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What is depleted uranium?

Depleted uranium is what is left over when most of the highly radioactive types (isotopes) of uranium are removed for use as nuclear fuel or nuclear weapons. The depleted uranium used in armor-piercing munitions and in enhanced armor protection for some Abrams tanks is also used in civilian industry, primarily for stabilizers in airplanes and boats.

What makes depleted uranium a potential hazard?

Depleted uranium is a heavy metal that is also slightly radioactive. Heavy metals (uranium, lead, tungsten, etc.) have chemical toxicity properties that, in high doses, can cause adverse health effects. Depleted uranium that remains outside the body can not harm you.

A common misconception is that radiation is depleted uranium's primary hazard. This is not the case under most battlefield exposure scenarios. Depleted uranium is approximately 40 percent less radioactive than natural uranium. Depleted uranium emits alpha and beta particles, and gamma rays. Alpha particles, the primary radiation type produced by depleted uranium, are blocked by skin, while beta particles are blocked by the boots and battle dress utility uniform (BDUs) typically worn by service members. While gamma rays are a form of highly-penetrating energy , the amount of gamma radiation emitted by depleted uranium is very low. Thus, depleted uranium does not significantly add to the background radiation that we encounter every day.

When fired, or after "cooking off" in fires or explosions, the exposed depleted uranium rod poses an extremely low radiological threat as long as it remains outside the body. Taken into the body via metal fragments or dust-like particles, depleted uranium may pose a long-term health hazard to personnel if the amount is large. However, the amount which remains in the body depends on a number of factors, including the amount inhaled or ingested, the particle size and the ability of the particles to dissolve in body fluids.

Were any studies on the health effects of depleted uranium ever conducted prior to the onset of the Gulf War? What were the findings of those studies?

The health effects of uranium have been studied extensively for over 50 years. In September 1999 the Agency for Toxic Substances and Disease Registry published a Toxicological Profile for Uranium, an update to the original profile published in May 1989. While natural and depleted uranium are considered chemically toxic, they are not considered a radiation hazard.

The environmental effects of depleted uranium have been studied comprehensively by a wide range of governmental and non-governmental bodies both before and after the Gulf War. Burn tests and other evaluations performed under simulated battlefield conditions indicated that the health risks associated with the battlefield use of depleted uranium were minimal and even those could be reduced even more by simple, field-expedient measures, especially, avoidance of depleted uranium-contaminated vehicles and sites. During and after the Gulf War, personnel awareness of the hazards posed by battlefield depleted uranium contamination was generally low. As a result, many personnel did not practice field-expedient measures that would have prevented or mitigated possible exposures.

The two main areas that were not adequately addressed before the Gulf War were:

These are weaknesses that we have recognized and are addressing. The December 19, 2000 Environmental Exposure Report, Depleted Uranium in the Gulf (II) includes the Army's latest health risk exposure estimates for various Gulf War exposure scenarios. Health risk estimates for DU-contaminated vehicle recovery and incidental contact scenarios indicate that these exposures were well within safety standards. Because of gaps in data pertaining to uranium oxide dust levels inside DU-struck vehicles, exposure estimates for personnel inside DU-struck vehicles at the time of impact, or immediately afterwards, were based on conservative assumptions. These estimates for this highest exposed group indicated that medical follow-up was warranted. DOD is currently in the process of conducting additional live-fire testing in order to further refine the exposure estimates for those troops in or around vehicles when they were hit by DU munitions. It is important to note that over 60 friendly-fire victims have been evaluated by the voluntary VA DU Medical Follow-up Program. Aside from the problems associated with their traumatic injuries, to date, this follow-up program has attributed no illness or other harmful effects in the evaluated veterans to DU.

