Calculations of individual doses for Techa River Cohort members exposed to atmospheric radioiodine from Mayak releases

Time-dependent thyroid doses were reconstructed for over 29,000 Techa River Cohort members living near the Mayak production facilities from I-131 released to the atmosphere for all relevant exposure pathways. The calculational approach uses four general steps: 1) construct estimates of releases of I-131 to the air from production facilities; 2) model the transport of I-131 in the air and subsequent deposition on the ground and vegetation; 3) model the accumulation of I-131 in environmental media; and 4) calculate individualized doses. The dose calculations are implemented in a Monte Carlo framework that produces best estimates and confidence intervals of dose time-histories. Other radionuclide contributors to thyroid dose were evaluated. The I-131 contribution was 75-99% of the thyroid dose. The mean total thyroid dose for cohort members was 193 mGy and the median was 53 mGy. Thyroid doses for about 3% of cohort members were larger than 1 Gy. About 7% of children born in 1940-1950 had doses larger than 1 Gy. The uncertainty in the I-131 dose estimates is low enough for this approach to be used in regional epidemiological studies. (C) 2017 Published by Elsevier Ltd.