Neurodevelopmental effects of decabromodiphenyl ether (BDE-209) and implications for the Reference Dose

Improved microalgae carbon fixation and microplastic sedimentation in the lake through in silico method

The impact of microplastics in lake water environments on microalgae carbon fixation and microplastic sedimentation has attracted global attention. The molecular dynamic simulation method was used to design microplastic additive proportioning schemes for improving microalgae carbon fixation and microplastic sedimentation. Results showed that the harm of microplastics can be effectively alleviated by adjusting the proportioning scheme of plastic additives. Besides, the decabromodiphenyl oxide (DBDPO) was identified as the main additive that affect the microalgae carbon fixation and microplastic sedimentation. Thus, a molecular modification based on CiteSpace visual analysis was firstly used and 12 DBDPO derivatives were designed. After the screening, DBDPO-2 and DBDPO-5 became the environmentally friendly DBDPO alternatives, with the highest microalgae carbon fixation and microplastic sedimentation ability enhancement of over 25 %. Compared to DBDPO, DBDPO derivatives were found easier to stimulate the adsorption and binding ability of surrounding hotspot amino acids to CO2 and ribulose-5-phosphate, increasing the solvent-accessible surface area of microplastics, thus improving the microalgae carbon fixation and microplastic sedimentation ability. This study provides theoretical support for simultaneously promoting the microalgae carbon fixation and microplastic sedimentation in the lake water environment and provides scientific basis for the protection and sustainable development of lake water ecosystem.

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.

Nano‑selenium alleviates the pyroptosis of cardiovascular endothelial cells in chicken induced by decabromodiphenyl ether through ERS-TXNIP-NLRP3 pathway

Decabromodiphenyl ether (BDE-209) is one of the most widely used flame retardants that can infect domestic and wildlife through contaminated feed. Nano‑selenium (Nano-Se) has the advantage of enhancing the anti-oxidation of cells. Nonetheless, it remains uncertain whether Nano-Se can alleviate vascular Endothelial cells damage caused by BDE-209 exposure in chickens. Therefore, we established a model with 60 1-day-old chickens, and administered BDE-209 intragastric at a ratio of 400 mg/kg bw/d, and mixed Nano-Se intervention at a ratio of 1 mg/kg in the feed. The results showed that BDE-209 could induce histopathological and ultrastructural changes. Additionally, exposure to BDE-209 led to cardiovascular endoplasmic reticulum stress (ERS), oxidative stress and thioredoxin-interacting protein (TXNIP)-pyrin domain-containing protein 3 (NLRP3) pathway activation, ultimately resulting in pyroptosis. Using the ERS inhibitor 4-PBA in Chicken arterial endothelial cells (PAECs) can significantly reverse these changes. The addition of Nano-Se can enhance the body's antioxidant capacity, inhibit the activation of NLRP3 inflammasome, and reduce cellular pyroptosis. These results suggest that Nano-Se can alleviate the pyroptosis of cardiovascular endothelial cells induced by BDE-209 through ERS-TXNIP-NLRP3 pathway. This study provides new insights into the toxicity of BDE-209 in the cardiovascular system and the therapeutic effects of Nano-Se.

Comparative Effects of Brominated Flame Retardants BDE-209, TBBPA, and HBCD on Neurotoxicity in Mice

Brominated flame retardants (BFRs) are ubiquitous industrial chemicals. In China, BFRs that are applied in large quantities include decabromodiphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCD). Although findings are not always unequivocal, mounting evidence in vivo suggests that the BFRs have potential neurotoxicity. The present study aimed to assess and compare the neurotoxic effects of these three BFRs' exposure. Male mice were orally exposed to BDE-209, TBBPA, or HBCD at 50 and 100 mg/kg bw/day for 28 days. The cognitive behavior, oxidative stress (ROS, MDA, and GSH), apoptosis-related genes (caspase-3, bax, and bcl-2), memory-related proteins (BDNF and PSD-95), and neurotransmitters (AChE and ChAT) were detected comparatively. Results showed that high doses of BDE-209, TBBPA, and HBCD exposure impaired spatial memory of mice, elevated ROS and MDA and reduced GSH levels of hippocampus, upregulated caspase-3 and bax expressions, decreased BDNF and PSD-95 levels, and disordered AChE and ChAT levels. Notably, BDE-209 caused greater adverse effects > HBCD > TBBPA. This study confirms and extends that these three BFRs had similar neurotoxic effects at current concentrations, although they may be more or less toxic.

