Comparative toxicity and liver transcriptomics of legacy and emerging brominated flame retardants following 5-day exposure in the rat

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.

Insight into Tetrabromobisphenol A-Associated Liver Transcriptional Landscape via Single Cell RNA Sequencing

In recent years, there has been growing concern over the rising incidence of liver diseases, with increasing exposure to environmental toxins as a significant contributing factor. However, the mechanisms of liver injury induced by environmental pollutants are largely unclear. Here, using tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant, as an example, environmental toxin-induced liver toxicity in mice is characterized via single-cell sequencing technology. Heterogeneous gene expression profiles after exposure to TBBPA in major cell types of the liver are demonstrated. In hepatocytes, pathway analysis of differentially expressed genes reveals the enhanced interferon response and diminished metabolic processes. The disrupted endothelial functions in TBBPA-treated cells are then shown. Moreover, the activation of M2-polarization in Kupffer cells, as well as activated effector T and B cells are unveiled in TBBPA-treated cells. Finally, ligand-receptor pair analysis shows that TBBPA disrupts cell-cell communication and induces an inflammatory microenvironment. Overall, the results reveal that TBBPA-induced dysfunction of hepatocytes and endothelial cells may then activate and recruit other immune cells such as Kuffer cells, and T/NK cells into the liver, further increasing inflammatory response and liver injury. Thus, the results provide novel insight into undesiring environmental pollutant-induced liver injury.

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.

Association of flame retardants, polybrominated diethyl ethers (PBDEs), with vitamin D in female subjects

INTRODUCTION

A class of flame retardants, polybrominated diethyl ethers (PBDEs), are known endocrine disrupters and may induce the hepatic enzymes CYP24 and CYP3A that promote 25-hydroxylation of vitamin D3. Therefore, this study examined the association of PBDEs with vitamin D3 (25(OH)D3) and the active 1,25-dihydrovitamin D3 (1,25(OH)2D3) in a cohort of non-obese women.

METHODS

58 female participants (age:31.9 ± 4.6 years; body mass index (BMI):25.7 ± 3.7 kg/m2) had seven indicator PBDEs [PBDE28; PBDE47; PBDE99; PBDE100; PBDE153; PBDE154; PBDE183] measured using high resolution gas chromatography, with ƩPBDE level calculated. 25(OH)D3 and 1,25(OH)2D3 levels were determined by isotope-dilution liquid chromatography tandem mass spectrometry. Plasma level of calcium/calmodulin-dependent protein kinase type 1 (CaMK1) was measured by Somascan proteomics.

RESULTS

In this cohort, vitamin D3 (25(OH)D3) and 1,25(OH)2D3 levels were 22.9 ± 11.2 ng/mL and 0.05 ± 0.02 ng/mL, respectively. Of those, 28 had vitamin D deficiency [25(OH)D3 level <20 ng/mL (<50 nmol/L)]. For the whole group, individual PBDEs (PBDE28; PBDE47; PBDE99; PBDE100; PBDE153; PBDE154; PBDE183) and ƩPBDEs did not correlate with 25(OH)D3 or its active metabolite 1,25(OH)2D3 nor with BMI. For the subset who were 25(OH)D3 sufficient, negative correlations were found for 1,25(OH)2D3 with PBDE153 (ρ = -0.77; p = 0.02) and PBDE100 (ρ = -0.72; p = 0.005). In the subset of women who were 25(OH)D3 deficient, positive correlations were found for 1,25(OH)2D3 with PBDE153 (ρ = 0.68; p = 0.02) and ƩPBDEs (ρ = 0.57; p = 0.03). Using sufficient and deficient subset categories, no correlations were seen with 25(OH)D3 nor any of the PBDEs, and PBDEs did not correlate to renal function (estimated glomerular filtration rate, eGFR). 1,25(OH)2D3 was negatively associated with CaMK1 (r = -0.36; p = 0.03) as was PBDE153 (r = -0.31; p = 0.02).

CONCLUSION

PBDEs were not associated with 25(OH)D3, but PBDE100 and 153 correlated with its active 1,25(OH)2D3 metabolite and PBDE153 correlated to the calcium modulator CaMKI, suggesting that PBDE effects could either be mediated through vitamin D status or that functional inactivation or inhibition of 1,25(OH)2D3 may contribute to the impact of vitamin D deficiency.

