Pilots and flight attendants spend much of their working lives high above the ground, where the atmosphere provides less protection from radiation arriving from space.
A large U.S. study has now found that these two occupations had the highest proportions of deaths from cancers that can be related to radiation exposure among more than 500 occupations examined.
The research was led by scientists from Harvard Medical School and Brigham and Women’s Hospital.
The team examined nearly 13 million U.S. death records and compared patterns across 503 occupations. Their results were published on August 17 in JAMA Internal Medicine.
People on Earth are constantly exposed to small amounts of natural radiation. At cruising altitude, however, aircraft crews receive more cosmic radiation because there is less atmosphere above them to absorb it.
The amount can vary according to altitude, flight route, latitude and the amount of time spent flying.
Previous research has shown that pilots and flight attendants receive unusually high occupational exposure to ionizing radiation. According to estimates cited by the researchers, aircrew members may receive about 3 to 6 millisieverts of cosmic radiation each year, depending on their routes. This is far more than the exposure of an average passenger who flies occasionally.
Scientists have also reported higher rates of some cancers among aircrew members. However, many earlier studies were too small to determine clearly whether those diagnoses translated into higher cancer death rates. The new study was designed to provide a much broader picture.
The researchers used the U.S. National Vital Statistics System and examined death certificates from 2020 through 2024. Occupational information has only recently been linked to these records, allowing researchers to compare causes of death across a very large number of jobs. The data included about 14,000 pilots and 7,000 flight attendants.
The researchers adjusted their calculations for several personal factors that could influence mortality. These included age at death, sex, race, ethnicity, education and marital status. This approach helped make comparisons between occupations more meaningful, although it cannot remove every possible difference between workers.
The team focused on cancers that previous research has connected with radiation exposure. These included breast cancer, cancers of the central nervous system, leukemia, lymphoma, multiple myeloma, thyroid and prostate cancers, melanoma and other skin cancers. They then examined how often these cancers appeared as causes of death in different occupations.
Flight attendants ranked highest among all 503 occupations for the proportion of deaths involving these radiation-related cancers. About 6.9% of deaths among flight attendants were attributed to cancers in the group studied. Pilots ranked second, with about 6.7% of deaths involving these cancers.
Several individual cancers also stood out. Pilots and flight attendants had significantly higher rates of death from breast cancer, cancers of the central nervous system, prostate cancer and melanoma. Pilots also had a higher rate of death from leukemia.
The comparison with other radiation-exposed workers was particularly interesting. Nuclear technologists, who can encounter radiation as part of their jobs and are generally subject to workplace safety procedures, ranked 12th rather than first or second. The researchers argue that this difference raises questions about whether U.S. aviation workers receive enough protection.
The Federal Aviation Administration recognizes pilots and flight attendants as workers who are occupationally exposed to ionizing radiation. Yet U.S. aircrew members are not covered by the same federal radiation dose limits and monitoring requirements that apply to some other radiation-exposed workers. Some other countries have stronger monitoring systems for aircrew exposure.
Cosmic radiation cannot simply be removed from the sky, but exposure can potentially be estimated and managed. Flight schedules, altitude, latitude and routes all affect dose, and flights closer to the poles can involve greater exposure. Monitoring cumulative exposure could help employers and workers understand how much radiation a crew member receives over a career.
Senior author Anupam Jena of Harvard Medical School said the results support considering occupational protections that better match the radiation exposure experienced by U.S. aircrew. Such protections could include more systematic monitoring or other measures designed to limit unnecessary cumulative exposure. The study itself did not test which policy would work best.
The findings are important, but they do not prove that cosmic radiation caused every excess cancer death seen among pilots and flight attendants. This was an observational study based on death certificates and occupational records. It could not directly measure the radiation dose received by each individual worker throughout a career.
Other factors may also contribute to cancer risk in aviation workers. Aircrew can experience disrupted sleep, irregular working hours, repeated changes in time zones and other occupational exposures. Lifestyle and reproductive factors could also differ between occupational groups, and not all of these variables were available in the death records.
Another limitation is the relatively short period covered by the linked death data, from 2020 to 2024. Cancer can develop over decades, so longer follow-up and individual radiation histories would provide stronger evidence. Still, the enormous data set gives the study considerably more statistical power than many earlier investigations.
Overall, the research strengthens concern about the long-term health effects of working at high altitude. The unusually high proportion of radiation-related cancer deaths among both pilots and flight attendants is difficult to dismiss, particularly because these workers are known to receive substantial cosmic radiation exposure. The findings support further research and a closer look at how occupational radiation risks are monitored in U.S. aviation.
The study was led by Vishal Patel of Brigham and Women’s Hospital, with senior author Anupam Jena of Harvard Medical School. It was published August 17 in JAMA Internal Medicine.
