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PubMed1999

Chemical toxicity of some actinides and lanthanides towards alveolar macrophages: an in vitro study.

PURPOSE: To compare the toxicity of lanthanides (cerium, gadolinium) with actinides (thorium, neptunium, uranium) added in soluble form to rat alveolar macrophage cultures. MATERIALS AND METHODS: The metals were added 1 day after seeding alveolar macrophages extracted by pulmonary lavage, and the metal toxicity was scored 3 days later. Cell death was measured after vital staining to distinguish between apoptosis and necrosis; relative cell density was also quantified. The physico-chemical form of the metals in the culture medium was characterized using filtration and radioactive measurements. RESULTS: Except for thorium, induction of cell death was observed for all the elements studied and the death mechanism involved was apoptosis. Graduated toxicity was observed from uranium to neptunium, cerium and gadolinium, in the range of concentration from 10(-3)-10(-6) M. From pilot experiments, it was hypothesized that soluble compounds were mainly involved in lanthanide toxicity, whereas insoluble forms were mainly involved in actinide toxicity. CONCLUSION: This study demonstrates that the toxicity of neptunium and uranium was concomitant with the presence of insoluble forms in the culture medium. Further studies are needed to characterize the cell death mechanisms involved and the potential synergistic effects of chemical toxicity and irradiation.

Actinoid Series Elements↗
PubMed2001

Solubility of airborne uranium compounds at the Fernald Environmental Management Project.

The in vitro solubility of airborne uranium dusts collected at a former uranium processing facility now undergoing safe shutdown, decontamination, and dismantling was evaluated by immersing air filters from high volume samplers in simulated lung fluid and measuring the 238U in sequential dissolution fractions using specific radiochemical analysis for uranium. X rays and photons from the decay of uranium and thorium remaining on the filter after each dissolution period were also directly measured using a planar germanium detector as a means for rapidly evaluating the solubility of the uranium-bearing dusts. Results of these analyses demonstrate that two distinct types of uranium-bearing dusts were collected on the filters depending upon the location of the air samplers. The first material exhibited a dissolution half-time much less than 1 d and was most likely UO3. The dissolution rate of the second material, which was most likely U3O8, exhibited two components. Approximately one-third of this material dissolved with a half time much less than 1 d. The remaining two-thirds of the material dissolved with half times between 230 +/- 16 d and 1,350 +/- 202 d. The dissolution rates for uranium determined by radiochemical analysis and by gamma spectrometry were similar. However, gamma spectrometry analysis suggested a difference between the half times of 238U and its initial decay product 234Th, which may have important implications for in vivo monitoring of uranium.

Air Pollutants, Radioactive↗
PubMed2002

[Archaeological application of the Raman microprobe to the non-destructive identification of dinosaur fossil from Yunnan Wuding].

Selected ancient Dinosaur fossils (about a hundred million ago) from Wuding, Yunnan, pilot were studied by micro-Raman spectroscopy, atomic emissive spectrum and polarization microscopic analysis. Raman experimental results found out the primary compounds of fossil surface and section are calcite (CaCO3), and are not others. Analysis of atomic emissive spectrum indicated that main elements of fossils are calcium (> 10%), silicon (5.0%), phosphor (4.0%) and iron (1.0%), rare elements example of iridium (Ir) and thorium (Th) are not found in testing. Complementary studies by atomic emissive spectrum and polarization microscope found that besides calcite (CaCO3), SiO2.nH2O, which is not crystal, is contained in the examples of the fossils. Main composition data taken from both the atomic emissive spectrum, microscopic photograph and Raman spectroscopy are in agreement.

English Abstract↗
PubMed1998

Managing metabolic model deficiencies for routine radiation protection purposes at a thorium dioxide facility.

At a metallurgical facility using thorium dioxide feed materials, a number of conventional direct- and indirect-bioassay methods were potentially suitable monitoring methodologies when industry-standard dose assessment methodologies were based upon ICRP recommendations issued in 1959. When the ICRP recommended a different dose assessment methodology in 1977, the intake limits for thorium dropped significantly, and conventional bioassay methods for routine monitoring were rendered ineffective. While determining the technical basis for its air monitoring program, the facility noted that the radioactive materials used as feed to the process were highly insoluble. Therefore, their solubility in simulated lung fluids was determined. The results of this determination indicated that the facility's materials, if inhaled, dissolve in the lung at a half-time that is significantly longer than that contained in international consensus standards for Y-class compounds. They also indicated that the secondary dose limits, if adjusted to eliminate the dose contribution from translocated radionuclides, should be higher, and that a derived air concentration based upon more recent international recommendations is more appropriate for use in the facility's routine monitoring program.

