[ RadSafe ] Lethal Amount of Po-210 - any gamma?

[Kai Kaletsch]

Po-210 emits a gamma ray, but at a very low branching ratio. I did a quick 
calculation and concluded that you would not be able to see a gamma field 
above background, even a very small distance away from a lethal dose of 
Po-210, or even a few tens of lethal doses of Po-210 (it doesn't seem like 
those guys were particularly stingy with the stuff).

I would appreciate it if anyone in radsafe land could tell me if this 
conclusion is correct.

History:

I was on a plane yesterday and noticed elevated gamma readings on my 
radiation detecting watch. (5 to 20 times normal BG before take-off and 
after landing and noticeably higher than what I am used to during flight.) 
Was told afterward that there were medical isotopes in cargo. But, you have 
a lot of time to consider possible scenarios during a 4 hour flight.

BTW, it's a pretty strange experience trying to tell an airline that their 
plane is radioactive. You don't know who to talk to and you are not sure if 
they are going to stick you in a straight jacket. Especially, at a time when 
all you hear on the news is about people getting killed with radiation and 
planes getting contaminated. The first few people you talk to do not know 
that there is radioactive material in cargo.

Kai