Ubiquitous background radiation in the United States: comparing NCRP estimates to readings taken at selected locations in the continental United States using gamma spectrometry

Every organism on Earth is exposed to ionizing radiation. Food, water, air, rocks, soil, medical procedures, building materials and, of course, ubiquitous background cosmic radiation contribute in varying levels and types of radiation to our total radiation exposure. In 1987 and 2006, the National Council on Radiation Protection, (NCRP) undertook the task of attempting to estimate the total annual background radiation to which humans in the United States are exposed. My research sought to verify the NCRP estimates using a series of coordinated measurements of gamma radiation from sea level to over 14,000 feet altitude taken at multiple locations in the Continental United States. With one exception on Pikes Peak, the actual data recorded were found to be lower than the data points predicted by the NCRP. This was the case even though the gamma spectrometer employed was demonstrated to be 124X more sensitive than existing devices. The observed variances from predicted levels ranged from a maximum of 2.1 millisievert to a minimum of 0.4 millisievert.