Since the study began, tissue samples have been collected from three cows, two
calves, and one fetus in October, 1973; three cows and two fetuses in July,
1974; one cow and two yearling calves in January, 1975; and two cows and two
calves in January, 1976. Other animals sampled from the study area included
three goats, three foxes, one jackrabbit, one coyote, and one yearling beef
animal that wandered into the area in December, 1975.
2-year-old bulls are still grazing the study area.
One aged cow and two
Since the Nevada Applied Ecology Group meeting in May, 1975, analytical data
have been received on all tissues collected through January, 1975. Much of
these data were summarized and presented at the International Atomic Energy
Agency/Energy Research and Development Administration symposium in November ,
1975 (Smith et al., 1976).
In January, 1976, an additional data printout was received from the analytical
laboratory which included data on the gonads and four other tissues from five
animals (three aged cows and two yearling bulls).
The vital statistics of
these animals are presented in Table 1.
All animals grazed the outer compound
of two compounds established in Area 13. The cows were sacrificed in July,
1974, approximately 14 months after their entry into the area. The bulls were
sacrificed in January, 1975, 15 and 19 months after their birth within the
outer compound.
RESULTS AND DISCUSSION
Table 1 also shows the data on the ash percentages of the tissues analyzed.
Data are frequently expressed in reports as activity per unit of ash, or as
per unit of dry weight, or as per unit of wet weight.
Frequently there are
wide variations in percent ash reported for similar tissues by the analytical
laboratory, e.g., the gonads of cow number 4 and the femur of cow number 6 in
Table 1. Also note the sixfold variation in other gonad data, fourfold in
muscle, threefold in lung, and fourfold in liver.
If the data are reported on
these samples as activity per gram of ash, wide variation may result.
Reporting
the data as activity per kilogram of wet weight tends to level out these
variations since water loss between sampling and analysis should not cause
such a large variation.
For example, if two muscle samples each weighing 2 kilograms (kg) and each
containing 100 picocuries (pCi) of activity, are analyzed and the ash percentages are reported as 3 and 9%, then the activity per gram (g) of ash would be
reported as 1.67 pCi/g ash and 0.55 pCi/g ash.
This is a 300% difference.
When these values are converted back to wet weight, the correct value of
50 pCi/kg is obtained. Also, dose estimates from ingestion of tissues require
that the activity be expressed on a wet weight basis.
Therefore, in the
following discussion, all data are reported on the wet weight basis.
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