Comprehensive evaluation of the toxicity of the flame retardant (decabromodiphenyl ether) in a bioindicator fish (Gambusia affinis)

In recent years, concerns have increased about the adverse effects on health and the environment of polybrominated diphenyl ethers (PBDEs), especially BDE-209, the most widely PBDE used globally. These pollutants derive from e-waste and present different adverse effects on biota. In this work, a toxicological study on mosquitofish (Gambusia affinis) using BDE-209 (2,2',3,3',4,4',5,'5',6,6'-decabromodiphenyl ether) was carried out. Acute toxicity bioassays were conducted with daily renewal of solutions, using different concentrations of environmental relevance, ranged between 10 and 100 μg L^-1 of BDE-209. At 48 and 96 h of exposure, several parameters were evaluated, such as mortality, individual activity (swimming), biochemical activity (catalase; thiobarbituric acid-reactive substances; and acetylcholinesterase), and cytotoxic responses (micronucleus frequencies). In addition, integrated biomarker response and multivariate analyses were conducted to study the correlation of biomarkers. The calculated Lethal Concentration-50 remained constant after all exposure times (24 to 96 h), being the corresponding value 27.79 μg L^-1 BDE-209. Furthermore, BDE-209 induced effects on the swimming activity of this species in relation to acetylcholine, since BDE-209 increased, producing oxidative damage at the biochemical level and genotoxicity after 48 h of exposure to 10 and 25 μg L^-1 BDE-209. The results indicate that BDE-209 has biochemical, cytotoxic, neurotoxic, and genotoxic potential on G. affinis. In addition, mosquitofish could be used as a good laboratory model to evaluate environmental stressors since they could represent a risk factor for Neotropical species.

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.

Transportation and degradation of decabrominated diphenyl ether in sequential anoxic and oxic crop rotation

This work evaluated the debromination and uptake of ¹⁴C-labeled BDE-209 in rice cultivars grown in anoxic soil for 120 days (d) followed by cultivation of vegetables (peanut, eggplant and pepper) in oxic soil (120 d). Degradation of BDE-209 to lower polybrominated diphenyl ethers (PBDEs) occurred in cultivated soils, and more metabolites were released in oxic soil than in anoxic soil. The crop rotation from anoxic to oxic greatly enhanced the dissipation of BDE-209 in the soil (P < 0.05), in which the dissipation in anoxic soil planted with Huanghuazhan (HHZ, indica) and Yudao 1 (YD1, indica) were 6.8% and 2.4%, respectively, while in oxic soil with peanut and pepper were increased to 25.8% and 21.7%, respectively. The crop rotation also enhanced the degradation of BDE-209 in the soil, the recovered BDE-209 in soil after 120 d anoxic incubation with YD1 was 81.1%, but it decreased to 47.8% and 45.8% after another 120 d oxic incubation. Bioconcentration factors were between 0.23 and 0.36 for rice, eggplant and pepper but reached to 0.5 in peanut, which contains more lipids in the edible portion than the other test crops. The estimated daily intake for vegetables was 0.01-0.07 μg BDE-209-equivalent kg^-1 bw day^-1, which is at least two orders of magnitude below the maximum acceptable oral dose (7 μg kg^-1 bw day^-1). Our work confirms that crop rotation from rice to vegetable enhanced the dissipation and debromination of BDE-209 in the soil, and indicate that sequential anoxic-oxic rotation practice is considered to be effective in remediation of environmental pollutants.

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.

Exposure to polybrominated diphenyl ethers (PBDEs) and child behavior: Current findings and future directions

Polybrominated diphenyl ethers (PBDEs) are recognized neurotoxicants, but the extent to which PBDEs influence various domains of behavior in children is not fully understood. As such, we reviewed epidemiologic studies published to date to provide an overview of the current state of knowledge on PBDEs' potential role in behavioral development. We identified 19 epidemiologic studies reporting on associations of prenatal and childhood concentrations of PBDEs with behaviors assessed in children from 1 to 12years, including executive function, attention, externalizing and internalizing behaviors, adaptive skills, and social behaviors/Autism Spectrum Disorder (ASD). While the mechanisms of PBDE neurotoxicity in humans are still not clearly elucidated, findings from this review indicate that PBDE exposure during fetal development is associated with impairments in executive function and poorer attentional control in children. Results from large prospective cohorts demonstrate that prenatal and postnatal PBDE exposure adversely impacts externalizing behavior (e.g., hyperactivity and conduct problems). Additional studies are needed to determine whether PBDEs are associated with internalizing problems, adaptive skills, and social behaviors/ASD in children. Future studies will help better understand the potential neurotoxic effects of PBDE exposures during adolescence, possible sex-dependent effects, and the impact of exposure to BDE-209 and alternative flame retardants. Future studies should also examine chemical mixtures to capture real-world exposures when examining PBDEs and their impact on various behavioral domains in the context of multiple chemical exposures.

