RADIATION STANDARDS, INCLUDING FALLOUT
85
It should also be noted that value of the Sr® content or the Sr*/
Ca ratio of any individual dietary constituent cannot by themselves
be used to assess the degree of exposure: for such an evaluation it is
necessary to know the total amounts of Sr® and calcium in the diet.
The ratios of Sr/Ca in the body, the fetus and mother’s milk reflect the usual biological discrimination against strontium in favor
of calcium. This behavior is usually expressed in terms of the observed ratio; for example,
OR
= (0.25.
body/diet,
The variability in differential behavior, the processes involved and
the application of these concepts have been studied most intensively
in the laboratory, documentedinthe literature, and generally accepted.
I had not intended to go into this phase in any more detail unless
there is some question onit.
Chairman Ho.irretp. You, in effect, say here that this shows that
although there is that reading of 0.22 in the milk, that does not necessarily mean that the body absorbsthat.
It discriminates against some of that in favor of the collection of
calcium and, therefore, there is a lesser absorption that the figures
shownthere,is that right ?
Dr. Comar. Yes. It is perhapseasier to consider it in terms of the
ratios.
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If the total diet had a ratio of 1, then in the body the stron-
tium to calcrum would be 0.25.
If a person were consuming milk alone, his total diet would be 0.22
and the ratio in his body would be about a fourth of that, or 0.05.
Mr. Ramey. Has there been any changesince 1959 in your views as
to what this ratio is based, on further evidence ?
Chairman Ho.trietp. The discrimination factor.
Mr. Ramey. Yes.
Dr. Comar. The value for adult man seems to be gaining more support; that is, the value of 0.25 seems to be supported by the newer
evidence that is coming in,
As Dr. Dunham mentioned yesterday, for younger children the
value may be up as high as 0.5. For infants it might even approach
1 for a short time. Butthese experiments are not yet. in, in enough
detail to makea firm statement.
Mr. Ramey. Howabout the factor of pickup from thesoil of strontium. In our prediction panels, I believe, in 1959, the estimate apparently was assumed that you wouldget it all from thesoil.
Dr. Comar. I am going to discuss that later on if I may defer the
question ?
Mr. Ramey. Very well.
Chairman Hovirteip. Will you proceed, please, Doctor?
Dr. Comar. The discussion so far has been concerned with the
steady-state behavior and it is of interest to consider the actual state
of affairs in the last 2 years.
Chart 4 presents values for Sr*°/Ca expressed as in previous diagrams. The differences between plant foods and milk are not as great.
as will be attained under steady-state conditions for reasons that will
be discussed presently.
Nevertheless, plant foods have a higher Sr®/Ca ratio than the typical diet, and milk has a lowervalue.
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