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

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.

Associations of cord serum polybrominated diphenyl ether (PBDE) mixture with birth outcomes and mediating role of thyroid function: Evidence from the Sheyang Mini Birth Cohort Study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs), a series of worldwide applied flame retardants, may influence fetal growth and interfere with thyroid function. The study intended to explore the relationship between in-utero exposure to PBDE mixture and newborn anthropometric indexes and to further examine the potential mediating role of thyroid function.

METHODS

Demographics and laboratory measures of 924 mother-infant pairs were obtained from the database of the Sheyang Mini Birth Cohort Study. We applied gas chromatography-mass spectrometry (GC-MS) and electrochemiluminescence immunoassay to measure nine PBDE congeners and seven thyroid function parameters in umbilical cord serum samples, respectively. We fitted generalized linear models and Bayesian kernel machine regression (BKMR) to evaluate associations of lipid-adjusted cord serum PBDEs, as individuals and as a mixture, with newborn anthropometric and cord serum thyroid function parameters. We applied causal mediation analysis to test our hypothesis that thyroid function parameters act as a mediator between PBDEs and birth outcomes.

RESULTS

The molarity of cord serum ∑9PBDE had a median value of 31.23 nmol/g lipid (IQR 19.14 nmol/g lipid, 54.77 nmol/g lipid). BDE-209 was the most dominant congener. Birth length was positively associated with both single exposure to BDE-28 and cumulative exposure to PBDEs. Correspondingly, ponderal index (PI) was negatively associated with BDE-28 and the total effects of PBDE mixture. Free triiodothyronine had a negative trend with BDE-209 and PBDE mixture. In the sex-stratified analysis, BDE-153 concentrations were positively correlated with PI among males (β = 0.03; 95%CI: 0.01, 0.05; P = 0.01) but not among females. Cord serum thyrotropin mediated 14.92% of the estimated effect of BDE-153 on PI.

CONCLUSIONS

In-utero mixture exposure to PBDEs was associated with birth outcomes and thyroid function. Thyroid function might act as a mediator in the process in which PBDEs impact the growth of the fetus.

Decabromodiphenyl ether exposure reduces dabrafenib sensitivity of papillary thyroid carcinoma harboring BRAFV600E mutation through the EGFR-CRAF-MAPK pathway: An in vitro study

Decabromodiphenyl ether (BDE209) has been demonstrated to be associated with thyroid dysfunction and thyroid carcinoma risk as a widely used brominated flame retardants. Although dabrafenib has been confirmed to be a promising therapeutic agent for papillary thyroid carcinoma (PTC) harboring BRAFV600E mutation, the rapid acquired dabrafenib resistance has brought a great challenge to clinical improvement and the underpinning mechanisms remain poorly defined. By treating PTC-derived and normal follicular epithelial cell lines with BDE209, we assessed its impact on the MAPK pathway's activation and evaluated the resultant effects on cell viability and signaling pathways, utilizing methods such as Western blot, IF staining, and RNA-seq bioinformatic analysis. Our findings reveal that BDE209 exacerbates MAPK activation, undermining dabrafenib's inhibitory effects by triggering the EGFR pathway, thereby highlighting BDE209's potential to diminish the pharmacological efficacy of dabrafenib in treating BRAF-mutated PTC. This research underscores the importance of considering environmental factors like BDE209 exposure in the effective management of thyroid carcinoma treatment strategies.

Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (-0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Indoor environment, physiological factors, and diet as predictors of halogenated flame retardant levels in stool and plasma of children from a Canadian cohort

Exposure to halogenated flame retardants (HFRs) has been associated with various adverse effects on human health. Human exposure to HFRs mainly occurs through diet, ingesting contaminated dust, and inhaling contaminated air. Understanding and characterizing the variables linked to these exposure pathways is essential for developing effective risk assessment and mitigation strategies. We investigated indoor environment quality, physiological factors, and diet as potential predictors of HFRs concentration in children's plasma and stool. A selected number of HFRs, including polybrominated diphenyl ethers (PBDEs), Dechlorane-like compounds, and emerging halogenated flame retardants, were measured in children from eastern Quebec (Canada). Information on indoor environment quality, physiological factors, and diet was obtained through self-report questionnaires. Our results show that lower brominated compounds, which are more volatile, were primarily correlated to indoor environment quality. Notably, the use of air purifiers was associated with lower BDE47 and BDE100 levels in blood and newer residential buildings were associated with higher concentrations of BDE47. A significant seasonal variation was found in stool samples, with higher levels of lower brominated PBDEs (BDE47 and BDE100) in samples collected during summer. No association between household income or maternal education degree and HFRs was found. Among emerging compounds, Dec602 and Dec603 were associated with the most variables, including the use of air dehumidifiers, air conditioning, and air purifiers, and the child's age and body fat percentage.

