A dynamic model of the global iodine cycle and estimation of dose to the world population from releases of iodine-129 to the environment

A dynamic linear compartment model of the global iodine cycle has been developed for the purpose of estimating radiological impacts on the world population from releases of ¹²⁹I to the environment. The time-invariant fractional transfer rates, which describe the transport of ¹²⁹I between environmental compartments comprising the atmosphere, hydrosphere, lithosphere, and terrestrial biosphere, are estimated from an analysis of available data on concentrations for naturally occurring stable iodine and data on the global hydrologic cycle. The global radiological impacts on man from a given release of ¹²⁹I are estimated from the calculated compartment inventories as a function of time and models for the intake of iodine by a reference adult. For a constrant population of 12.2 billion, the estimated worldwide complete population dose commitment to the thyroid is 76 man-Sv/GBq (2.8 × 10⁵ man-rem/Ci) released. Estimated values of the incomplete population dose commitment at various times after a global-scale release to the atmosphere are also presented.