Depleted uranium is a very dense (1.7 times denser than lead) metal by-product of the process by which natural uranium is enriched to produce reactor fuel and nuclear weapons components. This by-product, which is 40% less radioactive than natural uranium, is called depleted uranium (DU). Because the enrichment process sometimes uses recycled uranium nuclear fuel rods, trace levels of impurities, such as plutonium, neptunium, americium, technetium, and uranium-236 are introduced into the depleted uranium. These trace impurities, in parts per billion, are inconsequential from a chemical toxicity and radiological standpoint. They have no impact on chemical toxicity and increase the radioactivity by less than one percent.^[1]

Depleted uranium is used as radiation shielding and in military munitions, military armor, and counterweights and ballast for some missiles, yachts, and aircraft. These uses take advantage of DU’s density (weight per unit volume). Military DU munitions, first used in combat in the Gulf War, also take advantage of DU’s hardness and resistance to mushrooming on impact. In fact, DU penetrators actually become sharper as they penetrate armor. Penetrators made out of other materials (tungsten for example) mushroom and become blunt as they penetrate. (See "DU—How is it Used and Why?" under Current Issues at http://deploymentlink.osd.mil/.) This allows a DU round to more effectively penetrate thicker armor than non-DU penetrators.

The following US military munitions contain a DU penetrator: 105mm and 120mm tank rounds, 20mm rounds fired by the US Navy’s Close-In Weapons System, 25mm rounds fired from the US Marine Corps’ AV-8 Harrier aircraft, 25mm rounds fired from the US Army Bradley Infantry Fighting Vehicle, and 30mm rounds fired from the US Air Force’s A-10 Thunderbolt aircraft (Figure 1). Only the A-10 aircraft fired DU munitions in the Balkans.

Figure 1. DU penetrator from the A-10 30 mm round

The A-10s fired approximately 10,000 30mm DU rounds (3.3 tons of DU) at 12 sites in Bosnia-Herzegovina in 1994-95. In 1999, they fired around 31,000 DU rounds (10.2 tons of DU) at 85 locations in Kosovo.^[2] Since then, many nations that deployed personnel to the Balkans Theater tested the areas their troops occupied for DU contamination in order to assess the health risks. In addition, several international organizations also researched depleted uranium and tested the Balkans environment to determine levels of contamination and evaluate all routes of exposure (ways that DU could get into the body from the environment).

Exposure to depleted uranium occurs primarily through inhalation, ingestion, and to a lesser degree, external irradiation.^[3] When depleted uranium rounds strike a hard surface, small pieces can fracture off and ignite, producing depleted uranium oxides in the form of a very fine dust. Most of this material settles close to the impact site and the remainder is rapidly diluted and dispersed by the effects of wind and weather. The very fine DU oxide dust can be inhaled by anyone nearby at the time of impact or resuspended and inhaled later. We all breathe in and consume in food and water small quantities of more radioactive natural uranium every day. While breathing or ingesting very large doses of natural or depleted uranium could cause kidney problems or damage lung tissue, these problems have not been evident in medical follow-up of Gulf War veterans with the highest DU exposures (i.e., surviving crew members of armored vehicles struck by DU rounds). (See "DU-Health Concerns" under Current Issues at http://deploymentlink.osd.mil/ or Chapter III of "Environmental Exposure Report; Depleted Uranium in the Gulf War (II)" (http://www.gulflink.osd.mil/du_ii/du_ii_s03.htm) for more details on depleted uranium’s health effects.)