takes for the human body to eliminate half the amount in the body) for uranium is about 15 days. The aerosol or spallation frangible powder produced by impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites, leading to possible inhalation by human beings. The actual level of acute and chronic toxicity of DU is also controversial. Several studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic, genetic, reproductive, and neurological effects from chronic exposure. According to an article in Al Jazeera, DU from American artillery is suspected to be one of the major causes of an increase in the general mortality rate in Iraq since 1991. A 2005 epidemiology review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU." A 2021 study concluded that DU from exploding munitions did not lead to Gulf War illness in American veterans deployed in the Gulf War. According to 2013 study, despite the use of DU by coalition forces in Fallujah, no DU has been found in soil samples taken from the city,; although another study of 2011 had indicated elevated levels of uranium in tissues of the city inhabitants. History Enriched uranium was first manufactured in the early 1940s when the United States and Britain began their nuclear weapons programs. Later in the decade, France and the Soviet Union began their nuclear weapons and nuclear power programs. Depleted uranium was originally stored as an unusable waste product (uranium hexafluoride) in the hope that improved enrichment processes could extract additional quantities of the fissionable U-235 isotope. This re-enrichment recovery of the residual uranium-235 is now in practice in some parts of the world; e.g. in 1996 over 6000 metric tonnes were upgraded in a Russian plant. It is possible to design civilian power-generating reactors using unenriched fuel, but only about 10% of those ever built (such as the CANDU reactor) use that technology. Thus most civilian reactors as well as all naval reactors and nuclear weapons production require fuel containing concentrated U-235 and generate depleted uranium. In the 1970s, the Pentagon reported that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition could not penetrate. The Pentagon began searching for material to make denser armor-piercing projectiles. After testing various metals, ordnance researchers settled on depleted uranium.