What is the VX nerve agent that killed North Korea's Kim Jong-nam?
What is VX?
VX is the deadliest nerve poion ever created. Just a tiny drop absorbed through the skin is enough to kill, says the Council on Foreign Relations.
It is 100 times more deadly than the nerve gas sarin, which was used by members of a Japanese doomsday cult in their deadly 1995 attack on the Tokyo subway.
VX is very hard to detect. It is a clear, tasteless and colourless liquid with a consistency something like engine oil.
So potent is VX – its full chemical name is S-2 Diisoprophylaminoethyl methylphosphonothiolate – that the UN classifies it as a weapon of mass destruction. The Centres for Disease Control, the US government’s top public health agency, says its only known use is in chemical warfare.
Where does it come from?
VX was first made by in the early to mid-1950s Ranaji Ghosh, a chemist working for the British firm Imperial Chemical Industries.
Its toxicity and physical properties were studied by warfare specialists in Britain, who passed the formula on to the US military, says the National Academies of Sciences, Engineering and Medicine in Washington. The US began full-scale production of VX in 1961.
The US army was involved in several controlled and accidental releases of VX gas. Iraq was reported to have more than 50 tonnes. Under Saddam Hussein, Iraq is thought to have used VX in a 1988 attack against the Kurds and during the Iran-Iraq war.
Who has VX?
The US and Russia are the only countries that have admitted owning VX stockpiles, but more countries are believed to hold it.
The US destroyed a small portion of its stockpile under the Chemical Weapons Convention and Russia may do the same.
According to a French intelligence assessment published in September 2013, Syria’s chemical weapons stockpile includes “several tens of tonnes” of VX.
While the Aum Supreme Truth doomsday cult used sarin gas in its subway attack, it is believed to have used VX injections in assassination attempts on several dissident members and cult opponents. One person was reported to have died.
North Korea claims it has never had a chemical weapons programme. But in fact it is believed to possess between 2,500 and 5,000 tonnes – behind only the US and Russia – including VX, says to the Nuclear Threat Initiative .
“The South Korean government thinks that North Korea can produce most types of chemical weapons, although it must import some ingredients to produce nerve agents, which it has done in the past,” the NTI said.
“At maximum capacity North Korea is estimated to be capable of producing up to 12,000 tons of [chemical weapons]. Nerve agents such as sarin and VX are thought be to be the focus of North Korean production.”
How does it affect the body?
Nerve agents are the most toxic and fast acting of the known chemical warfare agents, says the CDC.
The “V” in VX stands for venom, “a tribute to this compound class having high potency and a characteristic ability to penetrate the skin”,says the National Academies website .
The centre said exposure to near-lethal and lethal doses quickly causes victims to faint, convulse, became paralysed and stop breathing. Just 10 milligrams of VX on the skin is enough to kill.
It is possible to treat a VX attack with an injection of lots of antidotes, but the nerve agent works so quickly that a victim would have to be treated immediately to stand any chance of survival.