Chemical Warfare Agents

The Sarin gas attack that occurred in a Tokyo subway in 1994 and an earlier such terrorist incident in Matsumoto, Japan, added a new dimension to the threat of chemical agents. In the hands of terrorists, these agents pose a real threat to the population...


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The Sarin gas attack that occurred in a Tokyo subway in 1994 and an earlier such terrorist incident in Matsumoto, Japan, added a new dimension to the threat of chemical agents. In the hands of terrorists, these agents pose a real threat to the population, and almost any public area is vulnerable.

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Photo courtesy of FEMA/CSEPP Protective Clothing Training Course.
Military chemical protective clothing.

Emergency responders may be faced with hundreds and even thousands of casualties. Firefighters and EMS personnel may be unprepared to deal with chemical agents and their victims released in a terrorist attack. In the Tokyo attack, medical personnel and emergency responders didn't realize the source of the victims' medical problems until some time had passed; no decontamination was performed.

Chemical warfare agents were introduced during World War I and were used as recently as the Persian Gulf War. These agents have been stockpiled at seven sites in the mainland United States and on Johnston Island in the South Pacific since World War I.

The U.S. stockpiles of "unitary" chemical warfare agents have been slated for destruction as a result of international treaty by the year 2004. (Unitary agents are those that act on their own without having to be mixed with another chemical to be activated.) Many of the aging munitions have experienced leaks of chemical agents at some of the facilities, although to date no off-post releases of any significance have occurred.

The U.S. Army and Federal Emergency Management Agency (FEMA) are coordinating efforts to ensure public safety in the event an accident occurs involving any stockpiled chemical agents. This cooperative effort is the Chemical Stockpile Emergency Preparedness Program (CSEPP). Emergency responders in areas likely to be affected by a release are trained in chemical agent awareness, emergency medical treatment and response procedures including personal protective equipment (PPE) and decontamination. Chemical agents also have been found around the country in unexploded munitions buried on and off present and past military installations.

There are two primary types of chemical agents: mustard and nerve. Mustard agents are also referred to as vesicants or blister agents because they form blisters when they contact the skin. The two types of mustard agent are sulfur mustard and nitrogen mustard. Nitrogen mustard is similar to sulfur mustard as far as its health effects but has slightly more systemic effects (affecting the entire body).

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Photo by Robert Burke
Commercially available chemical protective clothing with a military hood.

Mustard is often incorrectly referred to as "mustard gas." Mustard agent is a viscous oily liquid, light yellow to brown in color, with an onion, garlic or mustard smell and it freezes at 57 degrees Fahrenheit. Mustard is usually non-volatile but may produce a vapor hazard in warm weather or when involved in a fire. The vapor is heavier than air, with a density of 5.4. Mustard agent is heavier than water and non-soluble in water.

There are three basic types of blister agents: sulfur mustard, lewisite and phosgene oxime. Mustard agent is designed to function through skin and tissue contact and generally is not a major inhalation hazard under normal conditions.

Vesicants are persistent agents, which means they do not readily vaporize and will remain as contaminants for long periods. Mustard agents do not cause pain on contact and do not act immediately; instead, there is a dormant period of one to 24 hours before symptoms present themselves. Symptoms of mustard exposure include: erythema (redness of the skin), blisters, conjunctivitis (eye inflammation) and upper respiratory distress; the symptoms may worsen over several hours. Once mustard has contacted tissues, the damage has already started, although there may not be any indication that contact has occurred. Mustard is highly soluble in fat, which results in rapid skin penetration.

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