~ 8.
Table 4
PREDICTED THYROID CANCERS
IN THE 565 INFANTS NEAR ST. GEORGE
AVERAGE DOSE
(120 rad - 440 rad)
ASSUMPTION
1)
£35 Thyroid Cancers
10®°
IN 1953
Infants given 1 rad
(Effect of x-rays; Beach & Dolphin)
2) 1/10 of x-ray effect
(113+ /x-ray RBE in rats; Doniach)
2
-
9
0.2
-
0.9
3) High Threshold
0
0.01
Wage
"NATURAL" INCIDENCE BY 15 YEARS AGE
(from Mustacchi & Cutler)
DISCUSS ION
A number of conclusions follow:
1}
Under the assumption of linear dose-response relations, the predict-
ed number of induced cancers for the total state is 5-10 times higher than
for the high-fallout St. George area where the studies to date have been most
emphasized.
Therefore, consideration should be given to expanding the studies
into additional regions.
2)
The advantage of studying the limited population in the St. George
area is that the expected number of "natural" thyroid cancers is so low
(0.01) that the observation of a single case of thyroid cancer would be high-
ly suggestive of radiation damage, while the observation of 2 cases would constitute almost conclusive proof.
However, under assumption (B) less than 1
case is predicted.
3}
The "epidemic" number of thyroid cancers predicted from assumption
(A) have not been observed experimentally”.
This indicates that either (1)
low doses are less effective rad-for-rad than higher doses, or (2) E** doses
are less effective than x-ray doses.
Very likely, both of these effects are
in operation.
*
If the additional doses received in later childhood had been included, the
predicted number of cancers would have been even higher.