Former Russian spy Alexander Litvinenko has been in the international news after suddenly falling ill earlier this month, then dying on 23 November. The cause of his illness confounded his physicians, who initially postulated that might have been poisoned with thallium. However, in a surprising twist, the cause of death now appears to be poisoning with radioactive polonium-210 (210Po). That is, the poison did not work by the usual chemical means, but instead released radiation as it decayed inside his body. Given this unusual method of toxicity, officials in the United Kingdom are now trying to determine how next to proceed. Debora MacKenzie writes in the New Scientist
“This is an unprecedented event in the UK,” said HPA [Health Protection Agency] 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.
Polonium is an extremely rare element. It has an atomic number of 84, meaning that it has 84 protons (and therefore, 84 electrons); its position in the periodic table is shown here courtesy of Wikipedia. There are 25 known isotopes of polonium; polonium-210 (with 126 neutrons) is the most common. Polonium and every element with a higher atomic number (that is, 84 and up) are radioactive; that is, they are unstable, and spontaneously decay into other elements. Ms. MacKenzie goes on to write
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.”
There are several ways for radioactive decay to occur. Polonium-210 undergoes alpha decay, emitting an alpha particle (two protons and two neutrons, essentially a helium-4 nucleus). As a result, 82 protons (and 124 neutrons) are left. This is lead-206, which is stable. Alpha particles are quite massive, so they cannot penetrate solid matter very well. Therefore, polonium-210 must be inside someone’s body to inflict much damage—so it must be ingested, inhaled, or administered through a wound, according to Roger Cox, director of the UK’s Centre for Radiation, Chemical and Environmental Hazards. Mr. Cox believes that Mr. Litvinenko would have to ingest the polonium to account for the large amount found.
According to Scotland Yard, “Traces of polonium-210 were found at the Itsu sushi restaurant in Piccadilly, the Millennium Hotel, Grosvenor Square, and at Mr. Litvinenko’s home in Muswell Hill, London.” The investigation will continue—Britain’s top-level Cabinet team has met, and the country has asked Russia to assist with the inquiry, according to CNN.