There has been a lot of attention lately on the North Korean nuclear weapons test. First aiders might find useful a brushup concerning a more 'down to earth' atomic hazard: the risk posed by a "dirty bomb".
The riskA "dirty bomb" (sometimes called a 'radiological dispersal device') combines conventional explosives with radioactive material (for example, certain types of medical and industrial waste). This combination is unnerving but should not be exaggerated: a dirty bomb is not a nuclear device. A nuclear weapon, like that tested by North Korea, splits atoms to cause a catastrophic explosion and widespread radioactive contamination. A dirty bomb is simply a conventional device with contaminants added.
Identification.An explosion is proverbially hard to miss, but radioactive material is unlikely to be obvious unless (for example) the debris contain material with a hazardous goods label.
Image from here
Ideally emergency responders will be equipped to detect radiation in the area of an explosion and will be able to relay suitable warnings. It is probably not worthwhile obtaining one’s own Geiger counter or similar advice: the United States' Nuclear Regulatory Commission warns that “many of the Geiger counters available commercially are uncalibrated and worthless”.
The Centres for Disease Control advise that radiation injuries may be indicated by the skin becoming red and swollen and the casualty complaining of nausea, vomiting and diarrhoea. However, they caution that the low radiation levels expected from a dirty bomb situation are unlikely to cause symptoms.