Occupational exposure to polybrominated diphenyl ethers or decabromodiphenyl ethane during chemical manufacturing: Occurrence and health risk assessment

Mechanistic and kinetic insights into the thermal degradation of decabromodiphenyl ethane

Decabromodiphenyl ethane (DBDPE), as one of the important new brominated flame retardants, is widely utilized in a variety of plastic products. However, the pyrolysis mechanism of DBDPE remains uncertain. In this article, the evolution behavior of the main products during the thermal decomposition of DBDPE is investigated using density functional theory at the theoretical level of M06-2X/6-311++G(2df,p)//M06-2X/6-311+G(d). The results show that the initial reaction starts with the cleavage of the ethane bridge bond, with an absorbed heat value of 298 kJ/mol, and the cleavage of the Caromatic-Br bond generates bromine radical, which is the main competitive reaction, with a heat absorption of 317 kJ/mol. The initial degradation of DBDPE generates a large number of pentabromobenzyl radicals and bromine radicals, which facilitate the secondary pyrolysis of DBDPE to a certain extent, resulting in the formation of possible products such as pentabromobenzyl bromide, pentabromobenzene, pentabromotoluene, hexabromobenzene, pentabromostyrene, and hydrogen bromide. In the pyrolysis system of DBDPE with hydrogen radicals, the reactions are classified into two types: extraction reaction and addition reaction. It can be known that the addition reaction plays a dominant role in the degradation process, with a branching ratio of 89.8% at 1600 K. The degradation of DBDPE with hydrogen radicals is mainly characterized by debromination, and the main products are hydrogen bromide, low-brominated diphenyl ethanes, brominated phenanthrenes, and brominated monoaromatic compounds. In addition, the lowest reaction energy barrier (18 kJ/mol) is required for the addition of hydrogen radical to the ipso-C site of DBDPE. DBDPE is dangerous for the environment and humans since its fate includes bioaccumulation, biomagnification, and toxicity via hormones and endocrine disruptors.

The seed germination and seedling phytotoxicity of decabromodiphenyl ethane to tall fescue under citric acid amendment

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has biological toxicity, persistence, long-range migration and bioaccumulation ability. However, there is currently little research on the phytotoxicity of DBDPE in plants. The perennial herbaceous plant tall fescue (Festuca elata Keng ex E. B. Alexeev) was selected as the model organism for use in seed germination experiments, and the phytotoxicity of DBDPE in the soil of tall fescue was studied. The results indicated that DBDPE had a significant effect on the germination and growth of tall fescue seedlings. Citric acid reduced the stress caused by DBDPE in plants, effectively alleviating the phytotoxicity of DBDPE in tall fescue. The root vitality and protein content significantly increased after the application of citric acid, increasing by 74.93-183.90%, 146.44-147.67%, respectively. The contents of proline and soluble sugars significantly decreased after the application of citric acid, decreasing by 45.18-59.69% and 23.03%, respectively (P < 0.05). There was no significant difference in superoxide dismutase (SOD) or peroxidase (POD) activity in tall fescue seedlings, and the catalase (CAT) activity and malondialdehyde (MDA) content were significantly lower after the application of citric acid, decreasing by 64.62-67.91% and 29.10-49.80%, respectively (P < 0.05). Tall fescue seedlings bioaccumulated DBDPE, with biological concentration factors (BCFs) ranging from 4.28 to 18.38 and transfer factors (TFs) ranging from 0.43 to 0.54. This study provides theoretical support for the study of the toxicity of DBDPE to plants and offers a research foundation for exploring the phytoremediation of DBDPE-contaminated soil by tall fescue.

Biomarkers of Organophosphate and Polybrominated Diphenyl Ether (PBDE) Flame Retardants of American Workers and Associations with Inhalation and Dermal Exposures

This study evaluated workers' exposures to flame retardants, including polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs), and other brominated flame retardants (BFRs), in various industries. The study aimed to characterize OPE metabolite urinary concentrations and PBDE serum concentrations among workers from different industries, compare these concentrations between industries and the general population, and evaluate the likely route of exposure (dermal or inhalation). The results showed that workers from chemical manufacturing had significantly higher (p <0.05) urinary concentrations of OPE metabolites compared to other industries. Spray polyurethane foam workers had significantly higher (p <0.05) urinary concentrations of bis(1-chloro-2-propyl) phosphate (BCPP) compared to other industries. Electronic scrap workers had higher serum concentrations of certain PBDE congeners compared to the general population. Correlations were observed between hand wipe samples and air samples containing specific flame-retardant parent chemicals and urinary metabolite concentrations for some industries, suggesting both dermal absorption and inhalation as primary routes of exposure for OPEs. Overall, this study provides insights into occupational exposure to flame retardants in different industries and highlights the need for further research on emerging flame retardants and exposure reduction interventions.

Emission and gas-particle partitioning characteristics of atmospheric halogenated and organophosphorus flame retardants in decabromodiphenyl ethane-manufacturing functional areas

The emission and gas-particle partitioning characteristics in various functional areas of production lines are still unknown. However, flame-retardant manufacturing activities are the primary emission source of flame retardants. Thus, fine particles and gases were investigated in three functional areas of a decabromodiphenyl ethane production line, i.e., polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), dechlorane plus (DPs), and organophosphorus flame retardants (OPFRs) in a flame-retardant manufacturing factory. High levels of PBDEs (8.02 × 10³-4.16 × 10⁴ pg/m³), NBFRs (6.05 × 10³-1.92 × 10⁵ pg/m³), and DPs (89.5-5.20 × 10³ pg/m³) were found in various functional areas, suggesting manufacturing activities were a primary emission source. In contrast, OPFRs were derived from long-range transport or other non-industrial sources. Varied concentrations of PBDEs, NBFRs, and DPs were observed in different production lines, higher in the reaction zone area than others. As the predominant compounds, decabromodiphenyl ether, decabromodiphenyl ethane, syn-DP, and tris(chloropropyl) phosphate accounted for 54.7%, 89.3%, 93.4%, and 34.7% of PBDEs, NBFRs, DPs, and OPFRs, respectively. Three models were used to predict the gas-particle partitioning of the halogenated flame retardants emitted from manufacturing activities. The Li-Jia Empirical Model predicted the gas-particle partitioning behavior well. This research shows that the adsorption-desorption process of the halogenated flame retardants between the gaseous and particulate phases did not reach equilibrium.

