iv WORLDWIDE EFFECTS OF ATOMIC WEAPONS increase the megaton “limits” (1.e., decrease the apparent hazard) as calculated herein. | On the other hand, certain natural factors and concepts regarding the mechanism of the Sr”” path into the human body have also been revised. For example, the original assumption regarding the amount of avatlable natural strontium in the soil is evidently too high; the effect of Jowering this value ts to decrease the megaton “limits.” In fact, the SUNSHINE “limit,” as recently estimated by W. F. Libby,* is lower than that given in this report. It is emphasized that absolute values, both biological and physical, given in this report must stand corrected in the ltght of investi- gations conductedsince 1953. Several of the speculative aspects of the report were recorded without the advantage of the data that have accumulated since the inception of the SUNSHINE experimental program. Some of the conclusions have withstood the test of time; others undoubtedly require modification on the basis of the SUNSHINE experience of the past 3 years. ACKNOWLEDGMENTS Project SUNSHINE was undertaken at the request of the U.S. Atomic Energy Commission; it was jointly sponsored by the AEC (Contract AT (11-1)-135) and USAF Project RAND (Contract AF 33(038)-6413). The inittal, intensive, summer effort was led by Willard F. Libby of the Institute for Nuclear Studies, University of Chicago.* A large part of this preliminary report was developed from Dr. Libby's suggestions. We gratefully acknowledge his assistance. The summer study was climaxed by a RAND-SUNSHINE conference held July 21--23, 1953. At the conference, data and conclusions were discussed with a number of experts who represented a variety of professional interests; we have used their comments where applicable in this report. The conference attendees were: Adams, C. E. Bacher, R. F. Bell, C. Bethe, H. A. Bugher, J. C.. M.D. Cadle, R. D. Claus, W.D. Comar, C. L. Coons, Maj. R. D. Crowson, Col. D. L. Edinger,J. G. Fisenbud, M. English, S. G. Gilmore, F. R. Naval Radiological Defense Laboratory California Institute of Technology Harvard University Cornell University Atomic Energy Commisston Stanford Research Institute Atomic Energy Commmisston University of Tennessce Air Research and Development Command Air Research and Development Command University of California Atomic Fnergy Commission Atomic Energy Commission California Institute of Technology CGrigos T) T University of California Grossman, B. Air Force Cambridge Research Center Gwynn, Lt. Col. P. S. Arined Forces Special Weapons Project *Now Commissioner, U.S. Atomic Energy Commission.