Negative associations between PBDE levels and thyroid hormones in cord blood

Detrimental consequences of micropolymers associated plasticizers on endocrinal disruption

The prevalence of polymer usage in everyday activities has emerged as a detriment to both human life and the environment. A large number of studies describe severe impacts of micropolymers (MP) and nanopolymers (NP) on various organ systems, including the endocrine system. Additionally, plasticizers utilized as additives have been identified as endocrine-disrupting chemicals (EDCs). MP/NP, along with associated plasticizers, affect principal signalling pathways of endocrine glands such as the pituitary, thyroid, adrenal, and gonads, thereby disrupting hormone function and metabolic processes crucial for maintaining homeostasis, fertility, neural development, and fetal growth. This review delves into the sources, distribution, and effects of micropolymers, nanopolymers, and associated plasticizers acting as EDCs. Furthermore, it provides a detailed review of the mechanisms underlying endocrine disruption in relation to different types of MP/NP.

A Review of the Association between Exposure to Flame Retardants and Thyroid Function

Flame retardants have been shown to cause widespread physiological effects, in particular on endocrine organs such as the thyroid. This review aims to provide an overview of the literature on the association between flame retardants and thyroid function within humans. A search in the National Library of Medicine and National Institutes of Health PubMed database through January 2024 yielded 61 studies that met the inclusion criteria. The most frequently analyzed flame retardants across all thyroid hormones were polybrominated diphenyl ethers (PBDEs), in particular BDE-47 and BDE-99. Ten studies demonstrated exclusively positive associations between flame retardants and thyroid stimulating hormone (TSH). Six studies demonstrated exclusively negative associations between flame retardants and TSH. Twelve studies demonstrated exclusively positive associations for total triiodothyronine (tT3) and total thyroxine (tT4). Five and eight studies demonstrated exclusively negative associations between flame retardants and these same thyroid hormones, respectively. The effect of flame retardants on thyroid hormones is heterogeneous; however, the long-term impact warrants further investigation. Vulnerable populations, including indigenous people, individuals working at e-waste sites, firefighters, and individuals within certain age groups, such as children and elderly, are especially critical to be informed of risk of exposure.

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

Polybrominated diphenyl ether (PBDE) exposure and adverse maternal and infant health outcomes: Systematic review

Polybrominated diphenyl ethers (PBDEs) are flame retardants found in ambient environment and are measured in humans. There are reports on general PBDE toxicity, including endocrine disrupting properties. Studies on adverse maternal and infant outcomes and underlying toxicity mechanisms needs to be understood. The objective of this study was to conduct a systematic review to examine the state of science on the relationship between PBDE and adverse maternal/infant health outcomes and related maternal biomarker changes. This literature review was conducted using PubMed, Scopus, Embase and Web of Science for published articles from January 2005-February 2022. Article quality was assessed using Newcastle-Ottawa Scale. Of the 1518 articles, only 54 human observational studies were screened in for this review. A second reviewer examined the validity of these articles. Reports on associations between PBDE and maternal health outcomes included gestational hypertension/preeclampsia (N = 2) and gestational diabetes mellitus/glycemic index (N = 6). Meanwhile, reports on PBDE and infant outcomes (N=32) included effects on infant birth weight, birth length and cephalic perimeter, preterm birth, fetal growth restriction and APGAR scores. Although findings on PBDE exposure and adverse infant outcomes showed inconsistencies across studies, in general, negative correlations between maternal PBDEs and infant birth weight, birth length and cephalic perimeter were seen, in few cases, after stratification by sex. Association between maternal PBDE and maternal biomarkers (N=18) suggested negative impact of PBDE exposure on markers relevant to neuro-endocrine system and inflammatory processes. The review findings identified potential associations between maternal PBDE and adverse maternal/infant health outcomes. Furthermore, PBDE-related biomarker changes suggest disturbances in maternal mechanisms relevant to endocrine disrupting properties of PBDEs. The observed study heterogeneity can be attributed to factors namely, sample size, study design and statistical analysis. Overall review findings imply the necessity for further research to validate PBDE exposure-related adverse maternal/infant health effects and to validate underlying toxicity mechanisms.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants used in plastics, textiles, polyurethane foam, and other materials. They contain two halogenated aromatic rings bonded by an ester bond and are classified according to the number and position of bromine atoms. Due to their widespread use, PBDEs have been detected in soil, air, water, dust, and animal tissues. Besides, PBDEs have been found in various tissues, including liver, kidney, adipose, brain, breast milk and plasma. The continued accumulation of PBDEs has raised concerns about their potential toxicity, including hepatotoxicity, kidney toxicity, gut toxicity, thyroid toxicity, embryotoxicity, reproductive toxicity, neurotoxicity, and immunotoxicity. Previous studies have suggested that there may be various mechanisms contributing to PBDEs toxicity. The present study aimed to outline PBDEs' toxic effects and mechanisms on different organ systems. Given PBDEs' bioaccumulation and adverse impacts on human health and other living organisms, we summarize PBDEs' effects and potential toxicity mechanisms and tend to broaden the horizons to facilitate the design of new prevention strategies for PBDEs-induced toxicity.

Associations between prenatal exposure to polycyclic aromatic hydrocarbons and thyroid hormones in umbilical cord blood

We explored the association between maternal urinary polycyclic aromatic hydrocarbon (PAH) metabolites and thyroid hormones in umbilical cord blood in 120 pairs of pregnant women and newborns. Maternal urinary PAH metabolites were measured using high-performance liquid chromatography with tandem mass spectrometry. Thyroid hormones were measured using a flow fluorescence assay. The dose-response relationship between PAH metabolites and thyroid hormones was analyzed using the generalized linear model and restricted cubic spline model. Results showed that ƩOH PAHs in maternal urine had a negative effect on triiodothyronine (T3). Associations between maternal urinary PAH metabolites and thyroid hormones in umbilical cord blood plasma were observed. Prenatal exposure to PAHs could affect neonatal thyroid hormones, thereby disrupting neonatal thyroid function.

The associations between concentrations of gestational bisphenol analogues and thyroid related hormones in cord blood: A prospective cohort study

Animal studies indicated that Bisphenol analogues (BPs) exhibited potential thyroid toxicity. However, little is known of the associations between maternal BPs exposure and offspring's thyroid related hormones in humans. On the basis of Shanghai-Minhang Birth Cohort study, we analyzed BPs in maternal urine collected at the third trimester of pregnancy. Thyroid related hormones (THs), including total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were measured in cord blood samples. We performed multiple linear regression and Bayesian kernel machine regression (BKMR) models to explore the single and joint effects of gestational BPs exposure on thyroid related hormones in cord blood among 258 mother-child pairs. Statistically significant inverse associations of categorized BPA with FT3 and TT4 concentrations were observed. We also found a significant association between the mixture of BPs in maternal urine and increased concentration of TT3 in cord blood and a marginally significant association between BPs mixture and increased FT3 concentrations. Further associations of BPA with lower TT4/FT4 and of Bisphenol AF (BPAF) with higher TT3/FT3 were also suggestive, by BKMR model, when other BPs were fixed at 25th percentiles. It was concluded that prenatal BPs exposure was associated with THs in cord blood. Exposure to BPA and BPAF might have large contributions to the effects on thyroid function than other bisphenols.

An Analysis of the Structural Relationship between Thyroid Hormone-Signaling Disruption and Polybrominated Diphenyl Ethers: Potential Implications for Male Infertility

Polybrominated diphenyl ethers (PBDEs) are a common class of anthropogenic organobromine chemicals with fire-retardant properties and are extensively used in consumer products, such as electrical and electronic equipment, furniture, textiles, and foams. Due to their extensive use, PBDEs have wide eco-chemical dissemination and tend to bioaccumulate in wildlife and humans with many potential adverse health effects in humans, such as neurodevelopmental deficits, cancer, thyroid hormone disruption, dysfunction of reproductive system, and infertility. Many PBDEs have been listed as chemicals of international concern under the Stockholm Convention on Persistent Organic Pollutants. In this study, the aim was to investigate the structural interactions of PBDEs against thyroid hormone receptor (TRα) with potential implications in reproductive function. Structural binding of four PBDEs, i.e., BDE-28, BDE-100, BDE-153 and BDE-154 was investigated against the ligand binding pocket of TRα using Schrodinger's induced fit docking, followed by molecular interaction analysis and the binding energy estimation. The results indicated the stable and tight binding of all four PDBE ligands and similarity in the binding interaction pattern to that of TRα native ligand, triiodothyronine (T3). The estimated binding energy value for BDE-153 was the highest among four PBDEs and was more than that of T3. This was followed by BDE-154, which is approximately the same as that of TRα native ligand, T3. Furthermore, the value estimated for BDE-28 was the lowest; however, the binding energy value for BDE-100 was more than BDE-28 and close to that of TRα native ligand, T3. In conclusion, the results of our study suggested the thyroid signaling disruption potential of indicated ligands according to their binding energy order, which can possibly lead to disruption of reproductive function and infertility.

