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Russian ex-spy Alexander Litvinenko who was investigating the murder of journalist Anna Politkovskaya has been assassinated by radioactive poisoning, polonium-210 to be precise, which is something extremely difficult to obtain unless you work for the secret services of a country with nuclear capabilities of course.

Radioactive element found in blood of Russian ex-spy

Traces of radioactive polonium have been found in the blood of the deceased Russian ex-spy Alexander Litvinenko, the UK’s Health Protection Agency (HPA) said on Friday. His urine also tested positive for radiation.

“This is an unprecedented event in the UK,” said HPA chief executive Pat Troop. “It is the first time someone in the UK has apparently been deliberately poisoned with a radioactive agent.”

The agency is now assessing the health risks posed to members of the public who may have come into contact with Litvinenko, including family members and hospital staff who cared for him during the weeks he spent in hospital. They are also trying to decide the safest way for pathologists to conduct an autopsy of his body, and indeed whether such a procedure is safe enough to be performed at all.

Litvinenko, aged 43, died on Thursday of heart failure after claiming he had been poisoned in a London restaurant. He was formerly an agent of the Soviet, then the Russian, security service. He specialised in investigating organised crime and its involvement with corrupt officials.

High levels of radiation have been discovered in a central London hotel that Litvinenko frequented, and at the sushi restaurant where he said he ate on 1 November 2006. The restaurant has now been closed, said the HPA.

“Tests have established that Mr Litvinenko had a significant quantity of the radioactive isotope polonium-210 in his body,” the HPA announced on Friday. “It is not yet clear how this entered his body. Police are investigating this.”

Dissolvable salt

Litvinenko was not admitted to London's University College Hospital until 17 November. His symptoms, reported to include hair loss, dehydration, vomiting and a very low white blood cell count, are consistent with poisoning by a radioactive material.

To poison someone, polonium would most likely have been chemically combined in some type of dissolvable salt, for example polonium nitrate, experts told New Scientist. In this form the material could easily have been added to his food and ingested.

Polonium is a radioactive element that is used industrially as an anti-static material. It is difficult to get hold of and not used regularly by research scientists, but very small traces of it occur naturally. The metal is usually made by bombarding the element bismuth with neutrons.

"To poison someone, large amounts of polonium-210 are required and this would have to be manmade, perhaps from a particle accelerator or a nuclear reactor," said Dudley Goodhead at the UK's MRC Radiation and Genome Stability Unit. “Polonium has a half-life of 138 days. This means that if that was the poison it will still be in the body and in the area – which makes it relatively easy to identify.”

Knocking out electrons

Polonium-210 decays to lead-206, which is stable. During the decay it emits alpha particles – two neutrons combined with two protons. These are not able to penetrate most materials, including skin. This means that Litvinenko would have had to ingest the polonium or have it enter his body through a wound or by inhaling it, said Roger Cox, director of the UK’s Centre for Radiation, Chemical and Environmental Hazards.

“Alpha particles are ionising. When they strike tissue they knock electrons out of molecules. Such damage can in serious cases wreck cellular machinery resulting in cancer, radiation sickness, or worse," said chemist Andrea Sella at University College London.

But the short-range action of alpha particles decreases the risks faced by people who may have come into contact with Litvinenko. Normal hygiene practices would reduce the risks still further, since people would have to ingest or breathe in his bodily fluids or faeces to be at risk, Cox added.

Many details are still unknown, such as how much of the material may have been given to Litvinenko. Cox was only able to say that a fatal dose would have to be something greater than 5 grays (a gray is a measurement of the amount of radiation absorbed by body tissue).

Organ malfunction

Determining the amount of polonium originally given will involve a “backwards analysis”, taking into consideration the radiation currently in his body, the days that have passed since it entered his body, and the half-life of the isotope.

In low doses over a long period of time, radiation poisoning produces few symptoms, but an increased risk of cancer. In high doses – as in this case, apparently – organs begin to malfunction within a few days to a few weeks, Cox said.

Radioactive poisoning was once used against dissidents by the Stasi, the former security service of East Germany. The Stasi favoured the element scandium (see Cold war, hot secret).

Litvinenko left Russia after reportedly falling out with President Vladimir Putin over a failure to crack down on corruption. His job is said to have made him many enemies. Those enemies, he claimed, poisoned him at a meal in a London restaurant on 1 November 2006. He was reportedly a close associate of exiled Russian billionaire Boris Berezovsky, himself a politically controversial figure in Russia.

On Friday, the British Home Secretary John Reid stated that police have called in experts “to search for any residual radioactive material at a number of locations".

New Scientist

And a BBC article.