Toxicological Evaluation of Depleted Uranium in Rats: Six-Month Evaluation Point

Abstract : The use of depleted uranium (DU) munitions during Desert Storm resulted in a unique type of battlefield casualty, DU shrapnel wounds. The toxicity associated with embedded DU may differ significantly from other metals or other routes of uranium administration. This is a 6-month interim report of an 18- month study that is designed to assess the toxicity of implanted DU pellets. This study evaluates kidney, behavioral, and neural toxicity associated with intramuscularly implanted DU pellets (1-mm x 2-mm) and assesses tissues for histological changes and for uranium content. Rats were assigned to five experimental groups: 1) a non-implanted sham-surgical control group, 2) rats implanted with 20 tantalum (Ta) to control for fragment implantation, 3) rats implanted with low-dose DU (4 DU and 16 Ta pellets), 4) rats implanted with medium-dose DU (10 DU and 10 Ta pellets), and 5) rats implanted with high-dose DU (20 DU pellets). Uranium levels were high and dose-dependent in the kidney, urine, and bone. Despite high uranium levels in the kidney, no renal toxicity was evident. Between 23-26 weeks body weight in high-DU dose animals was significantly lower than controls. Unexpectedly, uranium was found in the brain of DU-implanted animals. No behavioral neurotoxicity was evident. Excitability of hippocampal neurons was reduced in the high DU dose animals at 6 months. These data suggest that at the 6-month time point, renal toxicity may be less of a hazard than anticipated. While these results indicate that toxicity is not evident at 6 months with exposure to embedded DU, there is a need to further investigate long-term effects in light of the high levels accumulated in some body tissues.