Radiation can ionize matter caused by the high energy which displaces electrons during interactions with atoms. In the electromagnetic spectrum higher frequency ultraviolet radiation begins to have enough energy to ionize matter.
Examples of ionizing radiation include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions by direct or secondary processes in passage through tissues.
Damage of living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionized cells have to repair themselves to remain alive. Generally, healthy cells have a higher capability to repair themselves than cancer cells.

Biological effects of ionizing radiation exposure:
Ionizing radiation are used in a wide range of facilities, including health care, research institutions, nuclear reactors and their support facilities, and other manufacturing settings. These radiation sources can pose a serious hazard to affected people and environment if not properly controlled.

See also Radiation Safety, Controlled Area, Radiotoxicity and As Low As Reasonably Achievable.

Radiotoxicity refers to radioactive materials that are toxic to living cells or tissues. Radiotoxicity results from the type of radiation, the radioactive half-life of the used radionuclide, the biological half-life in the tissue and the radioactivity absorbed in the organ. Radiotoxic substances can be collected following ingestion, inhalation and absorption.

[Also: Half-Life Time, Radioactive Half-Life] The half-life is the time in which half the atoms (always a fraction, not a number) of a given radionuclide disintegrate from the amount of atoms present when measurement starts. From 200 atoms of a radionuclide with a half-life of one minute will 100 atoms disintegrate in the first minute, 50 in the second minute, etc. The half-life is a characteristic property of radioactive isotopes. The effective half-life includes all processes of elimination, including radioactive decay.
Different half-life terms:
- Physical Radioactive Half-Life
- Biological Radioactive Half-Life
- Effective Radioactive Half-Life.

See also Decay Constant, Decay.

A controlled area is the area outside of a restricted area but within the area whose access is limited by licensed operators. The access, occupancy, and working conditions are controlled for radiation protection purposes.
A controlled area includes the location of a radioactive waste disposal facility, identified by institutional control that is intended to be used for monitoring and surveillance of a disposal facility and to act against or restrict public access, and the subsurface underlying a surface location.

Decontamination is a process to reduce or remove unwanted material, such as radioactive, toxic chemical or biological substances. Decontamination from the surface of an object or from an area applies to removal by washing, biological agents, chemical action, mechanical cleaning, or other techniques.

(ARS) The acute radiation syndrome is a form of radiation sickness. An acute radiation syndrome can be developed after the exposition to a high radiation dose received in a short period of time (e.g., x-rays or gamma rays). ARS subsyndromes include hematopoietic, cutaneous, gastrointestinal, and neurovascular diseases. The reaction will vary with dose and factors like age, medical co-morbitdity and immunosuppression.