[ajarmst]

I'm not advocating DU as a part of a healthy diet. It's more than 100 times as radioactive as bananas, after all. I am saying that the primary danger from DU is not its radioactivity, but the fact that it's a heavy metal. That still true (possibly even more true) in an area with excessive DU contamination.

The fissibility of Uranium isotopes is critically important in weapon design and storage. With regard to biological danger, it's the radioactivity that is important (unless you happen to be near a prompt critical event, of course). DU is about half as radioactive as natural Uranium, so I think my "significantly" was justified.

Body burden and biological half-life are better indicators of a given radioactive substance's danger to living creatures, especially in the case of alpha emitters. That's why proactive measures like prophylactic iodine and showers are effective in contaminated areas. Of course accumulating more doses of an agent is always going to be more dangerous---what's important in comparisons is how dangerous one dose is.

Your Th-234 argument is misleading, and you know it. Yes it's nasty, but U-238 decays to Th-234 with a half-life of 4 billion years. That event would occur in a human body so rarely as to be completely immeasurable unless the human was contaminated with so much U-238 they'd die instantly from the toxic exposure and whatever horrific event deposited that much.

We ingest alpha-emitters with every meal, and while we should avoid ingesting more than we have to, at the small rates we do even in the presence of U-238 (or a diet rich in Bananas and Brazil Nuts, for that matter), there's no statistical impact on lifespan.