Calculation of the radiation induced cancer in the Russian population after the Chernobyl accident by means of a well established molecular biological model

This thesis puts emphasis on the evaluation of radiation effects from the Chernobyl accident inducing cancer in the Russian population. Certainly, the release of radionuclides from the nuclear reactor explosion caused higher radiation levels than there existed before the accident. The data of radiation exposure are obtained from several publications in different measured units. Thus the exposure dose rates have to be converted into the same dose rate unit (mGy/a) as the unit of fit parameters. The data of population in the year of the accident was also obtained from several reports. The calculation was done in matrices which are composed of 2,500 pixels. The exposure and population data were arranged into pixels. Since there was no epidemiological data of the Russian population before the Chernobyl accident, the epidemiological data set, ARIP data, was adjusted by using the Random Coincidence Model which involves the damage of nucleotides caused by spontaneous damage and radiological induced damage. This model has been approved to explain hormetical biopositive effects of the late effect of radiation. Beside this, the enhanced repair capacity related to enzyme production and scavenger mechanisms is also included in the formula. To calculate the radiation induced cancer, an excess of dose rates above background radiation from the Chernobyl accident was applied into these epidemiological data fits. For convenience, programming by using Igor Pro program was specially written with adjustable interfaces. Fit parameters for low LET radiation obtained from fitting of the epidemiological study of ARIP were used as constants. The radiation induced cancer is calculated both with and without the influence of the enhanced repair capacity. The generation rate of malignant cells and the tumor mortality were achieved as results. Using the epidemiological data set of the U.S. population, ARIP data set, the results of the Russian population can be inferred from that of the U.S. population by conservative estimation. It is found that the number of the generation rate of malignant cells is affected not only by dose rates varied by time but also by the enhanced repair capacity. Since several types of tumor progressed through the 5th transformation step, the summation of the 5th steps of the generation rate of malignant cells is presented as results. Calculating with the repair capacity, an excess of dose rates in a range of 0.007-14.31 mGy/a above background radiation can reduce about 0.03 % to 36.3 % of the generation rate of malignant cells. When an excess of dose rates is in a range of 14.32-20.12 mGy/a above background radiation, with the influence of the enhanced repair capacity, either reduction or no reduction of the generation rate of malignant cells is observed. No reduction of the generation rate of malignant cells is observed when the excess of dose rates is higher than 20.12 mGy/a above the background radiation. It is seen that the dose rate in each time interval has an influence on the reduction of the generation rate of malignant cells in this dose rate range. The dose rate in the first time interval must be high enough to stimulate the repair system for resisting the damage in the next exposure. The reduction of the generation rate of malignant cells is not observed in any ranges of dose rates without the enhanced repair capacity. At low doses and low dose rates, cellular repair mechanisms are available to compensate for the damage. (author)