Tetrachloro-dibenzodioxin

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. 

Zack, J.A. Suskind. R.R. (1980) The mortality experience of workers exposed to tetrachloro-dibenzodioxin in a trichlorophenol process accident.. 7. occup. Med., 22. 11-14... 

Estimate the Kiow values at 25°C of (a) ethylacetate, (b) 2,3,7,8-tetrachloro-dibenzodioxin, (c) the herbicide 2-s-butyl-4,6-dinitrophenol (Dinoseb), (d) the insecticide parathion, and (e) the hormone testosterone using solely the fragment coefficients and correction factors given in Tables 7.4 and 7.5 (Eq. 7-15). 

Kimbrough RD, Carter CD, Liddle JA, et al. 1977. Epidemiology and pathology of a tetrachloro-dibenzodioxin poisoning episode. Arch Environ Health 77-85. 

Mehrle PM, Buckler DR, Little EE, et al. 1988. Toxicity and bioconcentration of 2,3,7,8-tetrachloro-dibenzodioxin and 2,3,7,8-tetrachlorodibenzofuran in rainbow trout. Environ Toxicol Chem 1 47-62. 

Schecter A, Constable JD, Bangert JV, et al. 1989a. Elevated body burdens of 2,3,7,8-tetrachloro-dibenzodioxin in adipose tissue of United States Vietnam veterans. Chemosphere 18 431-438. 

Chlorinated dibenzo-p-dioxines and dibenzofurans are tricyclic aromatic compounds [4], characterized by a high chemical resistance and an ability to be accumulated in the nutritional chain. Some of them are extremely toxic, teratogenic, mutagenic and probably also carcinogenic. The most studied substances in this group are 2,3,7,8-tetrachloro-dibenzodioxine (TCDD) and 2,3,7,8-tetrachloro-dibenzofuran (TCDF), which are among the most toxic substances... 

EPA recently published a Proposed Significant New Use Rule, which if finalized as proposed, could require the notification to EPA for products produced from chloranil, particularly if those products are produced from chloranil containing more than 20 ppb incidented dioxin and furan concentrations measured as Tetrachloro Dibenzodioxin Threshold Equivalency Quotient (TEQ). 

Safe, S. (1995). Modulation of gene expression and endoerine response pathways by 3,4,7,8-tetrachloro-/>-dibenzodioxin and related compounds. Pharmacology Therapeutics, 67, 247-281. 

Dibenzo[6,e][l,4]dioxin, 2-nitro-bromination, 3, 974 cleavage reactions, 3, 973 Dibenzo[b,e][l,4]dioxin, 2,3,7,8-tetrachloro-synthesis, 3, 985 toxicity, 3, 992 Dibenzodioxins... 

Dioxins are prominent members of the class of polychlorinated hydrocarbons that also includes diben-zofuran, biphenyls and others. Dioxins are highly toxic environmental contaminants. Like others small planar xenobiotics, some dioxins bind with high affinity to the arylhydrocarbon (Ah) receptor. Dioxins activate the receptor over a long time period, but are themselves poor substrates for the enzymes which are induced via the Ah-receptor. These properties of the dioxins and related xenobiotics may be important for the toxicity of these compounds. Dioxins like 2,3,7,8-tetrachloro-p-dibenzodioxin can cause persistent dermatosis, like chloracne and may have other neurotoxic, immunotoxic and carcinogenic effects. 

For some toxins it is possible to demonstrate an apparent improvement in functional response at levels of exposure which are below a threshold. This effect, which has been termed hormesis , is most effectively demonstrated in the consistently improved longevity of animals whose caloric intake is restricted rather than allowing them to feed ad lib (Tannenbaum, 1942). Clearly in this instance, the observed effects are the result of exposure to a complex mixture of chemicals whose metabolism determines the total amount of energy available to the organism. But it is also possible to show similar effects when single chemicals such as alcohol (Maclure, 1993), or caffeic acid (Lutz et al., 1997) are administered, as well as for more toxic chemicals such as arsenic (Pisciotto and Graziano, 1980) or even tetrachloro-p-dibenzodioxin (TCDD) ( Huff et al., 1994) when administered at very low doses. It is possible that there are toxins that effect a modest, reversible disruption in homeostasis which results in an over-compensation, and that this is the mechanism of the beneficial effect observed. These effects would not be observed in the animal bioassays since to show them it would be necessary to have at least three dose groups below the NOAEL. In addition, the strain of animal used would have to have a very low incidence of disease to show any effect. 

Chlorinated dioxins occur in atmospheric deposition (Koester and Hites 1992), and will thereby enter the terrestrial environment and watercourses. The degradation of tetrachloro- through octa-chlorodibenzo[l,4]dioxins has been examined in low-nitrogen medium by Phanerochaete sor-dida YK-624 (Takada et al. 1996). All the compounds were extensively degraded, and the ring fission of 2,3,7,8-tetra- and octachlorodibenzo[l,4]dioxin produced 4,5-di- and tetrachlorocatechol. These results established important evidence for the biodegradability of even highly chlorinated dibenzodioxins. 

Chlorinated dibenzo-p-dioxins and dibenzofurans are among the most toxic substances known, especially 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD). These extremely hazardous compounds can be produced from 3,4,5- and 2,4,5-trichlorophenols by peroxidases [207]. However, the biological formation of such toxicants in nature or by microorganisms has not been described. 

Fig. 5.2 Dose-response curve for 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD) in the CALUX bioassay. The concentration (expressed as TCDD) can subsequently be determined by comparing the response obtained with a sample extract with the calibration...

For low volatility components such as polychlorobiphenyls or tetrachloro-para-dibenzodioxins (TCDD), it is possible to make use of a solvent effect in order to perform on-column enrichments. Thus, Poy [ 14 ] injected 4 times 2 pi of a sample containing TCDD isomers without destroying the separation performance. The low boiling components were stron y retained in the thick solvent layer formed when the solvent recondensed so that all 4 injections refocused in the column inlet before the chromatographic process took place. 

A family of over 200 substances, two of which are particularly important from a toxicological viewpoint 2,3,7,8-tetrachloro-p-dibenzodioxin (2378-TCDD) and 2,3,7,8-tetrachlorodibenzofuran(2378-TCDF). 

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