The article provides a general overview discussing niobium and partially zirconium isotopes and their behavior in experimental and natural environments. In terms of weight, zirconium and niobium isotopes account for a quite tangible fraction of radioactive waste streams generated by nuclear industry. As it comes to natural environments, the behavior of substances containing these isotopes has been poorly studied even over the initial period of their one-time intake. Moreover, their chronic long-term intake over hundreds and thousands of years hasn’t been basically studied at all, which raises certain difficulties when demonstrating the long-term safety of radioactive waste disposal. This overview also evaluates the experimental studies focused on niobium behavior in natural environments, as well as some individual hypotheses about its potential behavior. The paper evidences that new experimental studies should be launched to support the forecasts regarding niobium isotope impacts on various types of biota, including human.