glhcarl
I believe you are correct about the relative safety of depleted uranium. As long as it remains in one big solid chunk. However, if it becomes vaporised, or broken into fine particles, and can be breathed in, then it is a very different matter entirely.
I rather doubt that the temperatures or mechanical forces available in an aircraft crash are sufficient to achieve this. (Anyone know different?) But when DU is fired as armour piercing ammunition this does happen, and this is a recognised hazard on recent battlefields.