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.     

Pine needles as passive bio-samplers to determine polybrominated diphenyl ethers

Eight polybrominated diphenyl ethers (PBDEs) were determined in pine needles of three species (Pinus halepensis, Pinus pinea and Pinus nigra) collected in the NE Spain in an attempt to use this matrix for the biomonitoring of airborne PBDEs. The method used was based in ultrasonic extraction followed by alumina and Florisil clean-up and determination by gas chromatography coupled to mass spectrometry in negative chemical ionization. Recoveries were between 99% and 138%, limits of detection between 0.011 and 0.070 ng g⁻¹-dw (0.232 ng g⁻¹-dw for BDE 209) and repeatability lower than 13%. PBDE levels ranged between 0.027 ng g⁻¹-dw and 13.04 ng g⁻¹-dw, with predominance of BDE 209, followed by BDEs 47. P. halepensis was the species with the highest PBDE levels and P. nigra, the least, according to their widespread and remote distribution, respectively. The presence of PBDEs in pine needles was attributed to the release of in-use PBDEs, transport through atmosphere and adsorption upon lipid rich pine needles. Given the easy collection of pine needles, its ample distribution and its potential to accumulate airborne contaminants, this matrix is proposed as passive bio-sampler to be used in PBDE monitoring programs.

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Pine needles can be used to biomonitor airborne PBDEs.     

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.     

Synthesis of polybrominated diphenyl ethers via symmetrical tetra- and hexabrominated diphenyliodonium salts

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs) which have become widespread environmental pollutants due to their persistence and bioaccumulativeness. Pure authentic PBDE congeners are required for chemical analysis, assessments of their chemical/physical properties and toxicological studies. We here report an improved method for synthesis of authentic PBDE congeners applying bromophenols and symmetrical brominated diphenyliodonium salts as building blocks. Altogether, 13 PBDEs were synthesized of which seven are new. The improved coupling reaction between the bromophenol and the brominated diphenyliodonium salts resulted in enhanced yields for PBDEs substituted with more than six bromine atoms. Also, improvements in iodonium salt synthesis made it possible to synthesize symmetrical hexabromodiphenyliodonium salts for the first time, i.e. 2,2',3,3',4,4'-, 2,2',4,4',5,5'- and 2,2',4,4',6,6'-hexabromodiphenyliodonium salts and they made it possible to prepare octabrominated PBDEs via the actual coupling method. All synthesized compounds were characterized by (1)H NMR, (13)C NMR spectra and by their melting points. Also, all products except for the diphenyliodonium salts were characterized by mass spectra in electron ionization mode.     

Multi-year measurements of polybrominated diphenyl ethers (PBDEs) in the Arctic atmosphere

Weekly high-volume air samples have been collected in the Canadian High Arctic (Alert, Nunavut) since 1992. Fifteen polybrominated diphenyl ethers (PBDEs) are quantified in 104 samples over the time period of 2002–2004. To our knowledge, this study reports the first continuous multi-year measurements of PBDEs in Arctic air. Average air concentrations (in pg m⁻³) were 7.7 (0.40–47) and 1.6 (0.091–9.8) for 14 PBDEs (excluding BDE-209) and BDE-209, respectively, over the entire sampling period. BDE-28/33, 47, 99, 100, 153, 154, and 209 accounted for 90% (72–97%, n=104) of the 15 PBDEs. Occurrence of BDE-47, 99, and 209 suggests that PBDEs in Alert air were likely associated with the usage of “penta-BDE” and “deca-BDE” technical mixtures worldwide. Natural logarithm of concentrations for less brominated PBDEs correlated significantly with ambient temperatures in the summertime, suggesting importance of volatilization emissions in a local and/or regional scale. On the other hand, episodically elevated concentrations of the less brominated PBDEs in the wintertime and lack of seasonality for the non-volatile BDE-209 indicate potential inputs of particle-bound PBDEs through long-range transport (LRT), especially during the Arctic haze season. Inter-annual trend data further show that concentrations of the eight PBDEs increased inter-annually in 2002–2004 with doubling times of 2–6 years, which were similar to growth rates found in Arctic biotic samples. The results of this study and previous measurements suggest that potential sources of PBDEs in Arctic air include both volatilization emissions and LRT inputs.     

