The side windows of the car do not protect the skin and eyes from the harmful ultraviolet (UV) radiation. The front windshields block the vast majority of UV rays from the sun.Prolonged exposure to UV rays can increase the risk of skin cancer and cataracts.
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.
The 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 were measured.
The researchers revealed that only 14 percent of the cars offered a high level of side-window UV-A protection.
This could lead to cataract in the left eye and skin cancer on the left side of people's faces, said Wachler.
"Automakers may wish to consider increasing the degree of UV-A protection in the side windows of automobiles," said Wachler.
Dr. Doris Day is a dermatologist and skin cancer expert at Lenox Hill Hospital in New York City, 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," said Day.
"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. UV-A also goes through glass, making it a potential issue for those who have daily commutes or spend extended periods in the car," she explained.
People should wear sunscreen that protects against both UV-A and UV-B rays. Drivers can purchase special window tint products that block 99% 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," said Day.
The study findings were published in JAMA Ophthalmology.