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.
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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.
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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.
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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:
The medical implications of embedded fragments and
Exposure estimates for friendly fire incidents, recovery activities, and incidental contact scenarios.
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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. [...] 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.
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Civilians and soldiers are strongly discouraged from recovering souvenirs from the battlefield or climbing on or around damaged equipment.
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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.
US Military Fact Sheet on Depleted Uranium