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.

Complementarity of plasma and stool for the characterization of children's exposure to halogenated flame retardants: Update on analytical methods and application to a Canadian cohort

Sixteen halogenated flame retardants including Polybrominated diphenyl ethers (PBDEs), Dechlorane-like compounds, and emerging halogenated flame retardants were measured in stool and plasma samples from children aged 8.9-13.8 years old. Samples were obtained from a Canadian cohort investigating the effect of contaminants on children's neurodevelopment in the Estrie region, Québec, Canada. The method for stool analysis developed for this study showed good recovery for all targeted compounds (73%-93%) with associated relative standard deviation (RSD) in the range of 16.0%-30.7% for most compounds except for the thermosensitive BDE209, OBTMBI, and BTBPE, which showed slightly higher RSD, i.e., 49.3%, 37.2%, and 34.9% respectively. Complementarity investigation of stool and blood samples allowed us to better characterize human exposure to these halogenated flame retardants. Exposure patterns differed significantly between stool and blood, notably in the relative abundance of BDE47, BDE100, BDE99, and BDE153 and the detection frequencies of BDE209, syn-DP, anti-DP, and DBDPE. There was no correlation between the two matrices' PBDEs concentration levels except for BDE153 (rho = 0.44, p < 0.01). Our results indicate that future epidemiological studies may benefit from the use of stool as a complementary matrix to blood, especially investigations into chemical impacts on the gut microbiome. Results also revealed that children from the GESTE cohort, an Eastern Canadian semi-rural cohort, are exposed to both historical and emergent flame retardants.

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.

Serum polybrominated diphenyl ether exposure and influence factors in blood donors of Wuxi adults from 2013 to 2016

Polybrominated diphenyl ethers (PBDEs) have been used as brominated flame retardants worldwide and are correlated with extensive environmental pollution and human health concerns. This study is aimed at analyzing the concentrations of PBDEs and at evaluating their temporal trends among a population of blood donors (n = 33) over a 4-year period. A total of 132 serum samples were used for PBDE detection. Nine PBDE congeners were quantified in serum samples by gas chromatography with mass spectrometry (GC-MS). The median concentrations of Σ₉PBDEs in each year were 33.46, 29.75, 30.85, and 35.02 ng/g lipid, respectively. Most of the PBDE congeners showed a downward trend from 2013 to 2014 and then increased after 2014. No correlations between age and PBDE congener concentrations were observed, while concentrations of each congener and Σ₉PBDE were nearly always lower in females than in males, especially in BDE-66, BDE-153, BDE-183, BDE-190, and Σ₉PBDE. We also found that the intake of fish, fruit, and eggs in the daily diet was related to the exposure level of PBDEs. Our results suggest that, as deca-BDE is still produced and used in China, diet is an important exposure pathway for PBDEs, and follow-up studies will be required to improve our understanding of the behaviors of PBDE isomers in humans and the exposure levels.

Legacy and novel brominated flame retardants in air of Ny-Ålesund, Arctic from 2011 to 2019

