Polychlorinated dibenzofurans furans

Group of isomers with the same carbon skeleton and number of chlorines, e.g., TeCDDs Rat hepatoma cell line Polychlorinated biphenyls Polychlorinated dibcnzo-p-dioxin Polychlorinated dibenzofuran Polychlorinated dibenzo-p-dioxin and -furan Tetrachlorodibenzo-p-dioxin (-furan) Pentachlorodibenzo-p-dioxin ( furan) Hexachlorodibenzo-p-dioxin (-furan) Heptachlorodibenzo-p-dioxin ( furan)... 

Czuczwa JM, Hites RA (1985) Historical record of polychlorinated dioxins, furans in Lake Huron sediments. In Keith LH, Rappe C, Choudhary G (eds) Chlorinated dioxins and dibenzofurans in the total environment II. Butterworth, Toronto p 59... 

Kuroki H, Haraguchi K, Masuda Y (1984), Chemosphere 13 561-573.. .Synthesis of polychlorinated dibenzofuran isomers and their gas chromatographic profiles44 Riehle U (1990), Analytik der polyhalogenierten (Brom/Chlor) Dibenzodioxine und Dibenzo-furane und deren thermische Bildung in einem Verbrennungsmotor44, Dissertation, Universitat Ulm... 

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... 

These chemicals have received intense international attention in recent years because of their ubiquity, persistence, high bioaccumulation potential and harmful biological effects. Under the Stockholm Convention on POPs (see Chapter 1), 12 chlorinated chemical substances have been banned or severely restricted. These include dioxins and furans (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, PCDD/Fs),... 

Human poisonings from consumption of PCB mixtures include the well-known Yusho rice oil poisoning in Japan (1968), where PCB fluids became mixed inadvertently with rice oil used for cooking. The actual level of contamination of the rice oil was low, about 0.2%. About 2000 people were poisoned in 1978 in a similar incident in Yu-Cheng, Taiwan. The principal symptoms in both cases were related to headache. Adipose tissue from Yusho patients was found to contain up to 75 ppm of PCBs. Cancer development was not statistically connected with people poisoning by PCBs. Later investigations have shown that the toxicity of these PCB-contaminated rice oils was probably not primarily due to the PCBs themselves, but to the traces of polychlorinated dibenzofurans (PCDFs), which they contained. We will consider the formation of furans and dioxins in the following section. 

To date, there has been little published information on the emissions of substances such as volatile organic compounds (VOC), dioxins (polychlorinated dibenzo-dioxins, or PCDD), furans (polychlorinated dibenzofurans, or PCDF) and heavy metals from lime kilns. 

Dioxin is a term used to describe a large group of chemical compounds having a similar basic structure. The most common subgroup of dioxin compounds (of which there are 75 different varieties) comprises those which include chlorine atoms. A few are toxic the most toxic is 2,3,7,8-tetrachlorodibenzo(para) dioxin (2,3,7,8-TCDD). There are also 135 polychlorinated dibenzofuran corrtpotmds, known as furans. ... 

Figure 11.20 Typical structures of the polychlorinated dibenzo-p-dioxins (PCDDs, i.e., dioxins ), polychlorinated dibenzofurans (PCDFs, i.e., furans ) and polychlorinated...

Because PCB molecules have two benzene rings or 12 carbon atoms as well as some chlorine atoms, they wUl bum at high temperatures when ignited. The main danger from a PCB fire is not the PCB itself, but the formation of extremely toxic byproducts of combustion, such as polychlorinated dibenzodioxins, polychlorinated dibenzofurans, and hydrogen chloride gas, which often produce immediate respiratory effect. The formation of dioxins and furans... 

In addition, the concern about e-waste not only focuses on its vast quantity generated daily, but also more on the need to handle the toxic chemicals embedded in it. It is well known that e-waste contains lead, beryllium, mercury, cadmium (Cd), and brominated flame retardants (BFRs) among other chemical materials [3]. Furthermore, highly toxic chemicals such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and dibenzo-furans (PBDD/Fs) can be formed during the recycling process [4]. 

