‘Dirty’ Bombs’ Greatest Impact Likely Would Be Psychological

WASHINGTON —  Attacks with radiological or “dirty” bombs would probably not cause large numbers of immediate casualties, but they increasingly worry U.S. officials because of the ease with which they could be carried out and their ability to set off panic and inflict economic damage.

Experts say even relatively unsophisticated terrorist groups would probably be able to build radiation-dispersing car bombs with conventional explosives and low-level radioactive waste from U.S. hospitals and industry.

If such a bomb were set off in downtown Washington or New York, it would probably cause few if any immediate deaths. But as it raised the level of radioactivity, it could spark panic, overburdening the health-care system and perhaps forcing abandonment of many square blocks for decades, experts say.

“There’s no question in my mind that terrorists could, fairly readily, find some radiological material that they may wish to use,” said William C. Potter, a specialist at the Monterey Institute of International Studies in Monterey. “It is easier than I previously believed. And with the knowledge and the motivation of terrorists, that has me uneasy.”

It would be difficult for terrorists to buy or steal a small nuclear device from Russia, Pakistan or other nuclear-equipped countries, experts say.

But security is far more relaxed for radioactive materials such as cobalt, strontium and cesium that are used in medicine, in food irradiation and a host of industrial processes.

For this reason, most experts believe there is more risk of a dirty bomb attack than an attack with a “suitcase” nuclear bomb or an attack on a nuclear plant.

A terrorist could pack the irradiated material around an explosive in a car or truck, then set it off. Even if wind conditions were not optimal, the radioactivity could be dispersed widely enough to panic the public, experts say.

The Center for Strategic and International Studies in Washington conducted a study in March of the effects of an attack with a 4,000-pound dirty bomb set off in a bus parked outside the Smithsonian Air and Space Museum on Washington’s National Mall.

The study assumed that the terrorists would use cesium-137, a material that is widely used in medical treatment to treat cancer. The substance emits beta and gamma radiation that can penetrate the skin and lead to increased rates of cancer in healthy people.

The study said such a bomb would contaminate about 20% of downtown Washington, but would pose an increased rate of cancer or cataracts only in the blocks immediately around the blast site.

The report said the attack would cause many panicked residents to evacuate the area, and would quickly disable many local emergency response workers.

Containing such an attack could cost hundreds of thousands of dollars, and the number of people exposed could multiply quickly as people flee to the suburbs or outlying areas, spreading contamination, said Phil Anderson, a senior fellow at the center.

“One person who has done their homework, acting alone, can do significant damage, more psychological than real, to the United States of America,” Anderson said.

Long-term consequences of a dirty bomb attack include psychological effects on workers who might refuse to return to work and parents who might refuse to return their children to school. The local economy could stall while residents try to overcome their shock, the report says.

The strategic studies center found that participants in the simulated attack, including the police and fire departments and the Federal Emergency Management Agency, were “clearly not prepared to deal with” the presence of radioactivity found in the bomb.

Nuclear experts said the U.S. government is almost completely unprepared for an attack by a terrorist intent on unleashing a radioactive dirty bomb on the public. In states like California, there isn’t even an inventory of radioactive materials being kept by the government, and other highly radioactive products like radium and uranium are easily obtainable, said Jonathan Parfrey, executive director of Physicians for Social Responsibility’s Los Angeles office.

“In California, we don’t even know where the radioactive materials are,” said Parfrey. “We are not even on top of it. A terrorist could get some radioactive material that they could buy on the Internet, detonate it in an urban area. I’m not talking about thousands of people dying. But it would render the area uninhabitable and pose a long-term cancer risk.”

Parfrey said he’s found sites on Ebay and elsewhere on the Internet where radioactive materials can be purchased. “You simply wrap it with some TNT and detonate it, or you could just liberate the stuff into an air conditioning vent,” Parfrey said.

Thomas L. Neff, a physicist at MIT, said that the fear engendered last fall by the mailings of anthrax is indicative of what could happen in the wake of a dirty bomb.

“The impact on society can be very much out of proportion to the magnitude of the initial event,” Neff said. “You could have six months of panic, with people refusing to go to work, before the scientific evaluations catch up.”

A 1987 incident in Goiania, Brazil, illustrates the havoc that could be caused by dirty bombs. An abandoned radiotherapy machine containing cesium-137 was opened in a junkyard, exposing the blue, glowing dust. Just four people died, but more than 34,000 people had to be screened for exposure.

Times staff writers Paul Richter, Alan C. Miller and Josh Meyer contributed to this report.