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Cosmic Radiation During Flights
Earth and its inhabitants are constantly showered by radiation from space, like a steady drizzle of rain. This
shower of cosmic radiation is created by charged, "sub-atomic particles" (parts of atoms) that originate in our
galaxy, other galaxies, and the sun. The particles interact with Earth's atmosphere and magnetic field to create
cosmic radiation.
The charged particles exhibit a wide range of energies and the rate at which cosmic rays bombard Earth
depends on whether they are low- or high-energy. The vast majority of cosmic rays are low-energy. Although,
high-energy cosmic particles constantly pass through and sometimes interact with our body, they are very rare
and very difficult to detect.
About eight percent of our annual radiation exposure comes from outer space. The atmosphere shields us from
cosmic radiation, and the more air that is between us and outer space, the more shielding we have. The closer
we get to outer space, the more we are exposed to cosmic radiation. This holds true when we live at high
altitudes or fly.
Our exposure to cosmic radiation partially depends on the elevation of where we live. For example, people
who live in Denver, Colorado, which is more than 5,000 feet above sea level, are exposed to more cosmic
radiation than people living in Chicago, Illinois, which is only about 700 feet above sea level. For the same
reasons described above, we are exposed to higher levels of cosmic radiation when we fly on a commercial
airplane.
The amount of cosmic radiation you are exposed to while flying depends on your altitude and latitude
(distance from the Earth's equator) and solar activity. For atypical cross-country flight in a commercial
airplane, you are likely to receive 2 to 5 millirem (mrem) of radiation, less than half the radiation dose you
receive from a chest x-ray. People in the United States receive an average of 360 mrem of radiation per year
from natural and man-made radiation sources, which includes cosmic radiation exposure during commercial
flights.
Who is protecting you
Federal Aviation Administration (FAA)
Solar events, like sun spots, can produce elevated radiation levels at high altitudes and/or latitudes. To prevent
increased exposure to cosmic radiation, routine forecasts and alerts are sent through the FAA so that a flight
traveling during a solar event can alter its flight plan by reducing altitude. The FAA has developed a computer
software program for public use, entitled CARI-6, which provides an estimated equivalent radiation dose for
flights.
United States Environmental Protection Agency
Office of Radiation and Indoor Air (6608J) | EPA 402-F-06-021
April 2006
www.epa.gov/radtown/cosmic.html
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RadTown USA
What can you do to protect yourself
There are no practical ways to shield yourself from cosmic radiation during a flight you can reduce your
exposure while flying by taking shorter flights at lower altitudes. This is often not practical and the risks from
cosmic radiation do not warrant changing your travel plans to reduce your exposure.
Resources
You can explore this radiation source further through the resources at the following URL:
http://www.epa.gov/radtown/cosmic.htmltfresources
We provide these resources on-line rather than here so we can keep the links up-to-date.
United States Environmental Protection Agency
Office of Radiation and Indoor Air (6608J) | EPA 402-F-06-021
April 2006
www.epa.gov/radtown/cosmic.html
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