Introduction to Chemical Warfare Agents

CHEMICAL WARFARE AGENTS (CWA), as terrible as they are in war, are no longer limited to use on traditional-type battlefields. The terrorist has adopted these weapons to be used against civilian populations, and this produces new threats to first responders. Prior training of these responders in the field of hazardous materials response gives them at least a head start in understanding these weapons.

The discussion of CWA may be very elementary to those who have been studying them; but to others, it might all be painfully new. The majority of first responders lie somewhere in between. They are the principal audience for this series of articles, plus the newcomers and those seeking a refresher. Chemical warfare, in one form or another, has been in use for centuries, ever since the first army discovered that the smoke of burning sulfur irritated the enemy and, in many cases, incapacitated him. Germany was the first to use of poison gases, in 1915, during World War I, when 10,000 soldiers were killed in two releases of chlorine gas.

The purpose of this series is to try to demystify CWA and to help educate those who must respond to threatened or actual incidents involving them. The chemistry of each of the agents will be presented, mainly to show how they are related or not. A physical description will also be presented, in addition to the symptoms of exposure to each. Your training must provide you with the tactics necessary for your protection and that of the public. Hopefully, the information provided will be easily assimilated and understood. In any event, every first responder must get all the training available to help combat these chemicals and the people who would use them against us.

Decontamination is an integral part of all responses to these incidents. It must be left to each responding organization to see that decontamination is carried out properly by trained, educated, well-equipped personnel to prevent the spread of any chemical warfare agent.

CWA are defined by the Chemical Weapons Convention as toxic chemicals, but the definition also includes the ammunition and equipment used for their dispersal against humans. Toxic chemicals are defined as “ … any chemical which, through its chemical effect on living processes, may cause death, temporary loss of performance, or permanent injury to people and animals.” There are other definitions possible, but the term “chemical warfare agent” should be understood intuitively.

Toxins produced by living organisms and their synthetic equivalents will not be discussed, nor will ammunition and equipment used for their dispersal.

CWA are chemicals that fall into several classes of hazardous materials. Some of these materials are familiar to responders of hazardous materials incidents; most are not. Some are gases, some are liquids, and some are solids. Some are very simple chemicals; others are very complex. The only sensible way to classify these chemicals is by their effects on humans.


The major classes of CWA that will be covered are:

  • Nerve agents.
  • Blood agents.
  • Blister agents.
  • Choking agents.
  • Other incapacitating agents.

Minor classes of CWA that will not be covered are:

  • Psychotomimetic agents.
  • Incendiary agents.


Not all toxic chemicals can be used as CWA. The agent must be able to be stored safely for long periods of time and then be able to be moved long distances without losing its effectiveness. The chemical must be able to be delivered so that it is not adversely affected by atmospheric or weather conditions or by the method by which it is dispersed. A toxic chemical must not be so toxic or so difficult to handle that it presents an unreasonable risk to those who wish to administer it.

Different references may include different chemicals in the classes listed below, but all seem to agree on the chemical compounds listed as nerve agents and blood agents. The effects of any one of these chemicals can range from very mild symptoms to death. The symptoms in any individual, of course, depend on the concentration of the chemical, the length of exposure, the method of contamination (entry into the body), and the individual body chemistry (reaction to the exposure), plus the degree of medical attention and the time lapse between exposure and treatment or removal from the chemical.


A nerve agent works within the human body by inhibiting the normal actions of acetylcholinesterase, an enzyme produced by the body to control the actions of acetylcholine. Acetylcholine is a chemical released at the nerve endings to facilitate the normal transmissions of nerve impulses (a neurotransmitter). When acetylcholinesterase cannot do its job, the acetylcholine builds up at the nerve endings, and uncontrolled muscle spasms occur. Many normal functions of the body then face interruption, and many symptoms occur, varying with the route of exposure. Respiratory symptoms generally are the first to appear after inhalation of nerve agents in vapor or aerosol form, whereas gastrointestinal symptoms are usually the first after ingestion. Tightness in the chest is an early local symptom of respiratory exposure. These symptoms progressively increase as the nerve agent is absorbed into nervous system circulation, whatever the route of exposure. Following comparable degrees of exposure, respiratory manifestations are most severe after inhalation, and gastrointestinal symptoms may be most severe after ingestion. Aerosol or liquid that contacts the skin may cause severe itching and rashes before other symptoms appear. The end result of such poisonings is often death.

Nerve agents are related to insecticides, from which they were developed. Insecticides were never meant to poison humans, but the very chemical nature of the materials meant that they would be dangerous to humans. Once the mechanisms were understood, it did not take a large scientific leap to further develop those chemicals so that they would be very toxic to humans.

