Hmmm, I am not so sure how much paranoia will you "prevent" waving a GM counter around in a supermarket :D . I am really at a loss how real GM enthusiasts (who of all people should know better) keep on expecting to see food contamination. Labs equipped with HPGe spectrometers for food testing do exist, you know, and their MDA is many orders of magnitude below that achievable with a GM counter; then this is the only practical way to tell what contamination you have and what may have caused it.
That is not to say I have anything against people playing with GM counters of course, on the contrary, we all need to make stuff to play with and enjoy, obviously I am no different myself.
Dimiter
------------------------------------------------------ Dimiter Popoff, TGI
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