Exposure to decabromodiphenyl ether (BDE-209) produces mitochondrial dysfunction in rat liver and cell death

Polybrominated diphenyl ethers (PBDE) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunctions, reproductive disorders, and hepatotoxicity. The widespread use of PBDE as flame retardants has culminated in daily exposure of humans and wildlife to these contaminants and resulted in their banned use. Thus assessment of the potential effects of each PBDE congener on living organisms has become cause for concern. The aim of this study was to (1) examine the effects of decabromodiphenyl ether (BDE)-209 on different functions of HepG2 cells and (2) investigate whether this congener is involved in mitochondrial toxicity. The use of multiple methods was employed to (i) study the influence of BDE-209 on mitochondrial permeability transition (MPT) process in mitochondria isolated from rat liver and (ii) determine the consequential cellular damage. Our results showed that BDE-209 induced matrix swelling related to MPT with 10 µM and ATP depletion with 0.1 µM. In addition, 0.5 μM BDE-209 reduced HepG2 cell viability, produced collapse of membrane potential, but increased levels of reactive oxygen species (ROS) after 48 h incubation. After 24 h with 5 μM treatment elevated levels of ROS, DNA fragmentation and cytochrome c release, accompanied by caspase 9 and caspase 3 activation was noted. Taken together, these results suggest that short-duration exposure (24 or 48 h) to 0.5 μM or 5 μM BDE-209 concentrations diminished HepG2 cell viability due to apoptosis associated with mitochondrial dysfunction.

Metabolite profiling study on the toxicological effects of polybrominated diphenyl ether in a rat model

Polybrominated diphenyl ethers (PBDEs) are commonly used to retard the combustion of materials such as foam padding, textiles, or plastics, and numerous studies have confirmed the accumulation thereof in the environment and in fish, mammals, and humans. In this study, we used metabolomics to conduct an environmental risk assessment of the PBDE-209. We profiled the urinary metabolites of control and PBDE-treated rats (exposed to PBDE-209) using nuclear magnetic resonance (NMR) and mass spectrometry (MS). Global metabolic profiling indicated that the effects of PBDE-209 on the urinary metabolic profile were not significant. However, targeted metabolic profiling revealed progressive effects of PBDE-209 over a 7-day PBDE-209 treatment. Moreover, despite the weak PBDE-209 effects, we observed that choline, acetylcholine, 3-indoxylsulfate, creatinine, urea, and dimethyl sulfone levels were decreased, whereas that of pyruvate was significantly increased. Furthermore, we suggest that the increased pyruvate level and decreased levels of choline, acetylcholine, and uremic toxins were suggestive of endocrine disruption and neurodevelopmental toxicity caused by PBDEs. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1262-1272, 2017.

Simulating long-term occupational exposure to decabrominated diphenyl ether using C57BL/6 mice: biodistribution and pathology

Decabrominated biphenyl ether (BDE-209) is a fully brominated diphenyl ether compound used widely as an additive brominated flame retardant in a variety of consumer products. In recent years, BDE-209 has been reported to be abundant and persistent in the environment, and comparatively high burdens have been found in occupational environmental compartments and exposed individuals. In the present study, an animal model for simulating long-term occupational exposure to BDE-209 was set up. Female C57BL/6 mice (n=10) were intragastrically administered BDE-209 at a dose of 800 mg kg(-1) bw at 2-d intervals for 2 years with an internal blood level of approximately 200 ng mL(-1), which was comparable to the high level of BDE-209 detected in the occupational population, and the biodistribution and biological effects were evaluated systematically. The results showed that large amounts of the chemical accumulated in most tissues, and the preferential organs were the ovary and uterus, liver and lung. Decreased survival was observed in the exposed mice. The subsequent pathological analysis revealed hepatomegaly in the exposed mice, accompanied by obvious histopathological changes in the liver, lung, brain, spleen, kidney and ovary. No neoplastic lesions were observed in this lifetime exposure study. Although the number of experimental mice was limited, our observations offer a comprehensive understanding of the chronic toxicology of BDE-209 after continuous high-dose exposure.

