Tiny specks

It's the tiny things that are gonna kill you. It wasn't the bright flash, or the deafening boom. It wasn't the searing heat that would have vapourised your flesh right off the bones, which would have disintegrated a second later. It wasn't the shockwave that turned houses to rubble, sent trees and cars flying.
It wasn't the burst of gamma radiation either. It's the dust that'll slowly kill you, tiny irradiated specks that'll turn your organs into liquid, but not before your skin starts looking like that of a zombie, you hair falls off. And there's nothing you can do.