Sat, Sep 21, 2013 - Page 9 News List

Sarin gas: history of a chemical weapon

The UN has confirmed that the deadly nerve agent sarin was used to kill hundreds of Syrians last month. The history of this weapon’s use is a global story and often chilling

By Ian Sample  /  The Guardian

Illustration: Kevin Sheu

Now we know. On the morning of Aug. 21, as the air above Damascus cooled, rockets filled with the nerve agent sarin fell on rebel-held suburbs of the Syrian capital and left scores of men, women and children dead or injured. UN inspectors had been in the country for three days, on a mission to investigate allegations of earlier atrocities. They quickly changed tack. They brokered a temporary ceasefire with the regime and the rebels and made straight for Ghouta. Video reports from the area showed hospital staff overwhelmed and desperate.

Never before had UN inspectors worked under such pressure and in the midst of a war zone. The small team, headed by the Swedish chemical weapons expert Ake Sellstrom, was threatened with harm. Their convoy was shot at. However, their 41-page report was completed in record time.

Sarin was that breed of accident that scientists come to regret. Its inventors worked on insecticides made from organophosphate compounds at the notorious IG Farben chemical company in Nazi Germany. In 1938, they hit on substance 146, a formula that caused massive disruption to the nervous system. The chemical name was isopropyl methylfluorophosphate, but the company renamed it sarin to honor the chemists behind the discovery — Schrader, Ambros, Ritter and van der Linde — according to Benjamin Garrett’s 2009 book A to Z of Nuclear, Biological and Chemical Warfare. The chemical they created had the grim distinction of being many times more lethal than cyanide.

Substance 146 is not hard to make, but it is hard to make without killing yourself. There are more than a dozen recipes that lead to sarin, but all require technical know-how, proper lab equipment and a serious regard for safety procedures. One major component is isopropanol, more commonly known as rubbing alcohol. Another is made by mixing methylphosphonyl dichloride with hydrogen or sodium fluoride. Methylphosphonyl dichloride is not easy to come by. Under the Chemical Weapons Convention it is listed as a schedule 1 substance, making it one of the most restricted chemicals in existence.

Last year, the US and other countries stepped up efforts to block sales to Syria of chemicals that might be used to make sarin. But the country had already amassed substantial stocks of the precursors needed to make the agent. This month, it emerged that Britain had approved export licenses to Syria for the sale of more than four tonnes of sodium fluoride between 2004 and 2010, although business secretary Vince Cable said there was no evidence they had been used in the Syrian weapons program. The exports came on top of sales approved last year for sodium and potassium fluoride under licenses that were later revoked on the grounds that they could be used in the manufacture of weapons.

Though referred to as a nerve gas, sarin is a liquid at temperatures below 150C°. To maximize its potential as a weapon, the substance is usually dispersed from a canister, rocket or missile in a cloud of droplets that are fine enough to be inhaled into the lungs. Inevitably, some evaporates into gas, much as spilled water turns into vapor. The chemical enters the body through the eyes and skin too. Sarin has no smell or taste and is colorless, so the first people may know of its use is when victims start to fall.

Sarin takes such a dreadful toll on the body by interfering with a specific, but crucial aspect of the nervous system. It blocks an enzyme called acetylcholinesterase, with devastating consequences. Nerves that usually switch on and off to control muscle movements can no longer be switched off. Instead, they fire constantly. There are mild effects: the eyes become irritated, the vision blurred; people’s pupils shrink, they drool and vomit. Then there are the lethal effects. Breathing becomes labored, shallow, erratic. Unable to control their muscles, victims have convulsions. The lungs secrete fluids and when people try to breathe, foam comes from their mouths, often tinged pink with blood. A lethal dose can be as small as a drop and can kill in one to 10 minutes. If people survive the first 20 minutes of a sarin attack, they are likely to live.

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