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.     

Sorption-desorption behavior of polybrominated diphenyl ethers in soils

Polybrominated diphenyl ethers (PBDEs) are flame retardants that are commonly found in commercial and household products. These compounds are considered persistent organic pollutants. In this study, we used 4,4′-dibromodiphenyl ether (BDE-15) as a model compound to elucidate the sorption and desorption behavior of PBDEs in soils. The organic carbon-normalized sorption coefficient (K_OC) of BDE-15 was more than three times higher for humin than for bulk soils. However, pronounced desorption hysteresis was obtained mainly for bulk soils. For humin, increasing concentration of sorbed BDE-15 resulted in decreased desorption. Our data illustrate that BDE-15 and probably other PBDEs exhibit high sorption affinity to soils. Moreover, sorption is irreversible and thus PBDEs can potentially accumulate in the topsoil layer. We also suggest that although humin is probably a major sorbent for PBDEs in soils, other humic materials are also responsible for their sequestration.     

Absorption, disposition and excretion of polybrominated diphenyl ethers (PBDEs) in chicken

Except for fish, no toxicokinetic data on polybrominated diphenyl ethers (PBDEs) is available on relevant animals for the human food chain. In the present work, absorption, elimination through eggs and disposition of PBDEs in laying chickens were studied and compared to dioxin behaviour. Hens were fed with diet containing 3.4 mg/kg feed of PBDEs and 0.95 ng TEQ/kg feed of polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs). PBDEs have been demonstrated to show drastically different behaviours from PCDD/Fs and dioxin-like compounds. Excretion of PBDEs increased for two weeks and then decreased to nearly 0%. Sixty-two percent of ingested 2,2',4,4'-tetraBDE (BDE-47) were found in excreta after two weeks, suggesting a reductive debromination of PBDEs in the digestive tract. PBDE level in eggs increased during five weeks and reached 24 microg/g fat. After then, levels decreased to 3 microg/g fat at the end of the trial. PBDE bioconcentration factors estimated for abdominal fat varied from 0.7 for BDE-47 to 2 for BDE-183.     

Time-trend (1973-2000) of polybrominated diphenyl ethers in Japanese mother's milk

The time-trend and recent concentrations of polybrominated diphenyl ethers (PBDEs) in Japanese mother's milk were investigated. The time-trend of 16 PBDEs (BDE-28, 37, 47, 66, 71, 75, 77, 85, 99, 100, 119, 153, 154, 138, 183, and 190) in pooled milk samples from mothers living in Osaka between 1973 and 2000 was analyzed. Additionally, PBDE concentrations in individual milk samples collected from 13 mothers living in Kanagawa and Okayama in 1999 were measured. The total concentration of all PBDE congeners (SigmaPBDEs) measured in the pooled samples increased during the period between 1973 (<0.01 ng/g lipid) and 1988 (1.64 ng/g lipid), and remained low afterwards while showing remarkable changes in PBDE congener profiles. The SigmaPBDEs in the 1999 individual milk samples were also low (0.56-3.97 ng/g lipid), except for a single sample (291 ng/g lipid). The source of this exposure could not be identified.     

