Sitting here smoking my cancer sticks and working on trying to figure out the polonium drama (if you don't know what I mean, go to www.atlargely.com ) and I realized the following... going to post from my blog:

"My theory on the mechanism:

I have said before that I believe that the Polonium was not directly ingested by Alex, but was rather in something belonging to him or something that he used was laced with the polonium. But remember, you want to use one weapon against several people, and you don't want to use too much as it may be identified. What kind of delivery mechanism could both be undetected, potent, transmittable, and have the ability to cause so much confusion in terms of the evidence trail?

If Mario is not involved, but contaminated, what did he share with Alex and when? The same question applies to Alex's wife. What was it, a cup? No, because Mario did not go home to visit Alex's family.

How about this:

A cigarette. In fact, a cigarette would be an extremely powerful way to distribute the polonium via air, causing another to inhale it. But since the only people that would inhale for any real duration would be people in close proximity to the victim, it is certain to do the trick as smoking at most places is not allowed and also because in small vapor qualities it would not be necessarily lethal, so not too much of a danger to the British public, although somewhat of a danger if things went badly.

Let us then assume the polonium was brought into England by several agents, all bringing in cigarettes cartons. That would explain why an overhead was contaminated as well as a seat on a particular flight.

Imagine Alex going about his day, smoking. Meeting Mario for lunch, who only inhaled some of the poison. This would also account for some of the radiation sites that do not have a bodily fluid deposit, like urine for example. Most importantly, It would also account for the delayed reaction in Mario and also Alex's wife, because if they are non-smokers, they would not have directly ingested the Polonium, rather, they would have inhaled it. Alex, however, would have directly ingested it, both via his mouth and via inhalation, speeding up his death. The more he smoked, the worse it got, which might account for why there are places that are more contaminated than others and also out of order of his movements."
http://www.atlargely.com/2006/12/alex_smok...

Now I have to see if this pans out via atomic experts, but this would be one hell of a dangerous weapon.