7. What is known about uranium exposures?
7.1 Natural exposure is a relevant comparison
Risks from exposure to DU after military use have been the main focus of concern regarding use of the material. In particular there have been suggestions that it might be linked to Gulf War Syndrome, whose reported symptoms include immune system defects, chronic pain, fatigue and memory loss by ex-combatants, and to an alleged high level of birth defects affecting ex-combatants’ children.
Any exposure to DU can be compared with exposure to naturally occurring uranium. Uranium is one of the 20 most abundant elements on earth and is present in a variety of minerals. It is naturally present in soil, in concentrations ranging from 0.05 to 10 mg/kg, and surface and ground water, in concentrations from 0.01 μg/L to more then 1,500 μg/L.
The widespread presence of uranium also means it is normally found in food and drinking water. The average daily intake of natural uranium in humans is estimated as 1 to 2 μg from food and 1.5 μg from drinking water. The concentration of uranium in drinking water varies widely, according to local geology. In areas with low concentrations of uranium in drinking water, food is the major source.
7.2 What happens to the DU in munitions?
When a penetrating shell hits an armoured target like a tank the impact produces a combination of DU fragments and aerosols. The dust in the aerosols ignites spontaneously, producing uranium oxide. It usually accounts for between 10-30 per cent of the uranium in the shell, but this can go as high as 70 per cent. Most of the resulting oxide dust stays inside the tank which is hit. This means that breathing in DU dust inside abandoned vehicles is the main hazard after such a hit. DU particles which escape from the scene are deposited rapidly because of the density of the metal, and do not normally disperse easily.
If a DU penetrator misses its target and lands in soft soil it will bury itself between half a metre and several metres down. The uranium then oxidizes and dissolves, slowly. Complete dissolution may take 35 years. The Uranium gradually passes into the surrounding soil, with the highest concentrations near the impact site. Over time, the DU will be slowly removed from the site of deposition and will add to the natural uranium background. The amounts of DU added are too low to increase the total concentrations of uranium in larger areas.
Surveys of DU residues in combat zones have been made in areas of the former Yugoslavia, Kuwait and Iraq. Predicted concentrations of DU in areas with intensive use of DU munitions, using conservative assumptions, are within the typical concentration range of natural uranium in soil. Actual concentrations of DU detected in environmental samples in areas with intensive use of DU ammunition were generally much lower than this, although there were a few exceptional "hot spots”.
The many available measurements show that DU, after military use in combat, will mainly be located inside of military vehicles hit by DU ammunition and in their close vicinity. DU ammunition in soil will slowly corrode and hotspots with high local concentrations of DU may remain locally close to the impact site. Based on the available data, only a very small part of the DU released after the impact on a hard target will be more widely distributed in the environment.
It is possible to use measurements of DU in urine samples to probe whether any released DU has led to human exposure. The measurements must take into account natural intake from food and water, and this is achieved by measuring the precise ratio of the two most prevalent isotopes of uranium. Urine analysis can then be applied to specifically assess human DU exposure by swallowing or breathing. Most such biomonitoring studies have failed to find any DU in urine samples from serving soldiers or from civilians living in areas where DU ammunition was used. Where DU was detected, levels were very low.