The authors of the study believe that this could be due to increased exposure to ultraviolet (UV) and cosmic radiation related to high altitudes. Although officials routinely monitor levels of exposure to ionizing radiation, UV exposure is not usually recognized as an occupational hazard for pilots and cabin crew.
UV is, however, recognized as a major risk factor for the development of melanomas. UV is known to damage the DNA of skin cells, and when the DNA that controls the growth of skin cells is damaged, skin cancer can develop.
Skin cancer is the most prevalent form of cancer in the US, and although melanoma accounts for less than 2% of skin cancers, it is known to cause the majority of skin cancer deaths.
According to the American Cancer Society (ACS), approximately 76,100 new melanomas will be diagnosed during 2014. The ACS estimate that around 9,710 people are expected to die from the condition in the US this year.
Medical literature study
Melanoma rates in the US are consistently rising, and as several studies have suggested that there may be a raised incidence of melanoma among pilots and cabin crew, a team of researchers – led by Dr. Martina Sanlorenzo of the University of California – conducted a meta-analysis of 19 studies, involving over 266,000 participants.
The researchers found that the overall standardized incidence rate (SIR) of melanoma for flight-based occupations was 2.21. Specifically, pilots had a SIR of 2.22 and cabin crew had a SIR of 2.09. This result means that pilots and aircraft have twice the incidence of melanoma compared with the general population.
The authors acknowledge that their work is limited in that it utilizes observational and predominantly retrospective studies within its review. The authors were unable to adjust the findings of the studies used for potential confounders – other variables that may have influenced the results.
However, within the literature review, one study did not find any significant difference in the prevalence of melanoma risk factors – such as a history of sunburn or sunbed usage – between aircraft crew and the general population.
Other studies noted a correlation between increased incidence of melanoma within flight crew and increased numbers of flight hours, suggesting that occupational exposure to UV has more of an influence on melanoma incidence than leisure-activity exposure.
Increased UV exposure
The authors believe that an increased exposure to UV radiation for flight crew could explain their findings. They state that airplane windshields and cabin windows “seem to minimally block UVA radiation,” and that “at 9000 m, where most commercial aircraft fly, the UV level is approximately twice that of the ground.”
“Therefore, the cumulative UV exposure for pilots and cabin crew is still of concern, and the higher risk of melanoma evident in our meta-analysis could be due to greater occupation-related exposure to UVA radiation.”
The meta-analysis was partly funded by the National Cancer Institute of the National Institutes of Health and is published in JAMA Dermatology. These findings may have implications for the occupational health and protection for this part of the workforce.
