A 1991 study by the National Cancer Institute, "Cancer in Populations Living Near Nuclear Facilities," concluded no increased risk of death from cancer for people living in counties adjacent to U.S. nuclear facilities. Nuclear power plant operations contribute less than one one-hundredth of one-percent of the average American's total radiation exposure. This contribution is dwarfed by differences in background radiation. The background radiation exposure for someone living on the Colorado Plateau, for example, is about twice that of someone living in the Midwest.
Everyone is continually exposed to radiation. Very little of the exposure comes from any manmade source, unless we are using nuclear medicine, such as radiation therapy for cancer, or for diagnostic procedures. Natural sources - principally radon created as a result of ongoing radioactive decay of materials that are common in the earth’s crust, and gamma rays from space - are far more significant sources of radiation exposure. Our bodies have, and continuously take in, traces of naturally occurring radioactive materials, mostly from naturally occurring radioactive nuclides present in the food we eat and in the air we breathe. For example, potassium 40, a mineral that transmits electrical signals within bodies, comes from bananas and brazil nuts. That potassium contributes to about 4,000 - 5000 radioactive decays of individual nuclei every second in a person’s body (assumes 175 lb. person).