Deca-BDE

Based on the values of Cpcdd/fs [46], Ccipahs [38], and CBfrs in e-waste, the annual mass emissions of selected PCDD/F and C1PAH congeners and BFRs from e-waste are estimated (Table 3). The lowest annual mass emission of PBDEs is about 82,207 tons/year, with 70,607 tons/year from importation and 11,600 tons/ year from domestic generation (Table 3). Nona- and deca-BDEs are the most important congeners as they are the major constituents of BRFs in electronic equipment [77]. In addition, the annual mass emissions of PBBs, TBBPA, and PBPs are also estimated with the same procedure (Table 3). Obviously, importation is responsible for the majority of annual mass emissions of e-waste-derived organic pollutants in China (Table 3). 

Table 6 Annual generation of e-waste and contaminants based on following data annual amount of e-waste taken from Brigden et al. [2], concentrations of TBBPA and Octa/Deca-BDEs based on Morf et al. [11], concentrations of lead, plastics, metals, and CRT-glass taken from Ewasteguide.info [12]... 

Due to the toxicological effect of PBDEs, the production and use of penta-, octa-, and deca-BDE mixtures have been banned in Europe. Moreover, and in response to increasing international regulations on BFR formulations, alternative FRs for achieving commercial product fire safety standards are being developed and used. Some of these non-BDE BFRs are pentabromoethylbenzene (PBEB), hexabromobenzene (HBB), and decabromodiphenylethane (DBDPE) [28],... 

The first European results from 1988 reveal levels of about 20-30 ng/g dw of PBDEs in sewage sludges collected in Sweden [65], being deca-BDE-209 the... 

There is a huge variety of PBDEs considering that there might be from one to ten bromine atoms bound to the diphenyl ether molecule. Among all the PBDEs, the commercial mixtures of decabromodiphenyl ether (deca-BDE), octabromodiphenyl ether (octa-BDE) and pentabromodiphenyl ether (penta-BDE) are the products that are most found in the environment. Related to octa-BDE and penta-BDE mixtures, their commercial use was banned in the European Union in 2004 and that year their leading manufacturers in North America stopped producing them on a voluntary basis [2], Regarding the deca-BDE mixture, since July 2008, its use has been... 

Fig. 1 PBDE structures examples (a) deca-BDE-209 (b) hepta-BDE-183 (c) penta-BDE-99...

The mixture of deca-BDE is composed almost exclusively of deca-BDE (BDE-209), with a rate of 97% or more and by 3% or less of nonabromodiphenyl ethers (nona-BDEs) and octa-BDEs. On the contrary, the commercial octa-BDE mixture usually contains between 10% and 12% hexabromodiphenyl ethers (hexa-BDEs), 44% of heptabromodiphenyl ethers (hepta-BDEs), between 31% and 35% of octa-BDEs, between 10% and 11% of nona-BDEs and <1% of deca-BDE [4]. The two compounds with a higher proportion in this mixture are, in first place, BDE-183 (2,2, 3,4,4, 5, 6-hepta-BDE) and then the BDE-153 (2,2, 4,4, 5,5 -hexa-BDE). In addition, the penta-BDE mixture, commercially known as DE-71, is primarily composed by tetrabromodiphenyl ethers (tetra-BDEs) (24—38%), penta-BDEs (50-60%) and hexa-BDEs (4-8%) being BDE-99 (2,2, 4,4, 5-penta-BDE) and BDE-47 (2,2, 4,4 -tetra-BDE) the main compounds of the mixture. Figure 1 shows different structures belonging to the three PBDE mixtures described. 

PBDE compounds are highly insoluble in aqueous phase in all cases and very stable. Its insolubility increases as the higher the number of substituents in the molecule, ranging from a solubility of approximately 100 pg L-1 for monobromo-diphenyl ethers (mono-BDEs) to a value of 25 5 ng L-1 for deca-BDE [5]. 

In the case of deca-BDE, its suggested degradation process in mammals consists of a first reductive debromination where one, two or three bromine atoms can be replaced by hydrogen atoms followed by an oxidation to form hydroxylated metabolites, which are presumably formed from an intermediate epoxy [52]. This study detected traces of three nona-BDEs, which may be an indication of reductive debromination as a first step of degradation, and thirteen hydroxylated metabolites. Otherwise, the possibility of a deca-BDE oxidation as a first step to form the epoxy without an intermediate reductive debromination is also suggested [52]. The study conducted by Morck et al. [53] detected several hydroxylated products, from methoxy-hydroxy-pentabrominated to methoxy-hydroxy-heptabrominated compounds, which coincide with part of the metabolites obtained by Sandholm et al. [52]. In addition, both authors found that methoxy and hydroxy substituents are always on the same aromatic ring when both are present. Moreover,... 

Fig. 4 Proposed deca-BDE degradation pathway on mammals. Adapted from Morck et al. [53] and Sandholm et al. [52]...

Morck et al. [53] found traces of less brominated PBDEs than deca-BDE, indicating that the reductive debromination would be the first step in its degradation. In both articles, it is suggested the involvement of Cyp P450 in the oxidation reactions to form hydroxylated metabolites, but not in the reductive debromination proposed as the initial step. 

Regarding the reductive debromination as the first step of deca-BDE degradation in mammals, Huwe and Smith [54] detected the formation of different PBDEs (three nona-BDEs, four octa-BDEs and one hepta-BDE) from deca-BDE degradation in rats, which also suggests the existence of a reductive debromination process as the first step in deca-BDE degradation in mammals. In this case, it was not identified whether the specific enzymatic system responsible for the reductive debromination and the corresponding analyses to detect the formation of hydroxylated metabolites were not carried out. 

Figure 4 shows the proposed deca-BDE degradation pathway in mammals according to the research studies in rats. 

Deca-BDE Degradation in Aqueous Phase by T. versicolor 2.1 Degradation Capacity... 

First, the capacity of the fungus T. versicolor to degrade deca-BDE was evaluated. To carry out the treatment, the fungus was used in the form of pellets 100 mL amber serum bottles were filled with 10 mL of defined medium (DM) with Tween 80 (500 mg L x) as surfactant to increase the solubility of the contaminant and deca-BDE at a concentration of 10 mg L 1. The bottles were inoculated with the necessary amount of pellets to reach an approximate biomass concentration of 3.5 g L-1 (dry weight). 

Fig. 5 Evolution of glucose concentration and deca-BDE degradation yield in aqueous phase by T. versicolor pellets. Deca-BDE initial concentration = 10 mg L-1...

As mentioned previously, deca-BDE was considered for a long time as a practically non-toxic compound, due to its low availability. However, the results of both experiments have clearly demonstrated that this pollutant is bioavailable in aqueous phase in the presence of Tween 80. Considering that wastewater discharged into the environment often contains different types of surfactants,... 

Fig. 7 Deca-BDE amount in the abiotic and adsorption control for an initial concentration of 2 mg L-1 (left) and 10 mg L-1 (right)...

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