Concentrations of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in the atmosphere of Ny-Ålesund, Svalbard, were investigated. Passive air samples were collected for eight consecutive one-year periods from August 2011 to August 2019 at seven Arctic sampling sites. High-resolution gas chromatography coupled with high-resolution mass spectrometry (HRGC-HRMS) and gas chromatography coupled with election capture negative ionization mass spectrometry (GC-NCI-MS) were employed for PBDE and NBFR analysis, respectively. The median concentrations of Ʃ₁₁PBDEs and Ʃ₆NBFRs were 0.6 pg/m³ and 4.0 pg/m³, respectively. Hexabromobenzene and BDE-47 were the most abundant NBFR and PBDE congeners in the atmosphere, accounting for 31% and 24% of ƩNBFR and ƩPBDE concentrations, respectively. ƩNBFR concentration was approximately six times higher than that of ƩPBDEs in the same samples. Among NBFRs, the concentrations of 1,2,3,4,5-pentabromobenzene, 2,3,4,5,6-pentabromobenzene, and 2,3-dibromopropyl-2,4,6-tribromophenyl ether showed increasing temporal variations, with estimated doubling times of 3.0, 3.3, and 2.8 years, respectively. The concentrations of almost all PBDE congeners showed a decreasing variation, with halving times ranging from 2.1 to 9.5 years.

Potential Health Risk to Brazilian Infants by Polybrominated Diphenyl Ethers Exposure via Breast Milk Intake

Polybrominated diphenyl ethers (PBDEs) are ubiquitous flame retardants and are environmentally persistent. PBDEs show endocrine disruption, neurotoxicity, and lower birth weight in infants, and their human body burden has become a public health concern. The infants' exposure begins in the prenatal period and continues via breast milk ingestion, although, little is known about the factors that may influence this exposure. In this study, PBDE levels in Brazilian breast milk were assessed in 200 lactating women. The risk assessment of infants' exposure to PBDE was performed through the estimated daily intake (EDI) calculation. The geometric mean (GM) of ∑_PBDEs levels was 2.33 (0.14-6.05) ng/g wet weight. At least one PBDE congener was detected in the samples, and the 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) showed a 100% of detection rate (GM of 1.05 ng/g). Location of residence, maternal level education, monthly salary, and race were positively associated with PBDE levels (p < 0.05). The EDI of BDE-47 was higher in Belo Horizonte (8.29 ng/kg/day) than in Viçosa (6.36 ng/kg/day), as well as for the ∑_PBDEs (19.77 versus 12.78 ng/kg/day) (p < 0.05). Taking the high detection rate of PBDEs in breast milk and their toxicity, continuous studies on infant exposure, fetal growth, and child neurodevelopment are requested.

Long-Term Exposure to Decabromodiphenyl Ether Promotes the Proliferation and Tumourigenesis of Papillary Thyroid Carcinoma by Inhibiting TRß

Simple Summary

PBDEs have been reported to have endocrine-disrupting and tumour-promoting activity; however, the effects of BDE209 (the highest brominated PBDEs) on the thyroid and the underlying mechanisms are unclear. In this study, we found that long-term exposure to BDE209 could cause chronic toxicity and potential tumourigenesis by inhibiting the expression and function of TRß, which induces the proliferation of thyroid tissue and the oncogenesis of thyroid carcinoma. These findings emphasize the damaging effects that exposure to BDE209 has on human thyroid and papillary thyroid carcinoma.

Abstract

Polybrominated diphenyl ethers (PBDEs) have been reported to possess endocrine-disrupting and tumour-promoting activity. However, the effects of long-term exposure to decabromodiphenyl ether (BDE209) on thyroid tumourigenesis of papillary thyroid carcinoma (PTC) and the underlying mechanisms remain poorly defined. In this study, functional assays in vitro and mouse models in vivo were used to evaluate the toxic effects of long-term exposure to environmental concentrations of BDE209 on the pathogenesis and progression of PTC. MTS, EdU and colony-forming assays confirmed the chronic toxicity of BDE209 on the proliferation of human normal follicular epithelial cell line (Nthy-ori 3-1) and PTC-derived cell lines (TPC-1 and BCPAP). Wound and Transwell assays showed that BDE209 exacerbated the aggressiveness of PTC cells. BDE209 significantly promoted cell proliferation during the S and G2/M phases of the cell cycle. Mechanistically, BDE209 altered the thyroid system by acting as a competitive inhibitor of thyroid receptor beta (TRß) expression and function, which was further proven by public databases and RNA-seq bioinformation analysis. Taken together, these results demonstrated that BDE209 has chronic toxicity and potential tumourigenic effects on the thyroid by inhibiting TRß.

