Chemicals in War-Era Barrels Tested and Confirmed as Tear Gas

The head of the Cambodian Mine Action Authority (CMAC) said Thursday that field testing of a pair of war-era barrels found by villagers in Mondolkiri province earlier this week identified the contents as CS, a tear gas-like powder or aerosol that was used by the U.S. during its war in Vietnam.

CMAC staff initially thought the pair of 200-liter barrels, found about a kilometer apart in O’Reang district, might hold a kind of defoliant, which the U.S. also used extensively during the war to rob the Viet Cong of forest cover.

But CMAC director-general Heng Ratana said field testing of the contents Thursday morning confirmed that the barrels held CS.

“We found that the items there are very similar to what we found in the past…. We believe that inside is CS,” he said. “Now we have hard evidence for verification.”

“This [was] a kind of bomb,” he added, “dropped from the air.”

Mr. Ratana said samples would likely be sent to the National Authority for the Prohibition of Chemical, Nuclear, Biological and Radiological Weapons (NACW), which might do additional testing itself or send the samples on to The Hague for testing by the Organization for the Prohibition of Chemical Weapons.

According to a 2007 report in the Army Chemical Review, a publication of the U.S. Army Chemical Corps, the U.S. sent an estimated 8.2 million kilograms of “riot control agents” to Vietnam between 1962 and 1972, most of it some version of CS.

It says the chemical would sometimes be deployed using large drums that were rolled out the back of helicopters and detonated just above the forest canopy to flush out Viet Cong forces. Some of the barrel bombs failed to explode and were redeployed by the Viet Cong against U.S. and South Vietnamese forces.

Mr. Ratana said the two barrels in Mondolkiri were the 10th such find in CMAC’s records. A group of 11 similar barrels were found in the same district in 2012.

He said none of the barrels have ever been removed, and that the government is still working with “donor partners” to find a way to dispose of them safely.

General Chey Son, who heads the NACW, inside the Ministry of Defense, said the government has been working with experts from the U.S. since 2011 to search for the war-era barrels and that one of three sites identified by the U.S. in Mondolkiri had yet to be found.

He said the U.S. has acknowledged being the source of the barrels and agreed to cover the costs of cleaning them up.

“The U.S. agreed to pay to reclaim the area. We are negotiating,” Gen. Son said.

Sean McIntosh, spokesman for the U.S. Embassy in Phnom Penh, said he could not immediately comment.

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