<unk> is an extremely toxic synthetic chemical compound in the organophosphorus class, specifically, a thiophosphonate. 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. In recent years,<unk> was found to be the agent used in the assassination of Kim Jong-nam. In its pure form,<unk> is an oily, relatively non-volatile, liquid that is amber-like in colour. Because of its low volatility,<unk> persists in environments where it is dispersed.<unk> , 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. 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.<unk> fatalities occur with exposure to tens of milligram quantities via inhalation or absorption through skin;<unk> is thus more potent than sarin, another nerve agent with a similar mechanism of action. 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. The danger of<unk> , 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.<unk> is considered an area denial weapon due to these physical and biochemical characteristics. 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<unk> exceeding per year is outlawed. The only exception is for "research, medical or pharmaceutical purposes outside a single small-scale facility in aggregate quantities not exceeding per year per facility".
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