Icarus-Like: Pilots, Crew Have Double the Rate of Melanoma

Nick Mulcahy

September 03, 2014

As in the mythical story of Icarus, human beings in the modern world who fly too close to the sun have a price to pay, new research suggests.

Airline pilots and cabin crews have twice the incidence of melanoma as the general population, according to the largest meta-analysis to date on the subject, which was published online September 3 in JAMA Dermatology.

The standardized incidence ratio of melanoma for any flight-based occupation was 2.21 (P < .001).

Furthermore, melanoma was more deadly in these professionals, who had a disease-related mortality rate 42% greater than that of more regularly earthbound beings.

Specifically, the standardized mortality ratio for any flight-based occupation was 1.42 (P = .02).

"Further research on the mechanisms [of harm] and optimal occupational protection is needed," conclude the researchers, led by Martina Sanlorenzo, MD, a research fellow in the Department of Dermatology at the University of California, San Francisco.

They suspect that the increase in melanoma risk seen in airline pilots and cabin crews comes from exposure to ultraviolet (UV) light, which becomes more intense the higher a plane flies. "At 9000 meters [30,000 feet], where most commercial aircraft fly, the UV level is approximately twice that of the ground," the researchers report.

Remarkably, UV light exposure is "not a well-recognized occupational risk factor" for flight crews, they note. In contrast, ionizing radiation is a well-known risk, and levels in airline crews are regularly monitored.

This study provides no details on the clinical aspects of the melanomas.

 
It would be interesting to see the anatomic distribution of skin cancers in the crew.
 

"It would be interesting to see the anatomic distribution of skin cancers in the crew, because only hands and face should be exposed to UV passing through the windows," said Steven Wang, MD, director of dermatologic surgery and dermatology at the Memorial Sloan Kettering Cancer Center in Basking Ridge, New Jersey, who was not involved in the study.

Frequent flier passengers are probably not at an increased risk, he said in an email to Medscape Medical News. But for the worried, pulling down the window shade and sitting in an aisle seat are protective strategies, added Dr. Wang, who is the author of Beating Melanoma: A 5-Step Survival Guide.

The meta-analysis examined 19 studies (15 with data on pilots; 4 with data on cabin crews). Data from the studies, which involved more than 266,000 participants, were collected from 1943 to 2008 in more than 11 countries.

The researchers conducted separate analyses for pilots and for cabin crews (which include flight attendants).

They found that pilots were at greater risk for melanoma than the cabin crew. The standardized incidence ratio for pilots was 2.22 (= .001) but for the cabin crew was 2.09 (P = .45).

In fact, pilots and crews would have more than double the annual number of new melanomas per year, which is 21.3 per 100,000 individuals in the general population.

Pilots as a group were also at greater risk for mortality, and had a higher mortality ratio than cabin crews (1.83 vs 0.90).

UVA Radiation and Glass Might Be the Problems

The researchers discuss the technicalities of the types of UV radiation and windshields.

They cite measurements of UV radiation that passes through the windshields of a variety of aircraft — large (e.g., Boeing737 and Airbus A320) and small (e.g., Cessna 182) — from a 2007 report by the US Federal Aviation Administration.

The transmission of UVB is less than 1% for both plastic and glass windshields.

However, UVA is a different story, especially in airplanes with glass windows. "While plastic materials blocked almost all UVA radiation, 54% of it came through glass," Dr. Sanlorenzo and colleagues report.

This study was supported National Cancer Institute, the Melanoma Research Alliance, the Dermatology Foundation Career Development Award, and the National Center for Advancing Translational Sciences. The authors have disclosed no relevant financial relationships.

JAMA Dermatol. Published online September 3, 2014. Abstract

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