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HISTORY AND EPIDEMIOLOGY
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The first well-documented intentional use of chemicals as weapons occurred in 423 B.C. when Spartans besieging Athenian cities burned pitch-soaked wood and brimstone to produce sulfurous clouds.88 Large-scale chemical warfare began in World War I when the Germans released chlorine near Ypres, Belgium, killing hundreds of people and forcing 15,000 troops to retreat.19,48 Both sides rapidly escalated the use of toxic gases released from cylinders or by artillery shells, including various pulmonary irritants, lacrimators, arsenicals, and cyanides.
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The Germans first used sulfur mustard in 1917, again near Ypres, and caused more than 20,000 deaths or injuries.48 The Allies soon responded in kind. Sulfur mustard was unequaled in its ability to incapacitate opponents, often resulting in temporary blindness.9 Injuries far outweighed fatalities, diverting manpower and resources to care for the wounded. By the end of the war, chemical weapons caused more than 1.3 million casualties and approximately 90,000 deaths.19
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Germany began producing nerve agents just before World War II. Tabun was developed in 1936 by Gerhard Schräder when conducting insecticide research for IG Farbenindustrie.30,78 Sarin was synthesized in 1938.30 Between 10,000 and 30,000 tons of tabun and 5 to 10 tons of sarin were produced during World War II. Soman was synthesized in 1944, but no large-scale production facilities were developed. When the Allies discovered these chemical weapons at the end of the war, code names were designated based on the order of their development. Tabun was called GA (the letter G standing for German), sarin was GB, and soman was GD.30
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In 1952, the British synthesized an even more potent nerve agent while searching for a dichlorodiphenyltrichloroethane (DDT) replacement. This substance was given to the United States for military development and was named VX. The Russians developed a similar nerve agent, variably referred to as VR or “Russian VX.”38 The United States used defoliants and riot control agents in Vietnam and Laos. Iraq used sulfur mustard, tabun, and soman during its war with Iran in the 1980s and may have also used cyanide against the Kurds.48 More recently, chlorine and sarin were used by government forces in the Syrian civil war, and the Islamic State used sulfur mustard in Syria and Iraq.87
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Terrorist groups have also used chemical weapons. Sarin was released twice by the Aum Shinrikyo cult in Japan. The first release occurred in Matsumoto in 1994, killing seven and injuring more than 600.51 A more highly publicized sarin release occurred in the Tokyo subway system in 1995, killing 12 and resulting in more than 5,000 persons seeking medical attention.75 Cult members have also used VX in assassinations.50 Chemical weapons are particularly appealing to terrorist groups because the technology and financial outlay required to produce them is much less than for nuclear weapons, and the potential morbidity, mortality, ...