VX NERVE GAS

VX is the most toxic nerve agent ever synthesized for which activity has been independently confirmed.[5] The median lethal dose (LD50) for humans is estimated to be about 734 micrograms through skin contact and the LCt50 for inhalation is estimated to be 30-50 mg·min/m³.[6]

Early symptoms of percutaneous exposure (skin contact) may be local muscular twitching or sweating at the area of exposure followed by nausea or vomiting. Some of the early symptoms of a VX vapor exposure to nerve agent may be rhinorrhea (runny nose) and/or tightness in the chest with shortness of breath (bronchial constriction). Miosis (pinpointing of the pupils) may be an early sign of agent exposure but is not usually used as the only indicator of exposure.[7]
[edit] Treatment

Primary consideration should be given to removal of the liquid agent from the skin before removal of the individual to an uncontaminated area or atmosphere. After removal from the contaminated area, the casualty will be decontaminated by washing the contaminated areas with household bleach and flushing with clean water. After decontamination, the contaminated clothing is removed and skin contamination washed away. If possible, decontamination is completed before the casualty is taken for further medical treatment.

An individual who has received a known nerve-agent exposure or who exhibits definite signs or symptoms of nerve-agent exposure should immediately have the nerve agent antidote drugs atropine, pralidoxime (2-PAM), and diazepam injected. In several nations the nerve agent antidotes are issued for military personnel in the form of an autoinjector such as the United States military Mark I NAAK.[7]

Atropine works by binding and blocking a subset of acetylcholine receptors (known as muscarinic acetylcholine receptor, mAchR), so that the build up of acetylcholine produced by loss of the acetylcholinesterase function can no longer affect their target. The injection of pralidoxime regenerates bound acetylcholinesterase.
[edit] Diagnostic tests

Controlled studies in humans have shown that minimally toxic doses cause 70-75% depression of erythrocyte cholinesterase within several hours of exposure. The serum level of ethyl methylphosphonic acid (EMPA), a VX hydrolysis product, was measured to confirm exposure in one poisoning victim.[8]
[edit] History

For an in-depth discussion, see main article on nerve agent history

The chemists Ranajit Ghosh and J.F. Newman discovered the V-series nerve agents at ICI in 1952, patenting diethyl S-2-diethylaminoethyl phosphono- thioate (agent VG) in November, 1952. Further commercial research on similar compounds ceased in 1955 when its lethality to humans was discovered. Information on the substance was passed to Porton Down in 1954 and research there led to VX within a year. This was traded to the United States as the British passed over VX in favor of continuing with sarin as the UK chemical weapon of choice, the reasoning behind the decision is unclear, although the then recent completion of a sarin production facility at Nancekuke may have played a part.

The US then went into production of large amounts of VX in 1961 at Newport Chemical Depot.

Iraq under Saddam Hussein admitted to UNSCOM that it had researched VX, but had failed to weaponize the agent due to production failure. After U.S. and allied forces had invaded Iraq, no proof of weaponized VX was found.[9] Subsequent investigation after the 2003 Invasion of Iraq indicates that Iraq had indeed weaponized VX in 1988, and had dropped three VX-filled bombs on Iran.[10]

In December 1994 and January 1995, Masami Tsuchiya of Aum Shinrikyo synthesized 100 to 200 grams of VX which was used to attack three persons. Two persons were injured and one 28-year-old man died, who is believed to be the only victim of VX ever documented in the world.[11] The VX victim, whom Shoko Asahara had suspected as a spy, was attacked at 7:00 am on December 12, 1994 on the street in Osaka by Tomomitsu Niimi and another AUM member, who sprinkled the nerve agent on his neck. He chased them for about 100 yards (100 m) before collapsing, dying 10 days later without ever coming out of a deep coma. Doctors in the hospital suspected at the time he had been poisoned with an organophosphate pesticide. But the cause of death was pinned down only after cult members arrested for the subway attack confessed to the killing. Ethyl methylphosphonate, methylphosphonic acid and diisopropyl-2-(methylthio) ethylamine were later found in the body of the victim. Unlike the cases for sarin (Matsumoto incident and Sarin gas attack on the Tokyo subway), VX was not used for mass murder.

The only countries known to possess VX are the United States and Russia.[5] A Sudanese pharmaceutical facility was bombed by the U.S. in 1998 acting on information that it used VX and that the origin of the agent was associated with both Iraq and Al Qaeda.[9][12] The chemical in question was later identified as O-ethyl hydrogen methylphosphonothioate (EMPTA), used as a precursor in the production of VX. It is also used to treat seeds and turf grasses