toda} D. tIlIodine-131 Background Information - Approximately 0.15 million curies (a "curie" corresponds to 2.2 million million disintegrations per minute) of iodine-131 are produced for each kiloton TNI equivalent of energy released by fission. If the total yield of the explosion is large enough, the iodine-131 along with other radioactive materials is largely swept into the upper atmos- phere (stratosphere) and, since iodine-131 has a half-life of only eight days, a large part of it will decay before being deposited on the earth, On the other hand, iodine-13]1 that remains in the lower atmos- phere (troposphere) will be deposited relatively quickly and can enter the food chain. Milk is the principal mode of entry of iodine-131 into the body where it is selectively deposited in the thyroid gland. The assumption is usually made that 30 percent of iodine-131 ingested is deposited in the thyroid no matter what the size of this organ may be 10... Thus, an infant's thyroid gland of about two grams weight would receive 10 times more radiation dose than the 20 gram aduit's thyroid for the same amount of fodine-131 ingested. For this reason calculations of radiation doses from iodine-131 for the general population are based on those for the infant rather than the adult. Direct measurements of iodine-131 in milk were not made around the Nevada Test Site during earlier times of testing since it was the consensus of scientists within and outside the AEC and Government that 14. (7