Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “POLONIUM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1993

Relative effectiveness of dithiol and dithiocarbamate chelating agents in reducing retention of polonium-210 in rats.

Nine different sulphur-based chelators, including dithiols and dithiocarbamates, were examined for their ability to remove Po-210 from the rat. In general, treatments merely caused a redistribution of Po-210 in the body. Greatest reduction of Po-210 in blood was achieved by 2,3-dimercaptopropanol (BAL), sodium diethyldithiocarbamate (DDTC), and N-(2,3-dimercaptopropyl) phthalamidic acid (DMPA). Nearly all the compounds tested decreased Po-210 in the spleen and muscle. On the other hand, BAL and DDTC substantially increased the accumulation of Po-210 in the brain while DMPA, DMPS (sodium 2,3-dimercaptopropane-1-sulphonate) and DMSA (meso-2,3-dimercaptosuccinic acid) increased by several times the Po-210 in kidneys. A less pronounced increase of Po-210 was sometimes observed in liver (due to DDTC and DMPA) and in muscle (due to BAL and DDTC). Three of the dithiocarbamates (BGDTC, MeOBGDTC and BLDTC) did not increase accumulation of Po-210 in the brain and muscle but they reduced Po-210 in blood to a lesser degree than DDTC. A derivative of DMSA (Mi-ADMS) reduced Po-210 in blood, bone and muscle more than DMSA, but at the same time increased Po-210 in the kidney. When BAL or DDTC were combined with other agents there was a greater reduction in the whole-body burden of Po-210. Removal of Po-210 from the bone, spleen and kidneys by BAL was increased by repeated treatment. However, under similar experimental conditions the effect of a single injection of BAL on Po-210 in blood was less pronounced when the period of observation was prolonged. Total-body retention of Po-210 could not be reduced to less than 85% of the untreated controls by any of the chelators tested. In spite of this some of them (BAL, DMPS, DMSA, DMPA) could still have a useful role in reducing the toxicity of Po-210.

Animals↗
PubMed1993

Gastrointestinal absorption and retention of polonium in adult and newborn rats and guinea pigs.

The gastrointestinal absorption of 210Po was determined by comparing tissue retention after oral and systemic administration. The results indicate an increase in absorption in adult rats for 210Po administered in liver compared with 210Po nitrate with estimated absorption of 5 and 13%, respectively. For 210Po citrate, values of about 7% were obtained in 1-day-old neonate and adult rats while absorption in guinea pigs was estimated to be about 23% in 1-day-old neonates, 17% in 5-day-old neonates, and 9% in adults. Gut retention of ingested 210Po in neonates was high in rats but not guinea pigs. In adult animals, but not neonates, the liver accounted for a greater proportion of 210Po reaching the bloodstream after ingestion than after systemic injection. The significance of these results is discussed in relation to current assumptions made in the calculation of doses from 210Po.

Administration, Oral↗
PubMed1995

Transfer of polonium to the embryo and foetus of rat and guinea pig.

Transfer of 210Po to the foetus measured 3 days after administration in rat and 7 days later in guinea pig increased with increasing gestational age to about 0.1% injected activity per rat foetus at birth and 0.6% per guinea pig foetus on day 57, corresponding to whole-body foetus:mother concentration ratios of about 0.1:1 in both species. The greatest concentrations of 210Po were measured in the rat yolk sac during its haemopoietic stage, an order of magnitude greater than concentrations in the placenta and two orders of magnitude greater than foetal concentrations. The results obtained have been used to estimate in utero doses to haemopoietic tissues, taking account of transfer to the blastocyst/egg cylinder, yolk sac, liver and bone marrow. The concentration ratios relative to maternal liver for these tissues were taken to be 1, 3, 0.1 and 0.05 respectively and were applied to periods of human gestation of 0-2.5, 2.5-6, 6-12 and 12-38 weeks respectively. For chronic maternal intake by ingestion of 210Po during the year of pregnancy giving a committed effective dose (CED) to the mother of 1 mSv, the total in utero dose to haemopoietic tissue was about 340 microSv compared with a maternal red bone marrow dose of 2.2 mSv. The yolk sac and bone marrow accounted for 66 and 27% of the in utero dose respectively. In addition, the total CED to the offspring was calculated assuming a whole-body foetus:mother concentration ratio of 0.1:1 and that the distribution of 210Po between tissues was the same in the foetus as in adults and children. For chronic intake of 210Po during the year of pregnancy as assumed above, the CED to the offspring was estimated to be 8% of that to the mother.

Animals↗
PubMed1995

Combined chelation treatment for polonium after simulated wound contamination in rat.