Metagenomic insights into the mechanisms of triphenyl phosphate degradation by bioaugmentation with Sphingopyxis sp. GY

Biodegradation of triphenyl phosphate (TPHP) by Sphingopyxis sp. GY was investigated, and results demonstrated that TPHP could be completely degraded in 36 h with intracellular enzymes playing a leading role. This study, for the first time, systematically explores the effects of the typical brominated flame retardants, organophosphorus flame retardants, and heavy metals on TPHP degradation. Our findings reveal that TCPs, BDE-47, HBCD, Cd and Cu exhibit inhibitory effects on TPHP degradation. The hydrolysis-, hydroxylated-, monoglucosylated-, methylated products and glutathione (GSH) conjugated derivative were identified and new degradation pathway of TPHP mediated by microorganism was proposed. Moreover, toxicity evaluation experiments indicate a significant reduction in toxicity following treatment with Sphingopyxis sp. GY. To evaluate its potential for environmental remediation, we conducted bioaugmentation experiments using Sphingopyxis sp. GY in a TPHP contaminated water-sediment system, which resulted in excellent remediation efficacy. Twelve intermediate products were detected in the water-sediment system, including the observation of the glutathione (GSH) conjugated derivative, monoglucosylated product, (OH)2-DPHP and CH3-O-DPHP for the first time in microorganism-mediated TPHP transformation. We further identify the active microbial members involved in TPHP degradation within the water-sediment system using metagenomic analysis. Notably, most of these members were found to possess genes related to TPHP degradation. These findings highlight the significant reduction of TPHP achieved through beneficial interactions and cooperation established between the introduced Sphingopyxis sp. GY and the indigenous microbial populations stimulated by the introduced bacteria. Thus, our study provides valuable insights into the mechanisms, co-existed pollutants, transformation pathways, and remediation potential associated with TPHP biodegradation, paving the way for future research and applications in environmental remediation strategies.

DBDPE upregulates NOD-like receptor signaling to induce NLRP3 inflammasome-mediated HAECs pyroptosis

Decabromodiphenyl ethane (DBDPE), a typical new brominated flame retardant (BFR), is a widespread new pollutant in the environment. Several studies and our previous studies have found that DBDPE can cause aortic endothelial injury and aortic endothelial cell pyroptosis, whereas the molecular mechanism involved has not been elucidated. In this study, we exposed human aortic endothelial cells (HAECs) to 25 μmol/L of DBDPE and analyzed the gene expression profiles by Affymetrix PrimeView™ Human Gene Expression Chip. The results showed that 886 genes were differentially expressed in the DBDPE exposure group. Enrichment analyses revealed that differentially expressed genes were mainly enriched in the inflammatory response and NOD-like receptor signal pathway. Gene-gene functional interaction analyses and crossover genes and pathways analyses found that the NOD-like receptor signal pathway may be involved in regulating NLRP3 and IL-18. We found that NOD2 cannot interact with NLRP3 directly through an immunoprecipitation experiment. Thus, we construct the RIPK2 knockdown HAECs cell line to repress the NOD-like receptor signaling and further study the mechanism of DBDPE-activated NLRP3 inflammasome to induce HAECs pyroptosis. The results showed that RIPK2 knockdown could repress DBDPE-induced NOD-like receptor signaling pathway upregulation, inhibit NLRP3 inflammasome activation, and decrease HAECs pyroptosis. In addition, RIPK2 knockdown decreased the ROS generation in HAECs induced by DBDPE. And NAC pretreated HAECs inhibited DBDPE-induced NLRP3 inflammasome activation and HAECs pyroptosis. These results demonstrated that DBDPE upregulated NOD-like receptor signaling to induce ROS generation and, in turn, activated NLRP3 inflammasome, leading to HAECs pyroptosis.

