Brominated-chlorinated diphenyl ethers formed by thermolysis of polybrominated diphenyl ethers at low temperatures

Polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants (BFRs) used mainly as additives in different kinds of plastic material. Various PBDEs are found in all environmental compartments as well as in tissue and blood serum of animals and humans due to their persistence and tendency to bioaccumulate. Emission of PBDEs into the environment can occur during recycling of PBDE-containing plastic material or during their uncontrolled or insufficient combustion as e.g. in accidental fires or landfill fires. Under these circumstances, PBDEs can also function as precursor molecules for the formation of polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). In this study, we qualitatively investigated the reaction of two PBDE congeners, 2,2′,4,4′-tetrabromo diphenyl ether (BDE 47) and 2,2′,4,4′,5,5′-hexabromo diphenyl ether (BDE 153), as well as hexabromobenzene (HBB), a flame retardant used in the past, when exposed to temperatures between 250 °C and 500 °C. The formed reaction products were analysed by high resolution gas chromatography–low resolution mass spectrometry (HRGC-LRMS). Among others brominated–chlorinated diphenyl ethers were formed by chlorodebromination of the PBDEs. In addition, thermolysis of BDE 47 and BDE 153 in the presence of tetrachloromethane as model substance for an organic chlorine source was studied. Thermal treatment of HBB resulted in the formation of brominated–chlorinated benzenes.     

Hydroxylated and methoxylated polybrominated diphenyl ethers and polybrominated dibenzo-p-dioxins in red alga and cyanobacteria living in the Baltic Sea

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) are present in the ecosystem of the Baltic Sea. OH-PBDEs are known to be both natural products from marine environments and metabolites of the anthropogenic polybrominated diphenyl ethers (PBDEs), whereas, MeO-PBDEs appear to be solely natural in origin. Polybrominated dibenzo-p-dioxins (PBDDs) are by-products formed in connection with the combustion of brominated flame retardants (BFRs), but are also indicated as natural products in a red alga (Ceramium tenuicorne) and blue mussels living in the Baltic Sea. The aims of the present investigation were to quantify the OH-PBDEs and MeO-PBDEs present in C. tenuicorne; to verify the identities of PBDDs detected previously in this species of red alga and to investigate whether cyanobacteria living in this same region of the Baltic Sea contain OH-PBDEs, MeO-PBDEs and/or PBDDs. The red alga was confirmed to contain tribromodibenzo-p-dioxins (triBDDs), by accurate mass determination and additional PBDD congeners were also detected in this sample. This is the first time that PBDDs have been identified in a red alga. The SigmaOH-PBDEs and SigmaMeO-PBDEs concentrations, present in C. tenuicorne were 150 and 4.6 ng g(-1) dry weight, respectively. In the cyanobacteria 6 OH-PBDEs, 6 MeO-PBDEs and 4 PBDDs were detected by mass spectrometry (electron capture negative ionization (ECNI)). The PBDDs and OH-PBDEs and MeO-PBDEs detected in the red alga and cyanobacteria are most likely of natural origin.     

Theoretical study on the chemical properties of polybrominated diphenyl ethers

Density functional theory calculations at the B3LYP/6-31+G(d) and B3LYP/aug-cc-pVDZ levels were performed to obtain the equilibrium structures, thermodynamic properties, and electron affinities (EA) of 14 polybrominated diphenyl ether (PBDE) congeners in the gas phase. All congeners except for those of symmetric BDE are found to have two or more conformational isomers. The optimized geometries of the most stable conformational isomers are in agreement with recently published X-ray crystallographic data. The thermodynamic properties of the congeners with a given number of bromine substitutions are strongly dependent on the substitution pattern, whereas the EA values also depend on the number of bromine substitutions. The vertical electron affinities (EA(Ver)) calculated for the selected BDE congeners at the B3LYP/aug-cc-pVDZ level are all positive except for di-BDEs, and are correlated with the initial reductive debromination rate constants obtained recently [Keum, Y.-S., Li, Q.X., 2005. Reductive debromination of polybrominated diphenyl ethers by zerovalent iron. Environ. Sci. Technol. 39, 2280]. All adiabatic electron affinities (EA(Ada)) are positive, and suggest that the BDE congeners act as electron acceptors when reacting with receptors in living cells. The calculated EA(Ada) values differ considerably from those of EA(Ver) because of the large geometrical relaxation from the neutral to the anionic BDE congeners, highlighted by the lengthening of a C-Br bond. The elongated C-Br bond, which occurs at the alpha position, is directly involved in the debromination of n-bromodiphenyl to (n-1)-bromodiphenyl ethers in the reductive debromination experiments.     

