A study published this week in JAMA Internal Medicine found that among 503 US occupations, flight attendants had the highest proportion of deaths from radiation-related cancers and pilots the second-highest rate. This was ahead even of workers who handle radioactive materials directly, so it is quite shocking, and the evidence seems clear. Past studies have been limited in that they cannot determine directly whether exposure increases the risk of cancer mortality.

Research shows that flight crew (both pilots and flight attendants) receive the highest annual dose of ionizing radiation, more than any other workforce in the United States, largely due to exposure to cosmic radiation at high altitudes. Flight crew are also more likely to be diagnosed with certain cancers than the general population. Are crew aware of this risk, and what can they do to mitigate it? Are the airlines aware, and do they inform their crew? In this article, we will take a deep dive into the studies and find out what it really all means.

Cosmic Radiation Is Key

Credit: Shutterstock

The Earth is continuously bombarded by high-energy radiation from the sun, called solar radiation, and from the rest of the solar system, known as galactic radiation. These together are collectively known as cosmic radiation. Some of this cosmic radiation is absorbed by the Earth’s atmosphere. The intensity and power of this kind of radiation diminish rapidly with atmospheric thickness, so flying at high altitude increases exposure to cosmic radiation.

Because cosmic radiation increases with altitude and latitude, air travel results in an additional radiation dose compared with staying on the ground. Higher doses are associated with long-haul and trans-polar flights, for example, from North America to Europe or Asia. Short-haul flights in the same region are associated with lower levels of cosmic radiation. One short flight gives less radiation than a standard medical X-ray or a few days of normal outdoor life on Earth, according to the National Institute of Health.

The World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) say that ionizing radiation causes cancer in humans. For females, a National Institute for Occupational Safety and Health (NIOSH) study found that exposure to just 0.36 millisieverts (mSv) or more of cosmic radiation in the first trimester may be linked to an increased risk of miscarriage.

Strong Evidence

Credit: Shutterstock

Researchers from Harvard Medical School and their colleagues examined more than 12.7 million deaths recorded between 2020 and 2024, using federal mortality data newly linked to each decedent’s usual occupation. Of these, 14,000 were Pilots and 7,000 were flight attendants. The latter showed roughly 50% higher odds of dying from a radiation-related cancer than the general working population; for pilots, the figure was about 36%.

The study’s most persuasive feature is that neither group showed elevated death rates from cancers not linked to radiation, such as colon cancer. Two Australian radiation experts writing an accompanying commentary noted that this pattern supports occupational radiation exposure as the main factor, rather than lifestyle or socioeconomic factors. In all, about 6.9% of deaths among flight attendants and 6.7% of deaths among pilots were from radiation-related cancers, according to the studies. These were higher than in any other profession, including that of nuclear technologists.

“Aircrew members represent a unique occupational group exposed to a constellation of known and probable carcinogens, including cosmic ionizing radiation (CIR) at cruising altitude, UV-A radiation penetrating cockpit windows (for pilots), and circadian rhythm disruption from night-shift work and repeated time zone crossing,” the commentary writers, Catherine Olsen and Ken Karipidis, wrote in the studies.

The Facts And Figures

Credit: Shutterstock

Flight crew accumulate an estimated 3 to 6 millisieverts (mSv) of cosmic radiation annually, depending on routes flown and altitude, against roughly 0.4 millisieverts for a passenger taking ten cross-country round trips a year, according to the US Centers for Disease Control and Prevention (CDC). The Federal Aviation Administration (FAA) has classified flight crew as radiation workers since 1994, but the United States sets no federal dose limits and requires no monitoring. This is unlike other radiation-exposed occupations domestically or aircrew working in other countries such as the UK and within Europe.

Flight crew who fly below 26,000 feet (8,000 meters) are unlikely to receive radiation doses exceeding one millisievert (mSv) per year, the radiation dose limit for the public as specified by law. Those crew who fly above 26,000 feet will receive higher doses of cosmic radiation. Aircraft that operate above 50,000 feet are required to be equipped with cosmic radiation detection and measurement equipment, according to the International Civil Aviation Organization (ICAO).

