out by higher urine radioactivity; and (b) that iodine uptake is thought to be greater in infants because higher activity and metabolism of the gland are indicated by the finding of higher protein-bound iodine in infants (237). It seems possible that the thyroid doses received by the two boys who developed myxedema may well have been in the range known to produce such an effect. a risk/rad basis thyroid tumors produced from the calculated doses of the On Rongelap people appeared to be about equal to those reported to have resulted from x-ray exposure. Since a large component of the thyroid dose in the Marshallese is due to radioactive iodine, it is surmised that the presence of more energetic shorter-lived isotopes of iodine with faster dose rates may have at least partly accounted for this finding. (See Section IX.D.) The very slight additional accumulative exposure to the thyroid glands due to residual radiation on the home islands is not thought to have added signifi- cantly to their thyroid dose. - 122.