Windows of sensitivity to toxic chemicals in the development of the endocrine system: an analysis of ATSDR's toxicological profile database

This review utilizes the robust database of literature contained in toxicological profiles developed by the Agency for Toxic Substances and Disease Registry. The aim was to use this database to identify developmental toxicity studies reporting alterations in hormone levels in the developing fetus and offspring and identify windows of sensitivity. We identified 74 oral exposure studies in rats that provided relevant information on 30 chemicals from 21 profiles. Most studies located provided information on thyroid hormones, with fewer studies on anterior pituitary, adrenal medulla, ovaries, and testes. No studies pertaining to hormones of the posterior pituitary, pancreas, or adrenal cortex were located. The results demonstrate that development of the endocrine system may be affected by exposure to environmental contaminants at many different points, including gestational and/or lactational exposure. Moreover, this review demonstrates the need for more developmental toxicity studies focused on the endocrine system and specifically alterations in hormone levels.

Structural binding perspectives of common plasticizers and a flame retardant, BDE-153, against thyroxine-binding globulin: potential for endocrine disruption

The human exposure to diverse endocrine-disrupting chemicals (EDCs) has increased dramatically over several decades with very adverse health effects. Plasticizers and flame retardants constitute important classes of EDCs interfering in endocrine physiology including the thyroid function. Thyroxine (T4) is an important hormone regulating metabolism and playing key roles in developmental processes. In this study, six phthalate and nonphthalate plasticizers and one flame retardant (BDE-153) were subjected to structural binding against thyroxine-binding globulin (TBG). The aim was to understand their potential role in thyroid dysfunction using structural binding approach. The structural study was performed using Schrodinger's induced fit docking, followed by binding energy estimations of ligands and the molecular interaction analysis between the ligands and the amino acid residues in the TBG ligand-binding pocket. The results indicated that all the compounds packed tightly into the TBG ligand-binding pocket with similar binding pattern to that of TBG native ligand, T4. A high majority of TBG interacting amino acid residues for ligands showed commonality with native ligand, T4. The estimated binding energy values were highest for BDE-153 followed by nonphthalate plasticizer, DINCH, with values comparable with native ligand, T4. The estimated binding energy values of other plasticizers DEHP, DEHT, DEHA, ATBC, and TOTM were less than DINCH. In conclusion, the tight docking conformations, amino acid interactions, and binding energy values of the most of the indicated ligands were comparable with TBG native ligand, T4, suggesting their potential for thyroid dysfunction. The results revealed highest potential thyroid disruptive action for BDE-153 and DINCH.

Analysis of Polybrominated Diphenyl Ethers and Lipid Composition in Human Breast Milk and Their Correlation with Infant Neurodevelopment

Breastfeeding is recommended over formula feeding, but human breast milk (HBM) composition varies and can be affected by food additives. Whether flame-retardant polybrominated diphenyl ethers (PBDEs) found in HBM interact with lipid components of HBM to impede infant neurodevelopment is a critical public health issue. Using lipidomic analysis, we examined the association of PBDEs in HBM and HBM lipid components with infant neurodevelopment. HBM samples (n = 100) were collected at the beginning stage of breastfeeding and analyzed for 30 PBDE congeners as well as a group of lipid components by using high-resolution gas chromatography, mass spectrometry, and liquid chromatography time-of-flight mass spectrometry. Infants were examined at 8 to 12 months of age by using the Bayley-III to assess neurodevelopment. A total of seven PBDEs, 35 lipids, and 27 fatty acids in HBM showed significant associations with Bayley-III scores. Multivariate analysis confirmed that these candidate PBDEs and lipid components were significant predictors of infant neurodevelopment. Eicosapentaenoic acid and docosapentaenoic acid in HBM showed no association with infant neurodevelopment in the general Taiwanese population. While certain PBDEs may play a role, our findings indicate that the lipid components of HBM are directly important for infant neurodevelopment.

Determination of organic pollutants in meconium and its relationship with fetal growth. Case control study in Northwestern Spain

OBJECTIVES

Antenatal exposure to organic pollutants is a leading public health problem. Meconium is a unique matrix to perform prenatal studies because it enables us to retrospectively evaluate fetal exposure accumulated during the second and third trimester. The aim of the present study was to evaluate associations between organic pollutant levels in meconium and birth weight in NW Spain.

METHODS

In this study, we quantify the concentrations of 50 organic pollutants together with the total values of the most important chemical groups in meconium using gas chromatography coupled to tandem mass spectrometry.

RESULTS

Organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers were detected with the highest levels in meconium from small for gestational age newborns. It was estimated that several congeners were statistically significant (p<0.05). However, organophosphorus pesticides attained higher concentrations in newborns with an appropriate weight.

CONCLUSIONS

The occurrence of transplacental transfer can be confirmed. Prenatal exposure to organic pollutants was associated with a decrease in birth weight and, therefore, organic pollutants could have an impact on fetal growth. Nevertheless, these results need validation in larger sample sized studies.

Effects of prenatal exposure to polybrominated diphenyl ethers (PBDEs) on the second to fourth digit ratio in children aged 4 years

BACKGROUND

The second to fourth digit ratio (2D:4D) is assumed to be a biomarker of prenatal sex steroid exposure, correlating negatively with prenatal testosterone and positively with prenatal estrogen. The ratio has been suggested to be influenced by endocrine disrupting chemicals (EDCs). However, evidence regarding effects of prenatal exposure to polybrominated diphenyl ethers (PBDEs) on 2D:4D of children was sparse.

OBJECTIVES

We investigated the associations between prenatal exposure to PBDEs and 2D:4D of children aged 4 years.

METHODS

Participants were mother-child pairs from the Shanghai-Minhang Birth Cohort Study (S-MBCS) which enrolled pregnant women at 12-16 weeks of gestation from April to December 2012. Nine PBDE congeners in venous umbilical cord plasma of 340 children were measured. Digit lengths were measured using a vernier caliper in children aged 4 years and 2D:4D for left and right hands and average 2D:4D value of both hands were calculated. A total of 281 children (160 boys and 121 girls) who had data on both 2D:4D and PBDE concentrations were included in the final analysis. Associations between prenatal PBDE exposures and 2D:4D were investigated using multiple linear regression models.

RESULTS

Among the nine congeners, BDE-47 had the highest detection rate of 86.12% with the highest median concentration of 0.20 ng/ml lipid. Five PBDE congeners with detection rates greater than or close to 50% (BDE-28, -47, -99, -100 and -153) and Σ₅PBDEs (the sum of them) were included in final analysis. For girls, a consistent pattern for the positive associations between prenatal PBDE exposures and 2D:4D of children was observed mainly for the left hand, where those in the highest exposure groups had higher 2D:4D compared to the lowest exposure groups (a feminizing effect), with statistically significant associations observed for BDE-47 (β = 0.0247, 95% confidence interval (CI): 0.0017, 0.0477), -100 (β = 0.0264, 95% CI: 0.0087, 0.0441) and Σ₅PBDEs (β = 0.0201, 95% CI: 0.0027, 0.0374). For boys, compared with the lowest exposure groups, statistically significantly higher (feminized) 2D:4D for both hands was observed in those with the highest exposure levels of BDE-100 (β = 0.0147, 95% CI: 0.0005, 0.0289 for the left hand; β = 0.0182, 95% CI: 0.0046, 0.0318 for the right hand) and those with the middle and the highest exposure levels of BDE-153 (middle vs. undetected, β = 0.0215, 95% CI: 0.0072, 0.0358 for the left hand; β = 0.0155, 95% CI: 0.0015, 0.0295 for the right hand; highest vs. undetected, β = 0.0162, 95% CI: 0.0017, 0.0307 for the left hand; β = 0.0152, 95% CI: 0.0011, 0.0294 for the right hand).

CONCLUSIONS

Our study provides preliminary evidence that prenatal exposure to PBDEs might be associated with higher 2D:4D in boys and girls.

