AGE-SPECIFIC UNCERTAINITY OF THE 131I INGESTION DOSE CONVERSION FACTOR

Abstract

The production of weapons-grade nuclear materials and their by-products has resulted in a number of releases from United States Department of Energy facilities. 131I, a fission by-product, is one of the most common radionuclides generated and released to the environment. It is known that there are differences in various physiological parameters over all age groups when considering biokinetic modeling of iodine. The establishment of age-specific dose conversion factor uncertainty is necessary for accurate internal dose assessment. The 131I dose conversion factor determined herein is log-normally distributed with varying age-specific distribution characteristics. The two most important parameters for determination of the dose conversion factor, in all age groups, are thyroid mass and iodine uptake fraction. These parameters are assumed to be highly correlated with a relationship that is quite important to dose conversion factor uncertainty. Dose estimates to individuals exposed to radioiodine can be determined more accurately with an increased understanding of the correlation between thyroid mass and uptake fraction. Improved dose estimates following oral intakes of 131I can be made from the consideration of age-specific dose conversion factors and their input parameters.