Debromination of polybrominated diphenyl ether congeners BDE 99 and BDE 183 in the intestinal tract of the common carp (Cyprinus carpio)

Polybrominated diphenyl ether (PBDE) congener patterns in biota are often enriched in tetra-, penta-, and hexabrominated diphenyl ethers, which is believed to result from the use of the commercial "pentaBDE" formulation. However, our evidence suggests that debromination of PBDEs occurs within fish tissues leading to appreciable accumulation of less brominated congeners. This suggests that PBDE body burdens can reflect both direct uptake from exposure and debromination of more highly brominated congeners. We conducted two independent dietary exposure studies using the common carp (Cyprinus carpio) to trace the fate of 2,2',4,4',5-pentabromodiphenyl ether (BDE 99) and 2,2',3,4,4',5',6-heptabromodiphenyl ether (BDE 183) in fish tissues. Carp were fed food spiked with individual BDE congeners for 62 d, and depuration was monitored during the following 37 d. Significant debromination was observed, converting BDE 99 to 2,2',4,4'-tetrabromodiphenyl ether (BDE47) and BDE 183 to 2,2',4,4',5,6-hexabromodiphenyl ether (BDE 154) and another as yet unidentified hexa-BDE congener. The BDE 99 concentration rapidly declined from 400 +/- 40 ng/g ww in the food to 53 +/- 12 ng/g ww in the gut content material sampled 2.5 +/- 1 h following feeding. At least 9.5 +/- 0.8% of the BDE 99 mass in the gut was debrominated to BDE 47 and assimilated in carp tissues. In the BDE 183 exposure, approximately 17% of the BDE 183 mass was debrominated and accumulated in carp tissues in the form of two hexa-BDE congeners. In both exposure studies, the concentration of the exposure compound decreased significantly in the gut within 2.5 +/- 1 h following ingestion. This rapid decrease in the concentration of the BDE congeners could not be explained entirely by debromination to quantified products or fecal egestion. Reactions occurring within the gut transform BDE congeners to other products that may accumulate or be excreted. Further studies are needed to identify and determine the effects of these BDE metabolites.     

Identification of hydroxylated polybrominated diphenyl ether metabolites in blood plasma from polybrominated diphenyl ether exposed rats

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 parapositions. 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.     

Reductive debromination of polybrominated diphenyl ethers by zerovalent iron

Polybrominated diphenyl ethers (PBDEs) are a new class of global, persistent, and toxic contaminants, which need proper remediation technologies. PBDE degradation in the environment is not well understood. In this study, degradation of PBDEs with zerovalent iron was investigated with six BDEs, substituted with one to 10 bromines. Within 40 days 92% of BDE congener 209 was transformed into lower bromo congeners. During the initial reaction period of BDE 209 (<5 days), hexa- to heptabromo BDEs were the most abundant products, but tetra- to pentabromo congeners were dominant after 2 weeks. The amount of mono- to tribromo BDEs was steadily increased during the experiments. BDEs 28, 47, 66, and 100 also showed a stepwise accumulation of lower bromo congeners. No oxidation products were detected in all experiments. The results showed that a stepwise debromination from n-bromoto (n-1)-bromodiphenyl ethers was the dominant reaction in all congeners. The reaction rate constants of lower bromo BDEs decreased as the number of bromines decreased. The initial reductive debromination rate constants were positively correlated with the heats of formation of BDEs. The preferential accumulation of specific congeners was observed in the experiment with BDEs 28, 47, 66, and 100, where the most abundant products were BDEs 15, 28, 37, and 47, respectively. Reactions proceeded to form more stable and less brominated products that have lower heats of formation. Almost all the possible isomers from a specific parent BDE were found in all the experiments, which was probably due to the small difference of heat of formation between the products (2-5 kcal/mol). Reactions of all congeners proceeded fast at the initial phase (<5 days) followed by a slow reaction. The rate of reductive debromination of BDE 209 was slower with environmentally relevant sulfide minerals (iron sulfide and sodium sulfide). However, the product congener pattern, produced by sulfide mineral catalysis, was nearly similar with that of zerovalent iron treatment. This may be a possible source of lower brominated BDEs in the environment. Debromination of PBDEs by zerovalent iron has high potential values for remediation of PBDEs in the environment.     

