An attempt was made to estimate the dimension of direct toxic effects of exposure to Cd on the basis of researches on reproductive parameters in small mammals in natural populations ( on the example of red-backed vole) inhabiting localities of large-scale non-ferrous metal plants and comparison of results obtained with outcome of toxicological experiments ( chronic exposure of female rats to Cd) ). It was expected that at the existing pollution levels, embryonic losses caused by direct toxic

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... ect of Cd shouldn't exceed 7%; however actual losses significantly exceeded extrapolation results. Distinctions observed are caused by impact of external and internal factors influencing reproductive potential on fulfillment of reproduction of animals in natural populations.