Occurrence of some legacy and emerging contaminants in feed and food and their ranking priorities for human exposure

The "feed-to-food" pathway is one of the most important routes for human exposure to manmade contaminants. The contaminants could threaten human health through the "feed-to-food" route and have recently become of great public concern. This review selects the representative legacy and emerging contaminants (ECs), such as polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate esters (OPEs), short-chain chlorinated paraffins (SCCPs), and per- and polyfluoroalkyl substances (PFASs), regarding their occurrence in feed and food, as well as their metabolites and transport in farming and livestock ecosystems. Factors that might influence their presence and behavior are discussed. This review raises an approach to rank the priority of ECs using the EC concentrations in feed and food and using the hazard quotient (HQ) method for human health. Although SCCPs have the highest levels in feed and food, their potential risks appear to be the lowest. PFASs have the highest HQs on account of human exposure risk. Future research should pay more attention to the combined effects of multiple ECs.

DBDPE and ZnO NPs synergistically induce neurotoxicity of SK-N-SH cells and activate mitochondrial apoptosis signaling pathway and Nrf2-mediated antioxidant pathway

Decabromodiphenyl ethane (DBDPE), a new brominated flame retardant, could negatively affect neurobehavior and pose health risks to humans. Humans are also exposed to widely used nanomaterials. This study investigated the combined toxic effects and action types of DBDPE and Zinc oxide nanoparticles (ZnO NPs) on human neuroblastoma SK-N-SH cells and the toxicity mechanisms. DBDPE inhibited the viability of SK-N-SH cells by 21.87% at 25 mg/L. ZnO NPs synergistically exacerbated the toxic effects of DBDPE. DBDPE and ZnO NPs caused excessive ROS production and inhibition of antioxidant enzyme (SOD and GSH) activity in cells, thus causing oxidative cellular damage. Moreover, DBDPE and ZnO NPs caused apoptosis by disrupting mitochondrial kinetic homeostasis, reducing mitochondrial membrane potential (MMP), increasing cytochrome C release and regulating Bax/Bcl-2 and Caspase-3 mRNA and protein expression. DBDPE and ZnO NPs increased the mRNA expression of nuclear factor erythroid 2- related factor (Nrf2) and its downstream genes. The molecular mechanisms revealed that oxidative stress, apoptosis and mitochondrial dysfunction were the critical factors in combined cytotoxicity. The bioinformatics analysis further indicated that co-exposure affected Nrf2 activation, apoptotic factors expression and mitochondrial fusion. The findings enrich the risk perception of neurotoxicity caused by DBDPE and ZnO NPs.

Placental transfer of bisphenol diglycidyl ethers (BDGEs) and its association with maternal health in a population in South of China

Despite high production and usage, little is known about exposure to bisphenol diglycidyl ethers (BDGEs) and their derivatives in pregnant women and fetuses. In this study, we determined nine BDGEs in 106 paired maternal and cord serum samples collected from e-waste dismantling sites in South of China. Bisphenol A bis (2,3-dihydroxypropyl) glycidyl ether (BADGE·2H2O), bisphenol A (3-chloro-2-hydroxypropyl) (2,3-dihydroxypropyl) glycidyl ether (BADGE·HCl·H2O), and bisphenol F diglycidyl ether (BFDGE) were the major BDGEs, with median concentrations of 0.57, 4.07, and 1.60 ng/mL, respectively, in maternal serum, and of 3.58, 5.61, and 0.61 ng/mL, respectively, in cord serum. The transplacental transfer efficiencies (TTEs) were estimated for BDGEs found in samples, and median values were in the range of 0.98 (BFDGE) to 5.91 (BADGE·2H2O). Our results suggested that passive diffusion plays a role in the placental transfer of BADGE·HCl·H2O and BFDGE, whereas several mechanisms contribute to the high accumulation of BADGE·2H2O in cord serum. Multiple linear regression analysis indicated significant associations between maternal serum concentrations of BDGEs and blood clinical biomarkers, especially those related to liver injuries, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and adenosine deaminase (ADA) (P < 0.05). To our knowledge, this is the first study to report the occurrence of BDGEs in paired maternal-fetal serum samples and provide new insights into prenatal and fetal exposures. The newly discovered TTEs in maternal-fetal pairs contribute to a fuller inventory of the transmission activity of pollutants in the human body, ultimately adding to a more significant comprehensive risk evaluation.

Decabromodiphenyl ethane induces locomotion neurotoxicity and potential Alzheimer's disease risks through intensifying amyloid-beta deposition by inhibiting transthyretin/transthyretin-like proteins

As a major alternative to traditional brominated flame retardants (BFRs), decabromodiphenyl ethane (DBDPE) is widely used and has been commonly detected in various environmental media and organisms. Few previous studies have focused on DBDPE-induced locomotion neurotoxicity, and the exact molecular mechanisms and related health risks remain unclear. In this study, we first analyzed the locomotion indicators of nematodes following DBDPE exposure, demonstrated that DBDPE caused locomotion neurotoxicity, and identified that a series of the transthyretin (TTR)-like genes participated in the regulation of nematode motility by transcriptomic analysis, gene transcription validation and TTR-like mutant verification. Subsequently, this study demonstrated that DBDPE exacerbated amyloid-beta (Aβ) deposition by repressing TTR/TTR-like gene transcription based on Alzheimer's disease (AD) model nematodes and human SH-SY5Y cells following DBDPE exposure and further revealed that DBDPE reduced the binding between TTR and Aβ by competing with the strand G region sites on the TTR/TTR-like protein, ultimately exacerbating Aβ deposition and the risk of AD. In short, our study demonstrated that DBDPE induced locomotion neurotoxicity and potential AD risks through intensifying Aβ deposition by inhibiting TTR/TTR-like proteins, providing reference support for risk management and policy formulation related to DBDPE and similarly structured novel BFRs.