Assessment of polybrominated diphenyl ethers in eggs of waterbirds from South China

Concentrations of total polybrominated diphenyl ethers (PBDEs) in Ardeid eggs from Hong Kong, Xiamen and Quanzhou in south China ranged from 140-1000, 30-550 and 140-380ngg(-1), lipid wt., respectively. There were spatial and interspecies variations in the abundance and congeneric profiles of PBDEs. The different congeneric profiles observed among the study sites may be associated with the developmental phases of the cities, as well as a possible consequence of debromination of BDE209. Marked concentrations of higher-brominated diphenyl ethers (BDEs 183, 196, 197, 206, 207 and 209) were detected in the egg samples from all sites, probably indicating uptake of BDE209 by top predators, and that there is widespread occurrence of BDE209 in south China. Comparisons of egg concentrations of BDEs 47, 99, 153 and 209 with tentative critical concentrations for neurobehavioral effects and oxidative stress indicated some potential risks for BDE99 and BDE209 in the Ardeid populations.     

Spectral characterization of two bioaccumulated methoxylated polybrominated diphenyl ethers

Two methoxylated polybrominated diphenyl ethers (MeO-PBDEs) were isolated from a True's beaked whale (Mesoplodon mirus) and identified by NMR (1H, 1H-1H and 1H-13C) and high resolution mass spectrometry as 2-(2',4'-dibromophenoxy)-3,5-dibromoanisole (6-MeO-BDE47) and 2-(2',4'-dibromophenoxy)-4,6-dibromoanisole (2'-MeO-BDE68). Previously the structures of these bioaccumulated compounds have been determined by comparison of their mass spectra and gas chromatographic (GC) retention times with those of authentic standards. While this method is accepted and generally successful, NMR of the isolated compounds allows us to definitively identify the congeners. Our characterizations are consistent with those made for MeO-PBDEs in other organisms, identified by chromatographic methods.     

The occurrence of polybrominated diphenyl ethers in river and coastal biota from Portugal

Throughout this work PBDEs level determination in biota was developed for the first time in Portugal. The data obtained was important to provide a global perspective of Portugal contamination by PBDEs and allows the comparison with studies made in other countries. Environmental levels of fourteen polybrominated diphenyl ethers (PBDEs) were analysed in a number of biota samples (Barbus sp. and Mytilus galloprovincialis) taken over a large geographic range covering five rivers and coastal areas of Portugal. Tetrabromodiphenyl ether (BDE 47) was found in almost all samples ranging from not detected (nd) to 30ngg(-1) dry weight (dw). BDE 47 concentration is correlated with mussels weight indicating the bioaccumulation of this compound. Pentabromodiphenyl ethers (BDE 99 and BDE 100) were detected in several samples, but in lower concentrations.     

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) in biosolids from municipal wastewater treatment plants in China

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) along with methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have been frequently identified as natural compounds in marine environment and also assumed as metabolites of PBDEs. In the present study, nine OH-PBDE, nine MeO-PBDE and 10 PBDE congeners were studied in the sewage sludge collected from 36 municipal wastewater treatment plants (WWTPs) in 27 cities of China. The results suggest that OH-PBDEs and PBDEs are ubiquitous in sewage sludge in China, however, methoxylated PBDEs were not detectable. Composition profiles of detected OH-PBDE congeners were different depending on the sampling location. ΣOH-PBDEs in WWTPs sludge ranged from 0.04 to 2.24 ng g^?1 dry weight (mean: 0.35 ng g^?1 dry weight). The total amount of the two most prominent congeners (6-OH-BDE-47 + 2′-OH-BDE-68) accounted for about 53.3–100% of the sum of all six identified congeners. A significant linear relationship was found between 6-OH-BDE-47 and 2′-OH-BDE-68. A distinct geographical distribution of ΣOH-PBDEs was observed with greater concentrations of OH-PBDEs at coastal areas than inland regions in China.     

