2,3,7,8-tetrachloro-dibenzo-dioxin

Figure 3. Clearance of activity from the body of rats given a single oral dose of 50 fig/kg (0.14 fxCi/kg) 2,3,7,8-tetrachloro-dibenzo- -dioxin. Each value represents the mean SE for three...

NP NPEC OC OP OPEC PCB PCDBT PCDD PCDF PCP PFB RA TCA TCDD TCF TCMTB TOC VSC VOC Nonylphenol Nonylphenol ethoxycarboxylate Organo chlorine Octylphenol Octylphenol ethoxycarboxylate Polychloroinated biphenyls Polychlorinated dibenzothiophene Polychlorin ated dib enzo-p - dioxins Polychlorinated dibenzo-p-furans Pentachlorophenol Pentafluorobenzyl Resin acids 2,4,6-Trichloroanisole Tetrachloro dibenzo dioxin Totally chlorine- free 2-(Thiocyanomethylthio)-benzothiazole Total organic carbon Volatile sulphur compounds Volatile organic compounds... 

Of additional concern is the thermal conversion of PCBs to polychlorinated dibenzofurans, especially when PCB—filled electrical transformers are involved (16). Further, PCB isomers with no chlorine atoms substituted in the ortho. ortho -biphenvl positions are particularly potent as inducers of aryl hydrocarbon hydroxylase activity. The potency of certain dibenzofurans and non-ortho, ortho chlorine substituted PCBs in inducing activity of these enzymes is similar to that of the highly toxic 2,3,7,8-tetrachloro-dibenzo- -dioxin (15. 17., 18). 

Albrecht I. D., Barkovskii A. L., and Adriaens P. (1999) Production and dechlorination of 2,3,7,8-tetrachloro-dibenzo-/)-dioxin (TCDD) in historically-contaminated estuarine sediments. Environ. Set Tecknol. 33, 737-744. 

Exposure of mice to this compound as adults, however, did not significantly alter cellular or humoral immune functions ( ). These results suggest that the developing immune system may be more susceptible to iramunomodulation by chlordane than the adult immune system, and are consistent with earlier studies (, ) demonstrating a greater sensitivity of mice to the effects of 2,3,7,8-tetrachloro-dibenzo- -dioxin (TCDD) on developing than on adult immune systems. 

As shown by several investigations [91], the bromine-rich polybromide phase by itself is hardly flammable and fireextinguishing properties have been reported occasionally. The formation of polybrominated dibenzo-dioxins (PBrDD) and furans (PBrDF) due to the plastic-containing housing of a zinc-flow battery cannot be totally neglected in the case of a fire, but their concentrations are far away from the tetrachloro dibenzodioxine (TCDD) toxic equivalents even in a worst-case scenario. 

Ah-receptor-mediated toxicity is particularly associated with the highly toxic compound 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD), commonly referred to as dioxin. TCDD, and the concept of toxicity equivalency factors (TEFs) based on TCDDs, will be dealt with in Chapter 7. The main point to make at this juncture is that the toxicity of each individual coplanar congener in a mixture can be expressed in terms of a toxic equivalent calculated relative to the toxicity of dioxin. Summation of the toxic equivalents of the individual coplanar PCBs gives a measure of the toxicity of the whole mixture, as expressed through the Ah receptor mechanism. 

Decomposition products were captured in two traps immersed in dry ice followed by a third trap containing 5 ml of benzene. After 1 hour, the boat, tube, and traps were rinsed with benzene. The benzene solution was analyzed by gas chromatography using an electron capture detector to determine the concentration of unreacted 2,3,7,8-tetrachloro-dibenzo-p-dioxin. 

The initial concern for the possible hazard to humans exposed to 2,4,5-T was precipitated by teratologic studies conducted by Bionetics Research Institute under contract from The National Cancer Institute (2). In these studies, large doses of 2,4,5-T were administered to pregnant rats and mice for nine of the 21 days of pregnancy. The incidence of fetal abnormalities was slightly higher in the treated animals than in control animals. Later tests indicated that these abnormalities (cleft palate) may have been caused by 27 8 ppm of 2,3,7,8-tetrachloro-dibenzo-p-dioxin present as a contaminant in the 2,4,5-T sample used in the Bionetic study (3). After the results of the study were made known, the Panel on Herbicides of the President s Science Advisory Committee studied the total 2,4,5-T situation. The report of this committee was published in March, 1971 (4). 

