Sun Driving Skin Cancer

"For years, dermatologists have observed that patients in the U.S. often have more sun damage [which can lead to wrinkles, leathering, sagging, brown 'age' spots and even skin cancers] on the left side of their faces than on the right."
"Why? Research increasingly points to ultraviolet A [UVA] radiation penetrating through car windows."
"The UV exposure we receive driving a car especially adds up. In a U.S. study by Singer et al the researchers found asymmetric photodamage [sun-induced skin damage] on the face, with more brown pigment [colour] and deeper wrinkles on the left. The more time subjects spent driving a vehicle, the more severe their photodamage on the left side."
Dr. Susan Butler, dermatologist, co-author, Journal of the American Academy of Dermatology study

Karl-Josef Hildenbrand / AFP / Getty Images   The sun's rays can penetrate car windows, dermatologists say.

Vehicle windshield glass is laminated for safety reasons, giving the glass additional strength, a safety measure that ensures there are two sheets of glass with a sandwiched layer of thin plastic between them. Governments looking to enhance safety in the event of accidents with a view of reducing harm from flying glass shards in the event of vehicle collisions mandated this special windshield precaution. Not so however, with other glass windows in a vehicle.

The glass on the side and back windows was left as is, without tempered-glass [-hardened] since there was no need foreseen to have them treated in the same way as the windshield. Now, it seems that observation and research have led to the understanding that ultraviolent light beamed to the surface of the Earth which arrives in UVA and UVB form [UVB the more damaging; its short waves filtered out by car windows], sees the UVA rays penetrate those side windows.

The more complex glass with the light plastic sheeting in the centre is efficient at filtering out both UVA and UVB light; an unanticipated byproduct of serendipity in providing safety in crashes from flying glass, and at the same time offering a shield from the harmful sun rays that penetrate the side window glass. Which went a long way to explaining the puzzle that dermatologists struggled with; the presentation of patients with damaged skin, including skin cancer on people's left side of their faces and necks.

In Britain, Australia and Japan, it would be the right side of the face that is affected, for obvious reasons, reflecting the side of the road driven on. In a study that took place in 2010 of American subjects, it was noted that skin cancer on face and neck appeared on the left side in 52.6 percent of cases and on the right side in 47.4 percent of instances. A total of 890 patients were studied; these were people who had arrived for skin cancer surgery at a single medical clinic.

In Australia, the effect of right-side skin cancer has been named "cabbie cancer", to reflect drivers spending their working day in cars and their resulting susceptibility. It is unknown why it should be so, but studies reveal that the occurrence is more commonly seen in male than in female drivers. A California ophthalmologist who happens to also be a medical editor on the website WebMD, published an analysis of how much UV light penetrates side car windows.

Sun shining through a car's side window can be a skin cancer risk, dermatologists have said. Digital Vision, Getty Images

Dr. Brian Boxer Wachler studied the phenomenon in 29 vehicles manufactured by fifteen different companies, produced between 1990 and 2014 from the perspective of how eyes are affected by the influx of UV light penetration in vehicles. He found that the average side window succeeded in blocking out 71 percent of UV light, but also found that four of the cars studied blocked over 90 percent. His results saw publication recently in JAMA Opththalmology.

Until all car windows feature the same kind of three-ply protection, with two pieces of glass sandwiching a thin plastic sheet for the windshield, the recommendation is that alert people take to applying sunblock for UV protection, even while driving.

Zoran Bozecevic / Postmedia  Research has shown that ultraviolet A rays can penetrate through car windows.