Association between perfluoroalkyl substances exposure and thyroid function in adults: A meta-analysis

Per- and polyfluoroalkyl substances (PFAS), thyroid hormones, sexual hormones and pubertal development in adolescents residing in the neighborhood of a 3M factory

BACKGROUND

Near Antwerp a 3M factory has been active since 1971 emitting PFAS, mainly PFOS, in the local environment. Production of C8 compounds was stopped in 2002, production of other PFAS continued until 2024. This study aimed to examine the association between internal PFAS concentrations and thyroid hormones, sexual hormones, and pubertal development in adolescents living in the neighborhood of the factory.

METHODS

We measured PFAS in serum of 146 female and 139 male adolescents. For males sex hormones (LH, testosterone, estradiol, progesterone, inhibin B, FSH) and SHBG were measured in serum. For males and females we assessed serum thyroid hormone levels (TSH, T3, T4 and T3/T4) and pubertal development parameters self-assessed through a standardized questionnaire. Associations between PFAS concentrations and effect biomarkers/health effects were assessed through Generalized Estimating Equations (GEE), using linear models for continuous outcomes, logistic models for binary outcomes, and proportional odds models for ordinal outcomes.

RESULTS

For males LH, total and bioavailable testosterone showed significant negative associations with PFHxS and PFOA. LH and bioavailable testosterone also showed significant negative associations with other PFAS compounds. SHBG showed significant positive associations with PFDA, PFNA, PFHxS, PFOS and the sum of the linear forms of PFOS, PFOA, PFNA and PFHxS. Males' length and growth spurt showed significant negative associations with PFOS, PFOA and PFAS sum parameters and length and growth spurt separately also with other PFAS compounds. For females growth spurt showed significant negative association with PFOA and a significant positive association with PFOS(branched). For both males and females body hair development showed significant negative associations with PFHxS, and, for males and females separately also with other PFAS compounds. For females, breast development showed significant negative associations with PFOA, pubertal development scale showed significant negative associations with PFOA, PFHxS, PFOS(linear) and the sum of 4 PFAS. For males, TSH showed a significant negative association with PFDA and FT3 showed significant positive associations with PFOA, PFOA and PFNA. For females, FT3 showed a significant negative association with PFOS(branched).

CONCLUSION

We observed significant, consistent and biologically relevant associations of PFAS serum concentrations with sex hormone and SHBG levels in male adolescents. Moreover, a significant delay in physiological processes occurring in puberty was observed in females and males. Associations with thyroid hormones differed significantly by sex.

A combinational threat of micro- and nano-plastics (MNPs) as potential emerging vectors for per- and polyfluoroalkyl substances (PFAS) to human health

Micro- and nano-plastics (MNPs) and per- and polyfluoroalkyl substances (PFAS) are prevalent in ecosystems due to their exceptional properties and widespread use, profoundly affecting both human health and ecosystem. Upon entering the environment, MNPs and PFAS undergo various transformations, such as weathering, transport, and accumulation, potentially altering their characteristics and structural dynamics. Their interactions, governed by factors like hydrogen bonding, hydrophobic interactions, Van der Waals forces, electrostatic attractions, and environmental conditions, can amplify or mitigate their toxicity toward human health within ecological conditions. Several studies demonstrate the in vivo effects of PFAS and MNPs, encompassing growth and reproductive impairments, oxidative stress, neurotoxicity, apoptosis, DNA damage, genotoxicity, immunological responses, behavioral changes, modifications in gut microbiota, and histopathological alterations. Moreover, in vitro investigations highlight impacts on cellular uptake, affecting survival, proliferation, membrane integrity, reactive oxygen species (ROS) generation, and antioxidant responses. This review combines knowledge on the co-existence and adsorption of PFAS and MNPs in the environment, defining their combined in vivo and in vitro impacts. It provides evidence of potential human health implications. While significant research originates from China, Europe, and the USA, studies from other regions are limited. Only freshwater and marine organisms and their impacts are extensively studied in comparison to terrestrial organisms and humans. Nonetheless, detailed investigations are lacking regarding their fate, combined environmental exposure, mode of action, and implications in human health studies. Ongoing research is imperative to comprehensively understand environmental exposures and interaction mechanisms, addressing the need to elucidate these aspects thoroughly.

Screening the ToxCast Chemical Libraries for Binding to Transthyretin

Transthyretin (TTR) is one of the serum binding proteins responsible for transport of thyroid hormones (TH) to target tissue and for maintaining the balance of available TH. Chemical binding to TTR and subsequent displacement of TH has been identified as an end point in screening chemicals for potential disruption of the thyroid system. To address the lack of data regarding chemicals binding to TTR, we optimized an in vitro assay utilizing the fluorescent probe 8-anilino-1-napthalenesulfonic acid (ANSA) and the human protein TTR to screen over 1500 chemicals from the U.S. EPA's ToxCast ph1_v2, ph2, and e1k libraries utilizing a tiered approach. Testing of a single high concentration (target 100 μM) resulted in 888 chemicals with 20% or greater activity based on displacement of ANSA from TTR. Of these, 282 chemicals had activity of 85% or greater and were further tested in 12-point concentration-response with target concentrations ranging from 0.015 to 100 μM. An EC50 was obtained for 276 of these 301 chemicals. To date, this is the largest set of chemicals screened for binding to TTR. Utilization of this assay is a significant contribution toward expanding the suite of in vitro assays used to identify chemicals with the potential to disrupt thyroid hormone homeostasis.

Association of per- and polyfluoroalkylated substances/heavy metals and bone health in children and adolescents

Background

Research on the correlation between exposure to per- and polyfluoroalkylated substances (PFASs)/heavy metals and bone health during childhood and adolescence is limited. Considering their role as endocrine disruptors, we examined relationships of six PFASs and three heavy metals with bone mineral density (BMD) in children and adolescents using representative samples from the National Health and Nutrition Examination Survey (NHANES).

Methods

The study included 622 participants aged 12-19. The relationship between single pollutant and lumbar spine and total BMD was studied using linear regression analyses. Additionally, Bayesian Kernel Machine Regression (BKMR) models were applied to assess the joint effects of multiple PFASs and heavy metals exposure on the lumbar spine and total BMD.

Results

Statistically significant differences were noted in the serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), blood lead (Pb), and blood manganese (Mn) between male and female participants (all p < 0.05). Single-exposure studies have shown that Mn was negatively correlated with lumbar spine BMD and total BMD. Multivariate linear regression models revealed that, in the male group, total bone density decreased as the blood PFOA levels [95% CI = (-0.031, -0.001), p = 0.040] and blood manganese levels [95% CI = (-0.009, -0.002), p = 0.004] increased. Similarly, lumbar spine bone density decreased as the blood manganese levels [95% CI = (-0.011, -0.002), p = 0.009] increased. In the female group, total bone density decreased as the serum PFNA levels [95% CI = (-0.039, 0.000), p = 0.048] increased. As shown in the BKMR model, the joint effects of pollutant mixtures, including Mn, were negatively associated with both the lumbar spine and total BMD. Among the pollutants analyzed, Mn appeared to be the primary contributor to this negative association.

Conclusion

This study suggests that exposure to certain PFASs and heavy metals may be associated with poor bone health. Childhood and adolescence are crucial stages for bone development, and improper exposure to PFASs and heavy metals during these stages could potentially jeopardize future bone health, consequently raising the risk of osteoporosis in adulthood.

An Umbrella Review of Meta-Analyses Evaluating Associations between Human Health and Exposure to Major Classes of Plastic-Associated Chemicals

Background: Epidemiological research investigating the impact of exposure to plastics, and plastic-associated chemicals, on human health is critical, especially given exponentially increasing plastic production. In parallel with increasing production, academic research has also increased exponentially both in terms of the primary literature and ensuing systematic reviews with meta-analysis. However, there are few overviews that capture a broad range of chemical classes to present a state of play regarding impacts on human health. Methods: We undertook an umbrella review to review the systematic reviews with meta-analyses. Given the complex composition of plastic and the large number of identified plastic-associated chemicals, it was not possible to capture all chemicals that may be present in, and migrate from, plastic materials. We therefore focussed on a defined set of key exposures related to plastics. These were microplastics, due to their ubiquity and potential for human exposure, and the polymers that form the matrix of consumer plastics. We also included plasticisers and flame retardants as the two classes of functional additive with the highest concentration ranges in plastic. In addition, we included bisphenols and per- and polyfluoroalkyl substances (PFAS) as two other major plastic-associated chemicals with significant known exposure through food contact materials. Epistemonikos and PubMed were searched for systematic reviews with meta-analyses, meta-analyses, and pooled analyses evaluating the association of plastic polymers, particles (microplastics) or any of the selected groups of high-volume plastic-associated chemicals above, measured directly in human biospecimens, with human health outcomes. Results: Fifty-two systematic reviews were included, with data contributing 759 meta-analyses. Most meta-analyses (78%) were from reviews of moderate methodological quality. Across all the publications retrieved, only a limited number of plastic-associated chemicals within each of the groups searched had been evaluated in relevant meta-analyses, and there were no meta-analyses evaluating polymers, nor microplastics. Synthesised estimates of the effects of plastic-associated chemical exposure were identified for the following health outcome categories in humans: birth, child and adult reproductive, endocrine, child neurodevelopment, nutritional, circulatory, respiratory, skin-related and cancers. Bisphenol A (BPA) is associated with decreased anoclitoral distance in infants, type 2 diabetes (T2D) in adults, insulin resistance in children and adults, polycystic ovary syndrome, obesity and hypertension in children and adults and cardiovascular disease (CVD); other bisphenols have not been evaluated. Phthalates, the only plasticisers identified, are associated with spontaneous pregnancy loss, decreased anogenital distance in boys, insulin resistance in children and adults, with additional associations between certain phthalates and decreased birth weight, T2D in adults, precocious puberty in girls, reduced sperm quality, endometriosis, adverse cognitive development and intelligence quotient (IQ) loss, adverse fine motor and psychomotor development and elevated blood pressure in children and asthma in children and adults. Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) but not other flame retardants, and some PFAS were identified and are all associated with decreased birth weight. In general populations, PCBs are associated with T2D in adults and endometriosis, bronchitis in infants, CVD, non-Hodgkin's lymphoma (NHL) and breast cancer. In PCB-poisoned populations, exposure is associated with overall mortality, mortality from hepatic disease (men), CVD (men and women) and several cancers. PBDEs are adversely associated with children's cognitive development and IQ loss. PBDEs and certain PFAS are associated with changes in thyroid function. PFAS exposure is associated with increased body mass index (BMI) and overweight in children, attention deficit hyperactive disorder (ADHD) in girls and allergic rhinitis. Potential protective associations were found, namely abnormal pubertal timing in boys being less common with higher phthalate exposure, increased high-density lipoprotein (HDL) with exposure to mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) and reduced incidence of chronic lymphocytic lymphoma (a subtype of NHL) with PCB exposure. Conclusions: Exposure to plastic-associated chemicals is associated with adverse outcomes across a wide range of human health domains, and every plastic-associated chemical group is associated with at least one adverse health outcome. Large gaps remain for many plastic-associated chemicals. Recommendations: For research, we recommend that efforts are harmonised globally to pool resources and extend beyond the chemicals included in this umbrella review. Priorities for primary research, with ensuing systematic reviews, could include micro- and nanoplastics as well as emerging plastic-associated chemicals of concern such as bisphenol analogues and replacement plasticisers and flame retardants. With respect to chemical regulation, we propose that safety for plastic-associated chemicals in humans cannot be assumed at market entry. We therefore recommend that improved independent, systematic hazard testing for all plastic-associated chemicals is undertaken before market release of products. In addition because of the limitations of laboratory-based testing for predicting harm from plastic in humans, independent and systematic post-market bio-monitoring and epidemiological studies are essential to detect potential unforeseen harms.

