Inhalation and ingestion intakes with associated dose estimates for level II and level III personnel using Capstone study data

Depleted uranium (DU) intake rates and subsequent dose rates were estimated for personnel entering armored combat vehicles perforated with DU penetrators (level II and level III personnel) using data generated during the Capstone DU Aerosol Study. Inhalation intake rates and associated dose rates were estimated from cascade impactors worn by sample recovery personnel and from cascade impactors that served as area monitors. Ingestion intake rates and associated dose rates were estimated from cotton gloves worn by sample recovery personnel and from wipe-tests samples from the interior of vehicles perforated with large-caliber DU munitions. The mean DU inhalation intake rate for level II personnel ranged from 0.447 mg h(-1) based on breathing zone monitor data (in and around a perforated vehicle) to 14.5 mg h(-1) based on area monitor data (in a perforated vehicle). The mean DU ingestion intake rate for level II ranged from 4.8 mg h(-1) to 38.9 mg h(-1) based on the wipe-tests data including surface-to-glove transfer factors derived from the Capstone data. Based on glove contamination data, the mean DU ingestion intake rates for level II and level III personnel were 10.6 mg h(-1) and 1.78 mg h(-1), respectively. Effective dose rates and peak kidney uranium concentration rates were calculated based on the intake rates. The peak kidney uranium concentration rate cannot be multiplied by the total exposure duration when multiple intakes occur because uranium will clear from the kidney between the exposures.

Capstone depleted uranium aerosol biokinetics, concentrations, and doses

One of the principal goals of the Capstone Depleted Uranium (DU) Aerosol Study was to quantify and characterize DU aerosols generated inside armored vehicles by perforation with a DU penetrator. This study consequently produced a database in which the DU aerosol source terms were specified both physically and chemically for a variety of penetrator-impact geometries and conditions. These source terms were used to calculate radiation doses and uranium concentrations for various scenarios as part of the Capstone Human Health Risk Assessment (HHRA). This paper describes the scenario-related biokinetics of uranium, and summarizes intakes, chemical concentrations to the organs, and E(50) and HT(50) for organs and tissues based on exposure scenarios for personnel in vehicles at the time of perforation as well as for first responders. For a given exposure scenario (duration time and breathing rates), the range of DU intakes among the target vehicles and shots was not large, about a factor of 10, with the lowest being for a ventilated operational Abrams tank and the highest being for an unventilated Abrams with DU penetrator perforating DU armor. The ranges of committed effective doses were more scenario-dependent than were intakes. For example, the largest range, a factor of 20, was shown for scenario A, a 1 min exposure, whereas, the range was only a factor of two for the first-responder scenario (E). In general, the committed effective doses were found to be in the tens of mSv. The risks ascribed to these doses are discussed separately.

Efficacy of oral and intraperitoneal administration of CBMIDA for removing uranium in rats after parenteral injections of depleted uranium

The efficacy of oral administration of the chelating agent catechol-3,6-bis(methyleiminodiacetic acid) (CBMIDA) for removing uranium from rats after intraperitoneal (i.p.) and intramuscular (i.m.) injections of depleted uranium (DU) was examined and the results with those by the i.p. injection of CBMIDA were compared. In Experiment 1, after a single i.p. injection of 8 mg kg(-1) of DU of rat's body weight, 35 8-week-old male rats were divided into seven groups consisting of five rats each. Three groups were administered with CBMIDA 240, 720 or 1200 mg kg(-1) of rat's body weight orally once a day, and three other groups received an i.p. injection of 240, 480 or 720 mg kg(-1) CBMIDA for 3 d, starting 30 min after DU injection on the first day. One DU group received no CBMIDA. The remaining five intact rats were used as a control group. Rats were killed 6 d after DU injection. In Experiment 2, the 35 male rats that received a single i.m. injection of 8 mg kg(-1) DU were divided into seven groups, and the rats of each group received the same doses of CBMIDA on the same schedules of treatment as those described in Experiment 1. The results obtained in Experiment 1 indicated that orally administered CBMIDA significantly increased the excretion of uranium at doses of 720 and 1200 mg kg(-1) and decreased uranium concentrations, particularly in the kidney, at all the doses tested, and the effects were almost equal to those of the i.p. injection. The lack of increases in creatinine and blood urea nitrogen in serum indicated that CBMIDA is efficacious in preventing the renal dysfunction caused by uranium. In Experiment 2, oral administration of CBMIDA significantly increased uranium excretion and significantly decreased uranium concentrations, particularly in the kidneys, at all the doses tested, and the effects were almost equal to those of the i.p. injection. However, these effects of CBMIDA on the i.m.-injected DU were lower than those of the i.p.-injected DU in Experiment 1. These results indicated that oral administration of CBMIDA has almost the same efficacy as that administered by the parenteral route. Additional study is necessary to obtain satisfactory effects for the clinical use of CBMIDA, particularly for wounds contaminated accidentally with uranium.

