, children of between 3 and 18 years of age (n = 150) were recruited in Seoul and Gyeonggi, Korea, and the serum levels of 16 PFAAs along with lipids and thyroid hormones were measured. Questionnaire survey was conducted for dietary and behavioral characteristics of the children. Among the measured PFAAs, PFOA, PFNA, PFHxS, and PFOS were detected in all the samples, and PFUnDA and PFDA were detected in over 75% of the samples. PFOS was detected at the highest concentration with a median of 5.68 ng/mL. PFUnDA was detected at higher levels (median of 0.652 ng/mL) compared to those reported for children in USA. Serum PFAA levels were not different by sex among the children of <10 years of age, but in older children, those of boys are significantly higher than girls. Physiological characteristics like menstruation may explain lower PFAAs levels of the girls. In addition, breastmilk consumption, fish/shellfish consumption, non-stick frying pan use, and waterproof cloth use were identified as potential sources of PFAAs exposure. Serum PFUnDA level was positively associated with total cholesterol and low-density lipoprotein level of the children. PFNA was positively associated with free T4 level. High levels of PFUnDA among children and its association with serum lipids warrant replication and confirmation in other populations and/or supports by experimental studies.

Time trends over 2003-2014 in the concentrations of selected perfluoroalkyl substances among US adults aged ≥20 years: Interpretational issues

Data (N = 9650) for US adults aged ≥20 years downloaded from National Health and Nutrition Examination Survey for 2003-2014 were analyzed to study trends in adjusted and unadjusted concentrations of selected perfluoroalkyl substances (PFAS), namely, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). Over 2003-2014, unadjusted concentrations of PFOA decreased by 50%, by 75% for PFOS, by 32% for PFDA, by 27% for PFHxS, and by 30% for PFNA. Females not only had substantially lower concentrations of every PFAS than males but rate of decrease was also higher for females than males, for example, 36.7% for females and 30.6% for males every two years for PFOS. For each survey period of two years, percent decrease in adjusted concentrations was 17% for PFOA, 33.5% for PFOS, 11.5% for PFDA, 6.3% for PFHxS, and 7.6% for PFNA. However, these trend data must be examined within the context of design changes in NHANES over 2003-2014 resulting in oversampling of Hispanics other than Mexican Americans starting 2007-2008 survey cycle and oversampling of non-Hispanic Asians starting 2011-2012 survey cycle. In order to examine how design changes may have affected computations of adjusted and unadjusted concentrations, the data were analyzed using the racial/ethnic categories prior to and after oversampling of Hispanics other than Mexican Americans and non-Hispanic Asians was put into place.

Longitudinal trends of per- and polyfluoroalkyl substances in children's serum

Studies suggest negative health impacts from early life exposure to per- and polyfluoroalkyl substances (PFASs). However, information on longitudinal exposure to PFASs during childhood is scarce for background-exposed individuals. This study sought to fill this gap by investigating children's longitudinal exposure trends through measurement of PFAS serum concentrations and calculation of body burdens (μg, total in body). Blood of 54 Finnish children was sampled 2005-2015 and analyzed for 20 PFASs at 1, 6 and 10.5 years of age. The body burden was calculated by multiplying the serum concentration by the volume of distribution and the bodyweight for each individual. Associations between serum concentrations or body burdens and parameters, such as sex, breastfeeding duration, body mass index as well as indoor dust and air PFAS concentrations, were evaluated. Serum concentrations of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorohexane sulfonic acid (PFHxS) decreased significantly (p < 0.001) with age. In contrast to serum concentrations, body burdens stayed unchanged or even increased significantly (p < 0.05), except for PFOA in female children. Breastfeeding duration was positively correlated (p < 0.001) with serum concentrations of PFHxS, PFOS, PFOA and PFNA at 1 year of age. Some associations were found at 10.5 years with sex and indoor PFAS concentrations. Observations of longitudinal decreasing trends of serum concentrations can be misleading for understanding exposure levels from external media during childhood, as the serum concentration is influenced by parallel temporal changes and growth dilution. Body burdens account for growth dilution and thus better reflect differences in early-life to adolescence exposure than serum concentrations.

Associations between longitudinal serum perfluoroalkyl substance (PFAS) levels and measures of thyroid hormone, kidney function, and body mass index in the Fernald Community Cohort

Perfluoroalkyl substances (PFAS) are a diverse class of manufactured compounds used in a wide range of industrial processes and consumer products and have been detected in human serum worldwide. Previous cross-sectional and cohort studies in humans have suggested exposure to PFAS is associated with a wide array of chronic diseases, including endocrine disruption, developmental health effects, cancer and metabolic changes. We examined the associations between a panel of eight PFAS and indicators of thyroid disruption, kidney function, and body mass index (BMI), all of which were measured at repeated time points (1990-2008) over the course of the study. Participants (N = 210) were selected from the Fernald Community Cohort based on household water supply from a PFAS-contaminated aquifer. In adjusted repeated measures models, we observed several notable associations between serum PFAS and thyroid hormones as well as kidney function as measured by estimated glomerular filtration rate (eGFR). An interquartile (IQR) increase in serum PFOS was associated with a 9.75% (95% CI = 1.72, 18.4) increase in thyroid stimulating hormone. An IQR increase in serum PFNA, PFHxS, and PFDeA was associated with a -1.61% (95% CI = -3.53, -0.59), -2.06% (95% CI = -3.53, -0.59), and -2.20% (95% CI = -4.25, -0.14) change in eGFR, respectively. On the other hand, an IQR increase in serum Me-PFOSA was associated with a 1.53% (95% CI = 0.34, 2.73) increase in eGFR. No significant associations with BMI and serum PFAS were noted. Our findings are in agreement with previous reports that serum PFAS are associated with altered kidney and thyroid function.

Polybrominated diphenyl ethers and perfluorinated alkyl substances in blood serum of New Zealand adults, 2011-2013

A national survey was conducted in 2011-2013 to assess serum concentrations of brominated flame retardants (BFRs) and perfluorinated alkyl substances (PFASs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 geographic regions, 2 ethnic groups (Māori/non-Māori) and sex. Eligible participants (n = 734; response rate of contacted individuals = 37%) donated up to 30 mL of blood, after which serum was pooled (49 pools for BFRs, 63 pools for PFASs) according to demographic strata. BFRs were analysed by GC-HRMS and PFASs by LC-MS/MS. Associations between serum BFRs and PFASs and demographic variables (age, region, ethnicity, sex) were assessed using regression analysis. The weighted geometric mean (GM) serum concentrations of BDE47, BDE99, BDE100, and BDE153 were 2.0, 0.66, 0.43, and 1.2 ng/g lipid, respectively. The weighted geometric mean (GM) serum concentrations of PFOS, PFOA, PFHxS, and PFNA were 3.4, 2.4, 1.0, and 0.66 ng/mL, respectively. The majority of BFRs showed higher serum concentrations in younger age groups. Conversely, the four PFASs showed higher serum concentrations in older age groups. Concentrations of BFRs and PFASs were generally lower in females compared to males. In New Zealand, both age and sex are important determinants of BFR and PFAS serum concentrations.