Table 9.
Risks of thyroid nodularity from radiation in children.*
Risk
Group
Type
(years follow-up)
Rongelap (27)
Ailingnae (27)
Utirik (27)
rad
(rads)
Benign
18, Y
710-1150
26.7
"
"
All of above
Rochester (25)
Ann Arbor (17)
"
x-ray (162)
x-ray (162)
Dolphin (20)
UNSCEAR (17)
x-ray (182)
x-ray (97)
Beach &
ABCC (20)
Dose
Y,n (172)
280-450
60-95
312 (Cav)
119 (Cav)
20 (av)
1.6
29.4
0
24.4
1.9
3.0
2.2
16.7
3.8
24.0
L.7
0.5-1.5
20-1000
ABCC (20)
Modan et al.
Y,n (172)
x-ray (163)
<20
6-6.5
Maxon (21.5)
x-ray (164)
270 (av)
Albert et al.
Carcinoma.
1.3 (all ages)
0.2 (all ages)
4.2
12.3
1.5
No. of cases x 1076
*Risk is calculated . from the equation dose x years at risk’
Appendix IV.)
(See Table 4,
Unoperated cases in the Marshallese groups were not included
in the estimates. The incidence in the matched comparison Marshallese population has been subtracted from that in the exposed groups in determining the
risk.
If the actual number of years at risk were used,
i.e., subtraction of
latent period, the risk values would be higher in the Marshallese.
studies under way indicate that they may be too low.* Considerable variation
in individual thyroid doses probably resulted from differences in food and
water consumption at the time of the fallout. The greatest uncertainty was in
doses to the children.
Undoubtedly, the two boys exposed at one year of age
who developed thyroid atrophy and myxedema received doses well above those
calculated, as explained in Appendix II.
From the Marshallese experience it appears that there is a greater
propensity to develop thyroid nodularities after radioiodine exposure in the
children than in the adults.
This is related not only to the smaller size of
their glands (resulting in larger doses) but possibly also to the rapid growth
of the gland (from 1-2 grams at birth to about 18 at maturity) and increased
*Even if the Marshallese thyroid doses were twice as high, the risk estimates
would still be higher than would be accounted for on the basis of 13ly exposure alone.
-~ 78 -