Features: Depleted Uranium

The IAEA Focuses on Radiological Safety

Under its Statute, the IAEA has the specific mandate to establish, in consultation and collaboration with other United Nations and specialized agencies concerned, standards for the protection against ionizing radiation and for the safety of radiation sources and to provide for the application of these standards. With respect to potential radiation hazards, the Agency has jointly developed the International Basic Safety Standards with the World Health Organization, the International Labour Organization, and the Food and Agriculture organization. These standards, known as the BSS, cover a wide range of situations that give rise or could give rise to exposure to radiation such as the radiation hazard posed by depleted uranium.

The BSS sets limits for exposure to any combination of uranium isotopes, including those found in depleted uranium based on recommendations of the International Commission on Radiological Protection and the estimates of health effects of radiation from the United Nations Scientific Committee on the Effects of Radiation,. The established limits vary according to whether the scenario involves occupational exposures or exposures to the general public, but applies to any use of or practice involving ionizing radiation. For example, the BSS sets the annual dose exposure limits for members of the public and workers at 1 mSv and 20 mSv respectively, for any practice using ionizing radiation.

In the case of DU, determining whether or not these limits were exceeded would depend upon studying a representative group of individuals and calculating their possible doses from both internal irradiation, through ingestion and inhalation of DU particles and external irradiation.

The IAEA has assessed other cases of environmental radiation contamination to determine whether or not they comply with the limits of the BSS, for example in Fench Polynesia, Marshall Islands, Kazakhstan, and Kara Sea in collaboration with other UN organizations. In order to undertake such an assessment, a formal request must be first made to the Agency, the radiological situation of concern must be well defined (usually through a prior fact finding mission), and financial arrangements must be agreed upon.

If these conditions are met, the IAEA has the expertise to set up and co-ordinate an international study in order to evaluate the radiological situation. This study is generally conducted in four stages:

determining the source term through an environmental monitoring programme
modelling potential transfer pathways from the environment to humans
assessing the radiation doses to representative groups of individuals
checking for compliance of doses against the International Basic Safety Standards

Should such a study demonstrate that non-compliance with the BSS, the IAEA would recommend possible remedial measures. Should such non-compliance be so extreme as to possibly cause health effects, the World Health Organization would be responsible to deal with these health effects.

With respect to the need to clean up areas where DU weapons were used, the BSS dose not include specific criteria to assist in deciding what measures should be taken. However, the International Commission on Radiological Protection (ICRP) has established dose criteria (ICRP Publication 82, Pergamon Press 1999), which, in principle, could be applied to such decisions.

Many radiological protection decisions are based on comparisons with an annual dose limit for members of the public of 1 mSv. However, the ICRP has provided guidance using a scale of dose levels to help practical decision-making in a variety of situations.

Any intervention to clean up will need to be justified on a case-by-case basis. Pre-selected individual dose guidelines can only provide an input to decisions, and no single factor should be overriding. With these provisos, the ICRP has recommended a differentiated approach to intervention on the basis of individual effective dose. In cases where an individual effective dose of 100 mSv is exceeded, intervention should be "…almost always justifiable", while if the individual dose is above 10 mSv, intervention "…may be necessary". In contrast, for doses below 1 mSv intervention is "…unlikely to be justifiable".

Thus, to decide whether remedial measures (including a cleanup operation) would be justified, it is necessary to carry out an assessment of the dose received by individuals from exposure to depleted uranium to be compared with the ICRP guidelines.

Indicative potential doses to the population living in areas affected by DU for a range of different exposure situations are shown in the table below. The doses presented are theoretical doses, based on conservative assumptions.

Pathway	Estimated effective dose	Remarks	Intervention justified?
Handling of DU projectiles	a few tens of mSv	Based on a contact dose rate of 2 to 2.5 mSv per hour to the skin^1/, assuming that a person is in contact with the object for 10% of the time. Comparable to dose received by a person in tanks fully laden with DU munitions	Intervention may be necessary
Inhalation of DU aerosol	a few mSv	Likely doses to people inhaling dust when entering military vehicles hit by DU ammunitions	Doses are in a range where intervention should be considered
Exposure to DU in the environment	less than 1 mSv	Doses include those from inhalation and ingestion of dispersed DU aerosol. Probably in the region of a few µSv for most people, even in the vicinity of battlefields^2/	Doses are below the public dose limit of 1mSv and probably close to the IAEA "exemption" levels

^1/ See S Fetter and F N von Hippel, Science and Global Security, 8:2 125-161, 1999. The UNEP report "Depleted Uranium in Kosovo, Post-Conflict Environmental Analysis" gives similar estimates.

^2/ Using maximising assumptions S Fetter and F N von Hippel have calculated doses of 30 µSv in a year (S Fetter and F N von Hippel, ibid.). Maximum doses of between 30 to 100 µSv in a year, depending on the age group considered, were calculated by A. Nusser et al. in a document prepared for the Article 31 Working Group on Depleted Uranium of the European Commission (Nusser A., Kugeler E. and Thierfeldt S. Estimation of Effective Doses due to Depleted Uranium, Brenk Systemplanung, Aachen, 2001). Comparable doses were estimated in the UNEP report "Depleted Uranium in Kosovo, Post-Conflict Environmental Analysis".

The dose assessment indicate that remedial measures may be necessary only to remove DU ammunitions still lying on the ground which could be collected by people and, possibly armoured vehicles hit by DU projectiles. The extent of this operation would depend on several factors, such as the number and location of affected areas, the number of DU ammunitions and targets still present. Precautionary measures could include a public information campaign aimed at informing the local population (including military personnel) on the possible risks of DU ammunitions and discouraging them from collecting DU ammunitions found on battle grounds. It is unlikely that an extensive cleanup of the affected areas, where DU weapons have been used, such as removal of soil or filtration of drinking water, will be justified on radiological protection grounds.