The Capstone Depleted Uranium (DU) Aerosol Study, which generated and characterized aerosols containing DU from perforation of armored vehicles with large-caliber DU penetrators, incorporated a sampling protocol to evaluate particle size distributions. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes as well as the dosimetry of the inhaled particles. These aerosols were collected on cascade impactor substrates using a pre-established time sequence following the firing event to analyze the uranium concentration and particle size of the aerosols as a function of time. The impactor substrates were analyzed using proportional counting, and the derived uranium content of each served as input to the evaluation of particle size distributions. Activity median aerodynamic diameters (AMADs) of the particle size distributions were evaluated using unimodal and bimodal models. The particle size data from the impactor measurements were quite variable. Most size distributions measured in the test based on activity had bimodal size distributions with a small particle size mode in the range of between 0.2 and 1.2 microm and a large size mode between 2 and 15 microm. In general, the evolution of particle size over time showed an overall decrease of average particle size from AMADs of 5 to 10 microm shortly after perforation to around 1 microm at the end of the 2-h sampling period. The AMADs generally decreased over time because of settling. Additionally, the median diameter of the larger size mode decreased with time. These results were used to estimate the dosimetry of inhaled DU particles.
SummaryArmor-piercing, depleted-uranium (DU) munitions were used by the U.S. Armed Forces on the battlefield for the first time during the 1991 Gulf War Operation Desert Storm (ODS).( ) a Although the U.S. Army has conducted periodic impact tests on armored targets, the tests involved only limited sampling to characterize the aerosols that form when DU penetrators impact and perforate targets. As a consequence, the available data were insufficient for performing human health risk assessments. To remedy this, the U.S. Department of Defense (DoD) committed to obtaining more complete data about aerosols generated by the impact and perforation of armored vehicles by DU munitions to support a revised and updated personnel exposure assessment and human health risk characterization. The program arising from this commitment is the Capstone DU Aerosol Characterization and Risk Assessment Program consisting of two separate components. The first is the Capstone DU Aerosol Study, in which DU aerosols were generated through perforation of armored target vehicles, and the chemical and physical properties of aerosols generated were characterized. The study methods and results are presented in this report. The second component of the program is the Human Health Risk Assessment, documented in the Human Health Risk Assessment of Capstone Depleted Uranium Aerosols (Guilmette et al. 2004). S.1 PurposeUnder a program jointly sponsored by the Office of the Special Assistant for Gulf War Illnesses, Medical Readiness and Military Deployment (OSAGWI) ( ) b and the U.S. Army, the Army Heavy Metals Office provided oversight to the Capstone DU Aerosol Study, which was designed to quantify and characterize DU aerosols inside, on, and near Abrams tanks and Bradley Fighting Vehicles (also referred to as Bradley vehicles) struck by large-caliber DU (LC-DU) penetrators. This report, which documents the Capstone study, is the sourcebook of data from which reasonable and appropriate data could be selected for assessing exposure and characterizing human health risks to personnel who were exposed to aerosols during the Gulf War/ODS or potentially could be exposed to aerosols in future military activities. These data are expected to fill many gaps in available aerosol knowledge, thereby helping risk assessors to better estimate the health risks from DU aerosols to affected personnel.The aerosol data derived from this study provides the basis for modeling input parameters by summarizing the bounds and characteristics of typical aerosols generated by perforating armored vehicles with LC-DU penetrators. The test results will be used to update the human health risk characterizations for OSAGWI Gulf War/ODS exposure scenarios, and to determine if changes in personnel protective measures are warranted to reduce risks to DoD personnel in the future. S.2 Investigation TeamAn independent subject matter expert from Pacific Northwest National Laboratory (PNNL) directed the Capstone DU Aerosol Study. S.3 Study OverviewThe Capstone DU Aerosol Study involved ...
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