Thyroid dose assessment for the Chernigov region (Ukraine): Estimation based on131I thyroid measurements and extrapolation of the results to districts without monitoring

Abstract

Based on the results of 131I thyroid activity measurements in three districts of the Chernigov region (Ukraine), individual doses were calculated and an approach of the age dependence of the average thyroid exposure was derived. Using the relationships between the thyroid doses and the 137Cs deposition as well as the location relative to the Chernobyl Nuclear Power Plant (NPP), age-dependent average thyroid doses were extrapolated also for those settlements of this region where no monitoring measurements have been carried out. The highest doses were found in the west of the region with the lowest distance to the Chernobyl NPP. In this part, the highest mean of the thyroid dose in a settlement was 3.3 Gy for infants and 0.5 Gy for adults. The collective thyroid dose was 31,000 and 27,000 person-Gy for children and adults, respectively. Based on this assessment, 140 and 21 excess thyroid cancer cases are predicted for children and adults, respectively. In the years 1989 to 1991, in the whole contaminated territory of the Ukraine 0.4-1.2 cases per 100,000 children were observed. Although the absolute numbers are very small, this indicates the possibility of an increase in thyroid cancer morbidity among children. The same trend also seems to be indicated in the Chernigov region. A careful epidemiological study in the future is necessary to enable a final evaluation of radioinduced cancers in this region.

The Chernobyl Accident and its Consequences

“…Estimates indicate that the doses varied in a wide range from <0.05 mGy to >2 Gy in Belarusian, Russian and Ukrainian individuals of all age groups with averages of <0.3-0.7 Gy in children and individual doses up to 10 Gy [24][25][26][27][28][29][30]. Thyroid doses exceeding 2 Gy were observed almost exclusively in younger children aged less than 4 years [30] and they usually were higher in the residents of rural than in urban areas with similar contamination level [29].…”

“…Thyroid doses exceeding 2 Gy were observed almost exclusively in younger children aged less than 4 years [30] and they usually were higher in the residents of rural than in urban areas with similar contamination level [29].…”

“…According to some surveys, from1% to about 25% of the residents of contaminated territories reported taking KI pills shortly after the accident but the recall rate was low [29,31]. In part this was due to poor preparedness for large-scale accidents such as one that happened at CNPP, and in part to inappropriate information from the authorities.…”

Retrospective dosimetry of Iodine-131 exposures using Iodine-129 and Caesium-137 inventories in soils – A critical evaluation of the consequences of the Chernobyl accident in parts of Northern Ukraine

“…This was possible by comparing our results with thyroid dose estimates based on settlement-averaged results of direct measurements of 131 I in human thyroids performed in 1986 (Likhtarov et al, 1994) and evaluated later by Jacob et al (2006). Direct measurements of thyroid activities after the Chernobyl accident revealed a high variability of individual exposures compared to the results of deterministic model calculations of the mean thyroid exposures; e.g.…”

“…Direct measurements of thyroid activities after the Chernobyl accident revealed a high variability of individual exposures compared to the results of deterministic model calculations of the mean thyroid exposures; e.g. Likhtarov et al (1994). This variability depends e among many behavioural factors e on the small-scale variability of the environmental radioactivity.…”