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doses to the infant thyroid from ysl are equally as effective rad-for-rad
as are large doses of x-rays abruptly given.
On the other hand, if an RBE of 0.1 is closer to the truth, then it
will be difficult to separate the radiation-induced cancers from. the "spontaneous".
One cannot help but wonder what fraction of the so-called "spon-
taneous" cancers are in fact due to medical x-rays given before or after
birth.
If a sufficientiy high threshold exists for the induction of thyroid
cancer by irradiation, then there may be no cases caused by fallout.
The fact that many children were born when there was no testing within 2 years of birth provides an internal control by which the normal
incidence of thyroid cancer in Utah can be established.
Also, the uneven
distribution of fallout suggests that slightly contaminated areas could
serve as controls for those heavily contaminated.
Finally, the fact that
with other factors being equal, ysl dose is proportional to milk consump-
tion suggests that in theory the low milk drinkers could serve as controls
for the high milk drinkers.
However, from the practical standpoint, the
work and uncertainty in estimating individual milk consumptions in retrospect does not appear promising except for limited areas such as St. George
which received appreciable doses.
An interesting implication is the prediction that the number of cases
at St. George is small compared to that for the state as a whole.
It is
indeed fortunate that only a few hundred children received high exposures.
Crude as these dose estimates are, they indicate the advisability of
studies for possible delayed radiation effects in Utah.
To be fruitful
such studies should have long-term support and look for other effects in
addition to thyroid cancer.