as well areas, as ths treat Combine to make evaluations of local fallout contribu- ‘lany small-scale radiological surveys were conducted during lands; 3 red the northern Marshail Wn the 1950's and 1969's at or near the Pacific testing areas in nowever, definitive evaluaticns of the impacts of residual fallout radioactivity were not made until the 1270's {1-3}. These evaluations were conducted on those islands known or suspected to be contaminated by tropospheric fallout from the tests at Bikini and Enewetak Atolls. Pacific were conducted on a small scale during the testing vears (1945- T r 1979, and 1980 by Brookhaven National Laboratory as well. ~~] and thereafter in 19 O A @ 1958) by the University of Washington, “/1 Environmental studies of peripheral areas in the central studies vielded significant data on bacxground radiation levels in these areas, and form the basis for this report. The Marshall Isiands are all comprised of coral atolls or partially drowned atolls formed by coral limestone accretions on subsiding volcanic bases. Drilling studies at Enewet2k established that the limestone cap may exceed 1280 meters in thickness (6). As a result, the contributions of the uranium t tb 7) remote from th2 tast Oo a) FA External background radia ui raciati ho by cosmic w h- islands GQ ~ those a > are virtually nil. ct and thorium series tothe radiation environment in the Marshalls sites levels are on dominated , Sane fron fea YORk, contributions upplemented: by small =

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