The FAA recommends that airlines educate crew members on ionizing radiation exposure. However, it does not enforce mandatory federal limits or require routine exposure monitoring, and cosmic radiation is an advisory consideration rather than a strictly regulated workplace hazard. Labor organizations and flight attendant unions (such as the Association of Flight Attendants—CWA) argue that U.S. aircrews face higher average ionizing radiation exposure than many ground-based nuclear or medical radiation workers, yet lack the same legal tracking, training, and mandatory safety mitigations, according to ALPA.

What Do These Findings Suggest?

Credit: American Airlines

The authors of the new studies are careful to note that the findings do not establish that the data can measure any individual’s actual dose of cosmic radiation. Occupations are sometimes misrecorded on death certificates, and cosmic radiation, UV-A exposure, and circadian disruption from irregular schedules and time zone crossings all occur together and can not be fully disentangled.

Radiation-related cancers analyzed included breast cancer, central nervous system cancers, multiple myeloma, leukemia (except chronic lymphocytic leukemia), lymphoma, thyroid cancer, prostate cancer, melanoma and nonmelanoma skin cancers. Pilots and flight attendants studied had statistically significantly higher rates of death from breast, central nervous system and prostate cancers, as well as melanoma. Pilots also had a higher rate of leukemia deaths, according to information at MedicalXpress.

The study is based on simple logic. If cosmic radiation was driving cancer among all flight crew, the signal should appear in the cancers that are known to be caused by radiation. The researchers expected to see higher rates of radiation-associated cancers among other workers exposed to radiation, like nuclear technologists. They also did not expect to see higher rates among aviation workers who remain on the ground, such as aircraft mechanics.

How Can Airlines Manage The Risk?

Credit: Shutterstock

Airlines need to evaluate the exposure of their flight crew to cosmic radiation and whether they receive between 1 mSv and 6 mSv of exposure or above that, in any twelve-month period. Laws in Europe require that exposure to cosmic radiation be assessed and recorded, and that airlines must inform crew of the risks to their health. Major carriers like Air France and other European operators adjust flight schedules or re-route planes if crew exposure approaches legal limits. When a pregnancy is declared by a crew member, they are immediately transferred to working on the ground, because of the known risks.

The assessment of each individual air crew dose is made by combining route dose with crew roster data. Route dose estimates can be calculated using computer programs specifically designed for that purpose. Flight crew can calculate their usual cosmic radiation exposures. The Federal Aviation Administration (FAA) CARI program website allows you to enter information to estimate your effective dose of cosmic radiation for a flight.

The study’s findings cannot determine how large the risk is for any individual crew member. However, the authors do suggest “That the workers who absorb the most radiation of any occupation in the country deserve the same basic protections we extend to everyone else who works around it.” The National Academies urged the FAA to revise its approach to radiation exposure for all flight crew and describe their current approach as “insufficient”.

The Bottom Line

Credit: Shutterstock

The studies also state plainly that the results do not mean occasional leisure flying raises a passenger’s cancer risk; moreover, they reflect an entire career in the sky. To put this in perspective, pilots and flight attendants accrue an estimated 3 to 6 millisieverts of cosmic radiation each year. A traveler who takes 20 flights per year absorbs only about 0.4 millisieverts, roughly a seventh to 1/15 of what an aircrew member accrues in a single year.

Air travel is increasing annually in the United States, exposing approximately 43,000 pilots (out of approximately 351,000 globally) and 96,900 flight attendants (out of a global workforce of 400,000) to cosmic ionizing radiation (CIR) doses much higher than those experienced on the ground. The results of these recent studies suggest that support for occupational radiation protection for US aircrew members should be considered commensurate with their level of exposure to cosmic radiation.

“This study further confirms radiation-related cancers that cause mortality must be acknowledged as occupational deaths,” said Sara Nelson, president of the Association of Flight Attendants-CWA. “The risk is known, but crew are not educated or informed. And, no one is taking responsibility.”