I saw a YouTube video by a guy demonstrating Geiger Counter use and one of his radioactive test sources was a disk with Polonium. He casually mentioned that this was the poison used to kill that Russian defector (Alexander Litvinenko). I am referring to "antiproton" (see http://www.youtube.com/watch?v=EMGF-nnNdL8 for example).

How dangerous are isotopic sources like that? The NRC summary of the isotope says "If swallowed or inhaled, this form can be fatal in very small amounts." They go on to say "The chance of someone acquiring a lethal dose of polonium-210 is very small. Both the form and amount of radiation in exempt sources mean they would pose no health problem if ingested. It would take tens of thousands of these sources to make a fatal dose."

This would seem to imply that the source the YouTube guy had was so dilute that it is harmless, even if ingested. Is that correct?