A new study has found that flight attendants are at an increased risk for several types of cancers — and radiation exposure (at higher altitudes, there is less atmospheric protection against cosmic radiation from space) along with what's known as circadian rhythm disruption (hello, red-eye shifts and constant jet lag) have been cited as potential causes.
Cancer Rates and Cabin Crews
For the latest study, published in the journal Environmental Health, researchers used data from the Harvard Flight Attendant Health Survey, which included responses from more than 5,300 flight attendants. They compared those findings to data from nearly 3,000 adults with similar socioeconomic backgrounds: participants in the National Health and Nutrition Examination Survey (NHANES).
The results showed that for women, breast cancer was 1.5 times as prevalent in flight attendants as compared to in the general public, while melanoma was twice as prevalent and nonmelanoma skin cancers (like basal cell and squamous cell carcinomas) were four times as prevalent. Flight attendants also had higher rates of uterine, cervical, thyroid and gastrointestinal cancers.
In a release, study author Irina Mordukhovich, a research fellow at Harvard T.H. Chan School of Public Health, called the findings "striking," given the low rates of obesity and smoking in the flight attendants — 8 percent of participating flight attendants were current smokers, compared to 16 percent of the NHANES respondents.
The Role of Radiation
So what's to blame for the prevalence of cancer in flight attendants? Although the study didn't identify a cause (that wasn't its purpose), Mordukhovich and her colleagues offered up a few potential explanations, including flight attendants' exposure to cosmic ionizing radiation (or radiation from outer space).
We're exposed to small amounts of ionizing radiation all the time, though our atmosphere offers some degree of protection. At higher altitudes, where the air is thinner, more radiation gets through, which some researchers speculate may increase your cancer risk.
"Cabin crew have the largest annual ionizing radiation dose of all U.S. workers," pointed out study authors. Radiation dose is measured in millisievert per year (mSv), and previous research has shown that the average dose for cabin crews is 3.07 mSv, compared to 0.59 mSv for U.S. Department of Energy workers.
To help put those numbers in perspective, LIVESTRONG.COM spoke to Timothy J. Jorgensen, Ph.D., director of the Health Physics and Radiation Protection graduate program at Georgetown University.
He explains that natural background doses of radiation (the amount we're all exposed to right here on solid ground) range from about 3.0 mSv per year for residents of New York City (at about sea level) to 12.0 mSv per year in a high-altitude locale like Denver.
"So you can see that the most all crew members are getting a lower radiation dose than people living in Denver," Jorgensen says. "Since it's never been shown that people living in Denver, or any other areas with higher background doses, are at higher cancer risk because of their radiation exposure, I don't see how the allegedly higher risk of cancer for cabin crew members can be explained by their radiation doses, which are admittedly very small."
Experts estimate that exposure to 1 mSv radiation increases your cancer risk by 0.005 percent, so if a flight attendant worked for 30 years, for a cumulative exposure of 90 mSv, her increased lifetime risk of contracting a potentially fatal cancer would be 0.45 percent.
Given that small increase in risk, Jorgensen thinks the study authors' alternative explanations for the higher cancer rates "are more likely to be responsible than the radiation."
In addition to radiation exposure, flight attendants are exposed to other possible carcinogens (like jet fuel, pesticides used to kill onboard insects and flame-retardant chemicals), noted the study authors. But perhaps the explanation with the most research behind it is the irregular sleep schedules maintained by flight attendants.
In fact, a recent meta-analysis of 61 studies linked shift work and disrupted circadian rhythm with an increased risk of breast, skin and gastrointestinal cancers in women.
The reason? Our bodies do a better job of repairing DNA damage when we sleep during the night than if we sleep during the day, according to a 2017 study in the journal Occupational and Environmental Medicine. Study authors found that lower levels of melatonin, aka "the sleep hormone," in shift workers is likely to blame. (Light suppresses the hormone, which is normally secreted at night.)
"What seems to be happening, and this is supported by a lot of animal and cellular evidence, is melatonin normally drives repair of damage," explained lead author Parveen Bhatti, Ph.D., an epidemiologist with Fred Hutchinson Cancer Research Center, in a release. "So with low levels of melatonin, their repair machinery isn't functioning at optimal levels."
Bhatti and other researchers are looking into whether melatonin supplements might help counter the effect of working at night.
In the meantime, flight attendants are taking matters into their own hands. The Association of Flight Attendants-CWA, the main union for the group of workers, is calling on airlines and regulators to "change working conditions to reduce risk." The organization also plans to educate its members about the potential risks of both radiation exposure and interrupted sleep patterns.
If nothing else, it will at least raise awareness and may help with early cancer detection.
What Do YOU Think?
Were you aware of the the connection between circadian rhythm disruption and cancer? Does this increase in cancer risk affect you personally (or anyone you know)? Do you think the study's results might discourage people from entering a profession related to flying? Let us know in the comments below.