Polychlorinated naphthalene concentrations in human serum caused by unintentional production and emissions, and potential effects of polychlorinated naphthalenes on thyroid hormones

The concentrations of 75 polychlorinated naphthalene (PCN) congeners in 95 human serum samples from the Fengjiang electronic waste dismantling area and Huangyan District in Taizhou City (Zhejiang Province, China) were determined. Thyroid hormone (FT3, FT4, TSH, and TRH) concentrations in the samples were also determined. The total PCN concentrations in the samples from Fengjiang and Huangyan were 1.29 × 10⁴-4.28 × 10⁵ and 8.29 × 10²-6.45 × 10⁵ pg/g lipid, respectively. The less-chlorinated (Cl_1-3) PCN concentrations were relatively high in all of the samples, and the concentrations in the samples from the two areas were not significantly different. The sums of the combustion-related PCN congener concentrations were significantly higher in the samples from Fengjiang than in the samples from Huangyan, and the sums of the more-chlorinated (Cl_4-8) PCNs were slightly higher in the samples from Fengjiang than in the samples from Huangyan. The relationship between the PCN concentration and age indicated that electronic waste controls have decreased human exposure to PCNs but that attention should still be paid to exposure to less-chlorinated PCNs. The main PCN congeners that contributed to the toxic equivalent concentrations were markedly different for the samples from Fengjiang and Huangyan. CN-66/67 was dominant for the Fengjiang samples and CN-10 was dominant for the Huangyan samples. Attention should be paid to the risks posed by less-chlorinated PCNs to human health. CN-1, CN-2, and CN-20 concentrations are related to human thyroid hormone levels, and the relationships between less-chlorinated PCN concentrations and thyroid hormone concentrations should be further studied.

Biotechnology-based microbial degradation of plastic additives

Plastic additives are agents responsible to the flame resistance, durability, microbial resistance, and flexibility of plastic products. High demand for production and use of plastic additives is associated with environmental accumulation and various health hazards. One of the suitable methods of depleting plastic additive in the environment is bioremediation as it offers cost-efficiency, convenience, and sustainability. Microbial activity is one of the effective ways of detoxifying various compounds as microorganisms can adapt in an environment with high prevalence of pollutants. The present review discusses the use and abundance of these plastic additives, their health-related risks, the microorganisms capable of degrading them, the proposed mechanism of biodegradation, and current innovations capable of improving the efficiency of bioremediation.

Polybrominated Diphenyl Ether Serum Concentrations and Depressive Symptomatology in Pregnant African American Women

(1) Polybrominated diphenyl ethers (PBDEs) were widely produced in the United States until 2004 but remain highly persistent in the environment. The potential for PBDEs to disrupt normal neuroendocrine pathways resulting in depression and other neurological symptoms is largely understudied. This study examined whether PBDE exposure in pregnant women was associated with antenatal depressive symptomatology. (2) Data were collected from 193 African American pregnant women at 8–14 weeks gestation. Serum PBDEs and depressive symptoms were analyzed and a mixture effect was calculated. (3) Urban pregnant African American women in the Southeastern United States had a high risk of depression (27%) compared to the National average. Increased levels of PBDEs were found. BDE-47 and -99 exposures are significantly associated with depressive symptomatology in the pregnant cohort. The weighted body burden estimate of the PBDE mixture was associated with a higher risk of mild to moderate depression using an Edinburgh Depression Scale cutoff score of ≥10 (OR = 2.93; CI 1.18, 7.82). (4) Since antenatal depression may worsen in postpartum, reducing PBDE exposure may have significant clinical implications.

Dietary Intake of Endocrine Disrupting Substances Presents in Environment and Their Impact on Thyroid Function

According to the available data, environmental pollution is a serious problem all over the world. Between 2015 and 2016, pollution was responsible for approximately nine million deaths worldwide. They also include endocrine disrupting chemicals (EDCs) that can interfere with the functioning of the thyroid gland. They are characterized by high persistence in the environment. These substances can enter the body through the gastrointestinal tract, respiratory system, as well as contact with the skin and overcome the placental barrier. EDC can be found in food, water, and personal care products. They can get into food from the environment and as a result of their migration to food products and cosmetics from packaging. EDCs can disrupt the functioning of the thyroid gland through a number of mechanisms, including disrupting the activation of thyroid receptors and the expression of genes that are related to the metabolism, synthesis, and transport of thyroid hormones (HT). There is a need to strengthen the food safety policy that aimed at the use of appropriate materials in direct contact with food. At the same time, an important action is to reduce the production of all waste and, when possible, use biodegradable packaging, which may contribute to the improvement of the quality of the entire ecosystem and the health of food, thus reducing the risk of developing thyroid diseases.

