Flying may be hazardous to your health and not just from
plane crashes. Another less well publicized danger is the
increased risk of cancer caused by the extra solar radiation
you receive when you fly.
The sun constantly emits ionizing radiation known as
solar wind. During storms it releases solar
flares, also called coronal mass ejections, during which
billions of tons of protons burst outward at nearly the speed
of light. When these protons reach the earth they are directed
toward the poles by our planet's magnetic field. At the
altitudes at which airliners fly, the number of protons over
the pole is about twice as high as the number over the
equator. The earth receives more of this radiation every
eleven years when the sun is at the maximum of its storm
season, which correlates with the peak of the sunspot cycle.
During mid-2001 the sun has been at or near the peak of its
storm activity.
Solar radiation causes cancer in the same way as radiation
from a radioactive material. The sun's protons hit the
person's flesh so hard that an electron can be knocked off an
atom in the tissue. This process disrupts cells, which can
cause cancer. The sun's protons can also hit an atom in the
air or in the airplane's body knocking loose a neutron that
can also hit tissue and damage cells causing cancer. Neutron
radiation is rare on earth but is found in the cores of
nuclear reactors and near nuclear explosions.
Life on earth is protected from solar radiation by our
atmosphere. But the atmosphere is thickest at sea level and
decreases by half with each 6500 feet of altitude. Airplanes
typically fly above 30,000 feet where the atmosphere is only
about 3% as protective as at sea level. A passenger on a
single flight receives a very low dose of radiation, which
represents very little increased risk in getting cancer.
However, growing cells are more susceptible to radiation
damage than normal cells so a pregnant woman flying a polar
route during a solar storm may receive enough radiation to
exceed government health guidelines. Pregnant flight
attendants, especially those flying numerous polar routes,
could be endangering their fetuses. Flight crews who fly polar
routes for years may be exposed to more radiation than workers
in nuclear power plants. Unlike the nuclear plant workers,
they are not monitored.
There is no evidence so far that this exposure is
dangerous. Flight crews have higher rates of many diseases
than those who are earthbound but no one knows if these are
related to radiation or other job risks such as years of
disruption of biorhythms from time-zone changes. The skin
cancer melanoma is higher among pilots, which could be caused
by excess radiation, or by the ability of pilots to lounge on
sunny beaches.
Still the Association of Flight Attendants recommends
having radiation monitors on flights so that airplanes could
change altitude or route during solar storms. And a few
airlines do routinely alter routes to avoid solar storms.
European governments classify their flight crews as radiation
workers, educating them about radiation risks and tracking
their exposure. Some people discount the dangers from solar
radiation and suggest that the solar flares' disruption of
radio communication is a bigger threat to passengers as is
their risk from germs carried by other passengers.
Reference
The Frequent Flyer and Radiation Risk, Matthew L. Wald, New
York Times, June 12, 2001.
Credits
Dana
Desonie
