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Reprinted from Scrence, July 11, 1958, Vol. 128, No. 3315, pages 85-86.
KR
Current Strontium-90 Level in
Diet in United States
Table 1. Strontium-90 in common vege-
tables from various locations, 1956-57,
Sample
Knowledge of the concentration of
strontium-90 in the diet permits calculation of the equilibrium Ievel in the
humanskeleton (7), This report (2) de-
scribes measurements on approximately
100 food samples. Samples of the im-
portant calcium (and therefore strontium-90)}, sources—that is, milk, vegctables, cereals, and tap water—are in-
cluded.
.
Each vegetable sample (Table 1) represents 10 packages (about 3 kg) of
frozen food, which in turn represent a
production run at a food plant. The
cereals (Table 2) were 200-g aliquots
of a dozen boxes of the most common
varieties. Liquid milk samples (Table
3)
came mainly from cows that had
grazed on unplowed land, Meat, eggs,
and fish were omitted because their contribution to the calcium intake is trivial
and because the Sr®°/Ca ratio is not ex-
pected to exceed that in milk by more
than a factor of 2.
The chemical and radiometric procedures have been described elsewhere
(3). The over-all yield of strontium was
monitored with a Sr®> tracer. A representative set of six frozen vegetables was
prepared according to the directions on
the package, and the liquid phase was
analyzed separately. No appreciable Sr®°°
is removed in the preparation of the
vegetables for human consumption.
The data on U.S. milk (Table 3) include those of the Health and Safety
Laboratory of the AEC New York Operations Office (4), extrapolated to late
1957 where necessary. The variations in
Sr®° concentration from one farm to the
next are probably related to the available calcium content of the pasture and
to the average root depth of its grass.
Duplicate milk samples from two nearby
farms in Virginia gave 1.9 and 1.9, and
8.1 and 7.1 wc of Sr®° per gram of cal-
cium (hereafter referred to as strontium
units, SU), respectively. Variations up
to a factor of 2 occur from a single distribution source (Bergen County, N.J.)
over a period of a month, reflecting
changes in relative quantities of milk
from contributing farms in successive
batches. Despite these short-time variations, the average monthly value for dif-
Date
SU
Maine
Peas
8/56
21.3
Western New York State
Beans, cut green
8/56
20.2
Beans, cut green
9/56
18.4
Deans, cut green
9/56
8.6
Beans, wax
7/57
13.6
Beans, wax
8/57
11.3
Cauliflower
10/56
9.1
Corn
9/56
28.4
Spinach
6/57
18
Av.
13.9
Eastern Pennsyluania, New Jersey, Long Island
Asparagus
6/56
1.2
Asparagus
5/57
1.1
Reans, cut green
12/56
4.6
Beans, cut green
9/56
8.0
Beans, lima
9/56
6.6
Cauliflower
fall/56
8.1
Peas
6/57
10.0
Potatoes, sweet
P/57
13.3
Potatoes, white
?/57
6.1
Squash
fall /56
11.5
Ay.
7.3
Eastern Maryland, Delaware
Asparagus
10/56
1.7
Beans, lima
?/56
2.9
Beans, iima
9/56
8.4
Broccoli
10/56
4.7
Breecoli
10/56
6.7
Breccoli
10/56
8.5
Corn
12/56
3.6
Peas
12/56
1.3
Av.
4.7
Tennessee
Okra
Spinach
Spinach
Turnip greens
Turnip greens
Av.
Corn
Peas
Av.
.
7/57
?
4/57
5/57
2/56
Minnesota
9/56
6/56
Washington, Idaho, Oregon
Beans, lima
9/55
Broccoli
9/56
Corn
8/57
Peas
6/57
Peas
7/56
Peas
6/56
Potatoes
2/57
Squash
9/56
Squash
10/56
Av.
California
Asparagus
Beans, lima
5/57
Beans, lima
9/55
Beans, lima
9/56
Broccoli
4/57
Brussels sprouts
10/56
Brussels sprouts
9/56
Brussels sprouts
12/56
Brussels sprouts
11/56
Cauliflower
10/56
Cauliflower
4/57
Spinach
3/57
Spinach
3/57
Spinach
3/57
Av,
Av. for all vegetable samples
Av. for peas, beans, corn, and potatoes
18.6
6.1
1.2
21.3
7.8
10.9
1.6
5.8
3.7
6.3
3.7
2.1
4.8
7.8
3.0
8.7
3.1
3.7
4.8
1.8
4.6
10.0
4.3
4.5
12.0
4.3
2.5
1.1
28.5
22.5
13.9
9,1
9.5
8.5
9.4
8.7
ferent parts of the country is quite uni-
form, giving an average concentration
for the country of about 6 SU. In comparison, the average level of Sr? in
British milk would be 7 to 8 SUin late
1957, on the basis of an extrapolation of
the 1956 data (3).
The vegetables and cereals (Tables 1
and 2} are representative of large-acreage production. Variations from one
sample to another grown in the same
general area probably reflect different
soil conditions. No appreciable increase
in Sr®° from mid-1956 to early 1957 is
observable from the data, as is not wholly
unexpected, since an increase in Sr®° in
the total fallout was only about 20 per-
cent during this period.
Geographical differences in the Sr°¢
concentration appear but do not exceed
two times the mean. In the diet, however, these differences are averaged out
because of the nature of commercial
food distribution. Some differences appear among plant types—for example,
asparagus ts relatively low, but among
the major calcium contributors (peas,
beans, and cereals), the Sr® level is
rather uniform.
The U.S. population obtains 85 percent of its calcium from milk, 4 percent from cereals, and 5 percent from
vegetables (6, 7). If the average concentration of Sr®® in these foods in the
United States in late 1957 is assumed to
be 6, 15, and 10 SU, respectively, the
average diet contains about 6.5 SU. In
an extreme case, a vegetarian might
have double this value.
Monthly integrated tap-water samples
in the New York City area now carry
about 0.1 wc of Sr®° per liter. If an
average consumption of 1 liter of water
and 1 g of calcium from food each day
is assumed, the contribution of Sr®° from
Table 2. Strontium-90 in common cereals
from various locations, 1956-57.
Sample and location
Wheat (New York}
Wheat (Washington)
Bran (Michigan)
Flour (IHinois)
Rice (Unknown)
Wheat (Unknown)
Oatmeal (Unknown)
Av. for all cereals
Date
SU
2/56
55/56
summer/57
7/56
2/56
2/56
2/56
22.8
9.1
8.6
6.7
4.0
37.5
5.7
13.5