-12There is some evidence ?) that thyroid irradiation from 731 is only
about 1/10 as effective as x-irradiation in producing thyroid cancer in
rats, but it is. unknown whether this relation also applies to the human
infant.
The predicted numbers of thyroid cancers in Utah children are
tabulated in Table 6 for both a relative biological effectiveness
of 1 and a R.B.E. of 0.1.
(R.B.E.)
These values are compared with the number of
"spontaneous" cases expected by age 15 years.
Children are arranged by
age recognizing that some children were irradiated at age 0-1 and again at
age 1-2.
rarily
Irradiation received at age 2 and older has been assumed arbit-
(although perhaps incorrectly) to be without effect.
Table 6
PREDICTED THYROID CANCERS IN UTAH CHILDREN
AGE
IN 1963
13
le
11*
10*
9
8
7
6
5
y
3
2
L
0
NUMBER OF
CHILDREN
20,000
20,000
21,000
21,000
22,000
22,000
23,000
24,000
24,000
25,000
25,000
26,000
27,000
. 27,000
*St. George
700
Irradiated 250,000
EST. AV. TH.
DOSE (RADS)
0.4
4.2
10.1
6.3
2.0
2.0
8.6
10.0
1.4
0
0
1.0
1.0
0
68
Qiu
PRED. TH. CANCERS
RBE = 1
RBE = 0.1
0.16
0.02
1.68
0.17
u.24
0.42
2.64
0.26
0.88
0.09
0.88
0.09
3.96
0.40
4.80
0.48
0.67
0.07
0
0
0
0
0.52
0.05
0.52
0.05
0
0
"SPON. "
0.44
0.44
0.47
0.47
0.49
0.49
0.51
0.53
0.53
0.55
0.55
0.58
0.60
0.60
0.95
0.10
0.02
21.90
2.20
5.57
The predicted total number of fallout-induced thyroid cancers is 22
(for an R.B.E. of 1) or 2 (for an R.B.E. of 0.1).
These would be in add-
ition to the 6 "spontaneous" cases expected to develop in this 1/4 million
children during their first 15 years.
The large number of irradiated
children provides a rare opportunity to test the hypothesis that small