Basically, nerve agents are very complex organophosphates. Once the effect on the human central nervous system was understood, it was fairly easy to refine the effect with more “efficient” chemicals.


The first of the organophosphates was produced in 1854 and was originally developed to control insects and save crops from being destroyed by those insects. In fact, the University of Arkansas Glossary of Agricultural Production, Programs and Policy, defines organophosphates (OP) as pesticides made up of organic compounds containing phosphorous that affect the functioning of the nervous system.

More extensive research was not carried out on them until the 1920s and 1930s, mostly by German scientists (this is supposedly where the “G” designation originated). This work was done to try to find the most efficient and effective pesticides possible. The result of this research produced in late 1936 a compound the German researchers called “tabun.” During further work on this organophosphate, the lead researcher and his assistant were exposed to tabun vapors. The results of this accidental exposure demonstrated that the material might have military applications. The German government took over the work on tabun and produced several thousand tons of it during the Word War II.

After the production of tabun had begun, more work was done on developing more organophosphate insecticides (and most certainly as nerve agents). The result of this work produced sarin in 1945, while more researchers were beginning the study of soman. The Germans had a monopoly on the production of these nerve agents but never used them, probably because they feared the allies also had them and superior allied airpower might be used to deliver them against Germany.

The victors in the war captured all this information and developed research on their own, concentrating mostly on sarin (the United States and the United Kingdom) and both sarin and soman [the Union of Soviet Socialist Republics (USSR)]. Tabun, sarin, and soman were the first three nerve agents in the so-called “G” series, designated as “GA,” “GB,” and “GD,” respectively. Eventually, cyclohexyl sarin, or cyclosarin (GF), and DMAEDMAPP (GP, also known as GV) were added to the G series.

In the 1950s, more work was done on the organophosphates to try to make more efficient pesticides while using this research to improve the military aspect of the nerve agents. In 1954, amiton was developed and put on the market as a pesticide, but it was withdrawn because it was too toxic to be used safely as a pesticide.

The toxicity of amiton and other compounds made them attractive as nerve agents. As they were developed, they were given the designation “V” series. Amiton was given the military designation of “VG”; the most famous in this series was designated “VX.” The United States and the USSR carried out much of this work; the Soviets are leading the way. Eventually, the “V” series also included VE, VM, VR, VS, and Vx (V gas). The “V” designation is said to have originated because the research on new nerve gases was carried out by the “victors” of World War II.

In the meantime, work in the United States also continued in the pesticide market. The active ingredients for these organophosphates included methyl parathion, ethyl parathion, malathion, and chlorpyrifos.


Blood agents are chemical compounds that interfere with the vital ability of blood to transport oxygen in the bloodstream to all the cells of the body (blood asphyxiants) or, in the case of a tissue asphyxiant, a substance the blood cell picks up instead of oxygen, delivers to the body cell, and poisons the blood cell when it gives the substance up to the body cell.

Blood asphyxiants combine with the red blood cells and render them incapable of combining with oxygen and thereby of carrying the oxygen to the body’s cells. The normal process involved after breathing is the formation (by oxygen) of a compound in the red blood cell called “oxyhemoglobin.” This weak chemical compound serves as the vehicle for carrying oxygen to the cells, where the oxygen is “dumped” (released to the cell) and carbon dioxide released by the cell is picked up and brought back to the lungs for disposal. Anything that interferes with this process by preventing the formation of the oxyhemoglobin is a blood asphyxiant. Typical blood asphyxiants are carbon monoxide (by far the most common), aniline, and nitrobenzene.

Arsine (SA) is a blood agent that works by killing red blood cells, thus shutting off the flow of oxygen to the cells. In this manner, it differs from carbon monoxide and the other blood asphyxiants.

Tissue asphyxiants are those materials carried by the red blood cells to the body’s cells and which are given up to those cells in exchange for the carbon dioxide the cells are holding, poisoning them by making the cells incapable of ever again accepting oxygen from the red blood cells. Unlike carbon monoxide, which attaches itself to the red blood cell so tightly that it will not let go and renders the red blood cell incapable of picking up oxygen, the tissue asphyxiant allows itself to be “dumped” to the receiving body cell just as oxygen does. On acceptance of this material from the red blood cell, however, the body cell is poisoned so that it can no longer accept oxygen. The most common tissue asphyxiants are hydrogen cyanide (AC), cyanogen, and cyanogen chloride (CK).


Blister agents, as one would expect, cause the formation of large, painful blisters when they contact the skin, often incapacitating the victim. The effect of the agent on the skin after exposure to certain vesicants, such as mustard gas, might be delayed as long as 24 hours. The lungs and eyes may also be damaged. If the exposure to the concentrated gas is long enough, the blisters will be so severe that they will take an extremely long time to heal and may cause the body to go into lethal shock.

