Tabun in chemical attacks
Tabun is a highly toxic liquid classified as a chemical warfare agent, first discovered in the 1930s during efforts to create new insecticides. As the earliest and one of the most easily manufactured nerve agents, concerns about its potential use have grown, particularly in light of terrorist threats. The manufacture and storage of tabun are prohibited under the United Nations Chemical Weapons Convention of 1993. Historically, tabun was produced in large quantities by Nazi Germany during World War II but was not deployed in combat. However, it was used by Iraq against Iranian troops during the Iran-Iraq War, leading to documented cases of exposure and poisoning. Tabun functions by inhibiting the enzyme acetylcholinesterase, causing a dangerous buildup of acetylcholine in the nervous system, which can result in severe symptoms including respiratory failure and death. Detection and treatment methods for tabun exposure have been developed, including advanced analytical techniques for identifying the agent in biological samples and medical treatments that must be administered promptly to counteract its effects.
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Tabun in chemical attacks
DEFINITION: Highly toxic liquid used as a chemical warfare agent.
SIGNIFICANCE: Concerns that terrorists could employ chemical agents in attacks have increased law-enforcement agencies’ attention to substances such as tabun. The manufacture and storage of tabun were banned by the United Nations Chemical Weapons Convention of 1993.
Tabun, which was discovered in Germany in the 1930s during a search for new insecticides, is the earliest and most easily manufactured of the so-called nerve gases. Although it has been superseded as a chemical weapon by agents such as VX, its relative ease of manufacture makes it attractive to some nations that might consider using it as a weapon.
Tabun was manufactured and stored in multiton quantities in Nazi Germany during World War II, but it was never used in combat. During the Iran-Iraq War (1980-1988), however, Iraq did use the agent against Iranian troops in a 1988 chemical attack. In 1994, a team sent to Iran by the United Nations found tabun in a dud bomb that Iraq had dropped inside Iran’s borders. The team also visited a field hospital where several patients were recovering; they exhibited symptoms consistent with poisoning by tabun, although no detailed tests were done.
Like other organophosphorus nerve agents, tabun is an inhibitor of the vital enzyme acetylcholinesterase (AChE). When tabun is absorbed through the skin or the vapor or aerosol of the agent is inhaled, the chemical binds to AChE. The normal function of AChE is to catalyze a reaction that removes acetylcholine from the nerve endings, where it activates muscle contraction. Inhibition of the enzyme allows accumulation of acetylcholine, which causes sweating, runny nose, incontinence, visual impairment (including pain and contraction of the pupils, or meiosis), respiratory failure, convulsions, coma, and death. The degree of danger depends somewhat on the mode of exposure and the weight of the individual, but very small amounts of nerve agents such as tabun are toxic.
Signs of exposure to tabun in victims include abnormally low AChE levels in the blood. Traces of the agent may also be found in the victims’ bodies. Methods have been developed for detecting nerve agents in biological samples at the picogram level using gas chromatography-mass spectrometry (GC-MS) or capillary gas chromatography. Members of the American armed forces use a handheld device, the monitor (CAM), that detects nerve agents under field conditions through ion mobility spectrometry.
Treatment of nerve agent poisoning involves injections of atropine and administration of pralidoxime chloride (2-PAM chloride). The oxime tends to displace the nerve agent from the AChE, but it must be given quickly, because a reaction known as aging soon makes the AChE-nerve agent combination irreversible. Drugs given before exposure (prophylaxis) include carbamates (physostigmine, pyridostigmine) and enzymatic organophosphate scavengers.
Bibliography
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