Doug said:

>It's when you find that XXX is about 4 metric tons, and ZZZ is
>your 0.001% chance of contracting something increasing
>0.0015% that you wonder how, why and where the money for
>such pointless research originates.

The technology for measuring trace amounts of material has become so sensitive that it's beyond belief. I was alive when they were still doing atmospheric nuclear weapons tests (IMHO, one of the stupidest activities of all time). I'm sure anyone my age or older has a few plutonium atoms floating around in their body as a consequence of those tests. I'm not certain but I believe the plutonium I'm carrying is detectable using modern instruments. Does that mean I'm doomed to die from bone or lung cancer? No, like everyone else who is in good health, I have an immune system that combats new cancer cells. The trace amounts of plutonium are just part of the background noise of oxidants, reactive chemicals and radioactive materials that are part of everyday modern life. As bad as this is, our ancestors had it worse eating charred meat or partially rotten food (mold is extremely carcinogenic). The problem with these medical scare tactics is they treat toxic levels as an absolute quantity when they're only meaningful in a relative context. Probably the greatest source of insult to my body is the pollen from trees causing allergic reactions (I'm so glad Claritin is now a generic drug). Of course, the government is not going to declare my neighborhood a Superfund site because of too much tree pollen.

Gary

p.s. "Natural" or background plutonium-238 concentration is 0.00072 picoCuries per gram.