Next I tabulate the total number of exposed Utah
infants, and compute the average dose for all of then
(Table 2).
The yearly births were derived from the
U.S. Census (1960 and 1950).
The average birth time was
taken as mid-year, followed by an average delay of about
six months before appreciable consumption of fresh cow's
milk.
Thus,
exposures were regarded as beginning at
the start of the calendar year immediately following
the year of birth.
Only the dose during infancy
has been computed.
However, dose calculations can
easily be extended throughout childhood using the method
shown in Table 2 and correcting for the increasing mass
of the thyroid with age.*
Table 2
INFANT EXPOSURES BY YEAR OF BIRTH
YEAR
BIRTH
OF
DURING
YEAR
0.5 tol.5
1962
1961
1960
26,000
25,000
0.6 - 0.8
BIRTH
Age”
AV. THYROID DOSE (RADS) _
Age” ~
1.5 to 2.5
TOTAL ~
_
DOSE
0.6 - 0.8
0.6 - 0.8
0.6 - 0.8
1959
1958
1957
24,000
1956
23,000
1955
22,000
1954
22,000
21,000
1953
1952
21,000
1951
20,000
1950
20,000
1949
19,000
TOTAL = 243,000
0.2
1.3
0.2 - 20
2
-12
3
-18
0.04 4
0.2
1.3
0.2 - 20
2
-12
3
-18
0.04 4
AVERAGE DOSE =
0.2
1.5
1.3
0.2 - 20
0.2 - 20
2 -12
5 = 30
3 - 22
0.04 4
1.3 - 10
* The enlargement of the thyroid gland with age reduces
its iodine 141 concentration and the resulting radiati on
dose from a given intake of iodine 131.
For example,
the intake of one microcurie (1,000,000 picocuries) of
iodine 131 gives a seventeen-rad dose to the two-gram
thyroid of a one-year old infant, a 6.8-rad dose to
the eight-rad thyroid of an eight-year old child, and a
i.7-rad dose to the 20-grar thyroid of an adult.
Furthermore, tne weight of evidence incidates that the
radiation resistance of the thyroid increases with age 3 ?
although tne exact sequence of changes in sensitivity
has not yet been established precisely.
DOE ARCHIVES
4x