External Radiation Exposure to the Population of the Continental U.S. from Nevada Weapons Tests and Estimates of Deposition Density of Radionuclides That Could Significantly Contribute to Internal Radiation Exposure via Ingestion

This report provides estimates of the external radiation exposure and whole-body effective dose received by residents of the continental U.S. during the period 1951-1962 from weapons tests carried out at the Nevada Test Site (NTS). Estimates are given on a countyby-county basis for each test and for each year of testing. The average committed population dose from all NTS tests was about 0.5 mSv, about equivalent to 1-2 years of external radiation exposure from natural background. Residents of the counties immediately downwind from the NTS incurred much higher doses, in excess of 3 mSv, while the residents of the Far West, Pacific Northwest and Southeast received lower than average exposures. The tests and radionuclides that contributed the most exposure are discussed, as well as the dependence on fallout time of arrival. The most exposed individuals were outdoor workers; the least exposed were persons who spent most of their time indoors in heavily constructed buildings. The deposition of radionuclides that contribute to internal radiation exposure via the ingestion pathway was also calculated on a county-by-county and test-by-test basis. The general pattern of deposition, tests contributing the most to the deposition, deposition density versus distance from the NTS, and the differences in deposition between radionuclides are discussed. In general the deposition of long-lived radionuclides such as Sr-90 and Cs-137 was about a factor of 20 less than that from “global fallout” from highyield weapons tests carried out in the Pacific and Soviet Union. However, the deposition of short-lived isotopes such as I-131 was greater than from “global fallout.”