3. Forbes, C. B., Nutrition in relation to
prob-lems of radioactivity. Pediat. Clin. N. Amer.,
9:1009, 1962.
4. Filer, L. J., Jr., and Martinez, C. A.: Intake
of selected nutrients by infants in the
United States, Clin. Pediat., 3:633, 1964.
5. Morgan, A. F.: Nutritional Status U.S.A.
Cali-fornia Agriculture Exp. Station Bulletin 769,
1969.
6. Butz, W. T.: How Americans use their dairy
foods. National Dairy Council, Chicago
1966.
7. Hesp, R.: Uptake of cesium-137, due to
nu-clear weapon fall-out, in subjects from West
Cumberland. Nature, 206:1213, 1965.
8. Filer, L. J., Jr., and Sarett, H.: Unpublished data.
9. Forbes, C. B.: Unpublished data.
10. Lough, S. A., Hamada, C. H., and Conar,
C. L.: Secretion of dietary strontium-90
and calcium in human milk. Proc. Soc. Exp.
Biol. Med., 104:194, 1960.
11. Straub, C. P., and Murthy, C. K.: A
com-parison of Sr90 component of human and
cow’s milk. PEDIATRICS, 36:732, 1965.
12. Rosenthal, H. L., Cilster, J. E., and Bird,
J. T.: Strontium90 content of deciduous
hu-man incisors. Science, 140:176, 1963.
1:3. Saxena, K. M., Chapman, E. M., and Pryles,
C. V.: The minimal dosage of iodide
re-quired to suppress uptake of iodme-131 by
normal thyroid. Science, 138:430, 1962.
14. Cuddihy, R. C.: Thyroidal iodine-131 uptake,
turnover, and blocking in adults and
adoles-cents. Health Phys., 12:1021, 1966.
15. KuIp, J. L., Schulert, A. R., and Hodges,
E. J.: Strontium-90 in man IV. Science,
132:448, 1960.
16. Comar, C. L., and Wasserman, R. H.:
Stron-tium and barium. In Coniar, C., and
Bron-ner, F., ed.; Mineral Metabolism: An
Ad-vanced Treatise, Vol. II. New York:
Aca-demic Press, pp. 523-572, 1962.
17. Pendleton, R. C., Mays, C. W., Lloyd, R. D.,
and Church, B. W.: A trophic level effect
on Cs”7 concentration. Health Physics, 11:
1503, 1965.
18. Onstead, C. 0., Oberhausen, E., and Kearv,
F.: Cesium-137 in man. Science, 137:508,
1962.
19. Holmes, 0. W.: Tile contagiousness of
puer-Peral fever. In Medical Essays. Boston:
Houghton Muffin, 1861.
20. Snow, C. P.: Science and Government.
Cam-bridge, Massachusetts: Harvard University
Press, 1961.
21. Senator E. L. Bartlett: Tile Congressional Record, August 3, 1965.
2.2. Federal Register, May 22. 1965.
DISCUSSION
DR. Lis: Opening the discussion on Dr.
Forbes’s paper is Dr. Bernd Kahn.
Dn. KAHN: Dr. Forbes mentioned that it
would be of interest to discuss specific
problems encountered in measuring
ra-dioactivity levels in food and relating them
to human exposure. The four major
prob-lems that occur to me are obtaining reliable analyses of food samples, representative
samples, accurate consumption values, and
a relation between intake and retention.
Examples of these problems are provided
by our studies to determine tile retention of certain radionuclides by infants.
The analytical problem lies ill measuring
radionuclides in extremely small concentra-tions. Sr’#{176}levels in infant foods, for
exam-ple, ranged from 0.1 to 10 pCi/gm ash
dur-ing the past 5 years. At the lowest
concen-tration, the acceptable reproducibility of
duplicate samples was plus or minus 8%.
The counting error was 5% for
radiochemi-cally separated strontium’#{176} from 10 gm ash, counted overnight in an anti-coincidence
beta counter. Other significant sources of
error contributing to the plus or minus 8
value include background irregularities in
overnight counting and corrections for
chemical recovery.
The success and failure of sampling are
both illustrated in Table I. The national
av-erages of the Pasteurized Milk Network are
remarkably representative of the Sr90/Ca
ratios in homogenized, skimmed, and
evap-orated milk consumed by the infants in our
study. Values for premodified milk and
soy-bean-milk formulae, however, lie outside
these ranges during some of the periods.
Should such formulae be sampled? The
ex-tensiveness of sampling is obviously deter-mined by balancing the need for inclusive-ness against the costs and difficulties.
The composition of a representative diet
con-I I I I I I I I
NDOT00D
1,000
-800
-
600-400
-200
-MILK ONLY
OTHER FOOD
I I I I I
0 30 60 90 20 150 180 210 240 270 300 330 360
AGE , days
FIG. 19. Average dietary intake of infants.
212 RADIOACTIVITY IN THE ENVIRONMENT
TABLE I
SR90/CA RATIOS IN MILK AND INFANTS’ FOODS, I’CI/GM
Year
Pasturized
Milk, National Averages
Infants Foods, Retention Study
Ilonwgenized
.
and Ski mmcd
.
Milk
,
Lvaporated
.
Milk
.
.iflk
1orniulae
Soybean
.
Milk orm ida
Average in
7
\ on-mvlk Foods
1960
1961
196
1963
5-9 6-9
5-8 6-It)
7-15
-13-8
-6-9 H
6 9-13
5-11 7-9
- 6
-3-4
(July)
19 (Sept.)