Epigenetic effects of low perinatal doses of flame retardant BDE-47 on mitochondrial and nuclear genes in rat offspring

Polybrominated diphenyl ethers (PBDEs) are known endocrine disrupting chemicals used commonly as flame retardants in everything from electronics to furniture. Exposure to PBDEs during early development has been linked to neurodevelopmental delays. Despite mounting evidence of neurological harm from PBDE exposure, the molecular mechanisms underlying these effects on brain function remain unknown. We examined the effects of perinatal exposure to BDE-47, the most biologically active and prevalent BDE congener in North America, on epigenetic patterns in the frontal lobe of Wistar rats. Dams were gavaged with BDE-47 (0.002 and 0.2mg/kg body weight) at gestation days 9 and 16, and postnatal days 1, 8, and 15. Frontal lobes from offspring at postnatal day 41 were collected to measure 5-methylcytosine (5mC) in mitochondrial cytochrome c oxidase genes (Mt-co1, Mt-co2, and Mt-co3), global nuclear 5-hydroxymethylcytosine (5hmC) content, 5mC in repetitive elements L1Rn, and 5mC in nuclear genes (Bdnf, Crhr1, Mc2r, Nr3c1, and Snca) related to behavioral and brain functions in the nuclear genome. We observed a significant decrease in %5mC in Mt-co2 (difference from control=-0.68%, p=0.01 at the 0.2mg/kg BDE-47). 5mC in repetitive elements L1Rn decreased at 0.002 mg/kg BDE-47 (difference=-1.23%, p=0.02). Decreased nuclear 5mC was observed in Bdnf and Nr3c1 in BDE-47 exposed rats. However, we did not observe significant effects of PBDE toxicity on DNA methylation patterns for the majority of genes in the brain.

Alterations of endogenous metabolites in urine of rats exposed to decabromodiphenyl ether using metabonomic approaches

There is large usage of polybrominated diphenyl ethers (PBDEs) especially for decabromodiphenyl ether (BDE-209, Deca-BDE) in controlling the risks of fire. The toxicological effects of PBDEs are worth being concerned about. Female SD rats were daily gavaged with BDE-209 ether at the dose of 100 mg/kg for 20 days. Histological observation was performed for the screening of the target organs for BDE-209 exposure. The distribution and metabolism of PBDEs in the exposed main organs were evidenced by HRGC-HRMS. Alterations of the endogenous metabolite concentrations in urine were investigated using metabonomic approaches based on (1)H NMR spectrum. Histopathological changes including serious edema in kidney, hepatocellular spotty necrosis and perivasculitis in liver indicated that BDE-209 caused potential influences on endogenous metabolism in the exposed liver and the kidney. BDE-209 was found to be highly accumulated in lipid, ovary, kidney and liver after 20 days' exposure. Occurrence of other lower brominated PBDEs in the rats demonstrated that reductive debromination process happened in vivo. Hydroxylated and methoxylated-BDEs, as metabolism products, were also detected in the rat tissues. A total of 12 different endogenous metabolites showed obvious alterations in urine from the exposed rats, indicating the disturbance of the corresponding internal biochemical processes induced by BDE-209 exposure. These findings in vivo suggested the potential health risk might be of concern due to the toxicological effects of BDE-209 as a ubiquitous compound in the environment.

Effects of BDE-209 contaminated sediments on zebrafish development and potential implications to human health

Polybrominated diphenyl ethers are compounds widely used as flame-retardants, which are of increasing environmental concern due to their persistence, and potential adverse effects. This study had two objectives. First, we assessed if BDE-209 in sediment was bioavailable and bioaccumulated into zebrafish embryos. Secondly, we assessed the potential impact on human and environmental health of bioavailable BDE-209 using human in vitro cell assays and zebrafish embryos. Zebrafish were exposed from 4h to 8days post-fertilization to sediments spiked with 12.5mg/kg of BDE-209. Zebrafish larvae accumulated ten fold more BDE-209 than controls in unspiked sediment after 8days. BDE-209 impacted expression of neurological pathways and altered behavior of larvae, although BDE-209 had no visible affect on thyroid function or motoneuron and neuromast development. Zebrafish data and in silico predictions suggested that BDE-209 would also interact with key human transcription factors and receptors. We therefore tested these predictions using mammalian in vitro assays. BDE-209 activated human aryl hydrocarbon receptor, peroxisome proliferator activating receptors, CF/b-cat, activator protein 1, Oct-MLP, and the estrogen receptor-related alpha (ERRα) receptor in cell-based assays. BDE-209 also inhibited human acetylcholinesterase activity. The observation that BDE-209 can be bioaccumulated from contaminated sediment highlights the need to consider this as a potential environmental exposure route. Once accumulated, our data also show that BDE-209 has the potential to cause impacts on both human and environmental health.

