Assessment of radiation risks of cancer incidence and mortality among participants in the consequences of the Chernobyl accident

This paper presents the results of a study by the National Radiation and Epidemiological Registry on the assessment of radiation risks of the incidence of solid malignant neoplasms, mortality from solid malignant neoplasms and the incidence of leukemia (with the exception of chronic lymphocytic leuke-mia) in cohorts of Russian participants in the consequences of the Chernobyl accident (liquidators) over a 40-year follow-up period. The number of cohorts is more than 67 thousand. The average age at the time of entry into the Chernobyl zone was 34 years, and the average individual dose of external gamma radiation to the whole body accumulated during the period of work of the liquidators was about 0.133 Gy. In the studied Russian cohort of liquidators, there were statistically significant radiation risks of incidence of solid malignant neoplasms and mortality from solid malignant neoplasms, steadily in-creasing over the past 12 years of follow-up, from 2012 to 2024. During the maximum follow-up period, from 1992 to 2024, the estimates of excess relative risk coefficients ERR/Gy were 0.76 at 95% CI (0.46; 1.09) and 0.79 at 95% CI (0.40; 1.21) for incidence and mortality, respectively. Nonparametric estimates of relative radiation risk (RR) in dose ranges for both solid malignant neoplasms and leuke-mias in the cohort of liquidators are statistically significant only for doses of 0.150 Gy or more. For radiation doses of less than 0.150 Gy, the linear threshold-free model of radiation risk is conservative, i.e. this leads to overestimated estimates of radiation risks. A statistically significant radiation risk of leukemias among liquidators was observed only during the first 11 years after the Chernobyl accident, from 1986 to 1997, ERR/Gy=4.41 at 95% CI (0.24; 14.23). Further, until 2024, the radiation risk of leukemias was not detected. Further studies of radiation risks related to the localization of malignant neoplasms in the Russian cohort of liquidators are of great practical importance, as based on such estimates, a methodology for evaluating effective doses can be developed and methods for optimizing radiation protection for Russian irradiated cohorts can be implemented.