from all exposure pathways excluding cosmic radiation that range
from about 4 to 47%of the U.S. population-weighted background dose;
from about 2 to 29%of the Denver, Colorado dose; and from about |
to 17% of the Leadville, Colorado dose. When the 22 mrem/y of cosmic
radiation background dose in the Marshall Islands is added, the total
doses at the atolls for all exposure pathways range from 45 to 100% of
the U.S. population weighted external background dose; from about
23 to 50% of the Denver, Colorado external background dose; and
from 13 to 29% of the Leadville, Colorado external background dose,
depending on which diet is employed. The natural internal dose will
be similar in the U.S. and the Marshall Islands.
For additional reference, these estimated doses for the variousatolls
can be compared to the U.S. Federal guideline of 500 mrem/y above
backgroundfor an individual (170 mrem/y for the population average)
[52]. The doses at mostatolls are from 1 to 5% of the guideline,
depending on which diet is assumed to apply. The highest estimated
dose equivalent for an inhabited atoll is for the southern islands at
Rongelap where the doses range from about 10 to 50% of the guideline,
depending on thediet.
The 30- and 50-y integral dose equivalents provide a similar picture.
The 30-y integral dose equivalents for Likiep, Wotho, Ujelang, Mejit,
Ailuk, Taka, Jemo, and Bikar for the MLSC diet are less than 0.14
rem and for the BNL diet they are less than 0.7 rem. Thisis less by a
factor of 20 to 33 than U.S. Federal guidelines of 5 rem/30 y for a
population [52] and less than the integrated 30-y external background
dose in the U.S., which ranges from 1.6 to 5.5 rem [51]. The 30-y
integral dose equivalents for the MLSCdiet are less than 0.25 rem for
Utirik, less than 0.49 rem for Ailinginae, less than 1.3 rem for the
southern islands of Rongelap and for Rongerik, less than 7.4 rem for
Naen Island on northern Rongelap,and less than 3.3 rem for the other
northern islands of Rongelapif they were to be continuously inhabited.
Similarly, for the BNL diet, the doses are less than 0.72 rem for Utirik,
less than 2.1 rem for Ailinginae, less than 2.5 rem for the southern
islands of Rongelap, less than 14 rem for Naen Island at Rongelap,
and less than 7.6 rem for the other northern islands at Rongelap for
continuous occupation.
The global deposition of '’Cs in the 10 to 15° N. latitude of the
Pacific region through 1974 was about 30 mCi/km’ [53]. Adjusting
fo aadaasada betel
mined here, we see that 30% of the '’Cs soil concentration (and
therefore the dose) listed for Likiep, Wotho, Ailuk, Mejit, Ujelang,
Bikar, Jemo, and Taka is from worldwide fallout and is not specific to
the Marshall Islands. The worldwide fallout of '’’Cs accounts for about
74
7¢ of the '"Cs at Utirik and about 2% at Rongertk and Rongelap
Islands. The other 70, 93, and 98% of the ''Cs concentrations,
respectively, are due to intermediate range fallout.
Theglobal deposition of '''Cs between 30 and 50° N., which includes
the U.S., is greater by more than a factor of 3 than that in the 10 to
15° N. latitude. Thus, the deposition of '"Cs from global fallout
between 30 to 50° N. is nearly equal to the total '’'Cs observed at
Likiep, Wotho, Ailuk, Mejit, Ujelang, Bikar, Jemo, and Taka. The
deposition of other radionuclides follows a similar pattern.
Another comparison for this latitude and this area of the Pacific is
the background concentrations of ''’Cs in the soils at Ponape, Truk,
Palau, and Guam. The '"‘Cs soil concentration averaged over 10 cm
range from 0.1 to 0.5 pCi/g [54]. The range of '''Cs concentrations in
the 0- to 10-cm soil averaged for Likiep, Wotho, Ailuk, Ujelang, Mejit,
and Jemois 0.2 to 0.7 pCi/g, very similar to the backgroundlevels at
the other areas of Micronesia, although slightly higher.
The estimated doses for the southern islands at Enewetak Atoll are
very low and resettlement has occurred on these islands. However,
half of the Enewetak population, who lived on Enjebi prior to their
relocation and who ownthe landin the northern half of the atoll, wish
to return and establish permanentresidence. The estimated dose
equivalent for Enjebi Island, calculated using the average valuefor all
the parameter in the dose models, is less than 300 mrem/y for the
annual dose-equivalent rate and about 6 rem for the 30-y integral dose
equivalent (Tables 9 and 10). The U.S. Government has elected to
multiply by a factor of 3 these estimated annual doses and compare
the resulting number with the Federal guideline of 500 mrem/y. Thus,
the maximum, annual dose-equivalent rate presented to the Enewetak
people and used for risk analysis for Enjebi Island is 900 mrem/y when
imported foods are available. After evaluating the maximum doses and
the associated risk, the Enjebi people requested to proceed with
resettlement plans and that the U.S. provide housing, public buildings,
and an agricultural plan, The U.S. Government has not agreed to the
resettlement of Enjebi and the Enjebi people are continuing their
efforts to resettle the island.
At Bikini Atoll, the people were again removed from Bikini Island
in 1978 and the atoll is currently uninhabited. The people were
relocated when doses based on the 1975 Survey {5] were estimated to
body burdens were confirmed by the BNL whole-body counting program aslocal foods becameavailable. The current assessment of Bikini
Atoll (Tables 11 and 12) again indicate the magnitude of the doses
currently estimated for Bikini Island. However, at neighboring Eneu
75