A U.K. inquiry into the 2006 killing of Alexander Litvinenko confirmed on Thursday what many had already suspected: the former Russian spy was likely deliberately poisoned with polonium 210. Here’s how:
Polonium 210, the most common isotope of the radioactive element polonium, is one of the most toxic substances known. It is 10,000 times more toxic than hydrogen cyanide and 5,000 times more radioactive than radium. Marie Curie won the Nobel Prize in 1911 for discovering polonium (and radium), but her daughter died after accidentally being exposed to it in a laboratory explosion. A dose of just one microgram — one millionth of a gram — can kill a human. Experts at the inquiry into Litvinenko’s death estimated his teapot was laced with at least 50 micrograms. Because it is so radioactive, polonium 210 generates a lot of heat, which would have been masked by the hot tea.
Polonium 210 ejects alpha particles, a particularly high-energy form of radiation, but one which cannot penetrate surfaces as thin as a sheet of paper. Intact skin is enough to stop the damaging particles, so polonium 210 is only toxic if it is ingested or inhaled. Once it is inside the body, however, the alpha particles wreak havoc, depositing huge amounts of energy into living tissue and causing widespread cell death. The pathologists who conducted Litvinenko’s autopsy skipped some tests for fear of contaminating themselves; one called the procedure “one of the most dangerous post-mortem examinations ever undertaken in the Western world.”
After a victim ingests polonium 210, the U.S. Centers for Disease Control and Prevention says half or more of the substance would travel to the gastrointestinal tract and be excreted. The rest would travel the bloodstream and concentrate in soft tissues — primarily the kidneys, spleen and liver — and in bone marrow. Vomiting, pain and severe internal bleeding would occur within hours, and death within weeks. Litvinenko’s wife testified that her husband fell horribly ill the same night he drank tea with two Russian men at the Millennium Hotel’s Pine Bar. He died 22 days later of multiple organ failure, including heart and bone marrow failure.
Polonium 210 is found naturally in the environment. We are continually exposed to trace amounts of it through air, water and even our food (smokers have higher concentrations in their bodies, because polonium 210 accumulates in tobacco plants.) But the isotope is only commercially available in minute quantities. To manufacture a large enough dose of polonium 210 to poison someone requires sophisticated equipment. Inquiry experts agreed that the quantity of polonium that Litvinenko ingested could only be created by bombarding bismuth, another element, with neutrons in a nuclear reactor. Though one expert disagreed, another testified that the only facilities with those capabilities are in Russia.
After Litvinenko’s death, investigators found traces of polonium 210 all over the Pine Bar. They also found traces on a passport photo of one of the Russian men Litvinenko met, in hotel rooms they rented, at restaurants they visited and aboard British Airways aircraft flying the London-Moscow route. The news caused a minor panic as thousands of Brits jammed the U.K.’s National Health Service hotline, wondering if they had been poisoned too. 787 people were offered urine tests. A fraction of them were found to have been exposed to the polonium 210, but the investigators concluded the public health risks from the Litvinenko incident were low.