A 2012 study showed just how extreme these effects can get with a photo of a 69-year-old truck driver who had been behind the wheel of a big rig for the last 28 years. On the right side, he showed some signs of aging, but the left side was shocking with deep wrinkles and sagging skin. The picture looked more like special effects makeup than an actual person.
While the effects aren't as demonstrable, the same thing happens to normal drivers too. According to a Cars.com story, a 2004 study showed that all cancer is somewhat more likely on the left side at 52.6 percent versus 47.4 percent on the right. Far more striking, the cancer malignant melanoma showed up on the left 74 percent of the time. Those numbers have been backed up by other research around the world.
If you are really concerned about sun exposure, doctors recommend wearing a hat, sunglasses and sunscreen. Your car's glass helps a little. Windshields generally offer around 50 SPF protection and about 16 SPF from the side windows, according to Cars.com. Although those numbers can vary. There are also clear films that can be applied to further reduce these levels, and tinted glass can help too.