Physiologically based pharmacokinetic (PBPK) modeling of BDE-209 following oral exposure in Chinese population

The wide usage of decabromodiphenyl ether (BDE-209) as additive brominated flame retardant has caused its widespread occurrence in the environment and high exposure risk in humans. Estimating its internal exposure dose and reconstruction of external exposure dose using physiologically based pharmacokinetic (PBPK) modelling approach is a key step in the risk assessment of BDE-209. However, the PBPK model for BDE-209 is currently unavailable. This study has established two oral permeability-limited PBPK models of BDE-209 without enterohepatic recirculation (EHR) (model 1) and with EHR (model 2) for Chinese population. Using the in vitro experiments, the average binding of BDE-209 to human plasma protein (99.64% ± 2.97%) was obtained. Moreover, blood sample analysis and systematic literature review were performed to obtain internal and external exposure data of BDE-209 used for model calibration and validation. The predictions of both models were within 2-fold of the observed, and a longer half-life of serum BDE-209 was observed in model 2 than model 1. Based on the models, a human biomonitoring guidance value (HBM-GV) of 93.61 μg/g lw was derived for BDE-209, and there is no health risk found for Chinese population currently. This study provides new quantitative assessment tools for health risk assessment of BDE-209.

New Insights into Human Biotransformation of BDE-209: Unique Occurrence of Metabolites of Ortho-Substituted Hydroxylated Higher Brominated Diphenyl Ethers in the Serum of e-Waste Dismantlers

Extremely high levels of decabromodiphenyl ether (BDE-209) are frequently found in the serum of occupationally exposed groups, such as e-waste dismantlers and firefighters. However, the metabolism of BDE-209 in the human body is not adequately studied. In this study, 24 serum samples were collected from workers at a typical e-waste recycling workshop in Taizhou, Eastern China, and the occurrence and fate of these higher brominated diphenyl ethers (PBDEs) were investigated. The median concentration of the total PBDEs in the serum was 199 ng/g lipid weight (lw), ranging from 125 to 622 ng/g lw. Higher brominated octa- to deca-BDEs accounted for more than 80% of the total PBDEs. Three ortho-hydroxylated metabolites of PBDEs─6-OH-BDE196, 6-OH-BDE199, and 6'-OH-BDE206─were widely detected with a total concentration (median) of 92.7 ng/g lw. The concentrations of the three OH-PBDEs were significantly higher than their octa- and nona-PBDE homologues, even exceeding those of the total PBDEs in several samples, indicating that the formation of OH-PBDEs was a major metabolic pathway of the higher brominated PBDEs in occupationally exposed workers. An almost linear correlation between 6-OH-BDE196 and 6-OH-BDE199 (R = 0.971, P < 0.001) indicates that they might undergo a similar biotransformation pathway in the human body or may be derived from the same precursor. In addition, the occurrence of a series of penta- to hepta- ortho-substituted OH-PBDEs was preliminarily identified according to their unique "predioxin" mass spectral profiles by GC-ECNI-MS. Taken together, the tentative metabolic pathway for BDE-209 in e-waste dismantlers was proposed. The oxidative metabolism of BDE-209 was mainly observed at the ortho positions to form 6'-OH-BDE-206, which later underwent a consecutive loss of bromine atoms at the meta or para positions to generate other ortho-OH-PBDEs. Further studies are urgently needed to identify the chemical structures of these ortho-OH-PBDE metabolites, and perhaps more importantly to clarify the potentially toxic effects, along with their underlying molecular mechanisms.

Reduced mitochondrial DNA copy number in occupational workers from brominated flame retardants manufacturing plants

Decabrominated diphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are two flame retardants that have similar structure and are widely used in various industrial products. The accumulation and potential toxicity of them to human health have already aroused attention, and some research showed that they may affect mitochondrial function. Therefore, this study focused on the population with high exposure to brominated flame retardants (BFRs) and the related changes in mtDNA copy number (mtDNAcn) in whole blood. 334 blood samples were collected from three groups of people in Shandong Province, including 42 BDE-209 occupational exposure workers from the BDE-209 manufacturing plant, 131 DBDPE occupational exposure workers from the DBDPE manufacturing plant, and 161 non-BFRs occupational exposure residents from the BFRs contaminated area. We measured the levels of BDE-209, DBDPE in serum sample, and the mtDNAcn in whole blood sample and analyzed these data by multiple linear regression. The average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in BDE-209 occupational workers were 3510, 639 and 4600 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in DBDPE occupational workers were 229, 4040 and 4470 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in non-BFRs occupational exposure residents were 66.3, 45.7 and 137 ng/g lw, respectively. The relative mtDNAcn was 0.823 in BDE-209 occupational workers, 0.845 in DBDPE occupational workers and 0.989 in non-BFRs occupational exposure residents. A 10-fold increase in BDE-209, DBDPE concentrations was separately associated with a 0.068 and 0.063 decrease in mtDNAcn. Therefore, our study implied that BFRs may affect mitochondrial function. As increasing BFRs exposure has emerged in recent years, the relationship between BFRs exposure and mitochondrial function needs further study.