Biological Assay↗
PubMed2001

Concentrations of natural radionuclides in imported mineral substances.

Levels of natural radionuclides, such as thorium-232 (232Th), radium-226 (226Ra) and potassium-40 (40K), were determined in about 2,000 samples of imported mineral substances using gamma spectrometry. The maximum concentration levels of 232Th, 226Ra and 40K were 1,260 +/- 54, 13,400 +/- 94 and 1,256 +/- 260 Bq kg(-1), respectively, in zirconium compounds. Due to relatively high concentrations of the above-mentioned radionuclides in some imported mineral substances, the National Radiation Protection Department (NRPD), as the competent authority, has established national limits (900 Bq kg(-1) for 232Th, 1800 Bq kg(-1) for 226Ra and 11,000 Bq kg(-1) for 40K), based on the external exposures, for general importation permits of these materials.

Commerce↗
PubMed1999

Population study in the high natural background radiation area in Kerala, India.

A comprehensive survey of the population exposed to high-level natural radiation is presented. The population living in Karunagappally taluk in Kerala, India, presents a unique opportunity for studies on the health effects of chronic exposure to low-level radiation. The environmental radiation emanates largely from the thorium deposited mostly along coastal areas. In certain locations on the coast, it is as high as 70 mGy/year and on average is 7.5 times the level seen in interior areas. Using portable scintillometers, radiation levels in more than 66,306 houses were measured; outside levels were also measured in the same house compound. Of the total population of 400,000, 100,000 lived in areas with high natural radiation. Information on lifestyle, socio-demographic features, occupation, housing, residence history, and tobacco and alcohol use was obtained by house-to-house visits and enumeration of every resident individual. A population cancer registry system has been established to obtain cancer incidence rates. In this preliminary analysis, there is no evidence that cancer occurrence is consistently higher because of the levels of external gamma-radiation exposure in the area. Further dosimetry-level studies are needed along with biological studies. Studies of soil, thoron-in-breath, and the radon-thoron levels in houses are ongoing, and further case-control analyses are continuing.

Adolescent↗
PubMed1975

[Liver disease in polyvinyl chloride production workers - Clinical and peritoneoscopic aspects (author's transl)].

Peculiar clinical symptoms observed in polyvinyl chloride production workers of a nearby chemical plant arose the suspicion of liver and spleen disease in these workers before first reports on vinyl chloride-induced angiosarcoma of the liver became known. Starting at the end of 1972, 44 workers were followed up by biochemical investigations, peritoneoscopy and liver biopsy. As early as 1973 it could be ascertained, that advanced vinyl chloride-induced liver damage presents as hepatic fibrosis with splenomegaly, portal hypertension, and thrombocytopenia without conspicuous deterioration of hepatic parenchyma function. Similar symptoms have been observed after chronic intoxication by arsenic and thorium dioxide (thorotrast). The clinical and peritoneoscopic aspects of the disease are described.

Chemical Industry↗
PubMed1993

High-performance liquid chromatographic method for simultaneous determination of clodronate and some clodronate esters.

A quaternary alkylmethylamine-bonded stationary phase has been used for the liquid chromatographic resolution of bisphosphonates. Clodronate and three of its esters were separated by this technique. Nitric acid (30 mM) was used as the mobile phase. The effect of the pH of the mobile phase on the retention, resolution, capacity factor and theoretical plates of the column was examined. Thorium-ethylenediaminetetraacetic acid-xylenol orange mixed ligand complex was used as a postcolumn reagent for bisphosphonates. Bisphosphonates react quantitatively with this complex in slightly acidic solutions, and a change in the absorbance of postcolumn reagent is used as a measure of the bisphosphonate concentration. The relative standard deviation (R.S.D.) values for samples in aqueous solutions were in the range 2.3-15.5% (area) and 1.7-5.9% (height). The detection limits for different compounds, Cmin, varied from 0.3 to 1.4 mg/l (area) and from 0.3 to 0.5 mg/l (height). In urine samples the R.S.D. (%) varied from 3.1 to 18.9 (area) and from 1.1 to 6.3 (height). The linear dynamic range was from the detection limit up to 16 mg/l.

Chromatography, High Pressure Liquid↗
PubMed1998

Near-surface disposal of concentrated NORM wastes.