Effects of Endocrine-Disrupting Chemicals on Bone Health

This comprehensive review critically examines the detrimental impacts of endocrine-disrupting chemicals (EDCs) on bone health, with a specific focus on substances such as bisphenol A (BPA), per- and polyfluoroalkyl substances (PFASs), phthalates, and dioxins. These EDCs, by interfering with the endocrine system's normal functioning, pose a significant risk to bone metabolism, potentially leading to a heightened susceptibility to bone-related disorders and diseases. Notably, BPA has been shown to inhibit the differentiation of osteoblasts and promote the apoptosis of osteoblasts, which results in altered bone turnover status. PFASs, known for their environmental persistence and ability to bioaccumulate in the human body, have been linked to an increased osteoporosis risk. Similarly, phthalates, which are widely used in the production of plastics, have been associated with adverse bone health outcomes, showing an inverse relationship between phthalate exposure and bone mineral density. Dioxins present a more complex picture, with research findings suggesting both potential benefits and adverse effects on bone structure and density, depending on factors such as the timing and level of exposure. This review underscores the urgent need for further research to better understand the specific pathways through which EDCs affect bone health and to develop targeted strategies for mitigating their potentially harmful impacts.

Per- and polyfluoroalkyl substances (PFAS) exposure and thyroid cancer: Systematic review and meta-analysis

Per- and polyfluoroalkyl substances (PFAS) exposure is a potential risk factor for thyroid cancer and may be a contributor to the increasing thyroid cancer incidence rates. A systematic review and meta-analysis was performed to summarize all human studies to date investigating the association between PFAS exposure and thyroid cancer. A search of the National Library of Medicine and National Institutes of Health PubMed and Scopus databases was done to identify relevant articles published in English through January 2024. Studies reporting the association between PFAS exposure and thyroid cancer using odds ratios (OR) were included in the meta-analysis with summary estimate calculated using a random effects model (n=5). Perfluorooctanoic acid (PFOA) was the most investigated PFAS. Results of the included studies varied, ranging from significant positive to significant negative associations with thyroid cancer incidence for different PFAS. Meta-analyses of PFOA, Perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS) were not significant. This comprehensive review of the current literature highlights the limited knowledge and inconsistent results of this association. Large longitudinal cohort studies with varying time between sample collection and thyroid cancer diagnosis are needed to better understand the role of PFAS exposure on thyroid carcinogenesis.

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Polymers are the main building blocks of plastic, with the annual global production volume of fossil carbon-based polymers reaching over 457 million metric tons in 2019 and this figure is anticipated to triple by 2060. There is potential for environmental harm and adverse human health impacts associated with plastic, its constituent polymers and the chemicals therein, at all stages of the plastic life cycle, from extraction of raw materials, production and manufacturing, consumption, through to ultimate disposal and waste management. While there have been considerable research and policy efforts in identifying and mitigating the impacts associated with problematic plastic products such as single-use plastics and hazardous chemicals in plastics, with national and/or international regulations to phase out their use, plastic polymers are often overlooked. In this review, the polymer dimension of the current knowledge on environmental release, human exposure and health impacts of plastic is discussed across the plastic life cycle, including chemicals used in production and additives commonly used to achieve the properties needed for applications for which the polymers are generally used. This review focuses on polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene, four common plastic polymers made from the hazardous monomers, bisphenol, styrene, vinyl chloride and 1,3-butadiene, respectively. Potential alternative polymers, chemicals, and products are considered. Our findings emphasise the need for a whole system approach to be undertaken for effective regulation of plastics whereby the impacts of plastics are assessed with respect to their constituent polymers, chemicals, and applications and across their entire life cycle.

Changes in plasma concentrations of per- and Polyfluoroalkyl substances after bariatric surgery in adolescents from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study

Exposure to per- and poly-fluoroalkyl substances (PFAS) is ubiquitous due to their persistence in the environment and in humans. Extreme weight loss has been shown to influence concentrations of circulating persistent organic pollutants (POPs). Using data from the multi-center perspective Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) cohort, we investigated changes in plasma-PFAS in adolescents after bariatric surgery. Adolescents (Mean age = 17.1 years, SD = 1.5 years) undergoing bariatric surgery were enrolled in the Teen-LABS study. Plasma-PFAS were measured at the time of surgery and then 6-, 12-, and 36 months post-surgery. Linear mixed effect models were used to evaluate longitudinal changes in plasma-PFAS after the time of bariatric surgery. This study included 214 adolescents with severe obesity who had available longitudinal measures of plasma-PFAS and underwent bariatric surgery between 2007 and 2012. Underlying effects related to undergoing bariatric surgery were found to be associated with an initial increase or plateau in concentrations of circulating PFAS up to 6 months after surgery followed by a persistent decline in concentrations of 36 months (p < 0.001 for all plasma-PFAS). Bariatric surgery in adolescents was associated with a decline in circulating PFAS concentrations. Initially following bariatric surgery (0-6 months) concentrations were static followed by decline from 6 to 36 months following surgery. This may have large public health implications as PFAS are known to be associated with numerous metabolic related diseases and the significant reduction in circulating PFAS in individuals who have undergone bariatric surgery may be related to the improvement of such metabolic related diseases following bariatric surgery.

Systematic review and meta-analysis of birth weight and perfluorohexane sulfonate exposures: examination of sample timing and study confidence

We examined the association between mean birth weight (BW) differences and perfluorohexane sulfonate (PFHxS) exposure biomarkers.We fit a random effects model to estimate the overall pooled effect and for different strata based on biomarker sample timing and overall study confidence. We also conducted an analysis to examine the impact of a continuous measure of gestational age sample timing on the overall pooled effect.We detected a -7.9 g (95% CI -15.0 to -0.7; pQ=0.85; I2=0%) BW decrease per ln ng/mL PFHxS increase based on 27 studies. The 11 medium confidence studies (β=-10.0 g; 95% CI -21.1 to 1.1) showed larger deficits than 12 high (β=-6.8 g; 95% CI -16.3 to 2.8) and 4 low confidence studies (β=-1.5 g; 95% CI -51.6 to 48.7). 10 studies with mid-pregnancy to late-pregnancy sampling periods showed smaller deficits (β=-3.9 g; 95% CI -17.7 to 9.9) than 5 post-partum studies (β=-28.3 g; 95% CI -69.3 to 12.7) and 12 early sampling studies (β=-7.6 g; 95% CI -16.2 to 1.1). 6 of 12 studies with the earliest sampling timing showed results closer to the null.Overall, we detected a small but statistically significant BW deficit across 27 studies. We saw comparable BW deficit magnitudes in both the medium and high confidence studies as well as the early pregnancy group. Despite no definitive pattern by sample timing, larger deficits were seen in postpartum studies. We also saw results closer to the null for a subset of studies restricted to the earliest biomarker collection times. Serial pregnancy sampling, improved precision in gestational age estimates and more standardised reporting of sample variation and exposure units in future epidemiologic research may offer a greater understanding of the relationship between PFHxS on BW and any potential impact of pregnancy haemodynamics.

Peril in the Pipeline: Unraveling the threads of PFAS contamination in U.S. drinking water systems

We examined the spatial distribution of Per- and Polyfluoroalkyl Substances (PFAS) in the US drinking water and explored the relationship between PFAS contamination, public water systems (PWS) characteristics, and socioeconomic attributes of the affected communities. Using data from the EPA's third Unregulated Contaminant Rule, the Census Bureau, and the Bureau of Labor Statistics, we identified spatial contamination hot spots and found that PFAS contamination was correlated with PWSs size, non-surface raw water intake sources, population, and housing density. We also found that non-white communities had less PFAS in drinking water. Lastly, we observed that PFAS contamination varied depending on regional industrial composition. The results showed that drinking water PFAS contamination was an externality of not only some industrial activities but also household consumption.

Association between per- and polyfluoroalkyl substances exposure and thyroid function biomarkers among females attending a fertility clinic

Per- and polyfluoroalkyl substances (PFAS) exposure was associated with changes in thyroid function in pregnant mothers and the general population. Limited such evidence exists in other susceptible populations such as females with fertility problems. This cross-sectional study included 287 females seeking medically assisted reproduction at a fertility clinic in Massachusetts, United States, between 2005 and 2019. Six long-alkyl chain PFAS, thyroid hormones, and autoimmune antibodies were quantified in baseline serum samples. We used generalized linear models and quantile g-computation to evaluate associations of individual PFAS and their total mixture with thyroid biomarkers. Most females were White individuals (82.7%), had graduate degrees (57.8%), and nearly half had unexplained subfertility (45.9%). Serum concentrations of all examined PFAS and their mixture were significantly associated with 2.6%-5.6% lower total triiodothyronine (TT3) concentrations. Serum concentrations of perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluoroundecanoate (PFUnDA), and of the total mixture were associated with higher ratios of free thyroxine (FT4) to free triiodothyronine (FT3). No associations were found for PFAS and TSH or autoimmune antibodies. Our findings support the thyroid-disrupting effect of long alkyl-chain PFAS among a vulnerable population of subfertile females.

