VX (nerve agent)

VX 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 its pure form, VX is an oily, relatively non-volatile liquid that is amber-like in colour. Because of its low volatility, VX persists in environments where it is dispersed.

VX, short for "venomous agent X", is one of the best known of the V nerve agents and originated from pesticide development work at Imperial Chemical Industries (ICI). It was developed further 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. To date (2023), VX has not been used in combat, though claims as to its use as a weapon in assassinations have some credibility. The brother of North Korean leader Kim Jong Un, Kim Jong Nam, had the substance thrown in his face in Kuala Lumpur International Airport on the 13th February 2017 by two women. He died being rushed to hospital approximately 15 minutes later.

The substance is extremely deadly; VX fatalities occur with exposure to tens of milligram quantities via inhalation or absorption through skin; VX is 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 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. VX 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 VX exceeding 100 grams (3.53 oz) 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 10 kg (22 lb) per year per facility".