The bleaching process, in contrast, poses major difficulties. Traditional paper bleaching uses chlorine gas, which is reduced to chloride anions, cr, as it oxidizes the colored pigments in wood pulp. The chloride anion is not a pollutant, as it is a major species in the oceans. Unfortunately, chlorine processing also generates small quantities of chlorine-containing dioxins such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin, whose stmcture (below) appears less formidable than its name ... 

Neubert, R., G. Golor, R. Stahlmann, H. Helge, and D. Neubert. 1992. Polyhalogenated dibenzo-p-dioxins and dibenzofurans and the immune system. 4. Effects of multiple-dose treatment with 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) on peripheral lymphocyte subpopulations of a non-human primate (Callithrix jacchus). Arch. Toxicol. 66 250-259. 

Vorderstrasse, B., Dearstyne, E. A., and Kerkvliet, N. I., Influence of 2,3,7,8-tetrachloro-dibenzo-p-dioxin on the antigen-presenting activity of dendritic cells, Toxicol. Sci., 72, 103, 2003. 

House, R., Lauer, L., and Murray, M., Examination of immune parameters and host resistance mechanisms in B6C3F1 mice following adult exposure to 2,3,7,8-tetrachloro-dibenzo-p-dioxin, J. Toxicol. Environ. Health, 31, 203, 1990. 

Chatteijee, A., Onodera, Y., Ebina, T., and Mizukami, F. 2003. 2,3,7,8-tetrachloro dibenzo-p-dioxin can be successfully decomposed over 2 1 dioctahedral smectite—a reactivity index study. J. Mol. Graphics Model. 22 93-104. 

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). 

Walters and Guiseppe-Elle [221] studied the sorption of 2,3,7,8-tetrachloro-dibenzo-p-dioxin to soils from aqueous methanol mixtures and evaluated the applicability of the cosolvent theory to such sorption. Sorption kinetics were influenced by the fraction of methanol in the liquid phase and the soil type. 

Corbet RL, Muir D CG, Webster G RB. 1983. Fate of carbon-14 labelled 1,3,6,8-tetrachloro-dibenzo-p-dioxin in an outdoor aquatic system. Chemosphere 12 (4-5) 523-528. 

Cummings AM, Metcalf JL, Bimbaum L. 1996. Promotion of endometriosis by 2,3,7,8-tetrachloro-dibenzo-p-dioxin in rats and mice Time-dose dependence and species comparison. Toxicol Appl Pharmacol 138 131-139. 

DeCaprio AP, McMartin DM, O Keefe PW, et al. 1986. Subchronic oral toxicity of 2,3,7,8-tetrachloro-dibenzo-p-dioxin in the guinea pig Comparisons with a PCB-containing transformer fluid pyrolysate. Fundam Appl Toxicol 6 454-463. 

Gasiewicz TA, Rucci G. 1991. Alpha-naphthoflavone acts as an antagonist of 2,3,7,8-tetrachloro-dibenzo-p-dioxin by forming an inactive complex with the Ah receptor. Mol Pharmacol 40 607-612. 

Huuskonen H, Undila M, Pohjanvirta R, et al. 1994. Developmental toxicity of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) in the most TCDD-resistant and -susceptible rat strains. Toxicol Appl Pharmacol 124(2) 174-80. 

Lawrence BP, Kerkvliet NI. 1997. Role of altered arachidonic acid metabolism in 2,3,7,8-tetrachloro-dibenzo-p-dioxin-induced immune suppression in C57BI/6 mice. Toxicol Sci 42 13-22. 

Lucier GW, Tritscher A, Goldsworthy T, et al. 1991. Ovarian hormones enhance 2,3,7,8-tetrachloro-dibenzo-p-dioxin-mediated increases in cell proliferation and preneoplastic foci in a two-stage model for rathepatocarcinogenesis. Cancer Res 51 1391-1397. 

Mocarelli P, Needham LL, Marocchi A, et al. 1991. Serum concentrations of 2,3,7,8-tetrachloro-dibenzo-p-dioxin and test results from selected residents of Seveso, Italy. J Toxicol Environ Health 32 357-366. 

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