Polychlorinated dibenzodioxins production

Dioxins are a particular group of chlorinated organic molecules which have been associated with pulp and paper production and are a concern because of their extreme toxicity. There are two groups of molecular types which fall into the general category referred to as dioxins. These are the polychlorinated dibenzodioxins (PCDDs) and the polychlorinated dibenzofurans (PCDFs). The structures of these molecules are shown in Figure 10.4. 

Chlorinated micropoUutants are harmful for man and environment due to their toxicity, persistence, and bioaccumulation. Persistent compounds are very stable and difficult to get metabolized and mineralized by biological and chemical processes in the environment, and as a result, they have become ubiquitous in water, sediments, and the atmosphere bioaccumulation is the result of the lipophilicity of these compounds. Polychlorinated dibenzodioxins and -furans (PCDD/F) are not produced purposely like many of other chlorinated technical products, such as chlorinated biocides DDT, lindane, and toxaphene. The production and use of persistent organic pollutants (POPs), the dirty dozen has now been banned worldwide by the Stockholm protocol. It should be mentioned that about 3000 halogenated products have now been isolated as natural products in plants, microorganisms, and animals," but the total amount of these products is much smaller compared to xenobiotics. 

United States because they build up in the environment and can cause harmful health effects, they are still in use in many other countries. Polychlorinated dibenzodioxins and polychlorinated dibenzofurans (dioxins) (Fu et ah, 2003) consist of 210 different compounds that have similar chemical properties (Bhandari and Xia, 2005). This class of compounds is persistent, toxic, and bioaccumulative. They are generated as by-products during incomplete combustion of chlorine containing wastes such as municipal solid waste, sewage sludge, and hospital and hazardous wastes (Bhandari and Xia, 2005). PCBs were widely used in the past and now contaminate many industrial and natural areas. 

Dioxin A family of chemicals with related properties and toxicity. There are 75 different dioxins, or polychlorinated dibenzodioxins (PCDDs) 135 different furans, or polychlorinated dibenzofurans (PCDFs) and 209 different polychlorinated biphenyls (PCBs). Each different form is called a congener, a member of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity as contaminants in commercial products. Tests on laboratory animals indicate that it is one of the more toxic anthropogenic (man-made) compounds a term used interchangeably with 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD Disease prevention Measures used to prevent a disease or reduce its severity Dispersoids The particles of a dispersion... 

In response to the continuing discovery of the persistence, bioaccumulative properties, and toxicity of POPs, regional, national and international policies ban the intentional production of compounds, such as polychlorinated biphenyls (PCBs), several organochlo-rine pesticides, such as mirex and dieldrin, and the brominated flame retardants poly-brominated diphenyl ethers (penta-BDE and octa-BDE, and most recently, deca-BDE). Policies and programs have also targeted the unintentional production and release of POPs such as polychlorinated dibenzodioxins and furans (PCDD/Fs). Evidence of the success of these policies has been seen in immediate reductions of air concentrations, followed by declining concentrations in water bodies, soils, biota and our food supplies... 

Polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/PCDFs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) are now ubiquitous in the environment. Their occurrence in indoor air mainly results from the frequent use of chemical products such as paints, glue, sealants, fire retardants and wood protection agents up to the mid-1980s. Furthermore, PCDDs/PCDFs and PAHs are always formed to some extent during incomplete combustion processes. A list of possible sources is given in Table 1.4-1. 

Persistent or non-degradable environmental chemicals - even those with low volatility - may be dispersed around the globe. Polychlorinated biphenyls (PCB), polychlorinated dibenzodioxins and dibenzofurans (PCDD, PCDF), l,l,l-trichlor-2,2-bis(4-chlorphenyl)-ethan DDT, hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB) have been found in samples from the Arctic and Antarctic and in the tissues of marine animals. Although the open use of many of these chemicals has been prohibited in most industrialized countries, considerable residues still remain in the environment. It is estimated that about 20% of the global production of PCBs (230 000 t/a) persists in the upper layers of the oceans and that a further 7901 are present in the atmosphere (Fiedler and Lau, 1998). Such contamination may accumulate in organisms and have negative effects that go as far as the death of whole populations in ecosystems (Jdrgensen, 1998). 

PCBs and PCDDs. In Diarylide Yellow manufacture, the use of formate buffer to enhance pigment transparency for offset ink was discontinued in the nineteen seventies, when it was realized that polychlorinated biphenyls were being produced as an undesirable by-product of the coupling reaction. In Phthalocyanine Blue crude synthesis, the commonly used solvent, trichlorobenzene, was also discontinued in the US, as a potential source of poly-chlorinated biphenyls. More recently, use of chloranil, manufactured from chlorinated phenols, has been discontinued in the synthesis of dioxazine violet crude and sulfonated dioxazine acid dyes, so as to minimize by-product formation of polychlorinated dibenzodioxins and dibenzofurans (PCDDs/PCDFs). A new grade ofhigh purity chloranil is now produced from hydroquinone for dye and pigment manufacture. 

Since 1979, many studies have identified other chlorinated aromatic compounds present in trace levels in the PCBs, or produced as incomplete oxidation products in PCB fires . These compounds include polychlorinated dibenzofurans (PCDFs), polychlorinated biphenylenes (PCBPs), polychlorinated pyrenes (PCPYs), and polychlorinated chrysenes (PCCYs), Polychlorinated dibenzodioxins (PCDDs) have also been detected from fires where trichlorobenzenes were present with PCBs as the dielectric fluid Animal tests and industrial incidents have shown some... 

GC-EI-MS can be used for the direct analysis of mixtures, e.g., to analyze synthetic by-products an advantage that made GC-EI-MS benchtop instruments become widespread in modem synthetic laboratories. The GC-EI-MS combination is especially successful in monitoring environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofuranes (PCDFs), or other volatile organic compounds (VOCs). 

Polychlorinated dibenzodioxins and furans (PCDD/Fs) are persistent, bioaccumulative toxic by-products of incomplete combustion—whether manmade or natural—and certain chemical processes. 2,3,7,8-tetrachlorodibenzodioxin (TCDD) is the most toxic of the family of 210 compounds. 

This technology is applicable for the treatment of polychlorinated biphenyls (PCBs) and other halogenated contaminants, such as insecticides, herbicides, pentachlorophenol (PCP), lindane, and chlorinated dibenzodioxins and furans. The contaminant matrix can be soil, sludge, sediments, or oil. It can treat oily sludges, coal by-products, and wood-treating compounds. 

Voogt P de, Brinkman UAT (1989) In Kimbrough RD, Jensen AA (eds) Production, properties and usage of polychlorinated biphenyls. Halogenated biphenyls, terphenyls, naphthalenes, dibenzodioxins and related products. Elsevier, Amsterdam, p 3... 

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