Number of
Individuals
Age Group
<5
Volume of
Urine (m1)
% of Total
Volume
7
1,155
4.8
5 - 16
11
4,829
20.1
>16
34
18,011
75.0
The urine samples are typical of adults and the calculated thyroid burdens
are presumably also those of adults.
133
Associated with this y}3} are the shorter-lived isotopes ps2 I 3 :
and p39.
If the iodine entered by wayof inhalation, the time of intake was
H+6-+-0H+18,
On the other hand, if water (and food) were the principal
source, the time of ingestion would be extended from H+ 6toH +51.
Three items contribute to the differences in dose from the various
iodine isotopes.
These are:
(1) radioactive decay before inhalation or oral
ingestion, (2) differences in the fission yields of the chains,° and (3) the
average energy deposited in the thyroid per disintegr ition.
are presented in Table I for 1139 and p35.
distribution in the cloud was assumed.
These factors
In the case of inhalation, uniform
For oral ingestion it was assumed
that, on the average, one-third of the intake occurred at H + 10 and twothirds at H + 30.
Table I,
Ratio of doses for the two modes of intake.
Inhalation
Oral Ingestion
p33 77131
pi85 ;7131
Decay
0.68
0.31
0.487
0,148
Energy
2.00
1,50
2.00
1.50
1.85
0.57
1.35
0.27
Fission yield®
Net Factor
1.38
p93 ),131
1.23
1.38
p99 ;131
1,23
The dose to the thyroid in rads from all three isotopes is thus 3.4 times the
31
131
dose due to v
ingestion.
alone for inhalation and 2.6 times the I
dose for oral
Delay in reaching the thyroid after inhalation or ingestion would
lower these factors somewhat.
However, the y)32 daughter of the 78-hour
Tel 3? has been neglected and would approximately compensate for decay of
§
2
133 ana 1) before reaching the thyroid.
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We can now proceed to estimate the dose to the thyroids of 3- to 4-
year-old girls assuming (1).inhalation as the mode of intake and (2) oral
ingestion.
“4
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