Wikipedia has a copy of the Groves Memo online at

http://en.wikipedia.org/wiki/File:Groves_memo_30oct43_p1.GIF

Nowhere in this document, which is sometimes claimed to demonstrate that the army has known of the toxicity of DU for decades, is there mention of any specific radioisotope, including uranium.  In fact reading the entire memo shows that it’s referring to isotopes which are many orders of magnitude more radioactive than U238.   One possible candidate for the type of radiological weapon they’re talking about would be cobalt 60, which is nearly a billion times more radioactive (in the sense of decays per second) than U238.  In other words, this is not a smoking gun for DU toxicity.

With that said, it’s clear that in 1994 the army was and presumably still is very concerned about the health effects of inhaled DU.

http://www.fas.org/man/dod-101/sys/land/docs/du.html