Levels and trends of PBDEs and HBCDs in the global environment : status at the end of 2012

In this paper, we have compiled and reviewed the most recent literature, published from January2010 to December 2012, relating to the human exposure, environmental distribution, behaviour, fate and concentration time trends of polybrominated diphenyl ether (PBDE) and hexabromocyclododecane (HBCD) flame retardants, in order to establish their current trends and priorities for future study. Due to the large volume of literature included, we have provided full detail of the reviewed studies as Electronic Supplementary Information and here summarise the most relevant findings. Decreasing time trends for penta-mix PBDE congeners were seen for soils in northern Europe, sewage sludge in Sweden and the USA, carp from a US river, trout from three of the Great Lakes and in Arctic and UK marine mammals and many birds, but increasing time trends continue in Arctic polar bears and some birds at high trophic levels in northern Europe. This is a result of the time delay inherent in long-range atmospheric transport processes. In general, concentrations of BDE209 (the major component of the deca-mix PBDE product) are continuing to increase. Of major concern is the possible/likely debromination of the large reservoir of BDE209 in soils and sediments worldwide, to yield lower brominated congeners which are both more mobile and more toxic, and we have compiled the most recent evidence for the occurrence of this degradation process. Numerous studies reported here reinforce the importance o f this future concern. Time trends for HBCDs are mixed, with both increases and decreases evident in different matrices and locations and, notably, with increasing occurrence in birds of prey.

Self-assembly of a halogenated molecule on oxide-passivated Cu(110)

The supramolecular self-assembly of brominated molecules was investigated and compared on Cu(110) and Cu(110)[BOND]O(2×1) surfaces under ultrahigh vacuum. By using scanning tunnelling microscopy, we show that brominated molecules form a disordered structure on Cu(110), whereas a well-ordered supramolecular network is observed on the Cu(110)[BOND]O(2×1) surface. The different adsorption behaviors of these two surfaces are described in terms of weakened molecule–substrate interactions on Cu(110)[BOND]O(2×1) as opposed to bare Cu(110). The effect of oxygen-passivation is to suppress debromination and it can be a convenient approach for investigating other self-assembly processes on copper-based substrates.

Selenium-Mediated Dehalogenation of Halogenated Nucleosides and its Relevance to the DNA Repair Pathway

Halogenated nucleosides can be incorporated into the newly synthesized DNA of replicating cells and therefore are commonly used in the detection of proliferating cells in living tissues. Dehalogenation of these modified nucleosides is one of the key pathways involved in DNA repair mediated by the uracil-DNA glycosylase. Herein, we report the first example of a selenium-mediated dehalogenation of halogenated nucleosides. We also show that the mechanism for the debromination is remarkably different from that of deiodination and that the presence of a ribose or deoxyribose moiety in the nucleosides facilitates the deiodination. The results described herein should help in understanding the metabolism of halogenated nucleosides in DNA and RNA.

Biotransformation of alpha-Bromoacetophenones by the Marine Fungus Aspergillus sydowii

The biotransformation reactions of alpha-bromoacetophenone (1), p-bromo-alpha-bromoacetophenone (2), and p-nitro-alpha-bromoacetophenone (3) by whole cells of the marine fungus Aspergillus sydowii Ce19 have been investigated. Fungal cells that had been grown in artificial sea water medium containing a high concentration of chloride ions (1.20 M) catalysed the biotransformation of 1 to 2-bromo-1-phenylethanol 4 (56%), together with the alpha-chlorohydrin 7 (9%), 1-phenylethan-1,2-diol 9 (26%), acetophenone 10 (4%) and phenylethanol 11 (5%) identified by GC-MS analysis. In addition, it was observed that the enzymatic reaction was accompanied by the spontaneous debromination of 1 to yield alpha-chloroacetophenone 5 (9%) and alpha-hydroxyacetophenone 6 (18%) identified by GC-FID analysis. When 2 and 3 were employed as substrates, various biotransformation products were detected but the formation of halohydrins was not observed. It is concluded that marine fungus A. sydowii Ce19 presents potential for the biotransformations of bromoacetophenone derivatives.

(Tables 1,2) Polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas) and ringed seal (Pusa hispida) liver microsomal protein content and EROD activity

The present study assessed and compared the oxidative and reductive biotransformation of brominated flame retardants, including established polybrominated diphenyl ethers (PBDEs) and emerging decabromodiphenyl ethane (DBDPE) using an in vitro system based on liver microsomes from various arctic marine-feeding mammals: polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas), and ringed seal (Pusa hispida), and in laboratory rat as a mammalian model species. Greater depletion of fully brominated BDE209 (14-25% of 30pmol) and DBDPE (44-74% of 90pmol) occurred in individuals from all species relative to depletion of lower brominated PBDEs (BDEs 99,100, and 154; 0-3% of 30pmol). No evidence of simply debrominated metabolites was observed. Investigation of phenolic metabolites in rat and polar bear revealed formation of two phenolic, likely multiply debrominated, DBDPE metabolites in polar bear and one phenolic BDE154 metabolite in polar bear and rat microsomes. For BDE209 and DBDPE, observed metabolite concentrations were low to nondetectable, despite substantial parent depletion. These findings suggested possible underestimation of the ecosystem burden of total-BDE209, as well as its transformation products, and a need for research to identify and characterize the persistence and toxicity of major BDE209 metabolites. Similar cause for concern may exist regarding DBDPE, given similarities of physicochemical and environmental behavior to BDE209, current evidence of biotransformation, and increasing use of DBDPE as a replacement for BDE209.

Thermogravimetric Study of the Decomposition of Printed Circuit Boards from Mobile Phones

Paper submitted to the 19th International Symposium on Analytical & Applied Pyrolysis, Linz, Austria, 21-25 May 2012.

