During the Vietnam War, US planes sprayed more than 20 million gallons of herbicides, including the dioxin-contaminated orange agent, on the country's rainforests, wetlands and croplands . Agent Orange cleared the thick jungle vegetation that hid the Viet Cong fighters and destroyed some of the country's food crops, but it was mainly the dioxin contaminant that caused so much damage to many of the country's food crops. Vietnamese and American military. A new article from the University of Illinois and Iowa State University describes the environmental legacy of Agent Orange in Vietnam, including hot spots in which dioxin continues to enter the food supply.
"Current research on Orange agents and dioxin is essentially medical in nature and focuses on the details of human exposure through skin contact and the long-term health effects of US soldiers," says Ken. Olson, Professor Emeritus, Department of Natural Resources and Environmental Sciences. to U of I and co-author of the article. "In this article, we examine the short- and long-term environmental effects on the basis of Vietnamese natural resources and how the persistence of dioxin continues to affect soils, water, sediments, fish , aquatic species, food supply and Vietnamese health. "
Olson and co-author Lois Wright Morton of Iowa State University explain that Agent Orange was a combination of two herbicides, 2,4-D and 2,4,5-T, which do not persist no longer than a few days or weeks in the body. environment when it is exposed to the sun. However, during the production of the agent Orange, a toxic byproduct is formed: dioxin TCDD, the most toxic of the dioxin family. Once dioxin TCDD enters the environment, Olson and Wright Morton say, it can stay for decades or even centuries. This is what happened in the Vietnamese landscape.
The researchers examined a USAID report of 870 pages, as well as a dozen other research reports on contaminated air base sites in Vietnam, to explain the movement and the long-term future of dioxin TCDD in the Vietnamese countryside.
"The path begins with US military spraying in the 1960s, uptake by leaves of trees and shrubs, falling leaves at the soil surface (with direct contact of the spray with the soil), then fixing TCDD to dioxin on soil organic matter and soil clay particles, "said Wright Morton.
From there, the TCDD for dioxin has moved off-site into runoff, sticking to sediment particles and settling in wetlands, marshes, rivers, lakes and ponds . Sediments contaminated by dioxin TCDD were – and still are – ingested by fish and shrimp that feed on the bottom, accumulating in the adipose tissue of these animals and moving up the food chain in many fish forming the basis of the Vietnamese diet. Although fishing is now banned in most contaminated sites, bans have been difficult to enforce and, as a result, dioxin TCDD still enters the human food supply 50 years later.
The article maps the 10 air base sites where dioxin TCDD levels remain at unsafe levels, noting that millions of Vietnamese live in adjacent towns and villages.
"The worst dioxin-contaminated site in Vietnam is the Bien Hoa Air Base, located 30 km north of Ho Chi Minh City," Olson said. "After President Nixon had ordered the US military to stop spraying Agent Orange in 1970, it was the site where all the barrels of agent remaining in Vietnam were recovered. They were then processed and shipped to Johnston Island in the Pacific Ocean, where they were cremated at sea in 1977. "
Based on their research, Olson and Wright Morton recommend the burning of contaminated soils and sediments in the hot spots of the Vietnam Air Base.
"Although incineration is the most expensive technology currently available, it would eliminate dioxin rather than temporarily storing it in a landfill, and incineration would not require further maintenance or treatment." is one of the most commonly used technologies, having been used to treat soils on a mature and tested technology, "say the authors.