Reported September 2005

BACKGROUND: Airline pilots and flight crews may be exposed to higher radiation levels and therefore greater risk of developing cancer.

WHAT ARE SOLAR FLARES: Deep inside, the sun produces energy by joining atoms of hydrogen, and these nuclear reactions produce the heat and light from the sun. The earth's magnetic field protects us from most of the sun's radiation, and so does our atmosphere. The sun's surface also has magnetic fields, stronger in some places than others, and occasionally the magnetic fields can become twisted. A solar flare is a tremendous explosion on the sun that occurs when energy stored in a "twisted" magnetic field is suddenly released. This produces a burst of radiation across the entire spectrum, from radio waves to X-rays and gamma rays.

HOW RADIATION AFFECTS CELLS: Most of us are aware that the sun's ultraviolet (UV) radiation can damage surface skin cells, even leading to skin cancers, but at high energies it can become ionizing radiation. Ions are electrically charged atoms, a byproduct of a high-energy light ray (X-rays or gamma rays) knocking electrons off of atoms. The resulting free electrons then collide with other atoms to create even more ions. This is dangerous because an ion's electrical charge can lead to unnatural chemical reactions inside cells. It can break DNA chains, causing the cell to either die or develop a mutation and become cancerous, which can then spread. And if the mutation occurs in a sperm or egg, the result can be birth defects, which is why pregnant women should never be subjected to X-rays.

HOW MUCH IS TOO MUCH: Not all of the radiation from a solar flare reaches the earth at the level where we live, but commercial aircraft fly at much higher altitudes where the earth's magnetic field is weaker. So higher levels of radiation may be present. Still, the levels of radiation aren't all that dangerous: on a par with an X-ray or CT scan. This could still be harmful to pregnant women, however, and pilots and flight crew fly so frequently that over time, they receive much larger doses of radiation. Although most studies to date have shown no ill effects from this exposure, the effect can add up over long periods of time.

If you would like more information, please contact:

Vanessa Wasta
Public Information
Johns Hopkins Medical Center
(410) 955-1287

wastava@jhmi.edu