Dietary exposure of American kestrels (Falco sparverius) to decabromodiphenyl ether (BDE-209) flame retardant: uptake, distribution, debromination and cytochrome P450 enzyme induction

Accumulation and evidence of debromination of the flame retardant 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) have been reported for biota, including raptorial birds, based on PBDE congener residues in tissues and eggs. However, in vivo studies with BDE-209-exposed birds are rare and unknown for a raptorial species. In the present study, males (n=22) of raptorial American kestrels (Falco sparverius) were exposed to 116,000ng of BDE-209 (high purity, >98%; in safflower oil) per day for 21days (~2,436,000ng total BDE-209 exposure over this uptake period), followed by a 25-day depuration period. Control males (n=11) received the safflower vehicle only. In the exposed birds, BDE-209 was quantifiable in all plasma (end of uptake and depuration period) as well as liver and fat (end of depuration only) samples. The mean (±SE) BDE-209 level in plasma was 1474±1145ng/g wet weight (ww) at the end of the uptake period, and was significantly (p<0.001) lower (88%) at 174±148ng/g ww after the 25day depuration period. This equates to a mean reduction rate of 52ng/g ww per day and a rough estimation of the BDE-209 half-life in plasma of approximately 14days. The mean (±SE) BDE-209 levels were 4668±6192ng/g ww in the fat, and 338±311ng/g ww in the liver, of exposed individuals, which were significantly (p≤0.001) greater than mean concentrations (25±20 in fat and 2.6±0.9ng/g ww in liver) in the control birds. In addition to BDE-209, lower brominated PBDE congeners, and mainly meta- and para-debromination products of BDE-209 were also quantified in plasma, liver and/or fat. We estimated based on the dose that at least 80% of the non-BDE-209 concentration in the kestrel tissues and plasma must be derived from BDE-209 debromination by the kestrels. Where quantifiable, lower brominated PBDE concentrations were significantly (0.023>p>0.001) higher in the exposed relative to the control bird samples (except for BDE-154 and -153 in fat). Additional PBDE congeners found in plasma included nona-BDEs (208, 207 and 206), followed by octa-BDEs (197, 196, 201 and 203), and in liver and/or fat, the hepta-BDEs 180 and 183 and BDE-153. Higher hepatic EROD activity (cytochrome P450 1A1 monooxygenase-mediation) in the exposed birds compared to control birds was strongly suggested to be PBDE-induced, and was consistent with BDE-209 and congener metabolism in the exposed kestrels. The mean EROD activity rate was 36.1pmol/min/mg protein relative to the (n=4) control birds whose activity was just above the detection limit (10.3pmol/min/mg protein). Overall, the results demonstrated that following diet exposure of kestrels to high purity BDE-209, uptake occurred as well as BDE-209 degradation via debromination to lower brominated PBDE congeners.

Effects of decabromodiphenyl ether (BDE-209) on inter-specific competition between two species of marine bloom-forming microalgae

Decabromodiphenyl ether (BDE-209), a new kind of persistent organic pollutants, was selected to investigate its influence on population growth and inter-specific competition between two species of marine bloom-forming microalgae, Heterosigma akashiwo and Karenia mikimotoi. (1)BDE-209 showed acute toxic effects on both microalgae and H. akashiwo was more sensitive from view of 96 h-EC₅₀ and the ultrastructure variation. (2)The microalgal population growth patterns in mono-culture were density-dependent and the growth of both species in the normal co-culture was significantly depressed by competition (P<0.05) with different initial biomass ratios. BDE-209 exposure significantly changed the growth. (3) Lotka-Volterra competition model was used to simulate the interaction between the microalgae. BDE-209 exposure broke the competitive balance to make competition gradually shift in favor of H. akashiwo. Results suggested BDE-209 did have toxic effects on either microalgal growth or the inter-specific competition, which was quite different from previous reports. Further exploration of the mechanism is needed.

Spatial learning and memory deficit of low level polybrominated diphenyl ethers-47 in male adult rat is modulated by intracellular glutamate receptors

Polybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, are extensively diffused in the environment. Of particular concern are the reported highly sensitivity of PBDEs in children or developmental animals, however, almost no information is available on their potential effects on adults and the mechanisms are still unknown. In the present study, we investigated the neurotoxic effects of sub-chronic PBDE-47 exposure on adult male Sprague-Dawley rats. Thus, PBDE-47, 0.1, 0.5 and 1 mg/kg per day was administered to rats by gavage for 30 days. The learning and memory function was tested by Morris water maze. Further, in order to explore the potential mechanism, the expression of NMDA-receptors was evaluated by using both immunohistochemistry (IHC) and RT-PCR. Our results showed that sub-chronic exposure to PBDE-47 produced learning and memory deficits in male adult rats. Also, significant decrease in the CA1, CA3 and dentate gyrus areas of hippocampus affected by all three doses of PBDE-47 on the expression of NR(1), NR(2)B and Glu were found by IHC. In addition, the evaluation of expression of the NR(1), NR(2)B and NR(2)C showed statistically significant decrease in mRNA expression in rats exposed to PBDE-47. These findings showed that sub-chronic exposure to PBDE-47 could also induce behavioral alterations and the neurotoxic effects might due to the down-regulation expression of NMDA receptors. Our data indicated that the possibility of exposure of adults to PBDE-47 warranted further studies to characterize their potential neurotoxicity.

