105 HUMAN RADIATION INJURY mainly from material deposited directly on the skin, although beta radiation from the to nuclear devices detonated under different conditions, it is possible to predict from the findings, with reasonable assurance, the chief problems that will result from fallout. These ground, building, or even clothes may contribute to a small degree. Thus, shelter within a building, covering exposed skin areas with clothing and early skin and hair decontamination would go far toward pre- are as follows: The medical problems in the immediate vicinity of a kiloton atomic weapon or a megaton bomb will be essentially similar. Withthe larger weapon, of course, the areas of damage are much larger and, thus, the numbers 2) 3) +) of casualties with venting this hazard. Some degree of internal contamination will occur in persons exposed to fallout. The amounts deposited in the body, however, will be relatively small. It appears certain that no contribution to the acute medical picture seen will result from this cause. It appears also, although data are incomplete, that little or no long-term hazard is likely to result from this cause, particularly if reasonable precautions are taken to avoid excessive inhalation or ingestion of the material. The acute medical problems in the fallout area will be concerned principally with total-body gammaexposure ; some with beta irradiation of the skin. mechanical, thermal, or radiation injury are greatly increased. In addition, with large weapons, an area of fallout can extend for thousands of square miles beyond the range of thermal and blast injury, resulting in gammairradiation, beta irradiation of the skin and a potential internal hazard in the absence of blast or thermal injury. Serious fallout can occur several hours after detonation and at considerable distances. At this late time, the early, very steep fall in dose rate has already occurred andthe doserate falls off at a much slower rate. There may be adequate time for countermeasures and early evacuation or othereffective evasive action will reduce by a large amountthe total dose received. The gamma radiation is by far the most serious hazard in the fallout area. It is penetrating, and exposure can result in the same acute radiation injury observed in tbe Japanese at Hiroshima and Nagasaki. The quantitative dose-effect relationships may be altered because of dose rate and otherdifferences bet ween the two types of exposure. Beta radiation of the skin from fallout definitely can be a problem in the absence of lethal doses of associated gammaradiation. Although late in appearing, the skin lesions may be sufficiently serious to result in a “casualty”. Of equal importance, however, is the consideration of the effectiveness of rather simple countermeasures in preventing the lesions. The lesions apparently result References . Strauss, L. L., A Statement by Chairman and a Report by the U. S. Atomic Energy Commission on “The Effects of High Yield Nuclear Explosions”, February 15, 1955. . Libby, W. F. Address on radioactive fallout to 4th Annual Conference of U. 8. Civil Defense Council, Boston. Mass. 29 Sept. 1955. . Libby, W. F. Address to Washington Conference of Mayors. Dec. 1954. . Libby, W. F. Address in Chicago, June 3, 1955. . The effects of atomic weapons, Superintendent of Documents, U. 8. Government Printing Office, 1950. ant 1) . Oughterson, A. W., and Warren, S.: Medical effects of the atomic bomb in Japan. McGraw-Hill Book, Inc., New York, 1956. . Handbook of Atomic Weapons for Medical Officers. Prepared by the Armed Forces Medical Policy Council for the Army, Navy and Air Force. June, 1951. . Taylor, D. Radiae instrumentation. Instru. 29, 315-322, 1952. J. Sci.