EXTERNAL UX)’OSURE A value of .73 Rads in tissue of interest per Roentgen measured in air at one meter above the surface was used to convert exposure in air to absorbed dose . . : : 37 The source was assumed to be an exponential distribution of i Cs ac- in tissue. tivity with depth in soil, typical of aged fallout (Be70). Because of the multidirectional nature of the source, variation of absorbed dose with depth of organ was minimal. Additionally, external doses were adjusted for living pat- tern variutions since the atolls present a heterogeneous exposure rate environ- ment (Gr77). External e:posure calculations are based on figures 24, 25 and 26 which * were derived from data listed in Cr56, Sh57, Un59, and Gr77. The area under straight line portions of the curve was determined by ye eteBh , ntl (6) where X = external exposure during straight line interval, oR, R, = exposure rate at the end of the interval, mh¢, Ry = exposure rate at the beginning of the interval, mkh?, ty = time .sc¢ detonation at ty = tine +» osc detonation at the beginning >: interval, hours, n slope = Data fr.,. nean ta] Utirit:, the end of interval, hours, of a straight line. 1] detonations during May, June and July of 1958 (Sh57) indicated a out deposition exponent of 18.*. This mean value was observed at kon; lap, Parry and Wotho and applied to early time post detonation of 23