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PubMed1975

Toxicology of high-fired beryllium oxide inhaled by rodents. II. Metabolism and early effects.

Several groups of male and female rats and hamsters were exposed by inhalation to an aerosol of BeO particles calcined at 1000 C. Initial alveolar depositions ranged from 12 mug to 160mug Be. The alveolar retention half-life for BeO was approximately six months. Only the pulmonary lymph nodes accumulated detectable amounts of translocated BeO. Early alterations were seen in the alveolar macrophages, which were subsequently converted to histiocytic cells that accumulated in subpleural and peribronchiolar granulomatous lesions within eight months after the exposure. The alveolar clearance of a test aerosol, radioactive plutonium dioxide (239PuO2), was decreased to 60% of the normal rate when the radioactive material was given at 1, 30, or 60 days after exposure to BeO. These results demonstrate the important function of the alveolar macrophage in Be-induced granulomatous disease, as well as the rapid impairment of alveolar macrophage function by phagocytized BeO.

Animals↗

PubMed1998

The uptake of radionuclides by beans, squash, and corn growing in contaminated alluvial soils at Los Alamos National Laboratory.

Pinto beans (Phaselous vulgaris), sweet corn (Zea mays), and zucchini squash (Cucurbita pepo) were grown in a field pot study using alluvial floodplain soils contaminated with various radionuclides within Los Alamos Canyon (LAC) at Los Alamos National Laboratory, New Mexico. Soils as well as washed edible (fruit) and nonedible (stems and leaves) crop tissues were analyzed for tritium (3H), cesium (137Cs), strontium (90Sr), plutonium (238Pu and 239,240Pu), americium (241Am), and total uranium (totU). Most radionuclides, with the exception of 3H and totU, in soil and crop tissues from LAC were detected in significantly higher concentrations (p < 0.05) than in soil or crop tissues collected from regional background locations. Significant differences in radionuclide concentrations among crop species (squash were generally higher than beans or corn) and plant parts (nonedible tissue were generally higher than edible tissue) were observed. Most soil-to-plant concentration ratios for radionuclides in edible and nonedible crop tissues grown in soils from LAC were within default values in the literature commonly used in dose and risk assessment models. Overall, the maximum net positive committed effective dose equivalent (CEDE)--the CEDE plus two sigma for each radioisotope minus background and then all positive doses summed--to a hypothetical 50-year resident that ingested 352 lb ([160 kg]; the maxiumum ingestion rate per person per year) of beans, corn, and squash in equal proportions was 74 mrem y-1 (740 microS y-1). This upper bound dose was below the International Commission on Radiological Protection permissible dose limit of 100 mrem y-1 (1000 microS y-1) from all pathways and corresponds to a risk of an excess cancer fatality of 3.7 x 10(-5) (37 in a million), which is also below the U.S. Environmental Protection Agency's guideline of 10(-4).

Environmental Health↗

PubMed1993

Efficacy of 3,4,3-LIHOPO for reducing the retention of 238Pu in rat after inhalation of the tributyl phosphate complex.

The efficacy of 3,4,3-LIHOPO, a siderophore analogue, has been tested for removing 238Pu from rat after inhalation of plutonium as the tri-N-butylphosphate (TBP) complex. The amounts of Pu retained in the lung of untreated rat, 7 days after exposure ranged from 0.86 to 37 kBq. The results have been compared with DTPA, the current therapy of choice for man. The ligand 3,4,3-LIHOPO was more effective than DTPA for removing Pu from the body when repeated treatment began 1 h after inhalation. This observation was independent of the mass of Pu deposited in the lungs. The efficacy of 3,4,3-LIHOPO was mainly due to the decrease of Pu retention in lung, 1.5 times less than after DTPA administration; in liver and skeleton, retention was about four times less. Seven days after internal contamination, < 10% of the activity was found in organs other than lung when rat was treated with 3,4,3-LIHOPO. As this ligand showed an apparent lack of irreversible toxicity, it is likely to be of interest in the development of new decorporation treatments after inhalation of Pu as a TBP complex.

