This paper describes the method for reconstruction of the dose of internal irradiation of thyroid with incorporated 131 I. It is based on a statistical relationship between the mean internal dose estimated from individual thyroid radiometry and contamination around the population point. Using the method estimates of mean thyroid dose from incorporated 131 I were derived as a function of age for each population point of the Bryansk region, along with estimates of collective thyroid dose for all 27 administration districts of the region. For example, for 1.473 million residents of the Bryansk region living in 3,085 population points the collective thyroid dose is estimated at 34,200 people Gy. The largest contribution to the collective dose is made by Klintsovsky (35.3%), Krasnogorsky (22%) and Novozybkovsky (13.1%) districts of the Bryansk region. The obtained results were used in the search of dose relationship of thyroid incidence rate among children and adolescents of 0-17 years at the time of the Chernobyl accident living in the Bryansk region of RF. The analysis is based on 68 cases (47 girls and 21 boys) diagnosed in the assumed post-latent period from 1991 to 1996. The total population of the Bryansk region of 0-17 years at the time of the accident was about 375 thousand persons. The statistically significant estimate of the excess absolute risk for boys was estimated to be 1.5 (0.0, 2.8 - 95% confidence interval (CI)) [10 4 person years Gy] -1 ; for girls - 2.0 (0.5, 3.5 - 95% CI) [10 4 person years Gy] -1 . The excess relative risk per 1 Gy is 12.7 (0.3, 24.5) and 6.5 (1.6, 11.2), respectively. It has been demonstrated that for the period from 1986 to 1990 the detectability of spontaneous thyroid cancers increased by a factor of 5-8 due to the effect of screening.

We present a detailed description of dosimetric data entered in the Russian National Medical and Dosimetric Registry (RNMDR) for emergency workers (liquidators) involved in recovery operations (RO) after the Chernobyl accident. The data on the absorbed doses from external exposure are based on the documents given to liquidators by organizations that performed dosimetric monitoring in the zones of operation. Using the data on external doses currently available in the RNMDR for 119,416 liquidators (78.4% of the total number of 152,325 persons), different statistical characteristics were derived to assess the reliability of the information. The paper also discusses dose distributions according to the date of beginning work in the RO zone [up to 250 km from the Chernobyl nuclear power plant (NPP)], on the distance of the settlement where the liquidators were accommodated or worked from the NPP, and on the duration of their stay in the RO zone. To analyse the reliability of the dosimetric data, the notion of an effective exposure dose rate (EEDR), i.e. the ratio of the dose registered in RNMDR and the duration of stay in the RO zone, was introduced for each liquidator, and corresponding statistical characteristics for the distribution of EEDR depending on the date of entry into the RO zone and distance from the place of residence or work to the NPP were obtained. The analysis for different groups of liquidators shows that the dosimetric information of the RNMDR is, as a statistical aggregate, generally consistent with the data on the radiation situation in the RO zones.