SCIENCE

Six Secrets of Polonium

This rare and dangerous element, discovered by Marie Curie, is found in cigarettes and was used to poison an ex-KGB agent

Sarah Zielinski

October 3, 2011

One hundred years ago, Marie Curie won her second Nobel Prize, in chemistry, for her 1898 discovery of the elements polonium and radium, which she had painstakingly isolated from a radioactive uranium ore called pitchblende. She named polonium in honor of her homeland Poland (which officially did not exist at the time, as it had been occupied by neighboring countries). Polonium occurs in very low concentrations on the Earth’s surface. It is highly unstable, and all isotopes are radioactive. Here are some of the more interesting things we know about the element.

1. In 2006, Russian ex-KGB agent Alexander Litvinenko, who was living in the United Kingdom after claiming political asylum, died after being poisoned with polonium-210. A British investigation identified Andrei Lugovoy, a former officer in the Russian Federal Protective Service, as the main suspect in the case, but Russia refused to extradite him. Lugovoy is now a member of the Russian lower house of parliament, the Duma.

2. Before 1944, very little polonium had been isolated. The Manhattan Project, however, changed that. Polonium, an emitter of alpha particles, and beryllium, which absorbs alpha particles and emits neutrons, were used in the trigger of the first atomic bombs. The two elements were kept apart until the very last moment; once mixed, they set off the explosion.

3. Polonium-210 can be found in the air. It is created during the decay of radon-222 gas and during the production of phosphorus from phosphate rock. Plants can take up polonium through their roots, or it can be deposited directly on broad-leafed plants. Lichens also absorb polonium directly from the atmosphere. In northern regions, humans can have higher concentrations of polonium because they eat reindeer, which eat lichens.

4. Cigarettes and other tobacco-containing products also have low levels of radioactive polonium. Researchers from the University of California at Los Angeles recently found that tobacco companies knew about the radioactivity as early as 1959. The scientists calculated that this radioactivity, which can cause cancer, is responsible for up to 138 deaths for every 1,000 smokers over a period of 25 years.

5. Because the alpha particles from polonium don’t pass through the epidermis, the substance is not harmful outside the body. If polonium is ingested, 50 percent to 90 percent of the element leaves the body through feces. The rest is deposited mostly in the kidneys, liver and spleen; because it is radioactive, the amount of the element decreases by half every 50 days. The effects of inhaled polonium are localized in the lungs. Smokers have about twice as much polonium in their ribs as non-smokers.

6. The first person to die of polonium poisoning may have been Marie Curie’s daughter Irène Joliot-Curie. In 1946, a capsule of polonium exploded on Joliot-Curie’s lab bench. It is thought that this incident may have been responsible for her death, 10 years later, of leukemia.