Genetic effects and biological concentration of radionuclides in plants and animals after Chernobyl catastrophe.

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South of Belarus is highly radiocontaminated even in 19 years after the Chernobyl catastrophe in 1986, and consequent environmental changes are stored in the soil, plants and animals. The major radionuclides in the contaminated areas are ^<137>Cs and ^<90>Sr, and their physical half lives are 30.2 and 28.9 years, respectively. Slow self-cleaning efficiency of the soil (estimated half life is 24 years) resulted in the long term radiocontamination in the closed environment. It is expected that the radionuclides are concentrated by the food chain into the organisms which are living in the contaminated area, and radionuclides remain in the irradiated organisms not only externally but also internally for long periods. The evidence of radiation effects for the organisms living in the contaminated area were reported by many scientists. Chromosome aberration rate in mice and frogs were increased twice higher than before catastrophe. But most of reports were not shown the exact radioactivity and period of exposure. The exact radioactivity in organisms should have been known to assess the long term low dose rate and low dose internal and external radiation effect.We measured the ^<137>Cs radioactivity and its distribution in the plants (trees, berries) and animals (insects, frogs, moles, mice) in the highly contaminated area (Masani village, Gomel region, Belarus) and the low contaminated area (Babchin village, Gomel region, Belarus). The ^<137>Cs activity of mouse in 2005 was compared with mouse of 1997. The remaining rate of ^<137>Cs in organs at 2005 was about 2%. And it was estimated that the ecological half life was 1.511 years. Additionally, we tried the quantitative detection of contaminated radionuclides-induced DNA double-strand breaks by gamma-H2AX foci in mouse organs living in contaminated area. But the signal of gamma-H2AX foci was not detected even in animal cells in highly contaminated area.