DIETARY INTAKE OF RADIONUCLIDES
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TOTAL-DIET 9°Sr-INTAKE VARIATIONS
The methods used to estimate the level of Sr in the diet can be
classified under several categories:
1. Analysis of the total diet as consumed.
2. Analysis of a diet composite made up of individual foods that
were selected and weighted by average per capita consumption data.
3. Analysis of individual foods weighted by consumption data and
summarized for total-diet estimates.
4, Ratio analysis, which is the practice of relating another nuclide,
preferably a gamma emitter, or the *Sr content of biological substances
such as urine, feces, etc., to the dietary “Sr level ("Cs/"Sr, urine/
diet, etc.).
The first two categories represent the most common methodsin
use and must contain accurate estimates of (1) radionuclide concentra-
tions, (2) food consumption, and (3) diet composition to provide good
estimates of intake levels. Seldom are these requirements metin full.
Most of the emphasis has been directed toward the refinement and
standardization of radiochemical procedures and the improvement of
counting facilities. This effort has produced results that can generally
be considered as dependable and representative for most fallout situa-
tions. However, no Similar effort has been directed toward the development of food-consumption data.
For estimation of radionuclide
intake, it is necessary to blend the data from radionuclide networks
with food-consumption statistics. If the food data are inaccurate, outdated, or inadequate in coverage, then the estimate of radionuclide
intake is of questionable value.
Many of the food data in use are based on survey results! of 6000
households taken by the U. S. Department of Agriculture in 1955. This
survey utilized a “recall-list” technique where respondents were asked
about the foods consumed during the previous sevendays. The sampling
was conducted during the months of April, May, and June. The dif-
ficulty of extrapolating a week’s recall data of this type to reflect a
year’s consumption is immediately obvious, but this is the standard
practice utilized in nearly all estimates of annual radionuclide intake.
Other problems such as the season of the year in which the survey was
taken would result in variations of equal or greater magnitude. As an
example of the complexities associated with expanding a week’s results to a year, a comparison of similar recall-list techniques used
during the Pilot Food Stamp Plan’ in 1961 can be given (see Table 1).
This survey is particularly appropriate because it shows consumption
‘during a similar period of the year (April and May) in contrast witha
later period (September and October) when the effects of season and
the stamp program are evident. Two of the more seasonal vegetables,