LYON—Exposure to inflight cosmic radiation, a long-suspected occupational hazard for crew members, is clearly associated with elevated cancer incidence, a new study shows.
The research, published on the American Medical Association’s JAMA Network website, strengthens previous work on the subject. It supports considering radiation protections for crew members, the authors say. In July, France’s Social Division of the Bayonne Judicial Court recognized that a flight attendant’s breast cancer had an occupational origin, including exposure to ionizing radiation.
Aircrew members receive the largest mean annual effective dose of ionizing radiation of any occupational group in the U.S., the authors say. Cosmic rays encountered at commercial flight altitudes are the source, but studies so far have been relatively inconclusive. They have been limited by small numbers of deaths, for example.
The authors analyzed mortality from radiation-related and non-radiation-related cancers among pilots and flight attendants. Using epidemiological studies and cancer site-specific risk models, they included breast, central nervous system, multiple myeloma, leukemia, lymphoma, thyroid and prostate, as well as melanoma and non-melanoma skin cancers, in radiation-related cancers. They excluded lung cancer to reduce potential confounding, given its association with smoking.
The analysis of more than 12 million death certificates in the U.S. between 2020-24 enabled a comparison between 503 occupations, including 14,190 pilots and 7,170 flight attendants. The outcome for the crew members was juxtaposed with results for a group of nuclear technologists, for their exposure to radiation, and a group of workers in aircraft manufacturing and maintenance, for their exposure to aircraft.
Flight attendants, at 6.9%, and pilots, at 6.7%, had the highest and second-highest risk-adjusted percentage of deaths from radiation-related cancers. The authors did not observe that pattern for non–radiation-related cancer deaths, for which aircrew ranked near the median.
“Our findings are consistent with prior epidemiological studies linking aircrew occupation with elevated cancer incidence and extend the literature by ranking aircrew against 503 occupations,” the authors say. They admit their study may be limited by factors such as unmeasured confounding for variables—circadian disruption and exposure to engine bleed air, for instance.
“However, specificity of these findings to air crews suggests an association between large, cumulative inflight cosmic radiation exposure and a heterogeneous group of radiation-related cancers,” the authors say. “Pilots and flight attendants accrue an estimated 3-6 millisieverts per year of cosmic radiation, greatly exceeding the 0.4 millisieverts received by an air traveler taking 10 cross-country roundtrip flights per year.”
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