Atmospheric deposition of polybrominated diphenyl ethers (PBDEs) in coastal areas in Korea

Atmospheric bulk samples were collected monthly, for one year, from urban, suburban, and rural sites located in the coastal areas of Korea, for the assessment of depositional fluxes and seasonal variations in atmospheric concentrations of PBDEs. Twenty individual PBDE congeners were found in atmospheric samples, and their depositional fluxes varied from 10.1 to 89.0 microg/m2/year. The highest depositional fluxes were found in two urbanized areas, with a strong urban-rural gradient. The relationship between PBDE and particulate depositional fluxes showed significant correlation for all locations, which suggested the association of PBDEs to particulate phase. Deca-BDE (BDE 209) was the predominant congener (>93%) in all deposition samples, which is consistent with a high consumption of deca-BDE for the flame-retardant market in Korea. Seasonal variability was observed in PBDE concentrations for the two urban sites, whereas no seasonal trend was found for either the suburban or the rural location.     

Occurrence and congener profiles of polybrominated diphenyl ethers (PBDEs) in environmental samples from coastal British Columbia, Canada

Environmental levels and detailed congener profiles (31 congeners and 3 coeluting congener groups) of polybrominated diphenyl ethers (PBDEs) were assessed in a number of biota samples taken over a large geographic range covering harbours and industrial sites on Canada's West Coast. Additionally, PBDE congener profiles were determined using semipermeable membrane devices (SPMDs) deployed in the Fraser River, the river in Western Canada with the largest industrial activity. PBDE levels detected in biota were between 4 and 2300 ng/g lipid and these levels were compared with those reported in selected European biota to provide a wider perspective on PBDE contamination on Canada's West Coast. Thirteen-congener PBDE patterns in the environmental samples were examined using principal component analysis (PCA), and additionally, comparisons were made between the PBDE profiles in the sample groups and commercially used PBDE technical mixtures (e.g., Bromkals) on a percent composition basis. PCA on congener specific data revealed that PBDE patterns are remarkably similar over a wide geographical range in Western Canada, however, the general pattern in environmental samples varies significantly from those of the predominant technical mixtures. Finally, correlations between PBDE and other persistent and toxic co-occurring contaminants found in Dungeness crab were determined.     

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.     

Levels of polybrominated diphenyl ethers (PBDEs) in breast milk from Beijing, China

The levels of polybrominated diphenyl ethers (PBDEs) in breast milk from Beijing, China, were studied. The 6 predominant PBDEs congeners (BDE47, BDE99, BDE100, BDE153, BDE154 and BDE183) in 23 pooled breast milk samples from 205 mothers living in Beijing were measured. Mean and median of SigmaPBDEs concentrations in all samples were 1.12ngg(-1) lipid and 1.07ngg(-1) lipid, respectively. The Statistical difference in SigmaPBDEs concentrations was found between urban areas (1.22ngg(-1) lipid, n=14) and rural areas (0.97ngg(-1) lipid n=9). The sum of BDE47 and BDE153 accounted for more than 70% of SigmaPBDEs in most samples. The significant correlation was found between the SigmaPBDEs in pooled samples and average of consumption of food of animal origin in the pools in urban area. However, there was no correlation was found between the SigmaPBDEs in pooled samples and average of consumption of food of animal origin in the pools in rural area of Beijing. The current study showed that the level of PBDEs in breast milk from Beijing was lower than that from South China and some developed countries such as USA and Sweden.     

Tree bark as a passive air sampler to indicate atmospheric polybrominated diphenyl ethers (PBDEs) in southeastern China

