teemee
Fig. 3.1—Arrangement of apparatus for measurement of thyreid 1'* uptake in humans,
the thyroid gland did not exceed background. Three instances of higher levels were subsequently demonstrated to indicate external contamination of the hide, rather than actual thyroid
radioactivity, when the glands were removed and assayed in a deep-well scintillation counter.
3.3.
DETERMINATIONS OF RADIOACTIVITY IN SAMPLES OF URINE
Animals recovered from both the 7- and 106-mile-arc stations were studied during the
first 3 days following head exposure to fall-out. The first urinary collection period was from
H+14 to 18 hr, the second was from H+18 to 33 hr, and the third was from H+33 to 53 hr.
Samples from the first collection period, from animals at the 7-mile arc, were counted twice:
first at H+55 hr and again at H+117 hr.
The values for beta-gammaactivity found are presented in Table 3.2. The initial radioactivity levels were so low that, when samples were recounted 3 days later, the values obsamples collected immediately after return of the animals to Mercury are corrected for decay and extrapolation is made to H+ 12 hr, it is seen that small amounts of soluble radioactive
materials were present. From the rapid decay rate estimated from recounting these early
samples (at 55 and 117 hr), it is possible that 1°" was involved; however, because of low initial
levels, this possibility could not be established with certainty.
~ All samples from animals exposed at the 106-mile stations were found to have no meas-
urable radioactivity when counted at H+55 hr and later. Thus it {s impossible to determine
what the actual levels would have been immediately after exposure. However, they were un-
doubtedly lower than those found in animals exposed at the 7-mile stations.
at Aen
tained were too low to permit accurate measurements. However, when the values obtained on