Novichok remains active long after it is used and people could be poisoned by picking things up, experts warn

'They are designed to be quite persistent'

The clean-up in Salisbury after the first attack, which authorities insist removed all threat from the areas affected (ADRIAN DENNIS/AFP/Getty Images)

Novichok nerve agents can stay in the environment for a long time after they are used and people could easily be poisoned by contaminated objects, experts have warned.

Attention has turned to the deadly weapons once again after it emerged that a couple in Amesbury had also been the victim of the weapon, long after the Skripals were poisoned nearby and after what appeared to be a comprehensive clearup operation.

It is a reminder of the potency of nerve agents, developed as deadly weapons. And it also serves to show just how long-lasting their effects are, with traces hanging around for a long time after it is used and potentially contracted from contact in passing.

Public Health England warned people not to pick up discarded objects, as part of the working assumption that the couple came into contact with the substance by accident, rather than being intentionally targeted.

While health experts said that the risk to the public was still very low indeed, repeating advice that people who are concerned make sure to wash their clothes and clean their belongings with wipes. But they also noted that the incident is a demonstration of the danger posed by the agents themselves.

“Confirmation that this was the same chemical agent that poisoned the Skripals really confirms a lot of things that we believed were true about this ‘novichok’ class of nerve agents," said Andrea Sella, professor of inorganic chemistry at UCL.

"They are designed to be quite persistent – they hang around in the environment, neither evaporating or decomposing quickly. That means that if a container or a surface was contaminated with this material it would remain a danger for a long time and it will be vital to trace the movements of this couple to identify where they might have come into contact with the source. So while the public at large are at very low risk from this material, until the source is found there is a remote chance that someone else might come into contact with it.

“Some people online are saying that the fact that the investigating teams are wearing hazmat suits suggests that there is something “we are not being told”, but this is a purely precautionary measure given that until a few hours ago the authorities did not know what they were dealing with."

It is still not clear how the couple in Amesbury came to be affected by the nerve agent. But experts were clear that it did not mean the clean-up procedures were not working.

Professor Paul Cosford, medical director of Public Health England, told the Today programme: "The sites that were the subject of the clean-up after Skripal are not associated with this incident.

"So there should not be any concern that the clean-up after the previous incident has not worked here."

Chemical weapons expert Hamish de Bretton-Gordon said the latest victims are likely collateral debris from the Skripal attack.

"The Novichok gel that was smeared on the handle of the Skripals' house was presumably transported in some device or syringe," he said. "I think the working assumption now is that device or that syringe is what has appeared and the residue caused these two people to become ill."

Vladimir Uglyov, one of the men credited with inventing the “novichok” series of nerve agents, told The Independent that he wasn’t surprised that the substance had hung around.

“Unlike some of my colleagues, I’ve always said that it is very stable,” he said. “It can persist for years, with nothing much happening to it. ”There is a very, very, slow process of evaporation.”

According to the now-retired scientist, “novichok” can bury itself in paint, trees, and, perhaps, in wooden benches: “It can get in and remain there for a very long time. If it is on a neutral surface, it will only degrade on account of evaporation. And that would be a long process.”