“i DISCUSSION The body-burden and urine data indicated a Ghat (nha CHL LB definite decline with ume from the dayof return atom ingestion rate for "Cs. °Zn. “Co and citgy indicated a decline. These measurements of in- t 1 ak a rauo “Sr. The data for “’Pu were uncertain but MAR OUR be The, OMAR Th be idard clive yk 2e k's Se nee nme ee ntro. with adult “Fe. diet. The data for directly measured bodybur- adult Jatea Fig. ~. Exposure-raie hrivory at Rengelap Atoll. GUBR ACE on this ingestion rate, it was estimated that “Fe ghee hi t ME Tee OOve ot adult average body burden for each atoll. an 78 xD YoRE the} al TAME BLT So-AB ToT Uy - pe“185. mes 2hr they 10° ind, Fic. 8 Exposure-rate history at Uumk Atoll. These values were based on the exposure-rate history for each island and do not include the exposure contribution before rehabitation or from natural background radiation. The back- 4). The assumption that & = 0 for “Fe was made because sequential body-burden data were not available. Assigning k =2.0 x 107?d7'. the value determined for “Co. leads to an “Fe committed effective dose equivalent of 23x 107°Sv (23x 107'remi for Rongelap adults. This is larger by a factor of 5 than the estimate for committed effective dose equivalent based on k = 0. Use of the body-burden extrapolation equa- tion leads to the conclusion that * Zn could have been the major contmbutor to the ingested activity during thefirst year post-rehabitation of Utink Atoll (see Table 4). This was supported to 9.6x 107 'nCkg7' ho! photon count rate at the surface of various types of tuna retrieved from the Marshall Islands’ fishing grounds from March to August 1954 (100-10,000 cpm). Fish with count rates greater enberger and Greenhouse (Gr77b) and was Atoll valeral The 50-yr external effective dose equivalent was to nearly natural background levels by the year ind. contributed a negligible amount to the total committed effective dose equivalent (see Table ground exposure rate was measured by Milt- h =~] the rom 8). subwas and dens at Rongelap Atoll were the best qualitv data for determining derived quantiues. Based on a declining continuous intake due solely to radioactive decay and the 1970 “Fe esumate of the daily activity ingestion rate for “Fe on the dav of return was calculated. Based ty Alp ato utd é SUR AL F i atec itted « even TORE rbed FXENIGLIGE vf an hese OAT ONE ME TRAE ABONE a chides amu‘lude 1cer. fa- tron with the declining continuous intake equa- the committed effective dose equivalent and the rate of deciine of radionuclides in the overall i ividSr, ternal Jeveis of radionuclides used in conjuncuions provuiec an esumate of the total intake, er I id P corr. 523 E. T. LESSARD erul. (3.7 x 107° Rh7!). estimated to be 1.7 x 107? Sv (1.7 rem) at Rongelap and 4.1 x 10~?Sv (4.1 rem) at Utirik. The external exposure rate is expected to decline to 2072. Theratio of internal committed effective dose equivalent to 50 yr of net externa! dose equivalent was 1.1 for Utink and 1.5 for Rongelap. The internal portion of these dose equivalent ratios does not include the contribution from Pu due to the uncertainty in Pu bioassay data. 201 2b 14 some extent by a Japanese report (JCCRRER56) which indicated a rise in the than 100cpm at the surface were discarded. Radiochemical techniques indicated the prominence of Zn in the tuna’s edible flesh. If it was assumed (1) that ©°Zn was the principal con- tributor to the externa] photon count rate, (2) that a self-sufficient living pattern existed on Utirik in which adults consumed 300 g of fish each day (Na80), and (3) that 1% of the fish eaten was tuna, then the daily activity ingestion