Transfer Of Strontium Research Articles

Strontium biokinetic model for the pregnant woman and fetus: application to Techa River studies

A biokinetic model for strontium (Sr) for the pregnant woman and fetus (Sr-PWF model) has been developed for use in the quantification of doses from internal radiation exposures following maternal ingestion of Sr radioisotopes before or during pregnancy. The model relates in particular to the population of the Techa River villages exposed to significant amounts of ingested Sr radioisotopes as a result of releases of liquid radioactive wastes from the Mayak plutonium production facility (Russia) in the early 1950s. The biokinetic model for Sr metabolism in the pregnant woman was based on a biokinetic model for the adult female modified to account for changes in mineral metabolism during pregnancy. The model for non-pregnant females of all ages was developed earlier with the use of extensive data on 90Sr-body measurements in the Techa Riverside residents. To determine changes in model parameter values to take account of changing mineral metabolism during pregnancy, data from longitudinal studies of calcium homeostasis during human pregnancy were analysed and applied. Exchanges between maternal and fetal circulations and retention in fetal skeleton and soft tissues were modelled as adaptations of previously published models, taking account of data on Sr and calcium (Ca) metabolism obtained in Russia (Southern Urals and Moscow) relating to dietary calcium intakes, calcium contents in maternal and fetal skeletons and strontium transfer to the fetus. The model was validated using independent data on 90Sr in the fetal skeleton from global fallout as well as unique data on 90Sr-body burden in mothers and their still-born children for Techa River residents. While the Sr-PWF model has been developed specifically for ingestion of Sr isotopes by Techa River residents, it is also more widely applicable to maternal ingestion of Sr radioisotopes at different times before and during pregnancy and different ages of pregnant women in a general population.

Strontium biokinetic model for the lactating woman and transfer to breast milk: application to Techa River studies

This paper presents a biokinetic model for strontium metabolism in the lactating woman and transfer to breast milk for members of Techa River communities exposed as a result of discharges of liquid radioactive wastes from the Mayak plutonium production facility (Russia) in the early 1950s. This model was based on that developed for the International Commission for Radiological Protection with modifications to account for population specific features of breastfeeding and maternal bone mineral metabolism. The model is based on a biokinetic model for the adult female with allowances made for changes in mineral metabolism during periods of exclusive and partial breast-feeding. The model for females of all ages was developed earlier from extensive data on 90Sr-body measurements for Techa Riverside residents. Measurements of 90Sr concentrations in the maternal skeleton and breast milk obtained in the1960s during monitoring of global fallout in the Southern Urals region were used for evaluation of strontium transfer to breast and breast milk. The model was validated with independent data from studies of global fallout in Canada and measurements of 90Sr body-burden in women living in the Techa River villages who were breastfeeding during maximum 90Sr-dietary intakes. The model will be used in evaluations of the intake of strontium radioisotopes in breast milk by children born in Techa River villages during the radioactive releases and quantification of 90Sr retention in the maternal skeleton.

Determination of 137Cs, 90Sr, 40K radionuclides in food grain and commercial food grain products

Following up transfer of strontium from soil to plants requires determination of isotope in the surface layer of soil and a chosen plant. The most endangered food products are plants including commonly grown grain, which constitutes a basic feeding component for both people and animals. Indeed large amounts of 137 Cs, 90 Sr get into organisms of people and animals with the food, therefore determination of radioactivity of elements in food products and animal fodder is very essential. Choice of proper diet allows to limit the level of human organism denaturation. The aim of this paper was to study relocation of 90 Sr, 137 Cs, 40 K isotopes from soil to grain and then from grain to food products. There were investigated soil, wheat, barley, groats, flour, macaroni and breakfast flakes. Based on the obtained results there were calculated effective weighted doses (nSv) from consumption of 1 kg of a product for different age groups.

