Ukrainian-American thyroid project: review of scientific publication on epidemiology, dosimetry and iodi ne protection

Abstract

Introduction. For a detailed study of the medical consequences of the Chernobyl accident (ChNPP), a joint Ukrainian-American project ≪Scientific protocol for the study of thyroid cancer and other thyroid diseases in Ukraine following the Chornobyl accident≫ (Project) has been implemented. The Project provides the survey of Ukrainian residents: a) who at the time of the accident at the ChNPP had been permanently resided or temporarily had been stayed in the most radiation-contaminated areas of Zhytomyr, Kyiv and Chernihiv regions; b) who were up to 18 years of age at the time of the accidentt at the ChNPP; c) whom the thyroid radiometry was performed during the first weeks after the accident at the ChNPP; d) which were selected by random sampling. A cohort was formed in 13 243 individuals who during the 1998-2016 period passed 5 screening examinations, which included: an overview of the endocrinologist, ultrasound and hormonal tests of thyroid, fine needle aspiration biopsy and surgical treatment (if necessary), and also the determination of the level of iodine excretion from urine. Objective. Bibliographic review of the scientific publications based on the results of the Project. Results. In 2 publications on general issues, the methodology of the organization and implementation of the Project was outlined. In 8 publications on epidemiology, the procedure of forming the cohort for the Project, the procedure of a screening survey and the characteristics of members of the cohort were presented; the prevalence was analyzed and the relative risk for the main types of thyroid pathology (3612 cases) among the members of the cohort, related with the place of permanent residence, age at the time of examination and sex, was established. In 7 publications on dosimetry the dynamics of 131I and 137Cs deposition on the surface of the soil was reconstructed, the dosimetric model of the thyroid exposure was developed and individual thyroid doses for 13 204 cohort members were calculated; the influence of dose errors on the radiation risks assessment was analyzed. In 4 publications on iodine secretion both the iodine deficiency among cohort members and the dependence between the absorbed doses of thyroid irradiation and iodine status were shown. Conclusion. In the published papers a methodology for a long-term clinical and epidemiological cohort study among people who were exposed to radiation due to the accident at the ChNPP was presented. Long-term follow-up of the cohort members allows for a reasonable estimate of the risk of thyroid cancer and other thyroid pathology, depending on the dose of thyroid radiation by radioiodine.