health and safety laboratory - Digital Collections

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1* The gummed film results tend to be low when compared to pot
analyses.
2. Results from composite samples are even lower with respect to
the pot analyses than the summed daily values compared in
adjoining months.
3. The highest daily pot/film ratios are found in 1954, and the
next highest are found in 1958 and 1959.
4. The daily pot/film ratios are generally good during 1955, 1956
and 1957.
Since the composite gummed film results were excessively low, a com
parison was made for the months of February through June of 1955 where the
samples from stations in the United States were run by both methods. This
comparison showed the summed daily values to be 5 times as high as the com
posites on the average. This value may not be generally applicable and has
not been used in preparing the summary tables for individual stations. The
most probable causes are loss of sample in compositing and insufficient cor
rection for self-absorption.
The monthly pot samples collected in New York City from 1954 through
1958 were analyzed for total p activity as well as for Sr 90 . These total p
activity values have been treated by the present model, assuming the monthly
collection to have been a single sample taken on the 15th of the month. (Pot
samples before January 1957 were collected weekly and the effective date was
taken as mid-week). This computation allows comparison of calculated and
measured Sr from the same collector.
The data in Table 5 show a marked improvement over the comparison
made in Table 4. This is surprising, since they are based on the ssune
model and a factor (1.6) has been included to correct for gummed film ef
ficiency. The difference is very marked for 1958, and an inspection of the
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