Car windows are designed to do many things. By government standards, they must let in as much light as possible to help the driver see, shatter in tiny pieces rather than shards to avoid hurting occupants, and absorb impacts. But do your car’s windows protect you from UV rays? They’re certainly not designed with it in mind, so let’s find out.
Ultraviolet Ray Basics
There are two main kinds of UV radiation: UV-B and UV-A. The former is the kind you shouldn’t worry about—it tans or reddens the skin, which isn’t ideal but doesn’t cause any actual harm. On the other hand, UV-A radiation is the type that can cause long-term skin damage and lead to cancer, and should be avoided whenever possible.
Windshield and Sunroof Protection
Windshields are made of laminated glass, featuring a thin 0.8-mm piece of stretchy plastic sandwiched by two layers of 2.1-mm glass. Because plastic is naturally good at absorbing UV rays, windshields tend to be good at preventing sunburns.
According to Pete Dishart of Pittsburgh Glass Works in Pennsylvania—which supplies glass to automakers like Toyota, BMW, Hyundai, Mercedes-Benz, and GM—windshields absorb 100% of UV-B rays and approximately 98% of UV-A rays.
In other words, windshields are as effective at protecting occupants from the sun as some of the strongest sunscreens you can buy. Sunroofs block about 90% of UV rays, which is not quite as good but still adequate.
Side and Rear Window Protection
Unfortunately, side and rear window protection isn’t nearly as good. Researchers from the Boxer Wachler Vision Institute in Beverly Hills found that UV-A protection from the side windows of 29 cars varied between 44% and 96%; the average was around 71% and only four cars provided adequate protection (more than 90%). That’s no better than applying sunscreen with an SPF of 15 and leaves your skin thoroughly exposed, especially on longer drives.
If you commute to work every day, you’re probably absorbing a lot more UV-A light than you might have thought. In fact, a 2007 study at the St. Louis University School of Medicine found that people who spend more hours per week driving have a higher chance of getting left-side skin cancer in the head, neck, arms, and hands.
What Can We Do?
Some automakers, like Hyundai and Kia, are already using higher-SPF glass not only because it protects against UV rays but also because it helps cool down the car, and thus improves fuel efficiency by reducing the use of air conditioning. Others are also beginning to introduce laminated glass on all car windows because it lowers wind noise.
However, there’s no guarantee that an industry-wide shift toward UV-absorbing glass is going to happen any time soon. If you drive frequently, your best bet at the moment is to start wearing sunscreen on your exposed skin and explore the possibility of window tinting and aftermarket films.
Sources: Medical Daily, NBC News, SkinCancer
Kurt Verlin was born in France and lives in the United States. Throughout his life he was always told French was the language of romance, but it was English he fell in love with. He likes cats, music, cars, 30 Rock, Formula 1, and pretending to be a race car driver in simulators; but most of all, he just likes to write about it all. See more articles by Kurt.