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 1930's 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 1980's and later, sarin was used several times in 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—have been gradually destroying stockpiles of munitions with sarin in accordance with the Chemical Weapons Convention. The United States has taken significant steps to provide members of its armed forces with means of protection from sarin attacks.
A so-called nerve gas, sarin is one of several Page 848 | Top of Articlechemical 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 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, runny nose, incontinence, respiratory failure, convulsions, coma, and death. The eyes are particularly sensitive; the pupils react to sarin by shrinking to pinpoints (meiosis). Sarin absorbed through the skin or inhaled as vapor or aerosol is toxic to different degrees, depending on exposure.
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.
Sidebar: HideTerror Attacks in Japan
In November, 1994, members of the religious movement Aum Shinrikyo sprayed sarin aerosol near a pond in a park in the city of Matsumoto in Japan. Sarin's precursor chemicals, such as isopropanol, trimethylphosphite, methyl iodide, and sodium fluoride, have legitimate industrial uses, and in 1994 it was possible for individuals to purchase these materials openly (access to many has since been restricted). The cult members had obtained chemicals sufficient to prepare sarin in quantity. In the Matsumoto attack, 5 people were killed and 274 were injured. The police were initially unsure what had happened, but eventually forensic investigators detected sarin in the water of the pond.
A few months later, on March 20, 1995, Aum Shinrikyo carried out a sarin attack on three major lines of the Tokyo subway system; the terrorists boarded subway trains and punctured plastic bags of impure sarin. This time it took police investigators only two hours to collect a sample and identify sarin using the method of gas chromatography-mass spectrometry (GC-MS). The attack killed 12 people and injured thousands. The dead exhibited extreme lividity, bronchial congestion, meiosis, and pulmonary edema. Some victims showed reduced cholinesterase activity in the blood. This attack stimulated research on forensic methods for detecting nerve agents and on possible courses of treatment for poisoning by such agents.
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 agent. 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. Also under development are even smaller detectors that use AchE on a silicon chip or compounds with fluorescence that reacts to nerve agents.
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 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.
John R. Phillips
Croddy, Eric A., with Clarisa Perez Armendariz and John Hart. Chemical and Biological Warfare: A Comprehensive Survey for the Concerned Citizen. New York: Copernicus Books, 2002. Addresses the uses of sarin and other nerve agents as weapons.
Marrs, Timothy C., Robert L. Maynard, and Frederick R. Sidell, eds. Chemical Warfare Agents: Toxicology and Treatment. 2d ed. Hoboken, N.J.: John Wiley & Sons, 2007. Presents a technical discussion of the factors affecting the toxicity of agents. Includes description of tests done with sarin on volunteers.
Mauroni, Al. Chemical and Biological Warfare: A Reference Handbook. 2d ed. Santa Barbara, Calif.: ABC-CLIO, 2007. Comprehensive survey of chemical and biological weapons includes a valuable annotated bibliography that includes citations to Internet sites.
Suzuki, Osamu, and Kanako Watanabe, eds. Drugs and Poisons in Humans: A Handbook of Practical Analysis. New York: Springer, 2005. Collection of highly technical articles discusses analytic techniques. Includes information on procedures for the analysis of sarin and its degradation products through gas chromatography and mass spectrometry.
Tucker, Jonathan B., ed. Toxic Terror: Assessing Terrorist Use of Chemical and Biological Weapons. Cambridge, Mass.: MIT Press, 2000. Presents twelve case studies of the use of chemical and biological agents by terrorist groups, identifying terrorists' patterns of behavior and strategies to combat them.
White, Peter, ed. Crime Scene to Court: The Essentials of Forensic Science. 2d ed. Cambridge, England: Royal Society of Chemistry, 2004. General work provides good discussion of forensic science principles.