Terrestrial radiation

Background radiation is the ionizing radiation emitted from a variety of natural and artificial radiation sources: sources in the Earth and from those sources that are incorporated in our food and water, which are incorporated in our body, and in building materials and other products that incorporate those radioactive sources; radiation sources from space (in the form of cosmic rays); and sources in the atmosphere which primarily come from both the radon gas that is released from the earth's surface and subsequently decays to radioactive atoms that become attached to airborne dust and particulates, and the production of radioactive atoms from the bombardment of atoms in the upper atmosphere by high-energy cosmic rays. Today, a small fraction of background radiation also comes from radioactive tools such as smoke detectors and self-luminous dials and signs, and from global radioactive contamination due to historical nuclear weapons testing, nuclear power station or nuclear fuel reprocessing accidents, and from normal operation of the nuclear power industry. Sometimes included in background radiation are routine medical procedures like X-ray imaging; this is purposeful diagnostic exposure which dwarfs all other human-caused background radiation in the population of the industrialized world.