Structural studies on the endocrine-disrupting role of polybrominated diphenyl ethers (PBDEs) in thyroid diseases

Polybrominated diphenyl ethers (PBDEs) are synthetic brominated flame retardants with extensive applications in daily-life consumer products. However, PBDEs have become ubiquitous environmental contaminants due to their leach-out capability. The hazardous human health effects and endocrine-disrupting activity of PBDEs have led many governmental organizations to impose ban on their manufacture, causing their gradual phase out from commercial products. However, PBDEs and their metabolites are still being detected from biological and environmental samples owing to their persistence and bioaccumulation. The PDBE metabolites in these samples are present in concentrations often higher and even with higher toxic potential than parent PBDEs. The two commonly detected environmental PBDE congeners, 2,2',4,4'-tetra-bromodiphenyl ether (BDE-47) and 2,2',4,4',5-penta-bromodiphenyl ether (BDE-99), and their HO- and MeO- metabolites were considered in this study for their potential disrupting activity on thyroid hormone transport. Specifically, the study involved structural binding characterization of BDE-47 and BDE-99 including their two HO- and two MeO- metabolites with thyroxine-binding globulin (TBG), which is the main thyroid hormone transport protein in blood. The results showed that the binding pattern and molecular interactions of above two PBDEs and their metabolites exhibited overall similarity to native ligand, thyroxine in dock score, binding energy, and amino acid interactions with TBG. The BDE-99 and its metabolites were predicted to have stronger binding to TBG than BDE-47 with the metabolite 5-MeO-BDE-99 showing equal binding affinity to that of thyroxine. It is concluded that BDE-47 and BDE-99 and their metabolites have the potential to disrupt thyroid hormone transport and interfere in thyroid function.

Prenatal exposure levels of polybrominated diphenyl ethers in mother-infant pairs and their transplacental transfer characteristics in Uganda (East Africa)

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants with adverse effects on the foetus and infants. This study aimed at assessing in utero exposure levels and transplacental transfer (TPT) characteristics of BDE congeners in primiparous mothers from Kampala, the capital city of Uganda. Paired human samples (30 placenta and 30 cord blood samples) were collected between April and June 2018; and analysed for a suite of 24 tri-to deca-BDE congeners. Extraction was carried out using liquid-liquid extraction and sonication for cord blood and placenta samples, respectively. Clean-up was done on a solid phase (SPE) column and analysis was performed using gas chromatography/mass spectrometry (GC/MS). Total (∑) PBDEs were 0.25-30.9 ng/g lipid weight (lw) (median; 7.11 ng/g lw) in placental tissues and 1.65-34.5 ng/g lw (median; 11.9 ng/g lw) in cord blood serum, with a mean difference of 1.26 ng/g lw between the compartments. Statistical analysis showed no significant difference between the levels of PBDEs in cord blood and placenta samples (Wilcoxon signed rank test, p = 0.665), possibly because foetus and neonates have poorly developed systems to metabolise the pollutants from the mothers. BDE-209 was the dominant congener in both matrices (contributed 40.5% and 51.2% to ∑PBDEs in placenta and cord blood, respectively), suggesting recent and on-going maternal exposure to deca-BDE formulation. Non-significant associations were observed between ∑PBDEs in maternal placenta and maternal age, household income, pre-pregnancy body mass index (BMI), and beef/fish consumption. This suggested on-going exposure to PBDEs through multiple sources such as dust from indoor/outdoor environments and, ingestion of other foods. Based on absolute concentrations, the extent of transplacental transport was greater for higher congeners (BDE-209, -206 and -207) than for lower ones (such as BDE-47), suggesting alternative TPT mechanisms besides passive diffusion. More studies with bigger sample sizes are required to confirm these findings.

Persistent Organic Pollutants in Human Breast Milk and Associations with Maternal Thyroid Hormone Homeostasis

Epidemiological studies have indicated the thyroid-disrupting effects of persistent organic pollutants (POPs). However, the association of low-exposure POPs with thyroid hormones (THs) remains unclear. Here, we aim to assess the association of low exposure of POPs, including polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polybrominated dibenzo-p-dioxins and furans, with THs [total _L-thyroxine (TT₄), total 3,3',5-triiodo-_L-thyronine (TT₃), and total 3,3',5'-triiodo-_L-thyronine (TrT₃)] measured in human breast milk. Ninety-nine breast milk samples were collected from the LUPE cohort (2015-2016, Bavaria, Germany). Fourteen PBDEs, 17 PCBs, and 5 PCDD/Fs had quantification rates of >80%. Nonmonotonic associations were observed. In adjusted single-pollutant models, (1) TT₄ was inversely associated with BDE-99, -154, and -196; (2) TT₃ was inversely associated with BDE-47, -99, -100, -197, -203, -207, and OCDD; and (3) TrT₃ was inversely associated with BDE-47, -99, -183, and -203. Multipollutant analysis using principal component analysis and hierarchical clustering revealed inverse associations of PBDEs (BDE-28, -47, -99, -100, -154, -183, and -197) with TT₄ and TrT₃. These results indicate that POPs at low levels might be related to reduced THs. This study shows that human breast milk might be an appropriate specimen to evaluate the thyroid disruption of POPs.

Gestational Exposure to Common Endocrine Disrupting Chemicals and Their Impact on Neurodevelopment and Behavior

Endocrine disrupting chemicals are common in our environment and act on hormone systems and signaling pathways to alter physiological homeostasis. Gestational exposure can disrupt developmental programs, permanently altering tissues with impacts lasting into adulthood. The brain is a critical target for developmental endocrine disruption, resulting in altered neuroendocrine control of hormonal signaling, altered neurotransmitter control of nervous system function, and fundamental changes in behaviors such as learning, memory, and social interactions. Human cohort studies reveal correlations between maternal/fetal exposure to endocrine disruptors and incidence of neurodevelopmental disorders. Here, we summarize the major literature findings of endocrine disruption of neurodevelopment and concomitant changes in behavior by four major endocrine disruptor classes:bisphenol A, polychlorinated biphenyls, organophosphates, and polybrominated diphenyl ethers. We specifically review studies of gestational and/or lactational exposure to understand the effects of early life exposure to these compounds and summarize animal studies that help explain human correlative data.

Associations of prenatal exposures to low levels of Polybrominated Diphenyl Ether (PBDE) with thyroid hormones in cord plasma and neurobehavioral development in children at 2 and 4 years

BACKGROUND

Neurotoxic effects of Polybrominated Diphenyl Ethers (PBDEs) at low levels have not been well studied in human population, and whether the associations can be explained by thyroid hormones (THs) remains unclear.

OBJECTIVES

We examined the associations of prenatal PBDE exposures with THs in cord plasma and neurobehavior of children at 2 and 4 years among general population in China.

METHODS

Participants were mother-child pairs in the Shanghai-Minhang Birth Cohort Study. Nine PBDE congeners and THs (thyroid stimulating hormone, total thyroxine, free thyroxine, total triiodothyronine, and free triiodothyronine) were determined in cord plasma. Child Behavior Checklist (CBCL/1.5-5) were completed by caregivers to assess children's neurobehavioral development at 2 and 4 years. In the final analyses, 199 and 307 mother-child pairs at 2 and 4 years were included to examine associations of PBDEs with CBCL scores using Pearson-scale-adjusted Poisson regressions, and 339 subjects were included in linear regression models to investigate the associations between PBDEs and THs.

RESULTS

BDE-47 had the highest detection rate of 83.82% with the median concentration of 0.19 ng/g lipid, followed by BDE-28, -99, -100 and -153 with detection rates nearly 50%. We found positive associations between prenatal PBDE concentrations and children's neurobehavior, including Somatic Complaints, Withdrawn, Sleep Problems and Internalizing Problems in girls, and Somatic Complaints and Attention Problems in boys. We also observed inverse associations of the sum of BDE-47, -28, -99, -100 and -153 with THs. However, by adding THs to the models examining associations between PBDEs and CBCL, the main results didn't measurably change.

CONCLUSIONS

This study adds new knowledge that prenatal PBDEs at low levels may be related to long-lasting behavioral abnormalities in children and reduced THs in cord plasma. However, the hypothesis that the neurotoxic impact of PBDEs may be explained by alterations in cord THs was not supported.

Residue Levels of Organochlorine Pesticides in Breast Milk and Its Associations with Cord Blood Thyroid Hormones and the Offspring's Neurodevelopment

Previous studies have demonstrated that organochlorine pesticide (OCP) exposure has a negative impact on the neurological function of infants. Only a few reports have investigated the thyroid and growth hormones and their relationship to neurodevelopment after human exposure to OCPs, especially in the case of infants. Our goal was to determine whether breastmilk OCP residues were associated with negative impacts and/or alterations in the neurodevelopment of infants among specific southern Taiwanese mother–breastfed infant pairs. Our subjects (n = 55 pairs) were recruited from southern Taiwan between 2007 and 2010. The thyroid and growth hormone levels in the cord blood samples collected after childbirth were determined. The breastmilk was gathered within one month after childbirth for the determination of OCP levels using a high-resolution gas chromatograph with mass spectrometry, and the neurodevelopment of 10–12-month-old infants was examined using the Bayley Scales of Infant and Toddler Development^®, Third Edition (Bayley-III). It was observed that 4,4′-dichlorodiphenyl-dichloroethylene (4,4′-DDE) (mean = 10.3 ng/g lipid) was the most predominant OCP compound in the breastmilk samples. At higher concentrations (>75th percentile), specific OCPs were associated with significantly lower levels of thyroid and growth hormones than at lower concentrations (<75th percentile). Significantly higher odds ratios (ORs) were observed for binary cognitive (OR = 8.09, p = 0.025 for 4,4′-DDT), language (OR = 11.9, p = 0.013 for 4,4′-DDT) and social–emotional (OR = 6.06, p = 0.01 for trans-CHL) composite scores for specific OCPs belonging to the lower exposure group as compared to the higher OCP exposure group. The five domain Bayley-III infant neurodevelopment outcomes were negatively associated with specific OCPs in the breast milk samples based on the redundancy analysis (RDA) test. Bayley-III scales, which include cognitive, language, motor, social-emotional, and adaptive behavior scales, could be predicted by 4,4′-DDT, endrin, endosulfan I, heptachlor, or heptachlor epoxide using multivariate linear regression models with adjustment for maternal age, pre-pregnant BMI, parity, and infant gender. In conclusion, although our study showed that postnatal exposure to breast milk OCPs may be associated with infant neurodevelopmental outcomes and that prenatal exposure, if extrapolated from breastmilk levels, is associated with changes in thyroid and growth hormones that may have effects on neurodevelopment, these associations are only suggestive; thus, further studies are recommended for confirmation.

