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Agent Orange: An Overview

Written December 2015, edited May 2019

The term “Agent Orange” has been in and out of news media since the 1960s. Most stories featuring this chemical defoliant have focused on the medical impact of its use in Southeast Asia on the American veterans who came in contact with it. In more recent years, focus has shifted to children born to those veterans as well as the Vietnamese civilians whose children are affected by the lasting remnants of the herbicides. Due to this media coverage, Agent Orange is a term recognized by many. But there are few who understand what the term encompasses and exactly how and why it continues to impact people today, 48 years after the US Air Force conducted the last spraying mission in Vietnam.


Aerial herbicide spray missions in southern Vietnam, 1965 to 1971 (Source: U.S. Department of the Army)

What is a chemical defoliant? What is a herbicide?

A defoliant is a chemical compound sprayed or dusted onto plants meant to destroy the leaves.

A herbicide is a chemical compound distributed over unwanted plant life to kill the plants entirely.

Why use defoliants and herbicides in war?

  • To deprive the enemy of natural cover and food sources (offensive measure)

  • To clear perimeter areas around long standing bases or roads to provide greater line of sight (defensive measure)

Was there debate in using herbicides?


The Geneva Protocol of 1925 states that “ the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices, has been justly condemned by the general opinion of the civilised world”.

The history of using herbicides by the British in the 1950s against communists in Malaya helped the United States in its decision to use herbicides in Vietnam. To avoid the issue of the Geneva Protocol, the British simply denied the Malayan Emergency was a war, instead stating that it was an internal matter.

The United States (which did not ratify the Geneva Protocol until 1975) claimed that the use of herbicides in Vietnam was not meant to directly kill the enemy. Other arguments stated that such chemical based materials, namely tear gas and herbicides, should not be banned from warfare when there is a common domestic peace time use for them.

Why the name “Agent Orange”?

The herbicides used in Vietnam were named for the different color bands around the barrels they were stored in.

The term “Agent Orange” has become a catchall phrase for the herbicides used in Vietnam as it was used most extensively.

How many herbicides were used in Vietnam?



Agents Pink, Green, Purple, Orange, White, and Blue

Who produced the herbicides?

Several companies were contracted by the government to produce the herbicides, including but not limited to the Dow Chemical Company and Monsanto.

How were the herbicides distributed?

95% of the herbicides used in Vietnam were sprayed during Operation Ranch Hand from US Air Force aircraft specially modified for the job. This included the UC-123B variant of the Fairchild C-123 Provider. The remaining 5% was sprayed by US Army, US Navy and Republic of Vietnam forces through the use of hand sprayers, spray trucks, helicopters, and boats.

Methods of Defoliation

What chemicals were the herbicides composed of?

Most commonly:

  • 2,4-dichlorophenoxyacetic acid (2,4-D)

  • 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)

What makes these herbicides so harmful to humans?

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was found to be a contaminant in the 2,4,5-T used in the herbicides. Commonly referred to simply as “dioxin”, TCDD is human carcinogen. The lasting effects on the Vietnamese population have largely to do with the rate of decay for TCDD, which is still present in the soil and sediment. Basically insoluble in water, TCDD is able to continue existing, as well as be transported by water. Much human exposure is now suffered by eating animals like fish and birds that feed in dioxin heavy areas, or “hot spots”, and become contaminated with the toxin.

Do the herbicides have any lasting environmental effects?


Thousands of square miles of land were sprayed with defoliants and herbicides. Agent Orange and other herbicides used destroyed forests that developed into the complex, varied, and balanced ecosystems that they were over centuries. It will take centuries again to regain that same balanced complexity.

Additionally, in some areas where the original plant life was damaged,  more aggressive species like bamboo grew there rapidly which further slows, or even stops, the regeneration of the original forest.

Effects of Defoliation


Additional Reading


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