-S.Only the infant dose 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
_
TOTAL NUMPER OF UTAH INFANTS EXPOSED TO FALLOUT T°?
YEAR
BIRTHS
OF
DURING
BIRTH
1962
1961
1960
1959
1958
1957
1956
1955
1954
1953
1952
1951
1950
1949
TOTAL =
_ _ _ _AV._ THYROID DOSE (RADS)_ |
Age
YEAR
0.5 to 1.5
26,000
25,000
0.6 - 0.8
24,000
23,000
22,000
22,000
21,000
21,000
20,000
20,000
19,000
0.2
1.3
243,000
0.2 - 20
- 12
- 13
O.04u- 4
Age
TOTAL
0.6 - 0.8
0.6 0.6 -
1.5 to 2.5
0.2
1.3
|
0.2 - 20
2
~ 12
3-18
O.04- 4
AVERAGE DOSE =
DOSE
0.2
1.5
1.3
O.20.2 2
5 3
=
0.04-
20
20
12
30
22
4
:
1.3 - 10
Table 2 indicates that about 1/4 million Utah infants were exposed to
fallout I°3!, with an indicated average thyroid dose of 1.3 - 10 rads**
%
The enlargement of the thyroid gland with age reduces its I'3! concentration
and the resulting radiation dose from a given intake of P3?.
For example,
the intake of 1 microcurie (1,000,000 pCi) 23+ gives a 17-rad dose to the
e-gram thyroid of a l-year old infant; a 6.8-rad dose to the 8-gram thyroid
of an 8-year old child; and a 1.7-rad dose to the 20-gram thyroid of an
adult.
Furthermore, the weight of evidence indicates that the radiation
resistance of the thyroid increases with age ( » although the exact sequence
aot changes in sensitivity has not yet been established precisely.
“uy earlier crude methods yielded an estimated thyroid dose averaging 4.4 rads
to this population ©) ,
ment.
I am pleased (and a little surprised) at the agree-