Deposition of strontium-90 through October 1958; the global deposition of strontium-90 is discussed in relation to the absorption of the isotope by man

It is estimated that the global deposition of strontium-90 increased from 1.9 to 2.6 megacuries during the period from June 1957 to October 1958. During this time the stratospheric reservoir of strontium-90 increased from 1.4 to 4.3 megacuries. Approximately 90 percent of the deposition of debris now stored in the stratosphere will have occurred by 1970. In 1958, the strontium-90 content of powdered milk in the New York area averaged 5.9 micromicrocuries per gram of calcium in comparison with 3.9 micromicrocuries per gram of calcium for the previous year. For this region of the country, the strontium-90 content of milk appears to be increasing in proportion to the strontium-90 content of the soils from which the cows derive their forage. The upper limit of foreseeable contamination in milk can be estimated by assuming that this proportionality will continue until all of the strontium-90 has been deposited from the upper atmosphere. This procedure should yield estimates which tend to err on the side of safety. In this manner, it is estimated that the maximum foreseeable sustained level of milk contamination in the New York area is 11 micromicrocuries per gram of calcium. A child deriving its calcium from dairy sources may be expected to develop a skeleton having 5.5 micromicrocuries per gram of calcium. This estimate is double that made in June 1957 and reflects the increased stratospheric inventory due to U.S.S.R. detonations in 1958. The radiological dose to the skeleton from natural sources such as cosmic rays, radium, potassium, and so forth, is approximately 125 millirems per year. A skeletal burden of 5.5 micromicrocuries of strontium-90 per gram of calcium will deliver a dose of approximately 5.5 millirems per year to the bone marrow. The maximum foreseeable dose from strontium-90 in the New York area is thereby estimated to be about 5 percent of the dose due to natural radioactivity.     

Foliar retention of strontium-90 by wheat

Wheat harvested from the University of Maryland Agronomy Farm in June 1959 contained 20 to 50 micromicrocuries of strontium-90 per kilogram of grain. More than 90 percent of the strontium-90 came from deposition on aboveground plant parts, and less than 10 percent was taken up through the soil. About 1 to 2 percent of the strontium-90 fallout during the time the heads were exposed was retained in the grain.     

Strontium-90 Fallout: Comparison of Rates over Ocean and Land

Measurements of strontium-90 in waters residing on the Bahama Banks for periods between 12 and 180 days suggest that fallout rates onto these waters are substantially the same as the average rates at all fallout collection stations between 20 degrees and 30 degrees north latitude. If the amount of preciptation on the Bahama Banks is reasonably representative of the oceanic areas in this latitude band, our results support the conclusion that the amount of strontium-90 deposited per unit area of ocean surface is within a factor of 2 of that on land.     

Strontium-90: effects of chronic ingestion on farrowing performance of miniature swine

In experiments involving the ingestion of strontium-90 by nearly 800 female miniature swine and extending over three generations, no significant differences in litter size, percentage of stillborn, or birth weight were observed between controls and animals ingesting up to 625 microcuries of strontium-90 per day. At 625 microcuries per day, these animals were ingesting more than a million times the peak value of strontium-90 ever reported in the American diet. Animals on 3100 microcuries per day did not survive the gestation period. From these studies, it is evident that feeding levels of strontium-90 high enough to affect fetal or neonatal mortality in this species will not permit maternal survival long enough for the bearing of young.     

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.     

Ability of some Black Sea organisms to accumulate fission products

The coefficients of accumulation of strontium-90, cesium-137, and cerium-144 in seaweeds, eelgrass, actinia, mollusks, and crustaceans are presented. The discharge of strontium-90 into sea water from decomposing seaweed and the retention and additional absorption of cesium-137 and cerium-144 onto organic debris is discussed. Some observations are made about the ability of these elements to diffuse into sea water and about the relative hazard to man from strontium-90 and cerium-144 in marine life.     

Strontium-90 in hair

The hair of rats injected with strontium-90 retains a significant amount of the radionuclide. Although the strontium-90 content of hair is variable in these rats and appears to be subject to a variety of influences, determination of the radionuclide content of hair may offer a nondestructive method of estimating strontium-90 in bone.     