Comparison of observed body retention of uranium in natural condition in an average Indian adult with the values predicted by the ICRP biokinetic model

The daily intake of natural uranium and its contents in the lungs, skeleton, liver and kidney of an Indian adult population group was estimated using radiochemical neutron activation analysis (RNAA). These data on daily intake (through inhalation and ingestion) were used to compute the uranium contents in the lungs and other systemic organs such as the skeleton, liver and kidney, using the new human respiratory tract model (HRTM) and the new biokinetic model of uranium. The theoretically computed uranium contents in the lungs, skeleton, liver and kidney of an average Indian adult are 1.16, 1.96, 0.07 and 0.04 microg, respectively, and the corresponding experimentally measured values are 1.23 (1.76), 2.92 (2.5), 0.07 (1.76) and 0.19 (1.47) microg in an urban population group living in Mumbai. The values given in parentheses are geometric standard deviation (GSD). It is seen that the measured uranium contents in the lungs, skeleton and liver agree very well with the corresponding computed values, but the measured value for the kidney is observed to be on the higher side of the computed value. However, in view of many uncertainties, the overall agreement between the measured and the computed values can be considered to be good. Therefore, the result from this study can be taken as a validation of the new biokinetic model of uranium in Indian conditions.

Proposed standards for acute exposure to low enrichment uranium for compliance with 10 CFR 70.61

Title 10, Code of Federal Regulations Part 70, puts forth requirements for licensure of special nuclear material including specific risk criteria for acute intakes based on biological effects. Standards for acute oral and inhalation intakes of soluble low enrichment are proposed for the three levels of biological effects given in the regulations. These levels were developed largely from available human data and have a large measure of conservatism. The proposed threshold for life endangerment was 500 mg for acute inhalation intakes and 2,500 mg for acute ingestion intakes. Acute intakes of 1,400 mg for ingestion and 100 mg for inhalation are proposed as thresholds for irreversible or serious long lasting health effects. For minor transient health effects, the proposed levels are 410 and 30 mg, respectively, for acute ingestion and inhalation intakes. For acute intakes below these levels, no demonstrable toxicological effects are anticipated.

Evaluation of uranium incorporation from contaminated areas using teeth as bioindicators--a case study

The Southwest region of the Bahia state in Brazil hosts the largest uranium reserve of the country (100 kton in uranium, only), plus the cities of Caetité, Lagoa Real and Igaporã. In this work, aim was at the investigation of uranium burdens on residents of these cities by using teeth as bioindicators, as a contribution for possible radiation protection measures. Thus, a total of 41 human teeth were collected, plus 50 from an allegedly uranium free area (the control region). Concentrations of uranium in teeth from residents of 5- to 87-y old were determined by means of a high-resolution inductively coupled plasma mass spectrometer (ICP-MS). The highest uranium concentration in teeth was measured from samples belonging to residents of Caetité (median equal to 16 ppb). Assuming that the uranium concentrations in teeth and bones are similar within 10-20% (for children and young adults), it concluded that uranium body levels in residents of Caetité are at least one order of magnitude higher than the worldwide average. This finding led to conclude that daily ingestion of uranium, from food and water, is equally high.

Pro-oxidant effects in the brain of rats concurrently exposed to uranium and stress

Metal toxicity may be associated with increased rates of reactive oxygen species (ROS) generation within the central nervous system (CNS). Although the kidney is the main target organ for uranium (U) toxicity, this metal can also accumulate in brain. In this study, we investigated the modifications on endogenous antioxidant capacity and oxidative damage in several areas of the brain of U-exposed rats. Eight groups of adult male rats received uranyl acetate dihydrate (UAD) in the drinking water at 0, 10, 20, and 40 mg/kg/day for 3 months. Animals in four groups were concurrently subjected to restraint stress during 2h/day throughout the study. At the end of the experimental period, cortex, hippocampus and cerebellum were removed and processed to examine the following stress markers: reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as U concentrations. The results show that U significantly accumulated in hippocampus, cerebellum and cortex after 3 months of exposure. Moreover, UAD exposure promoted oxidative stress in these cerebral tissues. In cortex and cerebellum, TBARS levels were positively correlated with the U content, while in cerebellum GSSG and GSH levels were positively and negatively correlated, respectively, with U concentrations. In hippocampus, CAT and SOD activities were positively correlated with U concentration. The present results suggest that chronic oral exposure to UAD can cause progressive perturbations on physiological brain levels of oxidative stress markers. Although at the current UAD doses restraint scarcely showed additional adverse effects, its potential influence should not be underrated.