Other vesicants, in addition to mustard gas, include sesquimustard, three types of nitrogen mustard, three types of lewisite, phosgene oxime (not a true vesicant but more dangerous), dimethyl sulfate, methyldichloroarsine, ethyldichloroarsine, and phenyldichloroarsine.


The first blister agent, sulfur mustard, was made as far back as the 1820s and was used by Germany almost a hundred years later in World War I. Retaliation by the allies occurred later in the same war. Mustard gas was “improved” (at least for chemical warfare) in the 1930s by substituting nitrogen for the sulfur in the compound.

To protect themselves from blister agents, combatants had to wear protective gear so bulky that it immobilized the troops almost as badly as if they had been poisoned by the agents.


Choking agents, as the name implies, attack the upper and lower respiratory organs, interfering with normal breathing. Violent coughing and the restriction of airways can and usually do incapacitate the victims quickly. If exposure to high concentrations of these agents is long enough, permanent damage and even death may occur.

Chlorine was probably the first chemical warfare agent used in so-called modern warfare (in 1915). Chlorine is a toxic, oxidizing, corrosive, reactive, irritating, noncombustible, dense, yellowish-greenish gas with a distinctive, sharp, pungent odor and an acrid taste. Used as a weapon, its high vapor density (2.49) will allow it to flow downhill and, as long as there is no strong breeze, “hang together,” flow in the trenches, and suffocate anyone without respiratory protection. Other choking agents that operate in much the same way are phosgene, diphosgene, ethyldichloroarsine, chloropicrin, nitrogen oxide, and perfluoroisobutylene.

The warring parties will take advantage of both the physical and chemical properties of the chemicals used to make them more “effective” in doing the job expected of them. Sometimes the most simple of compounds (chlorine, in the case of choking agents) will be most effective.


Herbicides, chemicals used to kill vegetation, will not be covered in this series. First responders should be aware, however, that these compounds, which are very toxic to plants, might also be very harmful to humans. As in the case of Agent Orange, used to defoliate the jungles in Vietnam to expose enemy camps, trails, and other secret sites, indiscriminately contaminated many people. Today, more is known about the devastating effects of chemicals used so freely and thought to be harmless to humans. Homeowners and other individuals charged with creating beautiful landscapes constantly use herbicides in great amounts. These chemicals then have countless ways of entering our lifestyles; our activities; and, therefore, our bodies.


Incendiaries, which are used to start fires, will not be covered in this series. Incendiaries used in warfare are bombs or missiles that usually contain a flammable substance that will start a fire on impact. They may also be chemicals sprayed or otherwise applied to a target and then set afire. They may be used to destroy vegetation, burn down a target, or cause panic and chaos through the ignition of multiple fires.

Napalm is the most famous incendiary that has been used. There are countless different types of napalm, with various compositions. Napalm is a trade name that has since passed into the English language as any flammable materials used as a weapon and sticks to anything it touches. The trade named Napalm is a powder that is often mixed with gasoline. What is used today is a firebomb that uses a fuel-gel mixture, and the new nomenclature for napalm is a mixture of fuel and gelling solution combined to produce a thickened mixture. This mixture is very sticky and will readily adhere to most surfaces. The “napalm” is made by combining a gelling solution with aviation gasoline, JP-4, or JP-5 fuels.


Incapacitating agents will cause debilitating injuries to the victim on contact or by the victim’s ingesting or inhaling the substance. “Incapacitating agent” is defined by the U.S. Department of Defense as “an agent that produces temporary physiological or mental effects, or both, which will render individuals incapable of concerted effort in the performance of their assigned duties.” Incapacitating agents are not primarily intended to kill, but supposedly nonlethal incapacitating agents can kill many of those exposed to them.

Many references include choking agents and blister agents as incapacitating agents, since the effect is to remove the combatants or victims without necessarily killing them. Many of these chemicals will cause the victims to hallucinate and otherwise act as if they’ve lost their minds. These agents will not be covered in this series. Common incapacitating agents are canniboids, fentanyls, phenothiazines, Agent 15, Kolokol-1, Agent BZ, and LSD.


Other chemicals that may be classified as CWA will not be covered in this series. They include riot control agents and vomiting agents. Riot control agents include bromobenzylcyanide; chloroacetophenone; and Agents CNB, CNC, CNS, CR and CS. Vomiting agents include adamsite, diphenylchloroarsine, and diphenylcyanoarsine.


First responders can run into CWA in two ways. The first is through an accidental release of the agents caused by the leakage of stored or transported materials or an accident in the place of storage or the transportation vehicle. The second is through a deliberate release of the material by terrorists.

