Proof Sought For Chemical Weapons

Although “some evidence” has surfaced that chemical weapons have been used in Syria’s prolonged and intense civil war, it isn’t enough to warrant action, President Barack Obama said last week at a news briefing.

Obama said more facts must be known before he is willing to consider any kind of escalation or U.S. involvement in Syria. “We don’t know how [the chemical weapons] were used, when they were used, who used them,” he said. The U.K. and France have claimed that Syria has used poison gases in its war with opposition political groups. But “we don’t have a chain of custody that establishes what exactly happened,” the President said.

Syria’s cache of chemical weapons is believed to be the largest in the Middle East. Syrian President Bashar al-Assad’s stockpile of the nerve agent sarin stockpile “is estimated in the high hundreds of tons, possibly over 1,000 tons,” says Laicie Heeley, director of Middle East and defense policy at the Washington, D.C.-based Center for Arms Control & Non-Proliferation.

On April 29, United Nations Secretary-General Ban Ki-moon appealed to Syria to allow a team of analytical chemists and other experts into the country to investigate all allegations of chemical weapons use. “A credible and comprehensive inquiry requires full access to the sites where chemical weapons are alleged to have been used,” Ban said.

U.S. intelligence, to date, indicates sarin to be the chemical weapon used.

The White House says its tentative assessment that the weapons were used was partly based on “physiological samples,” most likely blood samples collected from victims of attacks, experts say. The British and French governments say their claims stem from a range of evidence, including soil samples, witness interviews, and accounts by medical experts who observed victims’ symptoms.

But to conclusively determine whether chemical weapons have been used, experts say the UN fact-finding team must gather its own physical evidence and examine in UN certified laboratories samples of soil, water, blood, and tissue taken from people and from sites in or near the alleged attacks.

It is sometimes difficult to detect sarin in tissue directly, says the Organisation for the Prohibition of Chemical Weapons, a UN-affiliated group. But in victims, lowered activity of cholinesterase in the blood—sarin inhibits the enzyme—is a good index of exposure, the group says.

“What’s ideally needed is for the international inspection team to retrieve samples themselves, investigate the sites for any forensic evidence of weapons usage, interview witnesses and victims, and review autopsy and medical reports,” says Paul F. Walker, director of environmental security and sustainability at Green Cross International, a Geneva-based group that works to eliminate weapons of mass destruction.

The chain of custody for the samples would also have to be verified. “The problem with the samples the U.S., U.K., and France used is that the full chain of custody is not known,” Walker says. “This raises questions as to whether they could have been tampered with or not, where they actually originated, and who possessed and fired the chemical agents.”

He notes that the 1997 Chemical Weapons Convention, which bans the production and use of chemical warfare agents, includes extensive rules for conducting on-site inspections in cases of suspected use. Syria has not signed the treaty.

Assad himself has asked the UN to investigate his government’s claim that opposition forces used chemical weapons during fighting in the town of Khan al-Asal near Aleppo on March 19. The rebels have said that government forces used chemical weapons in the battle.

The U.K. and France have also asked the UN to investigate alleged use of chemical weapons in and around the cities of Aleppo, Homs, and Damascus. Syria wants only the Khan al-Asal incident investigated.