vals for a 6-week period. Radioanalysis of the excreta was performed in the same manner as
that of the tissue samples described above.
3.2
RESULTS AND DISCUSSION
3.2.1
Gross Observations
The animals had been roaming free on the islands. Although malnourished, they showed no
evidence of disease. Autopsy of two chickens that died during shipment revealed no pathological
findings that could be associated with radiation.
On the basis of an assumed 1-hr effective fallout time, the Rongelap animals received an
integrated external dose of 280 to 360 r, depending on the date of their collection (see Table
3,1). The Utirik pigs had received a calculated dose of 32 r at the time of their evacuation. The
animals all showed extensive external contamination, ranging from 0.5 to 5 mr/hrat 30 days
postdetonation. This activity was reduced about 75 per cent by a washing with water alone.
3.2.2
Radioactivity of Tissues and Excreta
The gross beta activity of the pig at 82 days postdetonation was about 4 pc. The distribution
of activity in the individual tissues is shown in Table 3.2. Over 90 per cent of the beta activity
was localized in the skeleton. The highest activity in a soft tissue was found in the liver, which
had, however, less than 0.5 per cent of the total body burden. The colon contents had the second highest activity for the soft tissues, about 0.24 per cent of the total. The alveolar tissue of
the lung had an activity less than 0.02 per cent of the total activity in the body.
Gross beta and gammaactivity of the chickens at 74 days postdetonation was approximately
0.2 pc. The gross activity per body weight of the chicken is approximately the sameas that of
the pig. The distribution of activity in the tissues of the chicken (Table 3.3) was very similar
to that in the pig. Most respiratory activity was localized in the turbinates, as a result of entrapmentof the large particles that could not penetrate to the alveolar tissue.
The beta activity in the skeleton of chickens at 160 days dropped to 4 per cent of the value
at 24 days postdetonation, whereas in the same period the gammaactivity dropped to 0.2 per
cent of the 24-day value. These data indicate that most of the activity is associated with shortlived isotopes. The initial drop in activity is very rapid, and after 45 days the decay curveis
essentially that of sr®? the most abundantof the longer lived elements deposited.
The residual total beta activity found in the two larger fish at 4 months postdetonation
averaged 2,5 tc (Table 3.4). There was, at the same time, about twice as much gammaactivity.
The fish were collected 56 days postdetonation, and the drop in activity between that time and
the analysis at 4 months represents only radiological decay. Thus the results are not directly
comparable to those obtained from animals that were returned alive and in which biological
turnover, as well as radiological decay, was operating.
The largest fraction of the gross beta activity in the fish was contributed by the concentration of radioactive material in the viscera. In two of the fish in which bones and muscle were
separated and analyzed, equal amounts of activity were found in each fraction. However, the
storage of these fish in formaldehyde for 3 months may have permitted the diffusion of the
radioelements from bone to muscle to take place. Further studies on fresh fish will clarify this
point.
The contamination of the fish was considerably greater than that of the land animals studied.
Since fish form a large staple item in the diet of the island populations, the high level of contamination is very important to consider.
At the end of a 2'4-month experimental period, the excretion by the chickens of beta and
gammaactivity per 24 hr was 5 per cent of the value measured at the start at 37 days postdetonation (Fig. 3.1).
Analysis of pig excreta indicates a similar decrease of activity with time. In a 6-week
period the gammaactivity excreted per 24 hr decreased to about 2.5 per cent of the activity
excreted at 44 days postdetonation (Fig. 3.1).
24