Q. What is depleted uranium?
A. 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 radiation shielding and aircraft balance control.
Q. What makes depleted uranium a potential hazard?
A. 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.
Q. 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?
A. The health effects of uranium have been studied extensively for over 50 years. This is relevant because chemically, DU has the same properties as natural uranium, while being 40% less radioactive. While natural and depleted uranium are considered chemically toxic, they are not considered a radiation hazard. In May 1989 the Department of Health and Human Services' Agency for Toxic Substances and Disease Registry published a Toxicological Profile for Uranium reviewing and summarizing the key uranium health effects literature. This document was updated in September 1999.
The Department of Defense has comprehensively studied the environmental fate of depleted uranium 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 could be reduced even more by simple, field-expedient measures, especially, avoidance of depleted uranium-contaminated vehicles and sites.
Q. Were any depleted uranium health effects studies conducted after the Gulf War? What were the findings of those studies?
A. The two main areas that were not adequately addressed before the Gulf War were:
The medical implications of embedded DU fragments in people and inhalation exposure estimates for friendly fire incidents, recovery activities, and incidental contact scenarios.
These are recognized weaknesses that are being addressed. 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 began 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 added to the surveillance program in 1999. In 1998, the program was expanded to include Gulf War veterans who may have been exposed 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 that were hit with DU projectiles. The published results of these medical evaluations indicate that the presence of embedded DU fragments is the only scenario predictive of a high urine uranium value, and those with embedded DU fragments continue to have elevated urine uranium levels ten years after the incident. It is unlikely that an individual without embedded DU fragments would have an elevated urine uranium level, and consequently any uranium-related health effects. 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 individuals with elevated levels of urine uranium ten years after the Gulf War have not developed kidney abnormalities, leukemia, bone or lung cancer, or any other uranium-related adverse outcome. The DU Medical Follow-up Program will continue to monitor those individuals with elevated urine uranium levels to enable early detection of any adverse health effects due to their continued exposure to DU.
Q. There are reports from the Balkans and Iraq of individuals recovering the DU penetrators. Are these hazardous?
A. Depleted uranium penetrators are only one of many possible hazards on the battlefield. Civilians and soldiers are strongly discouraged from recovering souvenirs, particularly spent ammunition, from the battlefield.
Fortunately, DU is only mildly radioactive emitting alpha and beta particles, and gamma rays. Alpha particles, the primary radiation type produced by DU, are blocked by skin, while beta particles are blocked by clothing and shoes. While gamma rays are a form of highly-penetrating energy, the amount of gamma radiation emitted by DU is very low. The risk of chemical toxicity is also minimal because there is little likelihood that sufficient quantities of DU could be inhaled or ingested to cause a heavy metal concern.
Q. What has the Defense Department done to protect future generations of service members from accidental exposure to depleted uranium?
A. 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 Deputy Secretary of Defense has ordered the Service Chiefs to ensure that DU awareness training is incorporated into their general military training programs. The U.S. Army's Training and Doctrine Command published Training Support Packages for general DU awareness training and certain specialty training in July 1999. The Marine Corps also uses a three-level DU training program. Both the Marines and Navy use a service-specific variant of the Army's DU Awareness Training video. The Air Force program calls for all personnel on mobility status to receive DU awareness training and has incorporated DU awareness guidance in the Nuclear, Biological, and Chemical handbook carried by all deploying personnel. Complete implementation of the various training programs is underway. The Office of the Special Assistant will continue to monitor the status of the Services' DU training efforts.
Q. In what way has the DoD attempted to categorize and quantify service members' exposure to depleted uranium during the Gulf War?
A. 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 have embedded DU fragments. Others inhaled or ingested DU particles, or had DU dust 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 of exposure Level I is less than the 5 rem per year limit for radiation workers.
The theoretical kidney concentration may have exceeded the maximum permissible concentration guideline of 3 µg of uranium per gram of kidney. However, it is unlikely. These highest exposure estimates were based on two penetrations 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 voluntary Veterans Affairs DU Medical Follow-up program remains the most important source for identifying potential adverse health effects in those friendly-fire victims who have embedded DU fragments. About a quarter of over 60 Level I exposed individuals who have been evaluated still carry DU fragments in their bodies, and they have elevated levels of urine uranium ten years after the Gulf War. None of the individuals with embedded DU fragments have developed kidney abnormalities, leukemia, bone or lung cancer, or any other 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 DU 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 radiation 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 DU 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.
For more information see Tab O of Environmental Exposure Report, Depleted Uranium in the Gulf (II), or "Depleted Uranium-Human Exposure Assessment and Health Risk Characterization in Support of the Environmental Exposure Report 'Depleted Uranium in the Gulf' of the Office of the Special Assistant to the Secretary of Defense for Gulf War Illnesses, Medical Readiness and Military Deployments (OSAGWI)"
Q. What are the health effects of contact with unfired depleted uranium munitions or non-penetrated (intact) armor on the various weapons systems, such as the Abrams Heavy Tank?
A. No adverse health effects are expected from such contact. Unfired depleted uranium munitions are encased in thin metal jackets that seal in alpha and beta particles. The amount of gamma emissions from DU is very low and falls 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. The penetrator rods in the 120mm, 105mm and 30mm rounds are shielded which prevents direct contact with the actual penetrator rod of intact rounds. 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.
Q. 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?
A. . 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.
After the media reports in early 2001, nations who had deployed peacekeepers to the Balkans have begun medical monitoring and epidemiological studies. The objective of the studies is to determine whether there is an increase in medical problems in troops who served in the region when compared to troops who did not. To date, none of these studies have found a connection between DU exposure and leukemia or any other pathology. The United Nations and other international organizations also have conducted environmental surveys in Bosnia-Herzegovina and Kosovo. These surveys consistently have reported no widespread DU contamination and no current impact on the health of the general population or deployed personnel. Reports from the various countries and organizations are in Depleted Uranium Environmental and Medical Surveillance in the Balkans.
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.
Q. 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?
A. Yes, trace levels of transuranics have been found in DU. 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 recycled uranium extracted from spent nuclear fuels 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 radioactive contaminants increase the radiation dose from theDU itself by less than 1 percent, which is considered insignificant.
In March 2001, DOE reported the results of a two-year recycled uranium study that concluded the transuranic content in depleted uranium was very low. The DOE data are consistent with U.S. Army testing of the DU used in armor plate for the Abrams Heavy Tank, which concludes the radioactive contaminants contribute less than a one percent increase in the radioactivity from DU itself. Various NATO countries and the United Nations Environment Programme (UNEP) recently recovered penetrators in the Balkans and tested them for the level of contaminants. Their findings are consistent with DOE/DoD findings. The UNEP concluded that the transuranics have no significant impact on the overall radioactivity or the health risk. These contaminant levels are in the parts per billion range. A part per billion is approximately equivalent to one second in 31.7 years.
Q. With all of the medical and environmental concerns over DU, why hasn't DoD found a substitute for DU?
A. 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 radiological and chemical properties of uranium. While some candidate replacement alloys may not be radioactive, they are not necessarily less toxic to humans.