Polychlorinated dibenzo-/ -dioxins PCDDs

Dioxin and Furan Emissions. The emissions of polychlorinated dibenzo-/)-dioxins (PCDD) and polychlorinated dibenzo-furans (PCDF) from incinerators (4) are of interest to the pubHc, scientists, and engineers. The U.S. EPA classifies 2,3,7,8-tetrachlorodibenzo-/)-dioxin (2,3,7,8-TCDD) as the most potent carcinogenic compound it has evaluated. It is also Hsted as the agency s most potent reproductive toxin (4). 

Chlorobenzenes are stable compounds and decompose slowly only under excess heating at high temperatures to release some HCl gas and traces of phosgene. It is possible, under certain limited conditions of incomplete combustion or pyrolysis, to form polychlorinated dibenzo-/)-dioxins (PCDDs) and dibenzofurans (PCDFs) from chlorobenzenes (Cm OROCARBONS and cm OROHYDROCARBONS, toxic aromatics). 

GC-EI-MS permits the direct analysis of mixtures, e.g., to analyze synthetic byproducts 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 dibenzo-dioxins (PCDDs), polychlorinated dibenzofuranes (PCDFs), or other volatile organic compounds (VOCs). 

This approach was initially developed to estimate the potential toxicity of mixtures of polychlorinated dibenzo- -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dioxin-like biphenyls (PCBs). Over the years, a number of different TEF systems for PCDDs, PCDFs and PCBs have been used. A system was internationally agreed upon at a WHO Consultation in 1997 (WHO-TEF) as published by Van den Berg et al. (1998). A WHO update has been published recently (Van den Berg et al. 2006) (Table 10.3). 

In several tests on compound sets that are structurally very different from the training set, including a larger set of pesticide molecules, Eq. (10.3) proved to be very robust and transferable. Recently, the method was applied to polychlorinated dibenzo-/)-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) [137]. As shown in Fig. 11.3. it was found that the COSMO-RS predictions appear to be even more accurate than the experimental data, especially at the low-solubility end. While the experimental results for many compounds show a scatter of more than a... 

At the same time the issues related to the unintentionally produced dioxins and furans, i.e., polychlorinated dibenzo- -dioxins (PCDDs) and PCDFs, attracted public attention in 1983 when investigations revealed that dioxins were detected in the fly ashes from municipal waste incinerators. Therefore, measures to monitor dioxins in the bottom sediment and aquatic animals and plants in the rivers, lakes, marshes and seawaters as well as the atmosphere were initiated in 1986. Investigations were implemented on the actual status of waste incinerators in 1984 and pulp and paper factories in 1990. On the basis of these findings, guidelines and administrative guidance on controlling emissions of dioxin-related chemicals were derived and established. 

The Stockholm Convention is a global treaty committing the international community to protecting human health and the environment from the potentially harmful effects of POPs (UNEP Chemicals, 2005). The United Nations Environment Programme (UNEP) has identified 12 most toxic POPs (the Dirty Dozen ) for control under the Convention, including 10 intentionally produced POPs pesticides/industrial chemicals (aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex, toxaphene and polychlorinated biphenyls (PCBs)) and two unintentionally produced POPs by-products (polychlorinated dibenzo-/ -dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)). In implementing the Convention, Parties to the Convention will take measures to restrict the trade, production and use of the intentional POPs and to reduce and, where possible, to ultimately eliminate the production and release of the unintentional POPs by-products. 

A. Bignert, M. Olsson, P.-A. Bergqvist, S. Bergek, C. Rappe, C. de Wit. B. Jansson, Polychlorinated dibenzo-/)-dioxins (PCDD) and dibenzofurans (PCDF) in seal blubber, Chemosphere, 19 (1989), 551-556. 

As noted earlier, polychlorinated dibenzo dioxins (PCDD) and polychlorinated dibenzo furans (PCDF) are two important classes of potentially toxic by-products that can form in trace levels (e.g., less than parts per... 

CK on the fecal excretion of polychlorinated dibenzo-/ -dioxin (PCDD) congeners and polychlorinated dibenzofuran (PCDF) congeners in rats administered the dioxin mixture [3]. 

Polychlorinated dibenzo- -dioxins (PCDDs) are highly toxic substances that are present in trace amounts as by-products of some chemical manufacturing processes. They have been implicated in a number of environmental incidents—for example, the chemical contamination at Love Canal and the herbicide spraying... 

Hagenmaier et al. (1987) studied the catalytic effect of fly ash on the formation and decomposition of dioxins and dibenzofurans under oxygen-deficient and oxygen-surplus conditions. While under oxygen-deficient conditions, fly ash catalyzed dechlorination or hydrogenation reaction, in the presence of surplus oxygen an increase in polychlorinated dibenzo-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) was observed. 

