Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Ionizing Radiation Increases Cancer Risk for Frequent Flyers

Dear Doctor: My daughter isn't a flight attendant, but she flies a lot for business. Is she at an increased risk for cancer?

Dear Reader: Commercial airline flying is a relatively new experience. The concept of flying to multiple locations for business would have been inconceivable 100 years ago. The evolution of the human body has not been adapted to flight, so the exposure of humans to prolonged airplane travel is a change that may have health consequences. At higher altitude there is greater exposure to ionizing radiation. Flight attendants and pilots spend much of their working time 30,000 feet above the Earth's surface, so their health may give us an indication of potential hazards with flying.

A recent study in the journal Environmental Health looked at 5,366 former and current flight attendants and compared them with a control group of the same age and health. More than 80 percent of the flight attendants were women. The average age of the participants was 52 and the average duration at the job was 20 years.

The authors looked at the number of cancers in the flight attendants and found a greater rate of cancer overall compared with the control group. In women, there was a 51 percent greater prevalence in breast cancer, a 2.27 times greater risk of melanoma and a 4.09 times greater risk of other types of skin cancer. The elevations of skin cancer were not as great among male flight attendants. There were also increases in the rates of uterine, cervical, gastrointestinal and thyroid cancer among female flight attendants.

The rate of cancer increased with every five-year increment in the air for non-melanoma skin cancers, but this was not noted with other types of cancer. This result is confusing because one would believe there would be greater numbers of cancers based on greater flight time. What is also confounding is that the flight attendant group had fewer children on average than the control group, which should lower the rate of breast cancer in the control group compared to the flight attendants (the greater number of children a woman has incrementally lowers the rate of breast cancer). The authors, though, still found a modest increased rate of breast cancer in flight attendants with the same number of children as the control group. Lastly, the study doesn't take into account the amount of time flight attendants spent on layovers and vacations in the sunshine. This would appear to be greater than the control group and could be a reason for the increased rate of skin cancer.

Nonetheless, ionizing radiation is a risk factor for breast and non-melanoma skin cancers. Cabin crews have the highest annual ionizing radiation dose out of all American workers. While I believe there is a greater risk of cancer among flight attendants, I also feel that confounding factors may make the risk less than what is reported.

But this doesn't really answer the question regarding your daughter. Flight attendants have a substantially greater number of hours in the air than your typical business commuter. Thus, I feel your daughter may not be at a significant risk of cancer from her relatively short time in the air. But I would feel even more comfortable saying this if there were some way to protect both passengers and cabin crews from ionizing radiation.

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