2,4,7,8-Tetrachlorodibenzo

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). 

Structure— Function Relationships. Since PCBs and related HAHs are found in the environment as complex mixtures of isomers and congeners, any meaninghil risk and hazard assessment of these mixtures must consider the quaUtative and quantitative stmcture—function relationships. Several studies have investigated the stmcture—activity relationships for PCBs that exhibit 2,3,7,8-tetrachlorodibenzo-p-dioxin [1746-01-6] (1)... 

NB There is also conclusive evidence that this agent (tamoxifen) reduces the risk of contralateral breast cancer) 2,3,7,8-Tetrachlorodibenzo-para-dioxin [1746-01-6] (Vol. 69 1997)... 

There are even receptors that are known to become activated only due to interaction with a synthetic chemical, and no physiological agonist for such a receptor has been characterized. A model receptor in this class is the so-called Ah receptor complex that becomes activated subsequent to its exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxiu (TCDD). Activation of the. Ah receptor... 

Moses, M., and Prioleau, P. Ct. (1985). Cutaneous histologic findings in chemical workers with and without chloracne with past exposure to 2,3,7,8-tetrachlorodibenzo-/i-d oxin. i.. 4m. Acad. Dermatol. 12, 497-506. 

Organohalogen compounds are of serious concern also as contaminants. The most feared material in this category is dioxin (2,3,7,8-tetrachlorodibenzo-para-dioxin, TCDD) that has already caused several catastrophes and has even been detected in effluent and sludge from paper mills that use chlorine bleach and also in... 

Eernandez-Salguero, P.M., Hilbert, D.M., Rudikoff, S. et al. (1996). Aryl-hydrocarbon receptor-deficient mice are resistant to 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced toxicity. Toxicology and Applied Pharmacology 140, 173-179. 

The Preparation of Uniformly Labeled C-2,7-Dichlorodibenzo- -dioxin and C-2,3,7,8-Tetrachlorodibenzo- -dioxin... 

Table III. Assay of 2,3,7,8-Tetrachlorodibenzo-/F-dioxin- C by Mass Spectroscopy...

Tetrachlorodibenzo- -dioxm- C, U.L. 2,7-Dichlorodibenzo-p-dioxin- C, U.L. (0.500 gram) was stirred with 10 ml of chloroform containing trace amounts of FeCls and L and heated to reflux temperature while chlorine gas was passed into the mixture for 18 hours. After cooling, the white insoluble product was collected by filtration and triturated with 15 ml of boiling chloroform. The insoluble portion was transferred to a sublimation flask where it was vacuum-sublimed at 140 °C. The sublimate was recrystallized from 2.5 ml of anisole and washed with chloroform. The product weighed 0.229 gram and contained 2.9 /xCi of radioactivity per mg. 

Figure 11. ESR spectrum of 1,2,3,4-tetrachlorodibenzo-p-dioxin in TFMS acid after UV irradiation...

Three isomeric tetrachlorodibenzo-p-dioxins were studied. All were insoluble in TFMS acid. To dissolve these compounds and form cation radicals, UV irradiation was necessary. The 1,2,3,4-tetrachloro compound was particularly sensitive to UV irradiation, and as a solid, even turned pink when exposed to ordinary fluorescent light. When subjected to constant UV irradiation, radical ions were induced rapidly. The change in the cation radical concentration was monitored by the ESR signal as illustrated in Figure 10. To determine whether the tetrachloro isomer had been converted to lower chlorinated derivatives after UV irradiation, the dissolved dioxin was then poured into ice water and recovered. The GLC retention time of the recovered dioxin was unchanged in addition, no new GLC peaks were observed. Moreover, the ESR spectrum see Figure 11) for the recovered material was not altered between widely... 

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

Variations in the manufacturing process of 2,4,5-trichloro- and pentachlorophenol (but not 2,4-dichlorophenol) have sometimes resulted in contamination of the product by small amounts of heterocyclic impurities (4,5). Of these, the chlorinated dibenzo-p-dioxins such as TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) have received much scientific and public attention because of their real or potential toxicity 6, 7), [Chick edema factor, a curious toxicological problem to poultry producers for several years, has been shown to be composed of chlorodibenzo-p-dioxins (8).]... 

Tetrachlorodibenzo-p-dioxin (TCDD) (I), an occasional contaminant in 2,4,5-T and other trichlorophenol derivatives, is the most toxic of the commonly-encountered dioxins (8) and it received most of our attention. Its low solubility in common solvents and water (ca. 2 ppb) limited our experiments since the products were difficult to identify by the conventional techniques of organic chemistry. However, TCDD has an absorption maximum at 307 nm in methanol—well within the solar spectrum observed at the earth s surface and near the region of maximum intensity (310-330 nm) of the UV lamps used in previous experiments (H 29). 

Oevere toxicological responses have been associated with certain chloro- dibenzodioxins. One of these responses is chloracne, a folliculosis first associated with skin contamination by chlorohydrocarbons in 1899 (3). Serious outbreaks of chloracne-like lesions associated with runaway reactions in the production of 2,4,5-trichlorophenol occurred in Germany in the early 1950 s (5). 2,4,5-Trichlorophenol itself does not cause acne (S), but the contaminants which may be formed in the uncontrolled production of 2,4,5-trichlorophenol are extremely potent acnegens (5). 2,3,7,8-Tetrachlorodibenzo-p-dioxin and tri- and tetra-... 

Acute Lethality. Samples of 2,7-dichlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin, hexachlorodibenzo-p-dioxin, and octachloro-dibenzo-p-dioxin were evaluated for acute oral lethality in the following animals. 

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