Part Two

The Nature of Chemical Weapons

Chemical weapons, or chemical warfare agents, come in only three basic forms: solids, liquids, and gases. Each form has its own particular features that both favour and disfavour its use. Solids tend to be persistent, but they are immobile and once identified can be easily contained or avoided. Liquids can also be quite persistent, and they are also fairly mobile, but this also makes them more readily countered by expedient measures and they are more subject to environmental conditions. Gases are the most mobile of chemical agents, making their deployment the most rapid and versatile, but they are so subject to air movement and quick dilution effects that they are also the least persistent in effective concentrations.

Chemical agents in use to World War II were primarily industrial chemicals. That is, chemicals that were available in quantity because of their legitimate fundamental industrial uses, and which were diverted for use as military weapons because of their known toxic effects. Chlorine, phosgene, and hydrogen cyanide are prime examples. Phosgene and chlorine, both used in chemical weapons as choking agents, are important in industry as chlorinating agents, bleaches, and structural modifiers. Hydrogen cyanide, whose poisonous character in the blocking of oxygen transport by blood is well known, is used as a common synthesis feedstock in the manufacture of acrylics and other polymers, and in the elaboration of molecular structures for drug development.

These, and other such materials are relatively slow to produce an effect, and their use can require rather large quantities in order to be effective. They are readily available, however, and there-in lies the threat of use by terrorists. For all their relative weaknesses as weapons of warfare, such materials are quite capable of causing severe casualties and fatalities if they were to be deployed in a civilian setting. The possible results of releasing one of these materials in a densely-occupied, confined area with restricted egress, such as in a crowded subway or a standing-room-only theater, are indeed frightening to consider.

Simple industrial chemicals have long since been supplanted by more sophisticated and effective chemical warfare agents. These include the so-called "nerve gases" such as Sarin and VX. Contrary to the name, these and most other agents are not gases but liquids that must be physically contacted in order to have an effect.

This begs the question of how do chemical agents actually work if they are not gases to be breathed. As previously stated, chemical agents can only be either solids, liquids, or gases. While this may seem a trite simplification, the feature that determines how a chemical agent is used and deployed is its physical state rather than its chemical identity. Gases can only be released into the atmosphere, liquids can only be sprayed or painted, and solids can only be set in place or spread as a dust. A liquid that vapourizes becomes a gas, subject to atmospheric dispersal, as does a solid that sublimes. A solid that dissolves becomes a liquid. There are no other physical parameters for these materials, and regardless of the form of the agent it must be physically contacted or breathed in by its intended target in order to have an effect of any kind.

The physical state of the agent also determines its persistence once it has been deployed. Actual gases such as chlorine and carbon monoxide are the least persistent of chemical agents. Once released, they become subject to dispersal by air movement and to rapid dilution as they mix with the air. Their effectiveness in terms of having a rapid debilitating effect is limited by this concentration dependence.

Liquid agents are more persistent. They must be deployed either by spraying or painting, and this can take a variety of forms. The most insidious of these would be deployment by means of an explosive device. Once released, however, the liquid agent becomes almost completely immobile, unlike gases. To have an effect then requires active physical contact by the intended victim. It must be touched in some way, whether on purpose or by accident. The 'trick' is to deploy the agent in such a way that contact is unavoidable. Solid chemical agents disseminated as a powder or dust, perhaps through the use of an explosive device, must nevertheless settle in place. Once settled, they are completely immobile, again requiring active physical contact by the intended victim in order to produce an effect.

The most dangerous period in the deployment of a chemical agent is its initial mobile phase. During that time, contact with and movement of the agent is the most unpredictable. Paradoxically, the most effective period is generally when the agent has become immobile. In the trade of glass-blowing there is a working axiom that says "hot glass looks exactly the same as cold glass". Glass workers who forget this invariably end up with badly burned hands. A similar axiom could be stated for chemical agents: contaminated areas look exactly the same as clean areas. In other words, immobile chemical agents do not noticeably alter the appearance of their surroundings. A great number of injuries and fatalities due to contact with chemical agents can be attributed to this fact, and a number of chemical agents do not produce an immediately noticeable effect when contacted. During the Iran-Iraq war, for example, many Iranian soldiers suffered horrible fatalities from contact with mustard, which is not the usual result to be expected. Since the onset of effects from mustard can take several hours, those soldiers continued to wear clothing in which the chemical agent had become immobile. Prolonged contact with this material, a blistering agent, and breathing in its fumes proved fatal rather than merely debilitating.

Ironically, the dangerous immobile phase of chemical deployment is also the very feature that minimizes much of their danger and allows countermeasures to be taken. Once an area has been identified as or is suspected to be contaminated, it can be completely avoided by other potential victims and decontaminated by appropriately trained and equipped personnel.

Next Time We Will Continue with The Effects of Chemical Weapons

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Last modified December 2002

 All images credit and courtesy of the National Institute of Health