Radiation can be found naturally or can be created by human-made artificial sources. Radioactive unstable elements divide to become stable, they release the excess energy in their nuclei to their surroundings by producing different types of radiation. This uranium, radium, thorium, potassium, etc. on earth. Cosmic rays coming from the sun and outer space, together with unstable elements, create a certain level of natural radiation in the environment. Therefore, natural radiation comes from many naturally occurring radioactive substances found in the soil, water, air and body in the environment where we spend our daily lives.The intake of natural radioisotopes into the body through digestion varies depending on the consumption rate of food and beverages and the radioisotope concentration. The concentration of radioisotopes naturally found in foods varies depending on the natural background levels, climate and agricultural practices of the region. Likewise, eating habits vary from region to region and country to country.All foods contain radionuclides, which are transferred from soil to crops on land and from water to fish in seas, lakes and rivers. Natural radionuclides in drinking water and food generally have very low levels and are safe for human consumption. In normal situations, a reference level of 1 mSv in a year applies to the individual radiation dose from the consumption of food. The same reference level applies separately to drinking water. These references are determined by the WHO/FAO Codex Alimentarius Commission has established “Guideline Levels” for radionuclides in foods destined for human consumption and traded internationally.