-13._ C. Direct Measurement of the Stratospheric Fallout Content. Direct measurement by means of high-flying balloons has shown that the stratosphere does indeed have about the fallout anticipated in it. In addition, it has been found in these meas- surements that the radiocesium, Csl37, occurs at about the same level as Sr90 in millicurie units indicating there has been no serious fractionation of the two fission products by the fallout mechanism. It further points out that the sampling of the stratosphere is a practical matter and that measurements can be made of the stratospheric content of radioactive fallout. Such data should greatly assist the whole study of fallout. D. Radiocesium Assays for the, Biosphere. .. Recently a technique for measuring Cs137 in biosphere samples, weerticularly in human bodies, has been developed by Mr. L. D. Marinelli of the Argonne National Laboratory//. It has been found that about four-millionths of one millicurie is present in an average adult. This corresponds rather well to the expected amount considering the short residence time of radiocesium in the body, which is about 3 months, and the expected precipitation rate, which is taken to be equal as a first approximation, to that of radiostrontium. The radiocesium, of course, constitutes no hazard, amounting in radiation dosage to a small fraction of the amount present in the blood in the form of that received from the ordinary potassium present in the body. active. Potassium is naturally radio- It is interesting further evidence, however, 6/ "General Mills High Altitude Balloon Filter Samples,® 7/ Memorandum by A. P. Hardy and S. Tarras, New York Operations Office, July 2, 1956. "Gamma—Ray Activity of Contemporary Man," Science, 124, 122, July 20, 1956. . (more) -