Ask big city mayors to list the terrorist threats they worry about most, and they’ll probably put a “dirty bomb” attack near or at the top of the list. Of the unconventional weapons that a terrorist could use to attack the United States, a dirty bomb is arguably the most probable. The components for building a dirty bomb are (comparatively speaking) more numerous and technologically less complex to work with than those needed to construct and deliver a viable nuclear, chemical, or biological weapon.
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