The dioxin TCDD can linger in the environment for decades or even centuries.
During the Vietnam War the U.S. sprayed the Southeast Asian nation’s jungles and wetlands with vast quantities of a herbicide and defoliant known as Agent Orange. The aim was to flush Viet Cong guerrillas out of their rural hideouts. The 20 million gallons of the substance used in the war would cause a decades-long health crisis in Vietnam.
Agent Orange also wreaked havoc on local ecosystems. Half a century on, the environmental effects are still being felt, two U.S. researchers say. Agent Orange comprised two herbicides, both of which disintegrate after a few weeks upon exposure to sunlight. However, the researchers say, when Agent Orange was produced, a highly toxic byproduct resulted in the form of the dioxin TCDD, which can linger in the environment for decades or even centuries.
“The pathway begins with the U.S. military spraying in the 1960s, absorption by tree and shrub leaves, leaf drop to the soil surface (along with some direct contact of the spray with the soil), then attachment of the dioxin TCDD to soil organic matter and clay particles of the soil,” explains Lois Wright Morton, of Iowa State University who was one of the two authors of a new paper on the environmental aftereffects of Agent Orange in Vietnam.
Large quantities of dioxin TCDD were washed into water sources, including wetlands, marshes, rivers, lakes, and ponds. There the toxin accumulated in sediments where bottom-feeding fish and shrimp have been ingesting it ever since. Accumulating in the fatty tissue of those animals, the toxin has permeated the aquatic food chain. Fishing has been banned at most of the worst-contaminated areas, but such bans are routinely ignored. As a result, the toxin still ends up on the plates of people across much of Vietnam.
There’s of course a lesson in this: the wanton pollution of nature, whether for reasons of war or economic growth, can have long-lasting consequences. And polluting is invariably a lot easier than cleaning up pollution. In the case of Vietnam, incinerating heavily contaminated soil could provide a workable solution to rid the country of a potent toxin left by a war that most Vietnamese people today, those under 50, know only from the recollections of their parents and grandparents.