There's no such thing as relative comparison of "radioactivity". You cannot describe a radionuclide contamination by a single number. For starters, radioactive

There's no such thing as relative comparison of "radioactivity". You cannot describe a radionuclide contamination by a single number. For starters, radioactive emissions come in three forms (alpha, beta, gamma), all with different properties. Different nuclides accumulate differently in living tissues too. There can be almost no elevated gamma background, but nevertheless harmful to live there (e.g. Chernobyl).