Can you get sunburned through a window?

By Sarah B. Weir 

(Photo: Getty Images)

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While most people can not get sunburned through a window, that doesn't mean that glass protects you from all of the harmful effects of the sun. Glass commonly blocks UVB rays, but untreated windowsdo not shield you from dangerous UVA rays.

Despite many health organizations' efforts to clarify the difference between UVB and UVA rays, people are still confused and believe they're safe and healthy as long as they don't get a burn or stay outdoors too long.

UVB and UVA rays: What's the difference?

UVB rays cause sunburn. It's easy to tell if you've been overexposed by the redness and pain.  The effects of UVA rays are more insidious and cause damage over the long term.

They don't impact the skin right away -- instead, after years of exposure, UVA rays increase signs of visible aging such as wrinkles and brown spots, and can also lead to skin cancer, including melanoma, the most deadly form. While UVB rays can also lead to cancer and photo-aging, they diminish during the winter. UVA rays are present, and harmful, year-round.

Drivers are particularly vulnerable

UVA rays can penetrate a typical window -- whether it's in your home, office, or school. Because car windows are located so close to the body, they pose a particular risk.

Car windshields are coated with a protective film that blocks UVA rays, but often, side windows are not. At least two studies have shown that commuters and others who spend a lot of time in the car have an increased risk of developing skin cancer on the left side of their bodies -- the side that gets the most exposure through the car windows for U.S. drivers.

In the first study, led by Dr. Scott Fosko at the St. Louis University School of Medicine and published in 2010, researchers combed through the records of more than 1,000 patients treated by a local skin cancer clinic. They discovered that the people who spent the most time driving were more likely to develop cancers on their left sides, especially on their faces, necks, arms, and hands -- areas exposed to sunlight through the side window. According to Dr. Fosko, "It is an exposure that the public most likely doesn't consider and should be aware of and take precautions with."

Another study, noted in the Journal of the American Academy of Dermatology in January 2011, examined even more data gathered from the National Cancer Institute and came to the same conclusion.

Dr. Fosko suggests that if you are regularly sitting beside a sunny window indoors, you should also protect yourself from exposure to UVA rays. Although the chronic effects take several years to develop, he warns, "The damage starts early."

How to protect yourself:

• Consider having your car's side and rear windows tinted or laminated with a UV-filtering material such as UV film.
• Roll up your car windows -- open windows let in even more UVA rays as well as UVB rays.
• Drive wearing long sleeves.
• Install a rear window and passenger side window sun shades to protect your children.
• Consider using UV film on home or workplace windows. It is readily available at building supply stores. In addition to blocking harmful rays, it also helps prevent curtain and upholstery fabrics from fading.
• Wear a broad-spectrum sunscreen that blocks both UVB and UVA rays year-round.
• Wear sunglasses with 100% UVA and UVB protection when driving or outdoors. The lens and retina of the eyes are extremely sensitive to sun damage.