Polybrominated diphenyl ethers disrupt molting in neonatal Daphnia magna

Polybrominated diphenyl ethers (PBDEs) are flame-retardants which can bioaccumulate and biomagnify and are found worldwide despite their banned usage in some countries. In recent years, the possibility that PBDEs may disrupt endocrine functions in vertebrates has been well investigated, but little attention has been paid to the endocrine disrupting potential in aquatic invertebrates. The current study aimed to investigate whether PBDEs affect molting in neonatal Daphnia magna. Prior to molting studies, 48 h LC50 values were tested for several environmentally prevalent PBDEs: PBDEs-28, -47, -99, -100 and -209. The 48 h LC50s determined were 110.7, 7.9, 2.6, and 11.1 μg/L for PBDEs-28, -47, -99, and -100, respectively, but the highest concentration of PBDEs-209 tested (2.5 mg/L) did not affect survival at 48 h. Sublethal concentrations of these were used to investigate their potential effects on molting, assessed by the time taken to reach 4 molts. Molting studies found that PBDE-28 at 12 μg/L significantly increased the time it took to complete 4 molts. PBDE-47 at 20 μg/L inhibited daphnid molting initially but such an inhibitory effect disappeared with the prolongation of exposure due to the death of sensitive individuals. No other PBDEs affected molting at the concentrations tested, while still maintaining relatively high survival rates. In conclusion, this study found that PBDEs-28 and -47 can delay molting at μg/L concentrations, which raises concern for disrupted molting in crustaceans exposed to PBDEs.

Policy relevant results from an expert elicitation on the human health risks of decabromodiphenyl ether (decaBDE) and hexabromocyclododecane (HBCD)

AIM

Apply a recently developed expert elicitation procedure to evaluate the state of the current knowledge of the two brominated flame retardants (BFRs) most commonly used today; decabromo-diphenyl ether (decaBDE) and hexabromocyclododecane (HBCD) and their potential impact on human health in order to support policy considerations. This expert elicitation was organized by the HENVINET (Health and Environment Network) Consortium.

METHOD

The HENVINET expert elicitation procedure that was used in the evaluations of decaBDE and HBCD is a rapid assessment tool aimed at highlighting areas of agreement and areas of disagreement on knowledge-related key issues for environment and health policy decision making.

RESULTS

The outcome of the expert consultation on BFRs was concrete expert advice for policy makers with specific priorities for further action made clear for both stakeholders and policy makers. The experts were not in agreement whether or not the knowledge currently available on decaBDE or HBCD is sufficient to justify policy actions, but most experts considered that enough data already exists to support a ban or restriction on the use of these compounds. All experts agreed on the necessity of more research on the compounds. Priority issues for further research were, among others:• more studies on the extent of human exposure to the compounds.• more studies on the fate and concentration in the human body of the compounds.

Characterizing the optimal operation of photocatalytic degradation of BDE-209 by nano-sized TiO2

Brominated flame retardants have been widely used in industry. There is a rapid growing public concern for their availabilities in the environment. Advanced oxidation process (AOP) is a promising and efficient technology which may be used to remove emerging chemicals such as brominated flame retardants. This study aims at investigating optimal operational conditions for the removal of BDE-209 using nano-scaled titanium(IV) oxide. The residual PBDE congeners after photocatalytical degradation of BDE-209 by TiO2 were analysed by gas chromatography-mass spectrometry (GC-MS). It was found that the degradability of BDE-209 by TiO2 was attributed to its photocatalytic activity but not the small size of the particles. The half-life of removing BDE-209 by TiO2 was 3.05 days under visible light. Tetra- and penta-BDEs were the major degraded products of BDE-209. Optimum conditions for photocatalytical degradation of BDE-209 was found to be at pH 12 (93% +/- 1%), 5, 10, 20 mg/L (93.0% +/- 1.70%, 91.6% +/- 3.21%, 91.9% +/- 0.952%, respectively), respectively of humic acid and in the form of anatase/rutile TiO2 (82% +/- 3%). Hence, the efficiency of removing BDE-209 can be maximized while being cost effective at the said operating conditions.

