Levels of Exposure


The previous graph (0-5 mR) has been compressed by a factor of 10 and is illustrated as the lower portion of the above bar.

The dose received from a single chest x-ray ranges from 12 to 17 mR. This is a useful number to remember when making comparisons to other radiation exposures.

The president of the United States receives approximately 20 mR per year due to the large amount of granite in the structure of the capitol building. Granite contains many naturally occurring radioactive isotopes. Wood and bricks also contain natural radioisotopes. As a result, we each receive some exposure from the components of our dwellings.

Each of us receives approximately 25 mR per year as a result of cosmic rays and terrestrial sources. The cosmic rays originate primarily from the sun, while the terrestrial sources originate primarily from the natural isotopes that occur on our planet.