Sunlight is a natural radiation. Proper sunlight is beneficial to the human body and helps the human body to synthesize many necessary nutrients, but excessive enjoyment of sunlight can also cause damage. In addition, human beings are exposed to all kinds of other natural rays all the time, including the sun, cosmic rays and radiation produced by earth radionuclides. For example, granite used as decorative materials has radiation, and food, houses, the sky, the earth, mountains and rivers, plants and even human bodies have radiation. These natural rays are natural background radiation. Natural background radiation is harmless to human beings.

People will also be exposed to artificial ionizing radiation in daily life, such as chest X-ray examination and CT. Radioactive substances are also widely used in people's daily consumption, such as luminous watches, glazed ceramics, artificial dentures, smoke detectors and so on.

In long-term practice and application, it is found that a small amount of radiation exposure will not harm human health, while excessive radiation exposure will cause harm to human body, making people sick or even die. The influence of radiation on human health is related to many factors such as dose, time and mode of radiation.

The radiation dose in some high background areas in China is 3.7 mSv/ year, that in water, grain, vegetables and air is 0.25 mSv/ year, that in soil is 0.10.5 msv/year, and that to and from Beijing and Europe by air is 0.04 mSv. The annual maximum radiation dose to residents around 80km of the nuclear power plant is 0.0 1 mSv/ person/year, which is much lower than the natural background radiation. (Compared with the radiation dose value on the graph)

Source: official website, Kangningda, Hunan.