Last week a retired Russian spy and his daughter were poisoned by novichok, a nerve agent, in Salisbury, England. Officials are concerned that anyone who visited the restaurant or pub the man and his daughter went to that day are at risk of being poisoned themselves. Traces of novichok, which is similar to the poison used in the double assassination, were found at both places.

The Russian scientist who developed novichok says anyone exposed to minuscule traces of it could be affected by it, even years later.

From Sky News:

Dr Vil Mirzayanov is a chemist who ran the technical counter-intelligence department in Russia's chemical weapons institute.

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More than two decades ago, Dr Mirzayanov became so concerned about novichok that he blew the whistle and fled to America, where he campaigned to get all chemical weapons banned.

He spoke to Sky News at his home in Princeton in New Jersey.

He said: "It's the same as nerve gas but 10 times, at least 10 times, more powerful."

The scientist emphasised that Novichok was designed to do "irreparable" damage to the human body.

He said it would leave those exposed to significant doses, like Mr Skripal and his daughter, as "invalids" who would need medical assistance for the rest of their lives.

Image: Members of the hazardous materials entry team, wearing chemical protective suits, enter building 836 to sample for nerve agents on Maxwell Air Force Base during a nerve-agent exercise Jan 17. (U.S. Air Force photograph by Donna L. Read the rest