Cancer risk assessment of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in former agricultural soils of Hong Kong

The major objective of this study was to evaluate the carcinogenic risk posed to humans through PBDEs and PCBs of changing agricultural land use for recycling of e-waste and open burning of municipal waste. Nine locations were selected to represent 6 different types of land use such as e-waste dismantling workshop (EW (DW)) and e-waste open burning site (EW (OBS)). The total concentrations for PBDEs and PCBs, and the bioaccessibility of PCBs were determined using Soxhlet extraction and in vitro simulated gastric solution, respectively. Both total and bioaccessible concentrations were subsequently used to establish the cancer risk probabilities in humans via ingestion, dermal contact and inhalation of soil particles. It was found that very low cancer risk in all 6 types of different land use was caused by BDE-209. Nevertheless, at the 95th centile, the concentration of PCBs in EW (DW) and EW (OBS) indicate a low cancer risk to humans of 40 and 2.1 in a million, respectively, while the same was also observed for the bioaccessible PCBs in EW (DW) of 1.71 ± 2.96 in a million.

Effect of decabromodiphenyl ether (BDE 209) and dibromodiphenyl ether (BDE 15) on soil microbial activity and bacterial community composition

There is now increasing concern regarding the effect of polybrominated diphenyl ethers (PBDEs) on the environment. These compounds are widely used as fire retardants and by the electronic industry. Our study examined the effects of adding different doses of BDE 15 and BDE 209 on the soil microbial activities and function by using denaturing gradient gel electrophoresis (DGGE), fluorescence in situ hybridization (FISH) and soil enzymatic activity analyses. Soils were spiked with 1, 10, and 100 mg kg(-1) BDE 209 and BDE 15, respectively, and incubated for up to 180 days. No degradation of BDE 209 was observed; however, about 40% of the added BDE 15 underwent declining extractable concentration. Bacterial counts were significantly higher in the microcosms amended with BDE 15, while the suppression effect increased as the BDE 209 concentration increased. Pseudomonas, Bacillus and uncultured bacteria dominated the bacterial communities in all soil treatments, and PCA analysis showed that high doses of BDE 209 and BDE 15 altered the soil microbial community structure. This study provides new information on the effect of higher and lower PBDEs on the soil microbial community in an aerobic environment.

An oral developmental neurotoxicity study of decabromodiphenyl ether (DecaBDE) in rats

BACKGROUND

Decabromodiphenyl ether (DecaBDE; CASRN 1163-19-5) is a flame retardant used in a variety of manufactured products. A single oral dose of 20.1 mg/kg administered to mice on postnatal day 3 has been reported to alter motor activity at 2, 4, and 6 months of age.

METHODS

To further evaluate these results, a developmental neurotoxicity study was conducted in the most commonly used species for studies of this type, the rat, according to international validated testing guidelines and Good Laboratory Practice Standards. DecaBDE was administered orally via gavage in corn oil to dams from gestation day 6 to weaning at doses of 0, 1, 10, 100, or 1,000 mg/kg/day. Standard measures of growth, development, and neurological endpoints were evaluated in the offspring. Motor activity was assessed at 2 months of age. Additional motor activity assessments were conducted at 4 and 6 months of age. Neuropathology and morphometry evaluations of the offspring were performed at weaning and adulthood.

RESULTS

No treatment-related neurobehavioral changes were observed in detailed clinical observations, startle response, or learning and memory tests. No test substance-related changes were noted in motor activity assessments performed at 2, 4, or 6 months of age. Finally, no treatment-related neuropathological or morphometric alterations were found.

CONCLUSIONS

Under the conditions of this study, the no-observed-adverse-effect level for developmental neurotoxicity of DecaBDE was 1,000 mg/kg/day, the highest dose tested.

Understanding the mismatch between the demands of risk assessment and practice of scientists--the case of Deca-BDE

This review describes how a mismatch between the knowledge produced by scientists and the evidence demanded by regulators has emerged, and how society has struggled to find definitive answers to questions of safety, for an important flame retardant chemical in current use - Deca-BDE. This has involved two key disciplines: analytical chemistry and toxicology. Within the chemistry, a lack of standardized methodologies among scientists has resulted in a persistent yet largely undeclared failure to replicate results within the discipline. Within the toxicology, the quest for innovative, curiosity-driven research by university scientists in preference to using validated standard protocols, designed to promote consistency within the risk assessment process, has prompted questions about the credibility and relevance of scientific findings. Yet scientific laboratories have compelling reasons to do things the way they do in the cause of producing new knowledge, pointing to a sustained gap between the aims and practices of research scientists and those of risk management. A more rigorous scientific process that treats different elements of input data as discrete pieces of evidence is needed to ensure that science rather than politics will always define chemical safety.

Is decabromodiphenyl ether (BDE-209) a developmental neurotoxicant?

