Polybrominated diphenyl ethers (PBDEs) in aborted human fetuses and placental transfer during the first trimester of pregnancy

Exposure of Female Rats to an Environmentally Relevant Mixture of Brominated Flame Retardants Targets the Ovary, Affecting Folliculogenesis and Steroidogenesis

Brominated flame retardants (BFRs) are incorporated into various consumer products to prevent flame propagation. These compounds leach into the domestic environment, resulting in chronic exposure and contamination. Pregnancy failure is associated with high levels of BFRs in human follicular fluid, raising serious questions regarding their impact on female reproductive health. The goal of this study is to elucidate the effects of an environmentally relevant BFR mixture on female rat ovarian functions (i.e., folliculogenesis and steroidogenesis). A BFR dietary mixture formulated to mimic the relative BFR congener levels in North American house dust was administered to adult female Sprague-Dawley rats from 2 to 3 wk before mating until Gestational Day 20; these diets were designed to deliver nominal doses of 0, 0.06, 20, or 60 mg/kg/day of the BFR mixture. Exposure to BFRs triggered an approximately 50% increase in the numbers of preantral and antral follicles and an enlargement of the antral follicles in the ovaries of the dams. A significant reduction in the expression of catalase, an antioxidant enzyme, and downregulation of the expression of insulin-like factor 3 (Insl3) and 17alpha-hydroxylase (Cyp17a1) were observed in the ovary. In addition, BFR exposure affected steroidogenesis; we observed a significant decrease in circulating 17-hydroxypregnenolone and an increase in testosterone concentrations in BFR-exposed dams. Thus, BFRs target ovarian function in the rat, adversely affecting both folliculogenesis and steroidogenesis.

Developmental toxicity of the PBDE metabolite 6-OH-BDE-47 in zebrafish and the potential role of thyroid receptor β

6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (6-OH-BDE-47) is both a polybrominated diphenyl ether (PBDE) flame retardant metabolite and a marine natural product. It has been identified both as a neurotoxicant in cell-based studies and as a developmental toxicant in zebrafish. However, hydroxylated PBDE metabolites are also considered thyroid hormone disruptors due to their structural similarity to endogenous thyroid hormones. The purpose of this study was to evaluate the effects of 6-OH-BDE-47 on a developmental pathway regulated by thyroid hormones in zebrafish. Morphological measurements of development (head trunk angle, otic vesicle length, and eye pigmentation) were recorded in embryos at 30h post fertilization (hpf) and detailed craniofacial morphology was examined in 4 day old larvae using cartilage staining. Exposure to 6-OH-BDE-47 resulted in severe developmental delays. A 100nM concentration resulted in a 26% decrease in head trunk angle, a 54% increase in otic vesicle length, and a 42% decrease in eye pigmentation. Similarly, altered developmental morphology was observed following thyroid receptor β morpholino knockdown, exposure to the thyroid hormone triiodothyronine (T3) or to thyroid disrupting chemicals (TDC; iopanoic acid and propylthiouracil). The threshold for lower jaw deformities and craniofacial cartilage malformations was at doses greater than 50nM. Of interest, these developmental delays and effects were rescued by microinjection of TRβ mRNA during the 1-2 cell stage. These data indicate that OH-BDEs can adversely affect early life development of zebrafish and suggest they may be impacting thyroid hormone regulation in vivo through downregulation of the thyroid hormone receptor.

