By David L. Griscom
Above is the radioactive decay chain of Uranium-238. It's half life is about equal to the age of the solar system, so (1) it will be around long after homo sapiens destroy themselves but (2) it is not dangerous in its natural occurrences in minerals. However, it has a perpetual decay chain featuring several nasty radioactive daughter nuclides (owing to their very short half lives). In the diagram above, each alpha decay moves the next daughter downward by two proton numbers and each beta decay moves the next daughter one proton number upward. I've added the large blue arrows to call out the truly dangerous radionuclides in the U-238 chain -- the ones to be avoided as much as possible. Below, I present a table of the radiation doses that we all receive ...and the dose reserved only for smokers. And below that table I re-post a blog that gives more details on the dangers of Polonium-210 to smokers.