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At least 343 records · Page 19Linked to original sources
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↗
PubMed1982

New sintered thermoluminescent dosimeters for personnel and environmental dosimetry.

We discuss the development of an original method preparing thermoluminescent dosimeters using magnesium borate and calcium sulfate materials activated with rare earths. This method is based upon the effect of sensitized thermoluminescent emission of basic TLD phosphors as well as on the method for producing these in solid form. Our technique resulted in unique TLD's in the form of sintered thermoluminescent dosimeters. For one of these, MgB4O7:RE+, the thermoluminescent response is up to five times more sensitive than non-sensitized magnesium borate thermoluminescent material. The other TLD, CaSO4:RE+, has dosimetric characteristics which stay unchanged and are equivalent with characteristics of the well-known calcium sulfate TLD phosphors. These new types of sintered TLD's are highly promising for personnel and environmental dosimetry.

Borates↗
PubMed1995

Alpha self-absorption in monazite dusts.

Measurements have been made of the self-absorption effects in monazite of alpha particles of the 232Th decay series. Samples of six size fractions of monazite were deposited on filters at different dust concentrations and then the gross alpha activity determined. Self-absorption effects were negligible in monazite particles up to 8 microns diameter provided dust concentrations were less than 1 mg cm-2. Significant self-absorption effects occurred for both larger particle sizes and higher dust loadings. As reported AMAD values in the mineral sands industry range up to 15 microns, which is equivalent to an actual mean size of 8 microns diameter monazite particle, minimal self-absorption occurs in samples collected in air monitoring programs conducted in the industry provided that dust concentrations on the filters are less than 1 mg cm-2.

Absorption↗
PubMed2004

Lichen biomonitoring near Karabash smelter town, ural mountains, Russia, one of the most polluted areas in the world.

Biogeochemical signatures were investigated in transplanted and native lichens near a major pollution source using sensitive multi-element chemical analysis. Transplants were established across a 60 km transect centred on the smelter town of Karabash, Ural Mountains, Russia. Statistically significant trends in element concentrations were recorded, some below one part per million. Fine metal particles are accumulated from pollution aerosols. Prolonged exposure may lead to cellular damage and enhanced accumulation or element loss. 206Pb: 207Pb isotope ratios are similar to those associated with airborne particles in Europe and Russia; an outlier near Kyshtym with a lower ratio indicates a source with a higher 235U : 238U ratio. The method is discrete, sensitive, able to detect short-term pollution episodes and useful for understanding element cycling, which is of critical importance for human and environmental health.

Environmental Monitoring↗
PubMed1986

Distribution and kinetics of injected nickel in the pregnant rat.

Radioactive nickel (Ni) was injected intraperitoneally both carrier-free and in 4 mg/kg body weight of Ni as NiCl2 doses in control and pregnant rats on days 12 and 19 after impregnation. The time-course of disappearance of radioactivity from the tissues and blood of the rat was determined, as well as the degree of incorporation of radioactivity from the injected doses. The maximal uptake of the metal 15 min after injection corresponded to kidney uptake, followed by pancreas, blood plasma and then all other target organs studied. The presence of cold nickel resulted in higher uptake of the metal without much change in the proportion of distribution between tissues. The kinetics of disappearance was similar in all tissues and was little affected by pregnancy, with mean half-lives of about 3-5 h irrespective of doses.

Animals↗
PubMedDate not supplied

[The action of 232Th separately and in combination with heavy and alkaline metal salts on Tradescantia (clone 02)].

The action of 232Th-nitrate in concentration 0.09, 0.18 and 0.36 mg/l (counting on 232Th ion) on water cultures of Tradescantia (clone 02) was investigated. It was found that all investigated concentrations of 232Th showed statistically significant genotoxic effect and increased level of morphological abnormal cells in the stamen hairs of Tradescantia in the absence of modifying action of other metal ions. Synergistic toxic interaction was found between the 232Th in concentration 0.18 mg/l and metal ions for all samples of thawed water. Synergistic genotoxic effect of the combined action of these factors was revealed only at the low total contents of ions of heavy and alkaline metals in thawed water samples. The observed synergistic effects of the combined action of 232Th and metal ions should be taken into account when controlling the radionuclide level in the environment.

Dose-Response Relationship, Drug↗
PubMed2001

Non-combustible waste vitrification with plasma torch melter.