High-fat diet exacerbated decabromodiphenyl ether-induced hepatocyte apoptosis via intensifying the transfer of Ca2+ from endoplasmic reticulum to mitochondria

Polybrominated diphenyl ether (PBDE) as the flame retardant is heavily used in daily necessities, causing adverse health effects on humans. This study aimed to evaluate the hepatotoxicity of decabromodiphenyl ether (BDE-209), the most widely used PBDE, in lean and high-fat diet (HFD)-treated obese mice and elucidate the underlying mechanism. Firstly, the increasing levels of TG and proinflammatory factors in the liver and ALT and AST in serum demonstrated the hepatic damage caused by BDE-209 and further exacerbated by HFD. Tunel image revealed that BDE-209 induced more severe hepatocyte apoptosis with the assistant of HFD. Next, the mechanism analysis showed that the pro-apoptotic action of BDE-209 was in an endoplasmic reticulum (ER)/Ca²⁺ flux/mitochondria-dependent manner, concluded from the impairment of mitochondrial membrane potential, the enhancive protein expression of p-PERK/PERK, p-IRE1/IRE1, ATF6, CHOP, Bax/Bcl-2, cleaved caspase-3/caspase-3, IP3R1 and Sig-1R, and the over-transfer of Ca²⁺ from ER to mitochondria. Such proposed mechanism was further confirmed by the IP3R1 siRNA transfection cell experiment, where apoptotic rate was reduced in parallel with the reduced mitochondrial Ca²⁺ level. Finally, the higher expression of PACS-2 protein and the expanded ER contributed to the enriched ER-mitochondria interaction, reflected by the closer distance between ER and mitochondria visually displayed in the TEM image in HFD groups. This change was conducive to the rapid delivery of apoptosis signals via Ca²⁺, as proven, mechanically explaining the strengthening effect of HFD on BDE-209 hepatotoxicity. These findings detailedly explained the mechanism of BDE-209 hepatotoxicity and clarified the auxiliary effect of HFD, providing a theoretical basis for further studying other analogs.

Ensuring the reliability of brominated flame retardant data on food and feed occurrence through harmonised analytical criteria and proficiency testing

The volume of occurrence data on food and animal feed contaminants such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDDs) is slowly increasing as more laboratories develop analytical capability. This data allows an evaluation of current background levels in different countries and regions and is also useful for estimating the health risk through dietary exposure and as evidence for the formulation of future control strategies. Existing data varies in the number of analytes reported and the quality measures applied. In order to ensure reliability and comparability, guidance on analytical criteria such as precision and trueness, limits of quantitation, recovery, positive identification, etc. is provided. These parameters are based on several years of collective experience and allow validation and regular quality control of analysis of individual PBDE congeners and HBCDD stereoisomers. The criteria-based approach also allows laboratories the flexibility to use different analytical methodologies and techniques for generating data. The effectiveness of this approach has been demonstrated by a successful proficiency testing scheme that has been used for a number of years and has attracted an increasing number of participants. The majority of participating laboratories (>80%) have been able to demonstrate performance within the 95% confidence interval (│z-score│≤ 2) and a further 10% of laboratories demonstrated performance with a z-score of (2 <│z-score│< 3). The combined support of these guidance criteria backed by successful proficiency testing will ensure the reliability and comparability of results, in particular, to refine risk assessments and to help the formulation of regulatory policy.

The combined impact of decabromodiphenyl ether and high fat exposure on non-alcoholic fatty liver disease in vivo and in vitro

Non-alcoholic fatty liver disease (NAFLD) is considered a public health concern. Decabromodiphenyl ether (BDE-209) and high fat (HF) exposure cause liver injury, yet the combined impact on NAFLD development remains unclear. HepG2 cells were incubated with BDE-209 or/and HF reagent (C_{sodium oleate}/C_{sodium palmitate} = 2/1) for establishing the in vitro model, while C57BL/6 mice fed BDE-209 or/and HF diet (HFD) was the in vivo model. Oil Red O staining and the determination of triglyceride, malondialdehyde, and reactive oxygen species (ROS) contents proved the elevated lipid accumulation and oxidative stress by the mixture of BDE-209 and HF in HepG2 cells, consistent in C57BL/6 mice. Importantly, the action analysis showed the synergistic effect between BDE-209 and HF, suggesting that the population preferring the HFD is more susceptible to BDE-209 to aggravate the progression of NAFLD. Further, the increased protein expression of sterol regulatory element-binding protein 1, fatty acid synthase, and stearoyl-CoA desaturase 1 was considered to be responsible for hepatic steatosis. The impairment of antioxidant system was reflected by the lower hepatic superoxide dismutase and glutathione transferase activities and reduced glutathione level, explaining the detected excessive ROS production. Besides, using high content analysis, the decline of mitochondrial mass and membrane potential, which was closed to the NAFLD pathogenesis, was also demonstrated in HepG2 cells.

Worker health risk of heavy metals in pellets of recycled plastic: a skin exposure model

OBJECTIVE

According to epidemiological studies, heavy metals such as arsenic, cadmium, chromium, and lead are "known" carcinogenic substances. After recycling, these metals remain in processed plastics. The purpose of this study was to assess the health risks of heavy metal skin exposure to workers in facilities that recycle plastics.

METHODS

We used inductively coupled plasma-mass spectrometry to measure the dissolution concentrations of heavy metals in artificial sweat. Twenty-five samples of pellets of recycled plastic were examined, which were composed variously of polypropylene, high-density polyethylene, acrylonitrile-butadiene-styrene copolymer, high impact polystyrene, and polyamide. In addition, we used a "two-step assessment model," divided into exposure and risk characterization, to evaluate the health risks of heavy metal exposure in a simulated exposure environment of pellets of a recycled plastic processing workshop.

