Six or seven hours after the shot the American servicemen on Rongerik noticed a mistlike fallout of highly radioactive dust. The wind had veered enough to carry the atomic cloud over the occupied islands of Ailinginae, Rongelap, and Rongerik. In the anxious hours which followed no one could say how much damage had been done.
The Americans on Rongerik had had some education in the dangers of radioactivity. They washed themselves, put on extra clothes, and remained inside of the aluminum huts as much as possible. These actions helped to protect them against beta ray burns on the skin. The Marshallese on Rongelap and Ailinginae knew nothing of the danger and took no precautions. Many of them suffered quite severe skin burns.
All of the exposed persons were evacuated to Kwajalein as soon as the Task Force facilities would permit. But it was not until a week or so after the explosion that arrangements could be made for men with radiation measuring instruments to tour the atolls and determine what the levels of exposure had been.
On the southern tip of Rongerik they measured the activity and calculated that the American servicemen had received approximately 78 roentgens. This was good news because a dosage of 50 to 100 roentgens is not lethal and only in rare cases leads to any sickness. In any event full recovery could be expected within a few days.
As they prowled around Rongerik atoll, the measuring crew found places where the radiation levels had been much higher. At the northern end a person would have received more than 200 roentgens.
On Ailinginae the measured values were comparable to those on Rongerik. The estimated dosage to the Ailinginae people was 69 roentgens.
On Rongelap the situation was much worse. Measurements in the southern part of the atoll showed that the Rongelap people had gotten a dose of about 175 roentgens. Such a dose would not be fatal, but at least some of the people would probably be sick.
The crew then went on to explore the rest of the atoll. As they moved north, the dose levels rose higher and higher. In the middle of the atoll, only ten or fifteen miles from the inhabited part, a person would have received 400 roentgens of radiation. At this level he would have a fifty-fifty chance of surviving.
On the northern tip of the atoll, about thirty miles away, the dose would have been over a thousand roentgens. Such a dose means certain death in less than a month.
The following table contains a summary of what happened: