Theresa May has identified the nerve agent used in the attack on Sergei and Yulia Skripal in Salisbury as a novichok. The name, meaning “newcomer”, refers to a group of nerve agents developed by the Soviet Union in the 1970s and 1980s to elude international restrictions on chemical weapons.

Like other nerve agents, they are organophosphate compounds, but the chemicals used to make novichoks, and their final structures, are considered classified in the UK, the US and other countries. By making the novichoks in secret, from benign chemicals normally used for insecticides and the like, the Soviet Union aimed to manufacture them without interference.

“Much less is known about the novichoks than the other nerve agents,” said Alastair Hay, an environmental toxicologist at the University of Leeds who investigated the use of chemical weapons against Iraqi Kurds in Halabja in 1988. “They are not widely used at all.”



The most potent of the novichok substances are considered to be more lethal than VX, the most deadly of the familiar nerve agents, which also include sarin, tabun and soman. And while the novichoks work in a similar way to these, by massively overstimulating muscles and glands, one chemical weapons expert told the Guardian that novichoks do not degrade fast in the environment and have “an additional toxicity”.

“That extra toxicity is not well understood, so I understand why people were asked to wash their clothes, even if it was present only in traces,” he said. Treatment for novichok exposure would be the same as for other nerve agents, with atropine, diazepam and drugs called oximes.

The chemical structures of the main weaponised novichok agents were made public in 2008 by Vil Mirzayanov, a former Russian scientist living in the US, but the structures have never been publicly confirmed. It is thought that they can be made in different forms, including a dust aerosol that would be easy to disperse.

The novichoks are known as binary agents because they become lethal only after two relatively harmless components are mixed together. This means that labs do not have to build stockpiles of ready-made nerve agents but can mix them up from unrestricted chemicals as and when needed. According to Mirzayanov, the most potent of the agents are 10 to 100 times more toxic than the conventional nerve agents.

The fact that so little is known about the novichoks may explain why Porton Down scientists took several days to identify the compound used in the attack against the Skripals. And while the agents were invented in the Soviet Union, other labs with access to the chemical structures would be able to manufacture them too.