Nerve agents
The most lethal and important chemical weapons contain nerve agents, which affect the transmission of impulses through the nervous system. A single drop on the skin or inhaled into the lungs can cause the brain centres controlling respiration to shut down and muscles, including the heart and diaphragm, to become paralyzed. Poisoning by nerve agents causes intense sweating, filling of the bronchial passages with mucus, dimming of vision, uncontrollable vomiting and defecation, convulsions, and finally paralysis and respiratory failure. Death results from asphyxia, generally within a few minutes of respiratory exposure or within hours if exposure was through a liquid nerve agent on the skin. Defense against nerve agents requires a skintight gas mask and special protective overgarments.
In the mid-1930s chemists working for the German chemical corporation IG Farben developed the first organophosphorus compound with an extremely high toxicity; this became the nerve agent known as tabun (GA). As much as 12,000 tons was produced for the German army in World War II, although it was never used. Another nerve agent, sarin (GB), was first produced in 1938, and a third, soman (GD), was introduced in 1944; both were also invented in Germany. These three German nerve agents, the G-series (for German) in U.S. nomenclature, were all seized in large quantities by the Allies at the end of World War II. After the war the United States, the Soviet Union, and a number of other states also produced these and other nerve agents as weapons.
VX, the most famous of the so-called V-series of persistent nerve agents (and also the deadliest known nerve agent; V is for venom), was developed by chemists at a British government facility in 1952. Britain renounced all chemical and biological weapons in 1956 but traded information on the production of VX with the United States in exchange for technical information on the production of thermonuclear bombs. In 1961 the United States began large-scale production of VX. The only other countries believed to have built up VX arsenals were the Soviet Union, France, and Syria. Following the signing of the CWC in 1993, the United States and Russia began the elimination of their chemical weapons stocks, with a goal of finishing the process by 2012; neither country trains its forces with such weapons at present.
Defense against nerve agents requires a skintight mask and effective protective overgarments.
Incapacitants
A good deal of work has been done on chemicals that can incapacitate, disorient, or paralyze opponents. Experiments have been conducted on a number of hallucinogenic drug compounds—for instance, 3-quinuclidinyl benzilate (BZ), LSD (lysergic acid diethylamide), mescaline, and methaqualone—and at one time the U.S. Army fielded BZ weapons. Those chemical weapons are designed not to kill; however, even incapacitants can cause permanent injury or loss of life if employed in high dosages or if they cause accidents. BZ or LSD may attack the nervous system and derange a victim’s mental processes, causing, for example, hallucinations or psychotic thinking. Other incapacitants might cause victims to sleep or to be slow to respond.
Riot-control agents
Tear gas and vomiting agents have been produced to control riots and unruly crowds. Commonly used tear gases are chloracetophenone (CN), chloropicrin (PS), dibenz(b,f)(1,4)oxazepine (CR), and o-chlorobenzylidenemalononitrile (CS). CN, the principal component of the aerosol agent Mace, affects chiefly the eyes. PS and CS are stronger irritants that can burn the skin, eyes, and respiratory tract. Such riot-control agents are banned by the CWC if used as “a method of warfare” but are allowed for domestic police enforcement.
Although the United States signed and ratified the CWC, it has reserved the right to use riot-control agents in certain other situations, including counterterrorist and hostage-rescue operations, noncombatant rescue operations outside war zones, peacekeeping operations where the receiving state has authorized the use of force, and military operations against non-state actors initiating armed conflict.
Herbicides
Herbicides are not banned by the CWC unless they are used as “a method of warfare.” However, not all state parties to the CWC consider herbicides to be chemical weapons, and those states therefore do not recognize their use to be banned by the treaty.
States can attach reservations if they do not directly undermine the essential purposes of the treaty. In this case it is less essential to regulate nonlethal herbicides than the more dangerous chemical weapons.
Herbicides can be used to destroy enemy crops and foliage cover. For example, Agent Orange was used extensively by U.S. forces between 1962 and 1971, during the Vietnam War, as a defoliant to deny cover in the jungle to the Viet Cong and to North Vietnamese forces. Other herbicides, such as paraquat, Agent White (picloram and 2,4-D), and Agent Blue (dimethyl arsenic acid), have also been produced to act as chemical weapons.
Properties of chemical weapons
Chemical weapons can be categorized by their physical characteristics, such as lethality, persistency, mode of action on the human body, and physical state (i.e., gas, liquid, or solid) when being delivered.
Some chemical agents are highly lethal. For example, nerve agents such as sarin, tabun, soman, and VX can kill almost instantly; a few droplets absorbed through the skin can paralyze and cause death in minutes. At the other end of the lethality spectrum are chemical agents such as tear gas that only act as irritants or incapacitants and are unlikely to kill unless used in very large quantities.
Chemical agents also have varied levels of persistency. Some evaporate in minutes or hours and lose their effect rapidly. For example, sarin is a lethal but nonpersistent nerve agent. By contrast, VX can persist for days or weeks in lethal form. This difference in persistency may lead to a different strategic or tactical use of each agent in wartime. A military force may use persistent chemical weapons, such as VX or mustard, to neutralize an air base, seaport, or key staging area for an extended period in order to deny its use to the adversary. On the other hand, nonpersistent chemical weapons, such as sarin, more likely would be employed where only a temporary effect is sought. For example, nonpersistent chemical weapons could be used to breach an enemy line at a point that one’s own forces might want to pass through or occupy after the effects have dissipated.
Some poison gases, such as chlorine and hydrogen cyanide, enter the victim’s lungs during inhalation. On the other hand, nerve agent droplets might enter through the skin into the bloodstream and nervous system. Still other chemicals can be mixed with food in order to poison enemy personnel when they take their meals.
Finally, chemical weapons might be delivered via aerosols, mortars, artillery shells, missile warheads, mines, or aerial bombs. Most of these have all the ingredients premixed, but newer chemical arms may be so-called binary weapons in which the ingredients are mixed in flight while the weapon is being delivered. Binary weapons are safer and easier to store and handle than more-traditional chemical arms.