Herbicides including Agent Orange were sprayed by United States forces for military purposes during the Vietnam War (1961–1971) at a rate more than an order of magnitude greater than for similar domestic weed control. In 1974, the US National Academy of Sciences published estimates of the extent and distribution of herbicides sprayed. Here we present revised estimates, developed using more-complete data. The spray inventory is expanded by more than seven million litres, in particular with heavily dioxin-contaminated herbicides. Estimates for the amount of dioxin sprayed are almost doubled. Hamlet census data reveal that millions of Vietnamese were likely to have been sprayed upon directly. Our identification of specific military herbicide targets has led to a more coherent understanding of spraying. Common errors in earlier interpretations of the spray data are also discussed.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Buckingham, W. A. Jr Operation Ranch Hand: The Air Force and Herbicides in Southeast Asia 1961–1971 (Office of United States Air Force History, Washington DC, 1982)
National Research Council Committee on the Effects of Herbicides in Vietnam. The Effects of Herbicides in South Vietnam. Part A. Summary and Conclusions (National Academy of Sciences Press, Washington DC, 1974)
Data Management Agency, US MACV. Herbicide Report System (HERBS). Document No. DARU07 (US Military Assistance Command Vietnam, San Francisco, 1970)
Heizer, J. R. Data Quality Analysis of the HERB 01 Data File. No. MTR-5105 (The Mitre Corporation, Washington DC, 21 April 1971).
Wiersma, G. B. Ecological Impact of Antiplant Agents and Implications for Future Use. Report No. ACN 16223 (US Army Combat Developments Command, Institute of Land Combat, Fort Belvoir, VA, July 1970)
Huddle, F. P. A Technology Assessment of the Vietnam Defoliant Matter. Report to the Subcommittee on Science, Research and Development, Committee on Science and Astronautics. (Science Policy Research Division, Legislative Reference Service, Library of Congress Serial F, Washington DC, 8 August 1969).
Courtney, K. D. et al. Teratogenic evaluation of 2,4,5-T. Science 168, 864–866 (1970)
Institute of Medicine Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (National Academy of Sciences Press, Washington DC, 1994).
Committee on the Assessment of Wartime Exposure to Herbicides in Vietnam, Institute of Medicine. Characterizing Exposure of Veterans to Agent Orange and Other Herbicides Used in Vietnam: Scientific Considerations Regarding a Request for Proposals for Research (National Academy of Sciences Press, Washington DC, 1997).
Harrigan, E. T. Calibration Test of the UC-123K/A/A45Y-1 Spray System. Technical Report No. ADTC-TR-70–36 (Armament and Development Test Center, Eglin AFB Florida, February 1970)
Thayer, T. C. War without Fronts: The American Experience in Vietnam. Westview Special Studies in Military Affairs (Westview Press, Boulder, CO, 1985)
Brown, J. W. Vegetational Spray Tests in South Vietnam (US Army Chemical Corps Biological Laboratories, Fort Detrick, MD, 1962)
Brown, J. W. Vegetational Spray Tests in South Vietnam (Supplement U) (US Army Chemical Corps Biological Laboratories, Fort Detrick, MD, 1962)
Olenchuk, P. G., Burke, R. T., Henderson, O. K. & Davis, W. E. Evaluation of Herbicide Operations in the Republic of Vietnam (September 1962–September 1963) (US Military Assistance Command, Vietnam, APO San Francisco, 10 October 1963).
Darrow, R. A., Truchelat, G. B. & Bartlett, C. M. OCONUS Defoliation Test Program (US Army Biological Center, Fort Detrick, MD, July 1966)
Cecil, P. F. Herbicidal Warfare. The Ranch Hand Project in Vietnam (Praeger Scientific, New York, 1986)
Collins, C. V. Herbicide Operations in Southeast Asia July 1961-June 1967. Report No. DTEC 67–0020 (HQ PACAF, Directorate, Tactical Evaluation, CHECO Division, APO San Francisco, 11 October 1967).
Young, A. L., Calcagni, J. A., Thalken, C. E. & Tremblay, J. W. The Toxicology, Environmental Fate and Human Risk of Herbicide Orange and Its Associated Dioxin. US AF Technical Report OEHL-TR-78–92 (Brooks AFB, TX, 1978)
US Department of Defense. Records of the US Forces in Southeast Asia, Headquarters, Military Assistance Command Vietnam (MACV), Assistant Chief of Staff for Operations (J3), Chemical Operations Division (MACJ-3–09). Herbicide Operations Plans (1966–1967) series, Record Group 472 (National Archives and Records Administration, College Park, MD; 1950–75)
Panel on Herbicides of the President's Science Advisory Committee. Report on 2,4,5-T (Executive Office of the President, Office of Science and Technology, Washington DC, March 1971)
Dwernychuk, L. W. et al. Dioxin reservoirs in southern Viet Nam—a legacy of Agent Orange. Chemosphere 47, 117–137 (2002)
Young, A. L. Ecological Studies on a Herbicide-equipment Test Area (TA C-52A). (Air Force Armament Laboratory, Eglin AFB, 1974)
Letter from Colonel W. T. Moseley to Dr C. E. Minarik. No. MACC007 (US Military Assistance Vietnam, APO San Francisco, 10 May 1967).
