The depth-distributions and tracks of 200keV N+and 110keV Fe+ions in cells have been calculated with Moose Carlo method.The calculated results are similar to those measured by RBS.The dTth of ions obtained from the calculation or the experiments is all smaller than the length of a cell.The distributions of cascade atoms produced by 200keV N+ implanted intO a cell model have also been calculated. All these calculations indicate that neither low-energy heaVy ions themselves nor the cascade atoms can directly produce biological effects in cells. Finally some possible reasons for the effects are presented.