new study has found that American flight attendants are more likely than the general population to develop several cancers, including breast cancer, melanoma and non-melanoma skin cancer.
According to Alice Park of Time, the new report, published recently in the journal Environmental Health, is based on data collected by the Harvard Flight Attendant Health Study (FAHS), which was launched in 2007. The researchers behind the study sought to shed light on an understudied occupational group. Though flight attendants are frequently exposed to a number of possible or probable cancer-causing factors—like sleep disruptions, radiation, and pesticides and other chemicals in the cabin—the long-term effects of this exposure have not been well documented.
Between 2014 and 2015, researchers studied 5,300 flight attendants through surveys that were disseminated online, via mail and in person at airports. The surveys asked respondents about flight schedules and cancer diagnoses. The researchers then compared the responses to the health status of 2,729 non-flight attendant adults with similar socioeconomic backgrounds, using data from the National Health and Nutrition Examination Survey (NHANES), which surveys around 5,000 Americans each year.
The comparison revealed higher rates of uterine, cervical, breast, gastrointestinal, thyroid and melanoma cancers among flight attendants. The disparity was especially pronounced with breast, melanoma and non-melanoma cancers. Flight attendants had more than double the risk of developing melanoma, and more than quadruple the risk of developing non-melanoma cancers. They were also 51 percent more likely to develop breast cancer than the general population.
To the researchers’ surprise, they found a higher risk of breast cancer in female flight attendants with three or more children; typically, a woman’s risk of breast cancer decreases as she has more children.
“This study is the first to show higher prevalences of all cancers studied, and significantly higher prevalences of non-melanoma skin cancer compared to a similarly matched U.S. sample population,” lead study author Eileen McNeely of the Harvard T.H. Chan School of Public Health tells Lisa Rapaport of Reuters. McNeely also notes that “[n]on-melanoma skin cancer among women increased with more years on the job, suggesting a work-related association.”
The study suggests a number of factors that could be contributing to higher cancer risks among flight attendants. As Jen Christensen of CNN points out, flight attendants are often exposed to known or possible carcinogens like pesticides, jet fuel and fire retardants. Because they often cross time zones, flight attendants also could also be dealing with disrupted circadian rhythms, and irregular sleep patterns have been shown to increase the risk of cancer development. Poor air quality inside the cabin is also a concern.
Another risk factor could be flight attendants’ exposure to cosmic ionizing radiation, high-energy particles from outer space that collide with particles in the Earth’s atmosphere, “causing a chain reaction of particle decays,” according to NASA. Humans are protected from cosmic radiation on the ground, but there are increased chances of exposure at high altitudes. The WHO has found that exposure to ionizing radiation can lead to increased risk of cancer in humans; the CDC says it is investigating specific links between cosmic ionizing radiation and cancer.
The European Union requires that flight attendants’ schedules be arranged so that they do not exceed a certain amount of ionizing radiation each year. But there are no official dose limits for flight crew in the United States.
Study coauthor Irina Mordukhovich, a research associate at the Harvard T. H. Chan School of Public Health, tells Park of Time that going forward, the study’s results will need to be replicated to confirm possible risks. But she hopes that the current study calls attention to the potentially grave health hazards that flight attendants face on the job.
“We have known carcinogens that flight crews are exposed to,” she says, “and we’re hoping that this study allows people to start thinking about what should be done to implement protections.”