A "dirty bomb" is also called a radiological weapon or a radiological dispersal weapon. It contains some fissile (nuclear) materials and a conventional explosive. When the bomb explodes, this spreads the nuclear materials. This causes damage and can inflict casualties, but at levels far below a "real" nuclear weapon. Even if there are few immediate casualties, there may be long-term health and environmental damage. An in-depth discussion of these weapons and their impacts can be found in the Senate testimony of Dr. Henry Kelly, President of the Federation of American Scientists.