In the first case, first responders should already be prepared for the incident, including the knowledge of what the released agents are and the dangers they pose to the responders and the public at large. This knowledge should be in the responders’ possession, because they must be made aware of any CWA stored in their jurisdiction and of any planned transportation through their protection district.

The government might want to keep the presence of CWA in storage or in transportation a secret because of the possibility of terrorist action to steal the materials for later use or to cause an accident that will be devastating to the population. However, the authorities in charge of the CWA must inform first responders and other safety forces of the presence of such materials for this very reason.

Knowledge of what is present or what might be moving through the jurisdiction allows the first responders and others to train specifically for a release of those materials. Self-protection, protection of the public, evacuation procedures, first aid, emergency medical procedures, containment, decontamination, hospitalization, and treatment of the exposed, among other emergency procedures, must all be carried out rapidly and with the least number of injuries. Training, education, and proper equipment provided well in advance of such a release will save countless injuries and lives.

The second case, when terrorists may bring the CWA into your jurisdiction, presents the greater problem, if only for the uncertainty of what materials have been used in the attack. This response calls for broader training and education and more sophisticated equipment, including the proper equipment that will detect and identify the specific material released.

This second case is a greater problem for at least one other reason. The terrorists have incorporated the use of secondary devices specially designed to attack, injure, and kill first responders. This secondary device, after removing the majority of the emergency forces that responded initially, can then be followed by any number or types of devices and releases of even more deadly materials on a geographic area now helpless in the face of these attacks.

The fire service makes up the vast majority of first responders to every emergency in this country, including terrorist attacks. It is absolutely imperative that every department, large or small, paid or volunteer, protecting isolated or heavily populated areas take advantage of every training and educational opportunity to prepare themselves. The federal and state governments offer training courses, classes, and equipment purchase aid to all jurisdictions. You must take those steps that will protect you and your civilian population.


The absolute best way to defend against any weapon is to prevent its use. The governments of nations that are able to protect themselves somewhat from the use of CWA use many methods, including infiltration of the terrorist groups, counterespionage techniques such as monitoring telephone and e-mail transmissions, and other effective information-gathering operations. The best defense is to totally prevent any attack by any group using any weapons, conventional, chemical, or biological.

Chemical weapons do not magically appear out of nothing. They must be manufactured carefully, or the process can go out of control, killing anyone exposed. If the chemical to be used as a weapon is made correctly, it must then be stored properly in secure containers in a secure location. The containers must then be treated properly when moved and handled carefully when transferred to whatever mechanism will be used in an attack. Everything has to go “just right,” or disaster will strike the “bad guys.” The deployment of the weapon must also be done under the proper conditions, to achieve the effect the terrorists are after.

For this reason, the terrorist organization or individual will choose to use the chemical agents that most easily meet all the above conditions. This should make it easier for the authorities to track the manufacture of these materials by following the procuring of the precursor chemicals. Each of the nerve agents and other types of CWA must be manufactured from other chemicals, which, unfortunately, also have legitimate uses in the manufacture of other, more useful chemicals to industry, agriculture, and commerce.

It may border on restricting more rights that Americans are used to freely exercising, but the strict control of the manufacture, movement, sale, and use of all precursor chemicals may be the best way to control the CWA problem. These chemicals are literally everywhere, and everyone must do their part in solving the problem of free access to them. Chemical manufacturers are among the most helpful when it comes to the safe use of their products and in the safe mitigation of accidents involving chemicals. However, it will take the involvement of more than the manufacturers to exercise control. Everyone involved in the transportation, storage, and distribution of precursor chemicals must be part of the control network for it to work. The problem may travel as far downstream as the local hardware store, drug store, or agricultural supply store. Whenever an incident occurs, the American public is shocked to learn that not only can anyone buy these chemicals for terrorist activities but also that some of them are located in their own garages!

FRANK L. FIRE has worked for 40 years in the plastics industry and retired as executive vice president of sales, marketing, and international from Americhem, Inc., Cuyahoga Falls, Ohio, a provider of raw materials to thermoplastics processors. He has taught “Chemistry of Hazardous Materials” to firefighters and other emergency responders for 32 years; in the Fire Protection Technology program at the University of Akron (OH) Stark State College; for the National Fire Academy in Emmitsburg, Maryland; and, most recently, to civil support teams of the National Guard in Missouri and Minnesota. He has a B.S. in chemistry and an MBA from the University of Akron. He is the author of The Common Sense Approach to Hazardous Materials, The Common Sense Dictionary for Emergency Responders, A Study Guide to the Common Sense Approach to Hazardous Materials, Combustibility of Plastics, and Chemical Data Notebook: A User’s Manual and is a co-author of SARA, Title III: Intent and Implementation of Hazardous Materials Regulations. He has written more than 120 articles on individual hazardous materials for Fire Engineering.

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