Car windows are designed to protect you during a crash but they won’t necessarily protect you from the sun. Sun protection can vary depending on the automaker and even by the windows within a vehicle.Automotive glass must meet many standards - it must transmit light yet shatter into tiny cubes instead of dangerous shards , but what about protection from the sun? Windscreens are great at protecting you from the sun’s harmful rays but side glass is not.Windscreens offer the most sun protection, according to Pete Dishart, who leads product development at Pittsburgh Glass Works in Pennsylvania, USA. The company supplies glass to a host of automakers.ABSORBING HARMFUL UVAccording to the company, a windscreen must be made of laminated glass, which means they’re formed from three parts: two 2.1mm layers of glass sandwiching an 0.8mm piece of stretchable plastic. The glass is designed to shatter easily if something (e.g the driver’s head or an animal) comes into contact with it. Should that happen, the plastic stretches to cushion the impact.Plastic layers absorb most of of the sun’s ultraviolet (UV) rays. Dishart said plastic and can be made with extra UV absorbers to protect even more and that windshields “can absorb 100% UV rays.” It can also have a sun protection factor (SPF) of 50 or more, the equivalent of some of the most effective sunscreens.a sunroofs, too, often contains a layer that can block around 90% of ultra-violet.SIDE-WINDOW CANCER RISK?That’s all well and good for protecting drivers from the front and above but what about rays directed from side and rear? Sadly, that glass offers varying degrees of SPF depending on the make and model of vehicle. They are usually made of cheaper tempered (heat-treated) glass that's 4mm thick a plastic layer. Unless tinted, they usually absorb only 65% of UV, PGW said.Dishart again: “That gives them an SPF of around 16, the same as the lowest grades of sunscreen.”An SPF of 16 might be sufficient for short trips but several studies indicate a correlation between skin cancer and sun exposure while driving, especially on drivers who regularly conduct long journeys - such as truckers and taxi drivers.In 2007 researchers at the St Louis University School of Medicine found that in a group of 898 skin-cancer patients, 53% of cancers occurred on the left side (US driving side). Patients who spent more hours per week behind the wheel had a higher chance of cancers occurring on their left.