Quote Originally Posted by Seraph View Post
Externally, Po210 is very low risk. Alpha particles can't even go through a piece of paper. Not even through skin. Internally, very serious problem.
You're right, seraph -- Po-210 has to be inhaled or ingested in order to be dangerous. So in the case of hospital workers caring for Litvinenko and changing his bedsheets, etc., the main danger to them would NOT be from getting a little bit of his radioactive sweat or urine on their skin.

Rather, the risk would be that as the sweat/urine/feces dry out on Litvinenko's clothing and bedsheets, particles of polonium dust could become airborne and then be inhaled by a hospital worker. Although the risk from a one-time inhalation might be negligible because the Po210 dose was so tiny, if the same worker were visiting Litvinenko's bedside several times a day over a period of two or three weeks, then the total amount of inhaled Po210 could, in theory, become high enough to put the worker at statistically greater risk of lung cancer or leukemia. (Which could translate into expensive legal liability for the hospital.)

But as far as I know*, inhaling tiny amounts of airborne thallium dust from the dried bodily fluids of a thallium-poisoned patient wouldn't put hospital workers at significant risk. In other words, the "secondhand exposure" danger isn't as serious with thallium as it is with polonium.

Hence, my argument (mainly to Marcus) that it would have been utterly irrational for British agents to poison Litvinenko with Tl but then make up a total lie for the public that he'd been poisoned with Po210.

* Based on a lot of Googling -- I'm not a medical expert!