Prenatal polybrominated diphenyl ethers exposure and anogenital distance in boys from a Shanghai birth cohort

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are major brominated flame retardant (BFR) chemicals with endocrine-disrupting properties. One small-scale study on humans has suggested that prenatal exposure to PBDEs is adversely related to anogenital distance (AGD) a sensitive marker for prenatal androgen exposure. The aim of the present study was to examine the associations between prenatal exposure to PBDEs and AGD among boys 0-4 years of age in a cohort study.

METHODS

In the Shanghai-Minhang Birth Cohort Study (S-MBCS), nine PBDE congeners were measured in cord plasma of 192 male infants. We measured anopenile distance (AGD_AP) and anoscrotal distance (AGD_AS) at birth, 6 months, 12 months, and 48 months of age. A total of 190 boys with neonatal concentrations of PBDEs (ng/g lipid) who had at-least one AGD measurement were included in our study. Information on potential confounding variables were collected through in-person interviews. Multiple linear regression models and generalized estimating equation (GEE) models were used to evaluate the associations between prenatal PBDEs concentrations and AGD.

RESULTS

Among the nine congeners, BDE-47 had the highest detection rate (83.68%) and the highest median concentration (0.18 ng/g lipid). Boys who had neonatal concentration of BDE-47 or Σ₄PBDEs (sum of BDE-47, BDE-99, BDE-100, and BDE-153) in the higher quartile generally had shorter AGD_AP and AGD_AS than those in the first quartile. Significant inverse associations were found between AGD_AS and fourth quartile BDE-47 levels among boys 12 months and 48 months of age (β = -5.57, 95% confidence interval (CI): -9.89, -1.25 for 12 month of age; β = -4.32, 95% CI: -8.18, -0.46 for 48 month of age). Inverse associations were also observed between AGD_AS and fourth quartile Σ₄PBDEs levels among boys 12 months of age (β = -5.13, 95% CI: -9.89, -1.25). In GEE models, similar patterns of association were also observed between BDE-47 and AGD_AS.

CONCLUSIONS

Our findings provide preliminary evidence that prenatal exposure to BDE-47 and Σ₄PBDEs, even at low environmental levels, may be associated with shorter AGD in boys. This data suggest that prenatal exposure to PBDEs may have adverse effects on male reproductive development. Further studies should be conducted to validate these results.

Advanced Maternal Age, Mode of Delivery, and Thyroid Hormone Levels in Chinese Newborns

Objective: Thyroid hormones are essential for fetal growth and neurodevelopment, however, data on cord blood thyroid hormones are sparse in China where maternal age at childbearing is increasing in recent decades. We aimed to assess cord blood levels of free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) in full-term Chinese newborns, and examine potential related perinatal factors. Methods: This study included 922 mother-newborn pairs from a prospective birth cohort enrolled in 2012-2013, Shanghai, China. Cord serum concentrations of FT3, FT4, TSH, and TPOAb were measured in newborns. Results: Newborns born via cesarean section had higher cord serum FT3 (mean ± SD: 1.90 ± 1.16 pmol/L) and lower cord serum TSH (5.15 ± 2.60 mIU/L) than those born via vaginal delivery (FT3: 1.62 ± 0.93 pmol/L; TSH: 9.27 ± 6.76 mIU/L). In cesarean section deliveries, the concentration of cord serum FT3 was 0.15 (95%CI: -0.03, 0.33; p = 0.10) pmol/L lower in infants of mothers aged 30-34 years, and 0.57 (95%CI: 0.22, 0.92; p = 0.002) pmol/L lower in infants of mothers ≥35 years compared to infants of mothers <30 years. Large-for-gestational-age (birth weight >90th percentile) was associated with higher TSH (p = 0.02). Similar results were also found in vaginal deliveries. Conclusions: In this Chinese term birth cohort, newborns born via cesarean section had higher cord serum FT3 and lower TSH than those born via vaginal delivery. Advanced maternal age was associated with lower fetal FT3. Further research is needed to understand whether this association may mediate the adverse impact of advanced maternal age on neurodevelopment in early life.

Disruption of thyroid hormone levels by decabrominated diphenyl ethers (BDE-209) in occupational workers from a deca-BDE manufacturing plant

While there is some evidence that exposure to decabrominated diphenyl ethers (BDE-209) affects thyroid function, the results obtained to date have been inconsistent. No studies have been performed on workers in deca-BDE manufacturing who had a high level of exposure to BDE-209 and relatively little exposure to other contaminants. In the present study, the relationship between BDE-209 exposure and thyroid hormone in occupational workers from a deca-BDE manufacturing plant was investigated. The serum and urine levels of polybrominated diphenyl ethers (PBDEs) and serum thyroid hormones were measured in 72 workers recruited from the deca-BDE manufacturing plant. The associations between their thyroid hormone levels and their exposure to BDE-209 were examined using multiple linear regression models. Serum concentrations of BDE-209 ranged from 67.4 to 109,000 ng/g lipid weight (lw), with a median of 3420 ng/g lw, contributing to 93.1% of the total PBDEs. The concentration of BDE-209 in urine was highly correlated with that in the serum (r² = 0.440, p < 0.001), indicating that urine may be a good non-invasive biomonitoring medium of BDE-209 body burden in occupational workers. BDE-209 in the serum was significantly and positively correlated with total thyroxine (tT4, r = 0.270, p = 0.029) and marginally and positively correlated with total triiodothyronine (tT3, r = 0.232, p = 0.061) in all occupational workers after adjusting for gender, age, BMI, and occupational exposure duration. A 10-fold increase in the serum BDE-209 concentration was associated with an increase in tT4 (8.63 nmol/L) [95% confidence interval (CI): 0.930-16.3] and tT3 (0.106 nmol/L) [95% confidence interval (CI): -0.005-0.219], corresponding to the increase of 7.8% in tT4 level and 5.4% in tT3 level. Associations between urine BDE-209 levels and thyroid hormones were similar to the results for the serum levels. These findings offer new evidence for proving the thyroid disrupting effects of BDE-209, impacting the direction of hyperthyroidism.

Thyroid Function Disruptors: from nature to chemicals

The modern concept of thyroid disruptors includes man-made chemicals and bioactive compounds from food that interfere with any aspect of the hypothalamus-pituitary-thyroid axis, thyroid hormone biosynthesis and secretion, blood and transmembrane transport, metabolism and local action of thyroid hormones. This review highlights relevant disruptors that effect populations through their diet: directly from food itself (fish oil and polyunsaturated fatty acids, pepper, coffee, cinnamon and resveratrol/grapes), through vegetable cultivation (pesticides) and from containers for food storage and cooking (bisphenol A, phthalates and polybrominated diphenyl ethers). Due to the vital role of thyroid hormones during every stage of life, we review effects from the gestational period through to adulthood, including evidence from in vitro studies, rodent models, human trials and epidemiological studies.

Polybrominated diphenyl ethers in cord blood and perinatal outcomes from Laizhou Wan Birth Cohort, China

We explored whether polybrominated diphenyl ethers (PBDEs) exposed in cord blood could have any potential relationship with perinatal outcomes. Participants were pregnant females (n = 222) who were recruited from a prospective birth cohort (Laizhou Wan Birth Cohort, LWBC) between September 2010 and February 2012. We measured eight PBDE congeners (BDE-28, BDE-47, BDE-85, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) in cord serum and examined their relationship with perinatal outcomes. The median levels of BDE-28, BDE-47, BDE-85, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183 were 2.92, 3.93, 2.29, 7.03, 3.03, 3.14, 1.46, and 2.55 ng/g lipids, respectively. For each log unit increase in BDE-47, BDE-100, and ∑₄PBDEs, gestational age increased by 0.70 weeks (95% confidence interval [CI] 0.25, 1.15), 0.48 weeks (95% CI 0.03, 0.94), and 0.73 weeks (95% CI 0.12, 1.34), respectively. We also found that BDE-47 was positively associated with head circumference (β = 0.42, 95% CI 0.00, 0.84). Given that our study area is one of the major brominated flame retardant production areas in China, and the cord PBDEs levels were relatively higher than those reported in most other Asian areas, more studies on the effects of in utero PBDE exposure on fetal growth and child development are warranted.

