Pilots and flight attendants may face a greater risk of dying from certain radiation-related cancer because of repeated exposure to cosmic radiation at high altitudes, a new study has found.

The research, published August 17 in JAMA Internal Medicine, compared mortality data across more than 500 occupations in the United States. Researchers found that pilots and flight attendants had the highest and second-highest proportions of deaths from cancers considered potentially linked to ionising radiation.

The findings add to a long-running scientific debate over whether the radiation encountered during commercial flights translates into a measurable increase in cancer mortality among aircrew.

Importantly, the study identifies an association. It does not establish that cosmic radiation directly caused the deaths.

Why are pilots and flight attendants exposed to cosmic radiation?

Earth’s atmosphere and magnetic field provide substantial protection from high-energy particles originating in space.

That protection becomes weaker as aircraft climb to cruising altitude. Aircrew members therefore encounter more ionizing radiation than people working at ground level.

The exposure comes primarily from galactic cosmic radiation, along with radiation generated by interactions between cosmic particles and Earth’s atmosphere.

The amount varies according to several factors, including:

• Flight altitude
• Duration of the flight
• Geographic latitude
• Solar activity
• The number of hours a crew member spends in the air

Aircrew members can therefore accumulate exposure over hundreds or thousands of flights during a career.

Previous research has consistently identified aircrew as an occupational group with unusually high exposure to cosmic ionizing radiation. However, establishing whether that exposure causes additional cancer deaths has been considerably more difficult.

What did the new study find?

Researchers analyzed 12.7 million deaths recorded in the United States between 2020 and 2024, covering 503 occupations.

The dataset included approximately:

• 14,000 pilots
• 7,000 flight attendants
• Workers in hundreds of other professions
• Nuclear technologists, who routinely work around other sources of ionizing radiation
• Ground aircrew, who share some characteristics with aviation workers but do not experience the same level of in-flight radiation exposure

The researchers compared deaths attributed to cancers considered radiation-related with deaths from cancers not thought to be associated with radiation.

That second comparison was important.

If aircrew simply had unusually high cancer mortality overall, their results would be less suggestive of a radiation-specific association.

Instead, the researchers found that aircrew ranked relatively normally for cancers that were not considered radiation-related.

Pilots accounted for 6.7% of deaths in the study attributed to radiation-related cancers, while flight attendants accounted for 6.9%.

Those were the highest proportions among the occupations examined.

Why did researchers compare aircrew with nuclear workers?

The comparison with nuclear technologists provides an important piece of context.

Nuclear workers can encounter ionizing radiation from entirely different sources, generally in controlled occupational environments.

In the study, nuclear technologists ranked 12th among the 503 occupations for the proportion of radiation-related cancer deaths.

That result does not prove that radiation caused cancer in either group. But it provided researchers with an additional comparison group exposed to a known occupational source of ionizing radiation.

Lead author Vishal Patel said the findings were particularly notable because aircrew were not similarly elevated for cancers that were not considered radiation-related.

“The checks held,” Patel said, according to the study’s reported findings. “Aircrew ranked near the middle” for cancers not thought to be radiation-related.

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The researchers argued that this pattern is consistent with, though does not prove, a potential role for ionizing radiation.

Which flights expose crews to the most radiation?

Not every flight produces the same radiation exposure.

The highest doses generally occur on flights that are long, high-altitude and closer to the poles.

Earth’s magnetic field is particularly important here. It deflects some incoming charged particles from space, but its protective effect varies with latitude.

At higher latitudes, that shielding is weaker.

As a result, polar and ultra-long-haul flights can expose crews to higher radiation doses than shorter flights at lower latitudes.

This means that two flight attendants with the same number of years in the industry may not necessarily have accumulated the same radiation exposure.

A crew member regularly flying long-haul routes between North America, Europe and Asia may experience a different cumulative dose from someone primarily operating short domestic routes.

Does cosmic radiation cause cancer?

Ionizing radiation can damage DNA, which is one reason prolonged or sufficiently high exposure is recognized as a cancer risk.

But the relationship between the relatively low doses experienced by aircrew and cancer is complicated.

Previous epidemiological research has found higher rates of certain cancers among aircrew, but researchers have struggled to isolate cosmic radiation from other characteristics of the profession. A major review of the evidence concluded that a causal link between cosmic ionizing radiation and cancer in aircrew had not been firmly established.

