between urinary uranium and the accuracy impairment (A-IIac) index in 2001 and 2003 surveillance, but the authors noted that the result was based on test performance of two veterans whose uranium concentrations were exceedingly high.
The committee concludes that there is inadequate/insufficient evidence to determine whether an association between exposure to uranium and nonmalignant diseases of the nervous system exists.
Overall, published studies of neurologic outcomes are either negative studies that do not find any evidence of health effects of exposure to depleted uranium or relatively small studies, such as the Depleted Uranium Follow-up Program at the BVAMC, that find inconstant associations. As described in Chapter 3, the results of studies in animal models indicate that depleted uranium is a toxicant capable of crossing the blood-brain barrier. Data on effects are inconsistent; some animal studies report behavioral changes, and others do not. Although at high concentrations different forms of uranium might be associated with some subtle neurologic dysfunction in animals, the relevance of these observations to humans remains unknown. On the basis of the available evidence, the committee would assign a high priority to further study of an association between exposure to depleted uranium and neurologic effects.
A few studies examined the effects of natural or depleted uranium on human reproduction and development (see Table 8-18). McDiarmid and colleagues evaluated endocrinologic function in Gulf War veterans by measuring blood concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, testosterone, thyroid-stimulating hormone, and free thyroxine. Study authors also assessed semen for a number of characteristics, including volume, concentration, structure, and motility. A statistically significant difference was observed in mean prolactin concentrations, which were 1.66 and 12.47 μg/g of creatinine (p = 0.04) in low- and high-prolactin groups (McDiarmid et al., 2000).
In the 1999 surveillance, there were no statistically significant differences in mean FSH, LH, prolactin, and testosterone concentrations or thyroid measures between low and high groups. Of the 44 sperm samples included in the analysis, three were designated subnormal—possessing below normal values of at least three of the five characteristics as defined by World Health Organization standards. The high-urinary-uranium groups had more abnormal total sperm counts (583.5 ± 106.1 vs 286.6 ± 44.8), total progressive sperm counts (220.9 ± 44.0 vs 108.2 ± 19.2), and total rapid progressive sperm counts (155.5 ± 31.1 vs 81.3 ± 15.4) that were statistically significant (p = 0.02, 0.03, and 0.04, respectively), results not previously seen in this group (McDiarmid et al., 2001). In 2001, overall neuroendocrine function was normal, but mean free thyroxine was higher in