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aerosol allowed estimates of the likely intake of depleted uranium and health risk. A National Research Council committee reviewed and evaluated the Capstone report and concluded that the “methods and results of the Capstone exposure assessment to be appropriate and well done” (NRC, 2008).

The Sandia report independently analyzed the Capstone test-firing data, estimated intakes by soldiers on the battlefield, and provided predicted risks to health. The Capstone and Sandia reports provide typical intakes and maximum intakes based on the highest observed value in test firings. Direct comparison of the three reports is complicated by use of different methods, terminologies, and parameters. However, all three reports agree on the general extent of the intakes from and health risks posed by depleted uranium.

Level I Exposures

Each of the three reports estimated level I exposure through inhalation by modeling with data from test firings. The data from the Capstone test firings showed a range of inhalation intakes of 250-710 mg of depleted uranium by the surviving crews of an Abrams tank struck by a single large-caliber depleted-uranium penetrator. The range for first responders was 150-200 mg. The Sandia study reported a best estimate of 250 mg and a maximum of 4 g on the basis of the Capstone test-firing data, which are almost identical with those in the Royal Society report.

The three reports had similar estimates of peak renal uranium concentration. A comparison of the level I exposure estimates is shown in Table 5-1. The best estimates of 3 μg/g of kidney and up to 6.5 μg/g of kidney were reported in the Sandia study and the Capstone study, respectively. The central peak of 4 μg/g of kidney was reported in the Royal Society report. The worst-case renal concentration of 400 μg/g in the Royal Society study and the maximum of 53 μg/g in the Sandia study suggest that kidney failure is possible under extreme circumstances.

It is generally accepted that the risk of developing cancer is related to the radiologic dose. Internal exposure to alpha radiation, such as from deposited depleted-uranium aerosols, may increase the risk of cancer. Each report provided an effective dose based on a period of 50 years after exposure.

The predicted increase in lifetime risk of death from lung cancer from level I exposure is about 0.1% in the Royal Society and Sandia reports and 0.06-0.3% in the Capstone report. An increase risk of 0.1% implies that the chance over a person’s lifetime of dying of lung cancer from level I exposure is 0.1% greater than the background rate of cancer mortality. The worst-case estimate of lung cancer in the Royal Society report was 6.5%. The maximum estimates were 3.5% and 0.4-1.4% in the Sandia report and the Capstone report, respectively. The increase in lifetime risk of other fatal cancers, including leukemia, is much lower than the increase in risk of lung cancer.

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