The voluntary Veterans Affairs DU Medical Follow-up Program was begun in 1993-1994 with the medical evaluations of 33 friendly-fire DU-exposed veterans, many with embedded DU fragments. An additional 29 of the friendly-fire victims were later added to the surveillance program in 1999. In 1998, the program was enlarged to assess the wider Gulf War veteran community's exposure to DU through close contact with DU munitions, inhalation of smoke containing DU particulate during a fire at the Doha depot or while entering or salvaging vehicles or bunkers that were hit with DU projectiles. The published results of these medical evaluations conclude that the presence of retained DU fragments is the only scenario predictive of a high urine uranium value, and those with retained DU fragments continue to have elevated urine uranium levels nine years after the incident. It is unlikely that an individual would have an elevated urine uranium result, and consequently any uranium-related health effects, in the absence of retained DU fragments. Those individuals with normal urine uranium levels now are unlikely to develop any uranium-related toxicity in the future, regardless of what their DU exposure may have been in the Gulf War. Those DU-exposed friendly fire individuals with elevated levels of urinary uranium nine years after the Gulf War have not developed kidney abnormalities, leukemia, bone or lung cancer, or any classical uranium-related adverse outcome. The DU Medical Follow-up Program will continue to evaluate these individuals with elevated urine uranium levels to enable early detection of potential untoward health effects in the future due to their continued chronic exposure to DU.

There are reports from the Balkans and Iraq of individuals recovering the DU penetrators. Are these hazardous?

Depleted uranium penetrators are only one of many possible hazards on the battlefield. Civilians and soldiers are strongly discouraged from recovering souvenirs from the battlefield or climbing on or around damaged equipment. For example, some Eastern Bloc equipment also contains other more highly radioactive sources such as radium dials as well as asbestos. There is also a possible problem with unexploded munitions. As stated before, DU is only mildly radioactive. Depleted uranium emits alpha and beta particles, and gamma rays. Alpha particles, the primary radiation type produced by depleted uranium, are blocked by skin, while beta particles are blocked by the boots and battle dress utility uniform (BDUs) typically worn by service members. While gamma rays are a form of highly-penetrating energy, the amount of gamma radiation emitted by depleted uranium is very low. The threat of chemical toxicity would also be minimal because there is little likelihood that sufficient quantities of DU could be inhaled or ingested to cause a heavy metal concern.

What has the Defense Department done to protect future generations of service members from accidental exposure to depleted uranium?

The Department of Defense is fully aware of its responsibility for the safe use of depleted uranium. Since the Gulf War, the DoD has dramatically stepped up its emphasis on increasing soldier and leader awareness of the hazards associated with the battlefield use of depleted uranium. The U.S. Army's Training and Doctrine Command published Training Support Packages for respective training schools in September 1997. The Deputy Secretary of Defense has ordered the Service Chiefs to ensure that DU awareness training is incorporated into the general military training program. Implementation of the various training programs is underway. The Office of the Special Assistant will continue to monitor the status of the Services' depleted uranium training efforts.

In what way has the DoD attempted to track service members exposed to depleted uranium during the Gulf War?

We have categorized the exposure scenarios into three levels based on their relative exposures. Level I is the highest exposure group, including 102 soldiers who were in, on, or near combat vehicles at the time they were struck by depleted uranium rounds, and an estimated 30 to 60 soldiers who entered these vehicles immediately afterwards to perform combat rescue. Depleted uranium metal fragments struck a number of soldiers, and some of these still retain embedded depleted uranium fragments. Others inhaled or ingested depleted uranium particles, or had depleted uranium contaminate their wounds. The U.S. Army's Center for Health Promotion and Preventive Medicine preliminary estimate of the highest exposure level were based on test data that assumed two depleted uranium rounds impacted and penetrated the depleted uranium armor of an Abram's heavy armor model tank. The estimated radiation dose was less than the 5 rem per year limit for workers. The theoretical kidney concentration could have exceeded the maximum permissible concentration guideline of 3 g of uranium per gram of kidney. However, it is unlikely. These highest exposure estimates were based on two perforations of DU armor by 120mm DU rounds. The Department of Defense used the DU on DU exposure data because it had no exposure data on DU rounds penetrating non-DU armor. It should be noted that there were no penetrations of DU armor during the Gulf War and only two Abrams tanks were actually penetrated by two DU penetrators. In addition, the amount of DU aerosol generated by a DU round penetrating a Bradley Fighting Vehicle would be much less than that produced by a DU round penetrating an Abrams tank because the armor of the Abrams tank is harder to penetrate than the Bradley Fighting Vehicle. The Department of Defense used the DU-on-DU exposure data because it had no exposure data on DU rounds penetrating non-DU armor.

