[brooklin]

You really shouldn't worry about a "dirty" bomb. The worst part of the whole event is the ordinary explosion. There won't be enough radioactivity to hurt you. It's the panic that is caused when you mention radioactive materials.
Now if they exploded atomic weapons... that's another story.

[My Favorite Headache]

Agreed 100%. Although the movie sucked big time, I can never get that image out of my head of when the bomb went off in Sum Of All Fears.