Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of growing concern, as they have been detected in both humans and wildlife and have been shown to be toxic. Recent studies have indicated ...that OH-PBDEs can be more toxic than PBDEs, partly due to their ability to disrupt oxidative phosphorylation (OXPHOS), an essential process in energy metabolism. In this study, we determined the OXPHOS disruption potential of 18 OH-PBDE congeners reported in marine wildlife using two in vitro bioassays, namely the classic rat mitochondrial respiration assay, and a mitochrondrial membrane potential assay using zebrafish PAC2 cells. Single OH-PBDE congeners as well as mixtures were tested to study potential additive or synergistic effects. An environmental mixture composed of seven OH-PBDE congeners mimicking the concentrations reported in Baltic blue mussels were also studied. We report that all OH-PBDEs tested were able to disrupt OXPHOS via either protonophoric uncoupling and/or inhibition of the electron transport chain. Additionally we show that OH-PBDEs tested in combinations as found in the environment have the potential to disrupt OXPHOS. Importantly, mixtures of OH-PBDEs may show very strong synergistic effects, stressing the importance of further research on the in vivo impacts of these compounds in the environment.
Among all brominated flame retardants in use, the polybrominated diphenyl ethers (PBDEs) have been identified as being of particular environmental concern due to their global distribution and ...bioaccumulating properties, as observed in humans and wildlife worldwide. Still there is a need for more data on the basic characteristics of PBDEs to better understand and describe their environmental fate. Hence, the aim of this study was to investigate the photochemical degradation of PBDEs with different degrees of bromination. The photochemical degradation of 15 individual PBDEs substituted with 4−10 bromine atoms was studied in methanol/water (8:2) by UV light in the sunlight region. Nine of these were also studied in pure methanol, and four of the nine PBDEs were studied in tetrahydrofuran. The photochemical reaction rate decreased with decreasing number of bromine substituents in the molecule but also in some cases influenced by the PBDE substitution pattern. The reaction rate was dependent on the solvent in such a way that the reaction rate in a methanol/water solution was consistently around 1.7 times lower than in pure methanol and 2−3 times lower than in THF. The UV degradation half-life of decaBDE (T 1/2 = 0.5 h) was more than 500 times shorter than the environmentally abundant congener 2,2‘,4,4‘-tetraBDE (T 1/2 = 12 d) in methanol/water. The quantum yields in the methanol/water solution ranged from 0.1 to 0.3. The photochemical reaction of decaBDE is a consecutive debromination from ten- down to six-bromine-substituted PBDEs. Products with less than six bromines were tentatively identified as brominated dibenzofurans and traces of what was indicated as methoxylated brominated dibenzofurans.
Polybrominated diphenyl ethers (PBDEs), used as flame retardants, have been shown to be increasing in the environment and in human mother's milk. We have earlier reported that lower brominated PBDEs, ...such as tetra-, penta-, and hexa-brominated diphenyl ethers, can cause developmental neurotoxic effects in mice. Recently, this was also observed with the full-brominated PBDE, deca-brominated diphenyl ether (PBDE 209), although it was suggested that the effects were caused by a (possibly debrominated) metabolite thereof. The present study revealed that 2,2′,3,3′,4,4′,5,5′,6-nonabromodiphenyl ether (PBDE 206), 2,2′,3,4,4′,5,5′,6-octabromodiphenyl ether (PBDE 203), and to a minor extent also 2,2′,3,4,4′,5′,6′-heptabromodiphenyl ether (PBDE 183) can induce developmental neurotoxic effects. Neonatal Naval Medical Research Institute male mice were exposed on postnatal day 3 or 10 to PBDE 206, PBDE 203, or PBDE 183, given as a single oral dose of 21 μmol/kg body weight. At the adult age of 2–3 months, the mice were observed for performance in a spontaneous behavior test and the Morris water maze test. PBDE 203 and PBDE 206, when administered on neonatal day 10, caused disturbances in spontaneous behavior, leading to disrupted habituation and a hyperactive condition in adults at the age of 2 months. These behavioral changes were also seen in 2-month-old mice exposed to PBDE 203 on neonatal day 3. Furthermore, exposure to PBDE 203 on neonatal day 10 affected learning and memory functions in adult mice. The developmental neurotoxic effects were most pronounced in mice exposed to PBDE 203. These developmental neurobehavioral defects were in agreement with those we observed previously with lower brominated PBDEs and with PBDE 209. It is important to consider the fact that different PBDE congeners can have differing degrees of potency, when comparing levels of PBDEs in the environment and in mother's milk.
