Answer to Question #8866 Submitted to "Ask the Experts"

I am a pilot and would like to ask about the increased health risks when flying an aircraft. I have been flying general aviation airplanes for three years and am currently flying cargo in a jet for the past three months, averaging a very significant amount of time at high altitudes in the Middle East.

Besides being curious of the increased health risks if any, I would appreciate statistics. I would also be interested in finding out if there is some way to prevent any health risks associated with the job, while keeping active in it.

You ask about the health risks of piloting a cargo aircraft at high altitude and what, if anything, can be done to minimize the risks. The likelihood is that your risk from in-flight radiation is small or nonexistent. But your general question leads to a discussion of a number of factors that might impact pilot health, all of which are associated with occupancy of an aircraft cockpit as an occupational choice.

Studies have been done related to the air quality in aircraft, as well as to the possible impact of other external factors, such as the cosmic radiation exposure associated with high-altitude flight. Since this site is primarily concerned with radiation issues, I will address this topic first.

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 Middle East, the dose rate at an altitude of 9,000 meters (m) is about 3 microsieverts per hour (µSv h^-1). Thus your annual exposure would be approximately 3,000 µSv or 3.0 millisieverts (mSv), a value that is not unusual for a pilot. If your flying career lasts 25 years, your lifetime accumulated exposure would be about 75 mSv. 

It is the position of the Health Physics Society that "below levels of about 100 mSv above background from all sources combined, the observed radiation effects in people are not statistically different from zero." So, if my estimate of 75 mSv over your career 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% to 25.1%. 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 2,000 m, you could lower your exposure by working only short-haul routes. The highest exposure rates are found on polar routes at high altitude.

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 exposure at the levels presently encountered are indeed too small to be observed or are simply nonexistent.

The second area of concern for your health may be the air quality inside the aircraft. This is significantly influenced by such factors as air recirculation, air exchange rate, and even the type of cargo being transported if it leads to the growth of microorganisms, bacteria, or fungi. Because air in the aircraft is recirculated with additional fresh make-up air added in varying amounts (depending on factors such as acceptable fuel consumption), there is a generally higher concentration of microorganisms in an aircraft than in many other environments. And some individuals may be more susceptible to infections from these components.

It is logical that keeping the cargo compartment clean and free of biological material, as well as increasing the mix of fresh air supplied to the cockpit, will lower the possibility of negative health effects from this type of contamination.

At high altitude, there is also a significantly greater concentration of ozone in the atmosphere. As such, the injection of fresh air increases the ozone concentration. Ozone has been associated with a variety of problems including headaches, fatigue, shortness of breath, chest pains, coughing, and irritation of the eyes, nose, or throat. Catalytic converters are used to reduce ozone concentration in aircraft, and these should obviously be maintained on a regular basis to maximize their efficiency.

Another factor that might influence pilot health is related to preflight inspection of the aircraft. Often, conducting these inspections involves inhalation of fumes from fuel while it is being loaded into the aircraft or from spills that might be located in the area where a pilot is walking around and inspecting landing gear, control surfaces, etc.

Unfortunately there is not a lot of quantitative data on the effects of air quality since individual susceptibility plays a significant role in determining the body’s response to these challenges.

If you are interested in obtaining calculated values of your radiation exposure as you continue your flying career, there are two freely available computer programs that require only the input of simple flight data to derive an exposure value. These are the CARI-6 program from the US FAA and EPCARD, the European Program Package for the Calculation of Aviation Route Doses, from the German Research Center for Environmental Health.

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