HUMAN RADIATION INJURY parent that most of this fallout area is beyond the range of destruction by blast or heat, and thus one is dealing with essentially a “pure” radiological situation. The extent and potential seriousness of fallout was clearly indicated inofficial releases of the Atomic Energy Commission (1-+). From these statements, the bomb’s cloud could drop radioactive ashes in a cigar-shaped zone about 220 miles long and 20 to 40 miles wide. There could be sufficient radioactivity in a downwind belt about 140 miles in length and of varying width up to 20 miles to seriously threaten the lives of nearly all persons remaining in the area for 36 hours and who did not take protective measures. The zones thus outlined for potential morbidity and lethality depend obviously on weapon size, wind and other weather condition, etc. Strauss(1) emphasized that possible casualty figures given are for the worst possible situation. Casualties might be reduced greatly in number because many in the area would take shelter or evacuate the area. Also, the pattern of fallout might be spotty in nature, and thus, many would escape exposure. Nevertheless, the area where potentially serious casualties may result may exceed by orders of magnitude the relatively small areas for conventional weapons. 6.33 The Effects of Gamma Radiation From Fallout The gamma radiations are penetrating and, as seen in the Marshallese, produce the same type of injury produced bythe initial radiation from the conventional weapon. In the one case radiation is delivered from a distant source; in the other from essentially a plane field. In both situations, penetrating radiation of the entire body results. Qualitatively, the results are identical. Quantitatively (e. g., dose-effect relationships), there may be differences due to incompletely known and understood differences in the energy of radiation and in dose rate, and in the geometry of exposure (see sec. 6.42). For these reasons, and for additional reasons to be advanced later, instrument readings of roentgen dose measured in air and published dose-effect 97 tables for man should be used only as a rough guide in casualty estimation. For order of magnitude of doses that may be encountered in the fall out area, the following figures for total dose for thefirst 36 hour period, are quoted from chairman Strauss’ release (1). Ten miles downwind from the large device fired at the Bikini Atoll on March 1, 1954, within the test site, a total dose of 5,000 roentgens was delivered over a period of 36 hours. The largest total dose delivered outside the test site was 2,300 r for the same period at the north-west end of Rongelap Atoll about 100 miles from Bikini. Two other areas in Rongelap 110 and 115 miles from Bikini received 2,000 and 150 r respectively. Another area, 125 miles from Bikini received 1,000 r over the 36 hour period. Effects that may be expected for given doses of penetrating radiation given over a few minutes or hours are indicated in Table 6.1 (7). It is emphasized that such tables are derived chiefly from animal data and thus, should be taken as approximations only. These values vary considerably from the British estimates (8). Table 6.1.—Effects of Acute Total Body Irradiation on Human Beings 50 rj/ 100 r 150 r 200 r 300 r 450 r Over 650 r No casualties. No reduction in effectiveness. Two percent may be casualties (nausea and/or vomiting) for short period of time. No evacuation contemplated. No significant reduction in effectiveness. Twenty-five percent casualties in a few hours. First definite reduction in effectiveness. Fifty percent of the casualties in this group will have to be evacuated. All must be evacuated as soon as possible. Fifty percent will be noneffective. Approximately 20 percent deaths. All need evacuation immediately. All are noneffectives. Fifty percent deaths. Lethal dose, but not necessarily for all so exposed.