Circulating lead modifies hexavalent chromium-induced genetic damage in a chromate-exposed population: An epidemiological study

Chromium (Cr) can coexist with other heavy metals in the blood of chronically chromate-exposed individuals. However, few studies have explored the health impacts of other hazardous metals after exposure to hexavalent chromium [Cr(VI)]. This study aimed to assess the modification effects of blood lead (Pb) on the genetic damage induced by Cr(VI). During 2010-2019, 1000 blood samples were collected from 455 workers exposed to chromate and 545 workers not exposed to chromate from the same factory with similar labor intensity. The levels of Cr and Pb were measured in whole blood samples. Micronucleus frequency (MNF) and urinary 8-hydroxydeoxyguanosine (8-OHdG) were measured to reflect different types of genetic damage. Multivariate linear regression analyses were performed to evaluate the associations between hazardous metals and the modification effects of Pb on genetic damage. The geometric mean levels of Cr and Pb in the exposure group were significantly higher than those in the control group [Cr: 6.42 (6.08- 6.79) vs. 1.29 (1.22- 1.36) μg/L; Pb: 38.82 (37.22- 40.50) vs. 34.47 (33.15- 35.85) μg/L]. The geometric means of urinary 8-OHdG and MNF in exposure group were 4.00 (3.64- 4.40) μg/g and 5.40 (4.89- 5.97) ‰, respectively, significantly higher than the 3.20 (2.94- 3.48) μg/g and 4.57 (4.15- 5.03) ‰, respectively, in control group. log₂Cr was independently and positively associated with urinary 8-OHdG (β_-adjusted = 0.143, 95% CI: 0.082- 0.204) and MNF (β_-adjusted = 0.303, 95%CI: 0.020- 0.587). With the change in circulating Pb levels, the types of genetic damage induced by Cr(VI) were different. At low levels of circulating Pb (<30.80 μg/L), chromate mainly caused changes in 8-OHdG, while at high circulating Pb levels (≥44.88 μg/L), chromate induced alterations in MNF. The findings suggested that chromate exposure could cause multiple types of genetic damage, and circulating Pb might modify the association between circulating Cr and the form of genetic damage.

Changes in thyroid hormone related proteins and gene expression induced by polychlorinated biphenyls and halogen flame retardants exposure of children in a Chinese e-waste recycling area

Polychlorinated biphenyls (PCBs) and halogen flame retardants (HFRs) are major pollutants in e-waste recycling area. High internal exposure levels of PCBs and HFRs are harmful to human thyroid hormone (TH) equilibrium. To examine their disrupting effects on TH, we conducted a study on children (n = 114) of an e-waste recycling and a control area in South China. Concentrations of PCBs, HFRs, and TH levels were determined in serum samples. TH related proteins and their corresponding gene were also monitored as markers of such disruption. Levels of these chemicals in the exposed group were much greater than those in the control group. Results of the linear regression and generalized additive model indicated the presence of close relationships between the internal exposure levels and the responses of TH related proteins, gene expression. More extensive exposure concentrations of these chemicals led to higher expression of iodothyronine deiodinase I and decreased the concentrations of thyroid-stimulating hormone, expression of TH receptor α, indicating the exertion of discrepant and even contrary influences on equilibrium of TH, and a compensation of these mechanisms may kept the homeostasis of TH. These results for children warrant further investigation on the health risks of PCBs and HFRs exposure in e-waste area.

Umbilical cord serum PBDE concentrations and child adiposity measures at 7 years

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) exist extensively in the environment. Toxicological studies suggested PBDEs may interfere with adipogenic pathways. However, few human evidence addressed PBDE exposures in utero related to childhood adiposity.

