By H. Patricia Hynes, Sardor Ibragimov
Boston University School of Public Health, September 2003
1. What is Depleted Uranium?
Uranium (U) is a naturally occurring radioactive and chemically toxic metal that is widespread in the earth’s crust. The average amount of uranium in soil is about 3 grams per ton or 3 mg/kg. Natural uranium consists of three atomic components called isotopes: U238 (99.27%) and minute amounts of U235 and U234. Uranium is enriched for use in nuclear power reactors and nuclear weapons by increasing its percentage of U235.
Depleted uranium (DU) is the waste product of the uranium enrichment process. It consists of the same components as natural uranium but has differing proportions, with slightly more U238 and a reduced amount of U235. Uranium’s radioactivity is largely determined by the quantity of U235 it contains. DU has about 60% of the radioactivity of natural uranium (1). The United States has stockpiled an estimated 450,000 tons of DU (2).
2. What are the current uses of DU?
Civilian: DU is currently used in hospital irradiation shields, containers that transport radioactive substances, wide-bodied aircraft components, and petroleum drilling equipment (3, 4, 5).
Military: DU is used by the U.S. and other militaries in both defensive armor and armor piercing ammunition that is known as DU penetrators. These weapons have a solid rod of DU that increases their ability to penetrate heavily armored vehicles because DU sharpens upon impact and self-ignites. DU weapons, thus, increase the potential of detonating combustible vehicles such as tanks and destroying buildings (2).
3. How much DU has been used in recent wars?
An estimated 320 tons of DU were used in weapons during the 1991 Gulf War; about 12 tons were used in the Balkans in the late 1990s (6). While there is no clear information about the amounts of DU used in Afghanistan, it is likely that US forces used DU munitions in the war in Afghanistan because US weapons systems that shoot DU were used in that war (7). Available information suggests that the US and UK forces released approximately 90-180 tons of DU during the 2003 Gulf War in Iraq (8), although more recent estimates are between 110-165 tons (7). Much of DU munitions were likely fired near urban areas in the second Gulf War, which would create higher risk of exposure for the civilian population (8).
4. What happens when DU weapons strike a target?
U.S. test data show that approximately 20% of a DU weapon penetrator becomes aerosolized particles upon impact with an armored vehicle (9). A 120 mm DU penetrator, when fired from an Abrams tank, created 2 to 7 pounds of uranium oxide dust upon impact, according to U.S. Army tests. From 50-96% of the dust are respirable particles, the majority of which, if inhaled, can remain in the lungs for years (10). Some fraction of the aerosolized DU particles may be dispersed and spread by wind. A significant amount, however, contaminates soil within a few hundred yards of the target (11).
5. What are the pathways of exposure to DU?
Both soldier and civilians in war and post-war situations are at risk of internal and external exposure to DU through inhalation, ingestion of DU particles, and skin exposure. Those riding in a vehicle struck by a DU shell experience an acute exposure to DU. Civilians can be exposed when they are victims of a DU weapon that strikes a nearby target and generates aerosolized fine particles. Soldiers and civilians in conflict areas can suffer DU exposure from embedded shrapnel, with DU entering the blood stream through the wound. Prolonged exposure, such as that of soldiers driving for long periods in DU vehicles equipped with DU ammunition, may result in soldiers exceeding regulatory limits for external exposure (10).
The recent assessment in the Balkans by the United Nations Environment Program (UNEP) revealed soil contamination close to the site of embedded DU penetrators, from within a few yards to within a few hundred yards. Soil within a yard of the DU penetrator exceeded internationally recommended standards (12, 13, 14). Children playing near these sites are at risk of ingesting contaminated soil and breathing resuspended fine particles (1). A recent UNEP study in the Balkans also recorded DU contamination of groundwater in Bosnia-Herzegovina from DU rods that had corroded and released soluble forms of DU that reached groundwater (15). A journalistic report on Iraqi children working to support their families revealed that the children are sorting through blasted Iraqi tanks and armored vehicles, stockpiled in scrap yards by US military contractors, in order to salvage metal parts to sell to metal dealers (16). If the vehicles were hit by DU weapons, the interior of the vehicles would be highly contaminated with DU particles and expose the children to ingestion and inhalation of DU.
