Explain what the internal and external exposure of the body is. What is the difference between internal and external exposure?

Explain what the internal and external exposure of the body is. What is the difference between internal and external exposure? What are the routes of entry of radionuclides into the human body. Tell us about the penetration of radioactive substances into the human body through the respiratory system.

Depending on where the source of ionizing radiation is located (in the human body or outside it), internal and external radiation are distinguished.
Internal radiation is produced by radioactive substances that enter the human body with inhaled air, food and water. Radioactive gases inhaled with aerosols enter the respiratory system. From it, they penetrate the blood, lymph, gastrointestinal tract and are carried throughout the body, settling in various organs and tissues: bones, liver, spleen, thyroid gland, etc. The second way the radioactive substances enter the human body is through the digestive tract. From it, these substances are absorbed into the bloodstream and also enter various organs of the person. The entry of radioactive substances into the human body through the skin is possible with open wounds and injuries.
External exposure of the body is made by cosmic rays, natural and artificial emitters located in the air, in the earth, in the walls of the premises, as well as used for industrial, scientific, medical and domestic purposes. An important role is played by the location of the person. The higher it is above sea level, the stronger its radiation, since the thickness and density of the air layer of the atmosphere decreases as it rises, reducing its protective properties. So, people living in an area located at sea level receive a dose of external radiation 6 times lower than living at an altitude of 4000 m per year. At an altitude of 12 km above sea level, the radiation dose due to cosmic rays increases by about 25 times.

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