Efficient and fast remediation of soil contaminated by per- and polyfluoroalkyl substances (PFAS) by high-frequency heating

This study presents a novel thermal technology (high-frequency heating, HFH) for the decontamination of soil containing per- and polyfluoroalkyl substances (PFAS) and aqueous film-forming foams (AFFFs). Ultra-fast degradation of short-chain PFAS, long-chain homologs, precursors, legacy PFAS, emerging PFAS was achieved in a matter of minutes. The concentrations of PFAS and the soil type had a negligible impact on degradation efficiency, possibly due to the ultra-fast degradation rate overwhelming potential differences. Under the current HFH experiment setup, we achieved near-complete degradation (e.g., >99.9%) after 1 min for perfluoroalkyl carboxylic acids and perfluoroalkyl ether carboxylic acids and 2 min for perfluoroalkanesulfonic acids. Polyfluoroalkyl precursors in AFFFs were found to degrade completely within 1 min of HFH; no residual cationic, zwitterionic, anionic, or non-ionic intermediate products were detected following the treatment. The gaseous byproducts were considered. Most of gaseous organofluorine products of PFAS at low-and-moderate temperatures disappeared when temperatures reached 890 °C, which is in the temperature zone of HFH. For the first time, we demonstrated minimal loss of PFAS in water during the boiling process, indicating a low risk of PFAS entering the atmosphere with the water vapor. The findings highlight HFH its potential as a promising remediation tool for PFAS-contaminated soils.

Associations between serum per- and polyfluoroalkyl substances and thyroid hormones in Chinese adults: A nationally representative cross-sectional study

Disruption of thyroid homeostasis has been indicated in human studies on the effects of per- and polyfluoroalkyl substances (PFASs). However, limited research exists on this topic within the general Chinese population. Based on a substantial and representative sample of the Chinese adult population, our study provides insight into how PFASs specifically affect thyroid homeostasis. The study included 10 853 participants, aged 18 years and above, sampled from nationally representative data provided by the China National Human Biomonitoring (CNHBM). Weighted multiple linear regression and restricted cubic spline (RCS) models were used to explore the associations between eight individual PFAS concentrations and total thyroxine (T4), total triiodothyronine (T3), and the T4/T3 ratio. Bayesian kernel machine regression (BKMR) and quantile-based g-computation (qgcomp) were employed to explore the joint and independent effects of PFASs on thyroid homeostasis. Both individual PFASs and PFAS mixtures exhibited a significant inverse association with serum T3 and T4 levels, and displayed a positive association with the T4/T3 ratio. Perfluoroundecanoic acid (PFUnDA) [-0.07 (95 % confidence interval (CI): -0.08, -0.05)] exhibited the largest change in T3 level. PFUnDA also exhibited a higher weight compared to other PFAS compounds in qgcomp models. Additionally, a critical exposure threshold for each PFAS was identified based on nonlinear dose-response associations; beyond these thresholds, the decreases in T3 and T4 levels plateaued. Specifically, for perfluoroheptane sulfonic acid (PFHpS) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), an initial decline in hormone levels was observed, followed by a slight increase when concentrations surpassed 0.7 ng/mL and 2.5 ng/mL, respectively. Sex-specific effects were more pronounced in females, and significant associations were observed predominantly in younger age groups. These insights contribute to our understanding of how PFAS compounds impact thyroid health and emphasize the need for further research and environmental management measures to address these complexities.

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.

Per- and Polyfluoroalkyl Substances (PFAS) in Community Water Systems (CWS) and the Risk of Thyroid Cancer: An Ecological Study

Thyroid cancer incidence has been steadily increasing over the past decade in the United States (US). A discussion exists regarding the potential contribution of exposure to endocrine-disrupting chemicals, encompassing certain per- and poly-fluoroalkyl substances (PFASs). This ecological study evaluated the potential correlation between PFAS levels in drinking water and thyroid cancer incidence in the US. Data on age-adjusted thyroid cancer incidence rate (per 100,000 persons) by county were obtained from the Centers for Disease Control and Prevention (CDC) for US counties with available data in 2015-2019. Data on PFAS concentrations in the drinking water of selected community water systems (CWSs) were obtained from the CDC National Environmental Public Health Tracking Network in 2013-2015. The correlation between PFASs in CWSs and thyroid cancer incidence was calculated using Spearman correlation. A statistically significant correlation was found between perfluorooctanoic acid (PFOA) (r = 0.031; p = 0.043), perfluorononanoic acid (PFNA) (r = 0.058; p ≤ 0.001), and thyroid cancer incidence. The results suggest a potential link between certain PFAS exposures and thyroid cancer risk. However, due to the nature of an ecological study, no conclusions can be drawn at the individual level or causality. More research is needed, particularly on an individual level to allow for more detailed exposure assessment.

Per- and polyfluoroalkyl substances (PFAS) and thyroid hormone measurements in dried blood spots and neonatal characteristics: a pilot study

BACKGROUND

Pediatric thyroid diseases have been increasing in recent years. Environmental risk factors such as exposures to chemical contaminants may play a role but are largely unexplored. Archived neonatal dried blood spots (DBS) offer an innovative approach to investigate environmental exposures and effects.

OBJECTIVE

In this pilot study, we applied a new method for quantifying per- and polyfluoroalkyl substances (PFAS) to 18 archived DBS from babies born in California from 1985-2018 and acquired thyroid hormone measurements from newborn screening tests. Leveraging these novel data, we evaluated (1) changes in the concentrations of eight PFAS over time and (2) the relationship between PFAS concentrations, thyroid hormone concentrations, and neonatal characteristics to inform future research.

METHODS

PFAS concentrations in DBS were measured using ultra-high-performance liquid chromatography-mass spectrometry. Summary statistics and non-parametric Wilcoxon rank-sum and Kruskal-Wallis tests were used to evaluate temporal changes in PFAS concentrations and relationships between PFAS concentrations, thyroid hormone concentrations, and neonatal characteristics.

RESULTS

The concentration and detection frequencies of several PFAS (PFOA, PFOS, and PFOSA) declined over the assessment period. We observed that the timing of specimen collection in hours after birth was related to thyroid hormone but not PFAS concentrations, and that thyroid hormones were related to some PFAS concentrations (PFOA and PFOS).

IMPACT STATEMENT

This pilot study examines the relationship between concentrations of eight per- and polyfluoroalkyl substances (PFAS), thyroid hormone levels, and neonatal characteristics in newborn dried blood spots (DBS) collected over a period of 33 years. To our knowledge, 6 of the 22 PFAS we attempted to measure have not been quantified previously in neonatal DBS, and this is the first study to examine both PFAS and thyroid hormone concentrations using DBS. This research demonstrates the feasibility of using newborn DBS for quantifying PFAS exposures in population-based studies, highlights methodological considerations in the use of thyroid hormone data for future studies using newborn DBS, and indicates potential relationships between PFAS concentrations and thyroid hormones for follow-up in future research.

The interference between effects of PFAS exposure on thyroid hormone disorders and cholesterol levels: an NHANES analysis

Studies have documented that per- and polyfluoroalkyl substance (PFAS) exposures are associated with thyroid hormones (TH) and lipid levels. This study investigates whether these effects interfere with each other. We analyzed data on 3954 adults in the US National Health and Nutrition Examination Survey (NHANES; 2007-2012). TH disorder was defined using thyroid hormones. Serum high-density lipoprotein (HDL) cholesterol, total cholesterol, and six types of PFAS were included. Weighted quantile sum (WQS) regression was used to estimate the overall effect of PFAS mixture on TH disorder and cholesterols, respectively. Potential confounders, including age, race, gender, education, household poverty, smoking, and alcohol drinking, were adjusted. PFAS mixture was associated increased risk for TH disorder (odds ratio = 1.21, 95% confidence interval (CI): 1.02, 1.43), higher HDL cholesterol (linear coefficient = 1.31, 95% CI: 0.50, 2.11), and higher total cholesterol (linear coefficient = 5.30, 95% CI: 3.40, 7.21). TH disorder was associated with higher HDL cholesterol (linear coefficient = 2.30, 95% CI: 0.50, 2.11), but not total cholesterol. When adjusted for TH disorder, the effect estimates of PFAS mixture remain roughly unchanged on HDL cholesterol (linear coefficient = 1.13, 95% CI: 0.28, 1.98) and total cholesterol (linear coefficient = 5.61, 95% CI: 3.58, 7.63). Sex modified the effect of PFAS mixture on HDL cholesterol (P for interaction: 0.04) but did not change the interaction between PFAS and TH disorder on cholesterols. We corroborated the adverse health effects of PFAS exposure on TH and lipids; however, these two effects appear to be independent of and not interfere with each other.

Exposure to perfluoroalkyl substances (PFAS) and association with thyroid hormones in adolescent males

BACKGROUND

Perfluoroalkyl substances (PFAS) are found in a wide range of consumer products. Exposure to PFAS in children and adolescents may be associated with alterations in thyroid hormones, which have critical roles in brain function.

OBJECTIVE

This study investigated the association between plasma concentrations of PFAS and serum levels of total triiodothyronine (T3), free thyroxine (T4), and thyroid-stimulating hormone (TSH) in adolescent males.

METHODS

In 2017-2019, 151 boys from the Environment and Childhood (INMA)-Granada birth cohort, Spain, participated in a clinical follow up visit at the age of 15-17 years. Plasma concentrations of ten PFAS (PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFOS, and PFHxS) and serum thyroid hormones were measured in 129 of these boys. Linear regression analysis was performed to determine associations of individual PFAS with total T3, free T4, TSH, and free T4/TSH ratio, and quantile g-computation models were performed to assess the mixture effect. Additional models considered iodine status as effect modifier.

RESULTS

PFOS was the most abundant PFAS in plasma (median = 2.22 μg/L), followed by PFOA (median = 1.00 μg/L), PFNA (median = 0.41 μg/L), and PFHxS (median = 0.40 μg/L). When adjusted by confounders (including age, maternal schooling, and fish intake), PFOA and PFUnDA were associated with an increase in free T4 (β [95% CI] = 0.72 [0.06; 1.38] and 0.36 [0.04; 0.68] pmol/L, respectively, per two-fold increase in plasma concentrations), with no change in TSH. PFOS, the sum of PFOA, PFNA, PFOS, and PFHxS, and the sum of long-chain PFAS were marginally associated with increases in free T4. Associations with higher free T4 and/or total T3 were seen for several PFAS in boys with lower iodine intake (<108 μ/day) alone. Moreover, the PFAS mixture was association with an increase in free T4 levels in boys with lower iodine intake (% change [95% CI] = 6.47 [-0.69; 14.11] per each quartile increase in the mixture concentration).

CONCLUSIONS

Exposure to PFAS, considered individually or as a mixture, was associated with an increase in free T4 levels in boys with lower iodine intake. However, given the small sample size, the extent of these alterations remains uncertain.

