The Fate of Agent Blue, the Arsenic Based Herbicide, Used in South Vietnam during the Vietnam War

The destruction of the South Vietnamese rice (Oryza sativa L) crop using an arsenic-based herbicide known as Agent Blue during the American Vietnam War (1965-1972) was not a secret;however, it received little media attention in the United States. Republic of Vietnam and United States (U.S.) militaries began destroying food crops (rice) in November of 1962 primarily via aerial applications in the Mekong Delta and Central Highlands of South Vietnam. Spraying of Agent Blue on 100,000 ha of mangrove forests and about 300,000 ha of rice paddies just before rice harvest time resulted in the destruction of the standing crop and rendered the land contaminated with arsenic (As). Six Rainbow herbicides, commonly called Agent Orange, Agent Green, Agent Pink, Agent Purple, Agent White, and Agent Blue, were sprayed on wetlands, rice paddies, forests, mangroves, bamboo and military base perimeter fences to defoliate jungle vegetation, reveal guerilla hiding places and destroy the food supply of enemy troops. South Vietnamese farmers, U.S. and Republic of Vietnam military personnel, and communist insurgents were exposed to these herbicides with immediate and longer term impacts on personal health, civilian household food security and population-wide famine. Agent Blue (cacodylic acid, C2H2AsO2,) was the most effective of all the Rainbow herbicides in killing rice and grasses. Manufacturing of cacodylic acid began in the late 1950s in the U.S. at the Ansul Company chemical plant in Marinette, Wisconsin and Menominee, Michigan. During the Vietnam War, ocean going ships were loaded with 208-liter Agent Blue barrels and shipped via the St. Lawrence Seaway to the coast of South Vietnam. Arsenic (As) is a naturally occurring element that is found throughout SE Asia deltas including the Mekong Delta. Today arsenic contaminated rice and groundwater are growing concerns as neither naturally occurring arsenic nor anthropic arsenic have a half-life and cannot be destroyed. Anthropic arsenic has remained in the Mekong Delta environment for the last 60 years and added to persistent As contamination in water supplies, sediments and soils. Water soluble arsenic primarily leaches into the soil root zone and the groundwater or is carried by floodwater into adjacent waterways or volatilized under anaerobic rice paddy conditions as gaseous arsine. The health of 15 million Vietnamese people living in the Mekong Delta is at risk from the combination of manufactured and natural As in drinking water and food supply. The As in the contaminated rice paddy soil, sediment and water is up taken by fish, shrimp or by crop vegetation and trace amounts can end up in the food supply (rice grain) or be bioaccumulated by the fish, shrimp and birds which when eaten were bioaccumulated in the Vietnamese people. It is urgent that elevated As concentrations in water supplies and agricultural products be identified and mitigated through better run-off control and groundwater management;improved rice genetics and alternate crop selections;shifts in crop management associated with tillage, fertilization and phosphorus use;and systematic monitoring of food and drinking water.

St. Lawrence Seaway: Western Great Lakes Basin

The St. Lawrence Seaway connects Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario to the Atlantic Ocean. The lakes and connecting rivers, St. Mary’s, St. Claire, Detroit, Niagara and St. Lawrence, have been a major artery for transportation, migration and trade. The Menominee River flows into Green Bay and Lake Michigan and connects to the St. Lawrence Seaway. The Great Lakes have been sailed for trading and commercial purposes since at least the 17th century. Approximately 6000 ships have sunk killing more than 30,000 sailors and passengers. Cold Canadian winds over the three Western Great Lakes pick up moisture when the lakes are not yet frozen and create snow belts in the states of Wisconsin, Michigan and in Ontario, Canada. The Western Great Lakes moderate the seasonal temperatures as they absorb heat and cool the air in the summer. The lakes radiate heat in the fall. This temperature buffering creates fruit belts further north of where the fruit is traditionally grown. During the 1950s and 1960s all of the Agent Blue, the arsenic containing herbicide used in Vietnam War, was manufactured on the banks of the Menominee River by the Ansul Company at Marinette, Wisconsin. The groundwater and the river bottom are now heavily contaminated with arsenic compounds that were released from 1957 to 1977 by Ansul as a result of the manufacture of the herbicide. The linkage of Lake Michigan to the Mississippi River has allowed Chicago’s wastewater to be disposed of into the tributaries of the Illinois River and Mississippi River to avoid contaminating Lake Michigan the source of Chicago’s drinking water. An unintended consequence of linking the Western Great Lakes basin with the Mississippi River basin was the creation of the wet pathway (Chicago Sanitary and Ship Canal) through which the flying Asian carp is trying to use to get into the Great Lakes. An electric fish barrier was constructed on the Chicago Sanitary and Ship Canal in an attempt to prevent the carp from migrating into Lake Michigan, the Great Lakes basin and the St. Lawrence Seaway. The Western Great Lakes shorelines are actively eroding partly as a consequence of the high surface water levels. In June of 2020 Lake Michigan, Lake St. Claire and Lake Huron experienced the highest water level ever recorded since the 1800s. The high risk erosion areas are retreating at the average rate of 30 cm per year for the last 15 years. Planned urban development in a high risk area helps to prevent the loss of buildings. Locating structures back from lake bluffs promotes natural shorelines and reduces the need for engineered shore protection. Erosion of the sediment under the Mackinac Bridge and pipeline has occurred. The pipeline which carries 87 million liters of oil per day between Sarnia, Ontario and Superior, Wisconsin is at risk.