The voluntary Veterans Affairs DU Medical Follow-up program remains the most important source for identifying potential untoward health effects in those friendly-fire victims who have retained DU fragments. About a quarter of the over 60 Level I exposed individuals who have been evaluated still carry DU fragments in their bodies, and they have elevated levels of urinary uranium nine years after the Gulf War. The present health status of this cohort shows they have not developed kidney abnormalities, leukemia, bone or lung cancer, or any classical uranium-related adverse outcome.

Level II exposures comprise around 200 soldiers who worked in and around combat vehicles (mainly U.S. friendly fire vehicles) struck by depleted uranium and as many as 600 personnel who took part in the clean up after the fire at Camp Doha. These exposures resulted in significantly lower estimated intakes of depleted uranium than the Level I exposures. The radiation estimates were less than the 0.1 rem per year guideline for members of the general public and much less than the 5 rem per year limit for workers. The chemical exposure estimates were also well below the chemical toxicity guidelines. Therefore, no adverse health effects are expected from the Level II exposures.

Level III is an "all others" category for personnel whose contacts with depleted uranium were very brief and are highly unlikely to have resulted in any medically significant exposure taking place. This group includes curious personnel who entered Iraqi equipment or personnel down wind from vehicles that burned after being struck by depleted uranium rounds. This group’s estimated exposures were minimal.

What are the health effects of contact with unfired depleted uranium munitions or unperforated (intact) armor on the various weapons systems, such as the Abrams Heavy Tank?

Unfired depleted uranium munitions are encased in thin metal jackets that seal in alpha and beta particles, and allow only extremely slight gamma emissions which fall well below regulatory health and safety limits. Similarly, depleted uranium panels used in tank armor pose no health risk because the depleted uranium is sealed inside several inches of regular steel armor. Alpha radiation, which is the major concern for internalized depleted uranium, is not an external concern because alpha radiation does not penetrate the outer layers of skin. The second source of radiation is from the depleted uranium rounds stored on board the tank. While soldiers are exposed to an increased level of radiation from the stored munitions, the cumulative exposure levels for tank crewmembers are within applicable guidelines. Since depleted uranium munitions are only used in combat, only forward-deployed vehicles are routinely uploaded with depleted uranium munitions.

While it is impossible to evaluate all potential exposure scenarios, each of the major weapon systems have been fully evaluated and all of the routine exposures are well within exposure guidelines. In fact, radiation levels measured inside the turret of an Abrams Heavy Armor Tank are below background levels measured outside the turret because armor shields the tank occupants from cosmic and terrestrial radiation sources. Crewmembers have their overall radiation exposure reduced by working inside the tank.

The most frequently cited example of radiation exposure is holding a bare penetrator rod, which is impossible as long as the rounds are intact. The penetrator rods in the 120mm, 105mm and 30mm rounds are shielded which prevents direct contact with the actual penetrator rod. But even when holding a bare penetrator rod, an individual could hold the rod for 250 hours before reaching the extremity or skin limit of 50 rem. Contrary to some claims, the appropriate criteria is 50 rem rather than 5 rem because the exposure is to the extremity (hand) or to the skin and not to the whole body.

The European press in particular has been raising concerns of increased rates of leukemia in European troops that have been stationed in the Balkans. Can exposure to DU be the cause of these cases of leukemia?

It is highly unlikely that exposure to DU ammunition would cause leukemia. The Agency for Toxic Substances and Disease Registry of the U.S. Department of Health and Human Services stated in its Toxicological Profile for Uranium, "[n]o human cancer of any type has ever been seen as a result of exposure to natural or depleted uranium." A 1999 RAND study concluded, "there are no peer-reviewed published reports of detectable increases of cancer or other negative health effects from radiation exposure to inhaled or ingested natural uranium at levels far exceeding those likely in the Gulf." Exposures in the Balkans should be no more than those in the Gulf.