Prenatal contribution of 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) to total body burden in young children

Many scientists made estimates of the body burden of PBDEs from breastmilk and house dust. Interestingly, they have not included the prenatal contribution to the body burden in young children after birth. In order to address how the prenatal contribution is important in the risk assessment of PBDEs in infants up to five years old, we used the median measurements of BDE-47 as a model chemical in 108 neonates in Korea, and made simulations of its disposition out of body from birth to five years. During the simulation periods, the environmental exposure was considered for house dust, babyfood, breastmilk consumption, etc., with assumption of typical exposure scenario applicable to general infants in Korea. About 22% of the total amounts of BDE-47 in newborn remained up to 5years after birth. The relative amounts of BDE-47 from the prenatal source were 20%, 14%, 10%, 8%, 6%, and 4% of the total body burden for 1-, 2-, 3-, 4- and 5-year after birth, respectively. The contribution from breastfeeding was 95.2% and 92.2% of the total postnatal exposure amounts at 6-month and 1-year after birth, respectively. After cease of breastfeeding at 1-yr, house dust and food were the important sources of exposure up to 5-yr; however, their contributions to the bodyburden were negligible with consideration of the remaining amounts of the analytes from the breastmilk and prenatal exposure. Suggestively, the innate amounts and pharmacokinetics should be counted in estimating bodyburden of BDE-47.

Associations between serum polybrominated diphenyl ethers and thyroid hormones in a cross sectional study of a remote Alaska Native population

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants. Arctic indigenous peoples are exposed to PBDEs through a traditional diet high in marine mammals. PBDEs disrupt thyroid homeostasis. The aim of this study was to assess the relationship between serum PBDEs and thyroid function in a remote population of St. Lawrence Island Yupik. Serum samples were collected from 85 individuals from St. Lawrence Island, Alaska and measured for concentrations of PBDEs, free and total thyroxine (T4), free and total triiodothyronine (T3), and thyroid stimulating hormone (TSH). The relationships between PBDEs and thyroid hormones were assessed using multiple linear regression fit with generalized estimating equations. Serum concentrations of several Penta-BDE congeners (BDE-28/33, 47, and 100) were positively associated with concentrations of TSH and free T3, while serum concentration of BDE-153 was negatively associated with total T3 concentrations. Both BDE-47 and 153 remained significantly associated with thyroid hormones when BDE-47, BDE-153, and BDE-209 were covariates in the same model. There were no significant relationships between serum concentrations of PBDEs and either free or total T4. Individual PBDEs are associated with thyroid hormones in serum from a remote population of Alaska Natives, and directions of effect differ by congener.

A flexible plasma-treated silver-nanowire electrode for organic light-emitting devices

Silver nanowires (AgNWs) are a promising candidate to replace indium tin oxide (ITO) as transparent electrode material. However, the loose contact at the junction of the AgNWs and residual surfactant polyvinylpyrrolidone (PVP) increase the sheet resistance of the AgNWs. In this paper, an argon (Ar) plasma treatment method is applied to pristine AgNWs to remove the PVP layer and enhance the contact between AgNWs. By adjusting the processing time, we obtained AgNWs with a sheet resistance of 7.2Ω/□ and a transmittance of 78% at 550 nm. To reduce the surface roughness of the AgNWs, a peel-off process was used to transfer the AgNWs to a flexible NOA63 substrate. Then, an OLED was fabricated with the plasma-treated AgNWs electrode as anode. The highest brightness (27000 cd/m²) and current efficiency (11.8 cd/A) was achieved with a 30 nm thick light emitting layer of tris-(8-hydroxyquinoline) aluminum doped with 1% 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5 H,11H-(1)-benzopyropyrano(6,7-8-I,j)quinolizin-11-one. Compared to thermal annealing, the plasma-treated AgNW film has a lower sheet resistance, a shorter processing time, and a better hole-injection. Our results indicate that plasma treatment is an effective and efficient method to enhance the conductivity of AgNW films, and the plasma-treated AgNW electrode is suitable to manufacture flexible organic optoelectronic devices.

Polybrominated diphenyl ethers (PBDEs) and thyroid hormones in cord blood

Human exposure to polybrominated diphenyl ethers (PBDEs) has been increasing over the last three decades in China and around the world. Animal studies suggest that PBDEs could reduce blood levels of thyroid hormones, but it is unclear whether PBDEs disrupt thyroid function in humans. We used data from a prospective birth cohort of 123 pregnant women who were enrolled between September 2010 and March 2011 in Shandong, China. We measured the concentrations of eight PBDE congeners (n = 106) and five thyroid hormones (n = 107) in cord serum samples. We examined the relationship between prenatal exposure to PBDEs and thyroid function (n = 90). Median concentrations of BDEs 47, 99, 100, and 153 (detection frequencies > 75%) were 3.96, 8.27, 3.31, and 1.89 ng/g lipid, respectively. A 10-fold increase in BDE-99 and Σ₄ PBDEs (the sum of BDEs 47, 99, 100, and 153) concentrations was associated with a 0.41 μg/dL (95% confidence interval [CI]: 0.10 to 0.72) and 0.37 μg/dL (95% CI: 0.06 to 0.68) increase in total thyroxine levels (TT₄), respectively. No associations were found between other individual congeners and any of the five thyroid hormones. Our study suggests that prenatal exposure to PBDEs may be associated with higher TT₄ in cord blood. Given the inconsistent findings across existing studies, our results need to be confirmed in additional studies.

Thyroid-stimulating hormone levels in newborns and early life exposure to endocrine-disrupting chemicals: analysis of three European mother-child cohorts

BackgroundVarious studies have reported interactions between thyroid hormones and early life chemical exposure. Our objective was to analyze the associations between markers of endocrine-disrupting chemical exposure and thyroid function in newborns, determined through heel prick blood spots.MethodsThree European mother-child cohorts (FLEHSI-Belgium, HUMIS-Norway, and the PCB cohort-Slovakia. Total n=1,784) were pooled for the purpose of this study. Data on thyroid-stimulating hormone (TSH) were obtained from national neonatal screening registries, and samples of cord plasma and/or breast milk were collected to determine exposure to various chemicals. Multiple regression models were composed with exposure and cohort as fixed factors, and adjustments were made for a priori defined covariates.ResultsMedian TSH concentrations were 1, 1.10, and 2.76 mU/l for the Belgian, Norwegian, and Slovak cohorts, respectively. For polychlorinated biphenyl (PCB)-153 and dichlorodiphenyldichloroethylene (p,p'-DDE), children in the third exposure quartile had a 12-15% lower TSH at birth. Results remained unchanged after additional adjustment for birth weight and gestational weight gain. No effect on TSH was observed for the other compounds.ConclusionEarly life exposure to PCB-153 and p,p'-DDE impacts newborn TSH levels. Higher exposure levels were associated with 12-15% lower TSH levels.

Distribution of polybrominated diphenyl ethers in breast milk, cord blood and placentas: a systematic review

Polybrominated diphenyl ethers (PBDEs) have been extensively used as flame retardants in consumer products. PBDEs rapidly bioaccumulate in the environment, food, wild animals and humans. In this review, we investigated the harmful effects of PBDEs on humans, especially in early life, and summarised the levels of PBDEs in human biological samples (breast milk, cord blood and placentas). In addition, we described the spatiotemporal distribution of PBDEs in this review. PBDE levels in breast milk, cord blood and placentas were generally higher in North America than in other regions, such as Asia, Europe, Oceania and Africa. However, high levels of PBDEs in human biological samples were detected at e-waste recycling sites in South China, East China and South Korea. This finding suggests that newborns living in e-waste regions are exposed to high levels of PBDEs during prenatal and postnatal periods. The time trends of PBDE concentration differed according to the region. Few studies have investigated PBDE levels in humans from 1967 to 2000, but they increased rapidly after 2000. PBDE concentration peaked at approximately 2006 globally. Compared with other PBDE congeners, BDE-47, BDE-153 and BDE-209 were the major components, but the detection rate of BDE-209 was lower than those of others. Future studies should focus on determining the BDE-209 concentration, which requires the implementation of different analytical approaches. Additionally, the levels of PBDEs in human samples and the environment should be monitored, especially in e-waste recycling regions. Graphical abstract The figures described the spatial distribution of the lowest (Fig. a1) and highest concentration of ∑PBDE (Fig. a2) in different countries by 2006 and described the spatial distribution of the lowest (Fig. b1) and highest concentration of ∑PBDE (Fig. b2) in different countries from 2007 to 2015. All the figures indicated that the levels of PBDEs in North America were substantially higher than those in many regions of Europe, Asia, Oceania, or Africa. Comparing Fig. a1-b1 or Fig. a2-b2, increasing trends were observed in some countries, especially in some regions in China, Korea and Canada.

