LEVELS AND RELATIVE RISKS OF MORTALITY OF CHORNOBYL CLEAN-UP WORKERS IN 1986-1987 YEARS FROM MAIN NON-NEOPLASTIC DISEASES (OBSERVATION PERIOD 1988-2021).

The emergency destruction of the 4th reactor of the Chornobyl nuclear power plant necessitated large-scale emergency work, which involved large contingents of specialists. Analysis the mortality of Chornobyl clean-up workers isan important and relevant basis for planning medical protection measures in conditions of a potential threat ofemergency and other radiation situations.The objective of this work is to determine the levels and relative risks of mortality of Chornobyl clean-up workers in1986-1987 years from major non-tumor diseases depending on the received dose of radiation exposure, taking intoaccount age and time after the accident (period of epidemiological studies 1988-2021).

Materials and methods: The cohort of Chornobyl clean-up workers in 1986-1987 years with a known dose of external γ-irradiation of the whole body, totaling 64,490 male, was divided by age at the date of the accident at theChornobyl nuclear power plant and dose of external γ-irradiation of the whole body. Epidemiological analysis of mortality from non-tumor diseases was conducted for the entire post-accident period and in dynamics over five-yearmonitoring periods.

Results: The highest mortality rate, regardless of age, on the date of the Chornobyl disaster, were from diseases of thecirculatory system, of the digestive and respiratory systems. For Chornobyl clean-up workers 18-39 years on the dateof the accident, relative risks of mortality from non-tumor diseases over the entire observation period were significantly higher in all dose subgroups (from 0.05 Gy to 0.7 Gy) compared to the dose subgroup < 0.05 Gy. In the period1993-1997 (6-10 years after the Chornobyl accident), significantly higher relative risks of mortality from diseases ofthe circulatory system (pulmonary heart and pulmonary circulatory disorders, cardiomyopathy, myocardial infarction)were found; in 26-30 years - from cerebrovascular diseases, including cerebral infarction. The indicated reliabledose-dependent relative risks are characteristic of all dose subgroups relative to the subgroup with a dose < 0.05 Gy.

Conclusions: The overall mortality of Chornobyl clean-up workers from non-tumor diseases tends to increase. Theresults of the risk analysis of dose dependent mortality in the Chornobyl clean-up workers cohort showed a highersensitivity to ionizing radiation of persons of the younger age group (18-39 years old at the date of the accident).The most dangerous period of relative dose-dependent risk of death of Chornobyl clean-up workers due to non-tumordiseases was established - 6-10 years after radiation exposure for all dose subgroups (from 0.05 Gy to 0.7 Gy) relative to the subgroup with a radiation dose < 0.05 Gy.