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Your Car Side Window May Not Protect You Well From Skin Cancer

July 23, 2016

Skin cancer is the most common type of cancer in the U.S., and if you think slathering on sunscreen when you’re sitting outdoors is all the protection you need, you are mistaken.

A new study indicates that the sun’s UVA rays may be able to penetrate your car’s side windows. The study, conducted by Dr. Brian Boxer Wachler of the Boxer Wachler Vision Institute in Beverly Hills, Calif., compared levels of UVA radiation through the front windshield and the driver’s side window. Wachler tested the sun protection provided by the car glass — manufactured between 1990 and 2014 —  in 29 cars from 15 different car companies. 

The results suggest what we’ve long known — that the front windshield provides adequate protection from UVA rays, which causes the skin to age prematurely, develop sun spots and wrinkles and elevates your risk for skin cancer. However, the results also showed that side windows don’t provide as much protection from UVA rays. The front windshield blocked an average of 96 percent of UVA rays, while side windows blocked 71 percent of these rays. Only 14 percent of car windows provide enough protection from UVA radiation, the study showed. 

Car window glass traditionally blocks UVB rays, which have shorter wavelengths and can cause sunburn but do not penetrate the skin as deeply as UVA rays. UVA rays have a longer wavelength and can cause sun damage even when you’re indoors — if you sit by an open window all day, for example.

So what can you do if you spend hours in the car every day commuting? Use a broad spectrum sunscreen that protects against both UVA and UVB rays (many sunscreens only protect against UVB rays, so read the label). Another option? Tint your windows to block even more of the sun’s rays. However, check with your local DMV before you visit a car detailer, as many states have laws about how dark you can tint your windows.

Also don’t forget to protect your eyes from UVA radiation while driving. Always wear sunglasses, prescription-strength UV lenses or use the visor in your car to block the sun’s rays. If your eyes aren’t protected, they can directly absorb UVA light and prolonged exposure can lead to cataracts, macular degeneration, blurred vision and possible vision loss.

Taking these steps will help to reduce your risk of sun damage and skin cancer, whether you’re indoors or out.