Rescue workers take part in a trial in 2008 in Tokyo, Japan, to improve the city's response to a "dirty bomb" attack.

Editor’s Note: Matthew Moran is deputy director, and Christopher Hobbs is co-director of the the Centre for Science and Security Studies at King’s College London, specializing on issues related to nuclear proliferation and security. The views expressed in this commentary are solely those of the writers.

Story highlights

Radioactive sources acquired by ISIS cannot be used to create a nuclear bomb

The real threat from dirty bombs lies in their psychological and economic effects

Economic costs associated with a dirty bomb would be considerable

CNN  — 

Last week, the news emerged that ISIS terrorists have reportedly obtained radioactive materials from hospitals and research facilities captured in Iraq with a view to developing a radioactive “dirty bomb.”

Unsurprisingly, the prospect of ISIS dabbling with unconventional weapons has been greeted with considerable concern. The Iraqi government has appealed to the United Nations for international help to “stave off the threat” in this regard and Australian Foreign Minister Julie Bishop recently acknowledged that NATO countries are deeply concerned by the situation.

But what can ISIS actually do with these newly acquired radioactive materials? What is the nature of the threat?

First off, it is important to emphasize that radioactive sources of the type acquired by ISIS cannot be used to create a nuclear bomb. These sources are mostly used for medical research and treatments such as radiotherapy, and are completely unsuited to the development of nuclear weapons.

This said, the harmful effects of these sources, stemming from their chemical toxicity and radioactive properties, can be exploited in other ways. If inhaled or ingested, for example, these materials can be lethal. This was evidenced by the poisoning of Alexander Litvinenko in 2006, when just a fraction of a gram of radioactive polonium proved enough to kill the former KGB officer.

Fortunately, achieving this type of internal exposure on a large scale would prove enormously challenging for a terrorist group. Consequently, attention has focused on the use of these materials by ISIS in a dirty bomb.

Combining radioactive materials with conventional explosives, this is a bomb with an edge. A dirty bomb would spread radioactive materials, contaminating the local area and any individuals in the nearby vicinity. Crucially, however, this contamination would be mostly external in nature and, if the attack was promptly identified as being radioactive, decontamination of individuals would be a relatively straightforward process. The exposure time of anyone affected would be limited and the negative health effects mitigated.

Indeed, with a dirty bomb, members of the public are more likely to be harmed by the impact of the conventional explosives than that of the radioactive materials.

This point was borne out by a series of tests conducted over a four-year period by the Israeli Defence Forces (IDF) in the Negev Desert. As part of this project - details of which were recently published by Haaretz – some 20 devices laced with radioactive materials were detonated and their effects observed. The IDF concluded that a dirty bomb attack poses little physical danger beyond the conventional blast.

The real threat from dirty bombs lies in their psychological and economic effects – a fact that often sees these devices described as weapons of mass disruption rather than weapons of mass destruction.

From a psychological perspective, for example, nuclear weapons are associated with death and destruction on an enormous scale, and dirty bombs benefit from association with these more sophisticated weapons simply because they incorporate radioactive materials.

There is an important distinction to be made between nuclear and radiological materials but this is often lost in media reports and commentary on these issues. In any case, a dirty bomb detonated in a major urban center would be sure to cause widespread fear and panic.

The economic costs associated with a dirty bomb would also be considerable. A 2011 Congressional Research Service report, for example, suggested that the clean-up after such an attack could figure in the billions of dollars, if detonated in a high-value area such as city center or port. Little wonder, then, that the security of radiological sources has emerged as a politically salient issue in recent years.

Ultimately, while the thought of ISIS using dirty bombs to further its terrorist agenda is unsettling, the threat should not be exaggerated, particularly when it comes to its impact on public health. These are not the nuclear weapons that ISIS supposedly desires, and will do nothing to further the group’s ambitions in this regard.