by Dr. Bill Blank, M.D.
A recent report in a dermatology journal noted a study that revealed that an airline pilot is exposed to as much Ultraviolet A (UVA) radiation during a 56-minute flight at 30,000 feet as he would receive in a 20-minute session in a tanning booth. That is interesting, but why would anyone care? For our airline and corporate pilot readers, I thought I would look into it. What I have discovered will be of use to all of us.
UV radiation is harmful to the skin. The exposure is cumulative. The longer we are exposed and the higher the dosage, the more likely there will be damage.
I suspect that many of our readers are of northern European origin and have fair complexions. This type of skin is much more susceptible to UV damage. Darker skin is, to some extent, protective. By the time we are older, the damage has accumulated, and problems start to appear.
What type of damage am I talking about? Skin cancer; basal cell carcinoma, squamous cell carcinoma, and malignant melanomas, along with wrinkling and actinic keratosis, are the result.
Basal cells are not invasive. Squamous cells are invasive and can spread. Malignant melanomas are, by far, the most serious. They are sometimes fatal in spite of treatment.
There are two types of UV radiation we are concerned with, UVA and UVB. UVA has a longer wavelength. It penetrates more deeply into the skin. It causes cellular mutations, which lead to the various cancers I have talked about. It is present throughout daylight hours. UVB is stronger between 10 A.M. and 4 P.M. during summer months. It causes sunburn.
The study was done because airline pilots seem to be at a higher risk for developing malignant melanomas, about twice the risk of the general population. The atmosphere filters out a lot of the UV radiation by the time it gets to the earth’s surface. The exposure at 30,000 feet is about twice that at the surface.
Aircraft windshields are designed to filter out some of the radiation. Airline and corporate aircraft windshields are made of either polycarbonate or multi-layer composite glass. Both do a good job of preventing the transmission of UVB, about 99% of which gets blocked. They don’t do such a good job on UVA, up to 50% is, in some cases, transmitted. Remember, UVA causes most of the damage.
During the study, the authors measured the UVA and B radiation transmission in aircraft, such as the TBM 850, MD88, A-320, Boeing 727 and 737 at the surface and at altitude in two different locations. They made the same measurements in a tanning booth, which produces UVA. This permitted them to conclude that 20 minutes in a tanning booth was equivalent to 56 minutes at 30,000 feet.
What do we do with all of this? The most important thing is awareness. The longer the exposure, the more likely there will be problems. Dermatologists are quite concerned about the sun culture and the proliferation of tanning booths. They are seeing an increase in problems, especially of melanomas, even in young people.
Now we get to the key question, prevention. Should high altitude pilots wear sunscreen when they fly? I don’t know for sure. Will it help enough? I don’t think anyone knows.
Be aware that sunscreens are rated by SPF, Sun Protection Factor. An SPF of 15 means that if you would get a sunburn in 20 minutes without the sunscreen, it would take 300 minutes with it.
SPF only considers UVB, the sunburn producer, and doesn’t rate UVA protection.
If you use sunscreen, be sure to pick one, which is wide spectrum and tries to protect against both.
Don’t forget, almost all of us should be wearing sunscreen at fly-ins and air shows. In fact, sun protection clothing and hats are also a good idea.
See you at EAA AirVenture Oshkosh 2015!
EDITOR’S NOTE: William A. Blank is a physician in La Crosse, Wisconsin, and has been an Aviation Medical Examiner (AME) since 1978, and a Senior AME since 1985. Blank is a retired Ophthalmologist, but still gives some of the ophthalmology lectures at AME renewal seminars. Flying-wise, Blank holds an Airline Transport Pilot Certificate and has 5300 hours. He is a Certified Instrument Flight Instructor (CFII), and has given over 1200 hours of aerobatic instruction. In addition, Blank was an airshow performer through the 2014 season, and held a Statement of Aerobatic Competency (SAC) since 1987.