Flying introduces a barely perceptible increase in the natural radiation exposure everyone experiences daily. The concern during air travel focuses on cosmic radiation. While passengers and crew are exposed to slightly higher levels at cruising altitudes, the overall dose for the infrequent traveler remains low. Understanding the source and measurement of this exposure helps put the risk into perspective.
The Source: What is Cosmic Radiation?
Cosmic radiation consists of high-energy particles originating from the sun and deep space, primarily from events like supernovae. These particles, mainly protons and atomic nuclei, constantly bombard the Earth’s atmosphere. The Earth’s atmosphere and magnetic field act as a natural shield, deflecting or absorbing most of this radiation before it reaches the ground. At standard commercial flight altitudes (30,000 to 40,000 feet), this shielding effect is significantly reduced. When primary cosmic rays interact with the thin upper atmosphere, they create a cascade of secondary particles, such as neutrons and muons, which passengers and crew are exposed to.
Measuring Your Exposure Dose
Radiation exposure is quantified using the Sievert (Sv) and its smaller unit, the millisievert (mSv), which measures the biological risk to human tissue. The dose received during a flight is not constant and depends on three main variables: altitude, latitude, and solar activity. Altitude is the most significant factor, with dose rates at cruising height being roughly 15 times greater than at sea level. Latitude also influences exposure, as the Earth’s magnetic field deflects cosmic rays most strongly near the equator and weakest near the poles; thus, polar routes receive higher doses. Finally, solar activity plays a role, as intense solar flares can temporarily increase exposure.
Comparing Flight Radiation to Daily Life
For the average traveler, the radiation dose from a single flight is minor compared to other common, unavoidable sources of exposure. A round-trip, coast-to-coast flight within the United States exposes a passenger to about 0.03 to 0.035 mSv. This is a small fraction of the average annual background radiation dose from all natural sources, which is typically around 3 mSv per year. A single long-haul flight is equivalent to receiving less than one-third of the radiation dose from a standard chest X-ray (approximately 0.1 mSv). The dose from occasional air travel is considered too low to pose a measurable health risk to the general public.
Who Needs to Be Most Concerned?
While the occasional flyer has little cause for concern, radiation exposure from flying is considered an occupational risk for flight crew members. Pilots and flight attendants are classified as occupationally exposed workers because their high-altitude work leads to a greater cumulative dose.
Flight Crew Exposure
Annual exposure for flight crew can range from 0.2 to 5 mSv, with long-haul crew on polar routes receiving the highest doses, sometimes reaching up to 6 mSv per year. Airlines and crew are encouraged to use software to calculate flight-specific doses and adjust schedules to keep cumulative exposure within recommended safety limits.
Pregnant Travelers
Pregnant travelers are often advised to be mindful of exposure, though the risk remains negligible for infrequent flyers. For pregnant workers in aviation, the International Commission on Radiological Protection (ICRP) recommends a dose limit of 1 mSv over the entire pregnancy to protect the embryo or fetus.