Exploring the associations between microRNA expression profiles and environmental pollutants in human placenta from the National Children's Study (NCS)

The placenta is the principal regulator of the in utero environment, and disruptions to this environment can result in adverse offspring health outcomes. To better characterize the impact of in utero perturbations, we assessed the influence of known environmental pollutants on the expression of microRNA (miRNA) in placental samples collected from the National Children's Study (NCS) Vanguard birth cohort. This study analyzed the expression of 654 miRNAs in 110 term placentas. Environmental pollutants measured in these placentas included dichlorodiphenyldichloroethylene (DDE), bisphenol A (BPA), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), arsenic (As), mercury (Hg), lead (Pb), and cadmium (Cd). A moderated t-test was used to identify a panel of differentially expressed miRNAs, which were further analyzed using generalized linear models. We observed 112 miRNAs consistently expressed in >70% of the samples. Consistent with the literature, miRNAs located within the imprinted placenta-specific C19MC cluster, specifically mir-517a, mir-517c, mir-522, and mir-23a, are among the top expressed miRNA in our study. We observed a positive association between PBDE 209 and miR-188-5p and an inverse association between PBDE 99 and let-7c. Both PCBs and Cd were positively associated with miR-1537 expression level. In addition, multiple let-7 family members were downregulated with increasing levels of Hg and Pb. We did not observe DDE or BPA levels to be associated with placental miRNA expression. This is the first birth cohort study linking environmental pollutants and placental expression of miRNAs. Our results suggest that placental miRNA profiles may signal in utero exposures to environmental chemicals.

BDE-209 inhibits pluripotent genes expression and induces apoptosis in human embryonic stem cells

Decabromodiphenyl ether (BDE-209) has been detected in human serum, semen, placenta, cord blood and milk worldwide. However, little is known regarding the potential effects on the early human embryonic development of BDE-209. In this study, human embryonic stem cell lines FY-hES-10 and FY-hES-26 were used to evaluate the potential effects and explore the toxification mechanisms using low-level BDE-209 exposure. Our data showed that BDE-209 exposure (1, 10 and 100 nM) reduced the expression of pluripotent genes such as OCT4, SOX2 and NANOG and induced human embryonic stem cells (hESCs) apoptosis. The downregulation of BIRC5/BCL2 and upregulation of BAX were related to apoptosis of hESCs induced by BDE-209 exposure. A mechanism study showed that OCT4 down-regulation accompanied by OCT4 promoter hypermethylation and increasing miR-145/miR-335 levels, OCT4 inhibitors. Moreover, BDE-209 could increase the generation of intracellular reactive oxygen species (ROS) and decrease SOD2 expression. The ROS increase and OCT4 downregulation after BDE-209 exposure could be reversed partly by antioxidant N-acetylcysteine supplement. These findings showed that BDE-209 exposure could decrease pluripotent genes expression via epigenetic regulation and induce apoptosis through ROS generation in human embryonic stem cells in vitro.

Occurrence of specific environmental risk factors in brain tissues of sudden infant death and sudden intrauterine unexpected death victims assessed with gas chromatography-tandem mass spectrometry

Sudden infant death syndrome (SIDS) and sudden intrauterine unexpected death syndrome (SIUDS) are an unresolved teaser in the social-medical and health setting of modern medicine and are the result of multifactorial interactions. Recently, prenatal exposure to environmental contaminants has been associated with negative pregnancy outcomes, and verification of their presence in fetal and newborn tissues is of crucial importance. A gas chromatography-tandem mass spectrometry (MS/MS) method, using a triple quadrupole analyzer, is proposed to assess the presence of 20 organochlorine pesticides, two organophosphate pesticides, one carbamate (boscalid), and a phenol (bisphenol A) in human brain tissues. Samples were collected during autopsies of infants and fetuses that died suddenly without any evident cause. The method involves a liquid-solid extraction using n-hexane as the extraction solvent. The extracts were purified with Florisil cartridges prior to the final determination. Recovery experiments using lamb brain spiked at three different concentrations in the range of 1-50 ng g(-1) were performed, with recoveries ranging from 79 to 106%. Intraday and interday repeatability were evaluated, and relative standard deviations lower than 10% and 18%, respectively, were obtained. The selectivity and sensitivity achieved in multiple reaction monitoring mode allowed us to achieve quantification and confirmation in a real matrix at levels as low as 0.2-0.6 ng g(-1). Two MS/MS transitions were acquired for each analyte, using the Q/q ratio as the confirmatory parameter. This method was applied to the analysis of 14 cerebral cortex samples (ten SIUDS and four SIDS cases), and confirmed the presence of several selected compounds.