Excess leukemia incidence among those exposed to radiation (atomic bomb survivors) has been recognized only with doses in the range of 1 Sievert (100 rem) or more to the bone marrow. In the body, uranium concentrates on the bone surface rather than in bone marrow. Under these conditions irradiation of bone marrow by uranium’s alpha particles would be almost impossible. The scenarios for the highest potential exposure to DU in the Gulf War (friendly fire incidents, Level I) had estimated doses in the range of 0.05 Sv (5 rem). Incidental or casual exposures (Levels II and III) are estimated to be orders of magnitude less. To the extent that NATO forces in the Balkans had any exposure to DU, it is difficult to imagine exposure greater than Level II exposure scenarios.

For male, active duty military personnel in the U.S. military, the average frequencies of hospitalization for malignant disease are:

Depending upon how many NATO forces deployed to Bosnia and how many years have passed since their return, it should be possible to calculate the expected frequency of leukemia among these troops. News accounts state that approximately 60,000 Italian troops and 15,000 civilians have served in the Balkans since 1995. One could project that this group of 75,000 adults would have experienced seven to ten cases of leukemia during the six years since 1995. Similarly, one could project several hundred cases of cancer of all types.

Leukemias following high doses of radiation peak in frequency five to seven years after exposure. Media accounts of leukemia cases and deaths within months of return from the Balkans are not consistent with current scientific understanding of the time course of radiation-induced leukemia.

Press accounts have indicated the presence of trace levels of plutonium and other contaminants in DU that are indicative of recycled nuclear fuel. Is this true? How did these contaminants get in the DU and does it change your evaluation of the health hazards associated with DU exposure?

The Department of Energy operated three gaseous diffusion plants (Paducah, Kentucky; Portsmouth, Ohio; and Oak Ridge, Tennessee) where they enriched uranium for nuclear weapons and power plants; creating depleted uranium as a by-product. Some or all of these plants received uranium extracted from spent nuclear fuels for recycling in the '50s, '60s, '70s, and '80s. Uranium extracted from spent nuclear fuels included low levels of transuranics (americium, neptunium, and plutonium), technetium-99, and uranium-236. The gaseous diffusion process concentrates these contaminants in the enriched uranium and decreases the levels in the depleted uranium so that only trace quantities remain. The DoE plants have established maximum allowable levels for radioactive contaminants in the enriched uranium extracted from recycled nuclear fuel. Routine monitoring has documented contaminant levels below these allowable levels in post-1980 sampling. DoE’s plant at Fernald has received and/or shipped loads from almost all of the DU produced by the gaseous diffusion plants and tested subsets. These data, included in a draft DoE report dated June, 2000, indicate that radioactive contaminants increase the radiation dose from the DU itself by less than 1 percent. This result agrees with the U.S. Army's testing of the DU used in its armor plate for the Abrams Heavy Tank.

Department of Energy staff have indicated that their testing is representative of all DoD DU applications. The testing being performed by the United Nations Environmental Programme (UNEP) team is not a simple task. The contaminant levels are in the part per billion range. A part per billion is approximately equivalent to one second in 31.7 years.

With all of the medical and environmental concerns over DU, why hasn't DOD found a substitute for DU?

Each weapon system that uses DU has undergone extensive developmental testing and evaluation. As part of that process, DOD evaluates possible alternative metal alloys considering operational requirements and medical/environmental impacts. As improvements have been made in the "hardness" of armored vehicles, tests have demonstrated that DU offers superior performance to all other alloys.

DOD must also evaluate the environmental and medical consequences of exposure to any new alloy. Uranium has an advantage in this arena over several candidate materials because of the extensive database on uranium. While some candidate replacement alloys may not be radioactive, they are not necessarily less toxic to humans.