Bromine environmental concerns

Situated between the solid and gaseous states as the only non-metallic element liquid at ambient temperature, bromine is sandwiched in the periodic table between the ubiquitous chlorine and the rather rare iodine. In terms of production volumes it is neither a bulk commodity chemical like chlorine, nor a speciality chemical like iodine. And commercially, bromine is beset by uncertainty. Until the 1970s, the major market forbromine was in dibromoethane - a co-additive for leaded petrol. The phase-out of lead in petrol could have spelled the collapse of the bromine industry, but alternative bromine markets developed and the industry both rationalised and flourished. However, although world bromine production continues to increase slowly, fresh environmental concerns have emerged and the industry is once more under threat. Details are given. 19 refs. 

For more demanding applications, tetrabromophthalate ester is a thermally stable liquid fire-retardant additive with a bromine content of approximately 45wt%. Decabromodiphenyl ether is used for foamed soft PVC for thermal insulation even if diphenyl ether-free systems have been developed because of environmental concerns. 

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. 

A key driver of change and new product development in the plastics additives markets is a host of environmental concerns. This is seen most dramatically in PVC where concerns over the use of heavy-metal heat stabilizers based on lead have led to a widespread conversion to tin-based materials and even to nonmetallic stabilizers. The widely used phthalate-based Plasticizers for flexible PVC have come under fire because of concerns over their potential adverse effects on the human reproductive systems. Concerns over the potential for brominated FRs to form dioxins are fueling the development of new halogen-free systems. 

In recent years, environmental concerns over toxic smoke generation during fire and end-of-life incineration of electronic equipment containing brominated... 

Phosphorus compoimds comprise, value-wise, the second largest group of flame retardants, and are probably the fastest growing segment as a result of environmental concerns with various bromine—antimony retardants. An earlier review is... 

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. 

Of major concern are the health and environmental impacts of the abundant chlorinated and brominated hydrocarbons (ref. 2). These materials have numerous industrial applications as pesticides, solvents, propellants, refrigerants, plastics, fire retardants and extinguishers, disinfectants for drinking water, pharmaceuticals and electronic chemicals. Many chemical manufacturers utilize chlorinated and brominated organics as intermediates. It is estimated, for instance, that almost 85 % of the pharmaceuticals produced in the world require chlorine at some stage of synthesis. 

Most circuit boards are FR-4 boards that meet standards for fire safety by the use of brominated epoxy resins in which the reactive flame-retardant tetrabromobisphenol A (TBBPA) forms part of the polymeric backbone of the resin. Alternative flame-retardant materials are used in only 3-5 per cent of the FR-4 boards, but additional alternative flame-retardant materials are also imder development. Little information exists concerning the potential environmental and human health impacts of the materials which are being developed as alternatives to those used today that are based on brominated epoxy resins. 

The Danish Environmental Protection Agency has started work to draft a national plan to control brominated flame retardants, and has published what officials claim to be the most exhaustive national survey analysing the flow of such substances and assessing possible substitutes for specific applications. The survey found that the major source of BFRs emissions in Denmark was from evaporation from products already in use, and underlines previous concerns about the possible harm due to bioaccumulation. Denmark is to join Sweden in urging international action to curb the use of brominated flame retardants. 

The uncertainties identified in connection with these conclusions relate to the suitability of the current risk assessment approach for secondary poisoning, bioaccumulation, and whether or not debromination of the higher brominated molecules gives rise to other more toxic and bioaccumulative BDEs (such as Penta) is occurring at a significant rate in the environment. The risk assessors conclude that this combination of uncertainties raises concerns about the possibility of long-term environmental effects that cannot easily be predicted and that a strict PEC/PNEC approach may not be appropriate for this substance. 

Both HBCD and PBDEs are examples of brominated flame retardants (BFRs). The recent growth in the number of scientific papers addressing the environmental presence and impacts of such chemicals has been quite phenomenonal. In a similar vein, there has been a dramatic rise in concerns related to the environmental presence and impacts of perfluorinated chemicals (PFCs). Chapters 2 and 3 thus address current knowledge and research... 

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