Sarin in chemical attacks

DEFINITION: Highly toxic liquid substance used as a chemical weapon.

SIGNIFICANCE: Concerns that terrorists could employ sarin in chemical attacks have increased law enforcement agencies’ attention to this substance. The United Nations classifies sarin as a weapon of mass destruction.

Sarin was discovered in the 1930s during a search for new insecticides. Its extreme toxicity to humans led to its development as a chemical weapon by Nazi Germany and other nations, and huge quantities were manufactured and stored. In the 1980s and later, sarin was used several times in chemical warfare and in terrorist attacks. The United Nations’ Chemical Weapons Convention of 1993 bans the manufacture and storage of chemical weapons, including sarin, which is also known as isopropyl methylphosphonofluoridate, or GB. Various nations, including the United States and Russia, gradually destroyed stockpiles of munitions with sarin in accordance with the Chemical Weapons Convention. In 2023, the last chemical weapon from the world’s declared chemical weapons stockpiles was verified as destroyed when the United States destroyed its final munition, an M55 rocket containing GB . However, this does not take into account the unknown stock of sarin and other chemical weapons. The United States has taken significant steps to provide members of its armed forces with means of protection from sarin attacks.

Toxic Effects

A so-called nerve gas, sarin is one of several chemical agents that exert toxic effects through the ability to bind to and inactivate the vital enzyme acetylcholinesterase (AChE). AChE exists in nerves and acts as a catalyst for the hydrolysis of acetylcholine, the chemical that is released at nerve endings and that causes muscle contraction. Only a small amount of AChE is present in nerves, but it is very effective in catalyzing the destruction of acetylcholine.

When AChE is inactivated by sarin or a similar nerve agent, the acetylcholine builds up and causes uncontrolled muscle contractions. Symptoms of poisoning by sarin include pain in the eyes, blurred vision, a runny nose, incontinence, respiratory failure, convulsions, coma, and death. The eyes are particularly sensitive; the pupils react to sarin by shrinking to pinpoints (miosis). Sarin absorbed through the skin or inhaled as vapor or aerosol is toxic to different degrees, depending on exposure.

Dispersal

Sarin may be dispersed as a vapor or as an aerosol. The volatility of sarin permits a significant concentration of vapor at ambient temperatures, but this volatility also means that it may not persist in the environment. Toxic concentrations are more effectively achieved in confined spaces. For example, in 1995, members of a Japanese doomsday cult left punctured bags of liquid sarin in train cars, where the fumes quickly caused passengers to choke and vomit. Thirteen people died, while at least 5,800 were injured in five coordinated attacks in Tokyo. Some were left blind and paralyzed.

Aerosol dispersal of sarin, which requires some type of sprayer, can achieve higher concentrations than vapor dispersal. All types of dispersal tend to leave traces of sarin or its degradation products on surfaces, including clothing, from which forensic samples may be obtained for identification.

Detection and Treatment

Methods for the detection of sarin in military situations include test papers, test kits, and electronic devices. The M8 test paper for soldiers is impregnated with three dyes and responds with three color changes characteristic of different classes of chemical warfare agents. The M256A1 test kit contains a simple apparatus for sampling and applying chemical tests. Among more sophisticated methods are those that use small mass spectrometers, about the size of a brick; these devices can sample the ambient air directly and detect individual compounds. Even smaller detectors that use AChE on a silicon chip or compounds with fluorescence that react to nerve agents have also been developed.

Treatment of sarin poisoning follows removal of the victim from contaminated clothing and all other contact with the toxic substance. Atropine may be given by injection to provide some relief from symptoms, as it inhibits the binding of excess acetylcholine at some receptors. Diazepam may be administered to control the muscular spasms caused by the nerve agent, and pralidoxime methanesulfonate (P2S) is helpful in removing it from AChE.

Prophylaxis consists of drugs administered before sarin exposure occurs to increase resistance and reduce the severity of possible symptoms. Among the drugs used are atropine and pyridostigmine bromide.

Bibliography

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