Reconstruction of 131I deposition density in regions of Belarus with estimation of thyroid doses from inhalation of 131I

The relationship between I-131 and Cs-137 activity concentrations in 213 soil samples taken in 10 administrative districts of Belarus was derived. Analysis of the relationship shows a decreasing trend in the I-131/Cs-137 isotope ratio values with increasing Cs-137 content in soil. Using the [I-131-Cs-137] relation obtained and the data on Cs-137 contamination of settlements the I-131 deposition density was evaluated for 1080 settlements situated in the area of investigation. Based on these assessments thyroid doses from inhalation of I-131 were estimated. According to the results, the thyroid doses for the adult population vary from 5 to 40 mSv, the median dose is about 12 mSv. Uncertainties in the calculation of thyroid doses, based on the procedure applied, are discussed.