Answer to Question #7221 Submitted to "Ask the Experts"

I have a question about solar radiation storms and airline travel. On 15 July 2000, I flew with my then 12-year-old daughter from Salt Lake City via Las Vegas to Albany, New York. The flight left at 14:00 Mountain daylight time from Salt Lake City and arrived in New York City at 23:00 Eastern daylight time.

I happened to watch a news report the following day that said that the earth was hit on 15 July 2000 with one of the largest solar radiation storms in the last 11 years. I read some of Dr. Robert Barish's books on flight radiation and was concerned about this. I was actually able to speak with Dr. Barish at that time, and he indicated that the peak of the solar flare occurred before our flight and our danger was minimal.

However, I have some further questions on this due to a recent condition that my daughter has developed. She has been diagnosed with secondary hypothyroidism. We were told that the most common cause of this is a tumor of the pituitary gland. Magnetic resonance imaging (MRI) scans have shown no tumor, and she is currently just being watched.

I have looked at the archives of the space weather alerts from the National Oceanic and Atmospheric Administration website during the times of our flight that day and wonder if you could comment on this. I would like to get some idea of our radiation exposure that day and if it put us at any increased risk.

I think we flew mostly during the geomagnetic storm but would appreciate your comments on this. I do remember seeing the aurora borealis light display from the plane as we flew.

Thank you for the public health service that you provide.
 

We as health physicists don't specifically follow solar storms; however, we are concerned with so-called "cosmic rays"—that is, ionizing radiation from space that rains down on us on Earth. On average, this accounts for about 8% of our exposure to natural, background radiation. The rest comes from sources here on Earth. Frequent flyers will receive more cosmic radiation because they're closer to it—the higher the altitude, the more cosmic rays are encountered. This is a real concern for astronauts, who not only fly the highest but also stay up there the longest. There's good information from the National Aeronautics and Space Administration on this.

This and other sites also provide information on health effects from radiation, so I won't repeat that here. Note that any effects of cosmic radiation would be no different than those from other sources of ionizing radiation.

Coming back to ordinary flyers, I've never heard of anyone being overexposed to radiation on a commercial airline flight. Those airplanes don't fly high enough to receive a large dose, even during bursts or storms, and the dose from a transcontinental flight is quite small. Believe it or not, the air above us is an excellent shield against cosmic rays. The aurora borealis you saw shows the upper atmosphere absorbing those rays before they reach us.

Joel I. Cehn, CHP