Evaluation of stable iodine status of the areas affected by the Chernobyl accident in an epidemiological study in Belarus and the Russian Federation

Variation of the stable iodine supply was evaluated in the soils of around more than 700 settlements in the regions (oblasts) of Belarus and the Russian Federation contaminated after the Chernobyl accident. It involved the use of regional information on iodine content in different types of soil cover, biogeochemical criteria of iodine deficiency in food chains, and the available soil maps.The proposed method enabled to create overview maps that differentiated study areas by iodine supply level and to rank rural settlements according to iodine content in soil cover. The area-weighted concentration of stable iodine in the soil cover used for farming was estimated. Median iodine concentration was found to be highest in the settlements of Orel and Tula oblasts (3.6 mg/kg), lower in Gomel and Mogilev oblasts (3.0 and 2.3 mg/kg, respectively) and lowest in Bryansk and Kaluga oblasts (1.3 mg/kg). Estimates of iodine availability from different types of soils were corrected for volumetric weight and adjusted for the type of settlement in order to assign the stable iodine status for each subject in a case–control study of thyroid cancer risk following the Chernobyl accident. The epidemiological study found a significant modifying effect of iodine deficiency on the risk of thyroid cancer following exposure to radioiodines.

Research Highlights
► soil map-based method to evaluate stable iodine status of settlements was presented.
► the approach enabled differentiation of individuals by stable iodine status.
► risk of radiation-induced thyroid cancer depended on stable iodine status of the individuals.
► approach may be used for selection of settlements for preventive thyroid cancer prophylaxis.