Resolving Whether Inhalation of Depleted Uranium Contributed to Gulf War Illness Using High-Sensitivity Mass Spectrometry

Abstract

Background: Of the hypothesized causes of Gulf War Illness (GWI), a chronic multi-symptom illness afflicting approximately 25 percent of >700,000 military personnel deployed to the 1991 Gulf War, depleted uranium (DU) and exposure to nerve agents have stimulated the most intense international concern. Past depleted uranium research on Gulf War veterans has measured urinary uranium concentration [U] and uranium isotopic ratios with low precision mass spectrometry primarily in GW veterans with retained shrapnel but has not used high precision mass spectrometry to test for an association of GWI with inhaled DU and we set out to test this potential association. Methods: We applied a standard biokinetic model to predict the urinary total [U] and uranium isotopic ratios in urine 18 years after inhalation exposure. We applied high sensitivity mass spectrometry methods capable of detecting the predicted levels in 154 individuals of a population-representative sample of U.S. veterans in whom Gulf War illness had been determined by standard case definitions and DU inhalation exposures obtained by medical history. Results: Methods used in past studies are capable of detecting only the high urinary uranium excretion levels from retained DU shrapnel but not lower levels predicted from DU inhalation. Using high precision mass spectrometry, we found no difference in the 238U/235U ratio in veterans meeting the standard case definitions of GWI versus control veterans, and no differences by levels of DU inhalation exposure. Our bivariate analysis of 236U/238U by 235U/238U showed only the signature of natural dietary uranium, excluding DU inhalation exposures above 0.4 mg, far below the disease-causing threshold. Conclusion: The findings by high precision mass spectrometry support the conclusion that even the highest levels of DU inhalation played no role in the development of Gulf War illness. Other factors including exposure to aerosolized organophosphate compounds (pesticides and sarin nerve agent) remain as the most likely cause(s) of GWI.