|Molar mass||255.48 g·mol−1|
|Appearance||Off-white to yellow crystalline solid|
|Density||1.80 g/cm3, 20 °C|
|Melting point||154 to 158 °C (309 to 316 °F; 427 to 431 K)|
|238 mg/kg (30 °C)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
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.[medical citation needed] 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 The international trade of 2,4,5-T is restricted by the Rotterdam Convention. 2,4,5-T has since largely been replaced by dicamba and triclopyr.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.[medical citation needed] IARC considers the chlorophenoxyacetic acids group of chemicals as possibly carcinogenic to humans.
||This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. (February 2011)|
- Pamela Sodhy (1991). The US-Malaysian nexus: Themes in superpower-small state relations. Institute of Strategic and International Studies, Malaysia. pp. 284–290.
- CDC, Biomonitoring Summary
- Tschirley FH. Defoliation in Vietnam. Science. 1969;163:779-786.
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- 2,4,5-T - Identification, toxicity, use, water pollution potential, ecological toxicity and regulatory information
- CDC - NIOSH Pocket Guide to Chemical Hazards