of urine activity concentration variability, there was a 60% probability that
the male value for K would be different from the female value by the factor
observed.
Thus differences in the derived activity ingestion rates and dose
equivalents were not significant.
.
.
65
Figure 14 shows a semi~log plot of the
rate histories for adults on Rongelap.
.
.
the appearance of an increasing
137
Zn and
137
woe
.
.
Cs activity ingestion
A curve was drawn between points, and
.
.
.
1.
eae
Cs ingestion rate during the 1960's indicated
the possibility of another contaminating event.
The Hardtack Phase I series was
conducted just prior to the observed increase in the curve and fallout from the
Cactus, Yellow Wood, and Hickory experiments detonated at Bikini and Enewetak
would have reached Rongelap.
However, several observations fail to support the
conclusion that recontamination was significant.
—~
increase
65
in
137
These are as follows:
1) the
Cs ingestion rate was not in conjunction with an increase of
Zn; however, since 6525 is an activation product it may have not been produced
in the same proportions.
2) The peak 1376, body burden at Utirik occurred
nearly three years after the initiating event, Castle BRAVO, while the peak body
burden at Rongelap followed six years after the potentially contaminating experiments of the Hardtack series in 1958.
3) The activity ingestion rate at Utirik
demonstrated a continuously declining pattern versus the humped pattern observed
at Rongelap.
This occurred even though there was an equal external exposure
rate history following the Hardtack series as measured by the U.S. Public Health
Service on both Rongelap and Utirik (Un59).
4) The peak exposure rate on
Rongelap following the Hardtack series was 10,000 times less than the peak exposure rate following BRAVO.
These facts suggest that the Hardtack series was not
a major factor influencing the Rongelap body burden patterns.
Thus it is
postulated that body burden variations were caused by travel away from the atoll
29