Which item is NOT a main natural source of radiation exposure?

Which item is NOT a main natural source of radiation exposure?

• A. Radon, Cosmic radiation, radioactive elements in earth's crust, radioactive elements present in the human body
• B. Gamma rays from the Sun
• C. Medical X-ray exposure
• D. Solar ultraviolet radiation

Answer: (C)

Exposure to radiation in the environment mainly comes from natural sources that exist without human activity: radon gas seeping from the earth into buildings, cosmic rays originating in space, and naturally occurring radioactive materials in the earth’s crust and even in the human body. Solar radiation includes various forms; while ultraviolet light is non-ionizing, the Sun also emits natural radiation that contributes to exposure, and gamma rays from space are part of natural ionizing radiation as well. Medical X-ray exposure, by contrast, is produced by human-made imaging equipment and medical procedures, not by natural background sources. That makes it the item that is not a main natural source of radiation exposure.

Exposure to radiation in the environment mainly comes from natural sources that exist without human activity: radon gas seeping from the earth into buildings, cosmic rays originating in space, and naturally occurring radioactive materials in the earth’s crust and even in the human body. Solar radiation includes various forms; while ultraviolet light is non-ionizing, the Sun also emits natural radiation that contributes to exposure, and gamma rays from space are part of natural ionizing radiation as well. Medical X-ray exposure, by contrast, is produced by human-made imaging equipment and medical procedures, not by natural background sources. That makes it the item that is not a main natural source of radiation exposure.