Linking Transthyretin-Binding Chemicals and Free Thyroid Hormones: In Vitro to In Vivo Extrapolation Based on a Competitive Binding Model

Large numbers of pollutants competitively inhibit the binding between thyroid hormones and transthyretin (TTR) in vitro. However, the impact of this unintended binding on free thyroid hormones in vivo has not yet been characterized. Herein, we established a quantitative in vitro to in vivo extrapolation (QIVIVE) method based on a competitive binding model to quantify the effect of TTR-binding chemicals on free thyroid hormones in human blood. Twenty-five TTR-binding chemicals including 6 hydroxyl polybromodiphenyl ethers (OH-PDBEs), 6 hydroxyl polychlorobiphenyls (OH-PCBs), 4 halogenphenols, 5 per- and polyfluorinated substances (PFASs), and 4 phenols were selected for investigation. Incorporating the in vitro binding parameters and human exposure data, the QIVIVE model could well predict the in vivo effect on free thyroid hormones. Co-exposure to twenty-five typical TTR-binding chemicals resulted in median increases of 0.080 and 0.060% in circulating levels of free thyroxine (FT4) and free triiodothyronine (FT3) in the general population. Individuals with occupational exposure to TTR-binding chemicals suffered 1.88-32.2% increases in free thyroid hormone levels. This study provides a quantitative tool to evaluate the thyroid-disrupting risks of TTR-binding chemicals and proposes a new framework for assessing the in vivo effects of chemical exposures on endogenous molecules.

Associations of Gestational Perfluoroalkyl Substances Exposure with Early Childhood BMI z-Scores and Risk of Overweight/Obesity: Results from the ECHO Cohorts

BACKGROUND

Gestational per- and polyfluoroalkyl substances (PFAS) exposure may be associated with adiposity and increased risk of obesity among children and adolescents. However, results from epidemiological studies evaluating these associations are inconsistent.

OBJECTIVES

We estimated the associations of pregnancy PFAS concentrations with child body mass index (BMI) z -scores and risk of overweight/obesity in eight U.S. cohorts.

METHODS

We used data from 1,391 mother-child pairs who enrolled in eight Environmental influences on Child Health Outcomes (ECHO) cohorts (enrolled: 1999-2019). We quantified concentrations of seven PFAS in maternal plasma or serum in pregnancy. We measured child weight and height between the ages of 2 and 5 y and calculated age- and sex-specific BMI z -scores; 19.6% children had more than one BMI measurement. We estimated covariate-adjusted associations of individual PFAS and their mixture with child BMI z -scores and risk of overweight/obesity using linear mixed models, modified Poisson regression models, and Bayesian approaches for mixtures. We explored whether child sex modified these associations.

RESULTS

We observed a pattern of subtle positive associations of PFAS concentrations in pregnancy with BMI z -scores and risk of overweight/obesity. For instance, each doubling in perfluorohexane sulfonic acid concentrations was associated with higher BMI z -scores (β = 0.07 ; 95% CI: 0.01, 0.12). Each doubling in perfluroundecanoic acid [relative risk  ( RR ) = 1.10 ; 95% CI: 1.04, 1.16] and N -methyl perfluorooctane sulfonamido acetic acid (RR = 1.06 ; 95% CI: 1.00, 1.12) was associated with increased risk of overweight/obesity, with some evidence of a monotonic dose-response relation. We observed weaker and more imprecise associations of the PFAS mixture with BMI or risk of overweight/obesity. Associations did not differ by child sex.

DISCUSSION

In eight U.S.-based prospective cohorts, gestational exposure to higher levels of PFAS were associated with slightly higher childhood BMI z -score and risk of overweight or obesity. Future studies should examine associations of gestational exposure to PFAS with adiposity and related cardiometabolic consequences in older children. https://doi.org/10.1289/EHP11545.

Associations of per- and polyfluoroalkyl substances and their alternatives with bone mineral density levels and osteoporosis prevalence: A community-based population study in Guangzhou, Southern China

BACKGROUND

Evidence concerning associations of per- and polyfluoroalkyl substances (PFASs) exposure with bone mineral density (BMD) and osteoporosis is scarce. Additionally, no study has examined the effects of PFAS isomers and alternatives on bone health.

OBJECTIVES

To evaluate the associations of PFASs and PFAS alternatives with BMD levels and osteoporosis prevalence.

METHODS

A total of 1260 healthy adults from southern China were enrolled. Serum concentrations of 32 legacy PFASs, PFAS isomers, and alternatives were measured using modified liquid chromatography-tandem mass spectrometry. Logistic and linear regression models were applied to evaluate the associations of PFASs with osteoporosis prevalence and BMD levels, respectively, adjusting for confounding factors. We performed stratified analyses to assess potential effect modifications of age and sex. We further used sensitivity analyses to testify the robustness of the main findings.

RESULTS

There were 204 (16.2 %) participants diagnosed with osteoporosis. Eleven of the studied PFASs (i.e., PFHpA, PFOA, PFBS, PFHpS, total-PFHxS, n-PFHxS, br-PFHxS, br-PFOS, 1m-PFOS, Σ3 + 4 + 5m-PFOS, and 6:2 Cl-PFESA) showed significant and inverse associations with BMD levels (mean differences ranged from -6.47 to -26.07 per one ln-unit increase in the PFASs). Additionally, we observed that each one ln-unit increase in PFHpA was significantly associated a 23 % (OR = 1.23, 95 % CI = 1.04, 1.45) greater odds of osteoporosis. The above associations were consistent in several sensitivity analyses we performed. Stratified analyses showed stronger associations among women and younger compared to their counterparts.

CONCLUSIONS

Our findings suggested that greater PFAS exposure is associated with poorer bone health, especially in women and younger people.

Association between per- and polyfluoroalkyl substances and semen quality

Some studies have suggested that perfluoroalkyl and polyfluoroalkyl substance (PFAS) exposure may be associated with semen quality in the general population, but with inconsistent results. To identify a more precise relationship between them, a meta-analysis was performed. We searched Embase, the PubMed, The Cochrane Library, Ovid databases, and Web of Science databases (before March 2022) for appropriate studies on the correlations of PFAS exposure with semen parameters. We extracted β value and 95% confidence intervals (CIs) to conduct meta-analysis. Subgroup analyses was performed by sample size, geographic location, and sample type. A total of seven articles involving 2190 participants were included in this study. The concentrations of perfluorooctanoic acid (PFOA) (β value =  - 1.38; 95% CI: - 2.44, - 0.32) and perfluorononanoic acid (PFNA) (β value =  - 1.31, 95% CI: - 2.35, - 0.26) were negatively associated with sperm progressive motility. Subgroup analysis revealed that PFNA exposure was related to sperm morphology in studies with the sample size exceeding 200 people (β value =  - 0.14; 95% CI: - 0.26, - 0.01). Our study supports that exposure to some PFASs (e.g., PFNA, PFOA) may be associated with semen quality, such as lower sperm progressive motility. Therefore, it is of great significance for the prevention of male infertility by control the use of PFASs.

Isomer-Specific Serum Concentrations of Perfluorooctane Sulfonic Acid among U.S. Adults: Results from the National Health and Nutrition Examination Survey (NHANES) and the Study of Women's Health Across the Nation Multi-Pollutant Study (SWAN-MPS)

Electrochemical fluorination manufacture of perfluorooctane sulfonic acid (PFOS), one of the most studied per- and polyfluoroalkyl substances, produces mixtures of linear and branched isomers, but little is known about human exposure to linear or branched PFOS isomers. We examined determinants affecting isomer-specific patterns of PFOS in serum in two adult populations in the United States, the National Health and Nutrition Examination Survey (NHANES) and the Study of Women's Health Across the Nation Multi-Pollutant Study (SWAN-MPS). After adjusting for demographic variables, fish consumption (in both populations), a glomerular filtration rate above 90 mL/min/1.73 m2 (observed in NHANES; not tested in SWAN-MPS), premenopausal status (only observed in SWAN-MPS), and less consumption of processed food (observed in SWAN-MPS; not tested in NHANES) were associated with a higher proportion of linear PFOS. Non-Hispanic Black and Asian participants were likely to have a higher proportion of linear PFOS than non-Hispanic White participants in both populations. Our findings suggest that isomer-specific patterns of PFOS serum concentrations in humans vary depending on population characteristics that affect PFOS exposure and excretion. Consideration of specific PFOS isomers in future human biomonitoring and epidemiologic studies can provide useful insight to better understand PFOS exposure.

Association between per- and polyfluoroalkyl substances exposure and risk of diabetes: a systematic review and meta-analysis

BACKGROUND

Emerging evidence suggests that per- and polyfluoroalkyl substances (PFAS) are endocrine disruptors and may contribute to the etiology of diabetes.

OBJECTIVES

This study aimed to systematically review the epidemiological evidence on the associations of PFAS with mortality and morbidity of diabetes and to quantitatively evaluate the summary effect estimates of the existing literature.

METHODS

We searched three electronic databases for epidemiological studies concerning PFAS and diabetes published before April 1, 2022. Summary odds ratio (OR), hazard ratio (HR), or β and their 95% confidence intervals (CIs) were respectively calculated to evaluate the association between PFAS and diabetes using random-effects model by the exposure type, and dose-response meta-analyses were also performed when possible. We also assessed the risk of bias of the studies included and the confidence in the body of evidence.

RESULTS

An initial literature search identified 1969 studies, of which 22 studies were eventually included. The meta-analyses indicated that the observed statistically significant PFAS-T2DM associations were consistent in cohort studies, while the associations were almost non-significant in case-control and cross-sectional studies. Dose-response meta-analysis showed a "parabolic-shaped" association between perfluorooctanoate acid (PFOA) exposure and T2DM risk. Available evidence was rated with "low" risk of bias, and the level of evidence for PFAS and incident T2DM was considered "moderate".

CONCLUSIONS

Our findings suggest that PFAS exposure may increase the risk of incident T2DM, and that PFOA may exert non-monotonic dose-response effect on T2DM risk. Considering the widespread exposure, persistence, and potential for adverse health effects of PFAS, further cohort studies with improvements in expanding the sample size, adjusting the covariates, and considering different types of PFAS exposure at various doses, are needed to elucidate the putative causal associations and potential mode of action of different PFAS on diabetes.

IMPACT STATEMENT

A growing body of evidence suggests that per- and polyfluoroalkyl substances (PFAS) are endocrine disruptors and may contribute to the development of diabetes. However, epidemiological evidence on the associations of PFAS and diabetes is inconsistent. We performed this comprehensive systematic review and meta-analysis to quantitatively synthesize the evidence. The findings of this study suggest that exposure to PFAS may increase diabetes risk among the general population. Reduced exposure to these "forever and everywhere chemicals" may be an important preventative approach to reducing the risk of diabetes across the population.