The partitioning of alkylphenolic surfactants and polybrominated diphenyl ether flame retardants in activated sludge batch tests

Polybrominated diphenyl ethers and nonylphenol polyethoxylates have been reported to be estrogenic and may enter the aquatic environment through the discharge of treated sewage effluent. Therefore, their fate during wastewater treatment processes is an important factor in determining their environmental impact. Batch tests with activated sludge from a Husmann apparatus were used to determine the effects of physico-chemical properties and sludge characteristics on the partitioning of polybrominated diphenyl ether flame retardants and nonylphenol polyethoxylate surfactants during biological wastewater treatment. Hydrophobic compounds, those with high logK(ow) values, were sorbed more rapidly and to a greater extent to the solid phase than more soluble compounds. For these hydrophobic compounds sorption may become an increasingly important removal mechanism as sludge age and therefore solids content increase. The initial rate of partitioning was greatest for the most hydrophobic compounds but all rates diminished with time as a result of progressive saturation of sorbent binding sites, a reduction of sorbate availability and as a consequence of the system reaching equilibrium. The sorption of polybrominated diphenyl ethers fit Freundlich adsorption isotherms demonstrating generally increasing adsorption capacity and efficiency with increasing hydrophobic nature. A correlation between increasing logK(ow) and increasing organic matter content was also observed for both polybrominated diphenyl ethers and nonylphenol polyethoxylates indicating the organic content of mixed liquor will also be influential in removing compounds during wastewater treatment.     

Polychlorinated biphenyls and polybrominated diphenyl ethers in the North American atmosphere

To assess the spatial concentration variability of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the atmosphere on a large continental scale, their annually integrated air concentrations were determined in 2000/2001 using XAD-based passive air samplers (PAS). The network included 40 stations in Canada, the United States, Mexico, Belize and Costa Rica, and covered 72 degrees of latitude and longitude. Total concentrations of PCB and PBDE congeners ranged from below the detection limit to 130 ng PAS-1 and 24 ng PAS-1, respectively. PCBs displayed a large variation between urban, rural and remote sites, whereas PBDEs did not follow such a pattern. Open burning of "Penta"-containing waste may have contributed to the PBDEs detected in the air samples from rural and remote areas. Air from the Canadian Arctic had a relatively higher percentage of lighter PCB congeners than air sampled in the tropical region, which is interpreted as evidence for global fractionation.     

Leaching characteristics of polybrominated diphenyl ethers (PBDEs) from flame-retardant plastics

To investigate the effect of leachant on the leachability of polybrominated diphenyl ethers (PBDEs), we determined the leaching concentrations of PBDEs from flame-retardant plastic samples (TV housings and raw materials before molding processing) that are regarded as a source of PBDEs in landfill sites. The leachants used were distilled water, 20% methanol solution, and dissolved humic solution (DHS) of 1000 mg/l based on organic carbon. The leaching test conditions were a liquid-to-solid ratio of 100:1, and a contact period of five days, with twice-daily agitation in a temperature-controlled room of 30 degrees C without pH or ionic strength control. The leaching concentrations of PBDEs increased with increased content, and were found to be remarkably enhanced when methanol and DHS were used instead of distilled water. The enhancement of leachability in the presence of the latter was attributed to the cosolvency effect, and complex formations between the PBDEs and dissolved humic matter (DHM). PBDE concentrations in the leachate obtained from the leaching test and an actual landfill site revealed a significant presence of congeners below heptabromodiphenyl ethers (H7BDEs), detected in the leachate of the actual landfill, while significant amounts of nonabromodiphenyl ethers (N9BDEs) and decabromodiphenyl ether (D10BDE) were detected in the leachate of the leaching test.     

Occurrence of polybrominated diphenyl ethers (PBDEs) in brown trout bile and liver from Swiss rivers

The ranges of total polybrominated diphenyl ethers (PBDEs) in fish from four Swiss rivers were 0.8-240 ng/g in the bile and 16-7400 ng/g lipid in the liver. PBDE concentrations varied within each river and among the various rivers. Female fish tended to have higher concentrations in the liver, while the male fish had higher concentrations in the bile. From the resulting PBDE concentrations in fish it could not be infered that these contaminants contribute to the causes of the observed fish catch decline in Swiss rivers.     

