Sun exposure from car windows dangerous: Study

Researchers who have studied sun exposure from car windows say it is more dangerous than uncomfortable.

The new analysis, published online in JAMA Ophthalmology, says the side windows of automobiles had inadequate protection from ultraviolet A (UV-A) light.

This kind of light was weaker than UV-B light, the type of light that caused sunburn but was suspected to be linked to more long-term health effects, like skin cancer and cataracts.

The levels of UV-A protection afforded by the windows of different automobile makes and models, were studied by the leader of the new analysis, Boxer Wachler, of the Boxer Wachler Vision Institute in Beverly Hill, California. He measured the UV-A radiation in 29 different vehicles from 15 different manufacturers, with car models ranging from 1990 to 2014, but on average, the cars were produced in 2010, making them fairly newer models.

Wachler found the average percentage of UV-A blockage in windshields was 96 per cent, but the same for side-windows was 71 per cent.

Only four of the 29 automobiles showed high levels of side-window UV-A blockage (greater than 90 per cent).

"Automakers may wish to consider increasing the degree of UV-A protection in the side windows of automobiles," Boxer Wachler wrote.

"Some cars were as low as 50 percent blockage," he said.

"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 only a small portion of solar radiation but were the most damaging to human skin. According to the Skin Cancer Foundation, UV-A rays were the most common and penetrated most deeply.

Because drivers in the US had their left side exposed to sunlight, UV rays had been blamed for the increased number of cataracts and skin cancers that occured on the left side, Boxer Wachler wrote in JAMA Ophthalmology.

"Don't assume because you are in an automobile and the window is closed that you're protected from UV light," Dr Jayne Weiss  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.