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When you’re traveling by car, train, or bus, which side do you choose — the sunny side or the shady side? Our insights and recommendations will help you make a more informed decision.
Teresa Larkin, an associate professor at the University of Wollongong (Australia), explained how much ultraviolet (UV) radiation passes through different types of glass and when to use sunscreen.
Does Glass Block UVA and UVB Rays?
UVA and UVB are two types of ultraviolet radiation that reach the Earth. UVA makes up about 95 percent of that radiation, while UVB accounts for roughly 5 percent.
UVB rays mainly reach the upper layers of skin and are responsible for sunburns, cataracts, and some forms of skin cancer. UVA rays penetrate deeper, causing cellular damage that can also lead to skin cancer.
Window glass in homes, offices, and cars blocks UVA and UVB rays to varying degrees.
Only laminated glass can completely block UVA. When UVA passes through other types of glass, it can still cause skin damage and increase the risk of cancer.
Windshields Offer Better Protection Against UVA Rays
Car windshields block about 98 percent of UVA radiation because they consist of two layers of laminated glass. However, side and rear windows made of tempered glass do not fully protect against UVA. Research shows up to 56 percent of UVA rays can pass through those windows.
UV protection depends on the type of glass, its color, and whether it is tinted — not on the vehicle’s age or class. Gray or bronze glass and window tinting improve UVA protection. Window tinting can block roughly 95 percent of this type of radiation.
The Driver’s Seat: The Highest Risk Zone
Sitting in the driver’s seat or on the driver’s side carries the highest risk of UV exposure. A U.S. study found more skin cancer cases on the left side of the body than on the right — especially on the face, head, and arms, with higher numbers on the legs as well. Seventy-four percent of cancerous lesions were on the left side, while 26 percent were on the right.
Researchers also found these cases were more common in men than in women.
Cataracts and other eye damage are also observed more frequently on the driver’s side.
About UV Radiation Penetrating Through Home Windows
We often notice UV exposure from home and office windows in the form of faded walls and furniture.
Most types of glass used in buildings allow a significant amount of UVA to pass through — between 45 and 75 percent. Thicker, tinted, or film-coated glass provides better protection. The best options are laminated glass or double-glazed tinted windows, as reported by Science Alert.
Most modern office buildings are fairly well protected from ultraviolet rays. Thanks to modern glazing, windows in these structures let less than 25 percent of UVA through. Some “smart” windows block radiation because of special chemical treatments.
Sunscreen and Sunglasses
Should you use sunscreen when exposed to direct sunlight through glass? It depends on your skin type, the season, and whether the glass is tinted.
If your car windows are tinted, you may not need to use sunscreen during your trip.
In an untinted car, you can get sunburned in about one hour at summer midday and in about two hours at winter midday.
Sitting by a home window, you can get sunburned in roughly half an hour in summer and about one hour in winter. Wear sunglasses while driving or sitting near a window at home if the UV index exceeds 3. The UV index uses 13 levels: the higher the level, the greater the risk to your skin and eyes.
