Uncertainties in committed equivalent doses to the thyroid after ingestion or inhalation of different chemical forms of 125-129-131I.

The aim of this study is to reanalyse uncertainties in committed equivalent doses to the thyroid after ingestion of I125-129-131 using the last variability reported for anatomical and physiological parameters of the different ICRP age groups, and to estimate uncertainties after inhalation exposure to different chemical forms of iodine (elemental and organic iodine vapours, iodine loaded particles (study limited to workers for activity median aerodynamic diameters of 1 and 5 mu m)). The 95% confidence interval appears in the range of 7-18 (ratio of 97.5 versus 2.5 percentile values of the log-normal distribution: GSD(4)). The largest uncertainties are observed for I-129 which is due to its long half-life. Because of the small range of beta rays of I125-129 when compared with that of I-131, and the preferential location of iodine within the colloid of the thyroid follicles, the use of calculated doses for a realistic risk assessment is discussed.