Answer to Question #6801 Submitted to "Ask the Experts"

As a flight attendant for a commercial airline, I am flying at 30,000 feet plus for 75 hours a month (this does not include the ascent and descent intervals).

• How much radiation am I exposed to over the span of a month? Over the span of 25-plus years?
• Should I be concerned about this? Can I do anything or take anything to limit my exposure or absorption of radiation (other than quitting)?
• Has there been testing on the flight crews?
• Do any airlines, domestic or international, provide a radiation-detecting device for use while flying?
• Is radiation exposure more of a problem at certain altitudes, or direction of flight (east/west or north south), or different hemispheres?
• Does it affect pilots (because of the windshield) or flight attendants (moving about the cabin expending energy) more or less?
• Is there a tracking of flight crews and illnesses/diseases that could possibly be attributed to radiation from flying?

Radiation exposure in a commercial airliner is determined both by the altitude and, to a lesser extent, by latitude, the position of the aircraft relative to the pole and the equator. Assuming that you are flying at latitudes typical of the central United States, the dose rate at an altitude of 30,000 feet is about 4 microsievert¹ per hour. Thus your annual exposure would be approximately 3,600 microsievert or 3.6 millisievert², a value that is not unusual for a flight attendant. If your flying career lasts 25 years, your lifetime-accumulated exposure would be about 90 millisievert. 

Here is the position of the Health Physics Society: In accordance with current knowledge of radiation health risks, the Society recommends against quantitative estimation of health risks below an individual dose of 50 millisievert in one year or a lifetime dose of 100 millisievert above that received from natural sources. There is substantial and convincing scientific evidence for health risks following high-dose exposures. However, below 50-100 millisievert (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent.

So, if my estimate of 90 millisievert over your lifetime is accurate, your risk from in-flight radiation is really quite small or possibly nonexistent. If one widely used model (the model favored by the Federal Aviation Administration [FAA]) of risking a fatal cancer through radiation exposure is used to estimate your increased lifetime risk, it MIGHT possibly change from around 25 percent to 25.1 percent. Is this a cause for concern? That is really a matter for you to decide based on appropriate understanding of the magnitude of that potential risk compared with the risks of many other activities that you ordinarily pursue.

Since radiation exposure rates in aircraft vary considerably with altitude, doubling with approximate changes of 6,500 feet, you could lower your exposure by only working short-haul routes. The highest exposure rates are found on polar routes at high altitude. A typical nonstop flight from New York to Tokyo over the pole would give a dose of about 90 microsievert. If you were to work that route six times a month for 25 years, your total exposure would be 160 millisievert, a dose that can be calculated to increase your cancer risk by another 0.1 percent.

In-flight radiation of this sort is not influenced by one's role as a pilot or flight attendant. Cosmic radiation comes through the skin of the aircraft as well as through the windows, so position inside the cabin is not critical. Because there is a variation with latitude, the dose rates do change with north-south travel compared with east-west travel at the same altitude. There is about a factor of three difference in exposure rates between the north and south poles and the equator.

Regarding the difference between domestic and international airlines, all 27 nations of the European Union require radiation dose assessment for all of their flight crew and cabin staff. In the United States, the FAA has not passed any regulations that would force U.S.-based carriers to do the same—even though they classified all crew members as radiation workers in 1994.

Because the radiation encountered at altitude is a complex mixture of radiation types and energies, accurately measuring the dose that a person would receive while on an aircraft would, using current technology, require rather complex and bulky instrumentation rather than the simple radiation devices worn by other radiation workers, such as those you find clipped onto the collars of x-ray technicians.

Instead, a computer program such as the FAA-endorsed CARI-6 software or the European EPCARD (European Program Package for the Calculation of Aviation Route Doses) is applied to a simple flight plan containing airports of origin and termination, flight altitudes, and trip duration, and the computer programs then derive an applicable radiation dose for that particular journey. It is that number, rather than a measured dose reading, that goes into the personal log of all European crew after each trip.

Since this issue became a matter of international concern almost 20 years ago, various studies have been conducted on the health of pilots and flight attendants with the goal of seeking to determine if their radiation exposure was causing increased health problems. To date, the results of these studies have been equivocal. The documented increased breast cancer in flight attendants has been ascribed to hormonal changes associated with disruption of normal sleep cycles. Pilots generally display the "healthy worker" effect, a term used to describe people whose health status and susceptibility to disease does not mirror that of the population at large. More research is underway to see if in-flight radiation exposures at the levels presently encountered are indeed too small to be observed or are simply nonexistent. It is, in my opinion, the right of every U.S.-based crew-member to receive the information necessary to understand this subject. See what the medical directorate of your airline offers in the way of educational material.

Robert J. Barish, PhD, CHP, DABR, FAAPM

¹A microsievert is equal to 1,000,000 of a sievert.
²A millisievert is equal to 1/1,000 of a sievert or 1,000 times a microsievert.