Environmental concerns bromine compounds

Other brominated compounds of environmental concern are also chiral. Polybrominated biphenyls, like PCBs, were used as capacitor fluids in mixtures of congeners (e.g. Fire-master), and are also atropisomeric [4]. While HBCDD is the most common chiral brominated flame retardant, others exist, such as 2,3-dibromopropyl-2,4,6-tribromophenyl ether (Figure 4.7). As of this writing, little is known about environmental occurrence, fate, and effects of these other chiral flame retardants, and with one exception [5] nothing has yet been published on their enantiomers. 

Environmental concerns over brominated, and other halogenated products will negatively impact on their future growth as end users pursue less controversial substitutes including non-halogenated phosphorus, magnesium hydroxide and silicone compounds. 

Organic Bromine. This is an efficient flame retardant that can be greatly syner-gized by addition of antimony trioxide. Since aliphatic bromine is too unstable for plastic processing, preferred compounds are polybrominated diphenyl ethers for thermoplastics, and tetrabromo bisphenol A and tetrabromophthalic anhydride for epoxies and polyesters. In a fire, it does produce smoke and toxic corrosive gases, so this must be considered in specific applications. In Europe, environmental concerns may limit the use of bromine. 

Organic Chlorine. This is a good flame retardant, less expensive but less efficient than bromine. It too is greatly synergized by antimony trioxide. A particularly popular compound is Dechlorane Plus, the adduct of hexachlorocyclopentadiene with cyclooctadiene. Chlorinated paraffins are also widely used. Like bromine, chlorine may be limited by problems with smoke, toxic corrosive gases, and environmental concerns. 

The environmental scrutiny that has impacted halogenated flame retardants has primarily focused on brominated diphenyl oxides such as DBDPO. There is concern that these compounds release dioxins when burned. Activity has primarily been in Europe. Currently there are no legislative bans or limits on halogenated flame retardants anywhere in the world, and there are not any on the near-term horizon. However, there are some voluntary bans on selected brominated compounds (particularly DBDPO and related types) in some of the green countries of Europe. In many cases, these brominated products are replaced by other brominated products that are not under immediate suspicion. 

Today, there is pressure on some bactericides due to environmental concerns and human health hazard and only three points of discussion should be briefly mentioned here. First, the use of bactericides containing chlorine or bromine in the molecule is discussed in Europe because of AOX problems in waste water treatment. Second, there is an increasing pressure on bactericides based on formaldehyde or formaldehyde releasing compounds due to health hazards. The third issue is the R43 labeling (sensitizing through skin contact possible) of products which contain more than 15 ppm CMIT/MIT in a three to one ratio in Europe. 

The PBDEs are of particular concern. They are incorporated into polymer matrices, but are not covalently bonded and readily leach out of substrates holding them. These compounds are similar in structure to PCBs, are persistent organic polluters (POPs), and are resistant to environmental degradation and metabolism. They can be absorbed via inhalation, ingestion, and dermal contact. The less-brominated PBDE species (tetra-, penta-, and hexa- moieties) have been found in human blood, adipose tissue, and breast milk. These bioaccumulate in human adipose tissues. 16 ... 

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