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PubMed1991

The efficacy of DTPA treatment after deposition of thorium nitrate in the rat lung.

The efficacy of CaDTPA and ZnDTPA, the chelating agents of choice for several actinide elements, have been evaluated after the deposition of thorium in the rat lung in widely different amounts. The results showed that: 1. When the initial mass concentration of thorium simulated human exposure to four times the annual limits on intake for 232Th, the prompt (300 or 1000 mumol kg-1 body weight at 0.02 d) or repeated (30 or 300 mumol kg-1 body weight at 0.02, 0.25, 1,2,3 d) administration of CaDTPA were at best only moderately successful for enhancing the elimination of thorium. By 7 d after exposure, the body contents of thorium were, respectively, about 74%, 65%, 90% and 74% of those present in untreated animals. 2. When the mass concentration simulated 1.7 x 10(-3) times the annual limits on intake for 232Th, the efficacy of treatment was not increased appreciably despite the substantial reduction in mass. After the repeated administration of CaDTPA at doses of 30 and 300 mumol kg-1 using the protocol above, the body contents of thorium by 7 d were, respectively, 69% and 51% of those in untreated animals. 3. Under comparable conditions, the efficacy of ZnDTPA was less than CaDTPA. The results suggest that more effective chelating agents are needed for the treatment of workers exposed to water soluble thorium compounds.

Administration, Inhalation↗
PubMedDate not supplied

Quantitative CT for determination of thorium in thorotrast patients.

The concentrations of thorium in the liver, spleen, and their efferent lymph nodes were determined in six thorotrast patients by quantitative CT scanning. Thorium concentration per CT number was calibrated by scanning a phantom that contained a known concentration of thorium nitrate solution. The total amount of thorium determined by the quantitative CT method in the liver, spleen, and lymph nodes was compared with that determined by gamma-ray measurement of the upper abdomen using a whole body counter. A linear relationship was obtained between the amount of thorium determined by the CT method and that determined by the gamma-ray measurement method, although the correlation was not high. The quantitative CT method appears to be useful for determining, with some accuracy, the concentration of thorium in the liver, spleen, and lymph nodes of thorotrast patients.

Gamma Rays↗
PubMed2006

Influence of the soil bioavailability of radionuclides on the transfer of uranium and thorium to mushrooms.

The soil-mushroom transfer of thorium and uranium was analyzed in two ecologically similar but geographically separated Spanish ecosystems by means of the transfer factor, TF. Uranium TF values were in the range 0.043-0.49, and thorium TF values in the range 0.030-0.62. These values were similar to those of (90)Sr, (239+240)Pu, and (241)Am found previously in the same ecosystems. Given the low availability of uranium and thorium, the available transfer factors, ATF, were also determined. These were higher than the TF values by one order of magnitude for (234, 238)U, and by 2-3 orders of magnitude for (228, 230, 232)Th. The ATF value of thorium was similar to that of (137)Cs, and that of uranium similar to that of (40)K. Hebeloma cylindrosporum presented the highest uranium and thorium transfer factors, confirming this species as a good bioindicator of a soil's radioactive content.

Agaricales↗
PubMed2001

Determination of thorium by ICP-MS and ICP-OES.

Natural thorium (232-Th) has traditionally been measured by radiometric techniques such as alpha and gamma spectrometry. However. with both ICP-OES and ICP-MS instruments becoming relatively common in many analytical laboratories. these techniques have become more acceptable in thorium analysis. This paper will briefly describe an overview of the instrumentation currently available and the techniques themselves applied to thorium analysis. Both techniques have low detection limits and require little sample treatment after the sample digestion. Routine sample analysis time is short and spectra easy to interpret. usually giving results with low uncertainties, Whereas ICP-OES measures total thorium only, ICP-MS also offers the potential to measure other long-lived thorium isotopes (t 1/2 > 10(4) years), such as 232Th. However, other important isotopes, such as 228Th. are still out of reach for routine analysis. The main disadvantage of the techniques is the requirement for a sample digestion stage.

Mass Spectrometry↗
PubMed1983

Mortality among male workers at a thorium-processing plant.