Reconstruction of 90Sr intake for breast-fed infants in the Techa riverside settlements

The Techa River (Southern Urals, Russia) was contaminated as a result of radioactive releases by the Mayak plutonium production facility during 1949-1956. 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 parent population to chronic radiation. The purpose of the present investigation is the estimation of (90)Sr intake from breast milk and river water in the period from birth to 6 months of life, necessary for an infant dose calculation. The investigation is based on all available data concerning radioactive contamination due to global fallouts and Mayak releases in the Southern Urals where extensive radiometric and radiochemical investigations of human tissues and environmental samples were conducted during the second half of the twentieth century. The strontium transfer factor from mother's daily diet to breast milk was estimated as 0.05 (0.01-0.13) d L(-1). Based on this transfer factor and data on (90)Sr water contamination, the average total (90)Sr intake for an infant born in the middle Techa River region was found to be equal to 60-80 kBq in 1950-1951. For the same period, calculations of (90)Sr intake using ICRP models gave values of 70-100 kBq. From 1952 onwards, the differences in intakes calculated using the two approaches increased, reaching a factor of 2-3 in 1953. The Techa River data provide the basis for improving and adapting the ICRP models for application to Techa River-specific population.

Ion uptake into demineralized dentine from glass ionomer cement following pretreatment with silver fluoride and potassium iodide

Diamine silver fluoride (Ag(NH3)2F), referred to as AgF, has been shown to provide a pronounced antimicrobial action against caries. The clinical application of this material has been limited by the staining associated with both teeth and tooth coloured restorative materials. The application of potassium iodide (KI) after AgF eliminates stain formation. The purpose of this study was to determine if a prior application of silver fluoride and potassium iodine to demineralized dentine affected the uptake of strontium and fluoride from a glass ionomer cement restoration. Three cavities were prepared in each of five recently extracted human third molars. The cavities were demineralized and treated as follows. In each tooth, one cavity was left as a control, one cavity was restored with glass ionomer cement and one cavity was treated with 1.8M AgF and a saturated KI solution and then restored with glass ionomer cement. The penetration of the various elements into demineralized dentine was measured by their relative percentage weights using electron probe microanalysis (EPMA). Fluoride uptake was significantly higher in the AgF and KI treated samples compared to the other two samples and significantly higher in the glass ionomer restored sample compared to the control. The application of AgF and KI did not significantly interfere with the transfer of strontium from glass ionomer cement into dentine. Silver and iodine deposits were present in the demineralized dentine treated with AgF and KI. The application of AgF and KI onto dentine prior to the placement of glass ionomer cement did not significantly affect the strontium uptake into the subjacent demineralized dentine and the fluoride levels in this zone were significantly increased.

Fallout strontium and caesium transfer from vegetation to cow milk at two lowland and two Alpine pastures

Vegetation-to-milk transfer coefficients for 137Cs, 90Sr and stable strontium were determined for cows grazing on two intensively managed lowland pastures and two Alpine pastures in Austria. The 90Sr transfer coefficient at the four pastures ranged from 0.0005 to 0.0012 dl −1 and correlated with the stable strontium transfer coefficient (0.0006 – 0.0013 dl −1) with the lower values found on the intensively managed pastures. The 137Cs transfer coefficient ranged from 0.0009 – 0.0045 dl −1.

Phytoremediation of Chernobyl Contaminated Land

Most of the land within a 10 km radius of the Chernobyl Nuclear Plant is still heavily contaminated by the 1986 accident. In 1998, a 3 year investigation of the potential of willow vegetation systems to stabilise the contaminated land and thereby reduce the dispersion of radionuclides was initiated under the PHYTOR project. During the first year, a number of screening tests were carried out on the contaminated flood plain of the river Pripyat. Survival of new willow plantations was tested at several locations. Except for the predominantly moist peaty soil in the vicinity of Yanov (where survival was nearly 100%), survival was low (0-30%). Notwithstanding, willows are found everywhere on the Pripyat flood plains: 7-8 year old plantations exist on the upper terraces and 1-2 year old saplings cover the newly deposited alluvial sands. For these willows radiocaesium transfer factors ranged from 10-4 and 10-3 m2.kg-1 and strontium transfer factors from 10-3 and 10-2 m2.kg-1. Biomass production was low: 70-100 kg.ha-1.y-1. Therefore, the radionuclide immobilisation in the biomass was insignificant. Even when based on the exchangeable caesium fraction, less then 0.1% for radiocaesium and less than 1% for radiostrontium became incorporated into the wood. Nevertheless, establishment of willow would reduce resuspension and erosion of soil and sediment.

