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Lewisite (L)
 Chemical structure of lewisite |
It was during World War I (WWI) that modern military chemical warfare emerged. Once immersed in that “Great Conflict,” the United States’ need for chemical warfare research became a priority and the U.S. Chemical Warfare Service (CWS) was established. (For more information, see Featured Article Chemical Warfare in World War I.) The need for research chemists quickly grew, and, before the war’s end, more than 10 percent of all chemists in the United States become involved in this effort.
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One of those chemists was Winford Lee Lewis, who became director of the offensive branch of the CWS unit at Catholic University in Washington, D.C. This unit was charged with developing and producing novel gases, with particular focus on compounds containing arsenic. In the course of his research, Lewis reviewed the dissertation of a former doctoral student who was attempting to synthesize rubber. The student had found that reacting arsenic trichloride and acetylene in the presence of aluminum trichloride resulted in a toxic product, which had caused him to become seriously ill. Lewis re-created and refined this experiment, creating a prototype chemical weapon agent.
The toxic substance developed by Lewis was named “lewisite” after him. It was given the military designation “L”. The government officially ordered Lewis to cease working on lewisite, publicly claiming that it was ineffective. This was done in the hope of convincing German spies that Lewis’s research had not been productive. Privately, however, research on lewisite continued and was transferred to nearby American University.
Lewisite had also been independently discovered, although not manufactured, in Germany during WWI. During World War II, the United States, Great Britain, Germany, the Soviet Union, and Japan all produced lewisite. Since then, other countries are known or suspected to have produced lewisite, including Iraq, North Korea, and possibly Libya, but there have been no known uses of lewisite on the battlefield.
Lewisite is a vesicant, or blister agent, that also acts as a systemic poison. Pure lewisite is an oily, colorless liquid, but it usually contains minor impurities that give it a brownish color and an odor similar to geraniums. Lewisite is not found naturally in the environment. It was developed as a chemical warfare agent, and has no medical or other practical use.
As a weapon, lewisite would most likely be released as an aerosol. Once released, it is persistent, potentially lasting in the environment for six to eight hours in sunny weather, and even longer in cold, dry climates. Lewisite vapor is about seven times heavier than air, and therefore can hover close to the ground.
Effects of exposure to lewisite usually begin immediately. Irritation and pain in the skin occurs within seconds to minutes, and blisters begin to form within several hours. Irritation, pain, swelling, and tearing of the eyes may also occur on contact. Inhalation of lewisite vapor affects the respiratory tract, causing runny or bloody nose, sneezing, coughing, hoarseness, sinus pain, and shortness of breath. Diarrhea, nausea, vomiting, and low blood pressure may also occur. Lewisite can be fatal in as little as ten minutes when inhaled in high concentrations.
The blisters caused by lewisite exposure heal much faster than those caused by other vesicants, such as sulfur and nitrogen mustards, and extensive skin burning is less likely. However, extensive inhalation of lewisite vapor may cause chronic respiratory disease, and severe eye exposure may cause permanent blindness.
Victims of lewisite exposure are treated by decontamination as soon as possible, and supportive medical care in a hospital setting. Skin can be decontaminated with soap and water. An antidote injection for lewisite, called dimercaprol or BAL, exists but, due to toxic side effects, should only be used for severe, life-threatening exposures.
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