http://www.wired.com/news/conflict/0,2100,53110,00.html How Bad Can a 'Dirty Bomb' Be?
The most likely radioactive element in a dirty bomb is cesium-137, according to Phil Anderson, a senior fellow at the Center for Strategic and International Studies. And the "consensus government view," according to a March report in The Washington Post, is that al-Qaida "has probably acquired" the isotope, which has a half-life of 30 years.
What's worse, cesium is the most "reactive" metal there is -- in nature, cesium's always found combined with another element. So the isotope becomes easily attached to roofing materials, concrete, and soil, said Fritz Steinhausler, who led the International Atomic Energy Agency's environmental assessment of the disaster at Chernobyl.
"The Russians tried to clean it up for years, and they eventually gave up. It just wasn't economically viable," said Steinhausler, who's currently a physics professor and visiting scholar at Stanford University's Center for International Security and Cooperation.
In Goiania, Brazil, four people died and more than 34,000 people had to be individually screened for contamination after a man in 1987 found an abandoned medical device filled with cesium-137 in a junkyard.
That's because cesium interacts disturbingly well with muscle tissue because of its chemical similarity to potassium, which muscles need to flex.
Fortunately, the body is used to processing these kind of chemicals, and excretes half of the cesium it absorbs within 100 days. (In contrast, radioactive strontium-90, similar to calcium, is absorbed into bone, and can take 30 years for the body to get rid of half.) But the absorbed cesium "would nevertheless cause a radiation dose, potentially increasing the risk for cancer," Steinhausler said.
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Is this is set up in a major city, it could make it uninhabitable for a long time!