Tetra- and tribromopbenoxyanisoles in Marine Samples from Oceania

Some methoxylated polybrominated diphenyl ethers (MeO-BDEs) are known halogenated natural products (HNPs) and are frequently detected in higher organisms of the marine environment. In this study we demonstrate that a prominent MeO-BDE, previously detected in marine mammals from Australia, is identical to 3,5-dibromo-2-(2',4'-dibromo)phenoxyanisole(BC-3,6-MeO-BDE47). Up to 1.9mg/ kg of 6-MeO-BDE 47 was present in cetaceans from Australia, 0.2-0.3 mg/kg in two crocodile eggs from Australia, but concentrations of 1 or 2 orders of magnitude lower were found in shark liver oil from New Zealand and in marine mammals from Africa and the Antarctic. Concentrations of 6-MeO-BDE47 in samples from Australia were in the same range as anthropogenic pollutants such as PCB 153 and p,p'-DDE. Along with 6-MeO-BDE 47 and the known HNP 4,6-dibromo-2-(2',4'-dibromo)phenoxyanisole (BC-2,2'-MeO-BDE 68), several tribromophenoxyanisoles (MeO-triBDE) were present in tissue of Australian cetaceans. To determine their structure, abiotic debromination experiments were performed using 6-MeO-BDE 47 and 2'-MeO-BDE 68 and superreduced di cyanocobalamine. These experiments resulted in formation of eight MeO-triBDEs, all of which were detected in the cetacean samples. Five of these eight MeO-triBDEs could be identified based on two standard compounds as well as gas chromatographic and mass spectrometric features. It was also shown that the first eluting isomer (compound 1), 6-MeO-BDE 17 (compound 2), and 2-MeO-BDE 39 (compound 5) were the most prominent MeO-triBDEs in the Australian cetacean samples. The concentrations of the MeO-triBDEs in two cetacean samples were 0.20 and 0.36 mg/kg, respectively. Although the reductive debromination with dicyanocobalamine resulted in a different congener pattern than was found in the marine mammals, it could not be excluded that the tribromo congeners of 6-MeO-BDE 47 and 2'-MeO-BDE 68 in the samples were metabolites of the latter.

Polypropylene as a reductive agent for dehalogenation of brominated organic compounds

A new method for debromination of organics by a reductive medium like polypropylene is investigated. The reaction is carried out in inert atmosphere to avoid rapid oxidation of the polymer. Through this detoxification procedure, hydrogen bromide and small brominated alkanes are formed. Experiments in closed ampoules are carried out with tetrabromobisphenol A, dibromophenol, pentabromodiphenyl ether, dichlorophenol and an oil formed by pyrolysis of printed circuit boards in the Haloclean® process. The reaction is examined under isothermal conditions in a temperature range between 300 and 400°C and a residence time between 10 and 30 min. Optimal conditions were found at 350°C and at a residence time of 20 min. As chlorinated phenols are not destroyed under these conditions, the process may be a valuable procedure to gain hydrogen bromide out of mixtures of halogenated feed materials. Also, under atmospheric pressure, a reaction between polypropylene and brominated compounds takes place as could be proved by thermogravimetric analysis. Bromobenzene has an accelerating effect on the rate of weight loss of the polymer, but at higher concentrations, it can also be slowed down. © 2003 Elsevier Ltd. All rights reserved.

Hydrodebromination of bromobenzene over Pt(111)

The surface chemistry of benzene and bromobenzene over Pt(111) has been studied by temperature-programmed XPS/MS and NEXAFS. Time-resolved XPS shows that benzene adopts a single chemically distinguishable environment during low-temperature adsorption within the monolayer, with a saturation coverage at θC6H6 = 0.2 ML. Around 20% of a benzene monolayer desorbs molecularly, while the remainder dehydrogenates to surface carbon. Bromobenzene likewise adsorbs molecularly at 90 K, giving rise to two C 1s environments at 284.4 and 285.3 eV corresponding to the C−H and C−Br functions, respectively. The saturation C6H5Br monolayer coverage is 0.11 ML. NEXAFS reveals that bromobenzene adopts a tilted geometry, with the ring plane at 60 ± 5° to the surface. Bromobenzene multilayers desorb at ∼180 K, with higher temperatures promoting competitive molecular desorption versus C−Br scission within the monolayer. Approximately 30% of a saturated bromobenzene monolayer either desorbs reversibly or as reactively formed hydrocarbons. Debromination yields a stable (phenyl) surface intermediate and atomic bromine at 300 K. Further heating results in desorption of reactively formed H2, C6H6, and HBr; however, there was no evidence for either biphenyl or Br2 formation. Pt(111) is an efficient surface for low-temperature bromobenzene hydrodebromination to benzene and HBr. © 2007 American Chemical Society.

Detoxification of brominated pyrolysis oils

The development of an innovative technology for the pyrolytic conversion of brominated phenols in a reductive medium aimed at product recovery for commercial use is discussed in this paper. Brominated phenols are toxic products, which contaminate pyrolysis oil of wastes from electronic and electrical equipment (WEEE). The pyrolysis experiments were carried out with 2,6-dibromophenol, tetrabromobisphenol A, WEEE pyrolysis oil and polypropylene or polyethylene in encapsulated ampoules under inert atmosphere in quasi-isothermal conditions (300-400 °C) with a different residence time (10-30 min). Optimal conditions were found to be the use of polypropylene at 350 °C with a residence time of 20 min. The main pyrolysis products were identified as HBr and phenol. A radical debromination mechanism for the pyrolytic destruction of brominated phenols is suggested. © 2003 Elsevier Science B.V. All rights reserved.