Scrubbing 'dirty bombs': explosive hype.

SINCE 9/11, politicians and pundits have repeatedly warned that terrorists who can't get their mitts on a fully functioning nuclear device could still spread radioactive death with a "dirty bomb," a conventional explosive combined with radioactive material. Such a weapon, they claim, would scatter the material far and wide, rendering a large area unlivable and turning rescue efforts into suicide missions.

The results of tests involving controlled dirty bomb explosions, reported at a February meeting of the American Association for the Advancement of Science, cast doubt on this scary scenario. Physicist Fred Harper of Sandia National Laboratory in Albuquerque, who led the experiments, said even first responders on the scene of a dirty bomb attack probably would not need full radiation suits. The tests indicated that most of the radio active material would attach to large fragments of debris and end up on the ground, not in the air, making for an easier cleanup. And the very smallest particles, which could cause radiation damage if inhaled, tend to float above most people's breathing space.

Steven Musolino of Brookhaven National Laboratory, who worked on the dirty bomb experiments with Harper, summed it up this way: "Pretty much everything bad happens within 500 meters, and to a large extent [the bad effects] don't happen." That conclusion jibes with the Nuclear Regulatory Commission's fact sheet on dirty bombs, which says the long-term health risk of limited exposure to radioactive particles is probably "extremely small." The commission categorizes the dirty bomb not as a weapon of mass destruction, but as a weapon of mass disruption.