Groundwater in Concord, Massachusetts, USA has been severely contaminated by DU waste, which was stored and dumped at a manufacturing facility there. Investigations of the water in wells on site revealed uranium isotopes of DU levels up to 3,000 times the permitted state level for drinking water (8).
6. What are the human health impacts of exposure to DU? Is it harmful?
The two primary organs to suffer from exposure to DU are the lung and the kidney. The lung is exposed after inhalation of DU particles and the kidney filters and excretes DU dissolved from particles that were ingested and inhaled. The health effects of DU exposure depend on the solubility of DU particles. Relatively insoluble particles in the lung will remain there longer, exposing surrounding cells to radiation through the process of radioactive decay. The rate at which DU dissolves depends on its chemical form and the solvents it contacts. Human body fluids can carry DU to many organs and tissues. Soluble forms of DU will dissolve in the blood and circulate to other organs and systems, with potential toxic effects on those organs, before being excreted (17).
The heavy-metal chemical toxicity of DU is the same as that of natural and enriched uranium. Both possess a high chemical affinity for biological molecules (18). They may cause cellular necrosis (or death of cells) and cellular atrophy in the kidney with the risk of impairing the kidney’s function of filtering impurities and toxins from the blood (17).
Thus far, no conclusive studies have been conducted that demonstrate the long-term human health effects and harm of exposure from DU. Currently 29 veterans from the 1991 Gulf War who have DU metal shrapnel fragments embedded in their body and 38 non exposed veterans are being followed clinically. Those with DU fragments were excreting higher levels of DU in urine 7 years after exposure, which indicates that DU continues to enter the bloodstream and circulate to other parts of their body. The study found subtle central nervous system and reproductive effects in the exposed veterans (19). Research on mice by the US military has shown that DU particles from implanted DU fragments are deposited from the bloodstream into the bone and to a lesser degree in the brain, testes, and lymph nodes and that DU crosses the placenta from the mother into the fetus (20). Research on rats shows that DU accumulates in the testes, bone, kidney and brain; and in vitro tests found that DU may be genotoxic and mutagenic (21). Other research found that implanted DU fragments caused soft tissue sarcomas in the muscles of rats (22).
Animal studies are not a reliable source of evidence for human health effects because of differences in exposure scenarios, relative concentration doses, and physiology. However, the animal studies signal serious concern for the fate of DU in the human body. The number of exposed 1991 Gulf War veterans who are being followed clinically is small; and there has not been sufficient time since their exposure to draw definitive conclusions. The lack of scientific evidence of direct human harm from DU exposure is an indictment of the paucity of research not a proof of no harm. Thus, the decision to use DU in weapons has been made in an environment of uncertainty about the health impacts on those exposed in conflict and post-conflict situations.
7. What can we conclude about the risks of using DU weapons?
Many forecast the proliferation of DU weapons because of DU’s penetration and ignition characteristics and as a means of disposing the stockpiles of DU in countries that are enriching uranium. Most armed forces will not be protected from exposure to DU since few militaries acknowledge that DU exposure is or may be harmful. Although there is solid evidence that DU weapons contaminate soil and air upon impact, it is unlikely that contaminated soil will be removed or cleaned by those who used the weapons or by the country under siege because other post-war crises, such as rebuilding infrastructure, will claim the scarce resources. Civilian populations in DU contaminated sites are likely to be exposed to hot spots of DU soil contamination and of groundwater contamination, since systematic surveillance of soil and groundwater in areas of conflict where DU weapons have been employed has not been the norm.
We conclude that DU exposure in and after war adds long-term radiation and chemical exposure to the already existing risks of death, injury, and environmental damage from war. We advocate that depleted uranium not be used to augment weapons of war because its health effects on those acutely and chronically exposed are not known, because it persists in the environment in zones of conflict, and because contaminated sites are not adequately documented and remediated.
Editorial Assistance, Genevieve Howe
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