The long-term health effects of exposure to thorium are of interest because of the possible increased use of thorium as an energy source in reactors using 232Th to produce 233U. Mortality is described in a cohort of 3039 men who were employed between 1940 and 1973 at a company involved in the production of thorium and rare earth chemicals from monazite sand. Based on deaths ascertained by the Social Security Administration and mortality rates for U.S. white males, the standardized mortality ratio (SMR) for all causes was 1.05 with 95% confidence limits (95% CL) of 0.96 and 1.15. Much of the excess mortality was attributable to non-occupational motor vehicle accidents (SMR = 1.64; 95% CL = 1.16 and 2.23), but SMRs were also high for lung cancer (1.44; 95% CL = 0.98 and 2.02), pancreatic cancer (2.01; 95% CL = 0.92 and 3.82), and diseases of the respiratory system (1.31; 95% CL = 0.92 and 1.83). In a subgroup of 592 men who worked for at least one year in selected jobs (indicative of highest exposure to thorium and thoron) that was followed up more intensively, the SMR for pancreatic cancer was significantly elevated (i.e. 4.13; 95% confidence limits = 1.34 and 9.63). The SMR for lung cancer was 1.68 (95% CL = 0.81 and 3.09), while that for respiratory diseases was 1.20 (95% CL = 0.52 and 2.37). Information on smoking habits in a sample of survivors suggested that smoking could have explained at least part of the excess mortality from lung and pancreatic cancer and from diseases of the respiratory system. Continued follow-up of the cohort through morbidity and mortality studies is needed to evaluate further the possible long-term effects of exposure to radioactivity and chemicals in the thorium extraction process.

Adult↗
PubMed1995

Thorium excretion in feces by mineral sands workers.

An attempt has been made to correlate the thorium excreted in the feces of two male workers in the monazite section of a mineral sands dry separation plant over a ten-day period with personal air sampling measurements. The air-borne radioactivity was measured on a daily basis using a total (inspirable) dust filter, an integrating personal dosimeter, and a personal cascade impactor. The thorium content of the feces was measured using inductively coupled plasma mass spectrometry. The results suggest that thorium fecal analyses are able to detect acute and chronic exposures to the inhalation of thorium bearing dusts and to confirm the amount of inhaled thorium predicted from air sampling programs and metabolic models.

Administration, Inhalation↗
PubMed1995

Thorium lung burdens of mineral sands workers.

Thorium lung burdens have been measured in workers in the dry separation plants operated by the mineral sands industry in Western Australia. The data have been compared with historical employment records of the worker's exposure to thorium-bearing airborne dusts in order to assess the reliability of personal air sampling and with the predictions of the new Task Group lung model. The thoron exhaled in the breath of 62 workers was measured using a double filter tube. Six of the workers also underwent in-vivo gamma counting to determine their thorium lung burden. A thoron exhalation rate of 4.7% was obtained from a comparison of the two data sets. The estimated thorium lung burdens from the thoron-in-breath measurements had a geometric mean value of 10 Bq. The workers had a geometric mean employment period in the industry of 9.2 y and a geometric mean total inhaled alpha activity of 9,000 Bq, estimated from contemporary personal air sampling data and a retrospective assessment of previous workplace conditions. This exposure corresponds to a mean daily intake of 232Th of 0.45 Bq. Predictions from the new Task Group lung model indicate that, for the 45 workers with a thorium lung burden in excess of the minimum detectable level (6 Bq), the daily intake of 232Th is a factor of 1.6 higher than expected. This result suggests that previous intake of radioactive dust was higher than generally assumed for some workers. The application of the new Task Group lung models to the bioassay data results in an estimated mean annual committed effective dose for the workers of 8 mSv. Two workers (3%) were found to have been exposed for many years in excess of the 50 mSv y-1 annual limit for occupational exposure, while eight workers (13%) exceeded the ICRP's proposed new occupational standard of an average of 20 mSv y-1. All eight had been employed for more than 6 y and the majority of their exposure was attributed to early employment years, prior to extensive workplace improvements in dust control.

