About Agent Orange

Why Agent Orange?

From 1961 to 1971, the U.S. government sprayed 20 million gallons of herbicides and defoliants, 12 million of which were Dioxin-contaminated Agent Orange, over Vietnam, large areas of Laos and parts of Cambodia.

Operation Ranch Hand

U.S. Air Force C-123 aircrafts flew 20,000 missions that sprayed the herbicides, as part of a defoliation program called “Operation Ranch Hand.” During the time of the war, dipterocarp forests, plantations, mangroves, brush lands, and other woody vegetation constituted about 25 million acres of dense tropical forests in South Vietnam, an area approximately the size of the state of Kentucky. The program’s official objective was to denude this tropical-agricultural landscape, which provided cover and subsistence for counterinsurgency forces, with tactical code-named “Rainbow herbicides.”

Of the herbicides used in this U.S.-led ecocidal war were Agents Orange, Purple, Pink and Green, containing varying concentrations of the phenoxy chemical 2,4,5-T contaminated with Dioxin. The toxicity of Agent Orange, above the others, was attributed to its equal mixture of Dioxin-contaminated 2,4,5-T and another phenoxy chemical 2,4-D. Other herbicides included Agent White, a mixture of 2,4-D and picloram, and Agent Blue, an arsenical herbicide used against rice crops that consisted of sodium cacodylate and cadodylic acid. Much of the herbicides used were up to 50 times the concentration recommended for killing plants.

Fitted with specially developed spray tanks with a capacity of 1,000 gallons of herbicides, C-123s were able to spray an 8.5-mile swath of land with these chemical herbicides in less than five minutes. A smaller portion of the spraying efforts had also been conducted by on-ground combatants by hand and by way of trucks out of U.S. military installations by the U.S. Army Chemical Corps and other allied forces.

U.S. Objectives in Viet Nam

When U.S. President John F. Kennedy came into office in January 1961 the question of what to do with Vietnam was answered. By May of that same year—the Cold War inevitably becoming the lens through which U.S. foreign policy was interpreted—President Kennedy reached a decision on U.S. objectives in Vietnam. The U.S. would “prevent communist domination of South Vietnam,” a now-declassified White House memorandum read, “to create a viable and increasingly democratic society, and to initiate, on an accelerated basis, a series of mutually supporting actions of a military, political, economic, psychological, and covert character to achieve this objective.”

The U.S. shortly established the Combat Development and Test Center in Saigon, to identify new counterinsurgency techniques, along with the development of tactical weapons, against the North Vietnam Army and pro-Independence forces in the south. Among what was determined to be prime competitive advantages of these enemies was subsistence living under the cover of the thick jungle canopy, and so an herbicide powerful enough to clear this tropical-agricultural landscape was quickly becoming appealing.

Within months, in August 1961, after the Dinoxil herbicide reached the shores of South Vietnam, defoliation testing began in Kontom Province.

The defoliation program started out small and nearly ended before it began as the efficacy of herbicide spraying had been questioned by the Department of Defense, the State Department and the South Vietnamese government. Washington was also wary about a public backlash, both domestically and around the world, and that the program would be co-opted by the North Vietnamese as an anti-American propaganda tool. But President Kennedy was not swayed, agreeing instead with then-U.S. Secretary of Defense Roswell Gilpatric that the U.S. should “participate in a selective and carefully controlled joint program of defoliant operations in Vietnam starting with the clearance of key routes and proceed thereafter to food denial.”

President Kennedy also found that the use of herbicides did not violate “any rule of international law concerning the conduct of chemical warfare,” a precedent “established by the British during the emergency in Malaya.” The official stance at the time was that the use of herbicides, which did not target human populations, was akin only to its agricultural use. Little was known at the time about the byproduct of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), also known as Dioxin, that occurred during the industrial manufacturing of the herbicides and the extent of subsequent Dioxin contamination.

On January 13, 1962, the first official Operation Ranch Hand mission flew over National Route 15, which stretched from the port of Vũng Tàu to Bien Hoa Air Base. As the American involvement in Vietnam escalated, so too did the use of herbicides. Operation Ranch Hand in Vietnam expanded to include large areas of south-eastern Laos, in December 1965, and reached its peak by 1967 when over 1.5 million acres were sprayed.

“If we think they’re winning, you can imagine what they think.”
– President Lyndon Johnson, in a telephone conversation with Senator Mike Mansfield, 1965

The Apparent End

While opposition to the defoliation program existed from the very beginning, it did not grow in strength until 1967 when a petition was submitted to the White House by the Federation of American Scientists—with more than 5,000 signatures of renowned scientists, 17 Nobel Laureates and 129 members of the National Academy of Sciences. The U.S. scientific community continued to raise concerns about the ecological and human impacts of the herbicides and conducted field investigations in Vietnam under the auspices of the American Association for the Advancement of Science.

Even Senator Robert Kennedy famously warned: “At the end of it all, they may say, as Tacitus said of Rome: ‘They made a desert, and called it peace.’”

In 1969 a study found that Dioxin-contaminated 2,4,5-T caused birth defects in mice at high doses. A follow-up study a year later found what the chemical companies already knew, that the 2,4,5-T herbicidal component in the 12 million gallons of Agent Orange was contaminated with 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), that is, Dioxin. These findings led to the U.S. decision to restrict the use of Agent Orange altogether, though the U.S. EPA did not formally ban the use of 2,4,5-T until 1979. Later studies eventually found that Dioxin also causes adverse health effects and birth outcomes in humans. In 1997, the International Agency for Research on Cancer (IARC) of the World Health Organization, classified TCDD as a “known human carcinogen.”

The last defoliation mission using Agent Orange took place in April 1970. But its use for perimeter spraying of U.S. military bases continued for the next six months. The Air Force flew its last official crop spraying mission using Agent Blue on January 7, 1971, though the South Vietnamese forces continued spraying the remaining stocks of Agents Blue and White until 1972.

In September 1971, the surplus inventories of tactical Agent Orange, including those under the control of the Armed Forces of South Vietnam, were re-barreled as part of the operation code-named “Pacer IVY,” at Da Nang, Bien Hoa and Tuy Hoa airbases. The barrels were then shipped to Johnston’s Island in the South Pacific until it could be determined how they would be disposed of. The 860,000 gallons of surplus Agent Orange in the U.S. were shipped to the Seabees base in Gulfport, Mississippi, where it was stored until 1977. About 2.3  million gallons of Agent Orange from Gulfport and Johnston Island were incinerated in the South Pacific Ocean on the Vulcanus, as part of “Operation Pacer Ho.”

“Operation Ranch Hand” became a footnote in most accounts of the war in Vietnam, but its widespread use of Agent Orange and other herbicides, its toxic legacies, are still felt today.


Inside the Barrels: Agent Orange, Blue and White

Video Map of Spraying of Herbicides 1963-70. Developed by Jeanne Stellman.

Veterans and Agent Orange

Veterans and Agent Orange

National Academies of Sciences, Engineering, and Medicine. 2018. Veterans and Agent Orange: Update 11 (2018). Washington, DC: The National Academies Press.