CBRN / HazMat Training Blog

The Most Deadly of Nerve Agents: VX

Written by Steven Pike on 28 March 2024


The deadly nerve agent VX was used in the assassination of Kim Jong Un’s half-brother, Kim Jong Nam. It is the most lethal of the nerve agents produced, more so than Sarin, and has an interesting if shadowy history.

Death of an Exile

Kuala Lumpur International Airport was the unlikely scene of one of the last known uses of the deadly nerve agent VX. In February 2017, Kim Jong Nam, the elder half-brother of the North Korean leader Kim Jong Un, was preparing to take a return flight to his home in exile in Macau. He was approached and ambushed by two young women with a mysterious substance. Despite receiving immediate first aid, including an emergency tracheal intubation, Kim Jong Nam succumbed to death in considerable pain just 15 to 20 minutes later. While it was quickly established that the unfortunate Kim Jong Nam had been smeared with a toxic substance, the violent and rapid onset of death caused considerable speculation as to what substance could have been administered that was so fast-acting.

The revelation came when Malaysian authorities announced that the substance smeared across the victim’s face was VX nerve agent. VX is considered a weapon of mass destruction and is banned under the 1993 Chemical Weapons Convention.

Origins of VX

VX is not just any nerve agent, but is widely agreed to the most potent of all of them, including Sarin, an agent originally developed in Germany in 1938 as a pesticide. VX like Sarin, is chemically related to and was developed from pesticides, although it is far stronger in degrees of magnitude. When produced, VX exists as an oily liquid, amber in colour, odourless and tasteless.

This lethality and difficulty in detection is probably what attracted British scientists working at the secret nuclear, biological, and chemical facility at Porton Down in Wiltshire to its application as a chemical weapon in the 1950s. They knew of the lethal properties of the agent having been briefed by scientists at Imperial Chemical Corporation (ICI) who abandoned its development as a pesticide in 1955, after its lethality to humans began to be fully understood. Sometime in the late 1950s, the fruits of the Porton Down research were transferred to the United States, and the production and weaponisation of VX became a major part of the growing U.S. chemical weapons capability programme that took place during the 1960s.

Why is VX so Lethal?

Much of the lethality of VX is derived from its persistence in the environment – it evaporates slowly, especially in cold conditions, making it both a long and short-term threat. Like all nerve agents, VX stops a vital enzyme from working – which eventually leads to the body tiring, and no longer being able to breathe. Depending on how much agent a person has been exposed to, symptoms will start occurring either immediately or up to 18 hours later. In larger doses, convulsions, loss of consciousness, paralysis, and death due to respiratory failure will occur rapidly. While the agent could be released into a water supply or used to poison someone’s food, the vapor form of VX is the deadliest – and the quickest – to kill.

Those who planned the assassination of Kim Jong Nam knew what they were doing.

Has VX been Used Elsewhere in Anger?

VX agent has been included in the chemical weapon armouries of the U.S. Russia, Syria, and North Korea. Fortunately, the 30,000 tonnes of VX that the U.S. produced was never used in anger, and the 18,000 VX filled artillery shells and missiles were destroyed. A 1988 UN report concluded that Cuban armed forces had used VX during operations in the Angolan civil war. Inspectors had found soil traces of VX in areas where Cuban forces had been conducting counter-insurgency operations and the symptoms of Angolan civilians who began appearing in local hospitals was consistent with VX contamination.

Saddam Hussein admitted to UN inspectors that his regime had experimented with VX and traces of VX were found upon the remains of destroyed munitions. However, no evidence was found that suggested that the Iraqis under Saddam had successfully weaponised VX.

Outside of military use, proponents of asymmetric conflict have employed its deadly properties in individual attacks. The terrorist group Aum Shinrikyo led by Shoko Asahara, synthesised a small quantity of VX which was used to eliminate a member of the group suspected of spying. Later, Aum Shinrikyo turned to Sarin to carry out its deadly attack on the Tokyo metro system in 1995.

Is VX Still Around?

The U.S. cancelled its chemical weapons programme in 1969. Progress on the  arms reduction and limitation culminated in the 1993 Chemical Weapons Convention which saw VX banned. The U.S undertook the task of destroying its VX stocks by a variety of methods, some of which were questionable. The sinking of large stockpiles at sea, when discovered, caused particular concern. Elsewhere, upon the CWC coming into force, a staggering 19,000 tonnes of VX were declared by non-U.S. parties to the Convention.

The collapse of the Soviet Union led to international concern at the risk of weapons of mass destruction (WMD) falling into hostile hands. U.S. led programmes assisted in the conversion of Russian chemical weapons testing and storage sites into destruction facilities. However, these programmes resulted at best in the destruction of 15-20% of the known former Soviet Union stocks. While the OPCW (Organisation or the Prohibition of Chemical Weapons) declared Russian VX stockpiles destroyed in 2017. However, there remains some scepticism regarding whether full destruction actually occurred.

North Korea is not a signatory to the ’93 CWC, and the size status and intention for its known stockpile of VX can only be guessed. It is of course available to dip into for the elimination of troublesome family, although that country hotly denies the accusation.

Is VX Still a Threat?

VX cannot be uninvented. Its chemical makeup and properties are well known, and it is reasonably easy to synthesise, although weaponisation at an industrial scale is more problematic. While responsible nations have sought to restrict, limit, and destroy stocks of VX, the potential attractiveness of its non-volatility and lethality means there is no certainty that rogue nations or violent non-state actors may not turn to it again.

As we work to refine and hone CBRN detection and defence capabilities, it is worth remembering that VX is a nerve agent unique amongst its chemical warfare stablemates in that it has not a single non-military purpose.

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Topics: Chemical warfare

Steven Pike

Written by Steven Pike

Steven Pike is the Founder and Managing Director of Argon Electronics (UK) Ltd. A graduate of the University of Hertfordshire, Steven has been awarded a number of international patents relating to the field of hazardous material training systems and technology.