RESULTS

Except for chromium (92%), the detection of lead, cadmium and arsenic was 100% in 25 samples of pellets of recycled plastic. The possible carcinogenic risk levels of As and Cr were, respectively, 2 and 38 times greater than the unacceptable risk level of 10^-4 proposed by the US EPA. In addition, arsenic had the highest noncarcinogenic risk of 1.381 × 10^-6, which was in the potential risk range of 10^-6-10^-4 proposed by the US EPA.

CONCLUSION

We found clear exposure-risk associations between heavy metals (lead, cadmium, chromium, arsenic) and worker health. Particularly, we found workers exposed to As and Cr were more likely to incur cancer.

Thyroid hormones in relation to polybrominated diphenyl ether and metals exposure among rural adult residents along the Yangtze River, China

Although several studies indicate that exposure to polybrominated diphenyl ethers (PBDEs) and metals may influence thyroid function, the evidence is limited and inconsistent in general population. The current study was conducted to determine the levels of plasma PBDEs and urinary metals and evaluate the associations of co-exposure to both with thyroid hormones (THs) among rural adult residents along the Yangtze River, China. A total of 329 subjects were included in current analyses, and 8 PBDEs congeners and 14 urinary metals were measured to reflect the levels of environmental exposure. Multiple linear regression models were used to evaluate the association between PBDEs, metals and THs levels. Bayesian Kernel Machine Regression (BKMR) was used to examine PBDEs and metals mixtures in relation to THs. The geometric mean (GM) and 95% confidence interval (CI) of total measured PBDEs was 65.10 (59.96, 70.68) ng/g lipid weights (lw). BDE-209 was the most abundant congener, with a GM (95% CI) of 47.91 (42.95, 53.26) ng/g lw, accounting for 73.6% of the total PBDEs. Free thyroxine (FT4) was significantly negatively associated with BDE-28, 47, 99, 100, 154, and 183, and urinary strontium [β (95% CI): -0.04 (-0.07, -0.02)], but positively associated with selenium [β (95% CI): 0.04 (0.02, 0.06)]. Free triiodothyronine (FT3) was negatively associated with BDE-28 [β (95% CI): -0.03 (-0.05, -0.01)] and urinary arsenic [β (95% CI): -0.01 (-0.02, -0.001)]. The current study did not observe a statistically significant association of thyroid-stimulating hormone (TSH) with PBDEs and urinary metals. BKMR analyses showed similar trends when these chemicals were taken into consideration simultaneously. We found no significant interaction in the association between individual chemical at the 25th versus 75th percentiles and THs estimates, comparing the results when other chemicals were set at their 10th, 50th, and 90th percentile levels. Further study is required to confirm these findings and determine potential mechanisms.

Polybrominated diphenyl ethers in the environmental systems: a review

PBDEs are human-influenced chemicals utilized massively as flame retardants. They are environmentally persistent, not easily degraded, bioaccumulate in the biological tissue of organisms, and bio-magnify across the food web. They can travel over a long distance, with air and water being their possible transport media. They can be transferred to non-target organisms by inhalation, oral ingestion, breastfeeding, or dermal contact. These pollutants adsorb easily to solid matrices due to their lipophilicity and hydrophobicity; thus, sediments from rivers, lakes, estuaries, and ocean are becoming their major reservoirs aquatic environments. They have low acute toxicity, but the effects of interfering with the thyroid hormone metabolism in the endocrine system are long term. Many congeners of PBDEs are considered to pose a danger to humans and the aquatic environment. They have shown the possibility of causing many undesirable effects, together with neurologic, immunological, and reproductive disruptions and possible carcinogenicity in humans. PBDEs have been detected in small amounts in biological samples, including hair, human semen, blood, urine, and breastmilk, and environmental samples such as sediment, soil, sewage sludge, air, biota, fish, mussels, surface water, and wastewater. The congeners prevailing in environmental samples, with soil being the essential matrix, are BDE 47, 99, and 100. BDE 28, 47, 99, 100, 153, 154, and 183 are more frequently detected in human tissues, whereas in sediment and soil, BDE 100 and 183 predominate. Generally, BDE 153 and 154 appear very often across different matrices. However, BDE 209 seems not frequently determined, owing to its tendency to quickly breakdown into smaller congeners. This paper carried out an overview of PBDEs in the environmental, human, and biota niches with their characteristics, physicochemical properties, and fate in the environment, human exposure, and health effects.

Assessment of polybrominated diphenyl ethers and emerging brominated flame retardants in Pheretima (a Traditional Chinese Medicine): Occurrence, residue profiles, and potential health risks

China produces and consumes large quantities of brominated flame retardants (BFRs) as well as several other unregulated electronic waste recycling activities, causing high BFR concentrations in the natural environment. Thus, Traditional Chinese Medicines (TCMs) may be contaminated by legacy BFRs (e.g. polybrominated diphenyl ethers (PBDEs)) and emerging BFRs (eBFRs, such as decabromodiphenyl ethane (DBDPE)) during growth, processing, packaging, and transportation. Pheretima, which is a typical animal drug recorded in Chinese Pharmacopoeia, was used as an example to evaluate human exposure to BFRs through TCM intake. This study is the first to determine 25 PBDEs and 5 eBFRs in Pheretima and estimate the daily BFR intake via Pheretima-containing TCMs. Twenty-seven Shanghai Pheretima and fifty-one Guang Pheretima samples were collected between March and June 2019 in southeast China. High BFR detection frequencies were found in Pheretima, of which BDE-209 and DBDPE were the most predominant analytes. The total PBDE contents ranged from 73 pg/g to 8,725 pg/g, while that of the eBFRs varied between 115 pg/g and 2,824 pg/g. The profiles and abundances were found to be species- and origin-dependent. However, the traditional processing of Pheretima may reduce BFR residues. Based on the usual clinical doses of Pheretima and the available chronic oral reference doses of BDE-47, 99, 153, and 209, the mean (95th percentile) of the total hazard quotient was estimated to be 9.1 × 10^-5 (2.7 × 10^-4). Therefore, there is little risk related to BFR exposure for patients taking formulated Pheretima-containing TCMs. However, it is necessary to establish routine monitoring programs for the co-existence of pollutants in TCMs to perform a systematic and comprehensive risk assessment.

