people compared with four in the Rongelap people is de: expected based on the estimated dose. itely higher than However, we have reviewed the data and have found no reason to change the estimates of the dose to the thyroids of the Utirik people. The number of cases observed may vary above or below the average number expected — the variation being larger as the population n ize decreases. In a small population such as Utirik the difference between the predicted and observed number of cases may be substsntial. Of course, thyroid cancer occurs in populations not exposed to rediation above the natural background. population groups. The incidences of thyroid cancer varies with different For exauple, in children the risk vate (in number of cases per million people per rad per year) varies from 0.5 to 1.5 reported by the United Nations to 5.5 for a group of Americans in New York. It is ‘essential to know the natural incidence in the Marshallese and larger studies of such incidence have been initiated, Even though it was known that the dose to the thyroid glends was higher than to the rest of the body, what wes not known during the earlier years was the degree of sensitivity of the thyroid gland to radiation. Even today, there are many facts about radiation that are not known, despite the large number of scientists that have studied this subject for the past twenty or thixty years. Even less wes known about radiation in 1954 at the time of the exposure to the people on Rongelap and Utirik. Only relativély recently has the degree of sensitivity of the thyroid for developing tumors from vadiation exposure been appreciated. Therefore, the physicians exenining you in past years, based on the best possible medical information available at that time, were being truthful when they said that they did not expect radiation effects to develop in the Utirik people.