Uranium exposure

Animal studies indicate that the primary toxic effect of uranium exposure is on the kidney, with particular damage to the proximal tubules. Functionally, this may result in increased excretion of glucose and amino acids. Structurally the necrosis of tubular epithelium leads to formation of cellular casts in the urine. If exposure is insufficient to cause death from renal failure, the mbular lesion is reversible with epithelial regeneration. Although bone is the other major site of deposition, there is no evidence of toxic or radiocarcinogenic effects to bone or bone marrow from experimental studies. ... 

A significantly (p<0.05) increased incidence of malignancies in the lymphatic and hematopoietic tissues of uranium mill workers (cohort of 662 males) was found by Archer et al. (1973). The radioactivity in the tracheobronchial lymph nodes of the workers was found to be primarily the result of alpha emissions from thorium-230 and not from uranium-234 or uranium-238. Consequently, the authors suggested that the increased incidence of malignancies may have been a result of thorium-230 exposure and not uranium exposure. Exposure levels of thorium were not reported therefore, the results of the study are not reported on Table 2-1 or plotted in Figure 2-1. 

Generation of nitric oxide (NO) and evaluation of the central cholinergic system of male Sprague-Dawley rats following uranium exposure have also been studied... 

Briner, W., Murray, J. (2005). Effects of short-term and long-term depleted uranium exposure on open-field behavior and brain lipid oxidation in rats. Neurotoxicol. Teratol. 27 135 4. 

Squibb, K.S., McDiarmid, M.A. (2006). Depleted uranium exposure and health effects in Gulf War veterans. Philos. Trans. R. Soc. Lend. B Biol. Set 361 639-48. 

Like adults, children are exposed to small amounts of uranium in air, food, and drinking water. However, no cases have been reported where exposure to uranium is known to have caused health effects in children. It is possible that if children were exposed to very high amounts of uranium they might have damage to their kidneys like that seen in adults. We do not know whether children differ from adults in their susceptibility to health effects from uranium exposure. 

In chronic-duration experiments, inhalation of 2 mg U/m as uranyl nitrate hexahydrate for 6 hours a day, 5.5 days a week for 92-100 weeks resulted in 1% mortality in rats (Stokinger et al. 1953). This is not an unusual mortality rate for rats, so it is unlikely that these deaths can be attributed to uranium exposure. Dogs exposed to uranyl nitrate hexahydrate for 2 years suffered 4% mortality (Stokinger et al. 1953). 

Human studies that assessed damage to cellular immune components following inhalation exposure to uranium found no clear evidence of an immunotoxic potential for uranium. No association was found between the uranium exposure and the development of abnormal leukocytes in workers employed for 12-18 years at a nuclear fuels production facility (Cragle et al. 1988). Increases in the number of fatal malignant disease of the lymphatic and hematopoietic tissue reported among uranium mill workers may have been caused by other carcinogens in the work environment such as °Th. The authors of this report estimated that the workers were exposed to 8-5,100 mg/m (median 110 mg/m ) uranium mill dust, which contains °Th as a natural component (Archer et al. 1973b). 

In the available animal studies, the existing data provide evidence that uranium exposure does not cause detectable damage to the musculoskeletal system. Histopathological examination of muscle after... 

Ocular Effects. No ocular effects attributable to uranium exposure were reported in the available human studies. In animal studies, dogs exposed to 13 mg U/m as uranium hexafluoride for 30 days exhibited encrusted eyes and conjunctivitis prior to death. However, these signs were considered nonspecific indications of poor health by the investigators of the study (Spiegl 1949). Consequently, no ocular effects are expected from human exposure to uranium compounds. 

Specific information is not available on whether children are more susceptible than adults to the effects of uranium. No reports were located describing toxicity in children as the result of uranium exposure. It is probable, however, that if exposure levels were high enough, signs of renal toxicity would be observed similar to those seen in adults exposed accidentally (Zhao and Zhao 1990) or intentionally (Pavlaikis 1996). No reports are available of studies where toxic responses of young animals to uranium were directly compared to those of adults. 

Methods for Reducing Toxic Effects. Uranium forms complexes with the bicarbonate ion (Cooper et al. 1982) and has been administered prophylactically after uranium exposure (Fisher et al. 1991). Bicarbonate can alkalize the blood to a degree that facilitates the excretion of uranium via the kidneys. This in turn, can prevent uptake by and deposition in critical tissues (kidney, bone). Chelation has been tested in animals and found to have a limited potential, though possibly valuable, role in reducing acute uranium toxicity. Further research is needed to validate, refute, or refine method(s) for reducing the toxic effects of uranium compounds. No verified methods for reducing the toxic effects of long-term exposure to uranium are currently available. 

Keogh J Department of Veterans Affairs Medical Center, Baltimore, MD Assessment of depleted uranium exposure during the Persian gulf war. Department of Veterans Affairs Research and Development... 

As for adults, the potential for uranium exposure is greater for children who consume foods grown in areas with elevated concentrations of uranium in the soil and for children with elevated concentrations of uranium in their drinking water (EPA 1985 NCRP 1984a). Other home exposures are unlikely since no household products or products used in crafts, hobbies or cottage industries contain significant amounts of uranium, except in cases where uranium-bearing rocks are used in and around the home for decorative, collection, or construction purposes (ATSDR 1997)... 

Uranium exposure to children from parents work clothes, skin, hair, tools, or other objects from the worlq)lace is possible if the parent uses uranium at work. However, in a comprehensive review of incidents of home contamination by workers (NIOSH 1997), no cases of uranium contamination were described. 

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