Former Russian spy Sergei Skripal and his daughter Yulia were exposed to a nerve agent known as Novichok, prime minister Theresa May told MPs on Monday.
The Skripals are still seriously ill in hospital and – from what is known about this lethal agent – their long term prognosis is unlikely to be good even if they survive in the short term.
Novichok was identified as the compound used in the attack by experts at the science and Defence Science and Technology Laboratory at Porton Down.
Novichok is not a single toxin but a family of so called “fourth generation” nerve agents developed by the Russians in the 1970s and 1980s. In some forms, it is reported to be 5-8 times more toxic than earlier nerve agents such as VX.
It can be stored as two less toxic chemical ingredients which, when mixed, react to produce the weaponsised nerve agent. This makes it easier to transport and handle – an advantage for an assassin.
Michelle Carlin, senior lecturer in forensic and analytical chemistry at Northumbria University, said that it can be used in the form of an ultra-fine powder as well as as a liquid or vapour.
It kills after being ingested or absorbed through the skin.
Public Health England (PHE) says the risk to the public in Salisbury is “extremely low” and there is not thought to be any risk currently from Novichok beyond the immediate area. However, it has advised anyone who was in the Mill pub or Zizzi’s restaurant in Salisbury between 1.30pm on Sunday 4 March and closing time on Monday 5 March to take precautions.
You should clean clothing and items you had with you while you were there.
Clothing that is dry-clean only should be put in two plastic bags (ie. a double layer), tied at the top and stored safely – PHE is reviewing the best way of cleaning these items and will publish information in due course.
Items such as phones and handbags should be cleaned with baby wipes. Jewellery, watches and glasses should be washed with warm water and detergent and then rinsed in clean cold water.
Public Health England says this is not necessary but if you want to do this put them in two plastic bags, tie them at the top and dispose of it in an outdoor bin in the normal way.
It has taken investigators several days to confirm the type of toxin used in the attack and Public Health England has taken some time to react.
“The actions we advise are purely precautionary but will eliminate any possible risk,” a spokesman said.
Novichok, like all nerve agents, disrupts the chemical signals between the nerves and the muscles which control vital organs, said Dr Carlin. “This can lead to breathing difficulties, loss of control of bodily functions, increased salivation, convulsions, paralysis.”
Outward symptoms may include white eyes, convulsions, drooling and, in the worse cases, coma, respiratory failure and death.
Nerve agents can act within minutes but they can also take hours to take effect. Much depends on the exact toxin, the dose and the delivery method.
Patients exposed to nerve agents are normally given the drug atropine, which reduces muscle spasms and the production of saliva. It needs to be given as soon after exposure as possible – ideally within minutes.
It is likely that atropine was used to treat the Skripals, said Alastair Hay, emeritus professor of environmental toxicology at the University of Leeds.
Doctors may also use a drug called pralidoxime, an antidote to organophosphate pesticides and chemicals.
Little is known about this, although exposure is thought to lead to long-term harm. One of the Russian scientists who helped develop Novichok, Andrei Zheleznyakov, was accidentally exposed and, according to a book about the history of chemical weapons, War of Nerves by Jonathan Tucker, he suffered permanent ill health including hepatitis, epilepsy, severe depression and an inability to concentrate. He died five years after exposure.
The greatest risk comes from the fact that the taboo on the use of chemical weapons, which has held for much of the last 100 years, appears to be breaking down.
Politician’s must bend every sinew to reestablish this red line, said Hamish De Bretton-Gordon, a former commanding officer of the UK Chemical, Biological, Radiological and Nuclear (CBRN) Regiment.