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US unprepared for dirty-bomb attacks

April 26, 2004 By Philip Ball This article courtesy of Nature News.

Clear regulations for cleaning up radioactivity after a terrorist strike 'urgently needed'.

The United States is ill prepared to deal with the long term aftermath of a 'dirty-bomb' terrorist attack, say analysts. They warn that existing clean-up laws and regulations covering radioactive materials were not designed with dirty bombs in mind, and give conflicting recommendations.

If such an attack were to happen now, measures designed to cover industrial accidents would apply by default, say Deborah Elcock of Argonne National Laboratory in Illinois and her colleagues. They are concerned that the resulting confusion could hamper attempts to clean up the site and restore order1.

Dirty bombs use conventional explosives mixed with radioactive material to disperse radiation over a wide area. They are a crude way for terrorists to use radioactive materials. The materials do not need to be of the quality required for nuclear weapons: radioactive materials used for industrial or medical applications, which are easier to obtain, would create panic and disruption and a significant radiological health risk.

Although human injury is likely to be the immediate consequence of an attack, there are longer-term implications. An urban area contaminated with radioactivity would have to be cordoned off or evacuated until it was cleaned up.

But how clean should the area be before people can return? There are several existing US regulations dealing with radiological remediation.

For example, the 1974 Safe Drinking Water Act stipulates allowable levels of radioactivity in drinking water. The 1954 Atomic Energy Act and later amendments specify standards that must be observed by the US Department of Energy for radioactivity in soil, buildings and groundwater.

But these laws can be inconsistent. For example, facilities controlled by the energy department, the Environmental Protection Agency and the Nuclear Regulatory Commission all have different 'safe' levels. These discrepancies could lead to arguments over the criteria applicable to areas contaminated by a dirty bomb, Elcock says, which could delay clean-up efforts and undermine public confidence.

That's not the only problem. Some of the computer models used to calculate exposure levels for the present regulations are designed for rural areas. For example, they might recommend demolishing buildings and clearing the rubble from an affected site. But these measures aren't necessarily appropriate for the urban settings that would be the most likely targets of a terrorist attack. And the longer the evacuation preventing access to hospitals, homes or workplaces lasted, the more likely would it be that economic, social and health problems would arise.

The researchers want new guidelines to be drafted urgently to deal specifically with the consequences of a dirty-bomb attack, so that clean-up targets can be balanced against the problems of leaving buildings empty or demolishing them. The US Department of Homeland Security has formed a committee representing several federal agencies to develop guidelines for the clean-up response to a dirty-bomb attack and a draft package for public comment is expected to be available this summer. But they have no easy task ahead. Estimating the risks of social disruption "is not likely to be simple or uncontroversial", admits Elcock.

In Britain, a report released this week by the Royal Society has called for a new national centre to coordinate procedures for dealing with chemical and biological attacks by terrorists, including the establishment of 'safe' clean-up levels after an incident. But it makes no explicit reference to radiological hazards.


  1. Elcock, D., Klemic, G. A. & Taboas, A. L. Environmental Science and Technology, published online, doi:10.1021/es034894+ (2004).


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