Agent Blue Spraying in the Mekong Delta during the Vietnam War: Fate of the Arsenic Based Herbicide Weapon Used to Destroy Rice Crop and Mangrove Forests

Abstract

Agent Blue, a mixture of cacodylic acid (CH 3 ) As O 2 H) and sodium cacodylate (C 2 H 6 AsNaO 2 ), was a tactical arsenic-based herbicide used during the Vietnam War to destroy grasses and rice crops. Natural and synthetic sources of arsenic can degrade into water-soluble forms and persist in groundwater and potentially contribute to elevating As levels in drinking water. The United States Department of Defense (DOD) and United States Department of Agricultural (USDA) Operation Ranch Hand records for tactical herbicides including Agent Blue sprayed in southern Vietnam during the Vietnam War (1961-1971) are very detailed, rather complete and publicly available. The same is not true for tactical herbicides sprayed by the Republic of Vietnam (RV) during the Khai Quang program which was supported by the U.S. Army, U.S. Navy and Central Intelligence Agency (CIA) in the Mekong Delta. Agent Blue was sprayed by the RV military for three years before the official start of the American-Vietnam War. Few, if any, RV military, US Army, US Navy and CIA spray records exist from 1962 to 1965. Vietnam War veterans, historians and scholars have reported the spraying of 3.2 million liters (468,008 kg As) of Agent Blue on rice paddies and mangrove forests in the Mekong Delta and Central Highlands by the RV military with the support of the US Army, US Navy and CIA. The Institute of Medicine estimated that 3.2 million liters (468,000 kg As) were sprayed during the RV Khai Quang program. This was in addition to the U.S. Air Force’s Operation Ranch Hand spraying of the tactical herbicide Agent Blue primarily by C-123 aircraft. The Operation Ranch Hand missions maintained location and quantities of herbicides sprayed (over 4,712,000 liters (664,392 kg As) from 1961-1971. The RV military and US military (Army and Navy) spray equipment included hand and backpack sprayers, sprayers mounted on Brown Water Navy boats, on Army track vehicles and Army land-based helicopters and helicopters based on the decks of Blue Water Navy ships. Some of these spray missions were a military secret and spray records were classified or if kept were not maintained. Agent Blue containing cacodylic acid had a short half-life and degraded to water-soluble arsenic, which was released into the surface water and/or leached into the groundwater. Once the water-soluble arsenic leached into the Vietnam Mekong Delta groundwater, the arsenic-rich water was pumped back to the surface by tens of thousands of tube wells for urban and agricultural use. The primary objectives of this research are to explore the conditions during the Vietnam War under which 1) the RV military herbicide spray program with the support of the US Navy, CIA and US Army, and 2) the US Air Force spray program during Operation Ranch Hand may have significantly contributed to the natural and anthropic As spikes found in the Mekong Delta today. The environmental impacts of Agent Blue, on the Menominee River at manufacturing sites in the United States, were studied to identify possible As remediation and mitigation strategies. The lessons previously learned at the manufacturing sites in Wisconsin and Michigan, United States can be considered and applied to the Mekong Delta to help mitigate and remediate the arsenic-rich surface water, soil, sediment and groundwater found in the Mekong Delta.