Following the poisoning of former Russian spy Alexander Litvinenko, British authorities are following a trail of radioactive contamination. Litvinenko died from the effects of absorbing a rare radioactive element, Polonium 210.
Polonium is a naturally occurring element. There are trace quantities in the soil, minuscule amounts in seafood and in consumer products, such as anti-static brushes found in photo shops.
Although it is described as one of the "nastier radioactive isotopes," Polonium is harmless unless it gets inside your body, through ingestion or a puncture wound, for example.
Robert Siegel talks with John Emsley, author of The Elements of Murder: A History of Poison, about the poisoning of Russian-spy-turned-Kremlin-critic Alexander Litvinenko. Litvinenko died last Thursday after being poisoned with radioactive Polonium-210.
Emsley is a former science writer-in-residence for the University of Cambridge.