Strontium Transfer from Maternal Skeleton to the Fetus Estimated on the Basis of the Techa River Data

Measurements of 90Sr in human bone of inhabitants of the Techa river region were started in 1951, and since 1974 the Techa river population has been studied with a whole-body counter. One of the dosimetric tasks that could be decided using data on 90Sr measurements is direct evaluation of strontium transfer to the fetus from the maternal skeleton. Six cases were selected for which 90Sr measurements were available both for stillborn infants and their mothers. The ratio of 90Sr concentrations in fetal bone to maternal bone for the year of pregnancy has been evaluated. Two clusters of values were found and the difference between clusters could be explained by age-dependent features of maternal bone formation and remodelling. When the mother's 90Sr intake occurred in the period of intensive compact bone growth, the transfer coefficient was very low (0.012-0.032). If 90Sr ingestion occurred during the woman's reproductive age, the transfer to fetus was equal to 0.21-0.26.

Models for the transfer of radionuclides in cattle for use in radiological assessments

In performing assessments of the radiological impact of releases of radioactive materials to the environment, mathematical models are required to enable the transfer through various parts of the environment and hence the dose to man to be predicted. The nature of the models and their degree of complexity depend largely upon the particular applications in which they are to be used. Two types of model of differing degrees of complexity for predicting the transfer of strontium, caesium and iodine in cattle have been developed at NRPB. They form part of a general model for the transfer of radionuclides through terrestrial foodchains. The first is a relatively simple model based on the use of equilibrium transfer factors, while the second is an improved but more complex model which incorporates the extra features necessary to provide a reasonable representation of the time dependence of transfer to milk and to meat. Comparisons of the results using the two types of model in some situations of radiological interest have been performed. From these comparisons conclusions have been drawn about the adequacy and pertinence of the use of each model type in different situations.

Influence of lead on calcium and strontium transfer through the duodenal wall in rats

Five-week-old female albino rats were given daily doses for 1 or 2 weeks of lead as acetate ranging from 2 μg to 40 mg by gastric intubation and sacrificed on the 8th or 15th day of the experiment. Calcium-45 and 85Sr were used as markers to assess the calcium and strontium transfer through the duodenal wall by the everted gut sac method of Wilson and Wiseman. Doses of lead acetate greater than 20 μg per day decreased the transfer of both calcium and strontium across the duodenal wall and these transfers decreased further with increased doses of lead, an effect which was independent of whether the rats were killed on the 8th or 15th day of the experiment. Doses of lead acetate greater than 200 μg per day, however, did not produce a further decrease in these transfers. The retention of both calcium and strontium in the intestinal wall was unaffected by the lead treatment.

