Tear gas Orthochlorobenzylidenemalononitrile
The CS agent (Orthochlorobenzylidenemalononitrile) was first prepared in 1928 by two American chemists, Ben Corson and Roger Stoughton. (The initials CS were taken from the first letters of the discoverers’ names). However, it remained until 1956 for the British CBW at Porton Down, the Chemical Defense Experimental Establishment, to develop CS as a riot control agent. CS was first used on a large scale by the British in the Cyprus riots. In 1960, CS was officially adopted by the United States Army for use in riots.
CS in its pure form is a white crystalline powder that resembles talcum powder. It is classified as an irritant and tear-jerker. Since it is made of solid particles, it must be carried through the air by an agent or expelled into a fine powder. The smell is quite pungent.
CS causes burning and tearing of the eyes, as well as irritation of the skin and respiratory system. The burning effects of the eyes and skin will be similar to those of CN and irritation of the respiratory system will cause sneezing. It may take several seconds for the CS effect to occur. CS is most irritating in humid weather and on a damp skin surface. Anyone who has lost the sense of feelings due to the influence of narcotics or alcohol will not be affected by CS.
CS is a producer of tear and sneezes at levels as low as 0.05 mg / m3. CS powder is called CS1 and is much more durable than the aerosol form of the agent. As a further refinement, CS1 is silicone coated to extend its persistence in the field for up to several weeks; the weather resistant variety is called CS2.
Being extremely persistent, CS causes a serious decontamination problem in the area. Particles spread by any of the standard dispersion media will adhere to person, clothing, furniture, or accessories for extended periods. Humid conditions will make the odor and irritating effect linger indefinitely.
Decontamination is accomplished through the use of an alkaline solution. Typically a 5% sodium bisulfite and water solution is used for decontamination.
CS is less toxic than CN and only has temporary effects on the eyes. However, both CS and CN cause dermatitis and are sensitizers that can cause very serious allergic reactions after repeated exposures. Toxicological tests showed that animals that die after exposure to CS show an increased count of goblet cells in the respiratory tract and conjunctiva (the mucous membrane of the eyes, which lines the eyelid and covers part of the eyeball), necrosis (the death of cells) in the respiratory and gastrointestinal tracts, pulmonary edema (lungs filled with fluid) and bleeding in the adrenals. Death is the result of impaired oxygen transfer to the bloodstream as a result of edema, hemorrhage, and airway obstruction in the lungs. In the case of a substance like CS, attention must be paid to the degradation products that will be produced in the human body. Cleavage or hydrolysis into malononitrile and ortho-chlorobenzaldehyde is a reaction that is 50% complete in about ten minutes. Malononitrile is believed to undergo degradation to cyanide and thiocyanate, while the rest of the molecule combines with glycine and is excreted as ortho-chlorohippuric acid. Therefore, malononitrile is a highly toxic substance found in CS. The fatal dose for a 150-pound person is estimated to be about one gram or less.