Includes bibliographical references (page 18). July 1965.

Introduction -- Methods -- Results -- Discussion -- Concluding remarks. Balance studies of environmental iodine 131 over a period of 30 days are reported in children ranging from 1 to 6 years of age. Calculations of expected thyroidal accumulations of iodine 131, based on accepted exponential models and thyroidal function factors, are compared with thyroidal iodine 131 measurements performed in a low-background facility. The measured values were lower by a factor of 2 than the calculated accumulation of iodine 131, suggesting a lesser uptake and/or more rapid turnover of iodine in children. The difficulties involved in this type of environmental study and recommendations for improved methodology are discussed.