South African police have arrested four men allegedly trying to sell radioactive Cesium-137 that could be used in a "dirty bomb." Cesium-137 is commonly used in medical gauges, and is very dangerous if removed from its sealed canisters. In 1987 in Goiânia, Brazil, scrap metal scavengers unwittingly exposed such a source, and it resulted in 4 deaths and 249 other cases of radiation poisoning.There's no danger of a nuclear bomb being made from it. However, it could be an ingredient in a "dirty bomb," which uses regular explosives to spread radioactive dust and soot. It wouldn't take much to create a very big problem.
