For the purpose of the CWC (Article II) “Chemical weapons” means, together or separately, the following: a) toxic chemicals and their precursors, except where intended for purposes not prohibited under the Convention, as long as the types and quantities are consistent with such purposes; b) munitions and devices, specifically designed to cause death or other harm through the toxic properties of those toxic chemicals; and c) any equipment specifically designed for use directly in connection with the employment of those munitions and devices. A toxic chemical agent is any chemical which through its chemical action on life processes can cause death, temporary incapacitation or permanent harm to humans or animals.
It is common to classify chemical agents based on their predominant physiological action. On this basis, they can be grouped into choking, blood, blister and nerve agents.
Choking agents attack lung tissue and can cause a build-up of fluids in the lungs which then suffocates the victim. Phosgene, diphosgene, chlorine, perfluoroisobutylene and chloropicrin are all choking agents.
These agents affect body functions by blocking cell respiration and the normal transfer of oxygen from the blood to body tissues. Hydrogen Cyanide, Cyanogen Chloride are blood agents.
Blister agents act on the eyes, mucuous membranes, lungs and skin. Local action on skin causes swelling (blisters) and reddening followed by skin necrosis while local action on the eyes produces severe necrotic damage and loss of eyesight. Most fatalities are caused by systemic action that occurs primarily through inhalation. When sulfur mustard is inhaled, the upper respiratory tract is inflamed causing pulmonary oedema. Higher doses can produce injury to bone marrow, lymph nodes and spleen. Sulfur mustards, Lewisites and Nitrogen mustards and phosgene oxime are all blister agents.
Nerve agents are organo-phosphorus compounds that inhibit an enzyme called acetylcholinesterase causing accumulation of the neurotransmitter acethylcholine and overstimulation of muscles and glands. Exposure symptoms include runny nose, tightness of the chest, dimmed vision and pin pointing of eye pupils, difficulty in breathing, drooling and excessive sweating, nausea, vomiting, cramps, involuntary defecation and urination, twitching, jerking and staggering, confusion, coma and convulsion. The symptoms are followed by respiratory failure and death. Tabun, Sarin, Soman, GF, and VX are examples of nerve agents.