Administering stable iodine is an effective strategy to protect the thyroid in case of an accidental release of radioiodines. 131I is the most concerning iodine isotope due to its amount in the reactor vessel and its relatively long half-life. These factors result in 131I dominance in the total thyroid dose, and many studies focus on this isotope. The protective effect of stable iodine for other iodine isotopes is not well documented, and this study examines 132I and nine other isotopes with longer half-lives. The predicted trend in protective effect is estimated using a biokinetic toy model of the blocking effect. Then, the Zanzonico and Becker model (2000) is implemented for the inhalation of aerosol type F with an AMAD of 1 μm. The protective effect for administration of 130 mg KI is tabulated for administration time between 96 hours prior to the intake and 48 hours after the intake for 10 isotopes including 131I. It has been found that, regardless of the timing of stable iodine administration, the protective effect is similar for 124I (T1/2 ~4.2 days), 131I (T1/2 ˜8 days), and other isotopes with longer half-lives. For isotopes with shorter half-lives, the relative protective effect (normalised to the respective 131I values) depends on the timing of stable iodine administration and the isotopes' half-life. If stable iodine is taken after intake, the shorter the half-life the lower the protective effect. If stable iodine is taken before intake the opposite applies. For stable iodine administration 48 hours before the intake the protective effect is 93% for 132I and 73% for 131I, for administration 24 hours before the intake these values are 99 and 95%. Taken 6 hours after the intake the protective effect is only 9% for 132I but still 51% for 131I. The results obtained here could be considered for emergency planning and preparedness as well as communication with the public in case of accidental radioiodine release.
Broggio et al. (Mon,) studied this question.