Prop plane pilots exposed to tanning-bed radiation levels

Reuters Health - Flying for an hour at 30,000 feet exposes pilots to as much ultraviolet radiation as they would get from 20 minutes in a tanning bed, according to a new study.

“We performed UV measurement at the pilot seats inside a general aviation plane,” measuring the cosmic radiation coming through the windshield, said Dr. Martina Sanlorenzo who coauthored the new research letter.

Sanlorenzo, of the dermatology department at Mount Zion Cancer Research Center at the University of California, San Francisco, and her team recently published an analysis of past research concluding that pilots and cabin crew have approximately twice the incidence of melanoma compared to the general population (see Reuters Health article of September 14, 2014 here:

“Our meta-analysis showed an increased risk of melanoma in cabin crew too,” including flight attendants, Sanlorenzo said. “However, the role of UV radiation in melanoma risk could be more important for pilots, who are seated in the cockpits for most of the time, and therefore have a greater exposure.”

For the new study, the researchers placed UV index meters in the pilot seat of a small turboprop light business and utility airplane with six passenger seats and a plastic windshield.

They took radiation measurements at ground level and at regular altitude increments in flight, and took readings in two locations, San Jose, California and Las Vegas, Nevada.

Then they took the same UV measurements inside a tanning bed.

According to their measurements, published in JAMA Dermatology, the aircraft windshield blocked UV-B but not UV-A radiation.

UV-A is the most abundant source of solar radiation at the earth’s surface and penetrates beyond the top layer of human skin, increasing the risk for skin cancer, according to the Centers for Disease Control and Prevention. UV-B can cause some forms of skin cancer as well, but does not penetrate the skin as deeply.

The researchers calculated that 56 minutes in the pilot’s seat of the plane at 30,000 feet resulted in the same carcinogenic-effective dose of UV-A radiation as a 20-minute tanning session.

“Pilots and cabin crew should be aware of the higher risk of melanoma,” Sanlorenzo said. “They should know that windshields are not enough to protect their work environment from UV radiation.”

Aircraft windshields should be improved to block more UV-A radiation, she said.

“We strongly recommend the use of sunscreens and periodical skin check examinations for pilots and cabin crew,” she added.

There is great variation in how much radiation exposure pilots will have, depending on altitude, latitude, cloud cover, time of year and other factors, said Hajo Zeeb, head of the prevention and evaluation department at Leibniz Institute for Prevention Research and Epidemiology in Bremen, Germany.

Zeeb, who was not involved in the new research, has studied flight crew radiation exposure in the past.

There is less exposure in the passenger area of the plane and no exposure at night, he said.

“This is one small study, and I guess more will follow to see how different window types allow UV-A transmission, and what would be the best ways to also block UV-A more efficiently,” Zeeb told Reuters Health by email. “Pilots should be made aware of the increased melanoma risk in their professional group, but the link to UV-A transmitted through windows is far from clear as it currently stands.”

There could be other explanations for the increased rate of melanoma among pilots.

“It is true, that pilots have increased incidence of skin cancer,” said Katja Koto, a researcher at STUK Radiation and Nuclear Safety Authority in Finland.

If it were due to the UV-exposure in cockpit, the excess would probably be on the face and lower arm area, she said.

“Also cabin crew have increased incidence of skin cancer but there is no UV-exposure in the cabin,” Koto told Reuters Health by email. “These facts might support the idea that pilots and cabin crew are exposed to excess amount of UV on their free time, which causes the excesses of their skin cancer.”

A study of Nordic airline pilots found very similar incidence rates of melanoma of the head and neck, limbs and trunk, said Dr. P.H. Gaël Hammer, an epidemiologist at the Laboratoire National de Santé in Luxembourg.

“And since the trunk is usually covered and well protected in the cockpit, this suggests that exposures outside the cockpit are the most likely cause of these cancers,” Hammer said.

SOURCE: JAMA Dermatology, online December 17, 2014.