Air Pollutants, Radioactive↗
PubMed1997

Basis and implications of the ICRP's new biokinetic model for thorium. International Commission on Radiological Protection.

The International Commission on Radiological Protection (ICRP) has adopted a new, age-specific biokinetic model for thorium, along with new assumptions concerning the fate of radioactive progeny produced in the body after intake of thorium. This paper explains the basis for the model and assumptions and examines some of their implications with regard to radiation dosimetry and bioassay. The new model differs substantially from the ICRP's previous biokinetic model for thorium (introduced in 1979 in ICRP Publication 30) with regard to model structure, sources of data used to derive parameter values, predictions of integrated activities of long-lived thorium isotopes in some radiosensitive organs, and predictions of the rates of urinary and fecal excretion of thorium at times remote from exposure. For the case of injection of 232Th into blood of an adult, the new model and assumptions yield 4- to 8-fold decreases in predictions of 50-y committed equivalent doses to radiosensitive skeletal tissues but 7- to 55-fold increases in predictions of committed equivalent doses to extra-skeletal tissues, compared with the model and treatment of decay chain members recommended in ICRP Publication 30.

Adult↗
PubMed1990

The role of thorium in endomyocardial fibrosis.

The behaviour of thorium in animals exposed through injection, ingestion and inhalation, as well as in uranium miners, millers and the general population suggests that thorium accumulates primarily in the lung, tracheobronchial lymph nodes and skeleton; or in the liver if injected with polymeric thorium. Epidemiological studies on uranium miners, Thorotrast studies in man and animal, and studies on the toxic effects of thorium in animals suggest that there is no apparent heart diseases due to exposure to thorium in man and animal.

Animals↗
PubMed1989

Uptake and intracellular compartmentation of thorium in Saccharomyces cerevisiae.

When Saccharomyces cerevisiae was cultured in the presence of thorium, the element was accumulated by the cells and was visible in electron micrographs as electron dense granules. When thorium was present during exponential growth, these granules were located mainly in the vacuole, with some present in the cytosol. Where thorium was present only during the stationary phase, there appeared to be greater thorium deposition in the cell wall than during exponential growth and some vacuolar deposits were also evident. Thorium uptake by exponential-phase cells was not stimulated by glucose and was thus independent of metabolic energy.

Journal Article↗
PubMed2001

Uranium and thorium series disequilibrium in quaternary carbonate deposits from the Serra da Bodoquena and Pantanal do Miranda, Mato Grosso do Sul State, central Brazil.

Activities of gamma-ray emitting members of the uranium (238U) and thorium (232Th) series were measured in a quaternary limestone deposit that outcrops in the southeastern Pantanal Matogrossense Basin and in quaternary tufas deposited at the drainage of the Serra da Bodoquena. It is a first step in a study of the mobilization of uranium and thorium series and its relation to surface hydrology, in a region where carbonate deposits are being continuously dissolved and reprecipitated. The obtained results show that all these deposits are characterized by very low concentrations of uranium and thorium. The 238U/226Ra and 228Th/228Ra activity ratios are significantly different than 1.0, indicating that both series are in radioactive disequilibrium. Although the Serra da Bodoquena deposits seem to be very recent, their very fine granulation and high porosity suggest that they behave as open systems for geochemical exchanges of uranium and thorium series members. The Pantanal do Miranda limestone has a radiocarbon age of 3900 yr BP. Since the thorium series is in disequilibrium it is also concluded that this deposit behaves as an open system for geochemical exchanges.

Journal Article↗
PubMed2005

Electronic structure, excited states, and photoelectron spectra of uranium, thorium, and zirconium bis(Ketimido) complexes (C5R5)2M[-NCPh2]2 (M = Th, U, Zr; R = H, CH3).

