The 420 appears to be CDE not CEDE!
My apology, and thanks to the great seer of HP. I accidentally mistyped (very bad move, I know) the extra E this AM. Can't believe I did that. But, I was thinking that the dose to the lung would be from the Pu and not the AM. My understanding is that Am gets taken up by bone more than Pu, and the biological half life is quite short compared to Pu, so that the CDE of 420 Rem must be from the Pu. Since this is a significant increase in dose over the "threshold" for estimating the risk of cancer increasing from Pu I felt that there would be an elevated chance of occurence.
Again, my bad and a most sincere apology for switching up the CDE and CEDE acronyms.