Radiation oncoepidemiology in Russia after the Chernobyl accident: prognostication and facts

This work presents results of complex studying the morbidity and mortality from malignant neoplasms on the territories of Bryansk, Kaluga, Orel and Ryazan oblasts most radiocontami-nated after the ChNPP accident. Complexity of the approach was provided by solving the three basic tasks: assessment of possible contribution of radiation factor into oncomorbidity, i.e. prognostication of mortality and morbidity conditioned by radiogenic cancers; analyzing the development of oncoepidemiological situation (dynamics of morbidity indices) during the period from 1981 till 1994; assessment of relative risks of arising malignant neoplasms among population of indicated oblasts as compared to Russia before and after the ChNPP accident. Calculations models and risk coefficients recommended by the International Commission on Radiological Protection (ICRP) and the Committee on Biological Effects of Ionizing Radiation of USA (BEIR-V) as well as medico-demographic and dosimetric data on studied regions are used in the prognostication. In consequence of the prognostication the life attributive risk for the majority of oncodiseases was demonstrated not to exceed 5%, except thyroid cancer for which the attributive risk is expected to peak in Bryansk oblast and to reach 18-20% for adults and 45-50% for children. By this is meant that each fifth thyroid cancer among adults and each second cancer among children will be radiation-induced. Analysis of risks and oncomorbidity indices among residents of contaminated territories before and after the accident allows to conclude that the forming the levels of oncomorbidity available at present, their structure and dynamics occurred primarily under influence of factors existing before the accident. As a result of the analysis of all three aspects of given problem the conclusion about the lack of statistically reliable effect of radiation factor on oncomorbidity is made. Levels of onco-morbidity and oncomortality in contaminated regions reflect mainly the common tendency of changing these indices on Russia as a whole. The conclusion made is generally in agreement with the data of world practice on latent periods of induction of radiogenic cancers and values of radiation effects for levels of irradiation to which the population living on contaminated territories is exposed.