Focus: 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.