OBJECTIVE

We assessed associations between PBDEs concentrations in cord serum and childhood adiposity measures at 7 years.

METHODS

Among 318 mother-child pairs from Sheyang Mini Birth Cohort Study (SMBCS) in China, nine PBDE congener concentrations were quantified in umbilical cord serum using gas chromatography-negative chemical ionization mass spectrometry (GC-NCI-MS). Anthropometric indicators of children aged 7 years were measured, including weight, height and waist circumference. Age and sex-specific body mass index (BMI) z scores were calculated based on World Health Organization (WHO)'s child growth standards. Multivariate linear and logistic regression models adjusted for putative confounders were performed to examine associations between PBDE congeners and adiposity parameters.

RESULTS

BDE-209 was the most abundant congener of PBDEs with a median value of 19.5 ng/g lipid. The geometric mean values of nine PBDE congeners ranged from below limit of detection (LOD) to 18.1 ng/g lipid, and the detection rates were 46.5%~96.5%. Cord serum BDE-153 and BDE-154 concentrations were associated with lower childhood BMI z score (regression coefficient, β=-0.15, 95% confidence interval: -0.29, -0.02; p=0.02; β=-0.23, 95%CI: -0.43, -0.03; p=0.03, respectively) and lower waist circumference (β=-0.75 cm, 95%CI: -1.43, -0.06; p=0.03; β=-1.22 cm, 95%CI: -2.23, -0.21; p=0.02, respectively), after controlling for potential confounders. Moreover, prenatal BDE-154 exposure was related to a decreased obesity risk of children aged 7 years (odds ratio, OR=0.46, 95%CI: 0.22, 0.94; p=0.03). These effects were only observed among boys in sex-straitified analyses.

CONCLUSIONS

Cord serum BDE-153 and BDE-154 concentrations were related to reduced adiposity measures at 7 years of age. Further evidence regarding the impacts of prenatal PBDE exposures on childhood development is warranted.

Exposure pathways, levels and toxicity of polybrominated diphenyl ethers in humans: A review

Polybrominated diphenyl ethers (PBDEs) are extensively used as brominated flame retardants (BFRs) in different types of materials, which have been listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention in 2009 and 2017. Due to their ubiquities in the environment and toxicities, PBDEs have posed great threat to both human health and ecosystems. The aim of this review is to offer a comprehensive understanding of the exposure pathways, levels and trends and associated health risks of PBDEs in human body in a global scale. We systematically reviewed and described the scientific data of PBDE researches worldwide from 2010 to March 2020, focusing on the following three areas: (1) sources and human external exposure pathways of PBDEs; (2) PBDE levels and trends in humans; (3) human data of PBDEs toxicity. Dietary intake and dust ingestion are dominant human exposure pathways. PBDEs were widely detected in human samples, especially in human serum and human milk. Data showed that PBDEs are generally declining in human samples worldwide as a result of their phasing out. Due to the common use of PBDEs, their levels in humans from the USA were generally higher than that in other countries. High concentrations of PBDEs have been detected in humans from PBDE production regions and e-waste recycling sites. BDE-47, -153 and -99 were proved to be the primary congeners in humans. Human toxicity data demonstrated that PBDEs have extensively endocrine disruption effects, developmental effects, and carcinogenic effects among different populations.

Metabolomic insights into the lasting impacts of early-life exposure to BDE-47 in mice

Early-life exposure to toxicants may have lasting effects that adversely impact later development. Thus, although the production and use of a toxicant have been banned, the risk to previously exposed individuals may continue. BDE-47, a component of commercial penta-BDEs, is a persistent organic pollutant with demonstrated neurotoxicity. To investigate the persistent effects of BDE-47 and the mechanisms thereof, we employed a metabolomics approach to analyze the brain, blood and urine of mice exposed to BDE-47 for 28 days and then 3 months post-exposure. In the brain, BDE-47 was detectable just after exposure but was below the limit of detection (LOD) 3 months later. However, the metabolomic alterations caused by early-life exposure to BDE-47 persisted. Potential biomarkers related to these alterations included phosphatidylcholine, lysophosphatidylcholine, sphingomyelin and several amino acids and biogenic amines. The metabolic pathways involved in the response to BDE-47 in the brain were mainly those related to glycerophospholipid metabolism, sphingomyelin metabolism and neurotransmitter regulation. Thus, our study demonstrates the utility of metabolomics, as the omics most closely reflecting the phenotype, in exploring the mechanisms underlying the lasting effects induced by early-life BDE-47 exposure.

