Rainbow Herbicides

From Wikipedia, the free encyclopedia
Four USAF C-123s spraying Rainbow Herbicide over South Vietnam as part of Operation Ranch Hand
Agent Orange stored at Johnston Atoll in 1976, following the end of US involvement in Vietnam

The Rainbow Herbicides are a group of tactical-use chemicals used by the United States military in Southeast Asia during the Vietnam War. Success with Project AGILE field tests in 1961 with herbicides in South Vietnam was inspired by the British use of herbicides and defoliants during the Malayan Emergency in the 1950s, which led to the formal herbicidal program Trail Dust (see Operation Ranch Hand). Herbicidal warfare is the use of substances primarily designed to destroy the plant-based ecosystem of an agricultural food production and/or to destroy dense foliage which provides the enemy with natural tactical cover.


The United States discovered 2,4-dichlorophenoxyacetic acid (2,4-D) during World War II. It was recognized as toxic and was combined with large amounts of water or oil to function as a weed-killer. Army experiments with the chemical eventually led to the discovery that 2,4-D combined with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) yielded a more potent herbicide.[1] Some batches of 2,4,5-T manufactured for Rainbow Herbicide use were later found to have been contaminated with synthesis-byproduct dioxins including 2,3,7,8-tetrachlorodibenzodioxin (TCDD). Work by researcher Alvin Lee Young identifies examples of Agent Pink and Agent Green containing as much as double the TCDD concentrations observed in Agent Purple or Agent Orange.[2]


This is a list of the different types of agents used, their active ingredients, and the years they were being used during the Vietnam War as follows:[3]

Name Content used
Agent Green 100% n-butyl ester 2,4,5-T prior to 1963[2]
Agent Pink 100% 2,4,5-T (60% n-butyl ester 2,4,5-T, and 40% iso-butyl ester of 2,4,5-T) prior to 1964[2]
Agent Purple 50% 2,4,5-T (30% n-butyl ester of 2,4,5-T, and 20% iso-butyl ester of 2,4,5-T) and 50% n-butyl ester of 2,4-D 1961–1965
Agent Blue (Phytar 560G) 65.6% organic arsenicical (cacodylic acid (Ansar 138) and its sodium salt sodium cacodylate)[2] 1962–1971[4]
Agent White (Tordon 101) 21.2% (acid weight basis) triisopropanolamine salts of 2,4-D and 5.7% picloram 1966–1971[2][4]
Agent Orange Herbicide Orange (HO) 50% n-butyl ester 2,4-D and 50% n-butyl ester 2,4,5-T 1965–1970
Agent Orange II 50% n-butyl ester 2,4-D and 50% isooctyl ester 2,4,5-T after 1968[5][6]
Agent Orange III 66.6% n-butyl 2,4-D and 33.3% n-butyl ester 2,4,5-T.[7]
Enhanced Agent Orange, Orange Plus, Super Orange (SO), or Dow Herbicide M-3393 Standardized Agent Orange mixture of 2,4-D and 2,4,5-T combined with an oil-based mixture of picloram, a proprietary Dow Chemical Company product called Tordon 101, an ingredient of Agent White.[8][9]


In Vietnam, the early large-scale defoliation missions (1962–1964) used 8,208 U.S. gal (31,070 L; 6,835 imp gal) of Agent Green, 122,792 U.S. gal (464,820 L; 102,246 imp gal) of Agent Pink, and 14,500 U.S. gal (55,000 L; 12,100 imp gal) of Agent Purple. These were dwarfed by the 11,712,860 U.S. gal (44,338,000 L; 9,753,000 imp gal) of Agent Orange (both versions) used from 1965 to 1970. Agent White started to replace Orange in 1966; 145,239,853 U.S. gal (549,792,650 L; 120,937,476 imp gal) of White were used. The only agent used on a large scale in an anti-crop role was Agent Blue, with 142,166,656 U.S. gal (538,159,330 L; 118,378,504 imp gal) used.[10] The bombardment occurred most heavily in the area of the Ho Chi Minh Trail.[1]

The rainbow herbicides damaged the ecosystems and cultivated lands of Vietnam, and led to buildup of dioxins in the regional food chain.[1] About 4.8 million people were affected.[11] The environmental destruction caused by this defoliation has been described by Swedish Prime Minister Olof Palme, lawyers, historians and other academics as an ecocide.[12][13][14][15][16]

In addition to testing and using the herbicides in Vietnam, Laos, and Cambodia, the US military also tested the "Rainbow Herbicides" and many other chemical defoliants and herbicides in the United States,[17] Canada, Puerto Rico, Korea, India, and Thailand[18] from the mid-1940s to the late 1960s. Herbicide persistence studies of Agent Orange and Agent White were conducted in the Philippines.[19] The Philippine herbicide test program was conducted in cooperation with the University of the Philippines College of Forestry, and was also described in a 1969 issue of The Philippine Collegian, the college's newspaper. Super or enhanced Agent Orange was tested by representatives from Fort Detrick and Dow Chemical in Texas, Puerto Rico, Hawaii, and later in Malaysia, in a cooperative project with the International Rubber Research Institute.[8] Picloram in Agent White and Super-Orange was contaminated by hexachlorobenzene (HCB) a dioxin-like carcinogen.[citation needed] The Canadian government also tested these herbicides and used them to clear vegetation for artillery training.[20]

A 2003 study in Nature found that the military underreported its use of rainbow herbicides by 2,493,792 U.S. gal (9,440,030 L; 2,076,516 imp gal).[11]

Long-term effects[edit]

Professor Nguyen Thi Ngoc Phuong, at Từ Dũ Obstetrics and Gynecology Hospital is pictured with a group of disabled children in 2004.

