A dirty bomb, or a radiological weapon, is one in which nuclear material is combined with traditional explosives into a bomb.  The detonation is a conventional one- it’s not a nuclear explosion which releases a huge amount of energy by splitting the atom- but it is still an explosion that can disperse radioactive material. As the explosion is not as large as with a nuclear bomb, any radioactive material is unlikely to reach the upper atmosphere to become fallout.  A dirty bomb is not a nuclear weapon or a nuclear explosive device. The effects of a dirty bomb in terms of the anxiety and fear it causes can be tremendous. This is why a dirty bomb is also dubbed a weapon of mass disruption.

What are some impacts?

Researchers have looked at various impacts of chemical or biological weapons use by terrorist groups to assess what might happen if a radiological weapon were detonated. For example, the 1995 Sarin attack by the Aum Shinrikyo cult showed widespread panic and fear.

Another example is the incident in 1987 in Goiania in Brazil, where a Cesium-137 source was found and opened by scrap-metal scavengers in an abandoned radiotherapy institute.  The material was used in paint, and the dust spread over the area, contaminating more than 400 persons over the next two weeks. Four of those died from the exposure. To mitigate further damage, more than 100,000 people needed to be tested, and there was long-lasting social stigma to the area in which the incident occured. 

Another comparison was to look at the disaster of Chernobyl. Although the situation is very different from a dirty bomb scenario, it did show how radioactive materials, and specifically cesium, attaches itself to an urban environment and what those consequences are for the surrounding population. 

What is the response capacity?

Most emergency services have protocols in place for “CRBN” (Chemical, Radiological, Biological and Nuclear) emergencies, and to deal with the situation a number of phases are identified: the period before an attack, shortly after and some time after the attack. 

Before an attack the radiological source can already emit radiation but it is most likely that this will only affect the terrorist themselves or close bystanders. In the phase immediately after the attack it is necessary to attend to wounded persons and stabilize them first before starting decontamination, while rescue-workers at the same time need to take measures for personal protection. 

Because debris can work as a hotspot for radiological material the cleaning process needs to be started as soon as possible. Any cloud created by the explosion has the ability to carry radioactive particles and spread the material which will attach itself to buildings, grass and streets. It is necessary to start monitoring the cloud to determine which areas are contaminated and need to be cleaned.

Is there any international regulation on a dirty bomb?

There is a global effort to secure nuclear materials to prevent their use in any sort of improvised radiological weapon. There are international agreements, like the Convention on the Physical Protection of Nuclear Materials, the International Convention for the Suppression of Acts of Nuclear Terrorism, and a series of UN Security Council resolutions (including 1373 and 1540). There are also informal mechanisms, like the Global Partnership Against the Spread of Weapons and Materials of Mass Destruction and the outcomes from the Nuclear Security Summit Processes which were non-binding commitments to convert highly enriched uranium facilities to low enriched uranium, and to put excess materials under global control.

A dirty bomb is NOT a nuclear weapon and it is NOT a nuclear explosive device.  Therefore, it is not covered under either the NPT or the TPNW. 

What can I do?

Consistent and unequivocal condemnation from governments and civil society can stigmatise and delegitimize threats, help restore and strengthen the norm against the use of radiological weapons or dirty bombs, and reinforce nuclear security, disarmament and non-proliferation efforts. The use or threat of use of any chemical, biological, radiological or nuclear weapon is illegitimate and should be condemned.