Health Risks of Ionizing Radiation: - Clark University

of the bombing), orientation (facing away from or
towards the hypocenter) and the age of the person
at the time of the bombing. The DS86 system will
soon be replaced by a new system (DS02) that
will incorporate moderate changes in neutron dose
estimates, changes in methods for gamma radiation
dose computation and better adjustments for external
shielding by factory buildings and local terrain
features (Kellerer and Rühm 2002).
Some may wonder why the atomic bomb studies,
which are usually considered to be high-dose studies,
would be included in a low-dose overview. Although
it is true that many people received high doses of
radiation from the detonation of the bombs, 75% of
the exposed survivors had doses between 0.005 and
0.2 Sv (Pierce and Preston 2000). At the same time
the cohort is also representative of a wide range of
doses, from less than 1 mSv to several Sv, making it
useful for dose-response analysis.
Uncertainties. As with all scientific endeavors,
studies of the atomic bomb survivors are associated
with various complexities and uncertainties that can
impact our interpretations of the data. Stewart and
Kneale (1993) and Stewart (1997) have challenged
the sampling accuracy of the LSS on the grounds that
the initial exposures may have caused an unequal
distribution of deaths among those who had strong
and weak immune defenses. If this is true then the
surviving population is unusually strong and risk
estimates based on the cohort may underestimate
risks in the general population. Stewart and Kneale
found evidence of this ‘healthy survivor’ phenomena
in the data; there is a significant deficit of those who
were 50 years old and those who were