The effects of hexabromocyclododecane on the transcriptome and hepatic enzyme activity in three human HepaRG-based models

The disruption of thyroid hormone homeostasis by hexabromocyclododecane (HBCD) in rodents is hypothesized to be due to HBCD increasing the hepatic clearance of thyroxine (T4). The extent to which these effects are relevant to humans is unclear. To evaluate HBCD effects on humans, the activation of key hepatic nuclear receptors and the consequent disruption of thyroid hormone homeostasis were studied in different human hepatic cell models. The hepatoma cell line, HepaRG, cultured as two-dimensional (2D), sandwich (SW) and spheroid (3D) cultures, and primary human hepatocytes (PHH) cultured as sandwich were exposed to 1 and 10 µM HBCD and characterized for their transcriptome changes. Pathway enrichment analysis showed that 3D models, followed by SW, had a stronger transcriptome response to HBCD, which is explained by the higher expression of hepatic nuclear receptors but also greater accumulation of HBCD measured inside cells in these models. The Pregnane X receptor pathway is one of the pathways most upregulated across the three hepatic models, followed by the constitutive androstane receptor and general hepatic nuclear receptors pathways. Lipid metabolism pathways had a downregulation tendency in all exposures and in both PHH and the three cultivation modes of HepaRG. The activity of enzymes related to PXR/CAR induction and T4 metabolism were evaluated in the three different types of HepaRG cultures exposed to HBCD for 48 h. Reference inducers, rifampicin and PCB-153 did affect 2D and SW HepaRG cultures' enzymatic activity but not 3D. HBCD did not induce the activity of any of the studied enzymes in any of the cell models and culture methods. This study illustrates that for nuclear receptor-mediated T4 disruption, transcriptome changes might not be indicative of an actual adverse effect. Clarification of the reasons for the lack of translation is essential to evaluate new chemicals' potential to be thyroid hormone disruptors by altering thyroid hormone metabolism.

Gene expression profiling after exposure to a chemical carcinogen, Pentabrominated Diphenyl Ether, at different life stages

Exposure to environmental hazards occurs at different stages of our lifetime-infant, child, adult. This study integrates recently published toxicogenomics data to examine how exposure to a known rat chemical carcinogen (pentabrominated diphenyl ether (PBDE)) upregulated liver transcriptomic changes at different life cycle stages (PND 4, PND 22, adult). We found that at all three life cycle stages PBDE exposure induced hepatocellular transcriptomic changes in disease pathways including cancer, metabolic, membrane function, and Nrf2 antioxidant pathways, pathways all characteristics of chemical carcinogens. In addition, in the adult rat after a 5-day exposure to the chemical carcinogen, there was upregulation of members of the Ras oncogenic pathway, a specific pathway found to be activated in the PBDE-induced tumors in rats in a previous hazard identification cancer study. The findings of liver transcript changes characteristic of carcinogenic activity after early life exposures and after short-term adult exposures provides data to support the use of transcriptomic data to predict the apical cancer endpoints in model studies. Using data from gene expression profiling studies after neonatal, young, or adult short-term chemical exposure helps to meet the 21st century toxicology goal of developing study designs to reduce, refine, and replace the use of traditional 2-year rodent cancer studies to provide hazard identification information. The studies reported here find that key transcripts associated with carcinogenesis were elevated in neonate (PND 4), young (PND 22) and adult animals after short-term exposure to PBDE, a known experimental chemical carcinogen in model systems.

Developmental toxicity assessments for TBBPA and its commonly used analogs with a human embryonic stem cell liver differentiation model

Tetrabromobisphenol A (TBBPA) is widely used in industrial production as a halogenated flame retardant (HFR). Its substitutes and derivatives are also commonly employed as HFRs. Consequently, they can be frequently detected in environmental and human samples. The potential developmental toxicity of TBBPA and its analogs, particularly to the human liver, is still controversial or not thoroughly assessed. Therefore, in this study, we focused on the early stages of human liver development to explore the toxic effects of those HFRs, by using a human embryonic stem cell liver differentiation model. We concluded that nanomolar treatments (1, 10, and 100 nM) of those pollutants may not exert significant interference to liver development and functions. However, at 5 μM doses, TBBPA and its analogs severely affected liver functions, such as glycogen storage, and caused lipid accumulation. Furthermore, TBBPA-bis(allyl ether) showed the most drastic effects among the six compounds tested. Taken together, our findings support the view that TBBPA can be used safely, provided its amounts are strictly controlled. Nonetheless, TBBPA alternatives or derivatives may exhibit stronger adverse effects than TBBPA itself, and may not be safer choices for manufacturing applications when utilized in a large and unrestricted way.

