Since the beginning of time, all living creatures have been, and are still being, exposed to radiation. Nonetheless, most people are not aware of all the natural and man-made sources of radiation in our environment.
A chart of the public's exposure to ionizing radiation (displayed below) shows that people generally receive a total annual dose of about 620 millirem. Of this total, natural sources of radiation account for about 50 percent, while man-made sources account for the remaining 50 percent.
For additional information, see the following topics: