This slide demonstrates that we all receive a total of about 370 mrem (0.37 mSv) of radiation exposure each year from background sources. The range of exposures from background is very high in different environments. Background radiation increases as a function of elevation, as a function of radon in homes and from natural radioactive materials in the environments. There are some areas where the natural background radiation dose is increased by more than a factor of ten. Many of the man made exposure are being regulated at levels much below background.