tal In contrast, tne Caroline 1) Islands, immediately west of the are comprised of high volcanic islands with fringing coral reefs, as well as coral atolls and islands. The high island soils contain *?7Th and 773U and their daughters. Tae additional contributions of gamma emitters among these racionuclidces result in background exposure rates (at 1 meter above the ground) which are nearly a factor of two higher than those similarly measured on the coral atolls (Table 1}. Con- tributions of stratospheric and tropospheric fallout are, of - Oo rn oO WN superimposed cn these natural background radiation sources. rd course, Data for this study were obtained during three field trip years (1975, 1972 and 1980). The first of the field trips was QO he ct rn fo avs aw fo ° th conducted jointly with the University of Washington, Laboratory n Ecology (LRE), which was responsible for determining background concentrations of fallout radionuclides in soil and adoratory ~ (BNL) was Brookhaven National tasked with the measurement of external cund radiation. Subsequent field trip activities focused 4 Ch Va w uo t in terrestrial and marine biota (7). om external radiation measurements only. The measuriment sites were generally restricted to the District T he Trust Territory Lisnmed region whichn encomnassed ' .#) in" ao fo Go ee rs sh oO t ct fete ~ fu eet ral ‘ 3 2 ¢ ry teeir accessibility via commercial airline. yu Ww _— Centers of the Trust Territory of the Pacific Islands because or