Why is polonium-210 dangerous?
The alpha particles emitted by polonium-210 can be stopped by a sheet of paper or the dead layers of the skin. For the polonium to be harmful a person would have to eat it, drink it, breathe it in or absorb it through a cut. If eaten, dependent on the chemical form of the polonium, 10-50% could be taken up by the gut. This means that 50-90% would be excreted in the faeces within a few days. After uptake to blood, polonium-210 is widely distributed though soft body tissues including bone marrow and is eventually excreted, mostly in the urine with a half time (the time taken for the level of polonium-210 to fall by half) of about 50 days.
