All humans are constantly exposed to natural and artificial sources of radiation in daily life. Different sources and pathways of radiation exposure (natural as well as man-made) are depicted in various forms and levels. This radiation can impact the human living environment and cause biological effects. These biological effects depend upon different parameters, such as dose, age, and body location. These radiations can be divided into two types: natural and man-made sources. Natural sources include terrestrial radiation, which comes from the soil, rocks, air, tap water, natural gases, etc., and cosmic radiation, which comes from the cosmos. Man-made sources arise from medical and dental X-rays, nuclear medicine, etc. The level of radiation emitted by natural sources is particularly important due to two major radiological effects: (1) external irradiation of the body and (2) internal irradiation of the lung. Because natural radiation is the largest contributor of external radiation to the world population, assessing gamma radiation doses from natural sources and the accompanying health impacts on humans is crucial.