Strontium-90 deposition in New York City

Measurements of strontium-90 deposited in New York City over the past 12 years make for broader understanding of the fallout phenomenon. The data indicate a stratospheric half-residence time of 8 to 10 months. The seasonal oscillation of strontium-90 fallout is very symmetrical and consistent from year to year and completely independent of the timing and magnitude of nuclear tests. The predicted fallout of strontium-90 in 1970 is less than 1 percent of that during the peak year 1963.     

Transport of Strontium-90 in Runoff

Only a small portion of the strontium-90 that fell on cultivated soils was removed in runoff. The concentration of strontium-90 was usually about 10 times higher in the soil carried by the runoff than in the soil from the plow layer of the plots. Thus, a considerable concentration of Sr(90) could occur in areas where runoff sediments accumulate.     

Contribution of Hardtack debris to contamination of the air during 1959

A comparison of the concentrations of tungsten-185 and strontium-90 in the air at various times after the 1958 U.S. nuclear tests in the Pacific indicatesthat debris from this test series contributed less than 10 percent of the total Sr(90) content of the ground-level air at Miami and Washington during the spring of 1959.     

Strontium-90 Accumulation on Plant Foliage During Rainfall

Accumulation of strontium-90 in field-grown crops was measured during the spring of 1962. Each rainfall markedly increased the strontium-90 content of the crops, except when the plants were very small. Accumulation between rains was comparatively small, about equal to the expected uptake from the soil.     

Strontium-90: concentrations in surface waters of the Atlantic Ocean

From the large body of analyses of strontium-90 in surface waters of the Atlantic Ocean, annual average concentrations (from 10 degrees N to 70 degrees N) have been compared to those predicted. The data indicate higher fall-out over ocean than over land and confirm the rapid rates of down-mixing shown by most studies of subsurface strontium-90.     

Europium-155 in debris from nuclear weapons

The lithium-drifted germanium detector enables determination of europium-155 on a routine basis in environmental samples contaminated with debris from nuclear weapons. From measurements of europium-155, cesium-144, and strontium-90 in air filters collected between 1961 and 1966, the yield of europium-155 from weapons was estimated at 1400 atoms per 10(6) fissions, which is close to the yield of europium-155 from fast fission of uranium-238.     

Strontium-90 content of deciduous human incisors

The concentrations of strontium-90 in deciduous incisor teeth of children born in St. Louis between 1949 to 1957 are in accord with estimated bone levels, suggesting that human deciduous teeth are useful as an index of strontium-90 accumulation during the time the teeth are formed.     

Distribution of strontium-90 in a 1959 wheat sample

At least 22 percent of the strontium-90 found in a sample of wheat harvested in 1959 was due to direct deposition. Twenty-seven percent of the total strontium-90 content of this wheat sample was contained in the outermost bran layer.     

Fallout from nuclear detonations of February and April 1960

A sharp increase in the ratio of strontium-89 to strontium-90 in rain was observed at Fayetteville, Arkansas, after the French nuclear detonations of February and April 1960. Experimental data obtained suggest the possibility that part of the debris from atom bombs detonated in the tropical region may enter the stratosphere.     

Fallout from the Chinese nuclear explosion of 17 June 1967

Low-level activities of iodine-131, barium-140, and strontium-89 were found in a series of rain samples collected at Fayetteville, Arkansas, during the period from late June through August 1967. The ratios of these short-lived isotopes to strontium-90 were determined as accurately as possible. The data indicate that the debris from the Chinese nuclear explosion was injected primarily into the stratosphere.     

Strontium-90 concentration factors of lake plankton, macrophytes, and substrates

The ratio of concentration of strontium-90 in living and inert lake components to that in lake water (concentration factors) was determined for plankton, macrophytes, and substrates in eutrophic, mesotropric-eutrophic, and dystrophic Latgalian lakes. Concentration factors of strontium-90 in aquatic organisms and substrates are higher in a dystrophic lake than in the other types.     

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 Sr(90)/Cs(137). 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.     

Mass-yield distribution of the fission products in fallout from the 14 may 1965 nuclear explosion

Twenty single particles separated from a 20-liter sample of rain collected in Osaka, Japan, shortly after the 14 May 1965 test explosion of the Chinese nuclear device, were analyzed radiochemically. The abundance pattern of the fission products in these particles resembled the shape of the mass-yield curve for the thermal neutron-induced fission of uranium-235, except for the facts that cesium-hl37 and strontium-90 were markedly depleted and the yields near the symmetric fission region appeared to be somewhat enhanced.