I read on http://www.nytimes.com/2012/08/12/travel/faq-frequent-airline-questions.html?mcubz=1:
“Pilots do have a higher incidence of skin cancer,” said Dr. James M. Spencer, a member of the board of directors of the American Academy of Dermatology and an expert in skin cancer treatment and cosmetic surgery in St. Petersburg, Fla., referring to several studies about skin cancers among airline pilots.
Why exactly more pilots have skin cancer is not known (for instance it could be from cosmic radiation, changing circadian rhythms or from, say, spending a lot of time outdoors in the places they fly to). And to complicate matters, no one has done a scientific comparison of instances of skin cancer in frequent fliers versus non-frequent fliers, Dr. Spencer said.
The article was written in 2012. Since then, have we understood why airplane pilots are more likely to have skin cancer?