Chlorine

Chlorine is a halogen element used as a bleach, oxidizing agent, and disinfectant in water purification. Chemical formula Cl, chlorine is a corrosive - toxic gas. Chlorine gas can be pressurized and cooled to change it into a liquid so that it can be shipped and stored. When liquid chlorine is released, it quickly turns into a gas that stays close to the ground and spreads rapidly. Chlorine gas can be recognized by its pungent, irritating odor, which is like the odor of bleach. The strong smell may provide an adequate warning to people that they have been exposed.

Chlorine is mainly used to bleach paper and cloth and to make pesticides, chemicals, rubber, and solvents. It is used to kill bacteria in drinking water and swimming pool water. It is also used in the sanitation process for industrial waste and sewage, and as a disinfectant and fungicide. Chlorine's most important use is as a bleach in the manufacture of paper and cloth. Chlorine is also used widely as a chemical reagent in the synthesis and manufacture of metallic chlorides, chlorinated solvents, pesticides, polymers, synthetic rubbers, and refrigerants. Chlorine is a non-combustible gas, however most combustible materials will burn in chlorine.

Chlorine is used as a chlorinating and oxidizing agent in organic and inorganic synthesis; in the manufacture of chlorinated solvents, automotive antifreeze and antiknock compounds, polymers (synthetic rubber and plastics), resins, elastomers, pesticides, refrigerants, and in the manufacture of rocket fuel. Chlorine is used as a fluxing, purification, and extraction agent in metallurgy. Chlorine is used as a bacteriostat, disinfectant, odor control, and demulsifier in treatment of drinking water, swimming pools, and in sewage. Chlorine is used in the paper and pulp, and textile industries for bleaching cellulose for artificial fibers; use in the manufacture of chlorinated lime; use in detinning and dezincing iron; use to shrink-proof wool. Chlorine is used in the manufacture of pharmaceuticals, cosmetics, lubricants, flameproofing, adhesives, in special batteries containing lithium or zinc, and in hydraulic fluids; use in the processing of meat, fish, vegetables, and fruit. Chlorine is used as bleaching and cleaning agents, and as a disinfectant in laundries, dishwashers, cleaning powders, cleaning dairy equipment, and bleaching cellulose.

Bulk liquid chlorine, created by compressing pure chlorine gas, has been used throughout the history of disinfection. Due to the hazardous nature of the liquid chlorine, engineering and management controls are employed to minimize risks associated with its handling and use. As an alternative to using liquid chlorine, chlorine as aqueous hypochlorite, an inherently safer form, is commercially available and frequently used in the water treatment industry. Gas chlorination of swimming pools is accomplished by dissolving chlorine gas in a flowing stream of water and then injecting this stream into the recirculation system. The gas and water are mixed in a chlorinating device that is adjustable to control the feed rate.

Chlorine is a greenish-yellow, noncombustible gas at room temperature and atmospheric pressure. Chlorine is only slightly soluble in water, but on contact with moisture it forms hypochlorous acid (HClO) and hydrochloric acid (HCl); the unstable HClO readily decomposes, forming oxygen free radicals. Because of these reactions, water substantially enhances chlorine's oxidizing and corrosive effects. The intermediate water solubility may not cause upper airway symptoms for several minutes. In addition, the density of the gas is greater than that of air, causing it to remain near ground level and increasing exposure time. Chlorine can be detected by odor at 0.3 to 0.5 parts per million, but distinguishing toxic air levels would be difficult until irritative symptoms are present.

Chlorine gas is highly corrosive when it contacts moist tissues such as the eyes, skin, and upper respiratory tract. Frequent exposure to chlorine gas can degrade an individual's sense of smell; workers with occupational exposure to the gas are at greater risk of inhalational damage in later years. Low concentrations of chlorine gas irritate the nasal passages and constrict the chest. In larger amounts, chlorine gas causes death by asphyxiation. As little as 3.5 ppm can be detected as an odor. The lowest lethal concentration reported is 430 ppm for 30 minutes. Exposure to 15 ppm causes throat irritation, exposures to 50 ppm are dangerous, and exposures to 1000 ppm can be fatal, even if exposure is brief -- 1000 ppm is likely to be fatal after a few deep breaths. Approximately 19,000 mg·min/m3 is lethal dose to 50 percent of exposed adults.