Incorporation and distribution of uranium in rats after a contamination on intact or wounded skin

Uranium uptake can occur accidentally by inhalation, ingestion, injection, or absorption through intact or wounded skin. Intact or wounded skin routes of absorption of uranium have received little attention. The aims of our work were (1) to evaluate the influence of the type of wound contamination on the short term distribution and excretion of uranium in rats and (2) to generate data to assess the time available to treat contamination of intact or wounded skin before significant uptake of uranium occurs. Biokinetic data presented in the present paper are based on an in vivo rat model. This study shows that a significant uptake of a uranyl nitrate solution through intact skin can occur within the first 6 h of exposure. Absorption of a uranyl nitrate solution through excoriated skin is significant after only 30 min of exposure. After a 24-h exposure, uranium uptake through intact skin and excoriated skin represents about 0.4% and 38% of the initial deposit of uranium, respectively. Contaminated serious chemical skin burns induced by HNO3 or NaOH are paradoxically less important in terms of uranium uptake risk because 99% of the incorporated uranium remains trapped at the wound site and its incorporation is delayed for at least 6 h after the beginning of contamination. These results confirm that the biokinetics of a given physicochemical form of uranium incorporated after wound contamination depend largely on the physiological evolution of the considered wound. Each type of wound, with its corresponding biokinetics of a uranium species, is a particular case.

Chronic Exposure to Uranium Leads to Iron Accumulation in Rat Kidney Cells

After it is incorporated into the body, uranium accumulates in bone and kidney and is a nephrotoxin. Although acute or short-term uranium exposures are well documented, there is a lack of information about the effects of chronic exposure to low levels of uranium on both occupationally exposed people and the general public. The objective of this study was to identify the distribution and chemical form of uranium in kidneys of rats chronically exposed to uranium in drinking water (40 mg uranium liter(-1)). Rats were killed humanely 6, 9, 12 and 18 months after the beginning of exposure. Kidneys were dissected out and prepared for optical and electron microscope analysis and energy dispersive X-ray (XEDS) or electron energy loss spectrometry (EELS). Microscopic analysis showed that proximal tubule cells from contaminated rats had increased numbers of vesicles containing dense granular inclusions. These inclusions were composed of clusters of small granules and increased in number with the exposure duration. Using XEDS and EELS, these characteristic granules were identified as iron oxides. Uranium was found to be present as a trace element but was never associated with the iron granules. These results suggested that the mechanisms of iron homeostasis in kidney could be affected by chronic uranium exposure.

Bioaccumulation, oxidative stress, and neurotoxicity in Danio rerio exposed to different isotopic compositions of uranium

Experiments were carried out on adult male zebrafish (Danio rerio) to assess early changes induced by waterborne exposure to different isotopic compositions of uranium (depleted uranium associated or not with 233U). Oxidative stress and neurotoxicity were selected as effect endpoints to characterize uranium chemo- and radiotoxicity. Catalase, glutathione peroxidase, and superoxide dismutase activities and total glutathione content of hepatic extracts, as well as brain acetylcholinesterase activity and uranium bioaccumulation, were measured. Oxidative stress induced by uranium exposure led to decreases in superoxide dismutase and catalase activity levels as well as total glutathione content in liver extracts. These perturbations were significantly more marked in 233U-exposed fish. Furthermore, significant increase in acetylcholinesterase activity was observed in brain extracts at the same level, whatever the isotopic composition of uranium.