Thyroid Function: A Target for Endocrine Disruptors, Air Pollution and Radiofrequencies

Thyroid diseases, including congenital hypothyroidism, thyroiditis, and childhood thyrotoxicosis, are progressively increasing. The incidence of thyroid cancer in children and adolescents has also increased in recent decades, mirroring the trends observed in adults. These epidemiologic trends develop in parallel with the rising costs associated with diagnosis and treatment of thyroid diseases. Both genetic and environmental factors are involved in these diseases, and a number of widely diffused toxic chemicals of anthropogenic origin can impair thyroid function and make thyroid cancer worse. Synthetic substances persistently contaminate environmental matrices (i.e., air, soil, water) and the food chain and bio-accumulate in humans, starting from in utero life. Environmental toxins such as air pollutants, endocrine disruptors, and high-frequency electromagnetic fields can act on common targets through common pathways, combined mechanisms, and with trans-generational effects, all of which contribute to thyroid damage. Both experimental and epidemiologic observations show that mechanisms of damage include: modulation of synthesis; transportation and metabolism of thyroid hormones; direct interference with hormone receptors: modulation of gene expression; and autoimmunity. We should not underestimate the available evidence linking environmental pollutants with thyroid disease, cancer included, since toxic substances increasingly diffuse and thyroid hormones play a key role in maintaining systemic metabolic homeostasis during body development. Thus, primary prevention measures are urgently needed in particular to protect children, the most exposed and vulnerable subjects.

Associations between serum perfluoroalkyl acid (PFAA) concentrations and health related biomarkers in firefighters

Firefighters who used aqueous film forming foam in the past have experienced elevated exposures to perfluoroalkyl acids (PFAAs). The objective of this study was to examine the associations between clinical chemistry endpoints and serum concentrations of perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS) and perfluorooctane sulfonate (PFOS) in firefighters. Multiple linear regression was used to assess relationships between PFAA serum concentrations and biochemical markers for cardiovascular disease, kidney-, liver- and thyroid function, in a cross-sectional survey of 783 firefighters with elevated levels of PFHxS, PFHpS and PFOS in relation to the most recently reported levels in the general Australian population. Linear logistic regression was used to assess the odds ratios for selected self-reported health outcomes. Repeated measures linear mixed models were further used to assess relationships between PFAAs and biomarkers for cardiovascular disease and kidney function longitudinally in a subset of the firefighters (n = 130) where serum measurements were available from two timepoints, five years apart. In the cross-sectional analysis, higher levels of all PFAAs were significantly associated with higher levels of biomarkers for cardiovascular disease (total-cholesterol, and LDL-cholesterol). For example, doubling in PFOS serum concentration were associated with increases in total cholesterol (β:0.111, 95% confidence interval (95%CI): 0.026, 0.195 mmol/L) and LDL-cholesterol (β: 0.104, 95%CI:0.03, 0.178 mmol/L). Doubling in PFOA concentration, despite not being elevated in the study population, were additionally positively associated with kidney function marker urate (e.g., β: 0.010, 95%CI; 0.004, 0.016 mmol/L) and thyroid function marker TSH (e.g., β: 0.087, 95%CI: 0.014, 0.161 mIU/L). PFAAs were not associated with any assessed self-reported health conditions. No significant relationships were observed in the longitudinal analysis. Findings support previous studies, particularly on the association between PFAAs and serum lipids.

Exposure to perfluoroalkyl substances and neonatal immunoglobulin profiles in the upstate KIDS study (2008-2010)

Infant exposure to per/polyfluoroalkyl compounds is associated with immune disruption. We examined associations between neonatal concentrations of perflurooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and immunoglobulin (Ig) isotype profiles in a prospective cohort of infants. We measured Ig isotypes, including IgA, IgE, IgM and the IgG subclasses IgG1, IgG2, IgG3, and IgG4, and PFOA and PFOS in newborn dried bloodspots from N = 3175 infants in the Upstate KIDS Study (2008-2010). We examined the association between newborn Ig isotype levels and individual PFOS and PFOA concentrations using mixed effects regression models with a random intercept to account for twins among study participants. We assessed the joint effect PFOA and PFOS with quantile-based g-computation on all singletons and one randomly selected twin (N = 2901), with Ig categorized as above or below median value. Models were adjusted for infant sex, and maternal pre-pregnancy body mass index, race, parity, age and infertility treatment. In adjusted models, PFOA was inversely associated with IgE (coefficient = -0.12 per unit increase in PFOA, 95% CI: -0.065, -0.17), whereas IgG2, IgM, and IgA were positively associated with PFOA (coefficient for IgG2 = 0.22, 95% CI: 0.15, 0.27; coefficient for IgM = 0.11, 95% CI: 0.08, 0.15; and coefficient for IgA = 0.15, 95% CI: 0.07, 0.18). There was no relation between PFOS and Ig isotypes. Analysis of the joint effect of PFOA and PFOS showed an OR of 1.2 (95% CI: 1.04, 1.36) for IgA and OR of 1.12 (95% CI: 1.00, 1.24) for IgG2 levels above the median for every quartile increase. PFOA levels were significantly associated with elevated IgA, IgM, IgG2, and reduced levels of IgE in single-pollutant models. A small but significant joint effect of PFOA and PFOS was observed. Our results suggest that early exposure to PFOA and PFOS may disrupt neonatal immunoglobulin levels.

Reproductive and developmental toxicity of perfluorooctane sulfonate (PFOS) in the white-footed mouse (Peromyscus leucopus)

Concerns about per- and polyfluoroalkyl substances (PFAS) stem from their ubiquitous presence in the environment, bioaccumulation, resistance to degradation, and toxicity. Previously, toxicity data relevant to ecological risk assessment has largely been aquatic, terrestrial invertebrates, or avian in origin. In this study, repeated oral exposures of perfluorooctane sulfonate (PFOS) were administered to white-footed mice (Peromyscus leucopus) to evaluate effects on reproduction and development. Prenatal exposure to high doses of PFOS caused neonatal mortality, though growth and development were unaffected by low doses. Additionally, parental (P) generation animals exhibited increased liver:body weight, increased hepatocyte cytoplasmic vacuolization, and decreased serum thyroxine (T4) levels. Total litter loss was selected as the protective critical effect in this study resulting in a benchmark dose low (BMDL) of 0.12 mg/kg-d PFOS. Importantly, PFOS exposure has been linked to reduced adult recruitment in myriad species and at similar thresholds to this study. Similarities in critical/toxicologic effects across taxa may add confidence in risk assessments at sites with multiple taxa or environments.

Per- and Polyfluoroalkyl Substances and Incident Hypertension in Multi-Racial/Ethnic Women: The Study of Women's Health Across the Nation

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are ubiquitous synthetic chemicals that may disrupt blood pressure controls; however, human evidence to support this hypothesis is scant. We examined the association between serum concentrations of PFAS and risks of developing hypertension.

METHODS

This study included 1058 midlife women initially free of hypertension from the multiracial and multiethnic SWAN (Study of Women's Health Across the Nation) with annual follow-up visits between 1999 and 2017. Hypertension was defined as blood pressure ≥140 mm Hg systolic or ≥90 mm Hg diastolic or receiving antihypertensive treatment. Cox proportional hazards models were utilized to calculate hazard ratios and 95% CIs. Quantile g-computation was implemented to evaluate the joint effect of PFAS mixtures.

RESULTS

During 11 722 person-years of follow-up, 470 participants developed incident hypertension (40.1 cases per 1000 person-years). Compared with the lowest tertile, women in the highest tertile of baseline serum concentrations had adjusted hazard ratios of 1.42 (95% CI, 1.19-1.68) for perfluorooctane sulfonate (P trend=0.01), 1.47 (95% CI, 1.24-1.75) for linear perfluorooctanoate (P trend=0.01), and 1.42 (95% CI, 1.19-1.70) for 2-(N-ethyl-perfluorooctane sulfonamido) acetate (P trend=0.01). No significant associations were observed for perfluorononanoate and perfluorohexane sulfonate. In the mixture analysis, women in the highest tertile of overall PFAS concentrations had a hazard ratio of 1.71 (95% CI, 1.15-2.54; P trend=0.008), compared with those in the lowest tertile.

CONCLUSIONS

Several PFAS showed positive associations with incident hypertension. These findings suggest that PFAS might be an underappreciated contributing factor to women's cardiovascular disease risk.

Leveraging Systematic Reviews to Explore Disease Burden and Costs of Per- and Polyfluoroalkyl Substance Exposures in the United States

Accelerating evidence confirms the contribution of per- and polyfluoroalkyl substances (PFAS) to disease burden and disability across the lifespan. Given that policy makers raise the high cost of remediation and of substituting PFAS with safer alternatives in consumer products as barriers to confronting adverse health outcomes associated with PFAS exposure, it is important to document the costs of inaction even in the presence of uncertainty. We therefore quantified disease burdens and related economic costs due to legacy PFAS exposures in the US in 2018. We leveraged systematic reviews and used meta-analytic inputs whenever possible, identified previously published exposure-response relationships, and calculated PFOA- and PFOS-attributable increases in 13 conditions. These increments were then applied to census data to determine total annual PFOA- and PFOS-attributable cases of disease, from which we calculated economic costs due to medical care and lost productivity using previously published cost-of-illness data. We identified PFAS-attributable disease costs in the US of $5.52 billion across five primary disease endpoints shown to be associated with PFAS exposure in meta-analyses. This estimate represented the lower bound, with sensitivity analyses revealing as much as $62.6 billion in overall costs. While further work is needed to assess probability of causation and establish with greater certainty effects of the broader category of PFAS, the results confirm further that public health and policy interventions are still necessary to reduce exposure to PFOA and PFOS and their endocrine-disrupting effects. This study demonstrates the large potential economic implications of regulatory inaction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-022-00496-y.

The association between blood PFAS concentrations and clinical biochemical measures of organ function and metabolism in participants of the Canadian Health Measures Survey (CHMS)

Per- and poly-fluoroalkyl substances (PFAS) are ubiquitous and may persist in human tissue for several years. Only a small proportion of PFAS have been studied for human health effects. We tested the association between human blood levels of six PFAS and several clinical measures of organ and metabolic function in a nationally representative sample of 6768 participants aged 3-79 years old who participated in the Canadian Health Measures Survey. Cross-sectional associations were assessed by generalized linear mixed models incorporating survey-specific sampling weights. An increase in perfluorooctanoic acid (PFOA) equivalent to the magnitude of its geometric mean (GM) of 2.0 μg/L was associated with percentage (95% CI) increases in serum enzymes reflecting liver function: aspartate aminotransferase (AST) 3.7 (1.1, 6.4), gamma-glutamyl transferase (GGT) 11.8 (2.5, 21.8), alanine aminotransferase (ALT) 3.2 (0.5, 5.9), and bilirubin 3.6 (2.7, 4.5). A GM increase in perfluorodecanoic acid (PFDA) of 0.2 μg/L was positively associated with percentage increases in GGT, triglycerides, low-density lipoprotein (LDL) cholesterol, total cholesterol, and calcium with respective increases of 15.5 (2.2, 30.4), 7.0 (1.0, 13.2), 10.7 (5.5, 16.1), 2.8 (0.2, 5.3), and 0.8 (0.3, 1.3). PFOA, perfluorooctane sulfonate (PFOS), PFDA and perfluorononanoic acid (PFNA) were positively associated with GGT. All six congeners were positively associated with at least one biomarker of lipid metabolism, and 5 of 6, PFOA, PFOS, PFDA, perfluorohexane sulfonate (PFHxS) and PFNA were positively associated with serum calcium. Exposure to selected PFAS is associated with clinical blood tests reflecting metabolism and the function of several organ systems. These relatively small changes may possibly indicate early pathology that is clinically inapparent and may possibly be of significance in a general population or in individuals exposed to very high levels of PFAS.

