Nerve agents (chemicals of the same family as organophosphorus insecticides) are the most lethal of the classical chemical warfare agents, killing by poisoning the nervous system and disrupting bodily functions. Blister agents (such as mustard gas) burn and blister the skin (causing more casualties than any other agent in the first world war). Vesicants are blistering and tissue-injuring agents which produce injuries similar to burns, although the mechanism behind the injury is different. Choking agents (such as phosgene) are highly volatile liquids. Toxins (such as mycotoxins and botulin toxin) are biological substances chemical substances produced biologically (although many of them have also been synthesized) which are very highly toxic. Tear gas and harassing agents are sensory irritants causing pain in the eyes, tear flow, and severe irritation of the upper respiratory tract (and have been widely used as riot control weapons); they can also cause skin irritation, nausea and vomiting. Psycho-chemicals are drug-like chemicals intended to cause temporary mental derangement, including psychosis. Cyanides (blood agents) cause headaches, weakness, disorientation and nausea in low doses; higher doses are acutely lethal causing circulatory effects, seizures and respiratory and cardiac failure. Incapacitating agents produce physiologic or mental effects, or both. They render individuals incapable of performing normal activities. DZ (3-quinuclidinyl benzilate) is the most commonly used. It is pharmacologically related to anticholinergic drugs and is present within some over-the-counter sleeping medications. Tear gases are used primarily for riot control and cause irritation to the eyes, respiratory tract, and skin. Herbicides may also be used to poison or defoliate plants.
Defoliant chemicals were originally developed by the UK and used in the Malayan anti-terrorist campaign in 1948-60. During the Second Indochinese War, the USA used Agent Orange, a defoliating herbicide, and the riot-control agent CS. The USA used the same quantity of chemicals as was used by all the belligerents in the First World War, about 100 million kilograms (1965-1970).
The US Army divides chemical warfare agents according to different features including the nature of their use, their persistence in the field, and physiologic effects. They may produce incapacitation, serious injury and death. For tactical purposes, chemical warfare agents may be divided into two main categories:< (1) Persistent agents are those that remain dangerous for a considerable amount of time unless action is taken to destroy or neutralize them. They are usually liquid or solid at normal temperatures.
(2) Nonpersistent agents are those that remain in effective concentrations for only a short time. They are released as airborne particles of a solid, droplets of a liquid, or as true gases. They are affected by prevailing weather conditions and are quickly dispersed, so that the locality in which they have been released soon ceases to be contaminated.
For medical and service classification, chemical warfare agents are usually classified according to pharmacologic principles and their overall effects on combat efficiency.
Hundreds of Gulf War veterans have complained of severe flu-like symptoms (as many as 2,000 may be affected), but it is not know if chemical weapons were the cause. In 1993 it was alleged that Iraq had rebuilt its chemical weapons factories and had used such weapons (possibly white phosphorous) against Arabs located in the Hammar Marshes south of the Euphrates river. The Pentagon had insisted that it learned only in 1996 of an incident in which large numbers of American troops may have been exposed to chemical weapons - an event in March 1991, in which American combat engineers blew up an Iraqi ammunition bunker that was later determined to have contained tons of nerve gas and mustard agent.
Incapacitating agents produce physiologic or mental effects, or both. They render individuals incapable of performing normal activities. DZ (3-quinuclidinyl benzilate) is the most commonly used. It is pharmacologically related to anticholinergic drugs, and is present within some over-the-counter sleeping medications.
Tear gases are used primarily for riot control and cause irritation to the eyes, respiratory tract, and skin. Long-term effects of repeat exposure to these gases are not well studied.
2. Poison gas is one of the ugliest and most indiscriminate weapons in the modern armory.
2. Pentagon officials insisted that despite the technical sophistication of the mobile chemical-detection laboratories, known as the Fox vehicles, which are able to detect 60 different chemical agents simultaneously using a laboratory-quality mass spectrometer, most of the detections made during the 1991 Gulf War were false alarms.