In the Wool series; specifically, Wool 6: First Shift,
it is said that the world ends with atomic bombs.
The landscape of the world definitely jives with this.
However, whenever someone goes out into the world,
their protective suit is immediately attacked by something in the air and slowly disintegrates. First Shift makes mention of nano-technology or poison, but I don't recall if that was ever confirmed or not.
Does the series reveal what is the villain in the air?