Concentrations of organic contaminants in industrial and municipal bioresources recycled in agriculture in the UK

Many types of bioresource materials are beneficially recycled in agriculture for soil improvement and as alternative bedding materials for livestock, but they also potentially transfer contaminants into plant and animal foods. Representative types of industrial and municipal bioresources were selected to assess the extent of organic chemical contamination, including: (i) land applied materials: treated sewage sludge (biosolids), meat and bone meal ash (MBMA), poultry litter ash (PLA), paper sludge ash (PSA) and compost-like-output (CLO), and (ii) bedding materials: recycled waste wood (RWW), dried paper sludge (DPS), paper sludge ash (PSA) and shredded cardboard. The materials generally contained lower concentrations of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) relative to earlier reports, indicating the decline in environmental emissions of these established contaminants. However, concentrations of polycyclic aromatic hydrocarbons (PAHs) remain elevated in biosolids samples from urban catchments. Polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) were present in larger amounts in biosolids and CLO compared to their chlorinated counterparts and hence are of potentially greater significance in contemporary materials. The presence of non-ortho-polychlorinated biphenyls (PCBs) in DPS was probably due to non-legacy sources of PCBs in paper production. Flame retardent chemicals were one of the most significant and extensive groups of contaminants found in the bioresource materials. Decabromodiphenylether (deca-BDE) was the most abundant polybrominated diphenyl ether (PBDE) and may explain the formation and high concentrations of PBDD/Fs detected. Emerging flame retardant compounds, including: decabromodiphenylethane (DBDPE) and organophosphate flame retardants (OPFRs), were also detected in several of the materials. The profile of perfluoroalkyl substances (PFAS) depended on the type of waste category; perfluoroundecanoic acid (PFUnDA) was the most significant PFAS for DPS, whereas perfluorooctane sulfonate (PFOS) was dominant in biosolids and CLO. The concentrations of polychlorinated alkanes (PCAs) and di-2-ethylhexyl phthalate (DEHP) were generally much larger than the other contaminants measured, indicating that there are major anthropogenic sources of these potentially hazardous chemicals entering the environment. The study results suggest that continued vigilance is required to control emissions and sources of these contaminants to support the beneficial use of secondary bioresource materials.

Decabromodiphenyl ether disturbs hepatic glycolipid metabolism by regulating the PI3K/AKT/GLUT4 and mTOR/PPARγ/RXRα pathway in mice and L02 cells

Decabromodiphenyl ether (BDE-209) is a persistent environmental pollutant that poses great risks to human health and has been associated with glucose and lipid metabolism. However, the mechanisms by which BDE-209 disturbs glycolipid metabolism in the liver remain unclear. Therefore, this study sought to confirm the effects of BDE-209 on glycolipid metabolism in mice livers and L02 cells to elucidate potential mechanisms of action. In vivo BDE-209 exposure caused histological damage and lipid accumulation, elevated glucose, low-density lipoprotein, total cholesterol, and triglyceride levels, and decreased glycogen and high-density lipoprotein levels in mice livers. Moreover, in vitro BDE-209 exposure not only induced L02 cells cytotoxicity (i.e., reduced cell viability and increased LDH leakage and ROS generation) but also increased glucose and triglyceride concentrations in L02 cells. Furthermore, IGF-1, an activator of the PI3K-AKT pathway, markedly inhibited BDE-209-induced glucose concentration increase in L02 cells and antagonized the inhibitory effect of BDE-209 on the PI3K/AKT/GLUT4 pathway by counteracting the changes in the expression levels of p-IRS, AKT, PI3K, p-AKT, and GLUT4. Moreover, GW9662, a PPARγ inhibitor, blocked lipid accumulation and the upregulation of the mTOR/PPARγ/RXRα pathway in L02 cells induced by BDE-209 by relieving the increases in p-mTOR, PPARγ, and RXRα protein expression levels. In summary, this study revealed that BDE-209 disrupted glycolipid metabolism by inhibiting the PI3K/AKT/GLUT4 pathway and activating the mTOR/PPARγ/RXRα pathway.

Polybrominated dibenzo-p-dioxins and furans (PBDD/Fs): Contamination in food, humans and dietary exposure

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) have been recognised as environmental pollutants for decades but their occurrence in food has only recently been reported. They elicit the same type of toxic response as analogous polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) with similar potencies and effects, and share similar origins - inadvertent production during combustion and occurrence as by-products in industrial chemicals. Surprisingly, PBDD/Fs have received considerably less attention than PCDD/Fs, perhaps because determination requires a higher degree of analytical competence, a result of the higher adsorptivity and lability associated with carbon-bromine bonding. For most populations, the principal exposure pathway is dietary intake. The PBDD/F toxicity arising from occurrence in foods has often been expressed as toxic equivalents (TEQs) using the same scheme developed for PCDD/Fs. This approach is convenient, but resulting TEQ estimates are more uncertain, given the known differences in response for some analogous congeners and also the different patterns of PBDD/F occurrence confirmed by the newer data. Further studies to consolidate potency factors would help to refine TEQ estimates. Characteristically, most foods and human tissues show more frequent and higher PBDF concentrations relative to PBDDs, reflecting major source patterns. Occurrence in food ranges from <0.01 to several thousand pg/g (or up to 0.3 pg TEQ/g whole weight) which is comparable to PCDD/F occurrence (ΣPBDD/F TEQs are underestimated as not all relevant congeners are included). Plant based foods show higher PBDD/F: PCDD/F TEQ ratios. Reported PBDD/F dietary intakes suggest that some population groups, particularly young children, may exceed the revised tolerable weekly intake for dioxin-like contaminants (2 pg TEQ/kg bw/week), even for mean consumption estimated with lower bound data. It is evident that the omission of PBDD/Fs from the TEQ scheme results in a significant underestimation of the cumulative toxicity and associated risk arising from this mode of action.