Polybrominated diphenyl ethers (flame retardants) in mother-infant pairs in the Southeastern U.S

Polybrominated diphenyl ethers (PBDEs) are commonly used flame retardants in foams, building material, electronics, and textiles. These chemicals leach into the environment, where they persist, and are found today in virtually every population worldwide. Several studies in recent years have detected the presence of PBDEs in maternal and infant samples. However, few of these studies were conducted in the U.S., and few examined paired or matched mother blood-cord blood samples. We analyzed serum from 10 mother-infant pairs for the presence of PBDEs in a patient population in the Southeastern U.S. Out of 35 measured PBDE congeners, five (BDE-28, -47, -99, -100, and -153) were present, with detection frequencies of 65-100 %. The total PBDE concentrations in maternal and infant sera were highly correlated (r² = 0.710, p = 0.0043). The levels of BDE-47, -99, and -100 and of total PBDEs were higher in the infant cord sera when compared with those in maternal sera (p < 0.017), suggesting that fetuses and neonates might have higher circulating concentrations of these potentially neurotoxic and endocrine disrupting chemicals compared with their mothers. The primary focus henceforward should be whether there are any deleterious effects from exposure to these chemicals on human health.

Correlation between Prenatal Exposure to Polybrominated Diphenyl Ethers (PBDEs) and Infant Birth Outcomes: A Meta-Analysis and an Experimental Study

Only a few epidemiological studies have focused on the correlation between prenatal exposure to polybrominated diphenyl ethers (PBDEs) and infant birth outcomes (IBO), and the results of these epidemiological studies are contradictory. The objective of this study was to assess the correlation between prenatal exposure to PBDEs (PEP) and IBO (i.e., birth weight) in an analysis of epidemiological studies and an experimental animals study. We searched databases of the medical literature (PubMed, Excerpta Medica Database, Cochrane Library, and China National Knowledge Infrastructure) for articles and pooled the results of the included epidemiological studies. In parallel, birth outcomes (i.e., birth weights of pups) were collected from female Sprague-Dawley (SD) rats exposed to decabromodiphenyl ether (DecaBDE) in the diet from five weeks of age to delivery. A significant negative relationship was found between human PBDE burden and birth weight in the analysis of seven epidemiological studies based on a random-effects model (β = −50.598; 95% confidence interval (CI) −95.914, −5.282; I² = 11.8%; p = 0.029). In the experimental animal study, a significant decrease in birth weight in the DecaBDE-treated group was also observed (5.26 ± 0.39 vs. 5.8 ± 0.58, p = 0.0132). The results of our study contribute to increasing evidence suggesting that PEP adversely impacts IBO, especially birth weight.

Association of prenatal and childhood PBDE exposure with timing of puberty in boys and girls

BACKGROUND

Polybrominated diphenyl ether (PBDE) flame retardants are endocrine-disrupting chemicals that exhibit estrogenic and androgenic properties and may affect pubertal timing.

METHODS

Study subjects were participants between 1999 and 2013 in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a longitudinal cohort study of predominantly Mexican origin families in Northern California. We measured serum concentrations of four PBDEs (BDE-47, -99, -100, -153) in blood collected from mothers during pregnancy (N=263) and their children at age 9years (N=522). We determined timing of pubertal onset in 309 boys and 314 girls using clinical Tanner staging every 9months between 9 and 13years of age, and timing of menarche by self-report. We used Poisson regression for relative risk (RR) of earlier puberty and parametric survival analysis for time ratios (TR) of pubertal milestones.

RESULTS

Prenatal concentrations of all 4 congeners and ƩPBDEs were associated with later menarche in girls (RR_{earlier menarche}=0.5, 95% confidence interval (CI): 0.3, 0.9 for ƩPBDEs) but earlier pubic hair development in boys (RR_{earlier pubarche}=2.0, 95% CI: 1.3, 3.3 for ƩPBDEs). No associations were seen between prenatal exposure and girls' breast or pubic hair development or boys' genital development. Childhood PBDE exposure was not associated with any measure of pubertal timing, except for an association of BDE-153 with later menarche.

CONCLUSIONS

We found that prenatal PBDE exposure was associated with later menarche in girls but earlier pubarche in boys, suggesting opposite pubertal effects in girls and boys.

Maternal body burdens of PCDD/Fs and PBDEs are associated with maternal serum levels of thyroid hormones in early pregnancy: a cross-sectional study

BACKGROUND

Thyroid hormones (THs) regulate many biological functions in the human body and are essential for normal brain development. Epidemiological studies have observed diverging associations between halogenated persistent organic pollutant (POP) exposure and concentrations of THs in pregnant women and their infants. We investigated whether background exposure to polybrominated diphenyl ethers (PBDEs) is related to TH status in a Swedish population of pregnant women and their infants. Furthermore, we examined associations between polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) and TH status in early pregnancy as an extension of an earlier study focusing on late pregnancy TH status.

METHODS

Free thyroxine (T4), total triiodo-thyronine (T3) and thyroid stimulating hormone (TSH) were analysed in serum from first-time mothers (N = 220-281) in the first and third trimester, and in infants (N = 115-150) 3 weeks and 3 months after delivery. Antibodies to thyroid peroxidase (anti-TPO) (N = 260) were measured in maternal third trimester serum. Maternal body burdens of PCBs (N = 281) were estimated from serum lipid PCB concentrations in late pregnancy, and PCDD/F (N = 97) and PBDE (N = 186) body burdens were estimated from concentrations in mother's milk lipids 3 weeks after delivery. Linear regression models allowed for covariate adjustment of the associations between ln-transformed POP body burdens and concentrations of TH and anti-TPO.

RESULTS

Maternal body burden of BDE-153 was inversely associated with first trimester total T3, otherwise no associations between PBDEs and first and second trimester THs were observed. No associations were found between maternal PBDE body burdens and infant THs. Maternal body burden of PCDD/Fs were inversely associated with first trimester total T3. No associations were observed between PCBs and first trimester THs. Third trimester anti-TPO was not associated with maternal PCBs, PCDD/Fs and PBDEs.

CONCLUSIONS

Our results suggest that maternal PCDD/F and BDE-153 body burdens influence maternal TH status in early pregnancy, which is a critical period when maternal TH status influences fetal development.

Polybrominated Diphenyl Ether Exposure and Thyroid Function Tests in North American Adults

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are flame-retardant chemicals that are added to many consumer products. Multiple animal studies have shown PBDEs to be thyroid hormone (TH) disruptors. Epidemiologic evidence of PBDE exposure associated with TH disruption has been inconclusive.

OBJECTIVES

We used repeated measures to estimate associations between serum PBDE concentrations and THs in a North American adult cohort.

METHODS

From 2010 to 2011, we collected ≤ 3 serum samples at approximately 6-month intervals from 52 healthy adult office workers from Boston, Massachusetts, for analysis of PBDE congeners and THs.

RESULTS

The geometric mean sum concentrations of the most prevalent PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, and BDE-153) were 22 ng/g lipid in winter 2010, 23 ng/g lipid in summer 2010, and 19 ng/g lipid in winter 2011. BDE-47 was the predominant congener. Based on a multivariable mixed regression model, we estimated that on average, a 1-ng/g serum increase in BDE-47 was associated with a 2.6-μg/dL decrease in total thyroxine (T4) (95% CI: -4.7, -0.35). Total T4 was inversely associated with each PBDE congener. Serum concentrations of PBDEs were not strongly associated with total triiodothyronine (T3), free T4, or thyroid-stimulating hormone (TSH).

CONCLUSION

These results are consistent with those from animal studies showing that exposure to PBDEs is associated with a decrease in serum T4. Because the other TH concentrations did not appear to be associated with BDE exposures, our findings do not indicate effects on the pituitary-thyroid axis. Taken together, our findings suggest that PBDE exposure might decrease the binding of T4 to serum T4 binding proteins.

CITATION

Makey CM, McClean MD, Braverman LE, Pearce EN, He XM, Sjödin A, Weinberg JM, Webster TF. 2016. Polybrominated diphenyl ether exposure and thyroid function tests in North American adults. Environ Health Perspect 124:420-425; http://dx.doi.org/10.1289/ehp.1509755.