Administration, Inhalation↗

PubMed1995

Efficacy of 3,4,3-LIHOPO for reducing the retention of uranium in rat after acute administration.

Decorporation therapy is the only known effective method of reducing the radiation dose to persons following accidental internal contamination with transportable radionuclides. Deposits of actinides in bone should be minimized because development of osteosarcoma appears to be related to internal exposure. In contrast with other actinides, such as plutonium or americium where chelating agent treatment is efficient, the therapeuric approaches used for cases of uranium contamination are widely ineffective. This is the first report on in vivo efficacy of a chelating agent, a siderophore analogue code named 3,4,3-LIHOPO, after systematic exposure to natural uranium in the rat. Using the classical antidotal therapy (sodium bicarbonate) for comparison, this ligand has been investigated for its ability to remove uranium from rats after intravenous or intramuscular injection as nitrate. Following an immediate single intramuscular or intravenous injection of 3,4,3-LIHOPO (30 mumol.kg-1) urinary excretion of uranium was greatly enhanced with a corresponding reduction 24 h later in kidney and bone uranium content (to about 20 and 50% of the control rat respectively). Under identical experimental conditions, sodium bicarbonate (640 mumol.kg-1) reduced the uranium content in kidney in kidney and bone only to about 90 and 70% of controls respectively, and there was less enhancement of uranium excretion. However, when treatment was delayed by 30 min and administered intraperitoneally, there was no marked difference in retention and excretion of uranium between the two compounds. As this ligand showed no apparent irreversible toxicity at effective dosages, it is concluded that the administration of the 3,4,3-LIHOPO chelating agent represents potentially a most significant advance for prompt treatment of uranium contamination, while a more detailed investigation is necessary on the possible advantage when treatment delayed.

Animals↗

PubMed2003

Gaseous and particulate emissions from a DC arc melter.

Tests treating soils contaminated with metal compounds and radionuclide surrogates were conducted in a DC arc melter. The soil melted, and glassy or ceramic waste forms with a separate metal phase were produced. Tests were run in the melter plenum with either air or N2 purge gases. In addition to nitrogen, the primary emissions of gases were CO2, CO, oxygen, methane, and oxides of nitrogen (NO(x)). Although the gas flow through the melter was low, the particulate concentrations ranged from 32 to 145 g/m3. Cerium, a nonradioactive surrogate for plutonium and uranium, was not enriched in the particulate matter (PM). The PM was enriched in cesium and highly enriched in lead.

Air Pollutants↗

PubMedDate not supplied

The Maralinga Rehabilitation Project: final report.

Maralinga, South Australia was an important site in the United Kingdom nuclear weapons test programme. Seven bombs were exploded and a series of 'safety' tests carried out; the latter in particular disseminated appreciable amounts of uranium and plutonium over a wide area. A programme to clean up the test site over several years was instituted, with in-situ vitrification as a principal measure. The final report on the programme has now been published. However, both the programme and the Report are seriously flawed; this article provides criticisms of both.

Air Pollution, Radioactive↗

PubMedDate not supplied

The nuclear arsenals and nuclear disarmament.

Current world stockpiles of nuclear weapons and the status of treaties for nuclear disarmament and the ultimate elimination of nuclear weapons are summarised. The need for including stockpiles of civil plutonium in a programme for ending production and disposing of fissile materials is emphasized, and the ultimate difficulty of disposing of the last few nuclear weapons discussed.

Humans↗

PubMedDate not supplied

Is technetium-99 (Tc-99) radiologically significant?

