Table 2
Estimation of Gamma Dose2
No.
in
Approx. time of
commencement
I. Rongelap
64
H+4to6hr
II. Ailingnae
III. Rongernik
18
28
H+4to6hr
H+6.8 hr
Group
designation
[V. Ctirik
group.
157
offallout
H+22? hr
Timeof
evacuation
H +50 hr (16 people)
H+51 hr (48 people)
H+58 hr
H+ 28.5 hr (8 men)
H +34 hr (20 men)
Started at H+ 35 hr
Completed at H + 78 hr
andthe fallout duration as ~12 hr, with most of
the dose delivered early in that period. The times
when people were evacuated from the islands are
shownin Table 2.
2. Gamma (Whole-Body) Dose
Thefallout (where seen) resembled snow or mist
and was deposited relatively homogeneously so
that the individuals on each island were considered to have received about the same estimated
dose of gammaradiation. The children may have
had a somewhathigher dose than that calculated
for the adults because, being smaller, they were
closer to the ground andreceived larger midline
doses. This possibility is supported by the higher
incidenceof early nausea and vomiting and the
greater depression of blood elements in the young
children. The flimsy houses affordedlittle attenuation of the radiation. The whole-body doses were
calculated from measurements with radiation field
survey instruments held 3 ft above the ground,
made within a weekafter the detonation, bv extrapolation to the time of exposure with the energy
spectrum and decay taken into consideration.
Table 2 shows the calculated gammadoses for the
different populations exposed. The degree of hematological depression that developed lateris consistent with the doses calculated. In view of the 47
geometryof exposure, the midline doses to individuals were higher than those obtained with the
usual bilateral exposure of x-radiation.?
3. Skin Dose
The dose to the skin surface was much greater
than the whole-body gammadose becauseofthe
large amount ofbeta radiation absorbed by the
skin. The actual skin doses, although impossible to
calculate, probably amounted to thousands ofrads,
Instrumentreadings
used in dose
Best estimate
of total gamma
375 mR/hr, H +7 days
175
100 mR ‘hr. H+9 davs
280 mR/hr, H+9 days
69
78
40 mR/hr, H +8 days
l+
calculations
dose in air (R)
andtheir range of values, due to different amounts
offallout sticking to different areas, accounted for
the spotty nature and varyingintensity oflesions.
The extensiveness of the beta burns in each island
group correlated roughly with the amountoffall-
out visible on their island (see Table 6). Most of
the skin dose was dueto fallout deposited directly
on the skin, but some was dueto beta radiation
from fallout on the ground (estimated at Rongelap
to be 2000 rads at the level of the dorsum of the
feet, 600 rads at hip level, and 300 radsat the
head,on the basis of continuous exposure and no
shielding).? It was fortunate that the beta radiation had an average energy insufficient to penetrate deeply into the skin and therefore resulted
for the most part in superficial beta burns. The
average beta particle probably did not penetrate
much beyondthe basal layer of the skin (~ 100 4).
However,since epilation occurred in many people,
the region of the hairfollicles must have received
a dose equivalent at least to the minimal epilating
dose of 400 rads of 200-kVp x rays.
4. Internal Dose Calculations
Internal absorption of radioisotopes was due to
inhalation as the radioactive cloud passed over
andto ingestion of food and water contaminated
with fallout, water probably being a majorsource.
Drinking wateris obtained by collecting rainfall
from the roofs into catchments, anda slight rain
was reported on Rongelapthe night ofthe fallout.
Since the cisterns were nearly empty,the dilution
effect was minimal. Water was being rationed at
that time, and it was drunk in spite of warnings
from the health aide. On Rongerik food and water
were better protected from fallout deposition.
Internal levels of radioisotopes absorbed from
the fallout were assessed by numerous radiochemi-