Assessment of the Risk of Thyroid Cancer in Rural Settlements in the Areas of the Bryansk Region (Russia) Affected by the Chernobyl NPP Accident

Thyroid cancer is one of the most important medical problems. The disease often occurs in regions that have been exposed to radiation and where there is insufficient iodine in nature. Adequate intake of iodine is necessary for the functioning of the thyroid gland and the development of the mammalian fetus. Thus, in 1990, a special International Council for Combating Iodine Deficiency Disorders was established at WHO. Since 1990, the incidence of thyroid cancer in the world has increased by 169% (Dang et al., 2020). It can be assumed that such an increase is associated with early detection of the disease. However, in countries with high human development index (HDI), where the detection rate of the disease is 4-5 times higher than in low HDI countries, this indicator does not correlate with mortality from thyroid cancer. In our opinion, this is because the food sources must be considered. As local foods to the diet varies significantly between urban and rural areas, it is important to compare cases of thyroid cancer in them. For example, in rural areas of the United States, the overall incidence of thyroid cancer is 14% lower than in cities (McDow et al., 2020).

For the Bryansk region (the most affected by the Chernobyl accident in Russia) data on thyroid cancer also show a difference: in 27 regional centers (67% of the population), an estimate of the thyroid cancer incidence is 20.9 per 100 000 people per year (period from 1990 to 2019), while for other localities the rate is much lower (16.3). However, mortality from thyroid cancer in rural areas is 46% higher than in urban areas (0.89 and 0.60, respectively). Using a specialized GIS developed to study natural and man-made geochemical factors responsible for the spread of endemic diseases, we zoned the territory according to evaluated risk (Baranchukov et al., 2019).

Assessment of the risk of thyroid cancer turned out to be more effective for rural settlements (excluding the most contaminated area, where special measures were taken): the correlation between the calculated total natural and man-made risk and the incidence of thyroid cancer was significant and higher in rural areas (r=0.54, p=0.05, n=25) than in the main urban areas (r=0.27; p=0.17). The result of the study shows that the prevalence of thyroid cancer is associated, first of all, not with the level of diagnosis, but with the structure of nutrition, which ensures the entry of elements into the human body.

This study was funded by RFBR and BRFBR, project #20-55-00012.

References

Deng Y et al. Global Burden of Thyroid Cancer From 1990 to 2017. JAMA Netw Open. 2020;3(6):e208759. Published 2020 Jun 1. doi:10.1001/jamanetworkopen.2020.8759

McDow AD, et al. Impact of Rurality on National Trends in Thyroid Cancer Incidence and Long-Term Survival. J Rural Health. 2020 Jun;36(3):326-333. doi: 10.1111/jrh.12374. Epub 2019 May 17. PMID: 31099945

Baranchukov V et al. Application of Geoinformation Technologies for minimization of thyroid gland diseases in the impact areas of the radioiodine fallout, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9000, https://doi.org/10.5194/egusphere-egu2020-9000, 2020