Chemical agents which attack lung tissue, primarily causing pulmonary oedema, are classed as lung damaging agents. Choking agents are substances that cause physical injury to the lungs. Exposure is through inhalation. In extreme cases, membranes swell and lungs become filled with liquid (pulmonary edema). Death results from lack of oxygen; hence, the victim is ďchokedĒ. Chlorine (CL) is a choking agent. Symptoms include irritation to eyes/nose/throat, respiratory distress, nausea and vomiting, burning of exposed skin. Pulmonary edema and frothy sputum may be observed Choking Agents are typically colorless liquid to white cloud which turns into a vapor. The distinctive smell is like freshly mown hay, grass, or corn.
In low concentration, choking agents produce an action on the respiratory system that results in the accumulation of fluid in the lungs. Accumulation of fluid in the lungs can cause death. High concentrations produce death for the same reason, but the upper respiratory tract may be involved as well. Exposure to choking agents may produce immediate dryness of the throat, coughing, choking, tightness across the chest, headache, nausea, and at times, irritated and watery eyes. However, symptoms are usually delayed, and itís possible that no immediate symptoms will appear when exposed to a fatal dose.
Even a mild exposure to a choking agent that is accompanied by immediate symptoms may cause fluid to accumulate in the lungs within 2 to 24 hours after exposure. Shallow and rapid breathing, a hacking and painful cough, frothy saliva, and an ashen gray color of the skin indicate the presence of fluid in the lungs. After exposure to a high dose of a choking agent, itís important to begin medical treatment quickly to prevent accumulation of fluid in the lungs. Itís important to keep the victim at rest and warm. Cough suppressant and pain relievers can be given as long as the doses donít interfere with respiratory functions.
John Stenhouse, a Scottish chemist and inventor, synthesized chloropicrin in 1848. Chloropicrin is currently used as a soil fumigant used for its broad biocidal and fungicidal properties. As a CW agent, chlorpicrin was first used by Russia during World War I, and was eventually delivered in artillery shell sand cylinders by all sides. Known to the British as "vomiting gas," the French as "Aquinite," and "Klop" by the Germans, chloropicrin has an intense odor, which is a distinctive warning property.
During World War I, its use was often coupled with other agents because the agent often broke through gas mask filters, making soldiers vulnerable to other gasses. Chloropicrin is a colorless-to-light green oily liquid that is an irritant to all body surfaces. At 1 part per million (ppm), the victim experiences irritation with pain in the eyes; at 4 ppm exposed individuals are incapacitated; and at 20 ppm the victim has definite bronchial or pulmonary lesions. Overexposure leads to irritation of the nose and throat leading to coughing, labored breathing, sore throat, dizziness, bluish skin, vomiting and in some instances chemical pneumonitis and pulmonary edema. Skin contact can lead to chemical burns-exposure through damaged skin causes similar symptoms as those resulting from inhalation and prolonged eye exposure can result in blindness.
Because of its strong odor, wide use in commercial applications and being one-fourth less toxic than phosgene, chloropicrin has not received the same attention as more potent CW agents. Although not flammable, chloropicrin presents a significant explosion hazard if involved in a fire and bulk containers are shock sensitive and can detonate. Chloropicrin decomposes in the environment.
Liquid at room temperature, diphosgene is easier to handle than phosgene and is more persistent than chlorine or phosgene. The German army first used diphosgene during World War I in May 1916. Diphosgene is a colorless liquid that emits an odor similar to green corn or new mown hay. A lethal dose is 3,000mg∑min/m3 for 50 percent of resting adults exposed to the gas. Symptoms can be delayed three hours or more, though immediate symptoms may appear after exposure to high concentrations of diphosgene. Essentially, the body turns diphosgene into phosgene, producing the same results as if the victim were exposed to phosgene gas. Because diphosgene has a strong tearing effect, it has less surprise value than phosgene when used on troops. In addition, it's lower volatility makes it more difficult to set up an effective surprise concentration.
Perfluoroisobutylene is an industrial gas that is a byproduct of the overheating and during the production of Teflonģ. PFIB has the potential to be an asphyxiating weapon, causing pulmonary edema even in low concentrations. The effects of exposure of PFIB, called "polymer fume fever," begin to appear one to two hours after exposure and is often mistaken for influenza. Like phosgene, however, severe symptoms appear suddenly over 24 to 48 hours after exposure. Exposure to PFIB can result in pulmonary edema. Because of its high toxicity the United Kingdom brought PFIB to the attention of the Conference on Disarmament in 1989 and it was entered as a restricted chemical under the CWC.
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