ale Cesium-137 in Various Chicago Foods. (Collection Month January, 1970) S. S. Brar and D. M. Nelson Radiological Physics Division Argonne National Laboratory Argonne, Illinois 60439 Since April, 1961, the 3706 and potassium content of the Chicago portion of Tri-City Diet Sampling Program has been determined!”* in bulk food samples by gamma ray spectrometry using a 4" x 4" Nal (TI) crystal. The individual food components were counted for a minimum of 100 minutes, and from these measurements composite daily and yearly food intakes were obtained. Cesium-137 activity in food, now, is an order of magnitude lower than it was a few years ago; consequently, a new procedure for these measurements has been adopted in order to improve accuracy. The same variety of foods (all fresh vegetables; all fresh fruits, etc.) are composited before measurement, and the samples are counted a minimum of 400 minutes. The results of the January, 1970, quarter are tabulated in Tables I and ITI. * Work performed under the auspices of the U. S. Atomic Energy Commission, TII - 28