Julia Poska | March 1, 2019
Forty-four years since the fall of Saigon, chemical weapons still exist in Vietnamese ecosystems. A new study from the University of Illinois and Iowa State University assessed the environmental impacts of one especially persistent chemical byproduct.
“Agent Orange,” banned in the U.S. since 1971, was a combination of two herbicides sprayed from U.S. aircraft to thin out the jungle and destroy crops. Individually, the herbicides would have disappeared in just days, but together they produced “TCDD,” a highly toxic dioxin can last over 100 years in the right conditions.
Illinois’ Ken Olson, professor emeritus of environmental science, and Iowa State professor of sociology Lois Wright Morton sorted through previous research and humanitarian reports on contaminated Vietnam air bases. They were able to determine TCDD’s paths through the environment, as well as “hotspots” where it still enters the human food supply.
They found that TCDD destroyed Vietnam’s mangroves and mature forests, which may not return to their previous condition for centuries and are now plagued with invasive species. In sprayed areas, runoff, soil erosion and landslides degrade soil, change topography and spread TCDD even further.
Researchers believe that TCDD persists longest in river and sea sediment. TCDD at the bottom of waterbodies is still eaten by bottom-feeding fish and stored in their fatty tissues. The toxin bioaccumulates and biomagnifies in the fatty tissues of their predators when the fish are eaten by humans or other animals.
According to the World Health Institute, the health effects of consuming dioxins like TCDD include skin lesions, altered liver function, and impairment of the immune, nervous, endocrine and reproductive systems.
Olson and Wright Morton advise that the only way to destroy TCDD is to incinerate contaminated soils and sediments.