The vast majority of the activated radioactive material that is made in the aftermath of a nuclear blast have incredibly short half lives. GOOD NEWS: it goes away quickly. BAD NEWS: while it's still around it is BAD, BAD, SCORCH YOUR SKIN OFF BAD.

This is why you shelter from fallout: to hide from the immediate bad stuff in the first few days. Then you have to figure out what to do about the intermediate half life stuff that will make life unpleasant, but not prompt kill you dead, for the next several months like the radioiodines that will obliterate your thyroid.

After that, you start making your peace with the stuff which will remain for decades or centuries. Radioactive? Yes. Adds to your body burden of dose? Yes. Should I make an effort to avoid these if I can? Yes. Are they going to kill me dead if I don't? No, but may increase your cancer risk over the decades.

The sad fact of the matter is that 1/3 of people are going to die of cancer, and there's a hell of a lot of ways to raise that risk. The risk perception, however, is something else. if you have a 33.3% chance of drying of cancer and you raise it to 33.30001% with a higher background ionizing radiation dose, that is worse but damn near statistical noise.

Maki Naro