ABCNews.com:

Congressional investigators, in an undercover sting on the federal agency charged with protecting the U.S. from a radioactive attack, found out how easy it might be for terrorists to get their hands on the materials for a dirty bomb. Their radioactive material of choice? Americium-241, which is commonly used in certain kinds of construction equipment, called moisture-density gauges, and is “incredibly toxic,” according to Daniel Hirsch, the president of the Committee to Bridge the Gap, a nuclear watchdog group. “Americium is a material very similar to plutonium,” Hirsch told ABC News. “In fact, it’s about 50 times more toxic than plutonium gram for gram.”