Health Risks of Ionizing Radiation: - Clark University

DNA damage (a chemical change in DNA) than
controls selected from ground crew. Chromosome
aberrations and micronuclei were slightly elevated
but the difference was not significant. On the other
hand, unscheduled DNA synthesis, a measure of
DNA repair, was almost twofold higher in flight
engineers. This evidence of a DNA protection and
repair process was found to be dose-dependent:
oxidative DNA damage was inversely related to
cumulative dose, meaning that damage declined
with increasing exposure, and both DNA repair and
total antioxidant capacity were found to increase
with cumulative exposure (Zwingmann et al 1998).
9.3 Discussion
Pilots and flight crew appear to have higher than
normal rates of prostate cancer, skin cancer, and
acute myeloid leukemia in addition to cellular
evidence of chromosome damage. From the available
information it is hard to speculate about any kind
of radiation dose-response relationship, primarily
because dose information is highly uncertain. In
addition to uncertainty in routine cosmic radiation
Radiation Exposure in Flight 115
exposure, solar flares may contribute substantial
additions to dose in a random way so that cumulative
measures such as hours or years flying are unreliable.
Furthermore, radiation is not the only hazard in
flight. Although it is challenging to deal with the
various potential cancer factors involved with
flying (like chemicals or sleep/wake patterns), it is
plausible that these effects are the result of cosmic
radiation. In some cases the cellular studies help
to clarify the origins of the observed cancers. For
example, Lynge (2001) points out that among seven
aircrew with myelodysplasia 5 or AML that were
analyzed for chromosome changes, four had changes
that tend to be associated with radiation exposure
(deletion or loss of chromosome 7). In her study of
Concorde pilots, Heimers (2000) found an increase
in micronucleated cells, which are a common effect
of radiation, but did not find an increase in sister
chromatid exchanges, an effect typically associated
with chemical exposures. This suggests that the
radiation exposures experienced by flight personnel
might be more important than exposures to chemicals
when considering the observed cancer outcomes.
5 Myelodysplasia is a condition in which the bone marrow does not produce sufficient quantities of normal blood
cells; it can be an early stage of acute leukemia.