Bananas!

There's a nice article on the BBC News website talking about the Banana Equivalent Dose as a measure of radiation. It's a kind of nice idea, since it's motivated by the desire to point out that everyday objects are radioactive. Bananas are more radioactive than most things since they are high in potassium, which has a radioactive primordial isotope, Potassium-40 (K-40). K-40 is also responsible for the last item in the table in the BBC article - sleeping with someone is equivalent to half a banana's worth of radiation dose, because your bed partner is partly made of potassium, as are you. Around 5000 radioactive potassium decays occur every second in a typical adult.