IAEA Deputy Director General Werner Burkart is a Professor of Radiation Biology and Environmental Health, who before coming to the Agency was a director of the Institute for Radiation Hygiene of the Federal Office of Radiation Protection in Germany.
Werner Burkart, Deputy Director General of the Department of Nuclear Sciences and Applications addresses issues of depleted uranium.
What is the difference between depleted uranium (DU) and natural uranium?
Uranium is a naturally occurring element and has three principal radioactive isotopes: U-238, U-235, and U-234. Uranium is present in small amounts in water, soil, rocks, food and air.
Depleted uranium is a by-product of the process of uranium enrichment (for making nuclear fuel) and is about 60% as radioactive as natural uranium. DU is almost entirely U-238 because most of the radioactive isotope U-234 and about two thirds of the U-235 are removed. In addition to its military applications (to improve the penetration of armour-piercing ammunition, for example), DU has a number of commercial applications such as neutron detectors, staining in electron microscopy, ship ballast, and counterweights for airplanes.
What are the potential health concerns from use of DU?
To be honest, there are very few health concerns for DU from a radiological point of view, because it is only very slightly radioactive. Even the handling of enriched uranium in industry does not need special protection such as shielding. There are more dangerous radiotoxic elements associated with uranium in nature such as its natural decay products radon/radon progeny and radium. Contrary to uranium proper, radon progeny as indoor pollutants contribute sizeably to our radiation exposure. DU is devoid of this radiotoxicity
The effects of DU depend on the route and magnitude of exposure (ingestion, inhalation, contact, or wounds) and the characteristics of DU (particle size and solubility). The potential health risk from chemical toxicity would arise from ingestion or inhalation of soluble depleted uranium (DU) which - at higher exposure levels - could lead to kidney damage. The potential radiological risk would arise from inhalation of insoluble DU oxides that could reside for an extended period in the lung and lung lymph nodes, or from ingestion of soluble DU that could lead to exposure of bone and other tissues. In my view, it is difficult to imagine that peacekeepers in the Balkans had exposure to DU high enough to significantly change their normal level of radiation exposure from natural and civilian sources. In this context, it has to be remembered that each cubic metre of top soil in Europe already contains about 10 g of natural uranium with all its radiotoxic decay products. Although this leads to measurable levels of uranium in drinking water and in the human body, little radiation exposure results from this radioactivity, as compared to radon progeny and external radiation from natural terrestrial and cosmic sources. For instance, some areas in Finland show largely elevated uranium levels in drinking water from wells, which lead to body contents much higher than what can be expected in Kosovo. No increase in cancer has been detected in such chronic exposure situations.
Can you tell us about your experience in studying radioactive metals like depleted uranium?
During my training in public health at the Institute of Environmental Medicine at New York University, we studied the metabolism of curium, another actinide element above plutonium and americium, in baboons. It can be said that for all these elements the uptake in the gut is quite low, even for the most soluble compounds. The critical path is, therefore, through inhalation of very fine particles. This is true for depleted uranium. This kind of exposure, to aerosolized particles, would only be present during combat and - to a lesser extent - for those crews dealing with military vehicles hit by DU ammunition.