Craig, D. A. Use of Herbicides in Southeast Asia. Historical Report. (San Antonio Logistics Center, Directorate of Energy Management, San Antonio AFB, TX, 1975)
Darrow, R. A. Historical, Logistical, Political and Technical Aspects of the Herbicide/Defoliant Program, 1967–1971: A Resume of the Activities of the Subcommittee on Defoliation/Anticrop Systems for JTCG/CB. (Vegetation Control Committee, Fort Detrick, MD, September 1971)
Revised Draft Environmental Impact Statement. Disposition of Orange Herbicide by Incineration. Report No. AF-ES-72–2D. (Department of the Air Force, Washington, DC, April 1974)
Hughes, B. M. et al. Analytical Methodology for Herbicide Orange. Vol 1: Determination of Chemical Composition. No. ARL 75–0110 (Wright-Patterson AFB, Aerospace Research Laboratories, OH, May 1975)
Fee, D. C., Hughes, B. M., Tiernan, T. O., Hill, C. E. & Taylor, M. L. Analytical Methodology for Herbicide Orange. Vol II: Determination of Origin of USAF Stocks. No. ARL 75–0110 (Wright-Patterson AFB, Aerospace Research Laboratories, OH, May 1975)
Darrow, R. A., Irish, K. R. & Minarik, C. E. Herbicides Used in Southeast Asia. (United States Army Plant Sciences Laboratories, Fort Detrick, Maryland, 1969)
Young, A. L. & Reggiani, G. M. Agent Orange and Its Associated Dioxin: Assessment of a Controversy (Elsevier, Amsterdam, 1988)
US Department of Defense. Hamlet Evaluation System (HES). [Electronic Records]. Record Group 330 (National Archives and Records Administration Center for Electronic Records, College Park, MD, 1967–74)
Orians, G. H. & Pfeiffer, E. W. United States goals in Vietnam. Science 169, 1030 (1970)
Smith, C. & Watkins, D. The Vietnam Map Book. Self-help Guide to Herbicides Exposure. (Winter Soldier Archive, Berkeley, CA, November 1981)
Blackman, G. E., Fryer, J. D., Lang, A. & Newton, M. The Effects of Herbicides in South Vietnam. Part B: Working Papers. Persistence and Disappearance of Herbicides in Tropical Soils (National Academy of Sciences-National Research Council, Washington DC, 1974)
US Military Assistance Command, Vietnam. Vietnam Lessons Learned No. 74: Accidental Herbicide Damage (MACV, APO San Francisco, 15 September 1969).
US Department of Defense Records of the US Forces in Southeast Asia, 1950–1975, Headquarters, Military Assistance Command Vietnam (MACV), Assistant Chief of Staff for Operations (J3) Record Group 472 (National Archives and Records Administration, Modern Military Records LICON, Textual Archives Services Division, College Park, MD, 1950–75)
American Embassy, Phnom Penh. Telegram No. 875, NSF-VN Vol. X, Box 196–98 (John F. Kennedy Presidential Library, Boston, MA, 18 May 1963).
Cecil, P. F. The Air Force Ranch Hand Project in Southeast Asia: Operations and Consequences PhD dissertation, Texas A&M Univ. (1984)
Hay, A. The Chemical Scythe: Lessons of 2,4,5-T and Dioxin 187–195 (Plenum, New York, 1982)
Cyranoski, D. US and Vietnam join forces to count cost of Agent Orange. Nature 416, 262 (2002)
‘202 Committee’ List of 202 Task (sic) Realized From January 1962 to September 1965. (Military Assistance Command, Vietnam, Saigon, undated)
Dashiell, T. R. (Office of the Director of Defense Research and Engineering) Comments to Dr. P. Kunstadter's Comparison of HERBS and 202 Records (Memorandum to P. Ross, National Academy of Sciences, 11 July 1973).
US Department of Defense Herbicide Files, 1965–1970. Record Group 30 (National Archives and Records Administration Center for Electronic Records, College Park, MD, 1965–70)
R2V Software Able Software Corp, 2000; http://www.ablesw.com
Stellman, J. M. et al. A Geographic Information System for characterizing exposure to Agent Orange and other herbicides in Vietnam. Environ. Health Perspect 111, 321–323 (2003)
This research was supported by the National Academy of Sciences, the Department of Veterans Affairs and USPHS at the National Cancer Institute. We thank D. Hakenson and his staff at the US Armed Services Center for Research of Unit Records for technical support and access to military records; the staff of the National Archives and Records Administration, particularly R. Boylan and M. O. Adams; N. Heim for assistance with illustrations and F. Benjamin for assistance with military records. R.C. is a retired member of the US Army.
The authors declare that they have no competing financial interests.
About this article
On the Shoulders of Giants: Continuing the Legacy of Large-Scale Ecosystem Manipulation Experiments in Puerto Rico
Forest Ecology and Management (2019)
The agro-enabled urban revolution, pesticides, politics, and popular culture: a case study of land use, birds, and insecticides in the USA
Environmental Science and Pollution Research (2019)
Effects of perinatal dioxin exposure on development of children: a 3-year follow-up study of China cohort
Environmental Science and Pollution Research (2019)
Avicennia marina maintains genetic structure whereas Rhizophora stylosa connects mangroves in a flooded, former inner sea (Vietnam)
Estuarine, Coastal and Shelf Science (2019)