The different barks were sampled to discuss the influence of the tree species, trunk circumference, and bark thickness on the accumulation processes of polybrominated diphenyl ethers (PBDEs) from air into the bark. The results of different PBDE concentrations indicated that barks with a thickness of 0–3 mm collected from weeping willow, Camphor tree, and Masson pine, the trunk circumferences of which were 100 to 150 cm, were better PBDEs passive samplers. Furthermore, tree bark and the corresponding air samples were collected at Anji (AJ), Hangzhou (HZ), Shanghai (SH), and Wenling (WL) to investigate the relationship between the PBDE concentrations in bark and those in air. In addition, the significant correlation (r ²?=?0.906; P?<?0.05) indicated that atmospheric PBDEs were the principle source for the accumulation of PBDEs in the barks. In this study, the log K _BA (bark–air partition coefficient) of individual PBDE congeners at the four sites were in the range from 5.69 to 6.79. Finally, the total PBDE concentration in WL was 5 to 20 times higher than in the other three cities. The result indicated that crude household workshops contributed a heavy amount of PBDEs pollution to the environment, which had been verified by the spatial distribution of PBDEs levels in barks collected at Wenling (range, 26.53–1317.68 ng/g dw). The good correlation between the PBDE concentrations in the barks and the air samples and the variations of the PBDE concentrations in tree barks collected from different sites reflected that the bark could be used as a passive sampler to indicate the atmospheric PBDEs.     

Congener-specific accumulation and environmental risk assessment of polybrominated diphenyl ethers in diverse Korean sewage sludge types

Industrial, domestic wastewater, and livestock sludge samples were collected from 23 wastewater treatment plants in Korea and analyzed for polybrominated diphenyl ethers (PBDEs). The concentrations of Σ₁₉PBDE ranged from 4.01 to 10,400 ng/g dry weight. The average Σ₁₉PBDE concentrations in industrial, domestic wastewater, and livestock sludge were 1,560?±?3,610, 402?±?148, and 27.6?±?50.4 ng/g dry weight, respectively. The composition of PBDEs differed according to the type of sludge. Among the PBDE congeners, BDE 209 was dominant in all sludge samples. After BDE 209, relatively high levels were found for BDE 28 and 47 from industrial sludge, BDE 47 and 99 from domestic wastewater sludge, and BDE 206, 207, and 208 from livestock sludge. Using hierarchical cluster analysis, sludges were divided into three groups according to PBDE congener composition. A risk assessment of PBDEs in sludge used for soil amendment was carried out. Preliminary results indicated that the potential risk of soil exposed to PBDEs in sludge was relatively low.     

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.     

House dust as a source of human exposure to polybrominated diphenyl ethers in Kuwait

This study reports concentrations of polybrominated diphenyl ethers (PBDEs) in dust samples collected from 17 homes in Kuwait. PBDEs were measured in all homes investigated with mean summation operatorPBDEs concentration ranging from 1 to 393 ng g(-1), with a geometric mean of 76 ng g(-1). The dominant congener in all samples was BDE 209 constituting ca. 85% of the summationPBDEs followed by BDE 99 (5%), BDE 47 (4.5%), and BDE 183 (2%). The congener mixture in dust is dominated by those in deca and penta formulations. Using the measured concentrations and estimates of dust ingestion rates for children and adults, estimated human non-dietary exposure based on mean PBDE levels were 14.8 and 1.5 ng day(-1) for children and adults, respectively. The 10-fold difference in exposure estimates between children and adults in this study supports previous reports that children are at greater risk from pollutants that accumulate indoors. The ubiquitous distribution of these chemicals as noted in this study highlights the fact that we are continuously exposed to low doses of chemicals in the indoor environment.     

Sorption kinetic characteristics of polybrominated diphenyl ethers on natural soils

Sorption kinetic characteristics of BDE-28 and BDE-47 on five natural soils with different organic carbon fractions were investigated, and could be satisfactorily described by a two (fast and slow)-compartment first-order model with the ratio of rate constants ranged from 9 to 94 times. The fast compartment made a dominant contribution (71% ∼ 94%) to the total sorption amount in the whole process, and accounted for over 90% of the increase in the total sorption amount at initial 5 h. The influence of the slow compartment on the increase in the total sorption amount became principal (above 90%) in the subsequent stage approximately from 9 h or 25 h to the apparent equilibrium at 265 h. The results proposed the different sorption behaviors of the mathematically classified compartments for BDE-28 and BDE-47, which may correspond to the different soil components, such as soil organic fractions with amorphous and condensed structures, respectively.