Arthur R. Schulert

Strontium-90 in Man

The world-wide average strontium-90 content of man was about 0.12 micromicrocurie per gram of calcium (1/10,000 of the maximum permissible concentration) in the fall of 1955. A few values as high as 10 times the average have been obtained. This value is in accord with the predicted value based on fallout measurements and fractionation through the soilplant-milk-human chain. With the present burden of strontium-90, this average level should rise to 1 to 2 micromicrocuries of strontium-90 per gram of calcium by 1970.

Strontium-90 in Man V: The concentration in the bones of children had been dropping, but recent tests will reverse the trend

1) It is now possible to predict the strontium-90 concentration in the world population for specified modes of atmospheric contamination with moderate reliability. For example, the average adult bone level in the eastern United States 5 years after the detonation of a specified quantity of fission products into the lower polar stratosphere can probably be estimated to better than � 50 percent. 2) The concentration of strontium-90 in fetuses reached a maximum of 1.2 micromicrocuries of strontium-90 per gram of calcium in eastern North America and began to decrease significantly in 1960 and 1961. The ratio of the strontium-90 level in the fetus to the level in the average diet of the adult is about 0.08. 3) The average rate of turnover of strontium and calcium in the adult skeleton appears to be about 2.5 percent per year, although there is considerable difference among the various bones of the body. 4) The standard deviation for strontium-90 concentration in a population of urban adults appears to be about 40 percent of the mean. The distribution curve for an interval of from 60 to 0.1 percent of the population may be approximated by the log-normal function. In urban populations of Western culture the concentration for 5 percent of the population will exceed twice the mean, that for 0.1 percent will exceed four times the mean. 5) Cities in the Southern Hemisphere showed levels in bone about half those for cities of Western culture in the Northern Hemisphere in 1960, yet the fallout in the Southern Hemisphere is only one-fourth that in the Northern Hemisphere. This is attributed to differences in diet, with a higher milk component in the Northern Hemisphere. 6) A simple model for the strontium-90 concentration in the bones of young people as a function of their age appears to fit the experimental data. 7) The coefficients of the equation describing the relative contributions of the rate of fallout (direct absorption) and the cumulative deposit (soil up-take) to the strontium-90 concentration in milk have been calculated from the observed data for 1959 and 1960. They are as follows: rate factor A = 0.65 micromicrocurie of strontium-90 per gram of calcium in milk per millicurie of strontium-90 per square mile during the growing season; cumulative-deposit factor B = 0.12 micromicrocurie of strontium-90 per gram of calcium in milk per millicurie of strontium-90 per square mile at the midpoint of the growing season. The predicted levels in milk for 1958 obtained with these coefficients are in excellent agreement with the observed levels. In 1958 and 1959 about half the strontium-90 in milk was attributable to the rate factor, whereas in 1960 the contribution of the rate factor dropped to about 15 percent. 8) Future levels of strontium-90 in man are given (i) for the next decade as a result of the nuclear tests through 1961 and (ii) under the assumption that 1.0 megacurie of strontium-90 is added to the stratosphere of the Northern Hemisphere each year. 9) The radiation doses to the skeleton to be expected from world-wide fallout on the basis of a 3000-megaton (fission yield) war are also given.

Comparative metabolism of strontium and calcium in man

Abstract The metabolic fate of intravenously administered Sr 85 and Ca 45 was studied in man. It was found that the isotopes were somewhat equally divided between bone and soft tissue shortly after administration, but that after four months, more than 99 per cent of the fraction of each isotope remaining in the body resided in bone. The initial specific activity (isotope concentration per gramme calcium) was far greater in soft tissue than bone with the values approaching uniformity in about four months. The retention among the bones in the interval studied was greatest in vertebrae and least in long bone shaft and skull. The bone exhibits no marked preference in the uptake of the isotopes initially. However, as Sr 85 is preferentially excreted by the kidneys, the relative ratio of Ca 45 to Sr 85 remaining in bone gradually increases. The net retentipn of Ca 45 is about 60 per cent whereas that for Sr 85 is about 25 per cent.

Brain Reserpine Levels Following Large and Small Doses of Reserpine-H3

Summary (1) Reserpine randomly labeled with tritium had a time-concentration relationship in liver and brain similar to that observed for reserpine labeled with C14 in the TMBA moiety. (2) Throughout and beyond the entire period of observable pharmacological response, reserpine was found to be present in brain and liver. (3) The concentration of reserpine in the brain varied little during the entire period of observable activity and bore no relationship to the intensity of response. (4) The material present in the brain was indistinguishable from reserpine by paper chromatography.

Strontium-90 in Alaska. Alaskan Eskimos for whom the caribou is a dietary staple have a high strontium-90 concentration.

Strontium-90 concentrations have been determined in a variety of foods used by the native population. Caribou from the tundra carry 10 to 20 times the level of domestic cattle. Eskimos for whom caribou is a staple in the diet are found to have four times the strontium-90 content of the average for the world population of the North Temperate Zone.

Strontium-90 and Cesium-137 in North American Milk

The strontium-90 and cesium-137 concentrations in powdered milk in North America vary roughly with the specific activity of rain. The Sr90/Cs137. ratios in over 800 powdered milk samples taken from 60 stations in North America from 1957-60 have a standard deviation of only 44 percent.