Non-combustible radioactive wastes generated from Nuclear Power Plants (NPPs) are composed of concrete, glass, asbestos, metal, sand, soil, spent filters, etc. The melting tests for concrete, glass, sand, and spent filters were carried out using a 60 kW plasma torch system. The surrogate wastes were prepared for the tests. Non-radioactive Co and Cs were added to the surrogates in order to simulate the radioactive waste. Several kinds of surrogate prepared by their own mixture or by single waste were melted with the plasma torch system to produce glassy waste forms. The characteristics of glassy waste forms were examined for the volume reduction factor (VRF) and the leach rate. The VRFs were estimated through the density measurement of the surrogates and the glassy waste forms, and were turned out to be 1.2-2.4. The EPA (Environmental Protection Agency) Toxicity Characteristic Leaching Procedure (TCLP) was used to determine the leach resistance for As, Ba, Hg, Pb, Cd, Cr, Se, Co, and Cs. The leaching index was calculated using the total content of each element in both the waste forms and the leachant. The TCLP tests resulted in that the leach rates for all elements except Co and Cs were lower than those of the Universal Treatment Standard (UTS) limits. There were no UTS limits for Co and Cs, and their leach rate & index from the experiments were resulted in around 10 times higher than those of other elements.

Chemical Phenomena↗
PubMed2002

Micrometer-sized short-lived radioactive aerosol particles for convenient use in laboratory measurements.

For calibration and testing of radioactive aerosol measuring equipment such as continuous air monitors and cascade impactors, and other research applications, it is helpful to have a convenient and relatively safe means of producing radioactive aerosol particles of controlled size and activity. We describe a technique for producing such particles in the micrometer-diameter size range using electrostatic deposition of radon decay products onto otherwise nonradioactive powders of different sizes. An electric field focuses radon decay products (primarily 218Po) onto the surface of a powdered substrate that is then suspended by a technique such as pneumatic dry dispersion. Only a modest-activity commercial 222Rn source (e.g., containing as little as 10(5) Bq of 226Ra) is required, and issues of radioactive cleanup and contamination are minimized due to the short half-lives (26.8 min or less) of the decay products. We report representative results using powders of glass beads, iron oxide, and iron and gold metals in the size range of 0.3 to 30 microm. Yields for the deposited radioactivity per unit concentration of 222Rn gas were of the order of 5 x 10(-7) Bq (214Bi) per milligram substrate per Bq m(-3) of 222Rn for an electrostatic collection time of 30 min.

Aerosols↗
PubMed2006

Low-activity radioactive materials management at the U.S. Department of Energy.

The U.S. Department of Energy (U.S. DOE) is making significant progress with the cleanup of its legacy radioactively-contaminated facilities and sites left from research and development and production of nuclear materials and weapons. Sites like Rocky Flats, Battelle Columbus Laboratories, Fernald, Mound, Brookhaven National Laboratory, Hanford, and Oak Ridge are faced daily with decisions related to disposition of waste and radioactive material. One key to this success is the disposition of waste arising from cleanup. Most of the generated waste volume has very low levels of radioactive contamination. The waste includes contaminated soil, debris from demolition, or scrap metal and equipment. The cost of disposing of large volumes of waste can be prohibitive, so there is incentive to find innovative ways to disposition wastes. This paper describes the current status of policy development in this area, such as development of a draft programmatic environmental impact statement and monitoring of related rulemaking at the U.S. Nuclear Regulatory Commission. The paper also provides an overview of draft U.S. DOE guidance on control and release of property with residual radioactive material, and site-specific applications of DOE guidance.

Decision Making↗
PubMed1977

Choice of monitoring isotope in double label radioimmunoassays with nonimmunological separation techniques.

We discuss the suitability of some radioactive isotopes as volume markers in radioimmunoassays, from a radiochemical point of view. For three eligible isotopes (22Na, 60Co, and 75Se) we studied the concentration of the marker in the precipitate formed in the separation phase of radioimmunoassays. For all those kinds of separations tested (charcoal, ammonium sulfate, polyethylene glycol, and ethanol), binding or coprecipitation was virtually absent or negligible with 22Na but 75Se was strongly concentrated in the precipitate. Concentration of 60Co occurred only with charcoal and ethanol precipitation. Because heavy metals tend to bind to serum proteins, we conclude that of all radioactive isotopes commercially available only 22Na should be used in radioimmunoassays with nonimmunological separation methods.

Charcoal↗
PubMed1994

[Discrepancies in assessment of radiological exposure level in miners related to the use of various measurement systems].

