London, Dec 18 (IANS): Aircraft pilots are at considerable risk of skin cancer, being exposed to ultra violet (UV) rays of the sun, which aircraft windshields do not completely block, according to a new study.

According to researchers, pilots flying for an hour at an altitude of 30,000 feet are exposed to the same amount of solar radiation as during 20 minutes on a tanning bed, the Daily Mail reported Wednesday.

Writing in the journal Jama Dermatology, the authors, led by Martina Sanlorenzo from the University of California, San Francisco, also noted: “These (exposure) levels could be significantly higher when flying over thick cloud layers and snow fields, which could reflect up to 85 percent of UV radiation.”

The study found that airplane windshields, made of polycarbonate plastic, or multilayer composite glass, do not completely block UV-A radiation.

The researchers concluded that compared with the general population, airline pilots and flight crews may be twice as much at the risk of melanoma (malignant skin cancer).

UV-A radiation can cause DNA damage in cells and its role in melanoma -- a lethal type of skin cancer -- is well known, according to the report.

Aircrews were also found to face an increased risk of exposure to cosmic rays -- X-rays, gamma rays and subatomic particles -- from space.

The radiation in cockpits was measured at the pilot's seat of a general turboprop airplane, through the acrylic plastic windshield, at ground level and at various altitudes above the sea level.

Sun exposures were measured in San Jose, California, and in Las Vegas around midday in the month of April.

The researchers then compared them with measurements taken on tanning beds.

While short-wave UV-B radiation cannot easily penetrate glass and plastic windows, long-wave UV-A is much more likely to get through, though both kinds of UV rays can cause skin ageing and cancer.