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.

Polybrominated diphenyl ethers in the environment and human external and internal exposure in China: A review

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants. Because of their toxicity and persistence, some PBDEs were restricted under the Stockholm Convention in 2009. Since then, many studies have been carried out on PBDEs in China and in many other countries. In the present review, the occurrences and contamination of PBDEs in air, water, sediment, soil, biota and daily food, human blood, hair, and other human tissues in China are comprehensively reviewed and described. The human exposure pathways and associated health risks of PBDEs are summarized. The data showed no obvious differences between North and South China, but concentrations from West China were generally lower than in East China, which can be mainly attributed to the production and widespread use of PBDEs in eastern regions. High levels of PBDEs were generally observed in the PBDE production facilities (e.g., Jiangsu Province and Shandong Province, East China) and e-waste recycling sites (Taizhou City, Zhejiang Province, East China, and Guiyu City and Qingyuan City, both located in Guangdong Province, South China) and large cities, whereas low levels were detected in rural and less-developed areas, especially in remote regions such as the Tibetan Plateau. Deca-BDE is generally the major congener. Existing problems for PBDE investigations in China are revealed, and further studies are also discussed and anticipated. In particular, non-invasive matrices such as hair should be more thoroughly studied; more accurate estimations of human exposure and health risks should be performed, such as adding bioaccessibility or bioavailability to human exposure assessments; and the degradation products and metabolites of PBDEs in human bodies should receive more attention. More investigations should be carried out to evaluate the quantitative relationships between internal and external exposure so as to provide a scientific basis for ensuring human health.

Typical halogenated flame retardants affect human neural stem cell gene expression during proliferation and differentiation via glycogen synthase kinase 3 beta and T3 signaling

2',2',4,4'-tetrabromo diphenyl ether (BDE-47), one of the most abundant congeners of commercial pentaBDE utilized as flame retardants, has been phased out of production due to its potential neural toxicity and endocrine disrupting activities, and yet still present in the environment. Several alternatives to BDE-47, including tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), tetrachlorobisphenol A (TCBPA) and decabromodiphenyl ether (BDE-209), are presently employed without restrictions and their potential toxic effects on human neural development are still unclear. In this study, we utilized a human neural stem cell (hNSC)-based system to evaluate the potential developmental neurotoxic effects of the above-mentioned five chemicals, at environment and human exposure relevant concentrations. We found that those compounds slightly altered the expression of hNSC identity markers (SOX2, SOX3 and NES), without impairing cell viability or proliferation, in part by either modulating glycogen synthase kinase 3 beta (GSK3β) signaling (TBBPS, TCBPA and BDE-47), and slightly disturbing the NOTCH pathway (TBBPA, TBBPS and TCBPA). Moreover, the five chemicals seemed to alter hNSC differentiation by perturbing triiodothyronine (T3) cellular signaling. Thus, our findings suggest that the five compounds, especially TBBPS, TCBPA, and BDE-47, may affect hNSC self-renewal and differentiation abilities and potentially elicit neural developmental toxicity.

Association of blood chromium and rare earth elements with the risk of DNA damage in chromate exposed population

Pollution of heavy metals often occurs in combination with multiple metal ions. Whether the genetic damage among chromate exposed population correlated with rare earth elements (REEs) was still not well elucidated. A total of 291 participants from a chromate production plant were recruited in the present study. The DNA oxidative damage was evaluated by urinary 8-hydroxydeoxyguanosine (8-OHdG) and the concentrations of chromium (Cr) and 15 REEs accumulated in the peripheral blood of participants were determined. The results showed that significant DNA oxidative damage was observed in chromate exposed workers. Blood REEs levels in the exposed group were significantly higher than the control group and blood REEs increased in a concentration dependent manner with Cr. Additionally, significant correlations were observed between blood Cr and 10 REEs concentrations. Blood Cr had a significant positive correlation with urinary 8-OHdG. Blood Cr and Yttrium had a positive interactive effect on urinary 8-OHdG. Collectively, the results suggested workers who had been working in the chromate plant were simultaneously exposed to chromate and a variety of REEs, which could have interactive effects on the DNA damage of workers.