Debromination of the flame retardant decabromodiphenyl ether by juvenile carp (Cyprinus carpio) following dietary exposure

The congener 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE 209) is the primary component in a commonly used flame retardant known as decaBDE. This flame retardant constitutes approximately 80% of the world market demand for polybrominated diphenyl ethers (PBDEs). Because this compound is very hydrophobic (log K(ow) approximately 10), it has been suggested that BDE 209 has very low bioavailability, although debromination to more bioavailable metabolites has also been suggested to occur in fish tissues. In the present study, juvenile carp were exposed to BDE 209 amended food on a daily basis for 60 days, followed by a 40-day depuration period in which the fate of BDE 209 was monitored in whole fish and liver tissues separately. No net accumulation of BDE 209 was observed throughout the experiment despite an exposure concentration of 940 ng/day/fish. However, seven apparent debrominated products of BDE 209 accumulated in whole fish and liver tissues over the exposure period. These debrominated metabolites of BDE 209 were identified as penta- to octaBDEs using both GC/ECNI-MS and GC/HRMS. Using estimation methods for relative retention times of phenyl substitution patterns, we have identified possible structures for the hexa- and heptabromodiphenyl ethers identified in the carp tissues. Although exposure of carp to BDE 209 did not result in the accumulation of BDE 209 in carp tissues, our results indicate evidence of limited BDE 209 bioavailability from food in the form of lower brominated metabolites.     

反应性二苯醚类抗菌整理剂的制备及应用

以2,4,4'-三氯-2'-羟基二苯醚和异氰酸丙基三乙氧基硅烷为原料合成了一种反应性二苯醚类抗菌整理剂,通过红外光谱初步表征了其结构,探讨了其与织物的结合方式.抗菌性能测试结果表明:当抗菌整理剂乳液用量为20%(owf)时,整理织物经50次水洗后对大肠杆菌的抗菌率可达到94.46%,表明具有优良的抗菌效果和耐洗性能.物理机械性能测试结果表明:整理前后织物的白度、透气性、顶破强力等指标变化较小,表明该整理剂适宜于棉织物的耐久抗菌整理.     

Survey of polybrominated diphenyl ether levels in Spanish commercial foodstuffs

Concentrations of 15 BDEs flame retardants have been determined in a large variety of food samples purchased in different markets across Spain. This is the first time that BDEs 184, 191, 196, and 197; impurities from BDEs formulations; and/or degradation products of BDE 209, have been detected in foodstuffs. Values ranged from <0.01 to 2482 pg/g fresh weight. The highest total BDE concentrations were found in fish samples (median of 189, range of 24-880 pg/g f.w.), followed by oils (median of 119, range of 14.8-2958 pg/g f.w.), meats (median of 75.9, range of 6.82-2518 pg/g f.w.), shellfish (median of 75.7, range of 3.29-677 pg/g f.w.), eggs (median of 73.5, range of 12.8-557 pg/g f.w.), and dairy products (median of 66.1, range of 3.24-1588 pg/g f.w.). The total BDE values found in this study are consistent with research reported elsewhere. They are in the same range as those recently reported by other European and Asian studies and lower than those conducted in the U.S. BDE 47 was the predominant congener in fish, shellfish, dairy products (except butter), and meats, while BDE 209 was the predominant in oil and egg samples. The most remarkable findings in this study were the large contribution of the highest brominated BDEs (hepta- to deca-BDE), and principally BDE 209, to the total BDE concentration found in Spanish foods, except fish and shellfish, and the presence of BDE 184, 191, 196, and 197 in many of the samples. The calculated intake of 38.5 ng/day of BDEs was comparable to intake assessment from other UE countries.     

气相色谱测定小麦和稻米中11种多溴联苯醚

目的 建立气相色谱-电子捕获检测器法测定小麦和稻米中11种代表性多溴联苯醚的分析方法。方法 小麦粉或糙米粉经水化后,采用乙酸乙酯提取和5 g酸性硅胶(44%, m:m)固相净化柱净化,使用气相色谱-电子捕获检测器进行检测,外标法定量。结果 小麦和稻米中,11种多溴联苯醚的定量线性范围分别为0.1~50.0 ng/g,0.2~50 ng/g,0.5~50 ng/g,回归系数均大于0.998;方法检出限在0.03~0.15 ng/g之间,定量限为0.1~0.5 ng/g之间;方法回收率为66.9%~93.5%,相对标准偏差为0.4%~17.8%。结论 本方法的样品前处理简单,对仪器要求低,准确度和精密度较好,适用于小麦和稻米中多溴联苯醚的检测分析。     

Polybrominated diphenyl ether flame retardants in foodstuffs and human milk

Polybrominated diphenyl ethers (PBDEs) have been used worldwide as additive flame retardants in polymeric materials. Commercial products consist predominantly of deca-, octa-, and pentabromodiphenyl ether mixtures. PBDEs are resistant to degradation in the natural environment and Penta-BDE in particular accumulates in the fatty tissues of fish, birds and mammals (including humans). Several toxic effects on the thyroid system or on neurodevelopment have been reported in experimental animals exposed to PBDEs. It is likely that human exposure is predominantly through the ingestion of contaminated food and/or mother's milk. The potential health effects of dietary exposure to PBDEs have now become a great concern because of the increasing PBDE levels in the biosphere. In this review, published information on the toxicology of PBDEs, levels in foodstuffs and human milk, and analytical methods has been compiled.     

