Polychlorodibenzo-p-dioxins PCDDs

Electrophilic substituent factors for the -C6H5 XC1X and -OC6H5 XC1X groups, needed to calculate the OH radical addition rate constants for polychlorinated biphenyls (PCBs), polychlorodibenzo-p-dioxins (PCDDs), and polychlorodibenzofurans (PCDFs), appear in Atkinson (1996), with discussion of an approach to calculating the rate constants for the PCDDs and PCDFs. The room temperature rate constants for the reactions of the OH radical with phenanthrene and anthracene, recently measured by Kwok et al. (1994,1997), are lower by factors of 2.5-8 than the previous recommendations and rate data (Biermann et al., 1985 Atkinson, 1989), casting doubt on the previously proposed correlation between the OH radical addition rate constant and ionization potential (Biermann et al., 1985). 

Jensen AA. 1987. Polychlorobiphenyls (PCBs), polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) in human milk, blood and adipose tissue. Sci Total Environ 64 259-293. 

Reischl A, Reissinger M, Thoma H, Hutzinger O (1989), Chemosphere 18 561-568. Accumula-tion of organic air constituents by plant surfaces - IV Plant surfaces a sampling system for atmospheric polychlorodibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) ... 

TCBTs are relatively persistent and non-flammable (and therefore useful in hydraulic oils). Pyrolysis in a closed system for two days in the presence of hydrogen peroxide at 300 °C produced as main components chlorinated benzo-phenones, fluorenes, fluorenones, xanthenes, and xanthones. Polychlorodiben-zofurans (PCDF) and polychlorodibenzo-p-dioxins (PCDD) were formed in much lower concentrations than from PCB product Pyralene T1 under identical conditions [84]. In pyrolysis at 450-700 °C with excess oxygen TCBTs produce more PCDFs and PCDDs. In parallel with the behavior of PCBs, PCDFs are formed in significantly higher amounts than PCDDs from PCBTs [86],... 

Morselli L, Brocco D, Pirni A. 1985. The presence of polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDEs), and polychlorobiphenyls (PCBs) in fly ashes from various muidcipal incinerators under different technological and working conditions. Ann Chim 75 59-64. 

Polychlorodibenzo-p-dioxins (PCDDs) and poly-chlorodibenzofurans (PCDFs) are mostly produced by incineration, although they are also a waste product of the pulp/paper and chemical manufacturing industries (Duarte-Davidson et al. 1997).There are potentially 75 PCDD and 135 PCDF congeners (see Fig. 7.17), but PCDDs from most biological samples contain only the tetra- to octachloro congeners with 2,3,7,8 chlorination the absence of the other congeners has been attributed to rapid metabolism and excretion (Ahlborg... 

In 2002, Rodgman and Green (3300) reviewed the literature on tobacco smoke toxicants. In their review, they discussed the polychlorodibenzo-p-dioxins and polychlorodibenzofurans (PCDDs and PCDFs) identified in tobacco and tobacco smoke. Rodgman and Green noted that among the smoke toxicants conspicuous in their absence from all toxicant lists except that of Fowles and Bates (1217) are the polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs). The presence of dioxins in cigarette smoke was first reported in 1980 by Crummett (854). There are at least five other publications in which the presence of dioxins... 

Polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) are two classes of compounds that are of environmental concern because of the high toxicity of those isomers with 2,3,7,8-tetrachloro-substitution [12]. The PCDDs/PCDFs are monitored in air, rain, effluents, soil, and biota matrices. Usually, the total concentration of all PCDD/PCDF congener groups (i.e., total tetra-chlorinated dioxins, total pentachlorinated dioxins, etc.) and the concentrations of each of the seventeen 2,3,7,8-substituted toxic isomers are monitored. Such determinations require extensive sample preparation, sixteen expensive C 12-2,3,7,8-substituted internal standards [13], and mass spectrometers of high capital cost. High-resolution MS [14,15] or triple-stage quadrupole MS (TSQMS) [16-18] is necessary in order to differentiate between (1) PCDDs/PCDFs and interferences, such as polychlorinated biphenyls [19], and (2) Ci2-PCDFs and native PCDDs. 

The name of PCDD/Fs or dioxins is given to a family of compounds of different number of chlorine atoms in the molecules (congeners). Totally, there are 75 of polychlorodibenzo-p-dioxins and 135 polychlorodibenzo-p-furans that might be formed. Almost all of them have been found in the environmental matrices (air, soil, sediments and animals tissue) and abiotic... 

PCDD-PCDF polychlorodibenzo-p-dioxins and polychlorodibenzo-furans... 

PCDD polychlorodibenzo-p-dioxin polychlorinated dibenzo-p-dioxin... 

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