The contamination of the air with radioactive elements (radon-222 and its decay products) occurs in coal, metal ore and chemical raw materials underground mines. This causes irradiation of the miner's respiratory system with ionizing radiation. In Poland the radiation exposure level is controlled both by the ventilation services of particular mines and by the Nofer Institute of Occupational Medicine in Lodz to the order of the State Sanitary Inspection. The in-mine services collect air samples which are next examined to determine the degree of radiation contamination (environmental monitoring), whereas the Institute uses the method of representative individual dosimetry (the dosimeters are attached to the miners' helmets). The article presents discrepancies in the levels of exposure to radiation in mines, assessed by the in-mine services and the Nofer Institute of Occupational Medicine. The hazard level determined by these services is usually one or even two times lower than that determined by the Institute. The reasons for these discrepancies are discussed.

Air Pollutants, Radioactive↗
PubMed1980

The effect of divalent cations on the mode of action of DNase I. The initial reaction products produced from covalently closed circular DNA.

The effect of different divalent metal ions on the hydrolysis of DNA by DNase I was studied with an assay which distinguishes between cleavage of one or both strands of the DNA substrate during initial encounters between enzyme and DNA. Using covalently closed superhelical SV40(I) DNA as substrate, initial reaction products consisting of relaxed circles or unit-length linears are resolved by electrophoresis of radioactively labeled DNA in agarose gels. Only in the presence of a transition metal ion, such as Mn2+ or Co2+, and only under certain reaction conditions, is DNase I able to cut both DNA strands at or near the same point, generating unit-length linears. This ability to cut both DNA strands is inhibited by such factors as temperature decrease, the addition of a monovalent ion or another divalent cation which is not a transition metal ion, or a reduction in the number of superhelical turns in the DNA substrate. All of these factors lead to a winding of the duplex helix and antagonize the unwinding of the duplex promoted by transition metal ion binding. Transition metal ions may thus convert the DNA substrate locally to a form in which DNase I can introduce breaks into both strands. In the presence of Mg2+, DNase I introduces single strand nicks into SV40(I), generating exclusively the covalently open, relaxed circular SV40(II) as the initial product of the reaction. In the presence of Mn2+, DNase I generates as initial products a mixture of SV40(II) and unit-length SV40 linear DNA molecules, formed by two nicks in opposite strands at or near the same point in the duplex. These circular SV40(II) molecules consist of two types. A minority class is indistinguishable from the nicked SV40(II) produced by DNase I in the presence of Mg2+. The majority class consists of molecules containing a gap in one of the two strands, the mean length of the gap being 11 nucleotides. The SV40(L) molecules produced in the presence of Mn2+ appear to have single strand extensions at one or both ends.

Cations, Divalent↗
PubMed1991

Small mammals as monitors of environmental contaminants.

The merit of using small mammals as monitors of environmental contaminants was assessed using data from the published literature. Information was located on 35 species of small mammals from 7 families used to monitor heavy metals, radionuclides, and organic chemicals at mine sites, industrial areas, hazardous and radioactive waste disposal sites, and agricultural and forested land. To document foodchain transfer of chemicals, concentrations in soil, vegetation, and invertebrates, where available, were included. The most commonly trapped North American species were Peromyscus leucopus, Blarina brevicauda, and Microtus pennsylvanicus. In these species, exposure to chemicals was determined from tissue residue analyses, biochemical assays, and cytogenetic assays. Where enough information was available, suitable target tissues, or biological assays for specific chemicals were noted. In general, there was a relationship between concentrations of contaminants in the soil or food, and concentrations in target tissues of several species. This relationship was most obvious for the nonessential heavy metals, cadmium, lead, and mercury and for fluoride. Kidney was the single best tissue for residue analyses of inorganic contaminants. However, bone should be the tissue of choice for both lead and fluorine. Exposure to lead was also successfully documented using biochemical and histopathological endpoints. Bone was the tissue of choice for exposure to 90Sr, whereas muscle was an appropriate tissue for 137Cs. For organic contaminants, exposure endpoints depended on the chemical(s) of concern. Liver and whole-body residue analyses, as well as enzyme changes, organ histology, genotoxicity, and, in one case, population dynamics, were successfully used to document exposure to these contaminants. Based on information in these studies, each species' suitability as a monitor for a specific contaminant or type of contaminant was evaluated and subsequently ranked. A relationship between contaminant exposure and trophic level emerged. Insectivores (shrews) had the highest levels of contaminants, followed by omnivores (cricetid mice) with intermediate levels, and herbivores (voles) with the lowest levels. A substantial number of these biomonitoring studies using small mammals collectively point to the importance of food habits and habitat of small mammals, and their availability and abundance as factors that should influence species selection for monitoring studies. The type of contaminants under consideration as well as the appropriateness of the endpoints selected are important factors to consider when deciding whether or not to include small mammals in biomonitoring studies.

Animals↗
PubMed2005

The legacy of monazite processing in Brazil.

