Blood Agents

Blood agents enter the body through the respiratory tract. They affect bodily functions through action on the enzyme cytochrome oxidase, thus preventing the normal transfer of oxygen from blood to body tissue. Most blood agents act rapidly and are normally nonpersistent. In general, a victim who does not die quickly will recover within a few hours. The most common blood agents are hydrogen cyanide (AC) and cyanogen chloride (CK).

Although AC is one of the most deadly poisons known, it is one of the least effective chemical agents because it evaporates rapidly. The vapors are less dense than air. They do not provide a blanket of the agent, and the poisoning effects do not accumulate as exposure continues. CK deteriorates the chemical canisters in protective masks within a short period of time.

Choking Agents

Choking agents, sometimes called lung irritants, primarily injure the respiratory tract- that is, in the nose, throat, and particularly the lungs, causing pulmonary edema. In extreme cases, membranes swell, lungs become filled with liquid, and death results from lack of oxygen; thus, these agents choke an unprotected man. Fatalities of this type are known as "dry-land drownings."

The two most common choking agents are phosgene (CG) and diphosgene (DP). Use of these agents is rather limited because they react rapidly with water to yield nontoxic hydrolysis products. Their concentrations in air are reduced fairly rapidly by water condensates (rain and fog) and

by dense vegetation. Other classes of agents are much more efficient. Unlike the nerve and blister agents, choking agents have no poisonous effect upon foods; they are too readily destroyed.

Vomiting Agents

The most important agents of this type are diphenylchlorarsine (DA), diphenylchanoarsine (DC), and adamsite (DM). These agents are dispersed as aerosols and produce their effects by inhalation. Some minor eye irritation also might be observed.

These agents produce a feeling of pain and sense of fullness in the nose and sinuses. This is accompanied by a severe headache, intense burning in the throat, tightness and pain in the chest, irritation of the eyes and lacrimation. Coughing is uncontrollable and sneezing is violent and persistent. Nausea and vomiting are prominent. Mild symptoms, caused by exposure to very low concentrations, resemble those of a severe cold. The onset of symptoms may be delayed for several minutes after initial exposure, especially with DM. Therefore, effective exposure may occur before the presence of the smoke is suspected. If the protective mask is then put on, symptoms will increase for several minutes, despite adequate protection. As a consequence,

the victim may believe the mask to be ineffective, and by removing it cause further exposure. On leaving the scene of the attack, the victim's symptoms subside rather rapidly, and the severe discomfort vanishes after about one-half hour. At high concentrations, effects may last for several hours. Because of their arsenical properties, these agents make foods poisonous.

Tear Agents

Tear agents (also known as riot-control agents) are essentially local irritants, which, in very low concentrations, act primarily on the eyes, causing intense pain and a considerable flow of tears; stinging of warm, moist skin; and irritation of the nose. High concentrations produce irritation of the upper respiratory tract and lungs and cause nausea and vomiting. The agents may be either solids or liquids and may be dispersed in the air as vapors or smokes. Tear agent include CN, CNC, CNB, BBC, and CS. Of these agents, CS is the newest and most effective. It produces immediate effects even in extremely low concentrations. An individual is incapacitated about 20 to 60 seconds after exposure. Effects last 5 to 10 minutes after the affected individual is removed to fresh air. During this time, affected individuals are incapable of effective concerted action. The physiological effects include extreme burning of the eyes accompanied by copious flow of tears; coughing, difficulty in breathing, and chest tightness; involuntary closing of the eyes; and stinging sensation of moist skin. This agent is highly successful in quelling riots. Although personnel exposed to CS may shower as necessary, when CS dust or particles are on the skin, showering should be delayed for 6 hours to prevent stinging and reddening of the skin.