The average person in the United States receives about 360 mrem every year whole body equivalent dose from background sources. This is mostly from natural sources of radiation, such as radon, but does includes natural and human produced sources
On average, Americans receive a radiation dose of about 0.62 rem or 620 millirem)each year. Half of this dose comes from natural background radiation. Most of this background exposure comes to the air, with smaller amounts from cosmic rays and some from even the earth itself.