VX (nerve agent)

VX is a highly 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.

The substance is lethal in very small quantities: fatalities occur with exposure to tens of milligrams of VX via inhalation or absorption through skin. It 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.

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. VX has been allegedly used in warfare and has been used in several assassinations.

As it is dangerous due to its persistence rather than as a vapor hazard, VX is considered an area denial weapon. 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".

During the Cold War, the United States chemical weapons program concentrated on large-scale VX production, producing at least 4,400 tons, alongside sarin and mustard gas. The Soviet chemical weapons program declared production of 15,557 tons of the similar VR nerve agent, also called "Russian VX". There are unconfirmed reports VX was used by Cuban forces in the Angolan Civil War, and by Iraqi forces in the Iran–Iraq War. The first confirmed attacks and killing using VX were strings of assassination attempts by Aum Shinrikyo, a Japanese doomsday cult, in 1994 and 1995. Three men were hospitalized and one died four days later. On February 13, 2017, Kim Jong Nam, was assassinated in Kuala Lumpur International Airport, widely believed to be ordered by his brother, North Korean leader Kim Jong Un. He died within 15 minutes of exposure.