Analysis of the Dynamics of Mortality of Liquidators of the Consequences of the Accident at the Chernobyl NPP - Workers of the Atomic Industry of Russia

Abstract

Purpose: Assessment of the health of persons working under the influence of certain adverse environmental factors.
 Material and methods: The work includes all male liquidators registered in the Sectoral Register of persons exposed to radiation as a result of the accident at the Chernobyl nuclear power plant. This is about 18.5 thousand people. More than half of them have a verified dose load, all of which were exposed to radiation while working in the 30-km zone of the Chernobyl NPP. At this stage of the study, estimates were obtained for the corresponding retirement intensity function for two cohorts of liquidators – 1986 and subsequent years of work.In order to assess the dynamics of the age-specific mortality of the liquidators, the data for the years 2000 and 2014 are considered. It did not make sense to take earlier years due to the relatively young age of the liquidators at that point in time. The second estimate is related to exactly 15 years – half the entire period of observation of the register. 2014 turned out to be more preferable compared to 2015 due to the fact that it was in 2014 that a significant number of people were deregistered and thus dropped out of consideration.
 Empirical analysis methods are used – survival curves are considered (data such as the lifetime) both in terms of morbidity and mortality. And a comparison is made of the curves obtained in different rank groups. For fitting curves, risk functions of various parametric distributions constructed using the likelihood function can be used. The main problem of this analysis is a large number of censored data at this stage of the study.
 Results: The death rate of the liquidators differs significantly from the death rate of the male population of the Russian Federation, however, this difference decreases with time, primarily due to a decrease in the death rate of the population in the Russian Federation. If the trends in the dynamics of age-specific mortality in the Russian Federation correspond to global standards, which corresponds to a positive dynamic, the dynamics of the age-specific mortality of the liquidators is paradoxical, which primarily concerns the cohort of liquidators of 1986. The weather smoothed mortality of the liquidators of 1986 exceeds that calculated for all the liquidators of the register, which may indicate the presence of some additional factors determining the health of this group of persons. By the years 2007–2010, a significant increase in the slope of the mortality curve is observed as a sign of the cohort selection, relegation of the weaker ones first. Using the Kaplan –Meier method, survival curves for cohorts were constructed, and the presence of significant differences in their mortality was shown.