Radioactive pollution can come from natural sources like cosmic rays and radioactive elements in the Earth's crust, or from human sources such as nuclear weapons testing, nuclear power plants, medical use of radioisotopes, and improper disposal of radioactive waste. Exposure to radiation can cause both immediate effects like hair loss and long term effects like cancer. All living things are vulnerable but some organisms preferentially accumulate specific radioactive materials. Control of radioactive pollution requires safe containment and storage of wastes, along with preventative measures to limit radiation exposure.