Naturally occurring radioactive material (NORM) in concentrated forms arises in nature and in industry where natural radioisotopes become mobile and then accumulate at particular sites. In industry this often occurs in an acidic environment, where precipitates containing radionuclides plate out onto pipe walls, filters, tank linings, etc. As the radionuclides are selectively deposited, they build up and there is a multiplying effect in terms of the radioactivity concentration. Conditions often tend to favour the build-up of radium, particularly when barium is present and can cause the co-precipitation of radium compounds. As radium is highly radiotoxic, the handling and disposal of such material requires careful management. The state of Western Australia currently has the only low level waste repository in Australia, located at Mt Walton East. To date this repository has been used predominantly to dispose of packaged radioactive waste containing artificial radioisotopes, but there is an increasing demand for the repository to accept bulk concentrated NORM wastes from mining and related industries. Already steelwork from a dismantled phosphoric acid plant and other items contaminated with NORM have been disposed of. The Mt Walton East repository is now proposed as the disposal site for 6000 tonnes per annum of gangue residue from the processing of monazite. The residue contains thorium and a small amount of radium. This paper looks at the technical and related considerations of these disposal operations.

Environmental Exposure↗
PubMed1995

Uranium dust exposure and lung cancer risk in four uranium processing operations.

We examined the relation between uranium dust exposure and lung cancer mortality among workers employed in four uranium processing or fabrication operations located in Missouri, Ohio, and Tennessee. Among workers who had at least 30 years of potential follow-up, we identified 787 lung cancer cases from death certificates and matched one control to each case. Health physicists estimated individual annual lung doses from occupational exposure primarily to insoluble uranium compounds, using contemporary monitoring data. With a 10-year lag, cumulative lung doses ranged from 0 to 137 centigrays (cGy) for cases and from 0 to 80 cGy for controls. Health physicists assigned annual external radiation doses to workers having personal monitoring records. Archivists collected smoking information from occupational medical records. Odds ratios for lung cancer mortality for seven cumulative internal dose groups did not demonstrate increasing risk with increasing dose. We found an odds ratio of 2.0 for those exposed to 25 cGy and higher, but the 95% confidence interval of 0.20 to 20 showed great uncertainty in this estimate. There was a suggestion of an exposure effect for workers hired at age 45 years or older. Further analyses for cumulative external doses and exposures to thorium, radium, and radon did not reveal any clear association between exposure and increased risk, nor did dichotomizing workers by facility.

Adult↗
PubMed1971

Permeability of the ovarian follicle of Aedes aegypti mosquitoes.

The passage of tracers of various molecular weights into resting and vitellogenic ovarian follicles of Aedes aegypti mosquitoes was studied ultrastructurally. The outermost layer of the follicular sheath (the basement lamina) is a coarse mechanical filter. It is freely permeable to particles with molecular weights ranging from 12,000 to 500,000 (i.e. cytochrome c, peroxidase, hemoglobin, catalase, ferritin, immunoglobulin (IgG)-peroxidase, iron dextran and Thorotrast) that have dimensions less than 110 A. Molecules as large as carbon (300-500 A) are totally excluded. Whereas proteins and polysaccharide tracers permeate the basement lamina with apparent ease, certain inert particles (e.g. Thorotrast, Fellows-Testager Div., Fellows Mfg. Co., Inc., Detroit, Mich.) penetrate more slowly. With respect to the tracers tested, resting follicles are as permeable as vitellogenic follicles. The follicle epithelium of resting or vitellogenic follicles is penetrated by narrow intercellular channels. Our observations suggest that these spaces are lined with mucopolysaccharide material. After permeating the basement lamina, exogenous tracers fill these channels, while the bulk of material accumulates in the perioocytic space. Within 3 hr after imbibing blood, the pinocytotic mechanism of the oocyte is greatly augmented. Pinocytosis is not selective with regard to material in the perioocytic space, since double tracer studies show that exogenous compounds are not separated, but are incorporated into the same pinocytotic vesicle. During later stages of vitellogenesis, 36-48 hr after the blood-meal, the pinocytotic mechanism of the oocyte is diminished. Simultaneously, the intercellular channels become occluded by desmosomes, and the vitelline membrane plaques separate the oocyte and follicle epithelium.

Aedes↗
PubMed1985

Comparison of Ca-DTPA and Zn-DTPA in removing 234Th from the rat.

The relative effectiveness of Ca-DTPA and Zn-DTPA as a function of the dose, number of doses and time of their administration in removing 234Th that had been administered as the citrate or nitrate from various rat organs was investigated. With a single early treatment (1.5 min after intravenous injection of 234Th), Zn-DTPA was clearly less effective than Ca-DTPA over the whole dose range (30 mumol/kg body weight-1000 mumol/kg body weight) tested. In the skeleton, 1000 mumol Zn-DTPA/kg removed as much 234Th (about 50%) as 30 mumol Ca DTPA/kg. Prompt treatment with 100 mumol Ca-DTPA/kg body weight diminished the skeletal 234Th content by about 70%; but when it was delayed by 6 h or 4 d, the 234Th content was reduced by only about 20% and 10%, respectively. The effect of DTPA in the bone was independent of 234Th compound, while in the soft tissues 234Th injected as nitrate was less affected than the citrate. The effect of DTPA was potentiated when treatment was repeated; the end effect was dependent on the time of the first DTPA injection and on the total number of doses. Thus, about 90% and 50% less 234Th was found in the bones after repeated treatment started at 1.5 min and 4 d after administration of 234Th, respectively. Under the conditions of a delayed repeated treatment, Ca-DTPA and Zn-DTPA were equally effective.