Polybrominated diphenyl ethers and polybrominated biphenyls in Australian sewage sludge

This paper presents a brief review of the international scientific literature of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in sewage sludge and a survey of these compounds in sewage sludge from 16 Australian wastewater treatment plants (WWTPs). The SigmaPBDE mean concentration in the Australian study was 1137microgkg(-1) dry weight (d.w.) (s.d. 1116) and ranged between 5 and 4 230microgkg(-1)d.w. The urban mean of 1308microgkg(-1) (s.d. 1320) and the rural mean of 911microgkg(-1) (s.d. 831) are not statistically different and are similar to levels in European sludges. Principal components analysis was performed on the data set and revealed that 76% of the data variation could be explained by two components that corresponded to overall concentration of the pentaBDE and the decaBDE commercial formulations. An analysis of variance was performed comparing PBDEs levels at three WWTPs over the years 2005 and 2006, finding differences between treatment plants (BDE-47) but no significant difference in PBDE levels in the years 2005 and 2006. Low levels of BB-153 were detected in all samples of this survey (n=16); mean 0.6microgkg(-1)d.w. (s.d. 0.5). This compound has rarely been reported in any other study of sewage sludges undertaken outside Australia. This work highlights the need for a risk assessment of PBDEs in sewage sludge when used for land application, taking into account typical levels found in Australian sludges and soils.     

Sodium borohydride reduction of individual polybrominated diphenyl ethers

Many chemicals in use today lack appropriate documentation on their environmental properties, fate, and effects. To counteract this lack of documentation it is vital to thoroughly investigate a compound’s fate in the environment before it comes into use. The present study is describing a novel method for assessing the reduction potential of polybrominated diphenyl ethers (PBDEs), as a part of a project aimed to create an experimental model for determination of chemical persistence. The reductive transformation of 15 PBDE congeners using sodium borohydride was determined. Pseudo-first-order reaction rate constants of the transformations were determined by monitoring the disappearance of the investigated congeners. The reductions lead primarily to formation of lower brominated PBDEs. Each PBDE congener was tested in a total of ten replicates which showed a relative standard deviation of 31% or less. The decaBDE, BDE-209 was approximately 3 times as prone to reductive transformation as BDE-207. The three nonaBDEs, BDE-206, BDE-207, and BDE-208, showed similar reductive potential. The reactivity of the tested octaBDEs was quite variable, from 5% to 24% of the reactivity of BDE-209 for BDE-196 and BDE-198, respectively. The heptaBDEs studied were in the range of the less reactive octaBDEs, except for BDE-181 which was as high as 13% of the reactivity of BDE-209. The results presented give a method for measuring the propensity of PBDEs, and possibly similar compounds, to undergo reductions. They indicate a potential route to a vital piece of information in the assessment of environmental persistence of chemicals.     

Spatial distribution of polybrominated diphenyl ethers and polybrominated biphenyls in lake trout from the Laurentian Great Lakes

Concentrations of two types of brominated flame-retardants (BFRs); polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) were determined in a single age class of lake trout (Salvelinus namaycush) collected from the Laurentian Great Lakes in 1997. Mean concentrations of total PBDE were highest in samples from Lake Ontario at 95+/-22 ng/g wet weight (ww) or 434+/-100 ng/g lipid weight (lw) while the lowest concentrations were observed in Lake Erie lake trout (27+/-8.6 ng/g ww, 117+/-37 ng/g lw). In all samples, the predominant PBDE congeners were 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), and 2,2',4,4', 6-pentabromodiphenyl ether (BDE-100), which are the primary components of the commonly used penta-BDE formulation flame retardant. Lake trout collected from Lake Huron had the highest concentrations of PBBs (3.1+/-1.7 ng/g ww, 15+/-8.5 ng/g lw), while the lowest levels were detected in fish from Lake Superior (0.25+/-0.13 ng/g ww, 1.7+/-0.89 ng/g lw). In all lake trout samples, 2,2',4,4',5,5'-hexabromobiphenyl (BB-153), a major constituent of the flame-retardant FireMaster BP-6, was the predominant PBB congener.     

