- Knowledgebase: Biological & Chemical Warfare and Terrorism
- Answers to questions about Biological and Chemical terrorism and warfare.
- 12. Chemical Warfare Agents: From MS Encarta - Top
- Chemical warfare agents can be grouped into two general types: those that affect the body surfaces they contact, and those that damage the general nervous system.
Surface agents include phosgene gas, chlorine gas, hydrogen cyanide, and mustard gas. The principal action of phosgene, chlorine, and hydrogen cyanide occurs through inhalation. Phosgene is a choking agent that causes the lungs to fill with water, while chlorine destroys the cells that line the respiratory tract. Hydrogen cyanide blocks oxygen from reaching the blood. Mustard gas is actually composed of tiny droplets of liquid that are dispersed in the air, where they are inhaled like a gas. Mustard is a blistering agent that damages any surface it contacts, including the skin, eyes, and lungs. It may cause death by respiratory failure. See also Tear Gas.
Nerve agents act by blocking the transmission of nerve messages throughout the body. These agents include sarin, soman, tabun, and VX. All act by disrupting the normal action of a neurotransmitter called acetylcholine. Whether inhaled or absorbed through the skin, a single drop of nerve agent can shut down the body's nervous system. The most powerful of this group is VX, but all can cause death within minutes after exposure. See also Nerve Gas.
Herbicides, such as Agent Orange, are chemicals that kill vegetation. Agent Orange was used during the Vietnam War (1959-1975) as a defoliant, destroying jungle leaves to expose enemy troops. Some people regard herbicides as chemical weapons if used for hostile purposes, but there is no universal agreement about this, since herbicides are not directly intended to harm humans or animals. However, veterans of the Vietnam War suffered several health problems blamed on exposure to Agent Orange and other toxins.
Early Development
Large-scale use of chemical weapons first occurred in 1915 during World War I, when German troops released chlorine gas from cylinders as the wind blew toward French lines a few hundred yards away. The yellow-green cloud enveloped the French soldiers, who choked and panicked. As the war continued, phosgene and other chemical weapons were used, culminating with Germany's introduction of mustard gas in 1917. By the end of the war in 1918, all the major powers had used chemical weapons.
The suffering caused by the gas attacks led to the 1925 Geneva Protocol, which banned the use of chemical or bacteriological agents in war. Although most major countries became parties to the agreement, the United States declined to until 1975. Nevertheless, the Protocol encouraged an international norm that helped deter the use of these weapons.
Recent Developments
Use of poison weapons has been alleged in only a few of the hundreds of wars and skirmishes since World War I—and has been verified in even fewer. The handful of proven cases include Italy's limited use of chemical arms against Ethiopia in the 1930s, and Egypt's use of chemical agents against Yemen in the 1960s. But the international agreement to eschew such weapons was most flagrantly violated by Iraq during the Iran-Iraq War. Although Iraq denied using chemical weapons, United Nations (UN) inspectors repeatedly found Iraqi forces were doing so. Still, no international agency or country tried to stop Iraq's actions. As a result, in the 1991 Persian Gulf War, which pitted Iraq against an alliance led by the United States, many nations that had been silent about Iraq's actions faced an Iraqi army equipped with biological and chemical weapons.
Ground fighting in the Gulf War lasted only a few days, and Iraq apparently did not fire any chemical or biological agents, but the experience prompted renewed attention to the problem of such weapons. In 1995, a Japanese cult called Aum Shinrikyo released sarin nerve agent in the Tokyo subway, killing 12 people and injuring 5500. Cult leaders reportedly told authorities that their choice of weapon was inspired by publicity about Iraq's chemical arms.
- Updated: October 22, 2001
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