Published in JAMA Internal Medicinethe Harvard study does not prove that cosmic radiation is directly responsible for these cancers. But it provides new arguments in favor of better monitoring of the professional exposure of crews.
A job in the sky, an invisible exhibition
Flying regularly means crossing, for hundreds of hours each year, an environment where the atmosphere protects less effectively from cosmic radiation. This exposure is imperceptible and does not cause any immediate symptoms. But it accumulates over the course of a career.
Researchers at Harvard Medical School analyzed American death certificates recorded between 2020 and 2024. Their database included nearly 13 million people spread across 503 professionsof which approximately 14,000 pilots and 7,000 flight attendants. The results were published on August 17, 2026 in JAMA Internal Medicine.
After taking into account age, gender, race, education level and marital status, the researchers compared cancers considered to be radiation-related to those that were not.
The observation is striking: 6.9% of deaths among flight attendants and 6.7% among pilots were linked to cancers considered radiation-induced. These proportions were the highest of the 503 occupations studied.
More frequent cancers, and a path that is becoming clearer
Researchers observed significantly higher mortality for several cancers: breast, central nervous system, prostate and melanoma. Among pilots, an increase in deaths from leukemia was also noted.
Conversely, deaths from cancers not considered to be radiation-related were comparable to those in the general population. Aeronautical mechanics and assemblers did not have the same excess mortality either.
The contrast reinforces the interest of the signal, without however demonstrating causality.
The main particularity of the crews is their exposure to ionizing cosmic radiation. At high altitudes, the atmosphere filters them less effectively.
According to estimates cited in the study, a crew member receives approximately 3 to 6 millisieverts (mSv) per yeardepending on the flight paths. This is approximately ten times more than the estimated annual exposure of a traveler making ten transcontinental round trips, estimated at 0.4 mSv.
These are relatively small doses, but received repeatedly over years.
Should we better protect crews?
In France, the National Institute for Research and Safety (INRS) estimates that commercial flight crews receive on average around 2 mSv per yearwith values that can approach 5 mSv for the most exposed. Beyond 1mSvregulations already impose preventive measures and dosimetric monitoring via the SIEVERTPN and SISERI systems. The contrast is clear with the United States, where the Federal Aviation Administration recognizes crews as exposed workers, but where there is no federal dose limit or systematic monitoring obligation.
The authors believe that these results argue for protection more proportionate to the level of exposure.
But radiation is probably not the only factor involved. Night work, irregular hours, disruption of biological rhythms or exposure to ultraviolet rays can also influence the health of crews.
Above all, study does not prove that cosmic radiation causes observed cancers. It is based on death certificates and a comparison between professions, without measuring the individual dose received by each worker.
It is therefore not a question of saying that a pilot or a flight attendant will develop cancer because of their job. But this work raises an essential question: when a profession is particularly exposed to a potentially carcinogenic factor,
can we really prevent the risk without precisely measuring exposure over the course of a career?
For researchers, better documenting this exposure is a first step in determining how to further protect those who spend their professional lives in the sky.