Organometallic actinide bis(ketimide) complexes (C5Me5)2An[-N=C(Ph)(R)]2 (where R = Ph, Me, and CH2Ph) of thorium(IV) and uranium(IV) have recently been synthesized that exhibit chemical, structural, and spectroscopic (UV-Visible, resonance-enhanced Raman) evidence for unusual actinide-ligand bonding. [Da Re et al., J. Am. Chem. Soc., 2005, 127, 682; Jantunen et al., Organometallics, 2004, 23, 4682; Morris et al., Organometallics, 2004, 23, 5142.] Similar evidence has been observed for the group 4 analogue (C5H5)2Zr[-N=CPh2]2. [Da Re et al., J. Am. Chem. Soc., 2005, 127, 682.] These compounds have important implications for the development of new heavy-element systems that possess novel electronic and magnetic properties. Here, we have investigated M-ketimido bonding (M = Th, U, Zr), as well as the spectroscopic properties of the highly colored bis-ketimido complexes, using density functional theory (DFT). Photoelectron spectroscopy (PES) has been used to experimentally elucidate the ground-state electronic structure of the thorium and uranium systems. Careful examination of the ground-state electronic structure, as well as a detailed modeling of the photoelectron spectra, reveals similar bonding interactions between the thorium and uranium compounds. Using time-dependent DFT (TDDFT), we have assigned the bands in the previously reported UV-Visible spectra for (C5Me5)2Th[-N=CPh2]2, (C5Me5)2U[-N=CPh2]2, and (C5H5)2Zr[-N=CPh2]2. The low-energy transitions are attributed to ligand-localized N p --> C=N pi excitations. These excited states may be either localized on a single ketimido unit or may be of the ligand-ligand charge-transfer type. Higher-energy transitions are cyclopentadienyl pi --> CN pi or cyclopentadienyl pi --> phenyl pi in character. The lowest-energy excitation in the (C5Me5)2U[-N=Ph2]2 compound is attributed to f-f and metal-ligand charge-transfer transitions that are not available in the thorium and zirconium analogues. Geometry optimization and vibrational analysis of the lowest-energy triplet state of the zirconium and thorium compounds also aids in the assignment and understanding of the resonance-enhanced Raman data that has recently been reported. [Da Re et al., J. Am. Chem. Soc., 2005, 127, 682.].

Journal Article↗
PubMed2001

Distribution of natural thorium in the tissues of a whole body.

The distribution of thorium in the tissues of a whole body donor to the United States Transuranium and Uranium Registries is described. This case, identified by the USTUR as Case 0212, had two documented intakes of plutonium and americium from occupational accidents while employed at Hanford but no known occupational exposure to thorium. Concentrations of 239+240Pu, 241Am, and 232Th in the tissues are compared and the distribution of these isotopes in this case is evaluated. The distribution data for 232Th are compared to those from previous studies of thorium in human tissues resulting from environmental exposure and to an individual exposed to Thorotrast (colloidal ThO2) in a medical diagnostic procedure. The 232Th distribution data from this work are also compared against ICRP 30 and ICRP 69 models for the behaviour of thorium in the human body.

Americium↗
PubMed2001

Analysis of thorium and its progeny by gamma ray spectrometry and alpha track methods.

Samples originating from an EU sponsored intercomparison exercise were analysed by gamma ray spectrometry (a thorium solution sample, a zircon sand sample and a thorium ore sample). An alpha track method was also used to analyse the solution sample. The detection efficiency calibration for the gamma ray spectrometry measurements on the solid samples was established using an in-house standard of thorium nitrate. A GESPECOR Monte Carlo simulation program was utilised in the analysis of the solution sample. The in-house thorium nitrate standard was also used to prepare standards for the alpha track method. The relative differences between the 232Th activity concentration values determined in these intercomparison samples and values supplied by the NPL, UK, were found to be less than 5% when determined by the gamma ray spectrometry method and less than 8% when determined by the alpha track method.

Alpha Particles↗
PubMed1992

Measurement of thorium isotopes and 228Ra in soft tissues and bones of a deceased Thorotrast patient.

