The Syrian civil war reached a nadir on August 21 when rockets with toxic chemical agents were launched at the suburbs of the Ghouta region just outside the capital city of Damascus. Officials have not yet confirmed how many died as a result of the chemical attack, but more than 100,000 lives have been claimed by the overall uprising since it broke out two years ago between supporters of Pres. Bashar al-Assad’s regime and those who called for his expulsion.
United Nations inspectors working to determine the nature of the deadly agents used in last week’s attack have faced multiple challenges, including delays in reaching the site where the blasts occurred. Having originally granted investigators permission to access the site on August 25, Syrian officials later said the team could not enter until 24 hours later. On August 26 the team managed to reach the site after coming under fire from unidentified snipers.
The setback could prove disastrous if the chemical remains of the weapons have evaporated or expired. But if perpetrators used a persistent nerve agent such as sarin, traces of the toxin should linger in the soil for up to 29 weeks.
Scientific American spoke with Charles Blair, senior fellow on state and nonstate terrorist threats with the Federation of American Scientists, about the challenges of pinning down a toxic culprit.
[An edited transcript of the interview follows.]
What happened at 2:00 A.M. in the Ghouta region of Syria on Wednesday, August 21?
There are some visuals, but apparently there were thuds or explosions releasing a chemical agent that was dispersed throughout the area, harming a large number of people in a small space. That begins the debate: What was it? There will never be a definitive answer. The U.N. team’s only charge was determining if there was a chemical agent or not, not who delivered it. But it’s pretty safe to say the attack was chemical. The battle is what people consider counts as proof.
What kind of testing is done to find out what chemicals were used in the attack? Is it all done on-site?
The team that goes in can either do on-site testing or they can take it to one of 20 facilities outside the country that are certified to conduct off-site testing. One of the benefits of off-site testing is that the devices there are usually more advanced. Usually they do a combination of both. So in this case you take a sample and split it into eight [parts], which are then sealed to prevent contamination. Two of the eight [parts] are analyzed on-site. One goes to the inspector state party, and one is sent to be analyzed off-site. Each sample is weighed and reweighed before and after shipment to ensure no tampering takes place.
The samples then go through gas chromatography–mass spectrometry (GC–MS) analysis, which breaks down the sample into its various chemicals. Then they identify them by comparing what they have with a database of more than 2,000 chemicals. [Editor’s note: A GCMS instrument comprises two parts. The gas chromatography (GC) component separates the chemical mixture into pure chemicals based on the ease with which they evaporate; the mass spectrometer (MS) identifies and quantifies the chemicals based on their structures.]
Is there an expiration date for detection of these chemicals?
If it was sarin, they have 29 weeks to detect the degradation components. There have been rumors that it’s too late to detect or that sarin evaporates. What happens is it goes into the soil. If there were bursts of sarin in the area say, nearby a crater, the bottom of that crater would be a great place to find sarin remnants. With such a large number of people killed in this attack, there is evidence that large amounts of the chemical—if it was sarin—was used. I expect it lingered in certain areas.