To put various radiation exposures in perspective (not entirely certain of the validity of the link, it doesn't cite sources): http://www.physics.isu.edu/radin

To put various radiation exposures in perspective (not entirely certain of the validity of the link, it doesn't cite sources): http://www.physics.isu.edu/radinf/dental.htm http://www.physics.isu.edu/radinf/dental.htm >A typical dental x-ray image exposes you to only about 2 or 3 mrem. The National Council on Radiation Protection (NCRP) says that the average resident of the U.S. receives about 360 mrem every year from background sources. This comes from outer space, radioactive materials in the earth, and small amounts of radioactive material in most foods we consume. >Some typical sources that may expose you to radiation also include smoke detectors (less than 1 mrem per year), living in a brick house instead of a wood one (about 10 mrem per year due to radioactive materials in the masonry), cooking with natural gas (about 10 mrem per year from radon gas in the natural gas supply), reading a book for 3 hours per day (about 1 mrem per year due to small amounts of radioactive materials in the wood used to make the paper), and even from flying in an airplane (about 5 mrem for one cross-country flight because of the increased altitude.)