The findings support considering occupational radiation protections for US aircrew members that are commensurate with their level of exposure, said senior author Anupam Jena, the Joseph P. Newhouse Professor of Health Care Policy at the Blavatnik Institute at Harvard Medical School, and his team.

Aircrew members are known to receive the highest annual effective dose of ionizing radiation among US workers, largely because of exposure to cosmic radiation at high altitudes. Members of the profession are also more likely to be diagnosed with certain cancers than the general population, according to Harvard Medical School.

However, previous research has been limited in determining whether this exposure translates into higher rates of cancer mortality.

The new study, published on August 17 in JAMA Internal Medicine, examined the issue using a larger dataset and greater statistical power than previous studies.

Led by first author Vishal Patel, an HMS clinical fellow in surgery at Brigham and Women’s Hospital, the researchers used a single population-based data source — the National Vital Statistics System — rather than individual occupational or cancer cohorts.

Patel and his colleagues examined all US death certificates from 2020 to 2024. The records have only recently been linked to the occupations of deceased individuals and provided data on nearly 13 million deaths across 503 occupations, including around 14,000 pilots and 7,000 flight attendants.

The researchers used a common adjustment approach to account for factors other than occupation that could affect mortality. These included age at death, sex, race, ethnicity, educational attainment and marital status.

They analyzed radiation-related and non-radiation-related cancer deaths across occupations and also compared flight crew members with ground-based aviation workers.

The radiation-related cancers examined included breast cancer, central nervous system cancers, multiple myeloma, leukemia excluding chronic lymphocytic leukemia, lymphoma, thyroid cancer, prostate cancer, melanoma and non-melanoma skin cancers. Lung cancer was excluded to reduce potential confounding from smoking.

The researchers found that pilots and flight attendants had statistically significantly higher death rates from breast, central nervous system and prostate cancers, as well as melanoma. Pilots also had a higher rate of deaths from leukemia.

Overall, about 6.9% of deaths among flight attendants and 6.7% of deaths among pilots were attributed to radiation-related cancers, according to the analysis.

The proportions were higher than those recorded in any other occupation studied. Nuclear technologists, who are routinely exposed to radiation from non-cosmic sources, ranked 12th on the list.

By comparison, aircraft mechanics and assemblers did not show higher rates of radiation-related cancer deaths than other occupations.

The researchers also found that rates of non-radiation-related cancer deaths among aircrew members were similar to those in the general US population.

According to the US Centers for Disease Control and Prevention (CDC), aircrew members receive an estimated 3 to 6 millisieverts of cosmic radiation annually, depending on their flight routes. This is roughly an order of magnitude higher than the estimated 0.4 millisieverts received annually by an average air traveller taking 10 cross-country round trips.

The Federal Aviation Administration (FAA) formally recognises pilots and flight attendants as being occupationally exposed to ionizing radiation. However, unlike other radiation-exposed workers or aircrew in some other countries, US aircrew members are not subject to federal radiation dose limits or mandatory radiation monitoring requirements.