Ionizing radiation comprising: α-rays (α particles), β-rays (β particles), neutron flux of energetic particles and γ-rays, X-rays and other high-energy electromagnetic waves, and is known as cosmic rays are high energy particle beam both. Electromagnetic waves (photons) of the ionization capacity changes with the electromagnetic spectrum, the electromagnetic spectrum γ rays, X-rays ionize almost any atom or molecule. The higher the frequency of the electromagnetic wave energy stronger and stronger ionization capabilities. On the electromagnetic spectrum, far ultraviolet light, ionizing strong ability; 

Direct ionizing radiation: with sufficient kinetic energy to cause ionization of direct ionizing radiation consists of charged particles, such as collision. 

Indirectly ionizing radiation: with sufficient kinetic energy can be generated when the collision of charged particles so that the medium is ionized and so does not directly charged particles ionizing radiation occurs medium composition. 

Non-ionizing radiation and X-ray contrast is the longer wavelength electromagnetic waves, because of its low energy, can not cause ionization of matter, it is called non-ionizing radiation. As the near UV and visible light, infrared, microwaves and radio waves are weak ionizing electromagnetic waves. 

The dangers of ionizing radiation on the human body is great, because the general ionizing radiation is invisible, but extremely tiny radioactive dust is not so noticeable, so the victim may be unknowingly overexposure or inhalation of micro-radiation dust. In a short period of excessive radiation exposure or inhalation of dust can cause acute radiation sickness, there may be nausea, vomiting, abdominal pain and hair loss and other symptoms, its hematopoietic function, digestive and nervous systems may also be abnormal; while long-term excessive accumulation of radioactive elements in the body, can cause chronic radiation sickness. Excess ionizing radiation is carcinogenic and teratogenic effects. 

External radiation: ionizing radiation, radiation source outside the body of an effect on the human body. 

Irradiation: radioactive elements into the body, an effect directly on the human body.