TCDD 2,4,7,8-tetrachlorodibenzo

Abbreviations PAH = polyaromatic hydrocarbon, TCDD = Tetrachlorodibenzo-p-dioxin, PCB = polychlorinated biphenyl, PBB = polybrominated biphenyl, TBTO = tributyltin oxide, DBTO = dibutyltin oxide, TPT = triphenyltin. 

CDDs a chlorinated dibenzo-p-dioxins CDFs = chlorinated dibenzofurans PCBs = polychlorinated biphenyls TCDD = tetrachlorodibenzo-p-dioxin... 

CDDs = chlorinated dibenzo-p-dioxins CDFs = chlorinated dibenzofurons EPA = Environmental Protection Agency FIpCDD = heptachlorodibenzo-p-dioxin HpCDF = heptachlorodibenzofuran FIxCDD = hexachlorodibenzo-p-dioxin FIxCDF = hexachlorodibenzofuran NA = not applicable PeCDD = pentachlorodibenzo-p-dioxin PeCDF = pentachlorodibenzofuran TCDD = tetrachlorodibenzo-p-dioxin TCDF = tetrachlorodibenzofuran TEQ=Toxicity equivalency concentration... 

ACE, angiotensin converting enzyme AGD, anogenital distance DES, diethylstilbestrol IUGR, intrauterine growth restriction PBBs, polybrominated biphenyls PCBs, polychlorinated biphenyls T3, triiodothyronine T4, thyroxine TCDD, tetrachlorodibenzo-p-dioxin Th1, T helper 1 Th2, T helper 2... 

Fig. 9. Relationship between the steady-state bioconcentration factors on a lipid basis (BCFl) of chemicals in different fish species and the n-octanol/water partition coefficient (Kqw) (log/log scale). ( ) Solid circles are chemicals with known endocrine-disrupting properties. Abbreviations of the chemicals p,p -DDT 2,2-bis-(p-chlorophenyl)-l,l,l-trichloroethane. OCDD octachlorodibenzo-p-dioxin. TCDD tetrachlorodibenzo-p-dioxin. HCB hexachloro-benzene. PCA pentachloroanisole. PeCB pentachlorobenzene. MX musk xylene. TeCB tetrachlorobenzene. NP nonylphenol. TCB tetrachlorobenzene. y-HCH y-hexachlorocyclo-hexane (Lindane). PCP pentachlorophenol. DCB dichlorobenzene. BPA bisphenol-A. PCBs polychlorinated biphenyls...

TCDD—tetrachlorodibenzo-p-dioxins TCDF—tetrachlorodibenzofurans PeCDD—pentachlorodibenzo-p-dioxins PeCDF—pentachlorodibenzofurans HxCDD—hexachlorodibenzo-p-dioxins HxCDF—hexachlorodibenzofurans... 

Limits of detection for the various classes of herbicide vary from 0 01 to about 5 mg/kg. Some claims for TCDD (tetrachlorodibenzo-p-dioxin) are made at the parts per million million level in the literature, e.g. for fish, milk and beef fat for GLC with mass... 

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). 

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... 

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... 

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). 

TAetection of the highly potent impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), necessitated an environmental assessment of the impact of this contaminate. Information was rapidly needed on movement, persistence, and plant uptake to determine whether low concentrations reaching plants, soils, and water posed any threat to man and his environment. Because of the extreme toxicity of TCDD, utmost precautions were taken to reduce or minimize the risk of exposure to laboratory personnel. Synthesis of uniformly labeled C-TCDD by Muelder and Shadoff (I) greatly facilitated TCDD detection in soil and plant experiments. For unlabeled experiments it seemed wise to use only small quantities of diluted solutions in situations where decontamination was feasible and to rely on the sensitivity afforded by electron capture gas chromatography... 

Tetrachlorodibenzo-p-dioxin (TCDD) is a contaminant in 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) which may occur in the manufacturing process. Before 1971 some samples of 2,4,5-T contained from 2-50 ppm TCDD (i) in the technical acid. Highest concentrations of TCDD occurred before 1968. 

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