What is a dirty bomb and what can happen?
A dirty bomb is a regular bomb (plastic explosive, for instance) combined with radioactive material. When it is exploded, the radioactive material is spread around, creating a radioactive area that needs to be cleaned. A dirty bomb is neither a nuclear weapon nor a nuclear bomb. Injuries or deaths are far more likely to result from the explosion than from exposure from the radioactive material. Radioactive material from a dirty bomb would likely be deposited within a few blocks or less from the site of the explosion, but could cause widespread public fear and panic—which is what terrorists are trying to accomplish.
The harm caused by a dirty bomb would be determined by the type and amount of radioactive material involved, the type and amount of explosive, weather conditions, how the individual was exposed to the radiation (external, internal, or both), and how long the individual was exposed to radiation before it was discovered.