Vietnam remains heavily contaminated by dioxin-like compounds, which are classified as persistent organic pollutants. These compounds remain in the water table and have built up in the tissues of local fauna. However, the contamination has begun to deteriorate, and the forest canopy has regrown somewhat since the Vietnam War.[1]

Dioxins are endocrine disruptors and may have effects on the children of people who were exposed.[1]

Rainbow herbicides and other dioxin-like compounds are endocrine disruptors, and evidence suggests that they continue to have long-term health consequences many years after exposure. Because they mimic, or interfere with, hormonal function, adverse effects can include problems with reproduction, growth and development, immune function, and metabolic function. As an example, dioxins and dioxin-like compounds influence the hormone dehydoepiandosterone (DHEA), which has a role in the determination of male or female sex characteristics. There have been thousands of documented instances of health problems and birth defects associated with rainbow herbicide exposure in Vietnam, where tested levels remain high in the soil, water, and atmosphere, decades after initial exposure.

Soldiers exposed to Rainbow Herbicides in Southeast Asia reported long-term health effects, which led to several lawsuits against the U.S. government and the manufacturers of the chemical.[1]

See also[edit]


  1. ^ a b c d e f Ornitz, Sheri L. "Agent Orange and its Continuing Effects Archived 2015-02-09 at the Wayback Machine". British Travel Health Association Journal, vol. 10. Winter 2007.
  2. ^ a b c d e Alvin L. Young (2009-04-21). The History, Use, Disposition and Environmental Fate of Agent Orange. Springer. p. 34. ISBN 978-0-387-87486-9.
  3. ^ Stellman, Jeanne; Stellman, Steven D.; Christian, Richard; Weber, Tracy; Tomasallo, Carrie (17 April 2003). "The extent and patterns of usage of Agent Orange and other herbicides in Vietnam" (PDF). Nature. 422 (6933): 681–7. Bibcode:2003Natur.422..681S. doi:10.1038/nature01537. ISSN 0028-0836. PMID 12700752. S2CID 4419223.
  4. ^ a b Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides; Institute of Medicine (1994). Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. National Academies Press. pp. 89–90. ISBN 978-0-309-55619-4.
  5. ^ Stephen Bull (2004). Encyclopedia of Military Technology and Innovation. Greenwood Publishing Group. p. 6. ISBN 978-1-57356-557-8.
  6. ^ Daniel Vallero (2011). Biomedical Ethics for Engineers: Ethics and Decision Making in Biomedical and Biosystem Engineering. Academic Press. p. 73. ISBN 978-0-08-047610-0.
  7. ^ U.S. Army Corps of Engineers St. Louis District (4 April 2012). Archives Search Report Findings for Field Testing of 2,4,5-T and Other Herbicides (PDF) (Report). p. 116. Archived from the original (PDF) on 22 December 2016. Retrieved August 8, 2013.{{cite report}}: CS1 maint: uses authors parameter (link)
  8. ^ a b Corcoran, Charles A. (December 1968). "Operational Evaluation of Super-Orange (U)- unclassified". Military Assistance Command Vietnam(MAC-V) to Joint Chief of Staff (JCS) message for CINCPAC, USARPAC Ofc Science Adviser. via National Security Archives at George Washington University. {{cite web}}: Missing or empty |url= (help)
  9. ^ DGSC-PI Memorandum for the record: Herbicides reformulation thereof (Operation Guns and Butter meeting) (Report). Dow Chemical Company. September 9, 1966.
  10. ^ "Herbicides" entry in Spencer C. Tucker, ed. (2011). The Encyclopedia of the Vietnam War (2nd ed.). ABC-CLIO. ISBN 978-1-85109-961-0.
  11. ^ a b Wright, Laura. "New Study Finds Agent Orange Use Was Underestimated". Scientific American, April 17, 2003.
  12. ^ Zierler, David (2011). The invention of ecocide: agent orange, Vietnam, and the scientists who changed the way we think about the environment. Athens, Ga.: Univ. of Georgia Press. ISBN 978-0-8203-3827-9.
  13. ^ "How Imperative Is It To Consider Ecocide As An International Crime?". IJLLR. 2022-12-18. Retrieved 2023-06-21.
  14. ^ Falk, Richard A. (1973). "Environmental Warfare and Ecocide — Facts, Appraisal, and Proposals". Bulletin of Peace Proposals. 4 (1): 80–96. ISSN 0007-5035.
  15. ^ "Industrial disasters from Bhopal to present day: why the proposal to make 'ecocide' an international offence is persuasive – The Leaflet". theleaflet.in. 2022-02-17. Retrieved 2023-06-21.
  16. ^ Giovanni, Chiarini (2022-04-01). "Ecocide: From the Vietnam War to International Criminal Jurisdiction? Procedural Issues In-Between Environmental Science, Climate Change, and Law". {{cite journal}}: Cite journal requires |journal= (help)
  17. ^ "Herbicide Tests and Storage in the U.S." Department of Veterans Affairs. Retrieved 16 June 2010.
  18. ^ "Herbicide Tests and Storage Outside the U.S." Department of Veterans Affairs. Retrieved 16 June 2010.
  19. ^ Fryer, J. D.; Blackman, G. E. (January 1972). "Preliminary Proposals for the Study of Persistence of Herbicides in Forest and Mangrove Soil". NAS committee on the effect of Herbicides in Vietnam. National Academy of Science, (NAS). {{cite web}}: Missing or empty |url= (help)
  20. ^ Pelletier, Richard. "Agent Purple Deadlier than Agent Orange." Bangor Daily News, 1 July 2005.

Further reading[edit]

External links[edit]