Radiation from air travel
Cosmic radiation consists of energetic charged particles, such as protons and Helium ions, moving through space. They originate from events beyond our solar system and from the sun. By the time cosmic radiation reaches the ground its intensity has been considerably reduced.
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The only effect that is known to be possible at this level of exposure is a very slight increase in the chance of a cancer occurring many years, even decades after the exposure.
Health risks for unborn child
Birth defects are not expected to result from cosmic radiation at commercial aircraft altitudes because much higher levels of radiation exposure are needed to produce birth defects.
Pregnant women who expect to fly more than 200 hours over the course of their pregnancy should seek further information from the Radiation Protection Bureau, Health Canada on the radiation risks for unborn children.
It is uncertain whether this level of exposure is sufficient to cause any harm to an unborn child. It is possible that this level of exposure may result in a slight increase in the chance of a cancer, such as leukemia, occurring in childhood, or later.
Because of the uncertainty concerning the magnitude of the risk at low levels of exposure, radiation protection authorities have recommended that the additional exposure to an unborn child be kept to a level which is similar to the variation in natural background radiation. This would equate to about 200 hours of flying. At this level of exposure no observable health effects are expected.
The amount of exposure to cosmic radiation while flying depends on the time spent flying, in addition to the factors mentioned above - altitude, latitude and solar activity. Solar flares contribute very little to the overall exposure from cosmic radiation.
For occasional flyers the exposure to cosmic radiation is very small. For those who fly frequently, such as aircrew and some business travelers, the annual exposure may be comparable with, or even exceed, that of radiation workers in ground-based industries.
At commercial aircraft altitudes cosmic radiation is much more intense than on the ground. Even though exposure can be a hundred times greater at these altitudes than it is on the ground, it is still fairly small. It would take about 100 one-way flights between Toronto and Vancouver to obtain the same exposure as we get in one year from other sources of natural background radiation.
About cosmic radiation
The Earth's atmosphere provides considerable protection from cosmic radiation. At commercial aircraft altitudes the protective layer of the Earth's atmosphere is much thinner than it is on the ground and the intensity of cosmic radiation is approximately 100 times greater at these altitudes than it is on the ground.
On the ground, cosmic radiation makes up on average about 17% of the natural background radiation to which we are all exposed.
The amount, or intensity, of cosmic radiation depends on altitude and latitude, as well as the stage of the solar cycle. The Earth's magnetic field can deflect some of the cosmic radiation away from the Earth. The shielding ability of the magnetic field is most effective over the equator and least effective over the poles. The intensity of cosmic radiation at aircraft altitudes around the equator is about three times less than at the poles.
The Sun ejects energetic particles, such as protons (solar flares), which may also contribute to the intensity of cosmic radiation. However, only on very infrequent occasions would solar flares have sufficient energy to increase the intensity of cosmic radiation at commercial aircraft altitudes.
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