The whole body of an individual injected with Thorotrast 36 y prior to her death was analyzed for 232Th, 228Ra, 228Th, and 230Th. Measurement of these isotopes in all tissues of the body will provide data necessary to caculate the radiation dose to individual tissues and to evaluate the risk potential associated with deposition of thorium and progeny in humans. The tissues were ashed, dissolved in acid, and the thorium isolated by ion exchange and electrodeposition. The 228Ra was determined by measuring the 0.991-MeV gamma rays associated with decay of the 228Ac daughter. It was estimated that almost all of the 232Th from the original injection was retained in the body, mostly in the tissues of the reticuloendothelial system. A total of 28 kBq (0.76 microCi) of 232Th was measured in the soft tissues and bones. The body also contained 13 kBq 228Ra, 12 kBq 228Th, and 3.9 kBq 230Th. A Thorotrastoma contained about 3.5% of the total activity. Excluding the Thorotrastoma, approximately 45% of all the activity (232Th, 228Ra, 228Th, and 230Th) was retained in the liver, 13% in the spleen, 2% in muscle, 1% in skin, slightly less than 1% in the respiratory tract, 4% in all other soft tissues, and 33% in the skeleton (bone and bone marrow). Sixty to 80% of the thorium activity in bones containing red marrow was located in the marrow. Bones containing yellow marrow had less than 40% of the thorium activity in the marrow. Highest concentrations were found in the hepatic and other abdominal lymph nodes, spleen, hilar lymph nodes, liver, trachea, and bone. Approximately 60% of the 228Ra formed from the decay of the 232Th had been excreted from the body. The 228Ra and 228Th were in approximate equilibrium throughout the body.

Aged↗
PubMed1989

[Thorium in soil, vegetables, cereals and fruit].

Thorium contents (alpha-activities of the naturally occurring isotopes Th-228, Th-230, and Th-232) were determined in soils, vegetables, cereals, and fruits. The thorium content of plants depends on the degree of contamination by soil resuspension and thus on the specific surface of the plants. The activity of the isotope Th-230 is almost the same as that of the main isotope Th-232. Th-228, with about the same activity as Th-232 in soil, increases to about 10-fold the activity in vegetables, 29-fold in sweet chestnuts and 740-fold in Brazil nuts. Thorium concentration factors from the soil to these vegetable products are calculated; they include the total concentration, not only the soluble portion of thorium.

Edible Grain↗
PubMed1992

[Thorium amd uranium in food of animal origin].

The thorium and uranium contents (alpha-activities of the natural isotopes Th-228, Th-230, Th-232, U-234, and U-238) in several samples of the meat of domestic animals, venison, and cold-blooded animals are reported. The activity of thorium and of uranium was surprisingly constant in lean meat of all the animals tested. The average activity of the main isotope of thorium was 1-2 mBq Th-232/kg fresh meat (FM) and of uranium 21-34 mBq U-238/kg FM. The lowest and highest values observed were 0.4 and 2.7 mBq Th-232/kg FM, and 9 and 41 mBq U-238/kg FM, respectively. In some internal organs distinctly higher values were obtained: 8.6 mBq Th-232/kg in cattle bones, and 51 mBq U-238/kg in hog kidneys. The highest content of U-238, 84 mBq/kg, was observed in cuttlefish (whole animal). In lean meat, the activity of the daughter isotope Th-228 was on average (by factor) two to four times higher than that of the parent isotope Th-232. In cattle bones, and in fish samples including bones, the factor was 20 and 26, respectively. The activity of the isotope Th-230 ranged between Th-232 and Th-228. In all samples investigated, the daughter isotope U-234 showed an excess activity of 19 +/- 7% as compared to the parent isotope U-238. The above nuclides were determined alpha-spectrometrically using Th-229 for thorium, and U-232 for uranium as internal standard.

Animals↗
PubMed1986

Daily intake of thorium by an Indian urban population.

Thorium intake by an urban group (Bombay) has been estimated using neutron activation followed by simple chemical separation. Daily intake of thorium via all the three sources: food, water and air, is reported in this paper. The major contribution of thorium to intake is through food (2.0 micrograms), followed by water (0.02 microgram) and air (0.02 microgram). The individual food ingredients such as cereals, pulses, vegetables, milk, etc. were also analysed for their thorium content. The cereals were found to contribute most to the daily intake.

Environmental Monitoring↗