The U.S. Army has studied the potential environmental effect of aerosols created when depleted uranium (DU) munitions hit an armored target. In 2004, the U.S. Army reported the results of the "Capstone Study", which was conducted by a team from the following organizations:
This was a 2-part study composed of the Capstone DU Aerosols Study, which analyzed DU aerosols produced in the Abrams tank and Bradley Fighting Vehicle struck by large-caliber DU munitions, and the Capstone DU Human Health Risk Assessment, which used data from the first phase to calculate radiation doses and possible DU concentrations in the body. This estimated the health effect to Service members from DU exposure through contact with tanks and vehicles struck with DU munitions. These studies demonstrated that vehicle ventilation systems are very effective in reducing potential DU exposures of personnel inside vehicles. The risk assessment predicted little or no impact on health of Service members who breathe in DU dust particles while inside tanks or other vehicles hit by DU munitions.
Exposure to Civilians to DU in the Environment
Any civilian exposures to DU in the environment would in nearly every case be lower than the amount of DU inhaled by Service members in a vehicle struck by DU. Based on the projection of military exposures and risks, these civilian exposures would result in little or no risk to health.
Based on measurements made by outside organizations, including the United Nations Environment Programme, observable health effects are not expected from depleted uranium in the environment. The most likely mechanisms through which depleted uranium could be taken into the body of a civilian visiting or living in an area where DU had been used in combat include:
Inhalation
A potential exposure pathway for those visiting or living in DU affected areas after the aerosols have settled is the inhalation of DU particles in the soil that have been re-suspended through the action of wind or human activities. The risk will be lower because the re-suspended uranium particles combine with other material and increase in size and, therefore, a smaller fraction of the uranium inhaled will reach the deeper parts of the lungs.
Ingestion
Another possible route of exposure is through the ingestion of DU contaminated soil. For example, farmers working in a field where DU ammunitions were fired could inadvertently ingest small quantities of soil, while children sometimes deliberately eat soil.
In the long term, small amounts of DU may gain access to ground water and the food chain through migration from the soil or direct deposition on vegetation. Over time, chemical weathering may cause the DU in munitions left in the ground to corrode. Some of the DU in the soil will be soluble and migrate to surface and ground water from where it eventually may be incorporated into the food chain, or consumed directly. It is difficult to predict how long it would take before increased levels of DU could be measured in water and food. The associated risk from ingestion of food is generally low, because uranium is not effectively transported in the food chain.