Yes, indeed, you do have one. It’s rather surprising that many people simply don’t realize that radiation exists naturally all around us, and is part of our everyday lives—whether we are aware or not.
So become aware! Click the image below to visit the quick and easy ANS Interactive Radiation Dose Chart
The average radiation does for a person living in the United States is about 6.2 milliSieverts (mSv) per year. About half is from natural background sources, and about half from medical diagnostics and treatments.
For a quick primer on the basics of radiation, see the Radiation page at NuclearConnect. The U.S. Environmental Protection Agency has a highly informative page on Radiation Doses In Perspective. And for more perspective, also recommended is a recent post Get a grip on radiation, people at idigumining.
This chart from xkcd is a very interesting graphical comparison of radiation doses from many sources. Also, this chart (along with a click of the magnification button) from Information Is Beautiful is, well, beautifully portrayed, although do keep in mind it’s logarithmic so it can fit on one page.