Effects of PCBs and PBDEs on thyroid hormone, lymphocyte proliferation, hematology and kidney injury markers in residents of an e-waste dismantling area in Zhejiang, China

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two typical categories of contaminants released from e-waste dismantling environments. In China, the body burdens of PCBs and PBDEs are associated with abnormal thyroid hormones in populations from e-waste dismantling sites, but the results are limited and contradictory. In this study, we measured the serum levels of PCBs and PBDEs and the thyroid hormone free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in 40 residents in an e-waste dismantling area and in 15 residents in a control area. Additionally, we also measured some lymphocyte proliferation indexes, hematologic parameters and kidney injury markers, including white blood cells, neutrophils, monocytes, lymphocytes, hemoglobin, platelets, serum creatinine and beta 2-microglobulin (β2-MG). The results indicated that the mean level of ΣPCBs in the exposure group was significantly higher than that in the control group (964.39 and 67.98 ng g(-1), p<0.0001), but the mean level of ΣPBDEs in the exposure group was not significantly higher than that in the controls (139.32 vs. 75.74 ng g(-1), p>0.05). We determined that serum levels of FT3, FT4, monocytes and lymphocytes were significantly lower, whereas the levels of neutrophils, hemoglobin, platelets and serum creatinine were significantly higher in the exposed group (p<0.05). The mean level of ΣPCBs was negatively correlated with levels of FT3, FT4, monocytes and lymphocytes (p<0.05) and positively correlated with levels of neutrophils, hemoglobin, serum creatinine and β2-MG (p<0.05). Additionally, the mean level of ΣPBDEs was positively correlated with levels of white blood cells, hemoglobin and platelets (p<0.05). Our data suggest that exposure to an e-waste dismantling environment may increase the body burdens of PCBs and the specific PBDEs congeners in native residents and that the contaminants released from e-waste may contribute to abnormal changes in body levels of thyroid hormone, hematology and kidney injury markers.

Prenatal exposure to polybrominated diphenyl ethers and birth outcomes

This study aimed to examine the potential association between maternal PBDEs and birth outcomes, including birth weight (g), length (cm), head circumference (cm) and gestational age (week). 215 mothers were recruited from a prospective birth cohort in rural northern China between September 2010 and February 2012. Serum PBDE congeners were detected and their association with birth outcomes were examined. The median maternal serum concentrations of BDE-28, -47, -99, -100, -153 were 2.27, 2.26, 3.58, 2.13, 4.87 ng/g lipid, respectively. Maternal LgBDE-28 and LgBDE-100 were negatively associated with birth length (β = -0.92, 95% confidence interval (CI): -1.82, -0.02; β = -0.97, 95% CI: -1.83, -0.08). A negative association was found between LgBDE-28 and birth weight among male infants (β = -253.76, 95% CI: -438.16, -69.36). PBDE congeners were not associated with head circumference, or gestational age. Our results contribute to growing evidence suggesting that PBDEs have adverse effects on birth outcomes.

Maternal Polybrominated Diphenyl Ether (PBDE) Exposure and Thyroid Hormones in Maternal and Cord Sera: The HOME Study, Cincinnati, USA

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) reduce blood concentrations of thyroid hormones in laboratory animals, but it is unclear whether PBDEs disrupt thyroid hormones in pregnant women or newborn infants.

OBJECTIVES

We investigated the relationship between maternal PBDE levels and thyroid hormone concentrations in maternal and cord sera.

METHODS

We used data from the Health Outcomes and Measures of the Environment (HOME)Study, a prospective birth cohort of 389 pregnant women in Cincinnati, Ohio, who were enrolled from 2003 through 2006 and delivered singleton infants. Maternal serum PBDE concentrations were measured at enrollment (16 ± 3 weeks of gestation). Thyroid hormone concentrations were measured in maternal serum at enrollment (n = 187) and in cord serum samples (n = 256).

RESULTS

Median maternal serum concentrations of BDEs 28 and 47 were 1.0 and 19.1 ng/g lipid, respectively. A 10-fold increase in BDEs 28 and 47 concentrations was associated with a 0.85-μg/dL [95% confidence interval (CI): 0.05, 1.64] and 0.82-μg/dL (95% CI: 0.12, 1.51) increase in maternal total thyroxine concentrations (TT4), respectively. Both congeners were also positively associated with maternal free thyroxine (FT4). We also observed positive associations between BDE-47 and maternal total and free triiodothyronine (TT3 and FT3). A 10-fold increase in BDE-28 was associated with elevated FT3 concentrations (β = 0.14 pg/mL; 95% CI: 0.02, 0.26). In contrast, maternal PBDE levels were not associated with thyroid hormone concentrations in cord serum.

CONCLUSIONS

These findings suggest that maternal PBDE exposure, particularly BDEs 28 and 47, are associated with maternal concentrations of T4 and T3 during pregnancy.

Association between prenatal exposure to polybrominated diphenyl ethers and young children's neurodevelopment in China

The use of polybrominated diphenyl ethers (PBDEs) has been dramatically increasing over the last two decades in China. Animal studies suggest that prenatal exposure to PBDEs may result in neurodevelopmental deficits. Two hundred thirty-two participating mothers were recruited from a prospective birth cohort in rural northern China between September 2010 and February 2012. We analyzed 232 cord blood specimens for selected PBDE congeners and examined their association with children's developmental quotients (DQs) at 12 (n=192) and 24 (n=149) months of age based on the Gesell Developmental Schedules (motor, adaptive, language, and social domains). There were no substantial differences by demographic characteristics among the three time points: baseline, 12 and 24 months of age. Median cord blood levels of PBDE congeners 47, 99, 100, and 153 were 3.71, 6.70, 2.63, and 2.19 ng/g lipid, respectively. At 12 months of age, neither the individual nor total (the sum of BDEs 47, 99, 100, and 153) congener levels were associated with any of the four domain DQs. However, at 24 months of age, a 10-fold increase in BDE-99 levels was associated with a 2.16-point decrease [95% confidence interval (CI): -4.52, -0.20] in language domain DQs and a 10-fold increase in BDE-47 levels was associated with a 1.89-point decrease (95% CI: -3.75, -0.03) in social domain DQs. Prenatal exposure to PBDEs was associated with lower DQs in young children. The results contribute to the growing evidence that PBDEs could act as developmental neurotoxicants,and the findings have implications for children's environmental health in China.

The Correlation between Polybrominated Diphenyl Ethers (PBDEs) and Thyroid Hormones in the General Population: A Meta-Analysis

OBJECTIVE

Certain epidemiological studies have suggested exposure to polybrominated diphenyl ethers (PBDEs) affect the production and secretion of thyroid hormones (TH); however, conflicting results have been reported in different studies. There is not a convincing conclusion about this debate to date.

MATERIALS AND METHODS

To perform a meta-analysis determining if there are correlations between PBDEs exposure and the serum levels of TH. Medical and scientific literature databases were searched for articles that met the eligibility criteria. The included articles were assessed for methodological quality. The correlation coefficient values or regression coefficient values between PBDEs and thyroid stimulating hormone (TSH) or total thyroxine (TT4) from each article were used for analysis.

DATA SYNTHESIS

Sixteen articles were included in this meta-analysis. Pearson correlation coefficients (r) were directly collected or calculated from data given in the articles. Then, Fisher's z transformation was performed to convert each correlation coefficient to an approximately normal distribution. For z values between PBDEs exposure and TSH levels, the pooled z value for 18 studies was 0.08 (95% CI: -0.06, 0.22), and indicated significant heterogeneity (I2 values = 90.7%). Subgroup analysis was performed based on the median values of serum PBDEs in each study, there was not significant heterogeneity in each of the four subgroups (I2 values <30%). In meta-analysis of z values between PBDEs exposure and the levels of TT4, the pooled z value for 11 studies was -0.02 (95% CI: -0.11, 0.08), and also indicated significant heterogeneity (I2 values = 57.6%). Similar subgroup analysis was done for the PBDEs exposures and the levels of TT4. No significant heterogeneity was shown in either of the two subgroups (I2 values = 0).

CONCLUSION

The findings in our meta-analysis indicate the effects of PBDEs on thyroid function may mainly depend on PBDEs exposure and their levels found in serum. The relationship between PBDEs exposure and changes in thyroid function seem to fit an approximate u-shaped curve. These predictions await further verification, namely a prospective longitudinal study.

