Octa-BDEs

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... 

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. 

Penta-BDE and octa-BDE mixtures degradation studies in solid media in anaerobic conditions are very scarce. In the case of penta-BDE mixture, Vonderheide et al. [2] inoculated a culture with different anaerobic microorganisms in a contaminated soil by this mixture. After a short time, the major compound in the mixture, BDE-99, was almost completely degraded, as well as other PBDEs present in lower proportion (hexa-BDEs and penta-BDEs). Moreover, for the same time, it was observed an increase of the amount of BDE-47, which corresponds to the second major compound in the mixture. The authors argue that BDE-47 amount increase could be caused by the fact that it is a degradation product of other higher brominated PBDEs such as BDE-99. In fact, it was demonstrated later that BDE-47 is formed from BDE-99 degradation in anaerobic conditions [37]. 

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. 

Apart from deca-BDE mixture, the two PBDE mixtures most frequently used in the past were the penta-BDE and octa-BDE mixtures. Although its use was banned in the European Union from 2004 and their production was ceased in the United States... 

Table 4 Characterization of octa-BDE and penta-BDE mixtures compounds...

Before degradation experiments were performed, a characterization of the composition of both mixtures, which is summarized in Table 4, was carried out. Note that in the case of penta-BDE mixture, due to the lack of analytical standards, it was only possible to quantify 6 of the 27 compounds present in the mixture. These compounds correspond to BDE-47, BDE-100, BDE-99, BDE-154, BDE-153 and BDE-183. These compounds are the major components of penta-BDE mixture, representing the 92.5% of the total composition, and they are usually detected in the environment. Respect octa-BDE mixture, two compounds were detected, BDE-153 and BDE-183, which correspond to the major components of the mixture according to the reviewed literature [4], and probably the other compounds present in the mixture were not detected due to the lack of the corresponding analytical standards. 

Comparing the adsorption results obtained from octa-BDE mixture components with deca-BDE results (Fig. 8), it is obtained a higher adsorption for the less brominated compounds. This is due to its greater solubility in aqueous phase, and hence it has higher bioavailability to interact with biomass. 

Table 5 Degradation and removal percentages by T. versicolor for the detected components of octa-BDE and penta-BDE commercial mixtures...

In the case of deca-BDE mixture, the formation of less brominated compounds was not detected for any of the samples (time of degradation corresponding to 24, 36, 60, 84 and 182 h). Regarding octa-BDE and penta-BDE mixtures, the analysis of samples at time 168 h did not detect an increase in concentration for any of the components present in each of the mixtures or the formation of any PBDE not present in the original composition of both mixtures. Therefore, the results obtained for the three mixtures demonstrated that the PBDEs degradation by the fungus does not follow the reductive debromination pathway, which is logical because this... 

The two OH-PBDEs detected indicate that the degradation pathway of octa-BDE and penta-BDE mixtures by the fungus corresponds, in both cases, to a hydroxyl-ation of the PBDE compounds. In the case of deca-BDE mixture, it was not possible to detect any hydroxylated product, but it cannot be excluded the formation of OH-PBDEs and their subsequent degradation for a time lower than 24 h. Therefore, it is possible that deca-BDE degradation by the fungus also occurs through the progressive hydroxylation of the compound, but it would be necessary to have results from treatment times of 12 h to confirm this possibility. 

This article reports on two related pieces of news firstly that Albemarle Corp. of the USA has introduced a new reactive flame retardant, Saytex RX 8500 , as a replacement for pentabromodiphenyl ether (penta-BDE) in the production of flame-retardant PU foam. Secondly that Great Lakes Chemical Corp., the only manufacturer of penta-BDE, has announced plans to voluntarily phase out and cease production of this, and also octa-BDE, at the end of 2004. 

The replacement of established chemistries with newer ones is one of the classic drivers of change in the chemical industry. One of the current hotbeds of this kind of change is the replacement of brominated flame retardants in polymer formulations. The brominated flame retardants under the most scrutiny have been polybrominated diphenyl ethers, particularly penta- and octabromodiphenyl ether, which have been shown to be persistent in the environment and to bioaccumulate. Great Lakes Chemical is voluntarily phasing out penta- and octa-BDEs by the end of next year. The phaseout is made possible by the clean bill of health granted by EPA for Firemaster 550, a replacement for penta-BDE in flexible PU applications. BRG Townsend claims the phaseout of penta-BDE and octa-BDE is not as earth shattering as would be an exit from deca-BDE, a styrenics additive that is produced in the highest volume of the PBDEs. 

