Radiological risk assessment of Capstone depleted uranium aerosols

Assessment of the health risk from exposure to aerosols of depleted uranium (DU) is an important outcome of the Capstone aerosol studies that established exposure ranges to personnel in armored combat vehicles perforated by DU munitions. Although the radiation exposure from DU is low, there is concern that DU deposited in the body may increase cancer rates. Radiation doses to various organs of the body resulting from the inhalation of DU aerosols measured in the Capstone studies were calculated using International Commission on Radiological Protection (ICRP) models. Organs and tissues with the highest calculated committed equivalent 50-y doses were lung and extrathoracic tissues (nose and nasal passages, pharynx, larynx, mouth, and thoracic lymph nodes). Doses to the bone surface and kidney were about 5 to 10% of the doses to the extrathoracic tissues. Organ-specific risks were estimated using ICRP and U.S. Environmental Protection Agency (EPA) methodologies. Risks for crewmembers and first responders were determined for selected scenarios based on the time interval of exposure and for vehicle and armor type. The lung was the organ with the highest cancer mortality risk, accounting for about 97% of the risks summed from all organs. The highest mean lifetime risk for lung cancer for the scenario with the longest exposure time interval (2 h) was 0.42%. This risk is low compared with the natural or background risk of 7.35%. These risks can be significantly reduced by using an existing ventilation system (if operable) and by reducing personnel time in the vehicle immediately after perforation.