US to help clean up Agent Orange from Vietnamese site

Some 40 years after its military planes sprayed the herbicide Agent Orange across Vietnam's forests, the US has begun a project to clean up the contamination at one of the worst-affected sites.

Agent Orange left millions of acres of dead jungle in its wake. The plants grew back quickly, but an extremely toxic contaminant in the herbicide ? dioxin ? lingered in the soil. An estimated 3 million Vietnamese people have been exposed to its effects.

It has been difficult to track the effects of dioxin, as it raises people's risk of a range of diseases rather than killing them outright. Exposure may also cause birth defects and neurological problems.

"Dioxin is very persistent. What we do know is a certain amount is getting into bodies through food, even today," says Arnold Schecter at the University of Texas Southwestern in Dallas.

The task of identifying Agent Orange's victims has been aided by records that show exactly where it was sprayed. Three locations retain particularly high levels of the chemical in their soil: up to 1 million parts per trillion, says Schecter ? 1000 parts per trillion is considered the safe limit.

The US will target one of these sites, a 19-hectare area near Da Nang Airport, to test the economic and technological feasibility of a soil treatment process ? however, the US is not admitting fault.

Used in the US to treat highly contaminated "superfund" military sites, the soil treatment process involves removing soil from the site and heating it to 355 ?C to destroy dioxin. The US is investing $43 million in the project, and it is expected to take about four years.

If the US decides that this method is too expensive, there are a multitude of other clean-up options, says Schecter. The cheapest of these would be to put all the soil in a toxic waste dump; the most effective would be to incinerate it at high temperatures. Other proposals include pouring concrete all over the contaminated sites, or simply walling them off to humans and animals.

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