EVENT AND DESCRIPTION OF EXPOSED GROUPS relationship to the surface dose and depth dose as does the air dose measured in a “point source” beam in the clinic or laboratory. It would 9 source” beam air doses with comparable bio- logic effect are obtained: Rongelap, Group I._-_---- 260 Yr appear under these circumstances and in most Ailinginae, Group [I____---- 100 r experimental conditions that the midline dose, Rongerik, Group III ------ 120 r rather than dose measured in air, would be the Utirik, Group IV__--_-_---- 20 r r| : 4m EXPOSURE, c MANY SOURCES 5 RATIOIS6 | BILATERAL EXPOSURE, DIVERGING SOURCE 1.35 oe 59% , 2 a an } L a PER CENT AIR DOSE AT SURFACE i00 0 5 Id 15 20 25 30 36 CM MASONITE DEPTH DOSE DISTRIBUTION IN CYLINDRICAL PHANTOM, co FACILITY, (NMRI) FIGURE 1.4—Comparison of depth dose curves in masonite phantoms from bilateral exposure to a single point source, and simulianeous exposure to multiple sources with a aspherical distribution around the phantom. better common parameter in terms of which to predict biological effect. On this assumption, the air dose values stated in Table 1.1 should be multiplied by approximately 1.5 in order to compare their effects to those of a given air dose from a “point source” beam geometry delivered bilaterally. If this is done, assuming a fallout of 12 hours, the following “point 381712 O—56-——2 500 .tGa ro The geometry of radiation from a fallout field is not identical either to the geometry of bilateral point sources or spherically distributed sources since the plane source delivers the radiation largely at a grazing angle. However, the total field situation is better approximated by solid than by plane geometry. Exposure geometry in a radioactive cloud would be spherical.