[stefantalpalaru]

>months or years after the event, it's not generally going to be a big deal

Strontium-90 [1] has a half-life of 28.79 years and gets concentrated in bones causing bone cancers and leukemia.

Caesium-137 [2] has a half-life of 30.17 years and concentrates in soft tissues.

[1]: https://en.wikipedia.org/wiki/Strontium-90

[2]: http://large.stanford.edu/courses/2012/ph241/wessells1/