ABSTRACT
During the Summer or 1957 ion chamber measurements
were made of the external environmental radiation in
locations throughout the United States.
The purpose
of these measurements was to establish the approximate
range of population exposures to the penetrating radi-
ation component, cosmic radiation and terrestrial gamma
radiation, but excluding terrestrial beta radiation.
The natural levels encountered ranged from a low
of 8.4 microroentgens/hour along the Pennsylvania Turnpike to a high of 38.6 microroentgens/hour at the
summit of Pikes Peak. Among the major United States
cities visited, Denver, Colorado exhibited the highest
radiation levels with a range of 16.6 to 22.4 micro-
roentgens/hour.
Elevated levels associated with fall-
out from nuclear weapons tests, were encountered in
eastern Arkansas and the Black Hills of South Dakota.
The results of this survey are compared with the
estimates of other investigators; including, the
measurements of Hess, Neher, Compton, and the calculations of Burch and Libby.