A radioecological model for thyroid dose reconstruction of the Belarus population following the Chernobyl accident.

A radioecological model was developed to estimate thyroid exposures of the Belarus population following the Chernobyl accident. The input of the model includes an extensive data set of the (137)Cs activity per unit area deposited during the Chernobyl accident, the rainfall data for different regions of Belarus, the (131)I/(137)Cs ratio in the deposit and the start of the grazing period in Belarus in April/May 1986. The output of the model is the age-dependent thyroid exposure due to the intake of (131)I with fresh milk. Age-dependent average thyroid doses were assessed for selected regions of Belarus. The maximum thyroid doses were estimated for the inhabitants of Gomel oblast where the highest deposition was observed among the regions considered here. The lowest doses were estimated for Vitebsk oblast with the lowest level of depositions. The mean exposures for the oblasts of Grodno, Minsk, Mogilev and Brest were very similar. The results were compared with estimations of thyroid exposure that were based on (131)I measurements in human thyroids, and they are in good agreement. The model may be used for the assessment of thyroid doses in Belarus for areas where no (131)I measurements are available.