Wastes containing PAHs may be effectively destroyed by various incineration processes as mentioned briefly in the above section. Weber et al. (2001) have studied the mechanisms of formation of polychlorinated diben-zofurans (PCDF), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN) and polychlorinated benzenes (PCBz) from the degradation of PAHs in two types of incinerators, the stoker type- and the fluidized bed incinerators. Their studies have revealed the occurrence of a sequence of steps, such as the cleavage of C-C bond in the PAHs, chlorination at these cleaved positions, further chlorination or oxygen insertion at the ortho positions to the chlorine atoms in the intermediate chlorinated species. A perylene structure in soot is proposed as the basis for the observed PCDF pattern in the fluidized bed incinerators. Polychlorinated dibenzo-dioxins (PCDD) and the polychlorinated... 

Polychlorinated Dibenzo Dioxins (PCDDs) and Furans (PCDFs) are also toxic, and their concentrations are limited to low PPB levels by European and US regulations. Trace levels of these substances have been detected in PV 23 and also in chlor-anil, the raw material used to manufacture PV 23. 

Pigment manufacturers must comply with numerous environmental requirements including heavy metals, polychlorinated biphenyls (PCBs), polychlorinated dibenzo dioxins (PCDD), polychlorinated dibenzofurans (PCDFs), hejachoroben-zene, regulations for self-heating pigments, specific state or local county regulations, and customer specific requirements. 

PCDDs/Fs Polychlorinated dibenzo-/ -dioxins/polychlorinated dibenzofurans... 

Van den Berg, M., B.L.H.J. Craane, T. Sinnige, S. Van Mourik, S. Dirksen, T. Boudewijn, M. Van der Gaag, I.J. Lutke-Schipholt, B. Spenkehnk, and A. Brouwer. 1994. Biochemical and toxic effects of polychlorinated biphenyls (PCBs), dibenzo-/>-dioxins (PCDDs) and dibenzofurans (PCDFs) in the cormorant (Phalacrocorax carbo) after in ovo exposure. Environ. Toxicol. Chem. 13 803-816. 

Safe, S. 1990. Polychlorinated biphenyls (PCBs), dibenzo-/ -dioxins PCDDs), dibenzofurans (PCDFs), and related compounds environmental and mechanistic considerations which support the development of toxic equivalency factors (TEFs). Crit. Rev. Toxicol. 21 51-88. 

Published data on PCDD/Fs in the environment of the PRD is still limited. A short-term sampling scheme was conducted to determine the levels of particle-bound polychlorinated dibenzo- -dioxins and dibenzofurans (PCDD/Fs) in Guangzhou atmosphere and evaluate the impact of PCDD/ Fs to inhabitants. Samples were collected from four different districts of Guangzhou. The results showed that industrial activities had more influences on levels of PCDD/Fs in the sampled districts. The mean PCDD/Fs concentrations (i.e., mean I-TEQ values) of Huadu district, Liwan district, Tianhe district and Huangpu district were 3815-26,530 fg m-3 (104.6-769.3 fgl-TEQ m-3). Emission source analysis indicated that small diffuse sources were relatively important (Yu et al., 2006). 

Table 8.9. Polychlorinated dibenzo-/ -dioxins/ dibenzo-/ -furans (PCDDs/PCDFs) concentrations in bird samples from different countries... 

DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs) and hexachlorobenzene. Residues levels of industry-derived contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-/>-dioxins and dibenzofurans (PCDD/Fs) were also reviewed. Concentrations of these contaminants in different environmental compartments were expressed as unit equivalent to part-per-billion (ppb) level, unless otherwise specified. The cited values of concentrations from various literature sources were rounded to two significant digits for comparison. A number of factors can influence the concentrations in biological samples. Therefore, whenever possible, for biological samples the lipid normalized concentrations were cited for comparison. 

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. 

Dioxins (PCDDs) = Dioxin is a generic term used to denote a single compound or mixture of compounds derived from polychlorinated dibenzo-dioxins. The basic structure of all dioxins consists of two benzene rings joined by two oxygen atoms. There are 75 different polychlorinated dibenzo-p-dioxins and 135 dibenzofurans that are classified into groups termed homologs on the basis of the number of chlorine atoms in the molecule. 

A further example for the analysis of trace levels of pollutants is the determination of polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans in milk. The method includes gel permeation chromatography, alumina cleanup, and porous graphitized carbon chromatography, followed by analysis by GC/high-resolution MS. Moreover, the potential of porous graphitic carbon as an HPLC adsorbent for the isolation of halogenated aromatic compounds has been demonstrated by the fractionation of polychlorinated biphenyls (PCBs), chlorinated pesticides, polychlorinated dibenzo-p-dioxins (PCDDs), and... 

Broman D, Naf C, Rolfif C, Zebuhr Y, Fry B, Hobbie J. 1992. Using ratios of stable nitrogen isotopes to estimate bioaccumulation and flux of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in two food chains from the northern Baltic. Environ Toxicol Chem 11 331-345. 

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