Agent Orange

Agent Orange is a herbicide and defoliant chemical, one of the 'tactical use' Rainbow Herbicides. It is widely known for its use by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1961 to 1971. It is a mixture of equal parts of two herbicides, 2,4,5-T and 2,4-D. In addition to its damaging environmental effects, traces of dioxin (mainly TCDD, the most toxic of its type) found in the mixture have caused major health problems for many individuals who were exposed. Up to four million people in Vietnam were exposed to the defoliant. The government of Vietnam says as many as 3 million people have suffered illnesses because of Agent Orange. The Red Cross of Vietnam estimates that up to 1 million people are disabled or have health problems as a result of Agent Orange contamination. The United States government has challenged these figures as being unreliable. The U.S. government has documented higher cases of leukemia, Hodgkin's lymphoma, and various kinds of cancer in exposed veterans. Agent Orange also caused enormous environmental damage in Vietnam. Over 3,100,000 hectares (31,000 km2 or 11,969 mi2) of forest were defoliated. Defoliants eroded tree cover and seedling forest stock, making reforestation difficult in numerous areas. Animal species diversity sharply reduced in contrast with unsprayed areas. The aftermath of the use of Agent Orange in Vietnam resulted in massive legal consequences. The United Nations ratified United Nations General Assembly Resolution 31/72 and the Environmental Modification Convention. Lawsuits filed on behalf of both US and Vietnamese veterans sought compensation for damages. Agent Orange was to a lesser extent used outside Vietnam. It was first used by British Armed Forces in Malaysia during the Malayan Emergency. It was also used in neighbouring Laos and Cambodia during the Vietnam War because forests on the border with Vietnam were used by the Viet Cong. Some countries, such as Canada, saw testing, while other countries, such as Brazil, used the herbicide to clear out sections of land for agriculture. The active ingredient of Agent Orange was an equal mixture of two phenoxy herbicides – 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) – in iso-octyl ester form, which contained traces of the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD was a trace (typically 2-3 ppm, but ranging from 50 ppb to 50 ppm), but significant contaminant of Agent Orange. TCDD is the most toxic of the dioxins, and is classified as a human carcinogen by the US Environmental Protection Agency. If not bound chemically to a biological surface such as soil, leaves or grass, Agent Orange dries quickly after spraying and breaks down within hours to days when exposed to sunlight and is no longer harmful. Due to its fat-soluble nature, TCDD enters the body through physical contact or ingestion. Dioxin easily accumulates in the food chain. Dioxin enters the body by attaching to a protein called the aryl hydrocarbon receptor (AhR), a transcription factor. When TCDD binds to AhR, the protein moves to the nucleus, where it influences gene expression.