Lungs uranium toxicity

Plutonium has a much shorter half-life than uranium (24.000 years for Pu-239 6,500 years for Pu-240). Plutonium is most toxic if it is inhaled. The radioactive decay that plutonium undergoes (alpha decay) is of little external consequence, since the alpha particles are blocked by human skin and travel only a few inches. If inhaled, however, the soft tissue of the lungs will suffer an internal dose of radiation. Particles may also enter the blood stream and irradiate other parts of the body. The safest way to handle plutonium is in its plutonium dioxide (PuOj) form because PuOj is virtually insoluble inside the human body, gi eatly reducing the risk of internal contamination. 

The histological types of lung cancer seen to excess in uranium miners reflect those in the population at large (Masse, 1984). These occur almost entirely in bronchial airways. Approximately 207 are adenocarcinomas which occur in peripheral bronchioles (Spencer, 1977) where there are no basal cells. Squamous cell cancers predominate in miners exposed early in life to relatively low concentrations of radon daughters (Saccomanno et aJL., 1982). These are considered likely to arise from the secretory small mucous granular cells which undergo cell division and extend to the epithelial surface (Masse, personal communication). Division of these cells is accelerated after irritation by toxicants such as cigarette smoke or infectious diseases (Trump et a L., 1978). 

The hazard from inhaled uranium aerosols, or any noxious agent, is determined by the likelihood that the agent will reach the site of its toxic action. Two main factors that influence the degree of hazard from toxic airborne particles are the site of deposition in the respiratory tract of the particles and the fate of the particles within the lungs. The deposition site within the lungs depends mainly on the particle size of the inhaled aerosol, while the subsequent fate of the particle depends mainly on the physical and chemical properties of the inhaled particles and the physiological status of the lungs. 

Deaths occurred after accidental releases of uranium hexafluoride at uranium-processing facilities in 1944 and 1986, but these deaths were not attributed to the uranium component of this compound (Kathren and Moore 1986 Moore and Kathren 1985 USNRC 1986). These releases resulted in the generation of concentrated aerosols of highly toxic hydrofluoric acid and uranyl fluoride. In the 1944 incident exposure time was estimated to be only 17 seconds, deaths occurred in 2 of 20 workers within an hour and were attributed to severe chemical burns of the lungs. In the 1986 incident, 1 of 23 workers died from massive pulmonary edema, indicating that inhalation of hydrofluoric acid was responsible for death. Estimated airborne concentrations were 20 mg uranium hexafluoride/m for a 1-minute exposure and 120 mg uranium hexafluoride/m for a 60-minute exposure (15.2 and 91 mg U/m, respectively). 

Because particles containing insoluble uranium compounds can reside in the lung for years, it is likely that radiotoxicity as well as chemical toxicity can result from inhalation exposure to highly enriched uranium compounds. Radiation effects on tissues from the alveolar regions of the lungs were examined in Albino HMT (Fischer 344) male rats exposed, nose-only, for 100 minutes to an aerosol of to 92.8% U-enriched uranium dioxide with a concentration of 2,273 nCi/m (84.1 kBq/m ) to 5,458 nCi/m ... 

The model was used to estimate uranium intakes uranium burdens in the lungs, kidneys, and bones and effective dose equivalent for each worker in the accident. Initial intakes of workers involved in the accident ranged from 470-24,000 pg uranium. The model estimated the maximum kidney concentrations in the workers as ranging from 0.048 to 2.5 pg U/g kidney tissue, renal toxicity was not observed in any of the workers (Fisher et al. 1990, 1991). 

In addition, the sequestration patterns of the different uranium compounds are important determinants for the target organ chemical and radiological toxicities of these compounds. The site of deposition for the soluble uranium compounds (uranyl nitrate, uranium tetrachloride, uranium hexafluoride) is the bone, while the insoluble compounds (uranium hexafluoride, uranium dioxide) accumulate in the lungs and lymph nodes (Stokinger 1953). 

The dual modes of uranium chemical and radiological toxicity are not usually separately identifiable by end point. The renal and respiratory effects from exposure of humans and animals to uranium are usually attributed to the chemical properties of uranium, while the theoretically potential excess cancers are usually attributed to the radiation properties of this substance. Although the net effects on the lungs and kidneys have been suggested to be a cooperative action of the chemical and radiation properties, with a complementary mechanism of action, this relationship has not been demonstrated experimentally (Ballou... 

Saccomanno G, Thun MJ, Baker DB, et al. 1982. The contribution of uranium miners to lung cancer histogenesis renal toxicity in uranium mill workers. Cancer Research 82 43-52. 

Caution Uranium and its salts ate highly toxic. Dermati -tis renal damage, acute necrotic arterial lesions, death may occur. Radiation hazard from inhalation of fine particles of approx Ip. n ol particles in Lung may be long-term carcinogenic hazard. See L. T. Fair hall Industrial Toxicology (Hafner. New York, 2nd ed., 1969) pp 129-13L... 

In the mid-1960s, several other MSS toxicants had their brief moment of infamy, for example, °Po, NO2, CO, Ni. In their comparison of lung cancer incidence in uranium miners exposed to °Po vs. cigarette smokers exposed to MSS opo, Harley et al. (75) questioned the significance of °Po in tobacco-induced lung cancer. Concern over NO2 diminished with the demonstration that over 95% of the NO, in MSS was... 

The greatest health risk from large intakes of uranium is toxic damage to the kidneys, because, in addition to being weakly radioactive, uranium is a toxic metal. Uranium expo.sure also increases your risk of getting cancer due to its radioactivity. Since uranium tends to concentrate in specific locations iti the body, risk of cancer of the bone, liver cancer, and blood diseases (such as leukemia) are increased. Inhaled uranium increases the risk of lung cancer. 

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