Particle-bound Dechlorane Plus and polybrominated diphenyl ethers in ambient air around Shanghai, China

In present study, atmospheric particles from Shanghai, the biggest city and the most important industrial base in China, were analyzed for polybrominated diphenyl ethers (PBDEs) and Dechlorane Plus (DP). Concentrations of ∑(20)PBDEs and DP both exhibited the changing trend of industrial area > urban areas. Jiading District had the highest levels of particulate PBDEs and DP with values of 744 ± 152 pg/m(3) and 5.48 ± 1.28 pg/m(3), respectively. Compared with similar data in other areas of the world, PBDEs in Shanghai were at medium pollution level, while DP was at lower level, which reflected their different production and use in Shanghai. The results from multiple linear regression analysis suggested that deca-BDE mixture was the most important contributor of particulate PBDEs in Shanghai. The fractions of anti-DP showed no significant differences to those of the technical mixtures (p > 0.05), which suggested that no obviously stereoselective process occurred in ambient air around Shanghai.     

Seasonal variations of hydroxylated and methoxylated brominated diphenyl ethers in blue mussels from the Baltic Sea

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) found at high levels in the Baltic biota are mainly natural products, but can also be formed through metabolism or abiotic oxidation of polybrominated diphenyl ethers (PBDEs). The formation of OH-PBDEs is of concern since there is growing evidence of phenolic toxicity. This study investigates seasonal variations in levels of OH-PBDEs and MeO-PBDEs, focusing on an exposed species, the blue mussel (Mytilus edulis), sampled in the Baltic Sea in May, June, August and October of 2008. Both the OH-PBDE and MeO-PBDE levels in the mussels showed seasonal variations from May to October, the highest concentration of each congener appearing in June. The seasonal variation was more marked for OH-PBDEs than in MeO-PBDEs, but all congeners showed the same trends, except 6-MeO-BDE47 and 2′-MeO-BDE68, which did not significantly decline in concentrations after June. Biotic or abiotic debromination is suggested as a possible reason for the rapid decrease in methoxylated penta- and hexa-BDE concentrations observed in blue mussels from June to August, while the tetraBDE concentrations were stable. In addition, 1,3,7/1,3,8-tribrominated dibenzo-p-dioxins showed the same seasonal variation. The seasonal variations indicates natural formation and are unlikely to be due to transformation of anthropogenic precursors. The levels of PBDEs were fairly constant over time and considerably lower than those of the OH-PBDEs and MeO-PBDEs. The timing of the peaks in concentrations suggests that filamentous macro-algae may be important sources of these compounds found in the blue mussels from this Baltic Sea location.     

Photochemical studies of a polybrominated diphenyl ethers (PBDES) technical mixture by solid phase microextraction (SPME)

In this work the photochemical behaviour of a technical mixture of polybrominated diphenyl ethers (PBDEs) (BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) has been studied. The mixture of BDEs was extracted from aqueous solutions using SPME fibers that were subsequently exposed to different UV irradiation times, procedure so-called Photo-SPME. PBDEs photochemical studies in such medium have been accomplished for the first time. Twenty one different photoproducts, all of them generated by successive bromine atoms losses, have been identified, being their photoformation-photodegradation curves easily determined by the Photo-SPME technique.     

Emission estimation and congener-specific characterization of polybrominated diphenyl ethers from various stationary and mobile sources

Here we show that combustion sources, including waste incinerators, metallurgical processes, power-heating systems and so on, are also important emitters of polybrominated diphenyl ethers (PBDEs) to the atmosphere. Geometric mean PBDE concentrations in the stack flue gases of the combustion sources ranged from 8.07 to 469 ng/Nm³. The sinter plants (24.7 mg/h), electric arc furnaces (EAFs) (11.3 mg/h) and power plants (50.8 mg/h) possessed the largest PBDE emission rates, which were several orders higher than those of the other reported sources. The occurrences of the PBDEs in the flue gases of the power plants and vehicles, as well as their PBDE concentrations statistically highly correlated with combustion-originated PCDD/Fs, revealing that PBDEs should be the products of combustion. The ranking of major PBDE emission sources in Taiwanese PBDE inventory for combustion sources was power plants (30.85 kg/year), vehicles (14.9 kg/year) and metallurgical processes (5.88 kg/year).