Synthesis of a Zinc Hydroxystannate/Sepiolite Hybrid Additive to Avoid Fire Propagation and Reduce Smoke Emission of EPDM Rubber Nanocomposites

A zinc hydroxystannate/sepiolite (SEPZHS) hybrid additive was successfully prepared following a facile wet chemical route synthesis where zinc hydroxystannate (ZHS) nanoparticles were grown on the sepiolite's surface. SEPZHS particles have a fibrillar structure with ZHS nanoparticles homogeneously dispersed and with significantly smaller particle sizes than the synthesized ZHS nanoparticles alone. Sepiolite and SEPZHS were organically modified and introduced in a basic ethylene propylene diene monomer rubber (EPDM) formulation for cable to evaluate the nanocomposite behavior under direct fire sources. The results confirmed the synergistic effect of the hybrid SEPZHS additive in the formation of a most stable and efficient char barrier, thus improving the flame-retardant behavior of EPDM nanocomposite in terms of heat emission, with reductions of more than 40% in the peak of Heat Release Rate (cone calorimeter test), and smoke suppression, with more than 25% reduction in the Total Smoke Production and Smoke Density parameters (smoke chamber test). Moreover, the addition of sepiolite-based additives increased the mechanical properties (hardness) of the nanocomposites, as a result of the matrix reinforcement. This suggests that the SEPZHS hybrid additive may provide a promising option for a new, cost-effective, eco-friendly, yet efficient flame-retardant solution.

Comprehensive analysis of emerging flame retardants, a risk factor to prostate cancer?

Among man-made chemicals, flame retardants have caused great environmental concerns. Several studies in recent years have investigated potential sources of flame retardants, environmental distribution, exposure to wild animals and humans and toxicity. However, studies focusing on the prediction of toxicity of flame retardants are limited. Herein, toxicological and tumor databases were applied to evaluate the potential correlation between emerging flame retardants (EFRs) and tumors. Further analysis also showed that EFRs may be associated with prostate cancer (PCa). After constructing an EFR-related prognostic prediction model, it was established that EFR-related genes showed a strong prognostic predictive value among PCa patients. In addition, compared with the clinical characteristics model (including age, Gleason score, prostate-specific antigen level, T stage and N stage), a prognostic predictive model-based risk score demonstrated a better predictive value of PCa. The AUC of the 31-gene prognostic signature at 1, 3 and 5 years was 0.843, 0.824 and 0.819, respectively. In addition, the AUC of the risk score, Gleason score, age, PSA level, T stage and N stage were 0.843, 0.637, 0.414, 0.490, 0.668 and 0.517, respectively. Our analysis provides a comprehensive map of EFR interaction genes and demonstrated a new direction for environmentally hazardous materials and diseases.

Decabromodiphenyl ether induces ROS-mediated intestinal toxicity through the Keap1-Nrf2 pathway

Polybrominated diphenyl ethers (PBDEs) are widely used brominated flame retardants as commercial products. PBDEs have been demonstrated to induce hepatic, reproductive, neural, and thyroid toxicity effects. This study aimed to clarify the potential intestinal toxicity effects of decabrominated diphenyl ether (PBDE-209) in vivo and in vitro. First, we investigated the change of PBDE-209 on oxidative stress in the intestine of mice. Subsequently, the potential toxicity mechanism of PBDE-209 in vitro was investigated. Caco-2 cells were treated with different concentrations of PBDE-209 (1, 5, and 25 μmol/L) for 24  and 48 h. We determined the cell viability, reactive oxygen species (ROS) level, multiple cellular parameters, and relative mRNA expressions. The results showed that PBDE-209 significantly injured the colon of mice, increased the intestinal levels of malondialdehyde (MDA), and changed the antioxidant enzyme activities. PBDE-209 inhibited the proliferation and induced cytotoxicity of Caco-2 cells. The change in ROS production and mitochondrial membrane potential (MMP) revealed that PBDE-209 caused oxidative stress in Caco-2 cells. The real-time PCR assays revealed that PBDE-209 inhibited the mRNA expression level of antioxidative defense factor, nuclear factor erythroid 2-related factor 2 (Nrf2). Furthermore, the FAS and Cytochrome P450 1A1 (CYP1A1) mRNA expression levels were increased in Caco-2 cells. These results suggested that PBDE-209 exerts intestinal toxicity effects in vivo and in vitro and inhibits the antioxidative defense gene expression in Caco-2 cells. This study provides an opportunity to advance the understanding of toxicity by the persistent environmental pollutant PBDE-209 to the intestine.