Polybrominated diphenyl ether (PBDE) flame retardants have become ubiquitous environmental pollutants. The relatively higher body burden in toddlers and children has raised concern for their potential developmental neurotoxicity, which has been suggested by animal studies, in vitro experiments, and recent human epidemiological evidence. While lower brominated PBDEs have been banned in several countries, the fully brominated decaBDE (BDE-209) is still utilized, though manufacturers will discontinue production in the U.S.A. in 2013. The recent decision by the U.S. Environmental Protection Agency to base the reference dose (RfD) for BDE-209 on a developmental neurotoxicity study has generated some controversy. Because of its bulky configuration, BDE-209 is poorly absorbed and does not easily penetrate the cell wall. Its acute and chronic toxicities are relatively low, with the liver and the thyroid as the primary targets, though there is some evidence of carcinogenicity. A few animal studies have indicated that BDE-209 may cause developmental neurotoxicity, affecting motor and cognitive domains, as seen for other PBDEs. Limited in vivo and in vitro studies have also evidenced effects of BDE-209 on thyroid hormone homeostasis and direct effects on nervous cells, again similar to what found with other lower brominated PBDEs. In contrast, a recent developmental neurotoxicity study, carried out according to international guidelines, has provided no evidence of adverse effects on neurodevelopment, and this should be considered in a future re-evaluation of BDE-209. While estimated exposure to BDE-209 in children is believed to be several orders of magnitude below the most conservative RfD proposed by the USEPA, questions remain on the extent and relevance of BDE-209 metabolism to lower brominated PBDEs in the environment and in humans.

Comparative tissue distribution, biotransformation and associated biological effects by decabromodiphenyl ethane and decabrominated diphenyl ether in male rats after a 90-day oral exposure study

Recent reports indicate that decabromodiphenyl ethane (DBDPE) has become widespread in the environment. Yet databases regarding its bioavailability, biotransformation, and possible toxic effects to wildlife and humans are lacking. In this study, we investigated the bioconcentration and biotransformation of DBDPE after oral exposure and compared the results with those of decabrominated diphenyl ether (BDE-209) using rats as a model. Male rats were orally administrated with corn oil containing 100 mg/kg bw/day of DBDPE or BDE-209 for 90 days, after which the levels of DBDPE and BDE-209 in the liver, kidney, and adipose were measured. Biochemical parameters, including thyroid hormone levels, 13 clinical chemistry parameters, and the mRNA expression levels of certain enzymes were also monitored. Results showed DBDPE was found in all tissues with concentrations 3-5 orders of magnitude lower than BDE-209. At least seven unknown compounds were observed in the DBDPE-exposed rats, indicating that DBDPE biotransformation occurred in rats. These compounds were identified by comparing relative retention times and full-scan mass spectra of DBDPE debrominated products from a photolytic degradation experiment using GC/EI-MS and GC/ECNI-MS analysis. The results showed that debromination of DBDPE to lower brominated BDPEs were not the primary metabolic pathway observed in rats. Two of the metabolites were proposed tentatively as MeSO(2)-nona-BDPE and EtSO(2)-nona-BDPE using GC/EI-MS, but their structures require further confirmation by other techniques and authentic standards. In addition, evidence of a biological response to DBDPE and BDE-209 and their metabolites in rats are different. To our knowledge, these results are the first indications for the biotransformation of DBDPE in biota. Further studies are necessary to investigate the metabolites of DBDPE and their mechanisms of toxicities to assess the potential risks of DBDPE.

The potential of selected brominated flame retardants to affect neurological development

Various brominated flame retardants (BFR), including polybrominated diphenyl ether (PBDE) congeners, hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), are commonly used in household items and electronics and have been detected in the environment and/or the bodily fluids of people, including children. Some studies in animals suggest that exposure to PBDE congeners, HBCD, or TBBPA during the perinatal period may affect locomotor activity and/or memory and learning. Epidemiological studies showing similar effects in humans, however, are lacking. To assess whether an association exists between perinatal exposure and development of consistent neurobehavioral alterations, published animal studies investigating perinatal exposure to PBDE congeners, HBCD, or TBBPA with specific neurobehavioral evaluations-particularly, assessments of motor activity-were reviewed for consistency of results. Our analysis shows that although the majority of studies suggest that perinatal exposure affects motor activity, the effects observed were not consistent. This lack of consistency includes the type of motor activity (locomotion, rearing, or total activity) affected, the direction (increase or decrease) and pattern of change associated with exposure, the existence of a dose response, the permanency of findings, and the possibility of gender differences in response. Interestingly, Good Laboratory Practices (GLP)-compliant studies that followed U.S. Environmental Protection Agency (EPA)/Organization for Economic Cooperation and Development (OECD) guidelines for developmental neurotoxicity testing found no adverse effects associated with exposure to PBDE209, HBCD, or TBBPA at doses that were orders of magnitude higher and administered over longer durations than those used in the other studies examined herein. The lack of consistency across studies precludes establishment of a causal relationship between perinatal exposure to these substances and alterations in motor activity.