About Agent Orange

What is Dioxin?

Vuktor Yushchenko, Ukrainian presidential candidate, poisoned by Dioxin, photographed in 2004.

Often when Agent Orange is invoked, it actually refers to Dioxin, specifically the toxic contaminant 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) found in the phenoxy chemical 2,4,5-T, one of two components of Agent Orange.

Dioxin originated as an unintended byproduct in the deliberately accelerated manufacture of 2,4,5-T for use in the U.S. war efforts in Vietnam, Laos and Cambodia. 

Dioxin, or 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), is the most toxic of all the Dioxins and Dioxin-like compounds. The Dioxin-contaminated 2,4,5-T component, found not only in Agent Orange but also in Agents Pink, Purple and Green, was later discovered to alter the expression  of specific genes in humans. 

Some key facts:

  • Dioxin is a member of the class of persistent organic pollutants that is produced through combustion, in the bleaching of paper and pulp or in the chemical manufacturing process. 
  • 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), in particular, was a byproduct of the deliberately accelerated production of the phenoxy herbicide 2,4,5-T. Agent Orange was an equal mixture of 2,4,5-T and the other phenoxy herbicide 2,4-D.
  • 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), or Dioxin, is the most toxic of all the Dioxins and Dioxin-like compounds. 
  • The U.S. National Toxicology Program (NTP) and the International Agency for the Research on Cancer list TCDD as a “known human carcinogen.”
  • Dioxin has been found to be an endocrine disruptor that can cause chloracne, certain cancers, and reproductive and developmental effects (at least in animals).
  • ​Dioxin is not absorbed by most plants nor is it water soluble. Only zucchini species and water locusts, so far, have been found to absorb Dioxin.
  • Dioxin can attach to fine soil particles or sediment, which are then carried by water downstream and settle in the bottoms of ponds and lakes where it can accumulate in the food chain.
  • The half-life of Dioxin varies depending on where it is found. In humans the half-life is between 7 and 11years; in surface soil that has been fully exposed to sunlight it’s between 1 and 3 years; and in subsurface soils and sediment it can be more than 100 years.
  • Nations around the world have signed on to the Stockholm Convention on Persistent Organic Pollutants (POPs) and committed to reducing their inventory of Dioxins in their countries and eliminating their production.

Agent Orange

Agent Orange, also known as Herbicide Orange, was one of the many color-coded herbicides of the tactical “Rainbow Herbicides” that U.S. forces sprayed over Vietnam, Laos and Cambodia during the war. The herbicides were deployed by the U.S. Air Force as part of the defoliation program code-named Operation Ranch Hand, to denude the tropical landscape and destroy croplands over large areas that provided cover and subsistence for counterinsurgency forces. 

Production of Agent Orange and its military use ended in 1970, and existing stocks were subsequently destroyed after Operation Ranch Hand in 1971. Production of 2,4,5-T for domestic use continued until it was halted in the 1980s. In most countries, 2,4-D is still produced by Dow Agroscience and is a common component of over 70 products, including Scott’s Weed and Feed, Miracle-Gro Shake ‘n Feed and Weed B Gone, among many others.

Agent Orange degraded large swaths of land in Vietnam, Laos and Cambodia, making those areas no longer ecologically tenable. Pre-war conditions of Vietnam’s forests, which included an ecologically balanced mixture of large numbers of species of flora and fauna, took hundreds of years to reach. It will take many more centuries of natural regeneration to reproduce the pre-war tropical and topographical conditions and to recover from mass erosion, among other geomorphic processes, that occurred as a result of systematic defoliation. The altered features to the land by the wartime uses of herbicides not only lowered soil nutrient levels but also introduced invasive plant species.

“A few grains of salt dissolved in an olympic-size swimming pool.”

– Philip Jones Griffiths, “Agent Orange:
Collateral Damage in Viet Nam,” 2004.

The level of TCDD in human blood in industrialized nations has been decreasing since the 1970s. Studies have found that by the late 1990s TCDD levels in the blood of those tested had dropped from a high of nearly 20 parts per trillion to between 2 and 5 ppt. But populations directly exposed to TCDD have been found to have higher levels in their blood. This includes veterans who directly handled the contaminated chemicals during Operation Ranch Hand, whose body burden of Dioxins when tested in 1999, more than 20 years after they served in Vietnam, ranged from less than 6 ppt to over 130 ppt. Studies conducted in Vietnam in the last decade found high levels of dioxin in the blood of those who ate fish or duck from the ponds at the Bien Hoa or Da Nang air bases where Ranch Hand was based during the war.

Scientists are still trying to understand how Dioxin causes reproductive and developmental abnormalities in humans and impacts the expression of human genes. It is hoped that, as epigenetic research advances, there will be greater understanding.


Headache. Stomach ache. Muscle pain. Rashes. Stanford University