VX nerve agent: What is it and how does it work?

VX nerve agent: What is it and how does it work?

A primer on ethyl S-2-Diisopropylaminoethyl methylphosphonothiolate, or VX nerve agent, which Malaysian authorities said was used to kill a North Korean man at Kuala Lumpur International Airport.

Toxic gas mask

SINGAPORE: Malaysian authorities on Friday (Feb 24) said a chemical weapon, VX nerve agent, was used to kill a man believed to be the half-brother of Kim Jong Un at Kuala Lumpur International Airport on Feb 13.

The substance is a chemical weapon classified as a weapon of mass destruction by the United Nations.


VX is a tasteless and odourless amber-coloured oily liquid. It is outlawed under the Chemical Weapons Convention, except for "research, medical or pharmaceutical purposes".

VX is a human-made chemical warfare agent classified as a nerve agent. Nerve agents are the most toxic and rapidly acting of the known chemical warfare agents. Just 10 milligrammes of the nerve agent or a single drop is enough to kill in minutes, according to experts.

"You can think of VX as being a pesticide on steroids, this is an extraordinarily toxic substance," said Bruce Bennet, defence researcher at California-based RAND Corporation. "Roughly 1/100th of a gramme, a third of a drop, on someone’s skin, will kill them."

According to The Guardian, it is 100 times more deadly than the nerve gas sarin, which was used by the Aum Shinrikyo cult during their fatal attack on a Tokyo subway train.

It was developed in the United Kingdom in the 1950s.


The extent of poisoning depends on how much a victim is exposed to, how the exposure occurred and the length of time of the exposure.

Nerve agents operate by preventing an enzyme that acts as the body's "off switch" for glands and muscles. Without this "off switch", muscles and glands are constantly being stimulated - and after a while this will tire out the affected person, who would no longer be able to sustain a breathing function.

Death is caused by asphyxiation or heart failure.

Because it evaporates so slowly, VX can be a long-term threat as well as a short-term threat. Surfaces contaminated with VX should therefore be considered a long-term hazard, said the US Centers for Disease Control and Prevention (CDC).

VX can last for days on objects in comes into contact with; in colder temperatures, it can last for months on surfaces.


By contamination via skin or if they consume contaminated food or liquids.

Clothing can also release VX after contact with VX vapour, which can lead to exposure of other people through contaminated articles.

VX is considered to be much more toxic by entry through the skin and somewhat more toxic by inhalation. Any visible VX liquid contact on the skin, unless washed off immediately, is believed to be lethal, according to the CDC.


Symptoms after contact with VX in vapour form will appear within a few seconds, and within a few minutes to up to 18 hours after exposure to the liquid form.

Low or moderate dose: Feeling weak, abnormally low or high blood pressure, drowsiness, blurred vision, chest tightness, confusion, cough, diarrhoea, drooling and excessive sweating, headache, increased urination, nausea, vomiting, and/or abdominal pain, rapid breathing, runny nose, slow or fast heart rate, small, pinpoint pupils, watery eyes.

Large dose: Paralysis, convulsions, loss of consciousness, respiratory failure.


Antidotes are available for VX, but because of how quickly this nerve agent works, those affected need to be treated immediately if they are to survive.

Sources: Guardian, CDC, AFP, Reuters

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Source: CNA/rw