Animals↗
PubMed1995

Phosphorus as a potential guide in the search for extinct life on Mars.

In contrast to the search for extant organisms, the quest for fossil remains of life on Mars need not be guided by the presence of water and organic compounds on the present surface. An appropriate tracer might be the element phosphorus which is a common constituent of living systems. Utilizing terrestrial analogues, it should preferentially exist in the form of sedimentary calcium phosphate (phosphorites), which would have readily resisted changing conditions on Mars. Moreover, higher ratios of P/Th in phosphorites in comparison to calcium phosphates from magmatic rocks give us the possibility to distinguish them from inorganically formed phosphorus deposits at or close to the Martian surface. Identification of anomalous phosphorus enrichments by remote sensing or in situ analysis could be promising approaches for selecting areas preferentially composed of rocks with remains of extinct life.

Calcium Phosphates↗
PubMed1999

Accurate charge densities in days - use of synchrotrons, image plates and very low temperatures.

Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on tetrakis(dimethylphosphinodithioato-S,S')thorium(IV), [Th(S(2)PMe(2))(4)]. The use of very low temperatures, well below those obtained with liquid-nitrogen cooling, is crucial for the accuracy of the data. This is due to minimization of temperature-dependent systematic errors such as TDS and anharmonicity, and extension and intensification of the data in reciprocal space. Comparison of structural parameters derived separately from the sealed-tube data and the synchrotron data shows good agreement. The synchrotron data are markedly superior when comparing refinement residuals, standard uncertainties (s.u.'s) of the data and s.u.'s of the derived parameters. However, the study suggests that there are still small uncorrected systematic errors in the data. The very large extent [(sinstraight theta/lambda)(max) = 1.77 Å(-1)] of the synchrotron data and the very low temperature at which they were collected makes it possible to separate anharmonic effects from electron-deformation effects even with only an X-ray data set at a single temperature. The electron density shows a large polarization of the outer Th core of d-type symmetry. This deformation is successfully modelled with contracted multipolar functions, which are only slightly correlated with anharmonic expansions in reciprocal space when using the full extent of the data. In the data collection more than a factor of 100 in speed is gained by use of image-plate area detectors at the synchrotron source compared with conventional sequential measurements. Thus accurate, very low temperature synchrotron-radiation diffraction data can now be measured within days, which makes electron-density studies of compounds beyond the first transition series more frequently within reach.

Journal Article↗
PubMed2000

Effect of leachability on environmental risk assessment for naturally occurring radioactive materials in petroleum oil fields.

Elevated concentrations of naturally occurring radioactive material (NORM), including 238U, 232Th, and their progeny found in underground geologic deposits, are often encountered during crude oil recovery. Radium, the predominant radionuclide brought to the surface with the crude oil and produced water, co-precipitates with barium in the form of complex compounds of sulfates, carbonates, and silicates found in sludge and scale. These NORM deposits are highly stable and very insoluble under ambient conditions at the earth's surface. However, the co-precipitated radium matrix is not thermodynamically stable at reducing conditions which may enable a fraction of the radium to eventually be released to the environment. Although the fate of radium in uranium mill tailings has been studied extensively, the leachability of radium from crude oil NORM deposits exposed to acid-rain and other aging processes is generally unknown. The leachability of radium from NORM contaminated soil collected at a contaminated oil field in eastern Kentucky was determined using extraction fluids having wide range of pH reflecting different extreme environmental conditions. The average 226Ra concentration in the samples of soil subjected to leachability testing was 32.56 Bq g(-1) +/- 0.34 Bq g(-1). The average leaching potential of 226Ra observed in these NORM contaminated soil samples was 1.3% +/- 0.46% and was independent of the extraction fluid. Risk assessment calculations using the family farm scenario show that the annual dose to a person living and working on this NORM contaminated soil is mainly due to external gamma exposure and radon inhalation. However, waterborne pathways make a non-negligible contribution to the dose for the actual resident families living on farmland with the type of residual NORM contamination due to crude oil recovery operations.

Animal Feed↗