[quote=@Goblininamech]
<Snipped quote by Kensai> 

Biological, not radioactive my friend.


[/quote]

If it's not a radiological bomb, it doesn't classify as a dirty bomb - dirty bombs by definition contain radioactive materials. 
Anything else, and it's a chemical or biological weapon

The difference is important, because it depends on how people's powers would work on it, and how it would be treated by the authorities for containment and cleanup etc