Comparative analysis of thyropathy incidence rate in children of the Kaluga oblast exposed to iodine-131 at different time of their life from conception to 7 years old

The highest radioactive fallout in the Kaluga oblast contained iodine-131 following the Chernobyl accident was registered in south-west Zhizdra, Ulianovsky and Khvastovichi rayons, characterized by moderate iodine deficiency. Radioiodine in measurable quantities was detected there from 29 April to 28 July 1986. The purpose of the study is to compare incidence rate of thyroid disorders registered during 12 years after July 1986 in permanent residents of the rayons, exposed to radiation at different time of their life - from conception to 7 years old and in unexposed children of the same age. The cohort study was carried out. The incidence rate was higher in those who was exposed to radioiodine-131 in increased age regardless simultaneous decrease of absorbed dose to the thyroid. Thyropathy incidence rate in children unexposed to radioiodine was 2.5-3.4 times lower, however, it was detected more frequently in people of increased age. This increase is caused by iodine deficiency. Conclusions. In children exposed to radioidine at different time of their life - from conception to 7 years old - increased incidence of thyroid diseases was caused by synergistic action of radioiodine and iodine deficiency.