When we think of occupations exposed to radiation, images of nuclear power plants, laboratories, or X-ray rooms often come to mind. However, a recent study reveals that the most affected professions are found at altitudes far above the ground. Flight attendants top the list, followed closely by pilots, as the occupations with the highest rates of radiation-related cancer deaths in the United States.
This study, published on 17 August in JAMA Internal Medicine, examined over 12.7 million recorded deaths in the United States from 2020 to 2024 and compared 503 different occupations. After adjusting for factors such as age, sex, ethnicity, education, and marital status, it was found that approximately 6.9% of deaths among cabin crew and 6.7% among pilots were attributed to radiation-related cancers.
Cosmic Radiation at High Altitudes
Cosmic rays consist of high-energy particles originating from the Sun and other space sources. The Earth’s atmosphere provides a protective shield against this radiation; however, this protection diminishes with altitude. Commercial aircraft typically cruise at altitudes exceeding 30,000 feet (approximately 9,100 metres), where pilots, crew members, and passengers are exposed to higher doses of ionising radiation than at sea level. This type of radiation possesses sufficient energy to damage DNA, and prolonged exposure can contribute to the development of cancer.
The link between ionising radiation and certain cancers has been established for many years. A scientific review published in 2022 indicates that there is sufficient evidence to consider ionising radiation a causal factor for various cancers, including those of the breast, salivary glands, oesophagus, stomach, colon, lungs, bones, kidneys, bladder, brain, central nervous system, thyroid, and non-melanoma skin.
For other tumours, such as prostate cancer, associations have been identified, but they do not yet reach the threshold necessary to establish direct causality. In the case of melanoma, the evidence remains inconclusive.
Estimating Radiation Exposure Among Aviation Professionals
The study published in JAMA Internal Medicine estimates that pilots and crew members may accumulate between 3 and 6 millisieverts (mSv) of cosmic radiation per year, though this varies depending on flight routes. The millisievert is a unit used to express radiation dose and its potential effects on the body.
Not all flights entail the same level of exposure. The National Institute for Occupational Safety and Health (NIOSH) explains that exposure can increase during long-haul flights, on routes at high latitudes, or flights that pass over the poles. Additionally, radiation levels may fluctuate due to solar phenomena, such as solar flares.
Linking Cancer Deaths to Radiation Exposure
For their analysis, researchers grouped various types of cancers associated with radiation exposure and compared their incidence across the 503 occupations studied. Among pilots and cabin crew, a higher mortality rate was observed for breast, prostate, and central nervous system cancers, as well as melanoma. In pilots, an increased mortality rate for leukaemia was also noted.
The team conducted further comparisons to determine whether this pattern was specifically associated with occupations exposed to radiation. Remarkably, pilots and crew members ranked highest in deaths from cancers related to radiation exposure, yet they fell to nearly the midpoint when examining other cancer types.
A similar pattern emerged when comparing different professions. Nuclear technologists, who may also be exposed to radiation, ranked 12th, while ground-based employees in the aviation industry, such as mechanics and aircraft assemblers, did not exhibit elevated mortality rates.
Challenges in Isolating Causality
One of the study’s significant limitations is that researchers were unaware of the radiation doses received by each individual throughout their careers. The analysis relied on the usual occupation listed on death certificates, which may contain inaccuracies. Working on an aircraft also entails other exposures that are difficult to disentangle. Pilots and crew frequently traverse multiple time zones, work night shifts, and alter their sleep cycles, disrupting their circadian rhythms. NIOSH includes these disruptions among the factors that may contribute to the observed differences in cancer rates among aircrew, although the extent of each factor’s contribution to risk remains unclear.
Moreover, pilots may be exposed to ultraviolet radiation that penetrates the windows of certain aircraft cabins. UV radiation levels are higher at the altitudes of commercial flights, although the amount that passes through the windows depends on the materials used in their construction. Other occupational and personal factors can also influence cancer development. Therefore, the authors caution that their findings do not allow for a direct attribution of deaths solely to cosmic radiation.
Implications for Aviation Professionals
This research opens a vital debate concerning the protection of those who fly as part of their profession. The Federal Aviation Administration (FAA) recognises pilots and crew members as workers exposed to ionising radiation; however, there are currently no federal dose limits or requirements for individual monitoring of radiation exposure among aircrews in the United States.
For passengers, the exposure levels are markedly different. An individual undertaking ten round trips across the United States in a year would receive approximately 0.4 mSv of cosmic radiation, according to the comparisons used by the researchers. In contrast, a pilot or crew member may accumulate between 3 and 6 mSv annually, repeating that exposure for much of their working lives.
Regulatory approaches also vary globally. The European Union mandates that crew exposure is evaluated when it is expected to exceed 1 mSv per year, and that this is considered when scheduling work hours, alongside informing workers about the risks and doses they receive. If exposure is projected to surpass 6 mSv annually, additional protective measures must be implemented.
The authors suggest that these findings could serve as a basis for revisiting how accumulated exposure for pilots and crew members is measured and regulated in the United States. Nonetheless, they emphasise a crucial point: these results do not warrant a cessation of flying, nor do they conclude that cosmic radiation is the direct cause of these deaths.