Photochemical decomposition of 15 polybrominated diphenyl ether congeners in methanol/water

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 (T1/2 = 0.5 h) was more than 500 times shorter than the environmentally abundant congener 2,2',4,4'-tetraBDE (T1/2 = 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.     

Development of a cleanup method for polybrominated diphenyl ether (PBDE) in fish by freezing-lipid filtration

A new cleanup method for the determination of brominated flame retardants with an emphasis on polybrominated diphenyl ethers (PBDEs) has been developed for fish tissue sample. This method effectively reduces the sample pretreatment time, labor and required less solvent quantities relative to conventional methods. Freezing-lipid filtration procedure removes approximately 90 % of the lipids in the extract without any significant loss of the PBDEs. A multilayered silica gel column was used for further cleanup of the extracts after freezing-lipid filtration. Multilayered silica gel column chromatography eliminated most of the co-extracted interferences, such as residual lipids and fatty acids. The extracts were analyzed after cleanup by high-resolution gas chromatography/high-resolution mass spectrometry using the isotope dilution method. Tissue samples with 1.6–8.0 and 8.0–40 ppb of PBDE were analyzed using both the sulfuric acid treatment and freezing-lipid filtration cleanup methods in order to evaluate the method performance. Sulfuric acid treatment did not detect 2,4-DiBDE, whereas freezing-lipid filtration detected 2,4-DiBDE but at 50 % recovery. To compare the method, WMF-01 was analyzed via both the sulfuric acid treatment and freezing-lipid filtration cleanup.     

索氏提取-气相色谱/质谱法测定食品包装材料中羟基苯醚

目的 建立一种适用于食品包装材料中羟基苯醚的气相色谱/质谱检测方法。方法 采用索氏提取法, 以二丙醚萃取提取样品中二苯醚类物质, 经色谱分离后采用质谱检测器, 保留时间、分子碎片峰定性, 外标法定量。结果 对于二苯醚类物质检测回收率范围88%~109%, 相对标准偏差<3.9, 检测限0.032 ~0.067mg/L。结论 本方法便捷、重现性好, 适用于各种类型食品包装材料中二苯醚类物质检测。     

Levels of polybrominated diphenyl ether flame retardants in sediment cores from Western Europe

The levels of 14 brominated diphenyl ether (BDE)-congeners in sediment cores from three locations in Western Europe have been determined by GC/MS (negative chemical ionization mode). Sediments from the Drammenfjord (Norway), the western Wadden Sea (The Netherlands), and the freshwater Lake Woserin (Mecklenburg-Vorpommern, Germany) showed a time-dependent pattern in the distribution of BDEs since the beginning of the industrial production of polybrominated diphenyl ether (PBDE) formulations. Two out of three commercially available PBDE formulations could be distinguished. Starting from the beginning of the 1970s, the penta-mix formulation is clearly present, but the deca-mix formulation is only present since the late 1970s. The octa-mix formulation appeared to be still absent in these sediments, as its marker-congener, BDE183, was never detected. In the cores from the western Wadden Sea and Lake Woserin, all TOC-normalized concentrations of the penta-BDE-derived congeners were leveling off in the most recent sediment layers representing 1995 and 1997, whereas those in the Drammenfjord were still increasing in 1999. The levels of BDE209, however, decreased in the most recent layer of all three cores. In Lake Woserin, the concentrations of BDE209 were much less elevated above those of the tri- to hexa-BDEs than in the other the two areas. This might be due to the absence of a significant PBDE input from sources other than the atmosphere to this rural lake. The absence of all PBDE congeners in the older layers of the three sediment cores, as well as in several 100-150-My-old layers from an extremely organic-rich marine sediment from the Kimmeridge clay formation in Dorset (UK), indicated the absence of natural production of the BDE congeners analyzed.     

