Administration Claims Syria Used Chemical Weapons

Conclusive evidence that Syrian President Bashar al-Assad’s regime has used chemical weapons against his own people, killing up to 150 and possibly more in the past year, has been claimed by the White House.

But the Obama Administration did not provide details of what evidence it has and how it was obtained. Deputy National Security Adviser for Strategic Communications Benjamin J. Rhodes said on June 13 that the U.S. is not yet prepared to disclose the evidence upon which its intelligence assessment is based.

The U.S., he asserted, is working with its allies “to present a credible, evidentiary case to share with the international community and the public.”

That case to be made will likely include laboratory analyses of physiological samples obtained from a number of individuals wounded in the conflict in Syria. “Each positive result indicates that an individual was exposed to sarin, but it does not tell us how or where the individuals were exposed or who was responsible for the dissemination,” Rhodes said.

Nerve agents such as sarin are volatile organophosphorus compounds that react with a hydroxyl group in biological tissue to form a phosphate ester. When this reaction occurs at the catalytic site of acetylcholinesterase—an enzyme critical to nerve function—the enzyme’s activity is inhibited, leading to convulsions and death. In victims, a lowered activity of cholinesterases in the blood is a good index of exposure, according to the Organisation for the Prohibition of Chemical Weapons, a United Nations affiliate.

Arms control experts tell C&EN that without the public disclosure of the evidence behind the intelligence assessment, it’s difficult to evaluate the validity of the Administration’s claim.

Rhodes said the use of chemical weapons by Syria had crossed President Barack Obama’s “red line” for triggering greater U.S. involvement in the conflict.

Rhodes also said U.S. intelligence believes that the Syrian government has used chemical weapons, including the nerve agent sarin, “on a small scale” against the opposition at least four times over the past year. He said the intelligence community has “high confidence” in that assessment because its information comes from multiple sources.