Thyroid dose estimates for the genome-wide association study of thyroid cancer in persons exposed in Belarus to 131I after the Chernobyl accident

The Chernobyl accident on 26 April 1986 led to a sharp increase in thyroid cancer (TC) incidence in the individuals exposed to radiation in childhood. The major risk factor for TC was exposure to Iodine-131 (I-131). Here, we estimated the thyroid doses due to I-131 intake for 2041 participants of the genome-wide association study of TC in Belarusian people exposed to radioactive fallout from the Chernobyl accident. The following parameter-values specially developed in this study were used to estimate individual thyroid doses: (i) scaling factors for adjustment of the model-based doses, (ii) age and gender diet to characterize I-131 intake, and (iii) area-, age- and gender-specific S-values for the thyroid gland per I-131 decay in the thyroid. The most reliable doses were calculated for 103 people with measured I-131 thyroid activity (the arithmetic mean of 1.2 Gy, median 0.52 Gy), and 275 individuals with detailed residential history and dietary data (the arithmetic mean of 0.41 Gy, median 0.24 Gy). The arithmetic mean of thyroid doses among all studyparticipants was 0.23 Gy (median 0.082 Gy); the highest individual dose was 9.0 Gy. Special attention was paid to the reliability and validity of the obtained estimates, in particular for the individuals without I-131 thyroid activity measurements and individual data on residential history and diet, by comparing those with the doses from other post-Chernobyl epidemiological studies. Overall, the doses estimated in the current study were in reasonable agreement with previously reported thyroid doses. These doses will be used in the genome-wide association study of TC in people exposed in Belarus to I-131 after the Chernobyl accident.

Automated summary

The study estimated thyroid doses due to I-131 intake in Belarusian people exposed to radiation from the Chernobyl accident. The most reliable doses were calculated for 103 individuals with measured I-131 thyroid activity and 275 individuals with detailed residential history and dietary data. Overall, the estimated doses were in reasonable agreement with previously reported thyroid doses.