The Rainbow Herbicides are a group of chemicals used by the United States military in Southeast Asia during the Vietnam War. Success with Project AGILE field tests with herbicides in South Vietnam in 1961 and inspiration by the British use of herbicides and defoliants during the Malayan Emergency in the 1950s led to the formal herbicidal program Trail Dust (1961–71). Herbicidal warfare is the use of substances primarily designed to destroy the plant-based ecosystem of an agricultural food production and/or destroying foliage which provides the enemy cover.
The Agents used in southeast Asia, their active ingredients and years used were as follow:
- Agent Pink: 60% - 40% n-butyl: isobutyl ester of 2,4,5-T used in 1961, 1965
- Agent Green: (n-butyl ester 2,4,5-T) unclear when used but believed to be at the same time as Pink
- Agent Purple: 50% n-butyl ester of 2,4-D, 30% n-butyl ester of 2,4,5-T, 20% isobutyl ester of 2,4,5-T used 1962–65
- Agent Blue (Phytar 560G): cacodylic acid and sodium cacodylate used from 1962–71 in powder and water solution
- Agent White (Tordon 101): 21.2% (acid weight basis) triisopropanolamine salts of 2,4-D and 5.7% picloram used 1966–71.
- Agent Orange or Herbicide Orange, (HO): 50% n-butyl ester 2,4-D and 50% n-butyl ester 2,4,5-T used 1965–70
- Agent Orange II:50% n-butyl ester 2,4-D and 50% isooctyl ester 2,4,5-T used after 1968.
- Agent Orange III: 66.6% n-butyl 2,4-D and 33.3% n-butyl ester 2,4,5-T.
- Enhanced Agent Orange, Orange Plus, or 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 product called Tordon 101, an ingredient of Agent White.
In Vietnam, the early large-scale defoliation missions (1962-1964) used 8,208 gallons of Agent Green, 122,792 gallons of Pink, and 145,000 of Purple. These were dwarfed by the 11,712,860 gallons of Orange (both versions) used from 1965 to 1970. Agent White started to replace Orange in 1966; 5,239,853 gallons of White were used. The only agent used on a large scale in an anti-crop role was Blue, with 2,166,656 gallons used.
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 US, Canada, Puerto Rico, Korea, India, and Thailand from the mid-1940s to the late 1960s. Herbicide persistence studies of Agents Orange and White were conducted in the Philippines. The Philippine herbicide test program which 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, and Hawaii and later in Malaysia in a cooperative project with the International Rubber Research Institute. Picloram in Agent White and Super-Orange was contaminated by Hexachlorobenzene (HCB) a dioxin-like carcinogen.
- 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. doi:10.1038/nature01537. ISSN 0028-0836. PMID 12700752.
- 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.
- Alvin L. Young. The History, Use, Disposition and Environmental Fate of Agent Orange. Springer. p. 34. ISBN 978-0-387-87486-9.
- Stephen Bull (2004). Encyclopedia of Military Technology and Innovation. Greenwood Publishing Group. p. 6. ISBN 978-1-57356-557-8.
- 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.
- Archives Search Report Findings for Field Testing of 2,4,5-T and Other Herbicides (Report). 4 April 2012. p. 116. http://www.detrick.army.mil/responsible/ArchivalReport2012.pdf. Retrieved August 8, 2013.
- 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.
- DGSC-PI Memorandum for the record: Herbicides reformulation thereof (Operation Guns and Butter meeting) (Report). DOW Chemical Company. September 9, 1966.
- "Herbicides" entry in Spencer C. Tucker, ed. (2011). The Encyclopedia of the Vietnam War (2nd ed.). ABC-CLIO. ISBN 978-1-85109-961-0.
- "Herbicide Tests and Storage in the U.S.". Department of Veterans Affairs. Retrieved 16 June 2010.
- "Herbicide Tests and Storage Outside the U.S.". Department of Veterans Affairs. Retrieved 16 June 2010.
- 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).
- Alvin L. Young, The History of the US Department of Defense Programs for the Testing, Evaluation, and Storage of Tactical Herbicides, December 2006, www.dod.mil/pubs/foi/operation_and_plans/NuclearChemicalBiologicalMatters/TacticalHerbicides.pdf. A more abbreviated version: doi:10.1007/978-0-387-87486-9_2