Motorists' health may be being put at risk by a lack of protection against ultraviolet A (UVA) light in some vehicles' side windows, new research suggests.
Researchers in the US looked at how much UVA light is getting through windscreens and side windows.
Their study included 29 cars, made by 15 different manufacturers between 1990 and 2014.
Its findings show that while all the windscreens blocked between 95% and 98% - an average of 96% - of UVA light, most of the side windows were a lot less effective.
The tested cars' side windows kept out between 44% and 96% of the UVA light beamed on to them, an average of only 71%, the research shows.
The study's author, Dr Brian Boxer Wachler, of California's Boxer Wachler Vision Institute, says the findings may partially explain why in the US - where cars are left-hand drive - there is a higher incidence of skin cancer and cataracts on the left-hand side of the body.
And he adds that the findings suggest car makers should increase the protection their side windows provide against damaging UVA light.
The study has been published in the JAMA Opthalmology medical journal.
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