Objective: Our aim was to investigate exposure to polybrominated diphenyl ethers (PBDEs) in a young urban population in a developing country, with focus on potentially highly exposed children working ...informally as scrap scavengers at a large municipal waste disposal site. We also set out to investigate whether hydroxylated metabolites, which not hitherto have been found retained in humans, could be detected. Methods: We assessed PBDEs in pooled serum samples obtained in 2002 from children 11-15 years of age, working and sometimes also living at the municipal waste disposal site in Managua, and in nonworking urban children. The influence of fish consumption was evaluated in the children and in groups of women 15-44 years of age who differed markedly in their fish consumption. Hydroxylated PBDEs were assessed as their methoxylated derivates. The chemical analyses were performed by gas chromatography/mass spectrometry, using authentic reference substances. Results: The children living and working at the waste disposal site showed very high levels of medium brominated diphenyl ethers. The levels observed in the referent children were comparable to contemporary observations in the United States. The exposure pattern was consistent with dust being the dominating source. The children with the highest PBDE levels also had the highest levels of hydroxylated metabolites. Conclusions: Unexpectedly, very high levels of PBDEs were found in children from an urban area in a developing country. Also, for the first time, hydroxylated PBDE metabolites were found to bioaccumulate in human serum.
Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and hydroxylated PBDEs (OH-PBDEs) have recently been identified in fish and wildlife from the Baltic Sea. Both OH-PBDEs and MeO-PBDEs are known ...natural products, while OH-PBDEs also may be metabolites of PBDEs. The aim of the present study was to determine if the red macroalga Ceramium tenuicorne could be a source for MeO- and OH-PBDEs in the Baltic environment. Blue mussels (Mytilus edulis) from the same area were also investigated for their content of MeO- and OH-PBDEs. Seven OH-PBDEs and four MeO-PBDEs were present both in the red macroalga and the blue mussels. The mussels also contained a monochlorinated OH-tetraBDE. One of the compounds, 6-methoxy-2,2‘,3,4,4‘,5-hexabromodiphenyl ether, has never been reported to occur in the environment. The identification was based on comparison of relative retention times with reference standards, on two gas chromatographic columns of different polarities, together with comparisons of full-scan electron capture negative ionization (ECNI) and electron ionization (EI) mass spectra. It is shown that MeO-PBDEs and OH-PBDEs are present in algae, but at this stage it could not be confirmed if the compounds are produced by the alga itself or by its associated microflora and/or microfauna.
Faeces from day 1–5 of orally administered 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in rat have been analysed for hydroxylated metabolites. Six hydroxylated tetrabrominated diphenyl ethers, as ...well as three hydroxylated tribrominated diphenyl ethers found, were structurally identified. They were 2′-hydroxy-2,4,4′-tribromodiphenyl ether, 3′-hydroxy-2,4,4′-tribromodiphenyl ether, 4′-hydroxy-2,2′,4-tribromodiphenyl ether, 6-hydroxy-2,2′,4,4′-tetrabromodiphenyl ether, 2′-hydroxy-2,3′,4,4′-tetrabromodiphenyl ether, 3-hydroxy-2,2′,4,4′-tetrabromodiphenyl ether, 5-hydroxy-2,2′,4,4′-tetrabromodiphenyl ether, 4′-hydroxy-2,2′,4,5′-tetrabromodiphenyl ether and 4-hydroxy-2,2′,3,4′-tetrabromodiphenyl ether. The analysis was performed using gas chromatography–mass spectrometry (GC–MS). The identification of the hydroxylated polybrominated diphenyl ether (OH-PBDE) metabolites in the rat faeces was supported by similar relative retention times (RRTs) versus 2,2′,3,4,4′,5-hexabromodiphenyl ether (BDE-138) on two columns of different polarities compared to the authentic references. The identification of the OH-PBDE metabolites was also supported by full scan electron ionisation mass spectra. Two of the identified OH-PBDE metabolites have identical structures as natural products, which previously have been isolated from marine sponges and an ascidian.
Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified as metabolites of PBDEs, and also as compounds of natural origin in the marine environment; however, there has only been ...very limited study of their presence in the abiotic environment. In the present study, OH-PBDEs were determined in samples of surface water and precipitation (rain and snow) collected from sites in Ontario, Canada. OH-PBDEs were detected in all the samples analyzed, although half of the observed peaks did not correspond to any of the 18 authentic standards available. Fluxes of ΣOH-PBDEs ranged from 3.5 to 190 pg/m2 in snow and from 15 to 170 pg/m2/day in rain, and those were higher at three of the southern Ontario locations relative to a single northern remote site. Concentrations of ΣOH-PBDEs ranged from 2.2 to 70 pg/L in water and from <1 to 420 pg/g in particulate organic carbon (POC), and higher values were found near sewage treatment plant (STP) outfalls in Lake Ontario. Partition coefficients (log K oc) for OH-PBDEs ranged from 4.0 to 5.1. The results in this study suggest that OH-PBDEs are ubiquitous in the abiotic environment and most likely are produced through reaction of PBDEs with atmospheric OH radicals. As well, they may be present in surface waters near STPs due to oxidation of PBDEs and inflows from metabolism by humans and animals.
Methoxylated and hydroxylated polybrominated diphenyl ethers (MeO-PBDEs and OH-PBDEs) have recently been reported to be present in wildlife from Northern Europe. The structures of a majority of these ...compounds have however been unknown. In the present study, nine OH-PBDEs and six MeO-PBDEs were identified in Baltic Sea salmon (Salmo salar) blood. All OH- and MeO-PBDEs identified were substituted with four or five bromines, and five of these had one chlorine substituent. Fourteen of the OH- and MeO-PBDEs have the methoxy or hydroxy group substituted in the ortho position to the diphenyl ether bond. Identification was done by comparison of relative retention times of authentic reference standards with compounds present in salmon plasma on two gas chromatographic columns of different polarities. The identification was supported by comparisons of full-scan mass spectrometric data: electron ionization (EI) and electron capture negative ionization (ECNI). Nine of the 15 OH- and MeO-PBDEs identified have not previously been reported to occur in the environment. The structures of several identified OH- and MeO-PBDEs support natural origin. However, at least one of the OH-PBDEs may be a hydroxylated metabolite of anthropogenic polybrominated diphenyl ether (PBDE).
Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their use as flame retardants. Similarly to PCBs, the PBDEs are metabolized to hydroxylated metabolites ...(OH-PBDEs) in mammals. In the present study equimolar doses of seven environmentally relevant PBDE congeners were given intraperitoneally as a mixture to rats, and their blood plasma was analyzed for parent compounds and hydroxylated metabolites 1 and 5 days after dosing. Sixteen OH-PBDEs and two diOH-PBDEs were detected as PBDE metabolites in the rat plasma, a novel finding. Four OH-tetraBDEs were structurally identified by comparison (gas chromatography/mass spectrometry) with authentic reference standards. The position of the hydroxyl groups was suggested according to the mass spectrometric fragmentation patterns of the corresponding PBDE methyl ether derivatives. The OH-PBDE metabolites were dominated by hydroxyl groups in the meta- and para-positions. The results show that OH-PBDE congeners have an ability to be retained in rat blood, most likely by a mechanism similar to that of OH-PCBs. The results will be useful for determination of the origin of OH-PBDEs present in wildlife and in humans, since OH-PBDEs are also common natural products in marine environments.
The fate of polybrominated diphenyl ethers (PBDEs) in sewage sludge after agricultural application was analysed. This study was based on the analysis of sewage sludge and sludge amended soil samples ...collected during 2005. PBDE concentrations in sewage sludge ranged from 197 to 1185
ng/g dry weight (dw), being deca-BDE-209 the predominant congener. PBDE levels in soils ranged between 21 and 690
ng/g dw, being BDE-209 also the predominant congener in all soil samples. Sewage-sludge amendment at the research stations increased concentrations of all BDE congeners 1.2- to 45-fold, with the highest increases for BDE-209. Results obtained evidenced the cumulative effect of the sludge application rates. Moreover, high levels found at soils four years after the last sludge application indicate persistence of PBDEs in soils, including deca-BDE-209.
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