Cars' Side Windows Lack UV Protection and Contribute to Skin Cancer, Cataracts

The approaching summer months often call for long drives with the windows and top rolled down. Feeling the gentle breeze might be fun, but the sun’s rays beating down through the side window can be uncomfortable and even harmful to one’s health.

According to new research published in JAMA Ophthalmology, the side windows of automobiles have inadequate protection from ultraviolet A (UV-A) light.

Although this type of light is weaker than UV-B light (the type that causes sunburns), it is thought to be associated to more long-term negative health affects like skin cancer and cataracts.

Previous research had reported higher rates of cataracts in left eyes and that skin cancer developed more often on the left side of the body — both areas easily exposed to UV-A while driving.

By law, windshields are made with laminated glass to minimize injury when shattered. Also, extra-thick glass is added to make the windshields extra protective from the sun.

Side windows are not required to meet the same standards of protection.

Less regulated, side windows are also produced to be much thinner and do not have any plastic support. An easy solution for sun protection could be adding custom tints, but this is an illegal practice in several US states.

Nonetheless, the levels of UV-A protection between the windows of different automobile makes and models were previously unknown in the US, since they aren’t regulated.

As such, Brian Boxer Wachler, MD, the study’s lead author, measured the UV-A radiation in 29 different vehicles from 15 different manufacturers. The model years of the cars he used ranged from 1990 to 2014, but the mean production year was 2010 so he could use newer models.

The study results showed the average percentage of UV-A blockage in windshields was 96%, but the side window blockage was only 71%.

Because high levels (more than 90%) of side window UV-A blockage were only found in four of the 29 vehicles, Wachler suggested, “Automakers may wish to consider increasing the degree of UV-A protection in the side of automobiles.”

While there is no easy fix to this almost daily activity, physicians should remind patients to take personal measures like covering up, applying sunscreen above SPF 15 at least 30 minutes before driving, or wearing sunglasses.