Chemical Warfare Agents
Chemical warfare agents (CWAs) are chemicals designed to incapacitate, seriously injure, or kill people through their physiological effects. They can be deployed as either liquid aerosols or vapors. There are three major routes of exposure to chemical warfare agents: skin (liquid and high vapor concentrations), eyes (liquid or vapor), and respiratory tract (vapor inhalation). Chemical agents are usually divided into four categories: nerve agents (e.g., sarin, VX, tabun), blister agents (e.g., sulfur mustard, nitrogen mustard, Lewisite), choking agents (e.g., phosgene, chlorine), and blood agents (e.g., hydrogen chloride, arsine).
Nerve agents, discovered by the Germans in the 1930’s and developed during World War II, are the most dominant chemical warfare agents. They affect the transmission of impulses in the nervous system by blocking acetylcholinesterase enzyme. Nerve agents have an organo-phosphorus chemical structure, similar to the insecticides and pesticides from which they were developed. The “G” agents tend to be non-persistent whereas the “V” agents are persistent. Nerve agents are highly toxic, easily dispersed, highly stable and rapid acting when adsorbed through the skin or through the respiratory system. They are 100 to 1000 times more lethal than blister, choking or blood agents. They are most useful to terrorists because of the small quantity needed to inflict a substantial amount of damage. It has been said that sarin and VX (the most toxic nerve agents) can be synthesized by a moderately competent organic chemist with limited laboratory facilities.
Blister (vesicant) agents such as mustard were extensively used during WWI. They produce painful burns of the skin and respiratory track by rapidly generating a highly toxic intermediate episulfonium ion, which irreversibly alkylates DNA, RNA, and protein, disrupting cell function and causing cell death. Within two minutes, a drop of mustard on the skin can cause serious damage. They are intended to incapacitate rather than kill; however, respiratory exposure to these agents can be fatal.
Blood agents are not suited for use on large numbers of people, and so their primary role is in assassinations. Choking agents were the agents most used during WWI, but have lost much of their usefulness since the development of nerve agents.