The exploitation of natural resources containing naturally occurring radionuclides may lead to enhanced levels of radioactive isotope and enhanced potential for exposure to naturally occurring radionuclides in products, by-products, residues or wastes. Such resources include, for instance, monazite, the processing of which, in Brazil, generated a great amount of radioactive residues, being stored in buried concrete tanks, in temporary storage buildings and in sealed trenches. In addition, during the 1980s there were no radiological protection rules concerning the storage and transportation of these kinds of residues. Mineral radioactive residues were used as landfills and the residues of chemical processes contaminated floors and buildings. The decommissioning process and cleaning of old plants have generated tons of wastes that has been added to previously produced wastes. This paper reports and discusses the cycle of monazite in Brazil and its consequences in terms of site remediation and amount of wastes and residues generated and stored.

Brazil↗
PubMed1972

Influence of magnesium and manganese on some biological and physical properties of tetracycline.

Accumulation of (3)H-tetracycline in nonproliferating cells of susceptible and resistant strains of Escherichia coli and Staphylococcus aureus in tris(hydroxymethyl)aminomethane (Tris) buffer (10 mm, pH 7.5) was significantly decreased in the presence of 5 to 40 mm MgCl(2) and increased in the presence of 5 to 10 mm MnCl(2). When the bacteria first accumulated (3)H-tetracycline in plain Tris.HCl, and the metal salts were thereafter added, a prompt decrease or increase in radioactivity of the cells was observed after the addition of Mg(2+) or Mn(2+), respectively. In phosphate buffer (10 mm, pH 7.5), the effect of Mg(2+) was delayed. Three minutes after addition of (3)H-tetracycline, uptake was as in the control cell suspension, but thereafter it dropped rapidly. When (3)H-tetracycline was incubated with Mg(2+) before addition to the bacterial suspension, uptake was scarcely measurable. The addition of Mg(2+) to growing cultures of S. aureus and E. coli caused a marked decrease in susceptibility; in contrast, no increase in susceptibility could be demonstrated when Mn(2+) was added. It was also demonstrated that Mg(2+) and Mn(2+) had distinct influences on the absorption spectrum, the optical rotatory dispersion, the circular dichroism, and the lipid solubility of tetracycline.

Absorption↗
PubMed1990

[Disorders of zinc transport through the ileal epithelium in vitamin A deficiency and ischemia].

By means of histochemical revealing of zinc and applying radioactive isotope 65Zn accumulation, absorption and distribution of cations of this metal in the mucous membrane of the iliac intestine have been studied in chicken, normal, at ischemia and at A-avitaminosis. An essential zinc-depositing ability is peculiar to coverings of mucus upon the intestine epithelium, and among intracellular components--to smooth endoplasmic reticulum. A-avitaminosis and especially ischemia result in increasing permeability of the apical part of the external membrane of epitheliocytes, in overloading of the latter with zinc cations, when they are introduced into the intestine, as well as in decreasing transepithelial transport of zinc. The changes mentioned are accompanied with certain disturbances in the barrier function of the intestinal epithelium.

Animals↗
PubMed2003

Separation and recovery of radioactive and non-radioactive toxic trace elements from aqueous industrial effluents.

An update is presented on liquid membrane-based processes as viable and relevant alternatives to conventional approaches such as precipitation, solvent extraction, ion exchange processes and electrochemical techniques for the removal and recovery of some toxic and/or valuable trace metal ions including some actinides and fission products e.g. U, Am, Y etc and As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn etc from radioactive as well as non-radioactive aqueous waste solutions respectively. In particular, results of experiments aimed at developing supported liquid membrane(SLM)-based process using commercially available porous membranes and indigenously prepared track--etch membranes (TEMs) have been critically examined in laboratory studies to generate basic data needed to evaluate their utility for continuous operation without regeneration. These include effect of pore size, porosity, optimum pore size and their reusability. It is clearly demonstrated that indigenously prepared 10 microm thick TEMs with a porosity in the range of 2-5% give comparable transport rates for metal ions-matching with that of commercial membranes of much higher thickness (160 microm) and higher porosity of 60-85%. The smaller thickness of TEMs more than compensates for their lower porosity. It is shown that because of their well defined pore characteristics TEMs could serve as model supports in SLM studies. By comparing the values of permeability coefficient (P) for TEM and polytetraflouroethylene (PTFE) supports for the transport of Pb2+ chosen as a typical divalent metal ion, and using di-2 ethyl hexyl phosphoric acid (D2EHPA) as the carrier, it is unambiguously proved that diffusion of the metal complex across the membrane is the rate controlling step in metal ion transport in SLM-based processes. An overview of the experimental findings along with future outlook and suggestions for further work are presented in this paper.

Actinoid Series Elements↗