Dioxin contamination in Da Nang more serious than expected: conference

The event, organized by the National Steering Committee for Post-war Clearance of Ordnance and Toxic chemicals and USAID, shared some details on dioxin cleanup at the Da Nang International Airport, a U.S. air base during the Vietnam War.

Pham Quang Vu, head of the Air Force and Air Defense’s Military Science Division, said earlier calculations had underestimated the actual contamination at the airport.

He said the actual amount of contaminated soil is 162,500 cubic meters and not 72,900 cubic meters as earlier estimated.

Anthony Kolb, chief of USAID’s environmental remediation unit, explained that experts only took soil samples from the surface and from that determined the depth to which the dioxin could have penetrated.

The dioxin had percolated three meters deeper than expected, he said at the conference in Da Nang.

Vu said the miscalculation could be attributed to the fact this was the first time this particular technology was used to remove dioxin from the soil on such a large scale. It involves heating the contaminated soil while covering it in concrete.

The finding could help make future dioxin assessments more accurate, especially at another ongoing cleanup project at the Bien Hoa Air Base in the southern province of Dong Nai. Bien Hoa is considered one of the worst dioxin-contaminated spots, with some 850,000 tons of soil feared contaminated.

"We expect to cleanse 500,000 cubic meters of contaminated soil in Bien Hoa, meaning 50 hectares of land," Chung said.

Field workers use a heating process to remove dioxin from contaminated soil. Photo courtesy of Vietnam's Ministry of Defense

Since 2012, when the Da Nang project was initiated, it has cleaned 94,600 cubic meters of soil at the airport, reducing the dioxin level from 1,200 parts per trillion (ppt) to below 150ppt, and has placed 68,000 cubic meters of contaminated soil in the southwestern part of the airport, which contained less than 1,000ppt of dioxin, under long-term management. Dioxin concentration of 100ppt is considered high.

Kolb of USAID said 32.4 hectares of land has been cleaned.

"This project is the most ambitious we have ever undertaken."

Da Nang has been off the official list of dioxin contaminated spots in Vietnam after the cleanup, Vu said.

The cost of the work is budgeted at around $108.5 million, with $106 million coming from ODA grants.

Vietnam still has 28 dioxin hotspots, including airports in several cities and provinces which were used by the U.S. military during the Vietnam War.

The government hopes to complete the task of decontaminating the country’s soil by 2030.

Dioxins and dioxin-like compounds were contained in Agent Orange, which was sprayed by the U.S. military from 1961 to 1971 to clear jungle hideouts of Vietnamese soldiers. Some 80 million liters of the deadly defoliant are said to have been sprayed over 78,000 square kilometers (30,000 square miles) of Vietnamese territory.

The chemical, which stays in the soil and at the bottom of lakes and rivers for generations, was later found to be capable of damaging genes, causing deformities in the offspring of exposed individuals.

The Vietnam Red Cross estimates 2.1 to 4.8 million Vietnamese were directly exposed to Agent Orange and other chemicals that have been linked to cancers, birth defects and other chronic diseases since the war.