Final answer:
Casualties from a dirty bomb detonation would predominantly result from the explosion's blast. Radiation could cause long-term health issues and environmental contamination.
Step-by-step explanation:
If a "dirty bomb" were detonated in a U.S. city, most of the casualties would be caused by the initial blast from the conventional explosives used in the bomb. A dirty bomb combines conventional explosives with radioactive material, with the intent to disperse radiation and contaminate the area. However, it is important to note that the radiation spread by such a device would likely cause fewer immediate casualties compared to the blast but could lead to long-term health issues for those exposed and significant environmental impact.
The incendiary effects of traditional explosive devices have historically resulted in immediate and wide-scale damage, as seen in bombings during World War II or the Oklahoma City Bombing. In contrast, radiation can lead to illness and death over a longer period. After the initial explosion, the primary concern becomes the radioactive contamination of the area, which could expose the population to harmful radiation levels and necessitate costly and prolonged decontamination efforts.