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Cosmic radiation and cancer
Recently, several epidemiological
studies have been carried out to investigate cancer mortality
and
cancer incidence among airline crew. Many exposure studies
have
been conducted to estimate and to measure the dose of cosmic
radiation at flight altitudes of jet aircraft. The latter
studies conclude
that a typical annual radiation dose is between 3 and 6 mSv
for a commercial pilot. Values up to 9 mSv have been estimated
for a pilot flying some 600 h/year on polar flights at 10
km and
above. Detailed assessment of individual flight history has
showed
that for all pilots the lifetime cumulative exposure was below
100 mSv. Results of the mortality studies and incidence studies
are as yet inconclusive, although for most cohorts the total
cancer
(mortality and incidence) was not raised compared with the
general
population. For specific cancer sites, increased and decreased
standardised mortality or incidence ratios were observed without
a clear pattern. Leukaemia risk is not increased, with the
exception
of a study of Danish pilots, based on only 14 cases. A more
consistent
finding is an increased risk of breast cancer, which is also
a cancer associated with radiation. The role of risk factors
other
than radiation, such as late first childbirth and low parity,
may not
always have been fully taken into account when evaluating
these
findings. Another consistent finding is an increase in skin
cancer
and melanoma. Whether this is related to leisure activities,
occupational
factors or a combination of both needs further investigation.
The overwhelming evidence does not
point to a significant
adverse health effect in terms of cancer, and the present
regulation
of aircrew as radiation workers sufficiently controls the
occupational
exposure. Very few passengers will ever accumulate
radiation doses from cosmic radiation in the same magnitude
as
the staff and hence no particular precautions need to be taken.
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