19 (Apr.) 24 (July)
-38 (May)
* Range of monthly averages, DRH-PHS Pasteurized Milk Network, from Radiological Health Data.
sumption from the concentration per
indi-vidual food. These diets can be based on
pediatricians’ experience, interviews, and
questionnaires for large groups’ or direct
measurements of small groups. An example
of the latter is our data for 30 infants
fol-0
0
E
0’
z 0 a.
lowed in their homes over 7 consecutive
months (Fig 19). Foods were selected by
the parent on the pediatrician’s advice and
supplied by us. The milk consumption is
approximately 300 mi/day below the value
a
U
0
C
0 C
(I)
Ui
ID U
80
AGE, days a
O’E
0
I
->-<
0I-00
ma.
FIG. 20. Whole body count of infant (30 minute count, 8
x
4 inch NAI (TL) crystal).AEC, as based on several references and
pediatricians’ advice.2
Figure 20 shows how to avoid all four
problems if the radionuclide of interest
emits gamma rays. The Cs137 and K4#{176}
con-tent of a healthy infant between ages 40
and 155 days are d#{128}termined by direct
measurement in a whole body counter. The
counting system is expensive, calibration is
difficult, and the standard deviation at
these low concentrations is appreciable, as
indicated. Nevertheless, direct
measure-ment is advantageous because the previous-ly cited uncertainties and, most
important-ly, the complicated problem of relating
in-take to retention for these radionuclides, need not be considered.
DR. MENEELY: I would like to hear more
comment on burden. One can never
mea-sure the total burdens of an individual. One
can measure the cesium burden, the iodine
burden of his thyroid, or something of the
sort, but this burden, even when specific as in the thyroid, did not result from a single nucide exposure. It arises from a particular physical make-up of the mix. Another factor
to consider is the metabolic pathway and
the time relations involved during passage
or the period of time in residence in a
depot. This is a very complicated deriva-tion; to those basic data, many more bits of
information must be added to obtain the
biological effect on tile individual. One
must select a matrix within which to
de-scribe a particular population. This must
include a factor for other hazards, a
fac-tor for sex difference, a factor for age
difference, and a factor for race difference.
Each is very important. Then, even within
this little compartment you have a variation factor of something like six in the
popula-tion right within that compartment. This
precludes using an average burden to
214 RADIOACTIVITY IN THE ENVIRONMENT
3. Pendleton, R. L., et a!.: Health Physics, 11:
1503, 1965.
DR. MAYS: As Dr. Forbes has indicated,
the body discriminates against Sr90. For
example, a constant diet containing 100 pCi Sr#{176}#{176}/gmCa will contaminate newly formed
bone in the adult human to about 25 pCi
Sr90/gm Ca, or about one fourth of the
dietary level. Thus, a protective effect exists in the metabolism of Sr90.
Unfortunately, this type of protection is
absent for Cs’37. In the adult human, the
ratio of cesium to potassium is about three times higher than that in food.3 Therefore, a constant diet containing 100 pCi Cs’37/gm K will contaminate adults#{176} to about 300 pc
Ca’37/gm K. The enhanced concentration
of Cs’37 by the body is of particular
signffi-cance to certain populations, such as the
inland Eskimos, whose food contains high
and persistent levels of Cs’37.
DR. RIvImA: One of the things we find
difficult in our work is to determine the
ac-tual intake of children as the function of
their age. Dr. Forbes data for calcium
in-take starting at age 7 years is one I have
never seen before. I wonder if the data can
be extended down to the younger age
group and in the opposite direction to
adults. How were these numbers for
calci-um intake arrived at? How generally
appli-cable are they? Another kind of information I have sought to find in the literature is this type of diet survey data which exists only in scatter form. It is very difficult to use
be-cause some construct a table of data
head-ed calcium intake as a function of age but
fail to give specific sources of calcium as a function of age, which is the information
pertinent to the problem. I hope members
* If there were cannibals who fed exclusively on
these people, the cannibals would acquire about
900 pCi Cs”/gm K. Cannibalism has certain
un-desirable features!
of the Academy will do this so that these
will be records of what people eat, not
what they should eat, not what Dr. Spock
recommends, but what is actually eaten in
various places in the United States by per-sons in different economic circumstances.
DR. FORBES: This is a very difficult
ques-tion to answer. The data I showed on
chil-dren and adults came from Agnes Fay
Mor-gan’s compilation of diet based on
sam-plings of some 5,000 individuals throughout the United States. I did not have access to a similar large body of data for the younger
child. This problem comes up all the time
in evaluating the dietary intake of patients.
The solution depends somewhat on the
atti-tude of the pediatrician’s questions of the
parents and the child. It also depends on
the attitude of the mother and her ideas to
what you had recommended for her child.
Tile process of denial so common in obese
patients also complicates the picture. All of these factors tend to reduce the accuracy of dietary surveys; yet, they continue to serve
as an important source of information. It
has been shown with interview analyses of
dietary intakes of obese children that a
trained dietitian can add up to 500 calories
to the dietary intake over that which has
been determined by an untrained medical
student. It has also been shown that many
more calories may be added to this intake if
enough time is taken to establish a close
rapport with the patient to allay his initial suspicions.
REFERENCES
1. Filer, L. J., and Martinez, C. A.: Clin. Ped., 3:633, 1964.
