What do Nobel Prize winner Marie Curie and poisoned Russian spy Alexsander Litvinenko have in common?

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.