Car Windows Don’t Shield Skin, Eyes From UV-A Rays

Even if your car windows are closed and tinted, they may fail to protect your skin or eyes from the sun’s harmful ultraviolet rays.

New research, published online Thursday in the journal JAMA Ophthalmology, shows that side windows offer significantly less protection from UV-A rays than windshields provide.

The research was conducted by eye surgeon Dr. Brian S. Boxer Wachler of the Boxer Wachler Vision Institute in Beverly Hills, California.

The study involved 29 automobiles from 15 manufacturers. The vehicles’ years ranged from 1990 to 2014, with 2010 being the average year.

Boxer Wachler analyzed these vehicles by measuring the level of UV-A radiation:

• Outside
• Behind the front windshield
• Behind the driver’s side window

Here’s what he found:

• The front windshields blocked 95 percent to 98 percent of UV-A radiation, with 96 percent being the average amount blocked.
• The side windows blocked 44 percent to 96 percent of UV-A radiation, with 71 percent being the average amount blocked.
• Only four of the 29 vehicles’ side windows (14 percent) blocked what the study considered “a high level” (90 percent of more) of UV-A radiation.

Windshields offer greater protection because, unlike side windows, they are made from two planes of glass, the study explains. Between a windshield’s glass planes is a layer of plastic to make the windshield shatterproof, and most of the UV-A protection is in that plastic layer.

The study concludes:

These results may in part explain the reported increased rates of cataract in left eyes and left-sided facial skin cancer.

Cumulative UV-A exposure is “a significant risk factor for skin cancer,” according to the study.

Multiple studies have found that skin cancer is more common on the left side of the face in countries where cars are driven on the right side of the road. A study from Australia, where cars are driven on the left, found that skin cancers are more common on the right side of the face.

Dr. Doris Day, a dermatologist and skin cancer expert at Lenox Hill Hospital in New York City, tells HealthDay that UV-A rays can be especially dangerous:

“While UV-B is a shorter wavelength of light and is blocked by glass, UV-A is longer and goes deeper into the skin — causing both skin cancer and premature aging as it breaks down collagen. UV-A also goes through glass, making it a potential issue for those who have daily commutes or spend extended periods in the car.”

Do you take any steps to protect yourself from ultraviolet light on a daily basis? Let us know below or on Facebook.