Why Is Polonium Used in Assassinations?

Your polonium questions, answered.

Palestinian leader Yasser Arafat speaks during his meeting with European Union.
Was Yasser Arafat poisoned?

Photo by Hussein Hussein/PPO/Getty Images.

The body of Yasser Arafat was exhumed briefly on Tuesday so medical examiners could attempt to determine whether he was poisoned. Arafat’s widow, Suha, requested a murder investigation, and high levels of polonium-210 have been found on the Palestinian leader’s personal effects. Explainer readers have asked a series of polonium questions, which are answered below.

Why do political assassins like polonium-210? Because a small amount is very deadly. Polonium-210 is extremely toxic, and it’s relatively easy to smuggle across borders because it emits only short-range radiation. But it’s not a good choice for an assassin who wants to get away with his crime. Unlike many other potential poisons, polonium-210 is easily identifiable and can leave a radioactive trail to the culprit. It makes sense as an agent of murder only if you’re trying to make a statement. The chemical is, in a sense, a calling card, because only a handful of major countries, including Israel, the United States, and Russia, are known to maintain large stockpiles of polonium-210, and private entities can buy only small amounts under a government license.

The popularity of polonium-210 as an agent of murder may be overstated because of a single, dramatic case. In 2006, Alexander Litvinenko died slowly from polonium-210 poisoning in London. Before dying, the former KGB agent accused Vladimir Putin of ordering the attack. Litvinenko remains the only high-profile known case of deliberate polonium poisoning.

Where does polonium-210 come from? Bismuth. When showered with neutrons, the element bismuth absorbs one of them to become radioactive bismuth-210. Over the course of five days, the bismuth atom undergoes beta decay: The neutron turns into a proton, an electron, and an antineutrino, with the latter two particles eventually leaving the nucleus. The result is polonium-210. The world’s supply of polonium-210 is produced in a nuclear reactor in the central Russian city of Chelyabinsk.

Polonium-210 is also naturally present in the environment in small amounts, because it is a decay product of uranium.

How does polonium-210 kill? Through irradiation. Polonium-210 is a prolific emitter of high-energy alpha particles, and is 5,000 times more radioactive than radium. Alpha radiation loses much of its energy on first impact, so being exposed to external sources isn’t normally fatal. If, however, the substance enters the body, it damages bone marrow, causing nosebleeds, bruising, and hair loss. High doses travel through the body, irradiating tissue and sometimes killing the victim. Pictures of Alexander Litvinenko, who was allegedly fed dissolved polonium-210 in his green tea, dramatically demonstrate the external symptoms of polonium poisoning, including hair loss and yellowing of the skin.

If he really was poisoned, would polonium-210 still be detectable in Arafat’s body after eight years in a mausoleum? Possibly. The radioactivity of a sample of polonium-210 drops by one-half every 138 days, so examiners will be looking for approximately two-one-millionths of the original dose of radiation. Still, if Arafat was exposed to a lethal dose, it’s possible that tests will be able to detect the leftovers. It will likely be months before authorities get the results.

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