Polybrominated diphenyl ethers in human placenta associated with neonatal physiological development at a typical e-waste recycling area in China

Our aim of this study was to characterize the exposure pattern of polybrominated diphenyl ethers(PBDEs) in human placenta and assess their potential effects on neonates. Placenta samples were obtained from a typical e-waste area in Guiyu and a reference area in Haojiang, China. The median ΣPBDE concentration was 32.25 ng/g lipid weight (lw) in placenta samples from Guiyu, and 5.13 ng/g lw from Haojiang. BDE-209 predominated in placenta samples, followed by BDE-28, -47, -99 -153, -183. Residence in Guiyu contributed the most to elevated PDBE levels. Neonatal physiological indices, including bodymass index (BMI), Apgar 1 score and head circumference, were reduced in Guiyu group. No significant difference was found in neonatal weight between the two groups, but neonatal body length in Guiyu was increased. Our data suggest prenatal exposure to PBDEs is high at the e-waste recycling area, and may lead to adverse physiological development in the fetus.

Association of PCB, PBDE and PCDD/F body burdens with hormone levels for children in an e-waste dismantling area of Zhejiang Province, China

Increased electronic waste (e-waste) has raised public concerns regarding exposure to numerous toxic contaminants, particularly polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In China, the body burdens of PCBs, PBDEs and PCDD/Fs are associated with thyroid hormones in populations from e-waste dismantling sites; however, it is unclear whether this association occurs in children. In this study, we determined the serum levels of PCBs, PBDEs and PCDD/Fs and the endocrine hormones including free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), total thyroxine (TT4), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), cortisol and growth hormone (GH) in 21 children from an e-waste dismantling area and 24 children from a control area. The results showed that the mean levels of ∑PCBs and ∑PBDEs in the exposure group were significantly higher than in the control group (40.56 and 32.09 ng g(-1) lipid vs. 20.69 and 8.43 ng g(-1) lipid, respectively, p<0.01 for each), and the mean level of ∑PCDD/Fs in the exposure group was higher than in the control group, but the difference was not significant (206.17 vs. 160.27 pg g(-1) lipid, p>0.05). For the endocrine hormones, we did not find significant differences between the exposed and control groups, although the mean levels of FT3, TT3, TT4, ACTH, cortisol and GH were higher, whereas the mean levels of FT4 and TSH were lower in the exposed group. The mean level of ∑PBDEs was positively correlated with the mean levels of ∑PCBs (r=0.60, p<0.05) and ∑PCDD/Fs (r=0.61, p<0.05). Furthermore, the mean level of ∑PBDEs was positively correlated with ACTH (r=0.61, p<0.05). In conclusion, our data suggested that exposure to e-waste dismantling environment increased the body burdens of PCBs and PBDEs in local children and that these contaminants released from the e-waste might contribute to abnormal changes in hormone levels.

A systematic review of the human body burden of e-waste exposure in China

As China is one of the countries facing the most serious pollution and human exposure effects of e-waste in the world, much of the population there is exposed to potentially hazardous substances due to informal e-waste recycling processes. This report reviews recent studies on human exposure to e-waste in China, with particular focus on exposure routes (e.g. dietary intake, inhalation, and soil/dust ingestion) and human body burden markers (e.g. placenta, umbilical cord blood, breast milk, blood, hair, and urine) and assesses the evidence for the association between such e-waste exposure and the human body burden in China. The results suggest that residents in the e-waste exposure areas, located mainly in the three traditional e-waste recycling sites (Taizhou, Guiyu, and Qingyuan), are faced with a potential higher daily intake of these pollutants than residents in the control areas, especially via food ingestion. Moreover, pollutants (PBBs, PBDEs, PCBs, PCDD/Fs, and heavy metals) from the e-waste recycling processes were all detectable in the tissue samples at high levels, showing that they had entered residents' bodies through the environment and dietary exposure. Children and neonates are the groups most sensitive to the human body effects of e-waste exposure. We also recorded plausible outcomes associated with exposure to e-waste, including 7 types of human body burden. Although the data suggest that exposure to e-waste is harmful to health, better designed epidemiological investigations in vulnerable populations, especially neonates and children, are needed to confirm these associations.

