These values do not include the contribution of radium-226 from tap
water.
However,
the radium-226 content of the water is low and would
not materially increase the daily intake estimate.
New York City
San Francisco
0.011 pCi/liter
0.015 pCi/liter
Comparison of the two surveys in Tables 1 and 2 shows that although
individual food types may vary by more than a factor of 2, the average
daily intake for each city varies by less than 20% or within expected
experimental error.
It should also be noted that both the 1966 and 1968
food samplings were collected at mid-year so that possible seasonal
variation was not studied.
[It seems unlikely that a significant seasonal
variation in dietary radium-226 would exist for a given location.
The California State Department of Health has estimated the daily
radium-226 intake of individuals receiving a hospital diet.
The average
daily radium-226 intake for Berkeley, California hospital diets from
November 1967 to June 1968 was 0.4 pCi/day. (4)
Similar diets collected
from April to December 1968 in San Francisco averaged 1.3 pCi/day.
(5,6,7)
The radium-226 content of human bone from New York City and
San Francisco is 0.036 pCi/g Ca and 0.031 pCi/g Ca, respectively,
Since
the dietary radium-226 levels for these cities are different by about
a factor of two, it would be expected that the bone levels would reflect
this difference.
We suggest that a particular dietary component or a
combination of a few components may control the radium-226 level in man.
Little is known about the availability of radium-226 from foodstuffs,
but there is indication that it is quite variable.
We are initiating a
few studies to attempt to correlate radium-226 bone levels with particular
dietary components.
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