Radiation Exposure Seen as Posing Risk For Airplane Crews
By MATTHEW L. WALD
Published: February 14, 1990
Pilots and flight attendants on many airline routes are exposed to more radiation than most workers in nuclear power plants, new Government studies show. In power plants the Government imposes extensive safety requirements, including education, monitoring and procedures to minimize dose, but no such limits are applied for the flight crews.
Concern over radiation from the sun and the stars for both flight crews and passengers was stated more bluntly than ever in a report made public Monday by the Department of Transportation.
For airline personnel, the report likens the level of risk to that from working in cabins filled with cigarette smoke. The report also noted a higher risk to ''very frequent fliers'' on long trips and to women in early pregnancy.
Although scientists emphasize that the effects of low doses of radiation are uncertain and nearly impossible to measure in the population, several conclusions are clear from the report, as well as from the draft of a warning published late last year by the Federal Aviation Administration and from research by experts outside the Government.
Aviation officials have rejected requiring protective measures but may do so now. The new studies seem likely to spur further action, though airline employee unions are split on the importance of the issue.
The radiation doses received by the flight crews vary with the altitude and latitude: the higher the plane is flying and the closer to the poles, the higher the radiation doses. Experts say no shielding would stop the very-high-energy radiation to which air travelers are exposed, but monitoring devices in the cockpit could warn when it would be helpful to fly at a lower altitude to evade the radiation.
These devices would be useful because the sun's output of radiation varies widely, and a few times each decade the levels rise high enough to be of concern to women who fly just once during pregnancy.
But even for pilots and flight attendants, scientists say, the additional risk of cancer carried by the radiation exposures in flight is modest as against the overall cancer rate.
For instance, the Transportation Department study predicted that among 100,000 crew members who spent 20 years flying 960 hours a year on an east-west domestic route of more than three hours, 59 to 61 ''premature cancer deaths'' would occur. Among 100,000 passengers flying 480 hours a year on the same route, or about 9 hours a week, 29 or 30 additional cases of cancer would occur. The rate of cancer from all causes would be about 22,000 in that group. Pregnant Women Told To Avoid Some Trips Moreover, Dr. Michael E. Ginevan of Geomet Technologies Inc., of Germantown, Md., who made those calculations, said that since the report was completed in December, new findings based on cancer rates among survivors of Hiroshima and Nagasaki had tripled or quadrupled the expected incidence of cancer from low-level doses.
''If I were a woman in the critical period of pregnancy for retardation, I would tend to avoid flights to Europe,'' Dr. Ginevan said. Scientists say the most critical period is from the eighth week of pregnancy to the 15th week.
Dr. Andrew Horne of the F.A.A.'s Office of Aviation Medicine said in a telephone interview: ''We think it would be appropriate to educate people, particularly pregnant crew members who may be flying. It might be appropriate for some to consider alternate routes or leaves of absence.''
Although there is a mechanism the F.A.A. could use to warn the pilots to fly lower, during peak periods of solar activity, it has never been put in action. Exposure Can Be Higher Than at Nuclear Plants On some routes, the annual radiation doses for crews are higher than the averages for workers in a nuclear power plant, medical office or industrial setting where X-rays or radiation sources are used, the experts say.
Dr. Robert J. Barish of the division of radiation oncology at New York University Medical Center says radiation levels in a jetliner are occasionally so high that in a nuclear plant they would require signs warning of high radiation and instructing workers not to spend any longer in the area than necessary to do their jobs.
Concern among scientists is rising, because in the last few years researchers have doubled their estimate of the damage to cells caused by neutrons. These sub-atomic particles are prevalent at high altitudes.
In addition, planes today fly for longer periods at higher altitudes, with less of the atmosphere to shield them from cosmic sources of radiation, specialists say. The Concorde and corporate jets, which fly even higher than standard passenger planes, are especially vulnerable. More and more planes fly between North America and Asia or Europe over the North Pole, where radiation levels are four times those at the equator because of the effect of the Earth's magnetic field.
Dr. Barish said some sort of forecasting was needed, for example, to help pregnant women decide whether to fly on a particular day. Solar radiation peaks every 11 years, and at a handful of times in the cycle radiation fields are so high, he noted, that the dose on a single flight can exceed the recommended monthly maximum for a fetus.