Association between Several Persistent Organic Pollutants and Thyroid Hormone Levels in Cord Blood Serum and Bloodspot of the Newborn Infants of Korea

Current knowledge on adverse endocrine disruption effects of persistent organic pollutants (POPs) among newborn infants is limited and often controversial. To investigate the associations between prenatal exposure to major POPs and thyroid hormone levels among newborn infants, both cord serum or maternal serum concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) were compared with five thyroid hormones in cord serum of newborn infants as well as TSH in bloodspot collected at 2 day after birth (n=104). Since cord serum thyroid hormones could be affected by those of mothers, thyroid hormone concentrations of the matching mothers at delivery were adjusted. In cord serum, BDE-47, -99, and Σchlordane (CHD) showed significant positive associations with cord or bloodspot TSH. At the same time, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorbenzene (HCB) showed negative associations with total T3 and total T4 in cord serum, respectively. Maternal exposure to β-hexachlorhexane (β-HCH), ΣCHD, ΣDDT, or p,p'-DDE were also associated with neonatal thyroid hormones. Although the sample size is small and the thyroid hormone levels of the subjects were within the reference range, our observation supports thyroid disrupting potential of several POPs among newborn infants, at the levels occurring in the general population. Considering the importance of thyroid hormones during gestation and early life stages, health implication of thyroid hormone effects by low level POPs exposure deserves further follow up investigations.

Residue profiles of organohalogen compounds in human serum from e-waste recycling sites in North Vietnam: Association with thyroid hormone levels

This study demonstrated the contamination levels of polychlorinated biphenyls (PCBs), hydroxylated PCBs (OH-PCBs), polybrominated diphenyl ethers (PBDEs), methoxylated PBDEs (MeO-PBDEs), hydroxylated PBDEs (OH-PBDEs), and bromophenols (BPhs), and their relationships with thyroid hormones (THs), in the serum of human donors from an e-waste recycling site and a rural site in Hung Yen province, Vietnam. Occupationally related exposure was indicated by significantly higher residue levels of PCBs, OH-PCBs, PBDEs, and BPhs in the serum of donors from the e-waste recycling site (median: 420, 160, 290, and 300pgg(-1) wet wt, respectively) than those in the serum of donors from the rural site (median: 290, 82, 230, and 200pgg(-)(1) wet wt, respectively). On the other hand, levels of OH-/MeO-PBDEs were significantly higher in serum of donors from the reference site (median: 160 and 20pgg(-1) wet wt, respectively) than in those from the e-waste recycling site (median: 43 and 0.52pgg(-1) wet wt, respectively). In addition, we implemented stepwise generalized linear models to assess the association between the levels of TH and PCBs, PBDEs, and their related compounds. In females, we found positive associations of PCBs and OH-PCB concentrations with total thyroxine, free thyroxine, total triiodothyronine, and free triiodothyronine, and a negative association with thyroid-stimulating hormone concentrations.

Prenatal exposure to endocrine disrupting chemicals in relation to thyroid hormone levels in infants - a Dutch prospective cohort study

BACKGROUND

Endocrine disrupting chemicals (EDCs) present in the environment may disrupt thyroid hormones, which in early life are essential for brain development. Observational studies regarding this topic are still limited, however as the presence of chemicals in the environment is ubiquitous, further research is warranted. The objective of the current study was to assess the association between exposure markers of various EDCs and thyroxine (T4) levels in newborns in a mother-child cohort in the Netherlands.

METHODS

Exposure to dichlorodiphenyldichloroethylene (DDE), three di-2-ethylhexyl phthalate (DEHP) metabolites, hexachlorobenzene (HCB), polychlorinated biphenyl (PCB)-153, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma or breast milk, and information on T4 levels in heel prick blood spots was obtained through the neonatal screening programme in the Netherlands. Linear regression models were composed to determine associations between each of the compounds and T4, which were stratified for gender and adjusted for a priori defined covariates.

RESULTS

Mean T4 level was 86.9 nmol/L (n = 83). Girls in the highest quartile of DDE and PFOA exposure showed an increased T4 level compared to the lowest quartile with both crude and fully adjusted models (DDE > 107.50 ng/L, +24.8 nmol/L, 95% CI 0.79, 48.75; PFOA > 1200 ng/L, +38.6 nmol/L, 95% CI 13.34, 63.83). In boys a lower T4 level was seen in the second quartile of exposure for both PFOS and PFOA, however after fully adjusting the models these associations were attenuated. No effects were observed for the other compounds.

CONCLUSION

DDE and perfluorinated alkyl acids may be associated with T4 in a sex-specific manner. These results should however be interpreted with caution, due to the relatively small study population. More research is warranted, as studies on the role of environmental contaminants in this area are still limited.

Atmospheric concentrations of persistent organic pollutants over the Pacific Ocean near southern Taiwan and the northern Philippines

This study investigates the atmospheric occurrence of persistent organic pollutants (POPs) over the Pacific Ocean near southern Taiwan and the northern Philippines. We determined sixty-six compounds, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DLPCBs), polybrominated diphenyl ethers (PBDEs), as well as polychlorinated diphenyl ethers (PCDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), and polybrominated biphenyls (PBBs), in air samples simultaneously collected from the offshore oceanic atmosphere (n=6) and over a rural area (n=2). We calculated the atmospheric World Health Organization 2005 toxic equivalency levels (WHO2005-TEQ), for the total dioxin-like POPs, including PCDD/Fs, DLPCBs, and PBDD/Fs, being 0.00612 pg WHO2005-TEQ/m(3) and 0.0138 pg WHO2005-TEQ/m(3) over the ocean and land, respectively. We found unexpected lower averaged atmospheric PBDE concentrations in the rural area (15.9 pg/m(3)) than over the ocean (31.1 pg/m(3)) due to higher levels of the BDE209 congener, although the difference was not statistically significant. We have compared and reported our field results with previously published datasets over the global oceans, which suggest PCBs and PBDEs are the dominant chemical contaminants in the global oceanic atmosphere among these halogenated POPs (e.g. PCBs and Σdi-hepta PBDEs could be found in the range of 0.09-48.7 and 8.07-94.0 pg/m(3), respectively, including our dataset). However, there are still very few investigations on the global atmospheric levels of PBDD/Fs, PCDEs and PBBs and our data sums to these earlier studies. Finally, we point out that the halogenated POPs originated from Taiwan or the continental East Asia which could easily reach remote ocean sites via atmospheric transport.

Occurrences of major polybrominated diphenyl ethers (PBDEs) in maternal and fetal cord blood sera in Korea

Polybrominated diphenyl ethers (PBDEs) are of growing public health concern because of their potential toxicities which range from endocrine disruption to neurodevelopment. However, information on their exposure among sensitive human populations is limited. The objectives of this study were to determine the levels of major PBDEs in blood sera of pregnant women and their matching newborn infants. For this purpose, a total of 198 maternal blood samples and 118 matching umbilical cord blood samples were collected from four regions of South Korea in 2011, and were determined for 19 PBDE congeners. Various demographic, dietary, and behavioral characteristics were asked in a questionnaire survey. Average concentration of total PBDEs in maternal blood serum was 3.34 ± 8.42 ng/g lipid weight (lw) at delivery and 3.14 ± 7.46 ng/g lw at 6 months of pregnancy, respectively. In cord blood serum, an average of 9.37 ± 12.60 ng/g lw was detected. Among the measured PBDE congeners, BDE-47, BDE-99 and BDE-153 were most dominant in both maternal and cord blood sera. Relatively higher levels of BDE-99 were detected in cord blood serum. Strong positive correlations were detected between maternal and cord blood serum samples, indicating the importance of maternal transfer. Health consequences of transplacental exposure to PBDEs among fetuses and newborn infants warrant further investigation.

Prenatal polybrominated diphenyl ether exposures and neurodevelopment in U.S. children through 5 years of age: the HOME study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are persistent chemicals that have been widely used as flame retardants in furniture, carpet padding, car seats, and other consumer products during the past three decades.

OBJECTIVE

We examined whether in utero exposure to PBDEs is associated with child cognitive function and behavior in a U.S. study sample.

METHODS

In a prospective birth cohort, we measured maternal serum concentrations of BDE-47 and other PBDE congeners in 309 women at 16 weeks of gestation during 2003-2006 and followed their children in Cincinnati, Ohio. We measured cognitive and motor abilities using the Bayley Scales of Infant Development-II at ages 1, 2, and 3 years; intelligence using the Wechsler Preschool and Primary Scale of Intelligence-III at age 5 years; and children's behaviors using the Behavioral Assessment System for Children-2 annually at ages 2-5 years. We used linear mixed models or generalized estimating equations with adjustment for potential confounders to estimate associations between these outcomes and log10-transformed PBDE concentrations.

RESULTS

The geometric mean of BDE-47 in maternal serum (20.1 ng/g lipid) was comparable with U.S. adult national reference values. Prenatal BDE-47 was not significantly associated with Bayley Mental or Psychomotor Development Indices at 1-3 years, but a 10-fold increase in prenatal BDE-47 was associated with a 4.5-point decrease (95% CI: -8.8, -0.1) in Full-Scale IQ and a 3.3-point increase (95% CI: 0.3, 6.3) in the hyperactivity score at age 5 years.

CONCLUSIONS

Prenatal exposure to PBDEs was associated with lower IQ and higher hyperactivity scores in children.