Due to the radioactivity of the element, the maximum allowed concentrations are measured in radioactive activity (Ci - 1 Curie), which represents the number of decays per time unit. The maximum permissible concentration of Tc-99 in water is 0,01 microCi/cc and in the air is 2x10-6 microCi/cc. In the human body, the maximum permissible burden is 10 microCi in the kidney, 20 microCi in the liver, 400 microCi in the skin, 500 microCi in the bone and 2000 microCi in the lungs. Even though Tc-99 has a long half-life and emits only weak 0,29 MeV beta radiaction, it is still considerable contamination hazard, and should be handled in a glove box.