Fukuryu Maru 5, with 23 crew members, was exposed 80 miles east of Bikini (see
Appendix VI).
After extensive decontamination procedures, exposed individuals were observed closely for two months (and at frequent intervals thereafter) by special medical teams assembled at the Kwajalein Naval Base, then were resettled
in other islands of the Marshalls group.
Medical problems that arose were

treated on an individual basis as clinically indicated.

C.

Early Clinical Effects

A more detailed summarization of symptoms and clinical findings in the
immediate postexposure period is contained in the 20-year report (1).
Nausea occurred within 48 hours in two-thirds of those on Rongelap, the
most heavily exposed group, with vomiting and diarrhea in 10%.
By contrast,
none of those on Utirik (the least exposed group) and only 5% of those on

Ailingnae (with intermediate exposures) experienced nausea.

About one-fourth of those on Rongelap and Ailingnae complained of skin
irritation and itching; about one-fourth of this group also had eye irritation.
These symptoms were quite probably radiation-induced, mostly by direct
exposure to high-energy beta emitters, since most of the affected subjects
later developed epilation and a few developed conjunctivitis.
Some of these

symptoms may have been aggravated by the caustic effects of the highly alka-

line calcium oxides produced by fireball vaporization of the coral island.
Dermal effects were most pronounced on the scalp, neck, dorsa of the feet,
axillae, and antecubital fossae.
The severity of skin lesions in each group
of people appeared to be proportional to the amount of fallout material observed on their atoll.
Om Rongelap, fallout was described as similar to

snowfall, and it actually whitened the hair and adhered to the skin.

Partial

epilation began within two weeks and eventually affected half of this group.

A less dense, powdery mist fell on Ailingnae and Rongerik, and dermal effects
there were less evident, epilation beginning in three weeks and affecting <20%
of the people.

On Utirik,

the Fallout debris was not visible,

sions or epilation developed.

and no skin le-

Since peripheral blood changes are among the most sensitive and reliable
clinical indicators of radiation damage, these were studied closely.
Significant hemogram alterations soon became apparent among the more heavily exposed
subjects, both on an individual basis and in comparison with mean values for
nonexposed Marshallese controls grouped according to sex and five-year age in-

tervals (see Section III).

In the Rongelap population, absolute neutrophil

counts in all age groups fell 20 to 30% during the second postexposure week
and 50% by the fifth week, gradually returning to normal after one year.
Lymphocyte counts dropped rapidly to about one-half adult control values by the
third day.
By two years they were nearly normal.
Maximum lymphocyte depres-

sions were even greater (25% of control means) in the younger age groups, who

generally exhibited more profound hematologic effects than the adults.
Platelet counts reached a low of about one-third control levels during the
fourth post-exposure week and eventually required more than two years to return to normal.
No significant changes occurred in hematocrit or red blood
cell counts.

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