Toward a Mechanistic Understanding of Poly- and Perfluoroalkylated Substances and Cancer

Poly- and perfluoroalkylated substances (PFAS) are chemicals that persist and bioaccumulate in the environment and are found in nearly all human populations through several routes of exposure. Human occupational and community exposure to PFAS has been associated with several cancers, including cancers of the kidney, testis, prostate, and liver. While evidence suggests that PFAS are not directly mutagenic, many diverse mechanisms of carcinogenicity have been proposed. In this mini-review, we organize these mechanisms into three major proposed pathways of PFAS action-metabolism, endocrine disruption, and epigenetic perturbation-and discuss how these distinct but interdependent pathways may explain many of the proposed pro-carcinogenic effects of the PFAS class of environmental contaminants. Notably, each of the pathways is predicted to be highly sensitive to the dose and window of exposure which may, in part, explain the variable epidemiologic and experimental evidence linking PFAS and cancer. We highlight testicular and prostate cancer as models to validate this concept.

Longitudinal trajectories and determinants of plasma per- and polyfluoroalkyl substance (PFAS) levels from birth to early childhood and metabolomic associations: A pilot study in the Boston Birth Cohort

Background

Per- and polyfluoroalkyl substances (PFAS) are a major public health concern worldwide due to their ubiquitous exposures, environmental persistence, maternal-to-fetal transfer, and multi-organ toxicity. This pilot study aimed to generate preliminary data to inform future studies to address data gaps in the field, including early life PFAS exposure levels, longitudinal changes, determinants, and associated metabolomic alterations in understudied Black and Hispanic children in the United States (U.S.).

Methods

This study leveraged existing biosamples and data in the Boston Birth Cohort and measured 12 legacy and emerging PFAS, including Me-PFOSA-AcOH, PFDA, PFDoA, PFHxS, PFNA, PFOA, PFOS, PFUnA, GenX, ADONA, 9Cl-PF3ONS, and PFHpS, in paired cord and early childhood plasma samples. Summary statistics and graphic plots were used to depict PFAS levels at the two time points and their longitudinal changes. Linear regression models were used to identify the early-life factors associated with cord and early childhood PFAS levels. Associations of cord PFAS with cord metabolites were explored using a metabolome-wide association approach and a targeted approach.

Results

This study included 39 children, of whom 25 (64%) were Black, 14 (36%) were Hispanic, and 15 (38%) were female. PFOA, PFOS, PFNA, and PFHpS were detectable in all cord and early childhood plasma samples, while GenX and ADONA were not detectable in any sample. Cord PFAS levels were weakly-to-moderately correlated with early childhood PFAS levels (r = -0.03 to 0.40). Several maternal and child factors, including gestational age, year at blood collection, and race/ethnicity, were associated with cord and early childhood PFAS levels. The metabolome-wide association study and the targeted study identified several cord metabolites that may have been affected by in utero PFAS exposure.

Conclusions

This pilot study found ubiquitous exposure to multiple PFAS in cord plasma (reflects in utero exposure) and in early childhood plasma (reflects both prenatal and postnatal exposure) among U.S. Black and Hispanic children. Metabolomic analysis suggests that in utero PFAS exposures may alter fetal metabolism. Future large-scale studies are needed to replicate the findings and further examine the associations of fetal PFAS exposure with long-term health outcomes and underlying metabolic pathways.

Chlorinated Polyfluorinated Ether Sulfonates and Thyroid Hormone Levels in Adults: Isomers of C8 Health Project in China

Chlorinated polyfluorinated ether sulfonates (Cl-PFESAs) are one kind of replacement chemistry for perfluorooctanesulfonate (PFOS). Recent studies have shown that Cl-PFESAs could interfere with thyroid function in animal models. However, epidemiological evidence on the link between Cl-PFESAs and thyroid function remains scarce. In this study, we focused on two representative legacy perfluoroalkyl substances (PFAS), including PFOS and perfluorooctanoic acid (PFOA), and two PFOS alternatives (6:2 and 8:2 Cl-PFESAs) in the general adult population from a cross-sectional study, the "Isomers of C8 Health Project in China". Three serum thyroid hormones (THs), thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4), were measured. We fitted generalized linear regression, restricted cubic spline regression, and Bayesian kernel machine regression models to assess associations of individual Cl-PFESAs, legacy PFAS, and PFAS mixtures with THs, respectively. We found individual PFAS and their mixtures were nonlinearly associated with THs. The estimated changes of the TSH level (μIU/mL) at the 95th percentile of 6:2 Cl-PFESA and PFOS against the 5th percentile were -0.74 (95% CI: -0.94, -0.54) and -1.18 (95% CI: -1.37, -0.98), respectively. The present study provided epidemiological evidence for the association of 6:2 Cl-PFESA with thyroid hormone levels in the general adult population.

Association Between Exposure to Per- and Polyfluoroalkyl Substances and Birth Outcomes: A Systematic Review and Meta-Analysis

Background

A large body of emerging evidence suggests that per- and polyfluoroalkyl substances (PFAS) affect birth outcomes in various pathways, but the evidence is inconsistent. Therefore, this study aimed to systematically review the epidemiological evidence on PFAS exposure and birth outcomes.

Methods

Three electronic databases were searched for epidemiological studies through February 13, 2021. We used random-effects meta-analysis for eight birth outcome indicators to calculate summary effect estimates for various exposure types. The risk of bias and the overall quality and level of evidence for each exposure-outcome pair were assessed.

Results

The initial search identified 58 potentially eligible studies, of which 46 were ultimately included. Many PFAS were found to have previously unrecognized statistically significant associations with birth outcomes. Specifically, birth weight (BW) was associated with PFAS, with effect sizes ranging from −181.209 g (95% confidence interval (CI) = −360.620 to −1.798) per 1 ng/ml increase in perfluoroheptanesulfonate (PFHpS) to −24.252 g (95% CI = −38.574 to −9.930) per 1 ln (ng/ml) increase in perfluorodecaoic acid (PFDA). Similar patterns were observed between other PFAS and birth outcomes: perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) with birth length (BL) and ponderal index (PI), PFOS and perfluorododecanoic acid (PFDoDA) with head circumference (HC), PFHpS with gestational age (GA), and perfluorononanoic acid (PFNA) and PFHpS with preterm birth (PTB). Additionally, PFDA showed a statistically significant association with small for gestational age (SGA). The level of the combined evidence for each exposure-outcome pair was considered to be “moderate”.

Conclusion

This study showed that PFAS exposure was significantly associated with increased risks of various adverse birth outcomes and that different birth outcome indicators had different degrees of sensitivity to PFAS. Further studies are needed to confirm our results by expanding the sample size, clarifying the effects of different types or doses of PFAS and the time of blood collection on birth outcomes, and fully considering the possible confounders.

Association between perfluoroalkyl substances concentration and bone mineral density in the US adolescents aged 12-19 years in NHANES 2005-2010

BACKGROUND

Reports on the association of perfluoroalkyl substances (PFASs) exposure with adolescent bone health are scarce, and studies have primarily targeted maternal serum.

OBJECTIVE

We evaluated the relationship between autologous serum perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) levels and bone mineral density (BMD) in adolescents.

METHODS

We analyzed data from 1228 adolescents aged 12-19 years in the National Health and Nutrition Examination Survey (NHANES) 2005-2010 and used multiple regression analysis to identify the relationship between serum PFOA, PFOS, PFHxS, and PFNA concentrations and total femur, femoral neck, and lumbar spine BMD, in addition to multiple stratified subgroup analyses.

RESULTS

The mean age of participants was 15 years, males had higher serum PFAS concentrations than females. The results of multiple regression analysis showed that the natural log(ln)-transformed serum PFOA, PFOS, and PFNA concentrations were negatively correlated with total femur, femoral neck, and lumbar spine BMD (all p < 0.05), and ln-PFHxS was positively correlated with total femur and femoral neck BMD (all p< 0.05). In males, ln-PFOA was negatively associated with total femur and lumbar spine BMD (all p< 0.05), ln-PFOS was associated with the reduced total femur, femoral neck, and lumbar spine BMD (all p< 0.05), while ln-PFHxS and ln-PFNA were not observed to correlate with BMD at these three sites. In females, both ln-PFOA and ln-PFOS were negatively correlated with total femur and lumbar spine BMD (all p< 0.05), ln-PFHxS is associated with the increased total femur and femoral neck BMD (all p< 0.05), and ln-PFNA was negatively correlated with total femur and femoral neck BMD (all p< 0.05), most of the associations were confined to females. The associations of ln-PFOS with femoral neck BMD and ln-PFNA with total femur BMD were more significant in those who were overweight/obese and had anemia, respectively (all p for interaction < 0.05).

CONCLUSIONS

In this representative sample of US adolescents aged 12-19 years, certain PFAS were associated with lower bone mineral density, and most of the associations were confined to females. The negative effect of PFAS on BMD is more pronounced in those who are overweight/obese and have anemia. However, further studies are needed to confirm this finding.

Correlates of plasma concentrations of per- and poly-fluoroalkyl substances among reproductive-aged Black women

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in commercial and consumer goods. Black women are underrepresented in studies of PFAS exposure.

METHODS

We performed a cross-sectional analysis of correlates of plasma PFAS concentrations among 1499 Black women aged 23-35 participating in the Study of Environment, Lifestyle, and Fibroids (SELF), a Detroit-based cohort study. At baseline (2010-2012), participants provided questionnaire data on socio-demographics; behaviors; diet; and menstrual, contraceptive, and reproductive histories. Using mass spectrometry in non-fasting plasma samples collected at enrollment, we quantified several PFAS, including perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), and 2-N-methyl-perfluorooctane sulfonamido acetate (MeFOSAA). We used linear regression to calculate percentage differences (%D) and 95 % confidence intervals (CIs) for associations between selected correlates and PFAS concentrations, adjusting for all other correlates.

