Radiation is the process of a random spontaneous release of energy in the form of particles or electromagnetic waves from an unstable atom. Radioactivity is the property possessed by some elements to release energy in the form of particles or electromagnetic waves.
Contamination is a radioactive material in an undesirable location.
There are varying degrees of damage to cells in the body from exposure to radiation, and some cells are more radiosensitive than others. There is also a controversial theory that some low doses of radiation are beneficial or necessary. The use and exposure to nuclear materials causes free radicals. The waste products of nuclear power based on fission are automatically radioactive. Biological material is at a severe disadvantage when put into contact with radiation.