Contaminated puncture wounds were simulated in rat by intramuscular injection of 210Po. The aim of the study was to determine the effectiveness of chelation treatment as a function of time, dosage, and route of chelate administration. Ten newly synthesized substances containing vicinal sulphydryl and carbodithioate groups were used and their effect was compared with that of chelators clinically applicable in man--BAL (2,3-dimercaptopropane-1-ol), DMPS (2,3-dimercaptopropane-1-sulphonate), DMSA (meso-2,3-dimercaptosuccinic acid), and DDTC (sodium diethylamine-N-carbodithioate). The results indicate first that complete removal of 210Po from the injection site is achieved by only two local injections of DMPS, beginning as late as 2 h after injection of 210Po. Second, many of the substances used merely induce translocation of 210Po from the injection site into other tissues. Third, a combined local treatment at the injection site with DMPS plus repeated systemic, subcutaneous, treatments with HOEtTTC (N,N'-di-(2-hydroxyethyl)ethylenediamine-N,N-biscarbodithioate), a derivative of DDTC, results after 2 weeks in a reduction of the estimated total body retention of 210Po to about one-third of that in untreated controls. In the latter case the cumulative excretion of 210Po increased from 8 to 54%, mainly via the faeces.

Animals↗
PubMed1985

Radiological health implications of lead-210 and polonium-210 accumulations in LPG refineries.

Radon-222, a naturally occurring radioactive noble gas, is often a contaminant in natural gas. During fractionation at processing plants, Radon tends to be concentrated in the Liquified Petroleum Gas (LPG) product stream. Radon-222 decays into a number of radioactive metallic daughters which can plate out on the interior surfaces of plant machinery. The hazards associated with gamma-emitting short-lived radon daughters have been investigated previously. The present work reports an analysis of the hazards associated with the long-lived daughters; Pb-210, Bi-210, and Po-210. These nuclides do not emit appreciable penetrating radiation, and hence do not represent a hazard as long as they remain on the inside surfaces of equipment. However, when equipment that has had prolonged exposure to an LPG stream is disassembled for repair or routine maintenance, opportunities for exposure to radioactive materials can occur. This paper reports a series of measurements made on an impeller taken from a pump in an LPG facility. Alpha spectroscopy revealed the presence of Po-210, and further measurements showed that the amount on the impeller surface was well above the exempt quantity. Breathing zone measurements made in the course of cleaning the impeller showed that an inhalation exposure equivalent to breathing Po-210 at the Maximum Permissible Concentration (MPC) for 60 hours could be delivered in less than half an hour. It was concluded that maintenance and repair work on LPG and derivitive product stream equipment must be carried out with the realization that a potential radiological health problem exists.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollution, Radioactive↗
PubMed2004

Microdosimetry of astatine-211 single-cell irradiation: role of daughter polonium-211 diffusion.

A microdosimetric analysis of previously published data on 211At-albumin, free 211At, and 211At-C215 irradiation of Colo-205 cells in a slowly rotating single-cell suspension is presented. A custom-built computer program based on the Monte Carlo method was used to simulate the irradiation and the energy deposition in individual cell nuclei. Separate simulations were made for the assumption that the 211Po atom stays in the position where it is created, and that it diffuses away. The mean event number at which 37% of all cells survived, n37, and the frequency mean specific energy per event, zF, were estimated. The Poisson distribution of events and simulated single and multievent distributions of specific energy were used to find the single-cell specific energy at which the probability of survival is reduced to 37%, z37. The calculated single-cell radiosensitivity values show that 211Po atoms, created on a cell surface by the decay of 211At atoms, will diffuse from the cell during its life-span. The increasing distance to the cell nucleus will drastically decrease the probability of the emitted alpha particle to hit the nucleus. This will result in fewer alpha-particle events in the cell nucleus. For dispersed cells, the diffusion of 211Po atoms will reduce the total dose from cell-bound 211At by a factor of 2.

Alpha Particles↗
PubMed2006

Comparison between an unipolar corona charger and a polonium-based bipolar neutralizer for the analysis of nanosized particles and biopolymers.

In this work we present results on the charging efficiency of nanoparticles by means of a corona based unipolar charging unit. This device was designed to replace a Po210 bipolar charger unit in a commercial electrospray aerosol generator (TSI Mod 3480). The charging efficiency has been investigated for negative and positive charged particles of various chemical composition in the size range between 5 and 18 nm. The corona current has been found to be the most influential operation parameter on the charging efficiency. With a positive electrospray droplet charge and a negatively-biased corona needle, a rapidly decreasing yield of singly positively charged aerosol particles with increasing corona current was found. An increasing yield of negatively charged particles was observed with increasing current of the corona process. Providing appropriate corona settings nanoparticles with charge levels similar to these obtained with a Po210 charger were found. At optimal corona settings the yield of singly charged particles was found to be two to four times higher for negative and positive particles compared to bipolar charging. This gain in the charging efficiency increases directly the sensitivity of analysis and enhances all measurement and manipulation processes of airborne nanoparticles for which electrical charging is required.

Biopolymers↗