of the analog. Estimates of the_potential dose to the thyroid from ingestion of I-131 contaminated cow's milk are made utilizing an empirical relationship between gamma fallout ficld intensities and T-131 peak concentration in cow's milk developed by Knapp (6), Knapp found that after a sincle dry deposition of radioactive fallout on pastureland the level of I-131 in the fresh milk of dairy cattle reached a maximum value within 4 days and thereafter decreased exponentially with a half reduction time of about 5 days. The maximum level of I-131 in the fresh milk, L,,, was related to the external gamma radiation level by the relation Trax = (26,000%) to (96,000%) pei/2 where Y% is the open field, external gamna dose rate at 3 feet above the ' ground surface, 24 hours following detonation, expressed in mr/hr. Further, child consumes 1 liter of contaminated cow's milk per day, the fraction of ingested I-131 reaching the thyroid is 0.3, and the half reduction time of I-131 in fresh milk is 5 days, Knapp provides the following relation between the maximum I-131 level in the milk and the dose to the thyroid we ee ad wre eR eh oh BRALtt by assuming the mass of the thyroid to be 2 grams (1 year old child), the D = (1.71 x 1074) Inax rads Thus, if Tix lies in the range of (26,000 %) to (96,0007) then D = (4.4%) to (16.4 99) rade | Since the gamma exposure rate at H+1 hour, rather than at H+24 hours, is normally obtained in the scaling technique, the above equations have been ’ modified, assuming a t71-2 decay dependence, to the following