The TLD data for Bikini Island (Table 1) agree with. the RSS-111
measurements, but no constant relationship is seen between beta dose and gamma
exposure. Non-uniform deposition of fallout material in the areas surveyed and

transiocation of material are major factors governing this result.
DISCUSSION OF RESULTS

The average exposure rate as measured for each island is listed in Table
6. Estimation of the dose equivalent for the inhabitants of Bikini Atoll is
debatable due to the nonuniform distribution of radioactive material within
given areas of the atoll. The exposure rates measured on Eneu Island are fairly
uniform, but those on Bikini Island showed significant differences between areas
(Table 5 along with Figure 44 - 4E).
In the UCRL work4, this problem was
approached and a solution derived by estimating the fractions of an individual's
time =pent in various areas. These estimates+ are used here (Table 7) to
construct external exposure rate estimates for the various activities based on
the measurements reported in Tables 2 through 5. The exposure rate for the
lagoon was obtained by assuming that it would be less than or equal to that in
the areas of continual habitation. The values for other islands were obtained
by assuming that the Marshallese would spend an equal amount of time on each of
the other islands surveyed. All other estimates were made by taking the average
of al. measurements made within the area of interest.
Table 8 shows the estimated exposure rate for each pattern of activity in
Table 7 based on continuous occupancy of Bikini Atoll. Table 9 shows the estimated exposure rate for each age group as weighted by the percent of time spent
in each area,

for inhabitants of Bikini Atoll.

Summation of the exposure rates

in all the areas provides the average total-body exposure rate for each age
group.

Using the average hourly exposure rate, the long term external dose equivalent was calculated (Table 10). The data were corrected for background
(terrestrial and cosmic radiation) by using the average exposure rate on Wotje
and Ailuk as representative samples of the normal Marshall Island environment”.
These data for Bikini residents are lower than UCRL data? for living patterns 2
and 3, which give the estimated integral external gamma dose equivalent for 30
years

as 4 rem,

because

the

present

estimates

include

the measured exposure rate

for habitation of the newly constructed housing. These indoor values are 39%
lower than those previously reported and their use reduces the total estimated
reduction in the 30 year dose equivalent commitment by 32%.

The ICRP suggests® that population groups should not receive a 30-year
dose equivalent of more than 5.0 rem to the whole body from sources other than

medical equipment or natural background.

For the external radiation component

at Bikini Atoll, this requirement is met; the problem is that external radiation
is not the sole source of radiation exposure to the Marshallese. The dietary
pathway, based on UCRL data?, could increase the 30-year total body dose equivalent commitment by a factor of 4.
Whole-body counting data taken in 19741, 19772 and 1978’ indicate that the
dietary pathway became the prime source of radiation exposure after January

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