As a chemical weapon, it is categorized as a weapon of mass destruction by the United Nations and is banned by the Chemical Weapons Convention of 1993, where production and stockpiling of VX exceeding 100 grams (3.53 oz) per year is outlawed. VX is considered an area denial weapon due to these physical and biochemical characteristics. The danger of VX, in particular, lies in direct exposure to the chemical agent persisting where it was dispersed, and not through its evaporating and being distributed as a vapor - it is not considered a vapor hazard due to its relative non-volatility. On such exposure, these agents severely disrupt the body's signaling between the nervous and muscular systems, leading to a prolonged neuromuscular blockade, flaccid paralysis of all the muscles in the body including the diaphragm, and death by asphyxiation.

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. It is now one of a broader V-series of agents which are classified as nerve agents and have been used as a chemical weapon in various recorded deadly attacks. VX, short for 'venomous agent X', is one of the best known of the V nerve agents and was first discovered at Porton Down in England during the early 1950s based on research first done by Gerhard Schrader, a chemist working for IG Farben in Germany during the 1930s. Because of its low volatility, VX persists in environments where it is dispersed. In its pure form, VX is an oily, relatively non-volatile, liquid that is amber-like in color. In recent years, VX was found to be the agent used in the assassination of Kim Jong-nam. In the class of nerve agents, it was developed for military use in chemical warfare after translation of earlier discoveries of organophosphate toxicity in pesticide research. VX is an extremely toxic synthetic chemical compound in the organophosphorus class, specifically, a thiophosphonate.

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