HBCD, TBECH, and BTBPE exhibit cytotoxic effects in human vascular endothelial cells by regulating mitochondria function and ROS production

Brominated flame retardants (BFRs), such as, 1,2,5,6-tetrabromocyclooctane (HBCD), 1,2-dibromo-4-(1,2-dibromopropyl)cyclohexane (TBECH), and 1 1,2-bis-(2,4,6-tribromophenoxy)ethane (BTBPE), have garnered increasing attention due to their potent biological effects. In the present study, the toxicity of HBCD, TBECH, and BTBPE in human vascular endothelial cells (ECs) was explored. The data showed that HBCD, TBECH, and BTBPE induced cytotoxicity, namely dose-dependent cell viability reduction, cell membrane permeability and apoptosis increase, migration, and lumen formation inhibition. Moreover, HBCD was found to be more toxic than BTBPE or TBECH. Exposure to HBCD, TBECH, and BTBPE led to the production of reactive oxygen species, mitochondrial superoxide generation, and mitochondrial membrane potential collapse, implying that reactive stress caused the cytotoxicity. The ATP content, glutathione content, superoxide dismutase, and MDA activities were reduced, indicating that mitochondrial dysfunction may be the key mechanisms responsible for apoptosis. The present study suggested that mitochondria are a new target of BFRs in ECs and further deepened our understanding of the developmental toxicity of BFRs.

Update of the risk assessment of hexabromocyclododecanes (HBCDDs) in food

The European Commission asked EFSA to update its 2011 risk assessment on hexabromocyclododecanes (HBCDDs) in food. HBCDDs, predominantly mixtures of the stereoisomers α-, β- and γ-HBCDD, were widely used additive flame retardants. Concern has been raised because of the occurrence of HBCDDs in the environment, food and in humans. Main targets for toxicity are neurodevelopment, the liver, thyroid hormone homeostasis and the reproductive and immune systems. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour in mice can be considered the critical effects. Based on effects on spontaneous behaviour in mice, the Panel identified a lowest observed adverse effect level (LOAEL) of 0.9 mg/kg body weight (bw) as the Reference Point, corresponding to a body burden of 0.75 mg/kg bw. The chronic intake that would lead to the same body burden in humans was calculated to be 2.35 μg/kg bw per day. The derivation of a health-based guidance value (HBGV) was not considered appropriate. Instead, the margin of exposure (MOE) approach was applied to assess possible health concerns. Over 6,000 analytical results for HBCDDs 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 LB exposure to HBCDDs were fish meat, eggs, livestock meat and poultry. The CONTAM Panel concluded that the resulting MOE values support the conclusion that current dietary exposure to HBCDDs across European countries does not raise a health concern. An exception is breastfed infants with high milk consumption, for which the lowest MOE values may raise a health concern.

Transcriptomic data from the rat liver after five days of exposure to legacy or emerging brominated flame retardants

Large-scale gene expression analysis of legacy* and emerging** brominated flame retardants were conducted in the male Harlan Sprague Dawley rat [1]. Each animal was dosed for 5 days with the chemical at concentrations of 0.1 – 1000 μmol/kg body weight per day. Following the last dose, a specimen of the left liver was removed for RNA extraction. The amplified RNA (aRNA) was fragmented and then hybridized to Affymetrix Rat Genome 230 2.0 Arrays. Each GeneChip® array was scanned using an Affymetrix GeneChip® Scanner 3000 7 G to generate raw expression level data (.CEL files). Statistical contrasts were used to find pairwise gene expression differences between the control group and each dose group using the R/maanova package [2]. The transcriptomic data can be used to provide insights into the degree of toxicity, toxic mechanisms, disease pathways activated by exposure, and for benchmark dose analysis. The gene expression data for each of the nine flame retardants discussed here accompanies the research article entitled, “Comparative Toxicity and Liver Transcriptomics of Legacy and Emerging Brominated Flame Retardants following 5-Day Exposure in the Rat” [1].

* polybrominated diphenyl ether 47 (PBDE 47), decabromodiphenyl ether (decaBDE), hexabromocyclododecane (HBCD); ** 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB); bis(2-ethylhexyl) tetrabromophthalate (TBPH); tetrabromobisphenol A-bis(2,3-dibromopropyl ether (TBBPA-DBPE); 1,2-bis(tribromophenoxy)ethane (BTBPE); decabromodiphenylethane (DBDPE); hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO).