Problem of assessing genetic consequences caused by low-level irradiation

Study of the regularities in the induction of the cytogenetical injuries using test-systems with different sensitivity to radiation was performed. It has shown that dose-effect relationship is of a non-linear character within low exposure range and has a dose-independent part. A comparison of the newly found of the empirical curve with the results obtained for other objects (human lymphocytes, fibroblasts of Chinese hamster, Vicia faba seedlings, etc.) allows an important conclusion that the dose dependence of the output of radiation-induced cytogenetic disturbances is non-linear and universal in nature, varying for different objects only in dose values at which changes in the dependence character occur. These findings clearly the invalidity of linear extrapolation of effects observed at doses of above 50 cGy to a zero dose. Since genetic effects observed at low doses are provided by features in cell response to weak external influence rather than by damaging action of ionizing radiation or other factors of physical and chemical nature, a correct estimation of the genetic risk in this most important, in terms of practical application, case can only rely on a clear knowledge of the mechanisms governing the cellular response to low-dose irradiation