2,4,5-Trichlorophenoxyacetic acid

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2,4,5-Trichlorophenoxyacetic acid
2,4,5-Trichlorophenoxyacetic acid
Ball-and-stick model of 2,4,5-T
Identifiers
CAS number 93-76-5 YesY
ChemSpider 1435 YesY
UNII 9Q963S4YMX YesY
KEGG C07100 YesY
ChEBI CHEBI:27903 YesY
ChEMBL CHEMBL194458 YesY
RTECS number AJ8400000
Jmol-3D images Image 1
Properties
Molecular formula C8H5Cl3O3
Molar mass 255.48 g mol−1
Appearance Off-white to yellow crystalline solid
Density 1.80 g/cm³, 20 °C
Melting point 154-158 °C
Solubility in water 238 mg/kg (30 °C)
Hazards
R-phrases 22-36/37/38-50/53
S-phrases 24-60-61
Related compounds
Related compounds 2,4-D
auxin
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

2,4,5-Trichlorophenoxyacetic acid (also known as 2,4,5-T), a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants. It was developed in the late 1940s and was widely used in the agricultural industry until being phased out, starting in the late 1970s due to toxicity concerns. Agent Orange, a defoliant used by the British in the Malayan Emergency and the U.S. in the Vietnam War, was equal parts 2,4,5-T and 2,4-D (2,4-dichlorophenoxyacetic acid). 2,4,5-T itself is toxic with a NOAEL of 3 mg/kg/day and a LOAEL of 10 mg/kg/day.[1] Additionally, the manufacturing process for 2,4,5-T contaminates this chemical with trace amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a carcinogenic persistent organic pollutant with long-term effects on the environment. With proper temperature control during production of 2,4,5-T, TCDD levels can be held to about .005 ppm. Before the TCDD risk was well-understood, early production facilities lacked proper temperature controls and individual batches tested later were found to have as much as 60 ppm of TCDD.

In 1970, the United States Department of Agriculture halted the use of 2,4,5-T on all food crops except rice, and in 1985, the EPA terminated all remaining uses in the U.S. of this herbicide. The international trade of 2,4,5-T is restricted by the Rotterdam Convention. 2,4,5-T has since largely been replaced by dicamba and triclopyr.

Apart from agricultural uses, 2,4,5-T was also a major ingredient in Agent Orange, a herbicide blend used by the British military in Malaya and the U.S. military in Vietnam between January 1965 and April 1970 as a defoliant.

Human health effects from 2,4,5-T at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Intentional overdoses and unintentional high dose occupational exposures to chlorophenoxy acid herbicides have resulted in weakness, headache, dizziness, nausea, abdominal pain, myotonia, hypotension, renal and hepatic injury, and delayed neuropathy. IARC considers the chlorophenoxyacetic acids group of chemicals as possibly carcinogenic to humans.[2]

References[edit]

  1. ^ Pamela Sodhy (1991). The US-Malaysian nexus: Themes in superpower-small state relations. Institute of Strategic and International Studies, Malaysia. pp. 284–290. 
  2. ^ CDC, Biomonitoring Summary 

2. Tschirley FH. Defoliation in Vietnam. Science. 1969;163:779-786.

3. Orians GH, Pfeiffer EW. Ecological effects of the war in Vietnam. Science. 1970;168:544-554.

4. Neilands JB, Orians GH, Pfeiffer EW, Vennema A, Westing AH. Harvest of Death: Chemical Warfare in Vietnam and Cambodia. New York: Free Press; 1972.

5. Gochfeld M. The other victims of the Vietnam war. BioScience. 1975;25:540-541.

6. Westing AH, ed. Herbicides in War. The Long Term Ecological and Human Consequences. London: Taylor and Francis; 1984.

7. Schecter AJ, Tong HY, Monson SJ, Goss ML. Levels of 2,3,7,8-TCDD in silt samples collected between 1985-86 from rivers in the North and South of Vietnam. Chemosphere. 1989;19:547-550.

8. Schecter AJM, Dai LC, Thuy LTB, et al. Agent Orange and the Vietnamese: the persistence of elevated dioxin levels in human tissues. Am J Public Health. 1995;85:516-522.

9. Kahn PC, Gochfeld M, Nyugen M, Hansson M, Rappe C, Velez H. Dioxins and dibenzofurans in blood and adipose tissue of Agent Orange-exposed Vietnam veterans and matched controls. JAMA. 1988;259:1661-1667.

10. Fingerhut MA, Halperin WE, Marlow DA, et al. Cancer mortality in workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin. N Engl J Med. 1991;324:212-218.


External links[edit]