ERR 114 RADIATION STANDARDS, INCLUDING FALLOUT Federal Radiation Council Report No. 2 gives the following guidance for iodine 131. Range I — 0-10 pyc per day Range II — 10-100 suc per day Range IIIT—100-1000 puc per day An average daily intake at the upper limit of range II corresponds to the radiation does which is considered to represent an acceptable exposure level from normal peacetime operations (the RPG). It can readily be seen that average iodine 131 intakes during certain periods were in range III. Federal Radiation Council Report No. 2 states, “Transient rates of intake within this range (range ITI) could occur without the population group exceeding the RPG if the circumstances were such that the annual average intake fell within range [I or lower.” It can be shown that such was the ease for all of the stations as well as the national average during the period. Additionally it is useful to consider estimates of the radiation dose to the thyroid from iodine 131 during this period and compare these estimates with the RPG. ESTIMATES OF THYROID DOSE The Federal Radiation Council Report No. 2 provides a relationship between iodine 131 intake and the thyroid dose. This report estimates that an annual average daily intake of 80 uyc of iodine 131 would result in a dose of 500 milliroentgens in 1 year to infants in which the thyroid weight is taken as 2 grams. The dose estimates in table II were developed on the basis of the above relationship between intake and dose assuming 1 liter of fresh milk consumption per day for the 5-month period of iodine 131 fallout and that milk is the only significant source of intake. It must be clearly recognized that these dose estimates apply only to infants who consume a liter of fresh milk daily and whose thyroid weight is 2 grams. These conditions apply approximately to the age group from 6 to 18 months. Children under 6 months of age usually consume some type of formula other than whole fresh milk. With children above approximately 18 months of age, the dose to the thyroid would become progressively smaller with the increase in size of the thyroid to a value in the adult of approximately one-tenth the value in infants. Using data from the U.S. census of 1960" it is estimated that the age group from 6 to 18 months represents approximately 2.3 percent of the total population, or approximately 4 million infants. On this basis, the estimated infant population covered by the pasteurized milk network is 1,387,900. Since the network samples are collected from processing plants, and the iodine 131 activity is extrapolated back to the time of collection of the sample, the interval between production of milk and the time samples are collected at the processing plant is approximately 2 days. Infants living on farms and drinking raw milk could have had somewhat higher intakes of iodine 131, since the time interval between production and consumption could have been a matter of hours. This might, in some instances, have resulted in as much as 25-percent increase in the iodine 131 intake and the resultant thyroid doses. The average thyroid dose to infants with a 2-gramthyroid during the period of September through January 1962 was 160 milliroentgens. Figure 1 provides a percentage distribution of the infant population according to estimated thyroid dose from iodine 131. September 1961—January 1962. It can be seen that the high- est average doses were less than four times the average. Figure 1 also shows the annual RPG for the thyroid to be applied to the averages of suitable samples of exposed population groups. All of the estimated thyroid doses were less than the annual RPG. Segtate RAN Sy Ses iaERei: SMR,