Steve Pope wrote:
>
> What about the post-nuclear-age manmade environmental radiation?
> I'm pretty sure that's stronger than cosmic rays, even at
> 30,000 feet.

I have some Fiesta salt and pepper shakers and a plate
which measure 10 times background radiation at a distance
of 3 feet. They are definitely pre-nuclear age.
(No, I don't use them for food purposes.)