The European Union has unanimously voted to reverse a proposal from the European Parliament to phase out two brominated flame retardants, penta- and octa-BDE. This formed part of a forthcoming directive on a third member of the PBDE family. The proposed directive now returns to the Parliament for a second reading in early 2002, by which time risk assessments should be completed. Parliament also agreed that deca-BDE should be banned by 2006, though only if the risk assessment validated this. EUROPEAN COMMISSION... 

In an unprecedented step, the European Parliament has voted to ban two chemicals for which risk assessments are still pending. The chemicals, octabromodiphenylether and decabromodiphenyl ether, were lumped together with penta-BDE during a debate on the EC s proposed ban on that chemical, which is based on a completed risk assessment. All three chemicals are used as flame retardants. Parliamentarians backed the call to extend a ban on penta-BDE to octa-BDE, which is used in office equipment and domestic electrical appliances, by mid-2003. It is claimed that initial results of the ongoing risk assessments already indicate that the chemical is an environmental and public health hazard. MEPs have set a 2006 deadline for banning deca-BDE, adding that the ban should not come into force if the final results of the risk assessment show that deca-BDE is harmless. EUROPEAN PARLIAMENT... 

It is briefly reported that the European Parliament s environment committee has proposed a ban on the use of brominated flame retardants octabromodiphenylether and decabromodiphenylether, used in plastics and textiles, on health and environmental grounds. The two substances are scheduled to be banned from use in electronic and electrical equipment under separate EC draft legislation. The committee s decision has been announced before risk assessments of octa-BDE and deca-BDE for the commission have been completed. 

Lakes see below. Differences in the production and use of the penta-BDE product versus the octa-BDE product may account for these differences. Table 5 lists the demand for the three major PBDE commercial products in the global and North American markets. In 1990, the ratio of the penta-BDE product to the octa-BDE product demand was 0.7, but this ratio increased to 2 in 1999 and 2001. In other words, more of the octa-BDE product, which is relatively high in BDE-153 and -154, was used in the 1980s relative to the penta-BDE product, which is high in BDE-47, but now the opposite is true. This shift toward more of the penta-BDE product in the marketplace is mirrored by an increase in the ratios (R—see Eq. 1) over the same time period. The increase in R over the last 10 years has been about 50%, but the increase in the penta to octa ratio has been about 200%. This difference may be explained by the higher bio-availability of the less-brominated congeners compared with to the more-brominated ones. 

The highest atmospheric TBE concentrations were detected in samples from a site in southern Arkansas. It is interesting to note that the only producer of TBE in the United States, Great Lakes Chemical, produces this compound at a facility located in El Dorado, Arkansas, which is 150 km west of this Arkansas sampling site. It is likely that the production of TBE will increase at this site given that Great Lakes Chemical has announced that they will market TBE (trade named FF-680) as an additive flame retardant to replace the discontinued octa-BDE product [60]. 

According to EPA Inventory Update Rule 2002, Great Lakes Chemical produced 4500-22 500 metric tons each year of TBE from 1986-1994, but the production decreased to 450-4500 metric tons per year after 1998 [60]. This diminution in production may be the cause of the relatively constant concentrations in the sediment core in sections dating after 1985. However, since Great Lakes Chemical plans to replace the octa-BDE product with TBE, there may be an increase in the production of TBE, which will show up as increased concentrations in surficial sediments in the future [60]. 

The main types of brominated flame retardants (BFRs) are polybromin-ated biphenyls (PBBs), PBDEs, and tetrabromobisphenol A (TBBPA). PBDEs have replaced PBBs, which are the first brominated organic compounds to be used as flame retardants and were phased out because of environmental issues, but are now being replaced by TBBPA (Renner, 2000). The global consumption of BFRs is estimated to be 203425 tons in 1999 with PBDEs accounting for 33% (Fig. 2.10). Deca-BDEs, 82% of total PBDEs, are the most widely used product. Domestic BFR consumption in South Korea in 2002 was 49050 tons, of which 25% (i.e., 12408 tons) was PBDEs with deca-BDE accounting for 12324 tons and penta- and octa-BDEs accounting for 84 tons (KMOE, 2005c). Imported amounts of each product in 2003 showed a similar distribution to the consumption estimated in 2002 (Fig. 2.10). In BFR market of Western Europe, consumption of PBDEs has declined from 26% in 1996 to 11% in 1998 (DEPA, 1999). Penta-BDEs product has been restricted for over one decade and is now banned within Europe. Furthermore, there has... 

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