PCBs flame retardants

In 1978 the poly-chlorobifenyls (PCBs) flame-retardants were overreached by the bromated flame-retardants as the most important flame-retardants. They are used in the protection of electronic apparatuses, clothing and furniture. They have the advantage that the start of a fire is retarded and that they have an inhibition effect on the extension of fire. 

These industrial chemicals are widely used as the precursors for a wide range of products, which include agrochemicals, pharmaceutical products, polychlorinated biphenyls (PCBs), and polybro-minated diphenyl ether flame retardants. For almost all of them, serious concern has arisen over their adverse environmental effects. 

The structural range of industrially important representatives of these groups is enormous, and includes chlorobenzenes (solvents), polychlorinated biphenyls (PCBs) (hydraulic and insulating fluids), and polybrominated biphenyls and diphenyl ethers (flame retardants). There is widespread concern over both the persistence and the potential toxicity of all these compounds, and sites that have become contaminated during their production represent a threat both to the environment and to human health. Pathways for the aerobic bacterial degradation of chlorobenzenes and chlorobiphe-nyls, and their brominated analogs have been discussed in Chapter 9, Part 1. 

Commercial mercury, testing of, 76 44 Commercial oil reclaimers, 27 425 Commercial PCBs, 73 137-138 Commercial phosphorus flame retardants, 77 487 499... 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), Pentachlorophenol m(PCP, mercury and organic mercury compounds, cadmium, lead and organic lead compounds, brominated flame retardants), nonylphenol/ethoxylates (NP, NPEs) amongst others in the OSPAR Strategy with regard to Hazardous Substances... 

Risk avoidance often faces conflicts in objectives. In this way substance innovations for improved fire and explosion protection in the second half of the last century also made a major contribution to many environmental and health risks discussed today CFCs, PCB, chlorinated solvents, brominated flame retardants and also cutting oils in emulsion form must be mentioned at this point. This means that chemical/technical innovation originally aimed to achieve more operational safety. Additional improvements related to environmental or health aspects were not taken into account at the time of the innovation. 

The POCs include, but are certainly not limited to the polychlorinated biphenyls (PCBs) and the organochlorine pesticides, including those in current use, restricted use and historic use brominated flame retardants including polybrominated diphenyl ethers PAHs and the sometimes more toxic transformation products of these chemicals. Table 1 summarizes information on some of the POCs more commonly detected in alpine environments. 

Polychlorinated biphenyls (PCB) Polybrominated biphenyls Polybrominated biphenyl ethers Flame retardants... 

Polychlorinated biphenyls (PCBs), known by their trade marks of Arochlor (Monsanto U.S.), Phenochlor (in France), and Clophen (in Germany) are chemically similar to the chlorinated insecticides. Although not used for this purpose, their existence and persistence in the environment is well established. They were used to make more flexible and flame retardant plastics and are still used as insulating fluids in electrical transformers since there is no substitute in this application. They have been made by Monsanto since 1930 and were first discovered as a pollutant in 1966. U.S. production peaked at 72 million lb in 1970 but in 1975 it was down to 40 million Ib/yr because in 1971 Monsanto voluntarily adopted the policy of selling PCBs only for electrical systems. At least 105 PCBs are present in the environment. 

The polychlorinated biphenyls (PCBs, coplanar biphenyls) have been used in a large variety of applications as dielectric and heat transfer fluids, lubricating oils, plasticizers, wax extenders, and flame retardants. Their industrial use and manufacture in the USA were terminated by 1977. Unfortunately, PCBs persist in the environment. The products used commercially were actually mixtures of PCB isomers and homologs containing 12-68% chlorine. These chemicals are highly stable and highly lipophilic, poorly metabolized, and very resistant to environmental degradation they bioaccumulate in food chains. Food is the major source of PCB residues in humans. 

The chemicals tested were either organochlorine pesticides, polychlorinated biphenyls (PCBs) or polybrominated diphenyl ethers (PBDEs) (the latter are used as flame retardants) (www.wwf.org.uk/chemicals, accessed November 2006). 

Hardy ML. 2000a. Properties of the major commercial PBDPO flame retardant, DBDPO, in comparison to PBB and PCB. Organohalogen Compounds 47 233-236. 