Aircrew members also differ from the general population in many other ways.

Their work can involve:

• Irregular schedules
• Night-shift work
• Disrupted circadian rhythms
• Frequent time-zone changes
• Sleep disruption
• Different patterns of ultraviolet exposure
• Lifestyle and occupational factors

Those variables can complicate attempts to determine exactly what is responsible for an observed increase in cancer.

The new study attempts to address some of that problem by comparing radiation-related cancers with other cancers and by examining hundreds of occupations rather than relying solely on the general population.

What cancers were included in the study?

The researchers examined several cancers that have previously been associated with ionizing radiation.

These included cancers involving the:

• Breast
• Central nervous system
• Skin, including melanoma
• Thyroid
• Prostate
• Blood and lymphatic system

The researchers excluded lung cancer from their radiation-related category to reduce the potential influence of smoking, according to reporting on the study.

That approach was intended to make the comparison more meaningful because occupational and lifestyle factors can otherwise obscure the relationship being studied.

Are airlines required to monitor cosmic radiation exposure?

This is where the study could have implications for aviation policy.

The researchers said the United States currently does not impose occupational radiation dose limits or mandatory individual monitoring requirements for commercial aircrew comparable to those used in some other radiation-exposed occupations.

Their recommendation is not necessarily to ground aircraft or dramatically redesign planes.

Instead, they argue that a practical first step would be to estimate and record individual radiation exposure over a crew member’s career.

Patel suggested that dose estimates should follow workers when they change employers, creating a cumulative record of occupational exposure.

That could allow employers and regulators to identify workers with unusually high lifetime exposure and potentially develop more targeted health protections.

Would shielding aircraft solve the problem?

Not necessarily.

The study’s authors argue that simply trying to shield aircraft from cosmic radiation is not an easy solution.

Aircraft already operate within strict weight constraints, and adding substantial shielding could increase aircraft weight and fuel consumption.

The more practical approach may involve monitoring and managing exposure rather than attempting to block all cosmic radiation.

Potential measures could include:

• Individual exposure estimates
• Career-long radiation records
• Greater awareness among aircrew
• Exposure-based occupational guidance
• Further research into health effects
• Consideration of dose limits for particularly exposed workers

The exact regulatory response would require additional scientific and policy evaluation.

Are passengers exposed to the same radiation?

Yes — but generally at much lower cumulative levels.

Every passenger flying at cruising altitude is exposed to some cosmic radiation.

The difference is frequency and duration.

A person who takes a few long-haul flights each year spends a relatively small amount of time at cruising altitude. A flight attendant or pilot may spend thousands of hours there over an entire career.

Reported estimates put annual occupational exposure for aircrew in the range of several millisieverts, while even frequent travelers generally accumulate much less from flying.

That means the new findings should not be interpreted as a warning that ordinary passengers are facing an immediate cancer danger every time they board a plane.

The concern is primarily about repeated occupational exposure over decades.

What does the study mean for frequent flyers?

For most passengers, the findings are unlikely to change how they travel.

The radiation dose from an individual commercial flight is relatively small. The occupational issue arises because aircrew repeatedly encounter that exposure as part of their jobs.

The distinction is similar to many occupational hazards: a single exposure may be small, while repeated exposure over an entire working life can become more significant.

That is why the researchers are calling for occupational protections aimed specifically at aircrew rather than broad warnings for the traveling public.

What happens next?

The study is unlikely to settle the scientific debate by itself.

Its biggest contribution may be identifying a pattern that warrants closer investigation.

The researchers used death certificates and occupation data, which allowed them to examine a very large population. But this type of observational research cannot establish precisely how much radiation an individual received or prove that radiation was the cause of a particular person’s cancer.

Future studies could strengthen the evidence by combining occupational histories with individual flight schedules, altitude, latitude and estimated radiation doses.

That would allow researchers to ask a more precise question: Does cumulative cosmic radiation exposure predict cancer risk among aircrew?

For now, the message is more measured than “flying causes cancer.”

Pilots and flight attendants spend far more time exposed to cosmic ionizing radiation than ordinary travelers. The new research suggests that the pattern of cancer mortality among these workers deserves greater attention — and that regulators may need better systems for measuring and managing their lifetime occupational exposure.