A dirty bomb consists of conventional explosives combined with radioactive materials. This sort of weapon is incapable of creating a nuclear chain reaction; however, the explosion itself is not the primary means of causing damage. The explosives are the delivery mechanism for spreading lethal amounts of radioactive materials to a wide area.

Unlike conventional nuclear bombs, the type of radioactive materials that can be used in dirty bombs does not have to be weapons grade to have the desired effect. Spent fuel rods from nuclear power plants and even nuclear materials that can be obtained legally for medical applications can be used to create a functional dirty bomb. It is this comparative ease in attaining materials that makes a dirty bomb very desirable to terrorist organizations around the world.

The effects of a dirty bomb detonation are unclear. Many factors affect the scope of devastation created by such a bomb. First, the amount of contamination is dependent on the quality and quantity of the nuclear materials. The amount of traditional explosives also determines how widespread the contamination will be. Other variables such as wind make the effects of a dirty bomb nearly impossible to predict. Because of this uncertainty, there is wide dissention amongst experts on how much of a threat a dirty bomb would pose to a populated area. Experts from the Vienna-based International Atomic Energy Agency(IAEA), contend that a dirty bomb could render an entire city uninhabitable until a thorough decontamination is completed. Some other experts believe that a dirty bomb would not cause much of an increase in the death toll caused by a conventional terrorist bomb attack. In fact, Abel Gonzalez, the IAEA's director of radiation and waste safety contends that the TNT used might be more deadly than the nuclear materials themselves.

Even if the weapon does not create a higher death toll than normal explosives, a dirty bomb is much more powerful as a terror weapon than a solely explosive bomb. "contamination in even small quantities could have major psychological and economic effects," Gonzalez warns.

Unfortunately, the only way we will be able to know the real effects of a dirty bomb is if it is actually used in an attack.

The prospect of a dirty bomb attack is not as farfetched as once believed. Osama bin Laden’s al-Qaeda network has claimed that it has nuclear weapons. A dirty bomb is the most likely form such weapons would exist in.