Metal-phytoplankton interactions: modeling the effect of competing ions (H+, Ca2+, and Mg2+) on uranium uptake

The influence of pH and hardness cation concentrations on uranium uptake by a green alga, Chlamydomonas reinhardtii, was investigated through short-term exposure experiments. Uranium uptake at pH 5 and at pH 7 was measured over a large concentration range (0.020-2.0 microM 233U), and the effects of hardness cations were studied over environmentally pertinent concentration ranges (approximately 0.05-2 mM) at a constant uranium concentration (0.25 microM). Calcium and magnesium inhibited uranyl uptake, but the influence of pH was more complex than anticipated. The equilibrium biotic ligand paradigm of metal bioavailability predicts that two distinct phenomena of antipathetic effect will influence uranium availability as pH is varied. Increasing pH reduces the concentration of protons, thus reducing competition for the physiologically active sites, whereas the concomitant complexation by carbonates and hydroxides reduces the free uranyl activity. Maximum uranium uptake rates observed at pH 7, however, were far greater than those observed at pH 5, suggesting a noncompetitive inhibition of metal transport by protons. Modeling on the basis of our results strongly suggests that cells grown and exposed at pH 7 have either a greater internalization rate of uranyl or a higher number of transport sites compared with cells grown and exposed at pH 5. We thus conclude that the simple proton-metal competition described by the biotic ligand model cannot successfully depict uranium-algae interactions. The development of an appropriate model incorporating the influence of protons to predict metal uptake and toxicity will be more challenging than anticipated.

c-Type cytochrome-dependent formation of U(IV) nanoparticles by Shewanella oneidensis

Modern approaches for bioremediation of radionuclide contaminated environments are based on the ability of microorganisms to effectively catalyze changes in the oxidation states of metals that in turn influence their solubility. Although microbial metal reduction has been identified as an effective means for immobilizing highly-soluble uranium(VI) complexes in situ, the biomolecular mechanisms of U(VI) reduction are not well understood. Here, we show that c-type cytochromes of a dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1, are essential for the reduction of U(VI) and formation of extracellular UO(2) nanoparticles. In particular, the outer membrane (OM) decaheme cytochrome MtrC (metal reduction), previously implicated in Mn(IV) and Fe(III) reduction, directly transferred electrons to U(VI). Additionally, deletions of mtrC and/or omcA significantly affected the in vivo U(VI) reduction rate relative to wild-type MR-1. Similar to the wild-type, the mutants accumulated UO(2) nanoparticles extracellularly to high densities in association with an extracellular polymeric substance (EPS). In wild-type cells, this UO(2)-EPS matrix exhibited glycocalyx-like properties and contained multiple elements of the OM, polysaccharide, and heme-containing proteins. Using a novel combination of methods including synchrotron-based X-ray fluorescence microscopy and high-resolution immune-electron microscopy, we demonstrate a close association of the extracellular UO(2) nanoparticles with MtrC and OmcA (outer membrane cytochrome). This is the first study to our knowledge to directly localize the OM-associated cytochromes with EPS, which contains biogenic UO(2) nanoparticles. In the environment, such association of UO(2) nanoparticles with biopolymers may exert a strong influence on subsequent behavior including susceptibility to oxidation by O(2) or transport in soils and sediments.

Depleted uranium: all the questions about DU and Gulf War syndrome are not yet answered

For 15 years, the debate about depleted uranium (DU) and its detrimental effects on the health of veterans of the Gulf War of 1991, on the Iraqi people and military (and subsequently on the people of Kosovo, Afghanistan, and Iraq during the second war) has remained unresolved. Meanwhile, the number of Gulf War veterans who have developed the so-called Gulf War syndrome has risen to about one-third of the 800,000 U.S. forces deployed, and unknown proportions of those involved in the subsequent wars. Uncounted civilians and personnel of other nations that fought in Iraq and other wars since 1991 have also been afflicted. The veterans have suffered from multiple serious physiological disorders and have received little or no official recognition, medical relief, or compensation. We need to take another look at this issue, using a holistic and interactive model for the toxic matrix of exposures, identifying the major roadblocks to resolving the scientific questions, and finding appropriate medical and political responses. This commentary is such an attempt.

Can we predict uranium bioavailability based on soil parameters? Part 1: effect of soil parameters on soil solution uranium concentration

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for (238)U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K(d), L kg(-1)) and the organic matter content (R(2)=0.70) and amorphous Fe content (R(2)=0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH=6, log(K(d)) was linearly related with pH [log(K(d))=-1.18 pH+10.8, R(2)=0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex.