Second International Conference on Strontium Metabolism

The main object of the work was to study the mechanisms of discrimination in the transfer of strontium and calcium across biological membranes. 3. The experimental work was done in rats and in human subjects using radioactive and stable tracers and intravenous and oral doses of stable strontium. All experiments were carried out under in vivo conditions. 4. The studies using the rat as experimental animal investigated the passage of stronttum-85 with respect to calcium-47 across the gastrointestinal membrane from the bloodstream to the intestine. The isotopes were given intravenously and the rats were examined both feeding and fasting. From the first study which was over a 24 hour interval it appeared that strontium was excreted to a slightly greater extent than calcium into the intestine during feeding. When the rats were fasted, less of both isotopes was excreted by this route although the difference between strontium and calcium was increased. The Sr/Ca faecal excretion ratio increased from 1.2 in the feeding rats to 2,2 in the fasting animals, Intravenously administered strontium-85 was excreted equally in urine and faeces - approximately 10% of the dose by each route of excetion. Calcium-47 however was mainly excreted in stool (approximately 8%) while less than 1% was excreted via the kidney. Fasting caused reduced levels of both 85Sr and 47Ca in the urine. These excretory differences resulted in (a) greater bone deposition of 47Ca than 85Sr both during feeding and fasting and (b) greater levels of both isotopes in the skeleton of the fasting rats than of the feeding animals. A second rat study was performed to investigate the effect of time on the distribution of the isotopes compared to the 24 hour study. In this case animals were sacrificed at 0.5, 1, 2 and 4 hours after injection of the dose. The results of this experiment indicate that calcium is excreted into the intestine slightly faster than strontium and the differences between 85Sr and 47Ca at 24 hours were due to discrimination in reabsorption by the gut. It appeared that there was little difference between the isotopes between 1 and 4 hours. In fasting the reabsorption of the secreted isotopes was greater than during feeding. The passage of strontium with respect to calcium across the human placenta was investigated. Neutron activation techniques were used to measure stable strontium and flame emission spectrometry for calcium. It was shown that calcium passes more readily than strontium across the membrane from mother to child by a factor of about 2. The concentration of calcium in the serum of the newborn was about 20% higher than that of the mother. The effect of stable strontium on the excretions of strontium and calcium was studied in man during both oral and intravenous administration of the element. It was shown that a large dose of stable strontium administered orally was similarly distributed in the excretions as was the trace level of an average diet. Retention of such a dose was for a short period of time in a subject who had no error in calcium metabolism. Intravenously administered stable strontium was mainly excreted via the kidney. Ammonium Chloride and Aluminium Phosphate Gel have been used in attempts to modify stable strontium excretion but with little success. Both intravenously and orally administered stable strontium had a marked effect on the urinary calcium excretion. This was reduced to about half of the normal level when strontium was administered by either route.

Autoradiographic study of the histolocalization of Sr 85 in the newborn mouse

Autoradiographic methods were used to determine the histolocalization patterns and concentration of internal conversion and Auger electron emitting Sr 85 in the newborn mouse. Pregnant Swiss albino mice were given Sr 85Cl 2 during the last trimester of gestation. Some of the young were section-delivered to observe the distribution of strontium relative to the foetal position within the uteri. The localization and quantitation of radioisotope varied in litter mates, but did not coincide with the foetal position. Discrete localization was, however, consistently observed in the mineralizing matrices of bone and the dentine of developing incisors. Mouse litters from “cold” mothers nursed by “hot” mothers demonstrated detectable radiation in their bones and teeth, indicative of strontium transfer via lactation. In mice killed from 15 min to 4 hr after Sr 85 administration and whose tissues were processed routinely or cut in a cryostat and kept frozen to minimize isotope diffusion, no autoradiographic grains were observed over cellular elements, thus eliminating the possibility of a cellular pathway for Sr 86 to mineralizing structures.

Placental Transfer of Strontium 85 in Mice

Placental Transfer of Strontium 85 in Mice

The loss of radioactive isotopes from the leaves of plants in dry conditions

When radioactive isotopes are applied to the foliage of plants varying amounts of the isotopes may be subsequently lost from the plants when they are kept in dry conditions. Losses appear to be greatest in good growing conditions in the summer. It has been possible to demonstrate the transfer of strontium 89 to uncontaminated plants and to trap it in air filters. It is suggested that materials might be lost from leaf surface in association with small wax particles, but no conclusive evidence is available.

Distribution of Radiostrontium and Radiocesium in Milk and Milk Products

A study was conducted to determine whether radioactive milk manufactured into butter, cheddar cheese, and cottage cheese would produce a less contaminated food. The results show a low degree of transfer of strontium and cesium from whole milk to butter. In the case of cheddar cheese and cottage cheese no marked reduction in the transfer of strontium was noted. On the other hand, the transfer of cesium was markedly reduced in both cheddar and cottage cheese. It is concluded that manufacturing techniques can be developed making it possible to utilize most of the potential food value of radioactive contaminated milk in a form lower in radionuclide content than the parent raw milk. (Public Health Eng. Abstr., 42: No. 9, Sept. 1962)