PURPOSES OF THE MEETING J. Z. Holland Chief, Fallout Studies Branch Division of Biology and Medicine The Division of Biology and Medicine conducts research on biological effects of radiation, on the beneficial uses of radiation and radioisotopes in biology and medicine, and on special biomedical problems arising in the atomic energy program generally. The Fallout Studies Branch of the Division deals with the biomedical problems arising through the introduction of man-made radioactivity into the atmosphere. The research program includes not only studies of the dietary levels, ingestion rates, body burdens and external radiation doses from atmospheric radioactivity and fallout, but also: (1) studies of source conditions which affect the composition and properties of the radioactive materials released, (2) studies of the meteorolog- ical factors affecting the dispersion and deposition of contaminants from sources anywhere in the atmosphere or near space, (3) studies of aerosol physics and chemistry, (4) studies of actual levels of radioactive contamina- tion of the atmosphere and the earth's surface by means of extensive sampling and analysis programs, and (5) developmental projects aimed at improving and extending the sampling and analysis capabilities. We are not engaged in radiation monitoring per se, but with measurements as a source of experimental information to increase our understanding of the phenomena and to test and improve our ability to predict. These studies are conducted in AEC laboratories, in universities and industrial laboratories under contract, and in coordinated and cooperative programs with the Weather Bureau, the Air Force, the Navy, the Defense Atomic Support Agency, and others. Our interest in the upper atmosphere dates back to the first weapons tests, when transport in the upper troposphere was recognized as being related to contamination patterns observed on the ground, Stratospheric studies in the period 1954-1958 were concerned with debris from Ivy, Castle, and Redwing tests and smaller amounts from the UK and USSR tests. During this period Project Ash Can was initiated. While the possibility was recognized that some debris might have been projected to altitudes greater than 100,000 feet, no serious attempt was made to verify this. Firstly, it was hard enough to get interpretable quantitative data in the alti- tude range accessible by simple balloon-borne, fan-driven filter systems. Secondly, only | to 2 percent of the atmosphere, or perhaps 5 to 10 percent of the stratosphere were above our 90, 000-foot sampling limit. Thirdly, the data obtained in Project Ash Can consistently showed a strong decrease in fission product radioactivity upward from 65,000 or 80, 000 feet to the 90, 000-foot level. In the period 1958-1960 the high altitude shots Teak and Orange in Operation Hardtack gave us a new incentive for pushing our sampling altitude capability upward. The addition of rhodium to the Orange device made it possible to trace the debris from this one detonation. A conceptional study contract with the Atlantic Research Corporation resulted in some ideas which you will hear about later, The Air Force Cambridge Research Laboratories, with partial AEC support, have contracted with Aerolab Development Company to