The extent of poisoning caused by chlorine depends on the amount of chlorine a person is exposed to, how the person was exposed, and the length of time of the exposure. When chlorine gas comes into contact with moist tissues such as the eyes, throat, and lungs, an acid is produced that can damage these tissues.

Chlorine is one of the most commonly manufactured chemicals in the United States. Its most important use is as a bleach in the manufacture of paper and cloth, but it is also used to make pesticides (insect killers), rubber, and solvents. Chlorine is used in drinking water and swimming pool water to kill harmful bacteria. It is also as used as part of the sanitation process for industrial waste and sewage.

In 1863 Confederates use chlorine-filled artillery shells against Union forces. Of the 70,552 American soldiers poisoned with gasses during World War I, 1,842 were exposed to chlorine gas. First used as a chemical weapon at Ypres, France in 1915, chlorine gas acts a pulmonary irritant that causes acute damage in the upper and lower respiratory tract. By the end of World War I, Germany, France and the United Kingdom had all used chlorine gas. Not very efficient and in low concentrations, it was observed that even rudimentary protection would prevent a soldier from succumbing to its full effects. Its use, however, was still enough to cause "gas hysteria" during an attack.

Though not currently considered a battlefield weapon, there have been reports of its use in recent times. In the late 1990s, media sources quoted Bosnian soldiers as bragging they possessed gas grenades and other mortar weapons against Serbian forces. Croatia's UN mission issued a press statement confirming that the Bosnian Muslim forces were using gasses and that the agent was most likely chlorine gas.

Chlorine is not listed as a Scheduled Chemical in the CWC.

Between 1965 (the earliest data available) and 2006 there had been at least 2.2 million tank car shipments of chlorine-only 788 of which were involved in accidents (0.036 percent of all the shipments). Of those accidents, there were 11 instances of a catastrophic loss (i.e., a loss of all, or nearly all) of the chlorine lading (0.0005 percent of all the shipments). Of the 11 catastrophic losses, four resulted in fatalities (0.00018 percent of all the shipments). On June 28, 2004, a Union Pacific Railroad Company (UP) train collided with a Burlington Northern and Santa Fe Railway Company (BNSF) train in Macdona, Texas, breaching a loaded tank car containing chlorine and causing the deaths of three people. On January 6, 2005, a Norfolk Southern Railway Company (NS) train collided with a standing train on a siding in Graniteville, South Carolina. That accident resulted in the breach of a tank car containing chlorine, and nine people died from inhalation of chlorine vapors.

Although not a terrorist incident, the release of chlorine in Graniteville added to the growing concern about terrorism and prompted the development of the Freight Rail Security Program. Roughly 10 million tons of toxic inhalation hazard (TIH) chemicals are shipped by rail in the United States every year. This is a fraction of the 3.1 billion tons of hazardous materials shipped annually by all modes of transportation. However, a terrorist attack against a train carrying TIH in an urbanized area could endanger significant numbers of people.

In December 2003 a coalition of groups released a report contending that 19 million people in the United States face a major health threat in a terrorist attack or accident because they live near sewage treatment plants that use chlorine gas. The report recommended that plants using chlorine gas switch to alternatives such as solid disinfectants or ultraviolet light to kill microorganisms.

Emergency Response Unit personnel, Iraqi Police, and civilians northwest of Ramadi were attacked by a suicide vehicle-born improvised explosive device (SVBIED) 29 January 2007. Coalition forces responded to the attack to provide immediate medical assistance and evacuate the wounded to medical facilities. Along with the suicide bomber, 16 people were killed by the attack. The SVBIED was a dump truck filled with explosives and included a chlorine tank. The truck crashed into the Emergency Response Unit compound and detonated. There are no indications of any casualties caused by the release of chlorine gas.

Insurgents blew up a tanker filled with chlorine 21 February 2007 in southern Baghdad. The attack killed at least two people and wounded more than 30. Coalition officials in Baghdad said this could be an escalation in the insurgent attacks.