Over the years, the U.S. military has requested assistance from CDC's Environmental Health Laboratory to determine whether or not their personnel have been exposed to toxic chemicals in this country or abroad. The laboratory has collaborated on multiple exposure studies, most recently with the Department of Defense on a study of possible exposure of some members of an Army National Guard unit that had been deployed to Iraq. The unit had expressed concerns about possible exposure to depleted uranium in their bivouac location. CDC's Environmental Health Laboratory as well as two other laboratories—the Armed Forces Institute of Pathology and the U.S. Army's Center for Health Promotion and Preventive Medicine—analyzed the same samples, looking first at levels of total uranium in the urine samples provided and then, depending on those test results, at isotope ratios. Like all elements in the periodic table, uranium can exist as different isotopes.
In its natural occurrence, uranium primarily exists at a ratio of 235U/238U of 0.00725. Substances with ratios of 235U/238U that are less than 0.00725 are said to contain depleted uranium, and substances with ratios of 235U/238U that are greater than 0.00725 are said to contain enriched uranium. Because of its density and hardness, depleted uranium is used in vehicle armor and armor-piercing shells. If in fact unit personnel had been exposed to depleted uranium by breathing the air during battles when depleted uranium could have been used and if their levels of depleted uranium were higher than typically experienced by people not involved in military operations, they may have needed treatment, since health effects may occur from high exposure.
CDC scientists tested the urine of unit soldiers for total uranium and measured the 235U/238U ratio. None of the soldiers tested had total uranium levels that were outside the reference range of levels found in people living in the United States, and all uranium found had ratios indicating that the sources of exposure were natural and not from military use.