Rapid and extensive debromination of decabromodiphenyl ether by smectite clay-templated subnanoscale zero-valent iron

Subnanoscale zerovalent iron (ZVI) synthesized using smectite clay as a template was utilized to investigate reduction of decabromodiphenyl ether (DBDE). The results revealed that DBDE was rapidly debrominated by the prepared smectite-templated ZVI with a reaction rate 10 times greater than that by conventionally prepared nanoscale ZVI. This enhanced reduction is plausibly attributed to the smaller-sized smectite-templated ZVI clusters (～0.5 nm) vs that of the conventional nanoscale ZVI (～40 nm). The degradation of DBDE occurred in a stepwise debromination manner. Pentabromodiphenyl ethers were the terminal products in an alkaline suspension (pH 9.6) of smectite-templated ZVI, whereas di-, tri-, and tetrabromodiphenyl ethers formed at the neutral pH. The presence of tetrahydrofuran (THF) as a cosolvent at large volume fractions (e.g., >70%) in water reduced the debromination rates due to enhanced aggregation of clay particles and/or diminished adsorption of DBDE to smectite surfaces. Modification of clay surfaces with tetramethylammonium (TMA) attenuated the colsovent effect on the aggregation of clay particles, resulting in enhanced debromination rates. Smectite clay provides an ideal template to form subnanoscale ZVI, which demonstrated superior debromination reactivity with DBDE compared with other known forms of ZVIs. The ability to modify the nature of smectite clay surface by cation exchange reaction utilizing organic cations can be harnessed to create surface properties compatible with various contaminated sites.     

Quantitative structure-activity relationship models for prediction of the toxicity of polybrominated diphenyl ether congeners

Levels of polybrominated diphenyl ethers (PBDEs) are increasing in the environment and may cause long-term health problems in humans. The similarity in the chemical structures of PBDEs and other halogenated aromatic pollutants hints on the possibility that they might share similar toxicological effects. In this work, three-dimensional quantitative structure activity relationships (3-D-QSAR) models, using comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA), were built based on calculated structural indices and a reported experimental toxicology index (aryl hydrocarbon receptor relative binding affinities, RBA) of 18 PBDEs congeners, to determine the factors required for the RBA of these PBDEs. After performing leave-one-out cross-validation, satisfactory results were obtained with cross-validation O2 and R2 values of 0.580 and 0.995 by the CoMFA model and 0.680 and 0.982 by the CoMSIA model, respectively. The results showed clearly that the nonplanar conformations of PBDEs result in the lowest energy level and that the electrostatic index was the main factor reflecting the RBA of PBDEs. The two QSAR models were then used to predict the RBA value of 46 PBDEs for which experimental values are unavailable at present.     

European-scale modeling of concentrations and distribution of polybrominated diphenyl ethers in the pentabromodiphenyl ether product

The results from a modeling exercise utilizing the European variant (EVn) BETR multimedia environmental fate model are presented for selected polybrominated diphenyl ethers (PBDEs) of the technical penta- (Pe-) bromodiphenyl ether (BDE) product. The objectives of this study were to test PeBDE emission estimates from the literature for Europe by investigating the consistency between model predictions and ambient measurements to address the ability of the model to predict spatial variability and differences between congeners. Concurrently sampled and analyzed passive sampling air data, together with soil and grass data, were used as key model validation tools. The model steady-state simulations gave generally good agreement with measured data for BDE-47 and -99 with greater discrepancies for heavier congeners (e.g., BDE-153). To predict future atmospheric concentration trends, the model was used in its fully dynamic mode over the period 1970--2010. It was predicted that atmospheric concentrations peaked around 1997, declining with an overall "disappearance" half-life of 4.8 years. Soil and grass levels were underestimated by the model; possible reasons for differences with measurement data are further explored. Finally, the importance of temporally and spatially resolved environmental data sets is highlighted, while improved quantification of degradation half-lives is essential to better understand and predict the behavior of BDE congeners in PeBDE.     

Dehalogenation of polybrominated diphenyl ethers and polychlorinated biphenyl by bimetallic, impregnated, and nanoscale zerovalent iron

Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zerovalent, which shows the difficulty with in-situ synthesis of a significant fraction of zerovalent iron in the microporous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogeneous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI.     

Inactivation of MS2 coliphage by ferrous ion and zero-valent iron nanoparticles

This study demonstrates the inactivation of MS2 coliphage (MS2) by nano particulate zerovalent iron (nZVI) and ferrous ion (Fe[II]) in aqueous solution. For nZVI, the inactivation efficiency of MS2 under air-saturated conditions was greater than that observed under deaerated conditions, indicating that reactions associated with the oxidation of nZVI were mainly responsible for the MS2 inactivation. Under air-saturated conditions, the inactivation efficiency increased with decreasing pH for both nZVI and Fe(II), associated with the pH-dependent stability of Fe(II). Although the Fe(II) released from nZVI appeared to contribute significantly to the virucidal activity of nZVI, several findings suggest that the nZVI surfaces interacted directly with the MS2 phages, leading to their inactivation. First, the addition of 1,10-phenanthroline (a strong Fe(II)-chelating agent) failed to completely block the inactivation of MS2 by nZVI. Second, under deaerated conditions, a linear dose-log inactivation curve was still observed for nZVI. Finally, ELISA analysis indicated that nZVI caused more capsid damage than Fe(II).