According to radiological protection authorities the radioisotope technetium-99 (Tc-99) is not 'radiologically significant' to humans or other species. The Sellafield plutonium reprocessing plant discharges large amounts of Tc-99 into the Irish Sea; by the year 2015 a total of about 3,000 tera-becquerels of Tc-99, weighing about 5 tonnes, will have been discharged. This article considers the effects of Tc-99 on the environment. After discharge, Tc-99 travels large distances in the ocean. Levels of Tc-99 in Norwegian coastal waters increased by ten times between 1991 and 1996. Tc-99 becomes concentrated offshore in seaweed, winkles and mussels. A concentration factor of 120,000 has been reported in seaweed and one of 650,000 has been measured in the green gland of lobster. It may be necessary to reassess the risk to human health following the ingestion of the relevant isotopes, including Tc-99, because of the possibility of radiation induced genomic instability, as well as the cancer risk. The committed effective doses used to determine permitted levels of intake of these isotopes should be increased and the authorized limits for the discharge of radioactive wastes from Sellafield reduced. Authorized limits of the discharge of radioactivity should be based on Contaminated Food Intervention Levels rather than Generalized Derived Limits as they are now.

England↗

PubMed2003

Carcinogenic risk of hot-particle exposures.

It has been suggested that spatially non-uniform radiation exposures, such as those from small radioactive particles ('hot particles'), may be very much more carcinogenic than when the same amount of energy is deposited uniformly throughout a tissue volume. This review provides a brief summary of in vivo and in vitro experimental findings, and human epidemiology data, which can be used to evaluate the veracity of this suggestion. Overall, this supports the contrary view and indicates that average dose, as advocated by the ICRP, is likely to provide a reasonable estimate of carcinogenic risk (within a factor of approximately +/- 3). There are few human data with which to address this issue. The limited data on lung cancer mortality following occupational inhalation of plutonium aerosols, and the incidence of liver cancer and leukaemia due to thorotrast administration for clinical diagnosis, do not appear to support a significant enhancement factor. Very few animal studies, including mainly lung and skin exposures, provide any indication of a hot-particle enhancement for carcinogenicity. Some recent in vitro malignant transformation experiments provide evidence foran enhanced cell transformation for hot-particle exposures but, properly interpreted, the effect is modest. Few studies extend below absorbed doses of approximately 0.1 Gy.

Animals↗

PubMed2005

A respiratory model for uranium aluminide based on occupational data.

As part of an epidemiological study, doses from intake of radionuclides were estimated for workers employed during a 52-year period at the Rocketdyne/Atomics International facility in California. The facility was involved in a variety of research programmes, including nuclear fuel fabrication, spent nuclear fuel decladding, and reactor operation and disassembly. Most of the documented intakes involved inhalation of enriched uranium (U), fission products, or plutonium (Pu). Highest doses were estimated for a group of workers exposed to airborne uranium aluminide (UAl(x)) during the fabrication of reactor fuel plates. Much of the exposure to UAl(x) occurred early in the fuel fabrication programme, before it was recognised that intake and lung retention were being underestimated from urinary data due to an unexpected delayed dissolution of the inhaled material. In workers who had been removed from exposure, the rate of urinary excretion of U increased for a few months, peaked, and then declined at a rate consistent with moderately soluble material. This pattern differs markedly from the monotonically decreasing absorption rates represented by the default absorption types in the Human Respiratory Tract Model (HRTM) of the International Commission on Radiological Protection (ICRP). This paper summarises the findings on the behaviour of UAl(x) in these workers and describes material-specific parameter values of the HRTM based on this information.

Air Pollutants, Radioactive↗

PubMed2001

A genetic screen for suppressors and enhancers of the Drosophila PAN GU cell cycle kinase identifies cyclin B as a target.

