Dioxins/TCDD herbicide contaminants

Tetrachlorodibenzo[b,e][l,4]dioxin (TCDD), a contaminant of the defoliant and herbicide Agent Orange Mustard gas, l,l -thiobis[2-chloroethane]... 

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... 

Synonyms AIDS-105033 BRN 0271116 C-07557 CCRIS 576 Dioxin Dioxin (herbicide contaminant) Dioxine EINECS 217-122-7 NCI-C03714 TCDBD 2,3,7,8-TCDD 2,3,7,8-Tetra-chlorodibenzodioxin 2,3,7,8-Tetrachlorodibenzo[7>,e][l,4]dioxin 2,3,7,8-Tetrachlorodibenzo-1,4-dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin Tetradioxin. 

Dioxin (herbicide contaminant), see TCDD Dioxine, see TCDD p-Dioxobenzene, see Hydroquinone... 

Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin TCDD) is among the most toxic compounds known today. It is an airborne contaminant from an incineration process, which has been described in Section 3.3.2. Dioxin also frequently occurs as an impurity in the herbicide 2,4,5-T. Accordingly, when the herbicide 2,4,5-T is applied to crops, dioxin is also released to the soil. Any spills of dioxin also cause soil contamination. It may be removed by extraction with coconut-activated carbon. Its half-life in soil is about one year. 

Uses. Formerly used as an herbicide in brush control. Production was terminated in the United States in 1979 when the Environmental Protection Agency, in an emergency action, suspended all uses because of contamination with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In October 1983, all registrations for use of 2,4,5-trichlorophenoxy-acetic acid (2,4,5-T) were cancelled by the US Department of Agriculture because of concerns over the potential of dioxin contami-... 

The synthesis of other chlorinated chemicals such as the herbicide 2,4,5-T also produce dioxins, including TCDD, as contaminants (see pp. 106-7 above). 

Trichlorophenols are generally poisons and may be carcinogens. They may contain 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a contaminant. Some trichlorophenols are used as herbicides (e.g., 2,4,5-T and silvex). Human exposure may cause chloracne, liver dysfuncdon, muscle weakness, and prophyria. 

SYNS 2,3,7,8-czTEROCHLORODVc UBENZo-p-DWUOKSYNY (POLISH) DIOKSYNY (POLISH) DIOXIN (herbicide contaminant) DIOXINE NCI-C03714 TCDBD 2,3,7,8-TCDD 2,3,6,7-TETRACHLORODI-BENZO-p-DIOXIN 2,3,7,8-TETRACHLORODlBENZO-(b,e)(l,4)DIOXAN 2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN 2,3,7,8-TETRACHLORODIBENZO-l,4-DIOXIN TETRADIOXIN... 

Chlorophenoxy herbicides are, by themselves, of relative low toxicity to humans. They are, however, often contaminated with dioxins, of which, 2,3,7,8-tetrachloro-p-dioxin (TCDD) is the most toxic, which cause CNS and peripheral nervous system neuropathies. l8l... 

The most toxic member of the dioxin family is 2,3,7,8-TCDD. Agent Orange is an approximately 1 1 mixture of two herbicides—2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid. Dioxin TCDD was present as a contaminant in Agent Orange used as a defoliant in the Vietnam War. 

After TCDD (dioxin) had been found to be a contaminant in the herbicide 2,4,5-T and was tested as a teratogen in rats in 1968, the herbicide was outlawed by the EPA on most food crops. A complete discussion of this chemical and its history is given in Chapter 22, Section 4.1. 

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