People who work on U.S. flight crews have higher rates of certain types of cancer, according to a new study out of Harvard.

Not only are flight crews more likely to be diagnosed with cancer, the longer they work in the field, the higher the risk of developing it becomes, researchers from the Harvard T. H. Chan School of Public Health wrote in the Environmental Health journal.

More than 5,000 flight attendants participated in the study. About 15 percent of the participants reported ever having been diagnosed with cancer, a higher prevalence than the general population.

“Consistent with previous studies, we report a higher lifetime prevalence of breast, melanoma and non-melanoma skin cancers among flight crew relative to the general population,” Dr. Irina Mordukhovich, corresponding author of the study, said in a statement. “This is striking given the low rates of overweight and smoking in this occupational group.”

While the job itself may not inherently breed higher risks of cancer, working in a plane involves “exposures to known and probable carcinogens including cosmic ionizing radiation, circadian rhythm disruption, and possible chemical contaminants in the aircraft cabin,” according to the study.

Each five-year increase spent working as a flight attendant increased risk of non-melanoma skin cancer among women and higher risk of breast cancer in women who had never had children or those who had had three or more. Job tenure didn’t have any visible correlation with thyroid cancer or melanoma, however those who worked in planes before smoking was banned in 1998 reported higher rates of melanoma and non-melanoma skin cancer.

Researchers hope that the study’s conclusions can be used to “minimize the adverse exposures and cancers common among cabin crew.”