(Reuters Health) - Car windows don't protect against harmful sun exposure, so it might be a good idea to wear sunglasses and sun block even while driving, a new study suggests. 
 
 While windshields blocked the vast majority of ultraviolet (UV) radiation from the sun, car door windows offered varying levels of protection from the rays that are tied to cataracts and skin aging. 
 
 "Some cars were as low as 50 percent blockage," said researcher Dr. Brian Boxer Wachler of the Boxer Wachler Vision Institute in Beverly Hill, California. 
 
 "Even cars that came with factory tint, there was no guarantee that would protect against UV rays," he told Reuters Health. 
 
 UV rays account for a small portion of the sun’s rays but are the most damaging to human skin. UV-A rays are the most common and penetrate most deeply, according to the Skin Cancer Foundation. 
 
 Because drivers in the U.S. have their left side exposed to sunlight, UV rays have been blamed for the increased number of cataracts and skin cancers that occur on the left side, Boxer Wachler writes in JAMA Ophthalmology. 
 
 UV rays can pass through clouds and glass. To see whether car windows are protective, Boxer Wachler took a UV-A light meter to a number of Los Angeles car dealers on a cloudless May day in 2014. 
 
 He tested 29 cars from 15 different manufacturers, made between 1990 and 2014. 
 
 On average, car windshields blocked about 96 percent of UV-A rays. The protection afforded by individual cars ranged from 95 to 98 percent. 
 
 But side door windows were far less dependable. The percentage of UV-A rays blocked varied from 44 percent to 96 percent. Only four of the 29 cars had windows that blocked more than 90 percent of UV-A rays. 
 
 "It had no correlation at all with the cost of the car, high-end car or low-end car," said Boxer Wachler. 
 
 Windshields are more protective than car door windows because they must be made of laminated glass to prevent shattering, writes Dr. Jayne Weiss in a commentary published with the study. Car door windows, however, are usually just tempered glass. 
 
 "Don’t assume because you are in an automobile and the window is closed that you're protected from UV light," she told Reuters Health. 
 
 "For the eyes, your best bet is to get sunglasses that block UV-A and UV-B light and wraparound the face," said Weiss, who directs the Louisiana State University Eye Center of Excellence in New Orleans. 
 
 Some of the car windows in this study let in enough UV-A rays to affect skin health, said Dr. Paul Nghiem, who heads the division of dermatology at the University of Washington in Seattle. 
 
 "Wearing long sleeve clothing, or sunscreen that is 'broad spectrum' would be extremely effective and seems indicated on long drives on sunny days," Nghiem, who was not involved with the new study, told Reuters Health by email. 
 
 People can also get clear UV filters added to their car windows to protect from the damaging rays, said Boxer Wachler. 
 
 SOURCE: bit.ly/1s2rp6t and bit.ly/1XnFyHu JAMA Ophthalmology, online May 12, 2016. ||||| THURSDAY, May 12, 2016 -- The front windshield of your car probably shields you from the sun's UV-A rays as you drive, but the same may not be true for side windows, a new study finds. 
 
 Experts have long known that prolonged exposure to ultraviolet A (UV-A) rays can raise the odds for skin cancer and cataracts. 
 
 And with the long hours many Americans drive each day, one researcher in California wondered how much sun protection today's cars might offer. 
 
 To find out, Dr. Brian Boxer Wachler, of the Boxer Wachler Vision Institute in Beverly Hills, analyzed the ultraviolet protection provided by the glass in 29 cars from 15 different automobile manufacturers. 
 
 Boxer Wachler measured levels of ambient UV-A radiation behind the front windshield and behind the driver's side window of the cars, which were produced between 1990 and 2014. 
 
 While windshield windows tended to offer good protection against UV-A, protection was lower and inconsistent for the side windows of cars, the study findings showed. 
 
 The study found front windshields blocked an average of 96 percent of UV-A rays, compared to 71 percent for side windows. 
 
 Overall, only 14 percent of the cars offered a high level of side-window UV-A protection, the research revealed. 
 
 This could contribute to a higher prevalence of left eye cataracts and skin cancer on the left side of people's faces, Boxer Wachler said. He believes that, based on the new data, "automakers may wish to consider increasing the degree of UV-A protection in the side windows of automobiles." 
 
 Dr. Doris Day is a dermatologist and skin cancer expert at Lenox Hill Hospital in New York City. She said UV-A rays can be especially dangerous to the skin. 
 
 "The World Health Organization has designated all wavelengths of ultraviolet radiation as known carcinogens," Day said. 
 
 "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," she explained. "UV-A also goes through glass, making it a potential issue for those who have daily commutes or spend extended periods in the car." 
 
 What to do? 
 
 Day recommends that people wear sunscreen that protects against both UV-A and UV-B rays. She also noted that drivers can purchase special window tint products that block 99 percent of UV rays. 
 
 "This is a great option for those who have older cars or cars that don't have the protection already built in," she said. 
 
 The study findings were published online May 12 in JAMA Ophthalmology. 
 
 The U.S. National Institutes of Health has more about the health effects of sunlight. 
 
 Copyright © 2016 HealthDay. All rights reserved. 
 
 ||||| Importance Ultraviolet A (UV-A) light is associated with the risks of cataract and skin cancer. 
 
 Objective To assess the level of UV-A light protection in the front windshields and side windows of automobiles. 
 
 Design In this cross-sectional study, 29 automobiles from 15 automobile manufacturers were analyzed. The outside ambient UV-A radiation, along with UV-A radiation behind the front windshield and behind the driver’s side window of all automobiles, was measured. The years of the automobiles ranged from 1990 to 2014, with an average year of 2010. The automobile dealerships were located in Los Angeles, California. 
 
 Main Outcomes and Measures Amount of UV-A blockage from windshields and side windows. The average percentage of front-windshield UV-A blockage was 96% (range, 95%-98% [95% CI, 95.7%-96.3%]) and was higher than the average percentage of side-window blockage, which was 71% (range, 44%-96% [95% CI, 66.4%-75.6%]). The difference between these average percentages is 25% (95% CI, 21%-30% [P < .001]). A high level of side-window UV-A blockage (>90%) was found in 4 of 29 automobiles (13.8%). 
 
 Conclusions and Relevance The level of front-windshield UV-A protection was consistently high among automobiles. The level of side-window UV-A protection was lower and highly variable. These results may in part explain the reported increased rates of cataract in left eyes and left-sided facial skin cancer. Automakers may wish to consider increasing the degree of UV-A protection in the side windows of automobiles.
– Ever gotten a sunburn while driving with the windows up? A new study explains why. Most vehicle windshields block harmful UV-A rays—the kind that raise the risk of everything from cataracts to skin cancer—but your side windows might not, says Brian Boxer Wachler of California's Boxer Wachler Vision Institute. He tested 29 cars made from 1990 to 2014 and found that front windshields blocked 96% of UV-A rays, reports HealthDay News. Side windows, however, blocked just 71% of rays on average. Some blocked as little as 44%. The gap in protection may be to blame for a greater occurrence of cataracts and skin cancers on US patients' left sides, Boxer Wachler says. "It had no correlation at all with the cost of the car," he adds. An expert at Louisiana State University says the difference might be that windshields are made of laminated glass to prevent shattering, while side windows are made of tempered glass, reports Reuters. "Don't assume because you are in an automobile and the window is closed that you're protected from UV light," she says. A dermatologist suggests wearing sunscreen and sunglasses while driving, and window tinting products are "a great option for those who have older cars or cars that don't have the protection already built in." (Time to count your moles.)