RESULTS

PFHxS, PFOS, PFOA, and PFNA were detected in ≥97 % of women; PFDA in 86 %; MeFOSAA in 70 %; and PFUnDA in 52 %. Age, income, education, and intakes of water, alcohol, and seafood were positively associated with several PFAS. Current smoking was positively associated with MeFOSAA. Body mass index was inversely associated with most PFAS, except PFHxS. Strong inverse associations (%D; 95 % CI) were observed between parity (≥3 vs. 0 births) and PFHxS (-34.7; -43.0, -25.1) and PFOA (-33.1; -39.2, -26.3); breastfeeding duration (≥6 months vs. nulliparous) and PFOA (-31.1; -37.8, -23.7), PFHxS (-24.2; -34.5, -12.3), and PFOS (-18.4; -28.3, -7.1); recent birth (<2 years ago vs. nulliparous) and PFOA (-33.1; -39.6, -25.8), PFHxS (-29.3; -39.0, -18.1), PFNA (-25.2; -32.7, -16.8), and PFOS (-18.3; -28.3, -6.9); and intensity of menstrual bleed (heavy vs. light) and PFHxS (-18.8; -28.3, -8.2), PFOS (-16.4; -24.9, -7.1), PFNA (-10.5; -17.8, -2.6), and PFOA (-10.0; -17.2, -2.1). Current use of depot medroxyprogesterone acetate (DMPA) was positively associated with PFOS (20.2; 1.4, 42.5), PFOA (16.2; 1.5, 33.0), and PFNA (15.3; 0.4, 32.4).

CONCLUSIONS

Reproductive factors that influence PFAS elimination showed strong associations with several PFAS (reduced concentrations with parity, recent birth, lactation, heavy menstrual bleeding; increased concentrations with DMPA use).

Comparative Evaluation of the Effects of Legacy and New Generation Perfluoralkyl Substances (PFAS) on Thyroid Cells In Vitro

BACKGROUND

Per- and poly-fluorinated alkyl substances (PFAS) are environment-persitent emerging endocrine disrupting chemicals raising health concerns worldwide. Exposure to PFAS has been associated with the imbalance of thyroid hormones. However, available studies addressing the cell mechanism underlying thyroid disrupting feature of legacy PFAS, such as perfluoro-octanoic acid (PFOA), perfluoro-octane-sulfonic acid (PFOS), and the new generation substitutes, such as C6O4, are still lacking. In this study the potential disrupting effect of PFOA, PFOS, and C6O4 on a murine thyroid cell model was assessed.

METHODS

A rat FRTL-5 cell line was used as the normal thyroid follicular cell model. Cell iodide-uptake, induced by thyroid stimulating hormone (TSH), was used to assess the functional impact of PFAS exposure on cell function. Tetrazolium salt-based cell viability assay and merocyanine 540-based cell staining were used to address the possible involvement of cell toxicity and membrane biophysical properties on altered cell function. The possible direct interaction of PFAS with TSH-receptor (TSH-R) was investigated by computer-based molecular docking and analysis of molecular dynamics. Evaluation of intracellular cAMP levels and gene expression analysis were used to validate the direct impairment of TSH-R-mediated downstream events upon PFAS exposure.

RESULTS

Different from PFOS or C6O4, exposure to PFOA at a concentration ≥ 10 ng/mL was associated with significant impairment of the iodide uptake upon TSH stimulation (respectively: basal 100.0 ± 19.0%, CTRL + TSH 188.9 ± 7.8%, PFOA 10 ng/mL + TSH 120.4 ± 20.9%, p= 0.030 vs CTRL + TSH; PFOA 100 ng/mL + TSH 115,6 ± 12,3% p= 0.017 vs CTRL + TSH). No impairment of cell viability or membrane stability was observed. Computational analysis showed a possible direct differential interaction of C6O4, PFOA, and PFOS on a same binding site of the extracellular domain of TSH-R. Finally, exposure to PFOA was associated with a significant reduction of downstream intracellular cAMP levels and both sodium-iodide transporter and thyroperoxidase gene expression upon TSH-R stimulation.

CONCLUSIONS

Our data suggest that legacy and new generation PFAS can differentially influence TSH dependent signaling pathways through the direct interaction with TSH-R.

Metabolic Syndrome and Endocrine Disrupting Chemicals: An Overview of Exposure and Health Effects

Increasing prevalence of metabolic syndrome (MetS) is causing a significant health burden among the European population. Current knowledge supports the notion that endocrine-disrupting chemicals (EDCs) interfere with human metabolism and hormonal balance, contributing to the conventionally recognized lifestyle-related MetS risk factors. This review aims to identify epidemiological studies focusing on the association between MetS or its individual components (e.g., obesity, insulin resistance, diabetes, dyslipidemia and hypertension) and eight HBM4EU priority substances (bisphenol A (BPA), per- and polyfluoroalkyl substances (PFASs), phthalates, polycyclic aromatic hydrocarbons (PAHs), pesticides and heavy metals (cadmium, arsenic and mercury)). Thus far, human biomonitoring (HBM) studies have presented evidence supporting the role of EDC exposures on the development of individual MetS components. The strength of the association varies between the components and EDCs. Current evidence on metabolic disturbances and EDCs is still limited and heterogeneous, and mainly represent studies from North America and Asia, highlighting the need for well-conducted and harmonized HBM programmes among the European population. Rigorous and ongoing HBM in combination with health monitoring can help to identify the most concerning EDC exposures, to guide future risk assessment and policy actions.

Developing potency factors for thyroid hormone disruption by PFASs using TTR-TRβ CALUX® bioassay and assessment of PFASs mixtures in technical products

BACKGROUND

Over the last decade, per- and polyfluoroalkyl substances (PFASs) have become one of the most heavily investigated persistent organohalogen compound class of environmental concern. However, knowledge about their toxicology is still scarce, although PFASs as individual compounds and their industrial mixtures were shown to exert effects on the thyroid hormone system.

METHODS

In vitro toxicity potency factors were established for thyroid hormone transport disruption potential using the novel TTR-TRβ CALUX® bioassay for major PFASs. We assessed technical PFASs mixtures, including aqueous film-forming foam (AFFF) surfactants and chromium mist suppressants (CMS) applications with and without total oxidizable precursor (TOP) by TTR-TRβ CALUX® assay for their thyroid hormone transport disrupting potential.

RESULTS

All PFASs listed in the German guideline for drinking water (German Environment Agency, 2017) affected the T4 binding to TTR, an important plasma thyroid hormone transport protein. For all tested PFASs, potency factors based on PC₈₀ values relative to PFOA could be obtained and ranged between PFBA (0.0018) and PFOS (2.0). Applying in vitro potency factors obtained from the present in vitro TTR-TRβ CALUX® assay study and recently reported in vivo potency factors (Zeilmaker et al., 2018; Bil et al., 2021) on the above-mentioned German guideline for PFAS in drinking water, showed that the cumulative effect-based trigger values (in vivo and in vitro) are comparable (3.0 vs. 2.9 to 4.6 μg PFOA-EQ/l). Additionally, AFFF surfactants and CMS with and without TOP assay were tested. Highest activities were found in the older AFFF surfactants (2013/2014) due to higher PFOS/PFOA levels, which were already substituted with 6:2 FTS in 2019, resulting in much lower PFOA-EQ levels. As expected also the PFOA-EQ levels increased in the samples with TOP treatment compared to the original AFFF surfactants and CMS as confirmed here by biological and chemical PFOA-equivalents (PFOA-EQ) analysis. Additionally, CMS (which have been used in the electroplating chromium industry since the 1950s) as well as PFOS-free, but not PFAS-free fume suppressants (such as Fumetrol® 21) have been tested in the TTR-TRβ CALUX® assay and showed much lower activity levels then the AFFFs, confirmed by the similar potency determination based on chemical PFASs analysis followed by transformation to PFOA-EQ for comparison. The potency factor of 6:2 FTS, which is the main substitute for PFOS in CMS, indicates that it is approximately 100-times less potent as a thyroid hormone disruptor as compared to PFOS.

CONCLUSION

Potency factors based on PC₈₀ values from TTR-TRβ CALUX® relative to PFOA have been developed for major PFASs. In AFFF surfactants and CMS a trend of higher activities with higher amounts of PFOS and PFOA have been found. PFOA and PFOS showed high responses in the TTR-TRβ CALUX® assay and had the largest contributions to the PFOA-EQs in the AFFF surfactants and CMS applications. Using potency factors as determined in the TTR-TRβ CALUX® to convert PFASs assessed by chemical analysis to PFOA-EQ led to comparable results as compared to the results from PFASs measured directly by the TTR-TRβ CALUX® assay. This study supports the claim that semiquantitative effect- and group-based in vitro CALUX bioanalysis tools can be applied effectively to assess industrial products containing complex mixtures with PFAS compounds for which no instrumental analysis are established, and for many compounds where in vitro toxicity data are not yet available.

Buy-now-pay-later: Hazards to human and planetary health from plastics production, use and waste

More than 8 billion tonnes of plastic were produced between 1950 and 2015, that is 1 tonne for every man, woman and child on our planet. Global plastic production has been growing exponentially with an annual growth rate of 8.4% since 1950, equating to approximately 380 million tonnes per annum. A further 50 kg of plastic is now being produced for each person every year with production continuing to accelerate. Here, we discuss the human and planetary health hazards of all that plastic. We consider each step in the journey of these complex and pervasive industrial materials: from their synthesis predominantly from fossil fuel feedstocks, through an often-brief consumer use as plastic products, and onto waste streams as fuel, permanent landfill or as unmanaged waste in our environment, food, air and bodies.

Exposure to novel and legacy per- and polyfluoroalkyl substances (PFASs) and associations with type 2 diabetes: A case-control study in East China

Associations between per- and polyfluoroalkyl substances (PFASs) and the incidence of type 2 diabetes are controversial in epidemiological studies. In addition, limited data are available for assessing the health effects of novel PFAS alternatives. Our study evaluated the effects of PFAS exposure on type 2 diabetes by estimating the associations of PFASs in human serum with the risk of type 2 diabetes and levels of glycemic biomarkers and lipid fractions. The case-control study consisted of 304 participants from Shandong Province, East China, half of which were diagnosed with type 2 diabetes. Logistic regression showed that most PFASs were inversely associated with the risk of type 2 diabetes after adjusting for age, sex, and body mass index. However, concentrations of perfluorooctanoic acid (PFOA) in the control group were positively associated with fasting plasma glucose levels (β = 0.04, 95% confidence interval (CI): 0.0003, 0.08), which may promote the development of type 2 diabetes. Furthermore, each log-unit increase in the concentrations of perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnDA), and 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (Cl-PFESA) were associated with a total cholesterol increase (i.e., 17.49% (95% CI: 0.93%, 34.90%), 17.49% (95% CI: 4.71%, 31.83%), and 17.49% (95% CI: 4.71%, 31.83%), respectively). Positive associations were also observed between PFNA, PFUnDA, perfluorooctane sulfonate (PFOS), and 6:2 Cl-PFESA and low-density lipoprotein cholesterol. However, no associations between PFASs and hemoglobin A1c, triglycerides, or high-density lipoprotein cholesterol reached statistical significance, nor associations between PFAS mixtures and outcomes of interest. In conclusion, the significant correlations between serum PFASs and glycemic biomarkers and lipid fractions indicated that PFAS exposure may be a potential diabetogenic factor. To the best of our knowledge, this is the first study to assess the associations between novel Cl-PFESAs and type 2 diabetes, although the inverse associations observed require clarification in future studies.