The early cell cycles of Drosophila embryogenesis involve rapid oscillations between S phase and mitosis. These unique S-M cycles are driven by maternal stockpiles of components necessary for DNA replication and mitosis. Three genes, pan gu (png), plutonium (plu), and giant nuclei (gnu) are required to control the cell cycle specifically at the onset of Drosophila development by inhibiting DNA replication and promoting mitosis. PNG is a protein kinase that is in a complex with PLU. We employed a sensitized png mutant phenotype to screen for genes that when reduced in dosage would dominantly suppress or enhance png. We screened deficiencies covering over 50% of the autosomes and identified both enhancers and suppressors. Mutations in eIF-5A and PP1 87B dominantly suppress png. Cyclin B was shown to be a key PNG target. Mutations in cyclin B dominantly enhance png, whereas png is suppressed by cyclin B overexpression. Suppression occurs via restoration of Cyclin B protein levels that are decreased in png mutants. The plu and gnu phenotypes are also suppressed by cyclin B overexpression. These studies demonstrate that a crucial function of PNG in controlling the cell cycle is to permit the accumulation of adequate levels of Cyclin B protein.

Animals↗

PubMed2002

Thin layer alpha-Al2O3:C beta dosemeters for the assessment of current dose rate in teeth due to 90Sr intake, and comparison with electron paramagnetic resonance dosimetry.

The use of thin-layer alpha-Al2O3:C thermoluminescent detectors (TLDs) for the assessment of current beta dose rate in human teeth due to 90Sr intake is investigated. The teeth used in this study were collected from members of the Techa river population who were exposed to radiation as a result of releases of the Mayak plutonium production facilities (Southern Urals-Russia) between 1949 and 1956. The beta dose rates from different parts of the tooth (enamel, crown dentine, and root) were determined by storing the detectors over the samples in a shielded environment. The cumulative dose measured by electron paramagnetic resonance (EPR) in different dental tissues is found to be proportional to current dose rate obtained from alpha-Al2O3:C thermoluminescence dosemeters. The retention of 90Sr in various parts of the teeth is discussed.

Aluminum Oxide↗

PubMed2003

Application of Monte Carlo calculations to calibration of anthropomorphic phantoms used for activity assessment of actinides in lungs.

This paper reports on a new utility for development of computational phantoms for Monte Carlo calculations and data analysis for in vivo measurements of radionuclides deposited in tissues. The individual parameters of each worker can be acquired for an exact geometric representation of his or her anatomy, which is particularly important for low-energy gamma ray emitting sources such as thorium, uranium, plutonium and other actinides. The software discussed here enables automatic creation of an MCNP input data file based on computed tomography (CT) scanning data. The utility was first tested for low- and medium-energy actinide emitters on Livermore phantoms, the mannequins generally used for lung counting, in order to compare the results of simulation and measurement. From these results, the utility's ability to study uncertainties in in vivo calibration were investigated. Calculations and comparison with the experimental data are presented and discussed in this paper.

Actinoid Series Elements↗

PubMed2003

Internal dosimetry of uranium isotopes using Bayesian inference methods.

A group of personnel at Los Alamos National Laboratory is routinely monitored for the presence of uranium isotopes by urine bioassay. Samples are analysed by alpha spectroscopy, and the results are examined for evidence of an intake of uranium. Because the measurement uncertainties are often comparable to the quantities of material we wish to detect, statistical considerations are crucial for the proper interpretation of the data. The problem is further complicated by the significant, but highly non-uniform, presence of uranium in local drinking water and, in some cases, food supply. Software originally developed for internal dosimetry of plutonium has been adapted to the problem of uranium dosimetry. The software uses an unfolding algorithm to calculate an approximate Bayesian solution to the problem of characterising any intakes which may have occurred, given the history of urine bioassay results for each individual in the monitored population. The program uses biokinetic models from ICRP Publications 68 and later, and a prior probability distribution derived empirically from the body of uranium bioassay data collected at Los Alamos over the operating history of the laboratory. For each individual, the software creates a posterior probability distribution of intake quantity and solubility type as a function of time. From this distribution, estimates are made of the cumulative committed dose (CEDE) to each individual. Results of the method are compared with those obtained using an earlier classical (non-Bayesian) algorithm for uranium dosimetry. We also discuss the problem of distinguishing occupational intakes from intake of environmental uranium, within a Bayesian framework.

