Frequently Asked Questions
|8 |How many atomic-bomb survivors
are included in the group being studied by RERF and how were they
chosen for this study?
|8 | To establish a population framework in which to conduct
long-term follow-up of mortality and cancer incidence,
about 94,000 people were selected from 280,000
A-bomb survivors who were resident in Hiroshima or
Nagasaki at the time of the October 1950 Japanese
national census. Of these, about 54,000 were exposed to
radiation doses (Question 11) within about 2,500 meters from
the hypocenters. Another 40,000 members of the study
population were exposed beyond 2,500 meters and
received very low doses.
In the 1950 Japanese national census, approximately
280,000 people indicated that they had been exposed to the
atomic bombs. RERF’s study population probably
includes about 50% of those proximally exposed (within
about 2,500 meters of the hypocenters) and 25% of those
distally exposed (greater than 2,500 meters from the hypocenters).
These percentages are not precise because the
census did not record the location of exposure in reference
to the hypocenters.
An additional 27,000 who were
not in Hiroshima or Nagasaki at the time of the bombs, but
whose family registries were in Hiroshima or Nagasaki
and who lived in either city at the time of the 1950 census
also were included as an unexposed comparison group.
These groups constitute the 120,000-member Life Span
Study (LSS) cohort.
In addition to studying the LSS cohort, RERF scientists are involved in
studies of several other populations: the Adult Health Study (AHS), in utero-exposed, and F1 cohorts. The AHS population comprises 23,000 members of the LSS, who, since 1958,
have been asked to participate in biennial medical examinations carried
out at RERF. The in utero-exposed
cohort is a group of about 3,600 people who were exposed
to the bomb while in the womb. The F1 population consists of about 77,000 people born in Hiroshima or Nagasaki
between 1 May 1946 and the end of 1984 to parents with and without exposure
to the bombs.