From inequitable to sustainable e-waste processing for reduction of impact on human health and the environment

Recycling of electric and electronic waste products (e-waste) which amounted to more than 50 million metric tonnes per year worldwide is a massive and global operation. Unfortunately, an estimated 70-80% of this waste has not been properly managed because the waste went from developed to low-income countries to be dumped into landfills or informally recycled. Such recycling has been carried out either directly on landfill sites or in small, often family-run recycling shops without much regulations or oversights. The process traditionally involved manual dismantling, cleaning with hazardous solvents, burning and melting on open fires, etc., which would generate a variety of toxic substances and exposure/hazards to applicators, family members, proximate residents and the environment. The situation clearly calls for global responsibility to reduce the impact on human health and the environment, especially in developing countries where poor residents have been shouldering the hazardous burden. On the other hand, formal e-waste recycling has been mainly conducted in small scales in industrialized countries. Whether the latter process would impose less risk to populations and environment has not been determined yet. Therefore, the main objectives of this review are: 1. to address current trends and emerging threats of not only informal but also formal e-waste management practices, and 2. to propose adequate measures and interventions. A major recommendation is to conduct independent surveillance of compliance with e-waste trading and processing according to the Basel Ban Amendment. The recycling industry needs to be carefully evaluated by joint effort from international agencies, producing industries and other stakeholders to develop better processes. Subsequent transition to more sustainable and equitable e-waste management solutions should result in more effective use of natural resources, and in prevention of adverse effects on health and the environment.

Polybrominated diphenyl ethers in serum from residents living in a brominated flame retardant production area: Occurrence, influencing factors, and relationships with thyroid and liver function

Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants (FRs) in China for decades, even after they were identified as persistent organic pollutants. In this study, serum samples were collected from 172 adults without occupational exposure who were residents of a well-known FR production region (Laizhou Bay, north China), and PBDE congeners were measured to assess their occurrence, congener profile and influencing factors in serum. Moreover, the relationships between serum concentrations of PBDEs and thyroid/liver function indicators were analyzed to evaluate whether human exposure to PBDEs would lead to thyroid/liver injury. All 8 PBDE congeners were detected at higher frequencies and serum concentrations than those found in general populations. The median levels of ∑PBDEs, BDE-209 and ∑_3-7PBDEs (sum of tri-to hepta-BDEs) were 64.5, 56.9 and 7.2 ng/g lw (lipid weight), respectively, which indicated that deca-BDE was the primarily produced PBDE in Laizhou Bay and that the lower brominated BDEs were still ubiquitous in the environment. Gender was a primary influencing factor for some BDE congeners in serum; their levels in female serum samples were significantly lower than those in male serum samples. Serum PBDE levels showed a downward trend with increased body mass index (BMI), which might reflect the increasing serum lipid contents. Serum levels of some BDE congeners were significantly positively correlated with certain thyroid hormones and antibodies, including free triiodothyronine (fT3), total triiodothyronine (tT3), total thyroxine (tT4) and thyroid peroxidase antibody (TPO-Ab). Levels of some congeners were significantly negatively correlated with some types of serum lipid, including cholesterol (CHOL), low density lipoprotein (LDL) and total triglyceride (TG). Other than serum lipids, only two liver function indicators, total protein (TP) and direct bilirubin (DBIL), were significantly correlated with certain BDE congeners (BDE-100 and BDE-154). Our results provide new evidence on the thyroid-disrupting and hepatotoxic effects of PBDEs.

Serum levels of novel brominated flame retardants (NBFRs) in residents of a major BFR-producing region: Occurrence, impact factors and the relationship to thyroid and liver function

Five currently used novel brominated flame retardants (NBFRs) were determined in 172 serum samples collected from nonoccupational residents of a major BFR-producing region. All the 5 NBFRs presented high detection frequencies (DFs, >90%), and decabromodiphenyl ethane (DBDPE), a substitute of decabrominated diphenyl ethers (deca-BDE), was the most abundant NBFR. The levels of DBDPE were from <LOD to 1590 ng/g lw, with a median level of 32.5 ng/g lw. The median levels of other NBFRs were from 0.134 to 2.87 ng/g lw, which were at least 10 times lower than that of DBDPE. Moreover, a comparison to other studies showed that our results were significantly higher than studies conducted in background population. The levels of some NBFRs adjusted by serum lipid showed negative and significant correlation with BMI, whereas the difference disappeared when NBFRs levels were calculated based on serum volume. Certain NBFRs in female showed significantly higher concentrations than those in male. No significant effect of age, smoking habit, education level and children birth (in female) on serum NBFR levels was observed. The relationship between the serum levels of NBFRs and a series of thyroid/liver injury biomarkers was further analyzed to evaluate the health effects of these NBFRs to human being. Results showed that a 10-fold increment in the serum DBDPE level was associated with decreased total triiodothyronine (TT3) level (-0.037 nmol/L) [95% CI: -0.070, -0.003]， whereas serum pentabromoethylbenzene (PBEB) level was associated with increased total triiodothyronine (TT3) level (0.031 nmol/L) [95% CI: 0.001, 0.060]. For liver indicators, a 10-fold increment in the serum level of PBT was associated with decreased Ln aspartate aminotransferase/alanine aminotransferase (AST/ALT) level (-0.068) [95% CI: -0.129, -0.007]. A 10-fold increment in the serum level of BTBPE was associated with increased TBIL level (0.869 μmol/L) [95% CI: 0.175, 1.564], direct bilirubin (DBIL) level (0.231 μmol/L) [95% CI: 0.075, 0.388] and IDBIL level (0.638 μmol/L) [95% CI: 0.091, 1.185]. Our findings indicate that BFR production is posing heavy BFR contamination to surrounding environment and human being, and which might relate to thyroid disruption and liver injury.

