6.1
EARLY RADIATION SURVEYS.
In the months immediately following the detonations, U.S. scientists
conducted a number of onsite surveys to be sure that any residual radiation in
Hiroshima and Nagasaki would not present a health hazard to occupation troops
or to the Japanese remaining in the cities.
General Marshall, U.S. Army Chief
of Staff in Washington, addressed the first concern in a message sent to
General MacArthur, the Theater Commander.
General Marshall emphasized the
importance of early radiation surveys so that the occupation troops "shall not
be subjected to any possible toxic effects, although we have no reason to
believe that any such effects actually exist."
Three series of early
radiation surveys followed:
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Scientists from the Manhattan Engineer District, the organization that
had developed the bombs, made rapid radiation surveys of Hiroshima on
8-9 September 1945 (1 month before occupation troops arrived in that
area) and of Nagasaki on 13-14 September (10 days before the
occupation troops arrived).
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The Manhattan Project Atomic Bomb Investigating Group made more
extensive surveys in Nagasaki from 20 September to 6 October and in
Hiroshima from 3 to 7 October 1945.
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They reported negligible levels of radioactivity in the areas
surveyed.
Their measurements, detailed in extensive reports, showed the
levels of residual radioactivity to be extremely low.
The Naval Technical Mission to Japan surveyed Nagasaki during 15 to
27 October and Hiroshima on 1 to 2 November 1945.
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Their well-documented findings of negligible levels of
radioactivity corroborated the earlier measurements.
In addition to these surveys, the U.S. investigation teams used data from
numerous separate radiation monitoring surveys, soil and debris sampling
programs, and other analyses conducted by Japanese scientists in the days and
weeks immediately following the bombings.
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