To
measure
the concentration of strontium-90
in
test
samples of milk, CU’s consulting laboratory boiled the
water away and then burned off the organic matter in
an electric furnace (below). The resulting ash was then
dissolved, and the calcium and strontium precipitated and
filtered (right). By measuring radiation in the residue,
technicians
could
calculate
the
strontium-90
content
5.U. greater than it was in 1957, which is at least double
the AEC estimate for the annual rate of increase over the
last few years. This more rapid rate of increase must be
considered tentative, since data for all of 1958 are not yet
CU foundthat the strontium-90 in the milk supplies of sev-
eral cities was about twice the average of the others. These
seven cities were:
NEW ORLEANS, LA.
available. The summer months, when cows graze on the
BISMARCK, N. D.
BOSTON, MASS.
PITTSBURGH, PA.
open range, are more likely to yield milk with a higher
strontium-90 content than winter months, when cows are
fed on stored hay and fodder. Offsetting to some degree
such an anticipated drop in the strontium-90 content of
milk for the latter half of 1958 will be the effects of fallout
from the stepped-up rate of weapons testing during the
period August to November 1958. Because of this testing,
it may be assumed reasonably that the average strontium90 content of milk as currently consumed in the U.S. is
about 8 to 10 S.U., and will likely be closer to the higher
figure during the coming summer.
However, an average may befalsely reassuring. Local
meteorological conditions and other factors conceivably
could create conditions resulting in high concentrations in
relatively small areas that embrace large numbers of people. In CU’s tests, a range from about 2 S.U. to almost
16 S.U. was found in the composited samples. It has been
estimated that a factor of five applied to the average
found would encompass most of the variations that might
be expected for all factors. In such “hot” areas the concentration of strontium-90 in milk might be about 50 S.U.
—more than half the currently recommended maximum
“permissible” concentration.
In its tests of samples collected in July and August 1958,
110)
MARCH 1959
15.6 S.U.
14.1
13.9
13.7
MEMPHIS, TENN.
13.6
QUEBEC, CANADA
CHICAGO, ILL.
13.6
12.6
DULUTH, MINN.
RAPID CITY, S. D.
11.5 S.U.
11.2
Several other cities were well above-average, though not so much
as those above:
ST. LOUIS, MO.
11.1
NORFOLK, VA.
DES MOINES, IOWA
10.6
10.6
NEW YORK CITY
SEATTLE, WASH.
10.5
10.1
As was to be expected, most of these cities are in the
northern part of the country; several high-count areas were
found in the southern part of the U.S., too. Ten of the 13
U.S. cities just listed are not included in the present PHS
test network. It appears to CU that the PHS would do well
to extend its testing to include at least these 10. Furthermore, it appears to be desirable to investigate the milk supplies of all other areas which have not been included up to
nowin any study, in order to locate any other areas whose
milk is abnormally high in strontium-90. It is further suggested that the study of milk supplies might profitably include provision for more representative sampling than has
been the practice in the past.