Don't count on your car for protection--

At least not from damaging UV-A light. 

Few cars offer a high level of sun protection from side windows.  

 Skin cancers and eye cataracts appear with increased frequency on patients' left sides.  One doctor suspected a reason.   Dr. Brian Boxer of the Boxer Wachler Vision Institute in Beverly Hills did the research.  His findings were published  last week, online, in JAMA Ophthalmology.

Dr.  Boxer Wachler analyzed the ultraviolet protection provided by the glass in 29 cars from 15 different automobile manufacturers.  He 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.  Altogether, just “14 percent of the cars offered a high level of side-window UV-A protection.” 

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. 

Why would this be the case?   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."  It is the sheet of plastic laminate in the windshield that offers protection.  Unfortunately, glass that is just tempered, even if tinted, doesn't do the same.   

"For the eyes, your best bet is to get sunglasses that block UV-A and UV-B light and wrap around the face," said  Dr.  Weiss, who directs the Louisiana State University Eye Center of Excellence in New Orleans.

Obviously, and unfortunately,  long sleeves and sunscreen are needed while driving even if you are behind closed doors in the car with  the side windows up.    Hopefully, manufacturers will begin to address this problem with greater frequency.