Selected persistent organic pollutants in human placental tissue from the United States

Emerging and legacy environmental pollutants such as polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine pesticide metabolite DDE are found in human placenta, indicating prenatal exposure, but data from the United States are sparse. We sought to determine concentrations of these compounds in human placentae as part of a formative research project conducted by the National Children's Study Placenta Consortium. A total of 169 tissue specimens were collected at different time points post delivery from 43 human placentae at three U.S. locations, and analyzed by gas chromatography coupled with mass spectrometry following extraction using matrix solid phase dispersion. PBDEs, PCBs, and DDE were detected in all specimens. The concentrations of 10 PBDEs (Σ10PBDEs), 32 PCBs (Σ32PCBs) and p,p'-DDE were 43-1723, 76-856 and 10-1968pgg(-1) wet weight, respectively, in specimens collected shortly after delivery. Significant geographic differences in PBDEs were observed, with higher concentrations in placentae collected in Davis, CA than in those from Rochester, NY or Milwaukee, WI. We combined these with other published data and noted first-order declining trends for placental PCB and DDE concentrations over the past decades, with half-lives of about 5 and 8years, respectively. The effect of time to tissue collection from refrigerated placentae on measured concentrations of these three classes of persistent organic pollutants was additionally examined, with no significant effect observed up to 120h. The results of this work indicate that widespread prenatal exposure to persistent organic pollutants in the United States continues.

Elevated serum polybrominated diphenyl ethers and alteration of thyroid hormones in children from Guiyu, China

Informal electronic waste (e-waste) recycling results in serious environmental pollution of polybrominated diphenyl ethers (PBDEs) and heavy metals. This study explored whether there is an association between PBDEs, heavy metal and key growth- and development-related hormones in children from Guiyu, an e-waste area in southern China. We quantified eight PBDE congeners using gas chromatographic mass spectrometry, lead and cadmium utilizing graphite furnace atomic absorption spectrometry, three thyroids with radioimmunoassay and two types of growth hormones by an enzyme-linked immune-sorbent assay (ELISA) in 162 children, 4 to 6 years old, from Guiyu. In blood, median total PBDE was 189.99 ng/g lipid. Lead and cadmium concentrations in blood averaged 14.53±4.85 µg dL-1 and 0.77±0.35 µg L-1, respectively. Spearman partial correlation analysis illustrated that lead was positively correlated with BDE153 and BDE183. Thyroid-stimulating hormone (TSH) was positively correlated with almost all PBDE congeners and negatively correlated with insulin-like growth factor binding protein-3 (IGFBP-3), whereas free triiodothyronine (FT3) and free thyroxine (FT4) were negatively correlated with BDE154. However, no correlation between the hormones and blood lead or cadmium levels was found in this study. Adjusted multiple linear regression analysis showed that total PBDEs was negatively associated with FT3 and positively associated with TSH. Notably, FT4 was positively correlated with FT3, house functions as a workshop, and father's work involved in e-waste recycling and negatively correlated with vitamin consumptions. TSH was negatively related with FT4, paternal residence time in Guiyu, working hours of mother, and child bean products intake. IGFBP-3 was positively correlated with IGF-1 and house close to an e-waste dump. These results suggest that elevated PBDEs and heavy metals related to e-waste in Guiyu may be important risk factors for hormone alterations in children.