Uranium is a radioactive element that can be found naturally in rocks, water, and even human beings. [1,2] Approximately 0.0003% of earth crust and 3.0 μg/L in sea water is made up of uranium. [1] The average concentration of uranium in the human body, resulting from the normal intake of food and water, is approximately 90mg, 66% of which is found in the skeleton, 16% in the liver, 8% in the kidneys, and the remaining 10% in other tissues. [3] Depleted uranium (DU) results from converting natural uranium to enriched uranium for use in nuclear reactors and weapons. [1,2] DU is a dense metal with a high melting point (1132 °C), a tensile strength similar to that of most steels, and a half-life of 4.5 billion years. [1] While NU has the same chemotoxicity as DU, NU has a 60% higher radiotoxicity. [1] NU and DU primarily differ in that DU has approximately three times less U-235 than NU. [1,2]
DU has been used in civilian and military applications as a result of its high density. [2] DU is used as shields in radiation therapy, containers to transport radioactive materials, and counterweights in aircrafts. [2] In addition to its civilian use, DU is used in the military as armor plating since it will not ignite on impact for temperatures below 600°C. [1,4] DU is also used as a tamper in fission bombs and in ammunition. [1,4] The United States has used DU weapons in combat, most notably in the Persian Gulf War and in Bosnia and Kosovo. [1,4]
DU's chemical and radiological toxicities may have negative health effects. [5-10] Health consequences from DU's chemical toxicity result from its inhalation, ingestion, and dermal contact and resulting entry into the bloodstream. [5-10] Once the DU compounds have entered the bloodstream, they are filtered by kidneys. [8] Depending on the level of exposure, however, DU may impair the kidney function by causing damage to the kidney cells. [8] High DU intake over a prolonged period of time can result in acute kidney failure and death. [8] DU's radiological toxicity has also raised health concerns. Studies on troops and local populations where DU ammunition had been used during the Gulf War and Balkan conflicts show that exposure to DU may have increased the probability of individuals developing lung and bone cancer, non-malignant respiratory disease, skin disorders, neurocognitive disorders, chromosomal damage, and birth defects. [6-8] Still, these studies were not conclusive enough to determine the precise observable health effects and residual cancer risk estimates that may arise from moderate exposure to DU. [1]
Depleted uranium is still used today for both civilian and military applications. However, studies suggest that prolonged exposure to the chemical and radiological toxicities of DU may have severe health effects. Though DU may be hazardous to humans at very high levels, more studies need to be conducted to definitively conclude the precise health consequences of DU at more moderate levels.
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[1] A. Bleise, P. R. Danesi and W. Burkart, "Properties, Use and Health Effects of Depleted Uranium (DU): A General Overview," J. Environmental Radioactivity 64, 93 (2003).
[2] M. Betti, "Civil Use of Depleted Uranium," J. Environmental Radioactivity 64, 113 (2003).
[3] N. D. Priest, "The Distribution and Behavior of Metals in Skeleton and Bodies: Studies with Bone Seeking Radionuclide", in Trace Metals and Fluoride in Bones and Teeth, ed. by N. D. Priest and F. L. Van De Vyver (CRC Press, 1990).
[4] C. Giannardi and D. Dominici, "Military Use of Depleted Uranium: Assessment of Prolonged Population Exposure," J. Environmental Radioactivity 64, 227 (2003).
[5] H. Bern and F. Bou-Rabee," Environmental and Health Consequences of Depleted Uranium Use in the 1991 Gulf War," Environment International 30, 123 (2004).
[6] A. Durakovic, "Undiagnosed Illnesses and Radioactive Warfare," Croatian Medical Journal 44, 520 (2003).
[7] A. C. Miller and D. McClain, "A Review of Depleted Uranium Biological Effects: In Vitro and In Vivo Studies," Rev. Environ. Health 22, 75 (2007).
[8] E. S. Craft et al., "Depleted and Natural Uranium: Chemistry and Toxicological Effects," J. Toxicology and Environmental Health 7, 297 (2004).
[9] M. A. McDiarmid et al., "Health Surveillance of Gulf War I Veterans Exposed to Depleted Uranium: Updating the Cohort," Radiation Safety Journal 93, 60 (2008).
[10] W. Burkart, P.R. Danesi and J.H. Hendry, "Properties, Use and Health Effects of Depleted Uranium," International Congress Series 1276, 133 (2005).