Dietary exposure assessment of a nursing mother-infant cohort to legacy and novel brominated flame retardants: Results of a 3-day duplicate diet study in Beijing, China

In a 3-day duplicate diet study of a nursing mother-infant cohort (n = 20), the levels of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and 5 novel brominated flame retardants (BFRs) were measured in 60 24-h duplicate diet samples and 20 breast milk samples provided by the mothers. The dietary BFR intake and related health risks of the mothers and their babies due to food consumption or human milk ingestion were subsequently assessed. At median concentrations of 284, 264 and 177 pg/g wet weight (ww) in the diet, decabrominated diphenyl ethers (BDE-209), decabromodiphenyl ethane (DBDPE) and HBCDD were predominant among the total BFRs. In human milk, HBCDD was the most abundant BFR, followed by BDE-209 and DBDPE, which indicates that BDE-209 and HBCDD have remained ubiquitous in the environment because of their continuous production and use in China. Meanwhile, concentrations of DBDPE were comparative to those of PBDEs and HBCDD in both diet and human milk, and DBDPE also had much higher concentrations than any other NBFRs, which indicates that the BFR consumption pattern in China is shifting from legacy BFRs to NBFRs. The median estimated dietary intakes (EDIs) of BDE-209, HBCDD and DBDPE for the mothers were 6.83, 3.73 and 5.44 ng/kg bw/day, respectively, and EDIs for their nursing babies were 24.7, 41.9 and 7.83 ng/kg bw/day, respectively. The nursing infants showed higher BFR body burden than the mothers. However, the EDIs obtained for both mothers and their babies discloses a low health risk to this mother-infant cohort.

Polybrominated diphenyl ethers and decabromodiphenyl ethane in paired hair/serum and nail/serum from corresponding chemical manufacturing workers and their correlations to thyroid hormones, liver and kidney injury markers

We detected the polybrominated diphenyl ethers (PBDEs) or decabromodiphenyl ethane (DBDPE) in paired hair-serum and nail-serum samples collected from the corresponding chemical manufacturing workers. The levels of decabrominated diphenyl ether (BDE-209) or DBDPE in the serum, hair and nail samples were all significantly higher than those reported in other studies, and the "work place" (pretreatment or posttreatment workshop) was the primary influencing factor that affected the levels of specific BFRs in vivo. For BDE-209 workers, the BDE-209 in both the hair and nail samples were significantly and positively related to the BDE-209 in the serum, indicating that both hair and nails can be used as noninvasive biomatrices to reflect internal exposure to BDE-209. In DBDPE workers, hair rather than nails was more suitable for use as a noninvasive biomatrix to infer the DBDPE exposure level. A series of serum biomarkers reflecting thyroid hormones and liver and kidney injuries were tested to calculate the correlations between hair or nail BFR levels and the levels of the biomatrices. The BDE-209 in the hair samples was significantly and positively correlated with the total protein (TP), and the nail BDE-209 level was significantly and positively related to the total bilirubin (TBIL), indirect bilirubin (IDBIL) and uric acid (UA). The DBDPE in hair was significantly and positively correlated with the thyroid hormones free triiodothyronine (fT3) and total triiodothyronine (tT3) and kidney injury markers, including blood urea nitrogen (BUN), creatinine (CRE) and cystatin C (Cys-C). In addition, the nail DBDPE levels were significantly and positively correlated with the albumin/globulin (A/G), BUN, CRE and Cys-C but negatively correlated with the TP and globulin (GLO). Our findings provide preliminary evidence that hair and nails can be used as noninvasive biomatrices for assessing internal BFR exposure and health damage in occupational workers.

Hepatotoxicity of decabromodiphenyl ethane (DBDPE) and decabromodiphenyl ether (BDE-209) in 28-day exposed Sprague-Dawley rats

Decabromodiphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are heavily used in various industrial products as flame retardant. They have been found to be persistent in the environment and have adverse health effects in humans. Although some former studies have reported toxic effects of BDE-209, the study of DBDPE's toxic effects is still in its infancy, and the effects of DBDPE on hepatotoxicity are also unclear. This study aimed to evaluate and compare the hepatotoxicity induced by BDE-209 and DBDPE using a rat model. Sprague-Dawley rats were administered DBDPE or BDE-209 (5, 50, 500 mg/kg bodyweight) intragastrically once a day for 28 days. Twenty-four hours after the end of treatment, the rats were sacrificed, and body liver weight, blood biochemical parameters, liver pathology, oxidative stress, inflammation, pregnane X receptor (PXR), constitutive androstane receptor (CAR), and changes in cytochrome P450 (CYP3A) enzymes were measured. Our results showed that both BDE-209 and DBDPE could cause liver morphological changes, induce oxidative stress, increase γ-glutamyl transferase and glucose levels in serum, and down-regulate PXR, CAR, and CYP3A expression. In addition, BDE-209 was found to increase liver weight and the ratio of liver/body weight, lead to elevated total bilirubin and indirect bilirubin levels in serum, and induce inflammation. The present study indicated that BDE-209 and DBDPE may interfere with normal metabolism in rats through oxidative stress and inflammation, which inhibit PXR and CAR to induce the expression of CYP3A enzymes, and finally produce hepatotoxic effects and cause liver damage in rats. Comparatively, our results show that the damage caused by BDE-209 was more serious than that caused by DBDPE.