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.

4-Bromodiphenyl Ether Causes Adrenal Gland Dysfunction in Rats during Puberty

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants with two or more bromines attached. They are endocrine disruptors. PBDEs photodegrade into 4-bromodiphenyl ether (BDE3). Whether BDE3 impairs adrenal cortical cell function during postnatal development still remains unknown. The aim of the current study was to investigate the influence of BDE3 on adrenal cortical cell function. Sprague-Dawley rats (35 days of age, male) were orally administered with BDE3 (0, 50, 100, and 200 mg/kg/day body weight) for 21 days. BDE3 significantly increased serum aldosterone and corticosterone levels at 200 mg/kg without affecting adrenocorticotropic hormone level. Further study showed that BDE3 up-regulated Cyp11b1 at 100 and 200 mg/kg and Scarb1, Star, Cyp11b2, Cyp21, and Nr5a1 mRNA levels in the 200 mg/kg group. BDE3 also decreased the phosphorylation of AMP-activated protein kinase (AMPK) at 200 mg/kg and increased PGC-1α and phosphorylated cyclic AMP-responsive element-binding protein (CREB)/CREB at 200 mg/kg. Taken together, these findings demonstrate that BDE3 stimulates adrenal cell function likely through decreasing phosphorylation of AMPK and increasing phosphorylation of CREB.

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.

2,2',4,4'-tetrabromodiphenyl ether induces germ cell apoptosis through oxidative stress by a MAPK-mediated p53-independent pathway

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a representative congener of polybrominated diphenyl ethers in the environment, is known to have reproductive toxicity. However, the underlying mechanisms remain to be clarified, especially in in vivo systems. In the present study, we employed Caenorhabditis elegans to study the effects of BDE-47 on reproduction. Our results showed that BDE-47 impaired worm fecundity and induced germ cell apoptosis. To elucidate the mechanisms, DNA damage and oxidative stress induction were investigated by determining the numbers of foci formation in transgenic worms expressing HUS-1::GFP and the levels of reactive oxygen species, respectively. We found that BDE-47 induced oxidative stress but not DNA damage, and treatment with the antioxidant, N-acetyl-L-cysteine, completely abrogated BDE-47-induced germ cell apoptosis. In addition, the apoptosis was blocked in mutants carrying mek-1, sek-1 or abl-1 loss-of-function alleles, but not in the p53/cep-1 deficient worms, suggesting that the mitogen-activated protein kinase (MAPK) signaling cascade was essential for BDE-47-induced germ cell apoptosis and p53/cep-1 was not required. Moreover, the apoptosis in the strains deficient for DNA damage response was not suppressed under BDE-47 treatment. Overall, we demonstrated that BDE-47 could induce oxidative stress and subsequent germ cell apoptosis in Caenorhabditis elegans through a MAPK-mediated p53-independent pathway.

The Role of Polybrominated Diphenyl Ethers in Thyroid Carcinogenesis: Is It a Weak Hypothesis or a Hidden Reality? From Facts to New Perspectives

In the last decades, the incidence of thyroid cancer has increased faster than that of any other malignant tumor type. The cause of thyroid cancer is likely multifactorial and a variety of both exogenous and endogenous has been identified as potential risk factors. Polybrominated diphenyl ethers (PBDEs), used since the 1970s as flame retardants, are still widespread and persistent pollutants today, although their production was definitely phased out in the western countries several years ago. Polybrominated diphenyl ethers are known endocrine disruptors, and the endocrine system is their primary target. Whereas animal studies have ascertained the ability of PBDEs to affect the normal functionality of the thyroid, evidence in humans remains inconclusive, and only a few epidemiological studies investigated the association between exposure to PBDEs and thyroid cancer. However, a number of clues suggest that a prolonged exposure to these chemicals might act a trigger of the most common malignancy of the endocrine system, whereas further studies with an advanced design are suggested.