Algorithms↗

PubMed2003

Assessment of doses to the offspring of the Techa River cohort due to intakes of radionuclides by the mother.

The Techa River was contaminated as a result of radioactive releases by the Mayak plutonium production facility in 1949-1956. The residents of riverside communities were exposed to internal irradiation from radionuclides ingested mainly with river water, and also to external gamma irradiation resulting from shoreline and flood-plain contamination. The most important role in population exposure was played by (89,90)Sr and 137Cs. The persons born after the onset of the contamination have been identified as the 'Techa River Offspring Cohort' (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general population to chronic radiation. This report describes the results of the calculation of fetal doses due to intakes of radionuclides by their mothers. Particular attention has been given to fetal dose from 90Sr because this nuclide is the most significant in terms of population dose for the Techa River. The comparison of the fetal bone marrow doses evaluated using different approaches proposed in the literature has shown a large dispersal in dose values. The main cause of this is the difference in model assumptions simplifying some developmental aspects of fetal haematopoiesis and bone formation. This paper presents an analysis of these basic assumptions that could be useful for further improvements in fetal dosimetry.

Body Burden↗

PubMed2001

Biomarkers specific to densely-ionising (high LET) radiations.

There have been several suggestions of biomarkers that are specific to high LET radiation. Such a biomarker could significantly increase the power of epidemiological studies of individuals exposed to densely-ionising radiations such as alpha particles (e.g. radon, plutonium workers, individuals exposed to depleted uranium) or neutrons (e.g. radiation workers, airline personnel. We discuss here a potentially powerful high LET biomarker (the H value) which is the ratio of induced inter-chromosomal aberrations to intra-arm aberrations. Both theoretical and experimental studies have suggested that this ratio should differ by a factor of about three between high LET radiation and any other likely clastogen, and will yield more discrimination than the previously suggested F value (ratio of inter-chromosomal aberrations to intra-chromosomal inter-arm aberrations). Evidence of the long-term stability of such chromosomal biomarkers has also been generated. Because these stable intra-arm anld inter-chromosomal aberrations are (1) frequent and (2) measurable at long times after exposure, this H value appears to be a practical biomarker of high LET exposure, and several in vitro studies have confirmed the approach for unstable aberrations. The approach is currently being tested in a population of Russian radiation workers exposed several decades ago to high- or low LET radiation.

Biomarkers↗

PubMed2005

Shielding analysis at the upper section of the accelerator-driven system.

The proton beam duct of the accelerator-driven system (ADS) acts as a streaming path for spallation neutrons and photons and causes the activation of the magnets and other devices above the subcritical core. We have performed a streaming analysis at the upper section of the lead-bismuth target/cooled ADS (800 MWth). MCNPX was used to calculate the radiation dose from streamed neutrons and photons through the beam duct. For the secondary photon production calculation, cross sections for several actinides were substituted with plutonium because of the lack of gamma production cross section. From the results of this analysis, the neutron dose from the beam duct is seen to be about 20 orders higher than that of the bulk shield. The magnets and shield plug are heavily irradiated by streaming neutrons according to the DCHAIN-SP analysis.

Computer Simulation↗

PubMed2005

A time-dependent dose model for glovebox processing of fissile material.

A new modeling system for high-intensity neutral particle radiation fields is presented. The code PANDEMONIUM calculates external effective dose rates from neutrons and photons produced at specific locations within an industrial-size plutonium processing facility. The new version of PANDEMONIUM introduces time-dependent neutronics for source multiplication coupled with transient source and detector positions. The code is designed to provide quick and acceptably accurate total effective dose estimates for scenarios and facilities for which conventional methods prove to be too impractical or costly to model. The energy range of the code has also been extended to include the effects of prompt-fission photons.

Computer Simulation↗