Biological monitoring for depleted uranium exposure in U.S. Veterans

Abstract

Background: As part of an ongoing medical surveillance program for U.S. veterans exposed to depleted uranium (DU), biological monitoring of urine uranium (U) concentrations is offered to any veteran of the Gulf War and those serving in more recent conflicts (post-Gulf War veterans).

Objectives: Since a previous report of surveillance findings in 2004, an improved methodology for determination of the isotopic ratio of U in urine ((235)U:(238)U) has been developed and allows for more definitive evaluation of DU exposure. This report updates previous findings.

Methods: Veterans provide a 24-hr urine specimen and complete a DU exposure questionnaire. Specimens are sent to the Baltimore Veterans Affairs Medical Center for processing. Uranium concentration and isotopic ratio are measured using ICP-MS at the Armed Forces Institute of Pathology.

Results: Between January 2003 and June 2008, we received 1,769 urine specimens for U analysis. The mean urine U measure was 0.009 microg U/g creatinine. Mean urine U concentrations for Gulf War and post-Gulf War veterans were 0.008 and 0.009 microg U/g creatinine, respectively. Only 3 of the 1,700 (0.01%) specimens for which we completed isotopic determination showed evidence of DU. Exposure histories confirmed that these three individuals had been involved in "friendly fire" incidents involving DU munitions or armored vehicles.

Conclusions: No urine U measure with a "depleted" isotopic signature has been detected in U.S. veterans without a history of retained DU embedded fragments from previous injury. These findings suggest that future DU-related health harm is unlikely in veterans without DU fragments.

Keywords: bioassay; biomonitoring; depleted uranium; exposure; isotopic analysis.

Figure 1

Summary of urine U surveillance activities from January 2003 through June 2008. The number of samples analyzed is stratified into Gulf War and post-Gulf War veterans. The results of isotopic analyses, which define the presence of DU are presented. “Unknown” indicates samples obtained before July 2003, when routine isotopic analysis on samples was initiated. The three samples with an isotopic signature consistent with DU were from individuals identified to have been injured as a result of friendly fire.

Figure 2

Distribution of urine U results from mail-in specimens from January 2003 through June 2008 plotted as two separate groups: Gulf War (GWI) versus post-Gulf War (PGW) veterans. Samples are ranked from low to high urine U concentration. The different symbols within each group denote whether DU was identified in each of the urine samples. Only three specimens were isotopically consistent with DU in the PGW group. Reference lines are provided on this graph for comparison purposes: Mean total urine U found in a subcohort of U fabrication workers in 1980 (Thun et al. 1985); Means from two populations with known high levels of environmental exposure to U_nat (Kurttio et al. 2002; Orloff et al. 2004); Cut-point established by the Depleted Uranium Follow-up Program to identify high versus low urine U concentrations (McDiarmid et al. 2001a); 95th percentile for urine U from the NHANES 2000–2001 population study for adults ≥ 20 years of age (CDC 2005); mean from the current cohort of 1,769 reported in the present study.