View Full Version : The extent and patterns of usage of Agent Orange and other herbicides in Vietnam

05-08-03, 11:44 AM
The extent and patterns of usage of Agent Orange and other herbicides in Vietnam

Herbicides including Agent Orange were sprayed by United States forces for military purposes during the Vietnam War (19611971) 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.

Between 1961 and 1971 herbicide mixtures, nicknamed by the coloured identification band painted on their 208-litre storage barrels, were used by United States and Republic of Vietnam forces to defoliate forests and mangroves, to clear perimeters of military installations and to destroy 'unfriendly' crops as a tactic for decreasing enemy food supplies1. The best-known mixture was Agent Orange. About 65% of the herbicides contained 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), which was contaminated with varying levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Herbicide mixtures are listed in Table 1.

In 1970, the US Congress directed the US Department of Defense (DoD) to engage the National Academy of Sciences to conduct a comprehensive study (NAS-1974) of the ecological and physiological effects of defoliation in Vietnam2. NAS-1974 relied on a chronological record, the HERBS file3, which contained flight path coordinates of Air Force spraying missions carried out between August 1965 and December 1971 and from 1968 on US Army helicopter spraying missions. In 1985, the DoD supplemented this file with the Services-HERBS file, derived from additional record searches. The HERBS file error rate was about 10%, attributable largely to transcription, data entry and pilot recording errors4. Under contract to the NAS, using data more complete than were then available, we undertook, in close collaboration with the US Armed Services Center for Research of Unit Records (CRUR), to correct both files (see Methods) and during this process discovered much additional archived data.

Military herbicide operations in Vietnam became a matter of scientific controversy from their inception5, 6. In April 1970, 2,4,5-T was banned from most US domestic uses, on the basis of evidence of its teratogenicity7. The Agent Orange Act of 1991 requested the Institute of Medicine (IOM) to assess the strength of the evidence for association between exposure to military herbicides and disease in veterans and the feasibility of conducting further epidemiological studies. The IOM recommended that the Department of Veterans Affairs develop historical reconstruction methods for characterizing exposure to herbicides in Vietnam8, 9. The present report is the result of that recommendation.

Background to military use of chemical defoliants
The DoD's Advanced Research Project Agency's (ARPA) Project Agile was instrumental in the US development of herbicides as a military weapon, an undertaking inspired by the successful British use of 2,4,5-T to destroy jungle-grown crops during the insurgency in Malaya. ARPA supported tests on combinations and concentrations of herbicides; calibration studies of the spray delivery system to achieve the desired 28 l ha-1 (3 gallons/acre) rate; and experiments on optimal conditions to minimize spray drift10. ARPA also developed the Hamlet Evaluation System11 which collected the political census data that we use here for estimating population exposures.

The first large-scale US military defoliation took place in Camp Drum, New York, in 1959, using Agent Purple (a 50:50 mixture of 2,4-D and 2,4,5-T) and a spray system which was the model for those used in Vietnam. Herbicide tests were run from August to December 1961 in the Republic of Vietnam (RVN), using dinoxol and trinoxol12, 13. An insecticide test series was also undertaken. The first major herbicide shipment arrived in RVN in January 1962; defoliation targets were sprayed during September and October 1962 (Agent Purple); crop destruction targets were sprayed in November 1962 (Agent Blue)14. Systematic testing of herbicides and calibration of herbicide delivery systems continued for several years15.

A 1962 pact assigned ownership of the herbicides to RVN when they entered its territory. Vietnamese physically handled the herbicides during off-loading, transport, and transfer to storage tanks. RVN ownership complicated United States Air Force (USAF) logistics and record-keeping, and disposal when Agent Orange use was abandoned in mid-1970 (ref. 16). US policy emphasized that its forces were assisting the RVN in the herbicide programme. C-123 aircraft carried out the missions camouflaged and equipped with removable identification insignias. Crop destruction aircraft bore South Vietnamese markings and were accompanied by a Vietnamese crew member under a State Department/DoD concept known as Farmgate17. Flight crew wore civilian clothing.

The herbicide targets and US Air Force project folders
US Air Force (USAF) operations, codenamed Operation Ranch Hand, dispersed more than 95% of all herbicides used in Operation Trail Dust, the overall herbicide programme. Other branches of the US armed services and RVN forces, generally using hand sprayers, spray trucks (Buffalo turbines), helicopters and boats, sprayed much smaller quantities of herbicide. Operation Ranch Hand was organized into projects that underwent a complex combined South Vietnamese and US approval system which could sometimes last as long as one year. Each project consisted of specific targets that were often amended or deleted during the approval process. Crop destruction also required White House approval until 1963, after which final approval was delegated to the US Ambassador to the RVN.

We reconstructed the project number to which each mission in the HERBS file belonged by concatenating two data fields. Aggregating missions by project number transforms the HERBS file from a chronological listing of criss-crossing flight paths into target-related groups of flights flown at different points in time (Figs 1 and 2). The importance of projects and targets has not been sufficiently appreciated. NAS-1974, and even the USAF itself18, inverted the hierarchy thus: "All missions within a target formed a project".





05-08-03, 11:49 AM
We think my dad (USMC 67-68) had/died of some of the listed side effects. I wouldn't wish AO on anyone.