Human exposure to radioactive material destroys the body on a molecular level. When radiation collides with living cells, they become ionized. Since cells are mostly water (H20), radiation ionizes this molecule to form H+ and OH-. These are free radicals and are highly reactive in the body. Alternatively, the radiation can collide into DNA strands directly and damages it. Overall, critical cellular bonds and structures are disturbed which damages proteins and DNA in cells. To an extent, the human body can repair this damage on its own to an extent using antioxidants.