Assessment of radiation risks of morbidity and mortality for the main classes of non-cancer diseases among participants in the consequences of the Chernobyl accident

The main long-term effect of ionizing radiation in low doses on human health is currently considered to be an increase in the incidence of malignant neoplasms among exposed individuals. However, the International Commission on Radiological Protection (ICRP) in 2007 noted the "potential importance of monitoring the incidence of non-cancer diseases" and stated that there was insufficient evidence of their radiation risks at radiation doses of less than 0.2 Gy. In previous studies of Russian partici-pants in the liquidation of the consequences of the Chernobyl accident (liquidators), registered and observed since 1986 in the system of the National Radiation and Epidemiological Registry (NRER), it was shown that the radiation risks of non-cancer diseases can make a significant contribution to the overall radiation damage to human health, comparable with damage from malignant neoplasms. Therefore, their study is important from the point of view of radiation protection. The purpose of this work is to update the results of the assessment of radiation risks of non-cancer diseases of liquidators obtained during the period of NRER observations in 1988-2019, taking into account new data accu-mulated by the end of 2024. Radiation risk estimates were obtained within the framework of a linear threshold-free risk model and in the form of nonparametric estimates of relative risk (RR) in dose groups. The most important diseases in further calculations of possible radiation damage to liquida-tors are diseases of the circulatory system (I00-I99) and diseases of the digestive system (K00-K93), since radiation mortality risks have been identified for these diseases with coefficients ERR/Gy=0.49 at 95% CI (0.28; 0.71) and ERR/Gy=0.73 at 95% CI (0.20; 1.34), respectively. These estimates are 4 and 7 times higher than the estimates obtained earlier in the Japanese cohort of people who sur-vived the atomic bombings in 1945, and correspond in magnitude to the ERR/Gy estimates for solid malignant neoplasms recommended by the ICRP to substantiate the norms and rules of radiation protection. At radiation doses of less than 0.150 Gy, the estimated linear non-threshold risk model of radiation mortality risks from diseases of the circulatory system is conservative, i.e. leads to overes-timated estimates of radiation risks. The effect of multimorbidity on the assessment of radiation risks of non-cancer diseases may be significant and requires further investigation.