Nuclear radiation, or often called radioactive substances being present in all of this is the existence of hundreds of millions of years, the objective fact is a normal phenomenon. Nuclear radiation is the transition from one energy state structure or a structure to another state or another kind of energy released in the process of microscopic particles stream. Nuclear radiation can cause ionization or excitation substance, it is called ionizing radiation. Ionizing radiation is divided into direct and indirect ionizing radiation ionizing radiation. Direct ionizing radiation, including protons and other charged particles. Indirectly ionizing radiation, including photons, neutrons and other uncharged particles. 

Nuclear radiation is mainly α, β, γ three kinds of rays: 

α-rays are helium nuclei, as long as a piece of paper can be blocked, but inhaled great harm; 

β rays are electrons flow, skin burns after irradiation significantly. Because of these two rays penetrating the small, relatively close distance as long as the effects of radiation do not enter the body, the impact is not too great; 

Penetration γ rays are strong, a very short wavelength of electromagnetic waves. Similar γ radiation and X-rays can penetrate the body and buildings, hazard distance. The universe, the nature of radioactive substances can produce a lot of harm, but not too much, only a nuclear explosion or radioactive material leaking nuclear power plant accident to a wide range of ground personnel casualties. It is common electromagnetic radiation on the human body primarily by the power (the field strength) and the frequency is determined. Radio waves using a low-frequency electromagnetic waves, according to the frequency from low to high (from long to short wavelength) in order of precedence, electromagnetic waves can be divided into: long wave, medium wave, shortwave, FM, microwave, infrared, infrared , visible light, ultraviolet, X-rays, γ-rays, cosmic rays. Visible light for the sector, frequencies below (longer wavelength) electromagnetic waves visible to the human body is mainly thermal effects, a higher frequency than visible light rays on the human body mainly produce chemical effects.