Associations of single and multiple per- and polyfluoroalkyl substance (PFAS) exposure with vitamin D biomarkers in African American women during pregnancy

Vitamin D has been linked to various physiological functions in pregnant women and their fetuses. Previous studies have suggested that some per- and polyfluoroalkyl substances (PFAS) may alter serum vitamin D concentrations. However, no study has investigated the relationship between PFAS and vitamin D in pregnant women. This study aims to evaluate the associations of serum PFAS with serum total and free 25-hydroxyvitamin D (25(OH)D) during pregnancy in a cohort of African American women in Atlanta, GA. Blood samples from 442 participants were collected in early pregnancy (8-14 weeks of gestation) for PFAS and 25(OH)D measurements, and additional samples were collected in late pregnancy (24-30 weeks) for the second 25(OH)D measurements. We fit multivariable linear regressions and weighted quantile sum (WQS) regressions to estimate the associations of individual PFAS and their mixtures with 25(OH)D concentrations. We found mostly positive associations of total 25(OH)D with PFHxS (perfluorohexane sulfonic acid), PFOS (perfluorooctane sulfonic acid), PFDA (perfluorodecanoic acid), and NMeFOSAA (N-methyl perfluorooctane sulfonamido acetic acid), and negative associations with PFPeA (perfluoropentanoic acid). For free 25(OH)D, positive associations were observed with PFHxS, PFOS, PFOA (perfluorooctanoic acid), and PFDA, and a negative association with PFPeA among the women with male fetuses in the models using 25(OH)D measured in late pregnancy. In mixture models, a quartile increase in WQS index was associated with 2.88 ng/mL (95%CI 1.14-4.59) and 5.68 ng/mL (95%CI 3.31-8.04) increases in total 25(OH)D measured in the early and late pregnancy, respectively. NMeFOSAA, PFDA, and PFOS contributed the most to the overall effects among the eight PFAS. No association was found between free 25(OH)D and the PFAS mixture. These results suggest that PFAS may affect vitamin D biomarker concentrations in pregnant African American women, and some of the associations were modified by fetal sex.

Chronic exposure to perfluorohexane sulfonate leads to a reproduction deficit by suppressing hypothalamic kisspeptin expression in mice

Background

Perfluorohexane sulfonate (PFHxS) is a six-carbon perfluoroalkyl sulfonic acid found as an environmental contaminant. This study aims to investigate the effects of PFHxS exposure on female reproduction and the underlying mechanism in mice.

Methods

Eight-week-old ICR mice were divided randomly into four groups administered corn oil (vehicle) and PFHxS at doses of 0.5, 5, and 50 mg/kg/day for 42 days by intragastric administration. Body weight, ovarian weight, estrous cycle, follicle counts, and serum sex hormone levels were evaluated. The expression of kisspeptin and gonadotropin releasing hormone (GnRH) in the hypothalamus was also detected.

Results

Compared to vehicle exposure, 5 mg/kg/day PFHxS treatment prolonged the estrous cycle, especially the duration of diestrus, after 42 days of treatment. The numbers of secondary follicles, antral follicles and corpus lutea were significantly reduced in the PFHxS-treated mice. Moreover, compared with the control mice, the PFHxS-treated mice showed decreases in the serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estrogen (E2), and reduced GnRH mRNA levels, along with the lack of an LH surge. Furthermore, the PFHxS-treated mice had lower levels of kisspeptin immunoreactivity and kiss-1 mRNA in the arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV) than the control mice. After intraventricular administration of kisspeptin-10, the numbers of secondary follicles, antral follicles and corpus lutea recovered, along with the levels of GnRH mRNA, FSH, and LH in the mice treated with 5 mg/kg/day PFHxS.

Conclusion

These results indicate that chronic exposure of mice to 5 mg/kg/day PFHxS affects reproductive functions by inhibiting kisspeptin expression in the ARC and AVPV regions, leading to deficits in follicular development and ovulation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00903-z.

Per and poly-fluoroalkyl substances (PFAS) as a contaminant of emerging concern in surface water: A transboundary review of their occurrences and toxicity effects

Per and poly-fluoroalkyl substances (PFAS) have been recognized as contaminants of emerging concerns by the United States Environmental Protection Agency (US EPA) due to their environmental impact. Several advisory guidelines were proposed worldwide aimed at limiting their occurrences in the aquatic environments, especially for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). This review paper aims to provide a holistic review in the emerging area of PFAS research by summarizing the spatiotemporal variations in PFAS concentrations in surface water systems globally, highlighting the possible trends of occurrences of PFAS, and presenting potential human health impacts as a result of PFAS exposure through surface water matrices. From the data analysis in this study, occurrences of PFOA and PFOS in many surface water matrices were observed to be several folds higher than the US EPA health advisory level of 70 ng/L for lifetime exposure from drinking water. Direct discharge and atmospheric deposition were identified as primary sources of PFAS in surface water and cryosphere, respectively. While global efforts focused on limiting usages of long-chain PFAS such as PFOS and PFOA, the practices of using short-chain PFAS such as perfluorobutanoic acid (PFBA) and perfluorobutane sulfonic acid (PFBS) and PFAS alternatives increased substantially. These compounds are also potentially associated with adverse impacts on human health, animals and biota.

Perfluoroalkyl and polyfluoroalkyl substances and body size and composition trajectories in midlife women: the study of women's health across the nation 1999-2018

BACKGROUND/OBJECTIVES

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been suggested as obesogens but epidemiologic evidence is limited. We examined associations of serum PFAS concentrations with longitudinal trajectories of weight, waist circumference (WC), fat mass, and proportion fat in midlife women.

SUBJECTS/METHODS

This study included 1,381 midlife women, with a total of 15,000 repeated measures from the multi-racial/ethnic Study of Women's Health Across the Nation between 1999 and 2018. The average follow-up was 14.9 (range: 0-18.6) years. Body size (objectively measured weight and WC) and body composition from dual-energy X-ray absorptiometry were assessed at near-annual visits. Linear mixed models with piecewise linear splines were utilized to model non-linear trajectories of body size and composition.

RESULTS

After multivariable adjustment, PFAS concentrations were positively associated with weight, WC, fat mass, and proportion fat at baseline and during follow-up. Comparing the highest to the lowest tertiles of PFAS concentrations, adjusted geometric mean weight was 73.9 kg vs. 69.6 kg for PFOS (P < 0.0001), and 74.0 vs. 69.4 kg for linear PFOA (P < 0.0001) at baseline. Women with the highest tertile of PFOS had an annual increase rate of 0.33% (95% CI: 0.27%, 0.40%) in weight, compared to the lowest tertile with 0.10% (95% CI: 0.04%, 0.17%) (P < 0.0001). PFOS was also significantly related to higher increase rates in WC (difference = 0.12% per year, P = 0.002) and fat mass (difference = 0.25% per year, P = 0.0002). EtFOSAA and MeFOSAA showed similar effects to PFOS. Although PFHxS was not related to body size or fat at baseline, PFHxS was significantly associated with accelerated increases in weight (P < 0.0001), WC (P = 0.003), fat mass (P < 0.0001), and proportion fat (P = 0.0009). No significant results were found for PFNA.

CONCLUSIONS

Certain PFAS were positively associated with greater body size and body fat, and higher rates of change over time. PFAS may be an underappreciated contributing factor to obesity risk.

Changing incidence and projections of thyroid cancer in mainland China, 1983-2032: evidence from Cancer Incidence in Five Continents

PURPOSE

An increasing incidence of thyroid cancer has been seen in China during the past several decades. The aim of this study was to analyze potential age, period, and cohort effects on the incidence of thyroid cancer in mainland China and to predict new cases up to 2032.

METHODS

We calculated age-adjusted and age-specific incidence rates of thyroid cancer, conducted an age-period-cohort analysis of 35,037 thyroid cancer incidence cases reported to Cancer Incidence in Five Continents from 1983 to 2012 in mainland China, and predicted incidence up to 2032 using the Bayesian age-period-cohort method.

RESULTS

The age-adjusted overall incidence rate of thyroid cancer increased from 1.93/100,000 in 1983-1987 to 12.18/100,000 in 2008-2012 among females and from 0.77/100,000 in 1983-1987 to 3.89/100,000 in 2008-2012 among males, with a female-to-male ratio of approximately 3.0 during the three decades. Strong birth cohort and period effects on the incidence of thyroid cancer were observed for both sexes, and such an increasing trend is predicted to continue for at least the next 20 years. More than 3.7 million new cases are projected in the 2028-2032 period.

CONCLUSION

The increasing trend of thyroid cancer in mainland China will cause a great burden in the future. In addition to the potential impact of improvement in medical diagnostics, potential exposure to risk factors have played a role in the observed rising trend. Further population-based epidemiologic studies are required to identify risk factors to aid in thyroid cancer prevention and control.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Umbilical cord serum perfluoroalkyl substance mixtures in relation to thyroid function of newborns: Findings from Sheyang Mini Birth Cohort Study

BACKGROUND

The epidemiological evidence on the associations between prenatal exposure to perfluoroalkyl substances (PFAS) and thyroid hormones in newborns was inconclusive.

OBJECTIVES

We aimed to estimate associations of fetal exposure to PFAS individually and in mixtures with thyroid function of newborns.

METHODS

A total of 490 mother-newborn pairs were included from Sheyang Mini Birth Cohort Study (SMBCS), a prospective cohort that recruited between June 2009 and January 2010. 12 PFAS and 7 thyroid function indicators were quantified in umbilical cord serum. We examined associations of prenatal exposure to individual and a mixture of PFAS with thyroid function indicators using multivariable linear regression and weighted quantile sum (WQS) regression models with adjustment for potential confounders, respectively.

RESULTS

Higher cord serum concentrations of PFAS mixtures were related to increases in TT4 and FT4 levels, and reductions in TSH concentrations of newborns. Combining single-chemical models with multiple-chemical models, PFOS, PFNA and PFUnDA were associated with increased TT4 levels with contributing to the mixture effects of 46.4%, 22.8%, and 16.7%, respectively. PFOS exposure was in positive association with cord serum FT4 concentrations and contributed 28.9% to the joint effects of mixtures. PFNA and PFHpA were the most important contributors to the decreases of TSH levels of newborns with 46.3% and 45.0% among the mixtures, respectively.

CONCLUSIONS

The current findings indicated the thyroid disruption of individual PFAS and their mixtures in cord serum. Additional studies are warranted to explore the underlying biological mechanisms, particularly for PFAS mixtures.