Although most of the harmful radionuclides are of anthropogenic origin and released from military or industrial processes, radioactive substances, such as uranium, also occur naturally in the environment. Low standards of care at nuclear facilities can lead to the contamination of employees with radionuclides due to inhalation of gases or dust or contamination of skin or wounds. Various sources for radionuclide exposure may present concerns for radioactive polonium or plutonium exposure, for instance, terrorist actions on the infrastructure, such as on drinking water basins. Early health effects after extensive radiation exposure may be vomiting, headaches, and fatigue, followed by bone marrow depression, fever, and diarrhea. The main purpose of radionuclide mobilization is to minimize the radiation dose. Since some of the important radionuclides, such as polonium and plutonium, have very long biological half-times after their deposition in bone, liver or kidneys, rapid initiation of chelation treatment is usually imperative after a contamination event. The antidote DMPS (dimercapto-propanesulfonate) is considered the drug of choice for polonium decorporation. DTPA (diethylenetriamine pentaacetate) is a potent chelator especially approved for radionuclide mobilization, including polonium and other actinides. Other chelators and drugs are under investigation as potential chelators of transuranic elements.