Part Three

Effects of Chemical Weapons

The purpose of any chemical weapon is simple: to remove as many opponents as possible from the field of battle as quickly as possible. This does not necessarily mean killing them. Rather, the idea is to render them incapable of fighting. In a military application, it can be sufficient for a chemical agent only to cause widespread aggravation and injuries requiring intensive and prolonged medical attention. Not only do the affected personnel become incapable of fighting, but manpower is tied up and basic support services can become overloaded to the point of breakdown.

For chemical agents employed by terrorists, this is probably not a consideration. Terrorists are more likely to use chemical agents that cause death or at least life-long disfigurement or debilitation; something that would maximize the terror component and reduce the morale and self-esteem of the victims. (Terrorists seem to have overlooked the rule of life that says 'whatever does not kill you only serves to make you stronger'...)

The effects of chemical agents come from their interaction or interference with normal biochemical processes. Given the complexity of human biochemistry and physiology, it is a wonder that only a small number of actual chemical warfare agents have been developed or investigated.

The various chemical agents can be classified into groups according to their general physiological effects or mode of action. All are poisons of one sort or another, and all are used to incapacitate their victims to varying degrees.

Tearing agents, the most benevolent class, are not strictly defined as chemical warfare agents and are primarily used in civilian life for such things as riot control (tear gas) and the temporary incapacitation of an attacker (pepper spray). The more correct term for these materials is "severe lachrymators". They have the effect of blinding victims by causing painful burning of the eyes accompanied by a copious flow of tears. But while painful and debilitating, the effects of tearing agents are very temporary and easily countered. Useful for such things as riot control and police actions, tearing agents do not provide an effective manner of incapacitating large numbers of people for a significant length of time. They are therefore not classed as chemical warfare agents. Materials used as tearing agents include bromobenzyl cyanide, chloroacetophenone, and ortho-chlorobenzylidinemalononitrile.

A somewhat similar group of materials that are officially classed as chemical warfare agents, is called the choking agents. Their effect is to cause lung irritations resulting in pulmonary edema and lesions typified by choking and extreme difficulty in breathing. The human body, when subjected to such an effect, will automatically focus all of its energy and effort into recovering the ability to breathe before the situation becomes life-threatening; such trivial matters as firing a weapon or holding one's ground or continuing an attack quickly fall by the wayside. While more aggressive and longer lasting than tearing agents, normally the effects of choking agents are fully reversible in time, provided that the victim can avoid or be removed from exposure, Prolonged exposure to a choking agent can, of course, be fatal. Materials used as choking agents include phosgene (carbonyl chloride), diphosgene (trichloromethyl chloroformate), chlorine gas, and chloropicrin (trichloronitromethane).

Perhaps the most insidious of all chemical warfare agents are the so-called "blood agents". These have only one physiological effect: to remove the ability of the victims' blood to transport oxygen. Blood agents work by binding to the oxygen-carrying site of the haemoglobin molecule. This prevents haemoglobin from binding with oxygen molecules, and the victim more or less quickly dies from oxygen deprivation. The rapidity, or the slowness, of this effect depends entirely on concentration and exposure time; the more of the agent that there is and the longer it is contacted, the faster does death occur. The only intent in the deployment of a blood agent is the death of the victims. These agents have been long known, and have a long and infamous history. As may be expected, these materials include hydrogen cyanide and cyanogen chloride. Carbon monoxide can also be included in this group, and the possibility of its use by terrorists is truly frightening. While the cyanides can be recognized by the characteristic smell or taste of almonds, carbon monoxide is completely colourless, odourless, and tasteless. Victims of exposure simply pass out and die without any indication of danger.

The 'big guns' of chemical warfare agents are the blistering agents, or vesicants. As the name might suggest, the effects of blistering agents are not pretty. Contact with these materials results in the eruption of painful, incapacitating lesions and blisters. Inhalation of the vapours from these materials carries the effect inside the lungs of the victims. Prolonged medical attention is required, thus binding up manpower and essential services that would otherwise be used to support ongoing military actions. Death of the victims is not the usual result, nor is it the desired result of exposure to blistering agents. Death of the victims does not tie up manpower and resources to the same extent. However, since the time required for an effect to be actually felt by the victims can be several hours, it can happen that the victims of exposure continue to breathe in fumes from these agents for prolonged periods of time. This did happen during the Iran-Iraq war, resulting in the death of many Iranian soldiers. Blistering agents come in a variety of chemical identities ranging from highly acidic, such as fuming sulphuric acid or 'oleum' (SO3/conc. H2SO4), through neutral sulfur 'mustards such as dichloroethyl sulfide, to the strongly alkaline nitrogen 'mustards' such as trichloroethylamine. Apparently no particular group of chemicals governs the realm of blistering agents, since vesicant properties are found in all classes of chemicals.

Contact time is an important consideration with blistering agents. The longer the exposure time, the more pronounced is the effect. Many blistering agents quickly lose their vesicant properties on contact with water or mild oxidizing agents such as common household bleach. For highly effective blistering agents, then, chemical stability is key, and the onset of uncomfortable sensations resulting from contact is slow. This can increase the actual contact time from mere moments to several hours.