Percutaneous penetration of uranium in rats after a contamination on intact or wounded skin

The aim of this work is to assess in vivo in a hairless rat model, the percutaneous diffusion of uranium through intact or wounded rat skin. Six types of wounds were simulated by excoriation and burns with 10 N HF, 2, 5 and 14 N HNO3 and 10 N NaOH on anaesthetised hairless rats. Percutaneous penetration through wounded skin towards blood and subsequent urinary excretion of uranium was followed in vivo during 24 h. The influence of the physicochemical form (solution or powder) of uranyl nitrate (UN) on its percutaneous diffusion was also investigated. UN, even as a powder, can diffuse through intact skin. The presence of uranium in blood is more persistent and its urinary elimination is slower after an HF burn than after an HNO3 burn. Excoriation increases dramatically percutaneous absorption of UN. Thus, percutaneous diffusion of UN is largely dependent on skin barrier integrity with a particular importance of stratum corneum.

Effects of pH on du intake and removal by CBMIDA and EHBP

The effects of pH on deleted uranium (DU) and DU removal by chelating agents, catechol-3,6-bis(methyleneiminodiacetic acid) (CBMIDA) and ethane-1-hydroxy-1,1-bisphoshonate (EHBP) in rats were examined. Ninety male Wistar rats, 8 wk old, were divided into six groups of 15 rats. Rats of five groups were each preinjected intraperitoneally with 8 mg kg(-1) DU in pH 1, 3, 5, 7, and 10 solutions. In each pH group, five rats were injected intraperitoneally with 240 mg kg(-1) CBMIDA, and the other five with 10 mg kg(-1) EHBP; the remaining five were used as the corresponding group with no chelating agent. One group was kept as the control (no injected DU) group, which consisted of five intact, five with CBMIDA, and five with EHBP administration. Chelating agents were administered for 3 d. Rats were injected with the DU 30 min prior to treatment with chelating agents on the first day. The gathered data indicated that the DU toxicity varied according to differences in pH; in addition, at pH 7, when varied DU-complexes formed, the DU toxicity including renal dysfunction increased, and the DU removal effects of chelating agents were not obtained. Both CBMIDA and EHBP were effective in excreting DU, reducing DU concentrations in organs, and preventing DU-induced toxicity, and CBMIDA was superior to EHBP, particularly in the prevention of renal dysfunction. These results indicate that the excretion and distribution of soluble DU changes and the removal effects of chelating agents according to pH differs, indicating that the treatment with chelating agent should begin in the DU-contaminated person as early as possible after an accident.

Risk assessment after internal exposure to black sand from Camargue: uptake and prospective dose calculation

Some beaches in the south of France present high levels of natural radioactivity mainly due to thorium (Th) and uranium (U) present in the sand. Risk assessment after internal exposure of members of the public by either inhalation or ingestion of black sand of Camargue was performed. This evaluation required some information on the human bioavailability of U and Th from this sand. In vitro assays to determine the solubility of U, Th and their progeny were performed either in simulated lung fluid, with the inhalable fraction of sand, or in both simulated gastric and intestinal fluids with a sample of the whole sand. The experimental data show that the bioavailability of these radionuclides from Camargue sand is low in the conditions of the study. Prospective dose assessment for both routes of intake show low risk after internal exposure to this sand.

Can we predict uranium bioavailability based on soil parameters? Part 2: soil solution uranium concentration is not a good bioavailability index

The present study aimed to quantify the influence of soil parameters on uranium uptake by ryegrass. Ryegrass was established on eighteen distinct soils, spiked with (238)U. Uranium soil-to-plant transfer factors (TF) ranged from 0.0003 to 0.0340kgkg(-1). There was no significant relation between the U soil-to-plant transfer (or total U uptake or flux) and the uranium concentration in the soil solution or any other soil factor measured, nor with the U recovered following selective soil extractions. Multiple linear regression analysis resulted in a significant though complex model explaining up to 99% of variation in TF. The influence of uranium speciation on uranium uptake observed was featured: UO(2)(+2), uranyl carbonate complexes and UO(2)PO(4)(-) seem the U species being preferentially taken up by the roots and transferred to the shoots. Improved correlations were obtained when relating the uranium TF with the summed soil solution concentrations of mentioned uranium species.

Assessment of occupational exposure to uranium by indirect methods needs information on natural background variations

Urine monitoring is the preferred method to determine exposure to soluble compounds of uranium in workplaces. The interpretation of uranium contents in workers bioassay samples requires knowledge on uranium excretion and its dependence on intake by diet. Exceptionally high concentrations of natural uranium in private drinking water sources have been measured in the granite areas of Southern Finland. Consequently, high concentrations of natural uranium have been observed in the urine and hair samples of people using water from their own drilled wells. Natural uranium content in urine and hair samples of family members, who use uranium-rich household water, have been analyzed by using ICP-MS. The uranium concentrations both in urine and hair samples of the study subjects were significantly higher than the world-wide average values. In addition, gammaspectrometric methods have been tested for determining uranium in hair samples. This method can be used only for samples with highly elevated uranium concentrations.

