This is really scary stuff (and I was hoping that it would never make it on HN). I heard from an aeronautical engineer once that if one drop of mercury somehow gets let loose in an airplane that the whole plane needs to be basically taken apart (and possibly scrapped).

Mercury by itself is very toxic. There was a custodian who broke a thermometer in our office building once. That would have been ok - had she not spread it everwhere by playing with it. And, speaking from experience, as someone who broke a thermometer as a kid in his room and was mesmerized by the liquid, I can't blame them. Whole building had to be detox'd - almost spaceman suit E.T. style.