The last major group of chemical warfare agents is the "nerve" agents. In contrast to the blistering agents, contact time with a nerve agent' is not a consideration. Since the effectiveness of blistering agents is more pronounced the longer contact is maintained, the survivability of contact with blistering agents depends very strongly on minimizing the duration of the contact. For nerve agents, contact alone is sufficient. They are absorbed so quickly and the fatal dose is so small that minimizing the response time is crucial for survivability. Countermeasures must be administered immediately in order to give the victim a fighting chance of survival.

Nerve agents are rapidly absorbed through the skin. Once entered into the body, these compounds disrupt nerve function by inhibiting the enzyme acetylcholinesterase. The transmission of all nerve impulses throughout the entire body proceeds by the enzyme-mediated conversion of acetylcholine. When this conversion can not occur, as is the case when acetylcholinesterase is blocked by a nerve agent, there is no transmission of a nerve impulse. The body shuts down as it loses the ability to breathe, to move, to pump blood, even to think. With the system-wide disruption of nerve function, death can follow in a matter of minutes. Atropine or a related counteragent must be administered almost immediately in order to be effective.

The effects of nerve agents are dose dependent, and lethal doses are so small that exposure can easily result in contact with quantities equivalent to several lethal doses. As the symptoms progress, it may be necessary to give atropine repeatedly to keep the victim alive. Even this may not be enough. There comes a point as the symptoms progress when the nerve function can not be regenerated sufficiently to maintain life, no matter how much counteragent is administered, and the victim dies. Response time and minimal exposure are absolutely critical for survival.

Nerve agents are classed into two groups: the 'G' agents and the 'V' agents. The 'G' agents (after their discoverer, Gerhard Schrader) was developed between 1936 and 1944, and includes the materials known as Sarin (isopropyl methyl phosphonofluoridate), Tabun (ethyl N,N-dimethylphosphoramidocyanidate), and Soman (pinacolyl methyl phosphonofluoridate). Herr Schrader discovered these materials rather by accident when he realized that he and his colleagues were being affected with blurred vision, dizziness and other symptoms in the course of their laboratory work, and although large quantities of these materials were subsequently produced by the Nazi war effort during World War II, they were never used in that conflict by either side. The 'V' agents, most notably the materials known simply as 'VX' (O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate) and 'VM' (O-ethyl S-(2-diethylaminoethyl) methyl phosphonothiolate), have been developed since 1953. The 'V' stands for 'venom', due to the similarity of these compounds to snake venoms in their action. Developed by the British and other Allied nations after World War II, based on captured German research data, there is still a significant amount of secrecy surrounding the development work that was undertaken to produce the V agents.

Counterweapons

There are no hard and fast general rules for countering the effects of chemical weapons, other than to takes whatever steps possible to minimize both the length of time one is exposed to the agent and the length of time taken to respond with administration of specific countermeasures. The single most important factor for victims of a chemical agent attack is to not panic.

Any and all specific steps to be taken after exposure will depend on the identity and nature of the particular chemical agent or agents that have been contacted, the conditions of exposure, and on what may actually be readily available for use as a countermeasure. For all but the nerve agents, flushing with large amounts of running water to dilute and wash the chemical agent away as quickly as possible may go a long way to minimize the effects of exposure. This of course depends entirely on the availability of such water. The simple expedient of triggering an available automatic sprinkler system can do the job, provided one is sufficiently aware of the situation to think to trigger the water spray. Keeping one's eyes firmly closed and breathing as lightly as possible will also help to minimize the effects of chemical exposure.

Since chemical warfare agents are themselves just chemicals, one of the most effective countermeasures is to alter their intrinsic nature by forcing them to undergo certain reactions. Many chemical agents, particularly the sulfur mustard agents, are fairly easily oxidized with a 5% solution of sodium hypochlorite (common household bleach). In sulfur-based mustard agents, the sulfur atom becomes oxidized from sulfide to sulfoxide and sulfone, destroying the vesicant properties of the material, and one can tolerate contact with household bleach a lot more safely than with a sulfur mustard agent. Again, presence of mind in the event of an attack, and the availability of materials to hand are of great importance.

All chemical warfare agents have specific effective countermeasures that can be applied by anyone who has taken the time to make themselves familiar with available information. (Nerve agents, with which effective countermeasures are very limited, are an exception.) The single most effective countermeasure against chemical agents is knowledge. Being aware of the chemical nature of the world and the society we have constructed for ourselves, and understanding how chemistry can either harm or help us, is paramount to using that knowledge to protecting ourselves as well. While it is not within the realm of reason for everyone to know the chemical principles that would allow them to take steps on their own, there is certainly a wealth of information to be had. Complete descriptions of chemical warfare agents as 'Fact Sheets' and 'MSDS' forms are readily available. These documents contain complete descriptions of effective countermeasures and steps to be taken in the event of exposure. They represent the knowledge that can save lives and make the use of chemical weapons much less effective, and much less likely.

Next Time We Will Continue with Counterweapons

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Last modified January 2003

 All images credit and courtesy of the National Institute of Health