How serious is threat of radiological terrorism?

Radiological terrorism (radioterrorism) is the deliberate use of radiological weapons. These weapons use radioactive materials to disperse and emit ionizing radiation. There are two classes of radiological weapons--radiological dispersal devices (RDD) and radiation emission devices (RED). These weapons would no cause massive numbers of dead. In most radiological attack scenarios, only few people may die immediately or shortly after exposure to the ionizing radiation. Nevertheless, many people could develop cancer within several years to decade after the radiological weapon attack. Such attack might spur panic and result in high economic costs because of the need for decontamination and possible tearing down and reconstruction of contaminated structures. Thus, radiological weapons may be considered rather weapons of mass disruption than weapons threating of human life.