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VX (nerve agent)

Belongs to subject Disease due to physical and chemical agents

Chemical compound and chemical warfare nerve agent

VX is an extremely toxic synthetic chemical compound in the organophosphorus class, specifically, a thiophosphonate. Because of its low volatility, VX persists in environments where it is dispersed. Now one of a broader V-series of agents, they are classified as nerve agents and have been used as a chemical weapon in various recorded deadly attacks. VX fatalities occur with exposure to tens of milligram quantities via inhalation or absorption through skin; VX is thus more potent than sarin, another nerve agent with a similar mechanism of action. VX is considered an area denial weapon due to these physical and biochemical characteristics. VX is an odorless and tasteless chiral organophosphorous chemical with a molecular weight of 267.37 g/mol. VX is an acetylcholinesterase inhibitor. However, compared with other highly toxic nerve agents like soman or sarin, VX undergoes relatively slow "aging.Slower aging by VX suggests it should be possible to develop more effective antidotes and treatments. VX is chiral at its phosphorus atom. VX is produced via the transester process, which gives a racemic mixture of the two enantiomers. Finally, this immediate precursor is reacted with sulfur to form VX.

VX can also be delivered in binary chemical weapons which mix in-flight to form the agent prior to release. Binary VX is referred to as VX2, and is created by mixing O-(2-diisopropylaminoethyl) Like other organophosphorus nerve agents, VX may be destroyed by reaction with strong nucleophiles. The reaction of VX with concentrated aqueous sodium hydroxide results in two competing solvolysis reactions: cleavage of either the P–VX is a "particularly toxic nerve agent". When treating VX exposure, primary consideration is given to removal of the liquid agent from the skin, before removal of the individual to an uncontaminated area or atmosphere. 2-PAM reactivates the acetylcholinesterase enzyme (AChE), thus reversing the effects of VX. VX and other organophosphates block AChE activity by binding to and covalently inactivating the enzyme via transfer of the phosphonate moiety from VX to the active site of AChE; this inactivates AChE and produces an inactive bybroduct from the remaining portion of the VX molecule. There also exist procedures for determination of VX hydrolysis products in urine and of VX adducts to albumin in blood.

The U.S. started production of large amounts of VX in 1961 at Newport Chemical Depot. After the evaluation was complete, several members of this class of compounds became a new group of nerve agents, the V agents. Beginning in 1959, the United States Army began volunteer testing of VX in humans. Patients demonstrating symptoms of exposure to nerve agents first began appearing in Angolan hospitals around 1984. There was evidence of a combination of chemical agents having been used by Iraq against the Kurds in the Halabja chemical attack in 1988 under Saddam Hussein, including VX. Hussein later testified to UNSCOM that Iraq had researched VX, but had failed to weaponize the agent due to production failure. After U.S. and allied forces invaded Iraq, no VX agent or production facilities were found. However, UNSCOM laboratories detected traces of VX on warhead remnants. The VX victim, whom Shoko Asahara had suspected as a spy, was attacked at 7:00 According to the authorities he was murdered by poisoning with VX which was found on his face. The authorities further reported that one of the women suspected of applying the nerve agent experienced some physical symptoms of VX-poisoning. The director of a non-proliferation research program of the Middlebury Institute of International Studies at Monterey stated that VX fumes would have killed the suspected attackers even if they had been wearing gloves, suggesting that the VX was applied as two non-lethal components that would mix to form VX only on the victim's face.

Some countries known to possess VX are the United States, the United Kingdom, Russia, North Korea, and Syria. Cuba obtained VX during the 1980s and deployed it during its lengthy military intervention in Angola. In 1969, the U.S. government cancelled its chemical weapons programs, banned the production of VX in the United States, and began the destruction of its stockpiles of agents by a variety of methods. Incineration was used for VX stockpile destruction starting in 1990 with Johnston Atoll Chemical Agent Disposal System in the North Pacific with other incineration plants following at Deseret Chemical Depot, Pine Bluff Arsenal, Umatilla Chemical Depot and Anniston Army Depot with the last of the VX inventory destroyed on 24 December 2008.

Worldwide, VX disposal has continued since 1997 under the mandate of the Chemical Weapons Convention. When the convention entered force, the parties declared worldwide stockpiles of 19,586 tonnes (21,590 short tons) of VX. The Newport Chemical Depot began VX stockpile elimination using chemical neutralization in 2005. One of the best-known references to VX in popular culture is its use in the 1996 film The Rock, which centers on a threatened VX attack on San Francisco from the island of Alcatraz. The film uses artistic license, notably with VX being ascribed corrosive powers it does not possess, permitting an early scene in which a VX victim is shown with his face melting, rather than dying through asphyxiation.

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