MDA improvement technique for lung counter measurements of uranium workers

A practical and simple method was employed to improve the minimum detectable activity (MDA) for lung counting measurements by summing several accumulated spectra. The method was checked for natural uranium, which produces peaks due to photon energies of 63.3, 92.6 and 185.7 keV. By combining nine measurements, an overall improvement of the MDA by a factor of about 3 was achieved. Uranium contamination levels lower than the MDA of a single spectrum could be detected with acceptable accuracy when analyzing the sum spectra. Specific results are given for four workers occupationally exposed to natural uranium.

Inositol hexaphosphate: a potential chelating agent for uranium

Chelation therapy is an optimal method to reduce the radionuclide-related risks. In the case of uranium incorporation, the treatment of choice is so far i.v infusion of a 1.4% sodium bicarbonate solution, but the efficacy has been proved to be not very high. In this study, we examine the efficacy of some substances: bicarbonate, citrate, diethylenetriamine pentaacetic acid (DTPA), ethidronate (EHBP) and inositol hexaphosphate (phytic acid) to chelate uranium using a test developed by Braun et al. Different concentrations of phytic acid, an abundant component of plant seeds that is widely distributed in animal cells and tissues in substantial levels, were tested and compared to the same concentrations of sodium citrate, bicarbonate, EHBP and DTPA. The results showed a strong affinity of inositol hexaphosphate for uranium, suggesting that it could be an effective chelating agent for uranium in vivo.

Dose assessment for inhalation intakes in complex, energetic environments: experience from the US Capstone study

Because of the lack of existing information needed to evaluate the risks from inhalation exposures to depleted uranium (DU) aerosols of US soldiers during the 1991 Persian Gulf War, the US Department of Defense funded an experimental study to measure the characteristics of DU aerosols created when Abrams tanks and Bradley fighting vehicles are struck with large-caliber DU penetrators, and a dose and risk assessment for individuals present in such vehicles. This paper describes some of the difficulties experienced in dose assessment modelling of the very complex DU aerosols created in the Capstone studies, e.g. high concentrations, heterogeneous aerosol properties, non-lognormal particle size distributions, triphasic in vitro dissolution and rapid time-varying functions of both DU air concentration and particle size. The approaches used to solve these problems along with example results are presented.

Heterogeneous accumulation of uranium in the brain of rats

Recent reports suggest that uranium can accumulate not only in known target organs, that is, kidneys or bones, but also in others such as central nervous system. In the present work, the accumulation of uranium in the brain of rats was studied after repeated exposure by inhalation, chronic exposure by ingestion and acute exposure by injection. For each route of administration, the amount of uranium entering the brain was low. The results showed different accumulation in the brain areas according to the route of intake. Injection gave a rather homogeneous distribution in the different brain areas, whereas both inhalation and ingestion yielded heterogeneous but specific accumulation. These differences in distribution suggest the operation of different mechanisms of delivery of uranium to the brain tissues.

A review of depleted uranium biological effects: in vitro and in vivo studies

The use of depleted uranium in armor-penetrating munitions remains a source of controversy because of the numerous unanswered questions about its long-term health effects. Although no conclusive epidemiologic data have correlated DU exposure to specific health effects, studies using cultured cells and laboratory rodents continue to suggest the possibility of leukemogenic, genetic, reproductive, and neurological effects from chronic exposure. Until issues of concern are resolved with further research, the use of depleted uranium by the military will continue to be controversial.

Development and application of anthropomorphic voxel phantom of the head for in vivo measurement

The in vivo measurement of the activity deposited in the skeleton is a very useful source of information on human internal contaminations with transuranic elements, e.g. americium 241, especially for long time periods after intake. Measurements are performed on the skull or the larger joints such as the knee or elbow. The paper deals with the construction of an anthropomorphic numerical phantom based on CT scans, its potential for calibration and the estimation of the uncertainties of the detection system. The density of bones, activity distribution and position of the detectors were changed in individual simulations in order to estimate their effects on the result of the measurement. The results from simulations with the numerical phantom were compared with the results of physical phantoms.