As discussed in the earlier survey (1), a biogenic source of polychlorinated dibenzo-p-dioxins and dibenzofurans is peroxidase-catalyzed transformation of chlorophenols as first reported by Oberg and Rappe (2041-2044). More recent studies confirm these observations (2045-2048). In addition to lactoperoxidase and horseradish peroxidase, human leukocyte myeloperoxidase catalyzes in vitro formation of dioxins and dibenzofurans from chlorophenols (2046, 2047). Formation rates are in the pmol/mol range (Scheme 3.6) demonstrating that a human biosynthesis of dioxins and furans is not only possible but also likely. These observations are reinforced by the reported in vivo (rats) conversion of the pre-dioxin nona-chloro-2-phenoxyphenol to octachlorodibenzo-p-dioxin (OCDD) (2049), and the production of hepta- and octachlorodibenzo-p-dioxin in the feces of cows fed pentachlorophenol-treated wood (Scheme 3.7) (2050, 2051). 

More recently, environmental contamination by chlorinated dioxins and furans released during combustion processes has been recognized. These substances are formed not only during incineration of chlorinated phenols, but also during combustion of materials in home fireplaces and municipal incinerators (10). Chlorinated dioxins and dibenzofurans also are formed during fires involving polychlorinated biphenyls (15). 

Several countries have been given restrictions on the use of compounds because of potential toxic effects in humans. In the European Community, the use of tris(2,3-dibromopropyl) phosphate (EC Directive 76/769/EEC) and tris(l-aziridinyl)phosphine oxide (EC Directive 83/264/EEC) in textiles has been banned. In 1977, the U.S. Consumer Product Safety Commission banned the use of tris(2,3-dibromopropyl) phosphate in children s clothing (ICPS, 1995). The European Community has also banned the use of PBBs in textiles (EC Directive 83/264/EEC). Several countries have either taken or proposed regulatory actions on PBBs. In addition, controls on the emissions of dioxins and furans from municipal solid waste incinerators have been implemented in the United Kingdom under the Environmental Protection Act (1990). Germany has developed rules for the maximum content of selected 2,3,7, and 8 substituted polychlorinated dibenzo-pura-dioxins and dibenzofurans in products. Recently, the European Commission has issued a proposal to ban the production and use of PentaBDE. In U.S. A., on the other hand, there are currently no regulations on PBDE production or use. PBBs have not been used widely in Europe and also in U.S.A. the production of the main mixture, hexabromobiphenyl (Firemaster BP-6), ceased in 1974, after the Michigan disaster. ... 

Dioxins are a family of the most toxic chlorinated organic compounds known to science, numbering around 75 dioxins and 135 related furans. These can cause cancer and are ECD for humans, even at very low exposure levels, since minute amounts, can bio-accumulate due to their ease of solubility in body fat (dioxins are hydrophobic, water-hating and lipophilic, fat-loving ). Number and position of chlorine atoms in the molecule has a considerable effect on toxicity, and 17 dioxins are classed as highly toxic. These include polychlorinated dioxins (PCDD) and dibenzofurans (PCDF) which are by-products of the chlorine bleaching of paper, the burning of chlorinated hydrocarbons (such as pentachlorophenol, PCB, and PVC) and the incineration of municipal/medical... 

Q.6.3 Waste-to-energy processes can generate toxic emissions including dioxins, furans, NO , SO , CO, CO2, polychlorinated dibenzo-p-dioxins and dibenzofurans, and heavy metals. T or F ... 

This chapter is divided into seven main sections. The first of these sections is focused on technological contaminants, namely heterocyclic amines, acrylamide, furan, chloropropanok and their fatty acid esters, polycycKc aromatic hydrocarbons, monocyclic aromatic hydrocarbons, nitroso compounds, and ethyl carbamate. Other sections deal with microbial toxins (mycotoxins and bacterial toxins), persistent organohalogen contaminants (such as polychlorinated biphenyls, dibenzodioxins and dibenzofurans), chlorinated ahphatic hydrocarbons, pesticides (persistent chlorinated hydrocarbons and modem pesticides), veterinary medicines and contaminants from packaging materials. Presented for each of these contaminants are structures, properties, occurrence and the main sources of dietary intake, mechanisms of formation, possibilities of food contamination, prevention and mitigation and health and toxicological evaluations. 

Dioxins and furans are not produced deliberately but are produced imintentionally as by-products of combustions of organic matter in the presence of chlorine. Dioxins and furans consist of 135 possible chlorinated (or bromi-nated) dibenzofuran and 75 chlorinated (or brominated) dibenzo-p-dioxins with from one to eight chlorine (bromine) substituents (Figure 19.2). PCDDs/DFs are foxmd as by-products during the manufacture of some industrial chemicals such as PCBs, polychlorinated naphthalenes, chlorinated phenols, chlorinated phenoxyacids, polychlorinated diphenyl ethers, pol5winyl chlorides. 

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