By Joe Pinkstone For Mailonline
Published: 15:16 GMT, 1 March 2019 | Updated: 18:00 GMT, 1 March 2019
A toxic by-product from the US bombardment of Vietnamese countryside with the herbicide Agent Orange is still contaminating the environment today.
The chemical constituents of Agent Orange itself break down within weeks of application but a byproduct called dioxin TCDD can persist for decades or centuries.
US forces dropped 20 million gallons of the concoction over Vietnam during the war to thin vegetation utilised by the Viet Cong.
The toxic chemical is still present in high concentrations in the environment and in the food chain around ex-US airbases.
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US forces dropped 20 million gallons of Agent Orange over Vietnam during the war to thin vegetation utilised by the Viet Cong. A toxic by product is now still present in the environment
Researchers examined data from an 870-page report and found ten sites where the dioxin TCDD levels remain at dangerous levels.
These old airbases are surrounded by millions of Vietnamese inhabitants - with the long-term health impacts of prolonged exposure to the potent chemical still unknown.
'The worst dioxin-contaminated site in Vietnam is Bien Hoa airbase, which is 30 miles north of Ho Chi Minh City,' Dr Olson, lead author of the study published in the Open Journal of Soil Science from the University of Illinois.
'After President Nixon ordered the US military to stop spraying Agent Orange in 1970, this is the site where all the Agent Orange barrels remaining in Vietnam were collected.
'The barrels were processed and shipped to Johnston Island in the Pacific Ocean, where they were incinerated at sea in 1977.'
The fallout from Agent Orange and dioxin has meant most ongoing research investigates the medical