year period.
The standerd deviation was in general 302 of the mean value for all age
and sex subgroup distributions.
the fact that
65
This less pronounced variation may be due to
“Zn measurements took place over a 3 year interval while
90,
and 137¢, occurred over a 23 year interval und thus was contained in a more
homogeneous population than were the longer lived nuclides.
Figures 22 and 23a and 23b summarize the
90
“Sr dose equivalent results for
individuals at Rongelap.
In this analysis, only the ingestion pathway was considered important.
Some radioactivity would enter the body via the resuspension and direct inhala-
tion pathways.
It is known that for a given soil concentration of the stable
naturally occurring analogs to the radionuclides considered here, the ratios
of food and fluid intake to blood relative to airborne intake to blood, are
as follows:
Co > 3000
Zn > 130
Fe > 550
Sr > 10,000
Cs > 400
Thus, dietary intake of radioactive material is the principal pathway leading to
internal deposition.
This applies to most nuclides in the environment, however,
there are notable exceptions including I, U, and Pu.
External Exposure
A value of .73 rads in tissue of interest per rontgen, measured in air at
one meter above the surface, was used to convert exposure in air to absorbed dose
in tissue.
The source was assumed to be an exponential distribution of 1376. ac-
tivity with depth in soil, typical of aged fallout (Be70).
Because of the
multidirectional nature of the source, variation of absorbed dose with depth of
organ was minimal.
Additionally, external doses were adjusted for living pat43