Polychlorinated Dibenzo-(p)-Dioxins and Dibenzo-Furans. Another group of compounds that we need to specifically address are the polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzo-furans (PCDFs) (Fig. 2.15). The PCDDs and PCDFs are not intentionally produced but are released into the environment from various combustion processes and as a result of their occurrence as unwanted byproducts in various chlorinated chemical formulations (e.g., chlorinated phenols, chlorinated phenoxy herbicides see Alcock and Jones, 1996). Because some of the PCDD and PCDF congeners are very toxic (e.g., 2,3,7,8-tetrachloro dibenzo-p-dioxin, see margin), there have been and still are considerable efforts to assess their sources, distribution, and fate in the environment. Similarly to the PCBs or DDT (see above), the PCDDs and PCDFs are highly hydrophobic and very persistent in the environment. It is therefore not surprising that they have also been detected everywhere on earth (Brzuzy and Hites, 1996 Lohmann and Jones, 1998 Vallack et al., 1998). Finally, we should note that polybrominated diphenylethers (PBDEs, see margin) that, like the PBBs (see above), are used as flame retardants, are of increasing environmental concern (de Boer et al., 2000). 

The POP protocol elaborated on occasion of the Stockholm Convention in 2001 contained 12 compounds, known as the dirty dozen aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, HCB, mirex, PCBs, pol veil I orod i be nzo-/ -d i ox ins. polychlorodibenzofurans and toxaphene. After several years of implementation other compounds, were also included HCHs, PAHs, certain brominated flame retardants, perfluorooctanesulfonic acid (PFOS) and pentachlorobenzene (http // www.chem.unep.ch/pops/). This protocol is aimed to control, reduce and/or eliminate discharges, emissions and spills of POPs into the environment. 

PCBs are industrial compounds used as industrial, dielectric and heat transfer fluids, organic solvents, flame retardants, plasticizers, sealant and surface coatings. They may also be released to the atmosphere by waste incineration (Fig. 3). The worldwide production of this compound has been 1.3 million tonnes, of which 97% in the northern hemisphere [23]. The amount of chlorine atoms in the biphenyl mixtures is related to the duration and temperature of the chlorination process. The commercial mixtures were distributed under names such as Aroclor (Monsanto, USA) or Clophen (Bayer, EU). The chlorine atoms can substitute the para, meta and/or ortho positions of the biphenyls. There are 209 possible congeners. PCBs can be divided into nine isomeric groups and one decachlorobiphenyl, all with an empirical formula of C Hjo-uCln (n = 1-10) (Fig. 4). 

Milk. Mother s milk is rich in lipids and lipoproteins. Milk thus serves as an ideal route for the elimination of both water-soluble and fat-soluble chemicals from the mother s body. For example, the DDT metabolite DDE, the flame retardant mirex, and the polychlorinated biphenyls (PCBs) often have been detected in mother s... 

A special class of non-reactive additives in polymer materials are CPs, which have plasticizing and flame-retarding properties. They were found in an emission test of a television set with a maximum concentration of 2.2 tgm-3 after 220 h of operation (Wensing, 2003). CP are used as a substitute for PCBs, which have been prohibited worldwide since 2001. The detection of CP in indoor air needs a complex analytical procedure because the amount of single compounds in a CP mixture is high. Therefore, this class is seldom found during standard TD-GC-MS analysis. 

PBDEs Considered the new PCBs, polybrominated diphenyl ethers are a group of brominated flame retardants used in lots of products, including the foam in couches and mattresses, and plastic TV and computer monitors (Dell and HP, among others, have banned them). One of the reasons PBDEs are so hard to avoid is that they re not bound to the molecules in materials, so toxic residue can escape in the form of dust. Most kinds of PBDEs have been banned in Europe since 2004, and American women carry ten to seventy times as many PBDEs in their breast milk, tissues, and blood as Europeans do. Exposure to PBDEs during fetal development can negatively affect how the brain functions. 

DDT and PCBs remain the most widespread contaminants in human milk around the world. Other common contaminants of mother s milk include flame retardants, pesticides, wood preservatives, toilet deodorizers, and dry-cleaning fluids. 

China was one of the first proponents of the Stockholm Convention, but only recently have we started to prepare the national inventory of PCDD/Fs and PCBs, which are among POPs specified by the convention. PBDEs have been extensively used as flame retardants in various products, and recently, the environmental problems associated with these compounds have become great concern. Data about the pollution status of these pollutants were extremely scarce in China due to the lack of regulations and monitoring capacity. In this chapter, sources of PCDD/Fs, PCBs, and PBDEs and their levels in the environmental media in China are summarized, based mainly on available scientific literature. The challenges for management of these compounds are also discussed. 

PBDEs have been called one of the emerging pollutants . They are extensively used as flame retardants (FRs) in various polymers and especially in electronic equipment such as computers and television sets. Similar to PCBs, there are 209 congeners of PBDEs, and the nomenclature system is also based on the same IUPAC scheme used for PCBs. But unlike PCBs, for which large-scale production has been banned for many years, PBDEs are still widely used and their transport and transformation in the environment are still poorly understood. The global demand for PBDEs has increased rapidly since the 1970s. In 1992, the global production of PBDEs was 40,0001, but in 1999 this had increased to approximately 70,0001 (Renner, 2000). 

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