When you’re driving, chances are you’re not thinking about the level of ultraviolet A light that is beaming through the windows of your vehicle. A new study, however, suggests you might want to, after finding that side windows of automobiles may not offer sufficient protection.

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The side windows of automobiles offer insufficient protection from UVA radiation, a researcher found.

Study author Dr. Brian Boxer Wachler, of the Boxer Wachler Vision Institute in Beverly Hills, CA, publishes his findings in JAMA Opthalmology.

Previous research has linked exposure to ultraviolet A (UVA) radiation to increased risk for skin cancer and cataracts.

According to the Skin Cancer Foundation, while UVA radiation is less intense than ultraviolet B (UVB) radiation, it can cause significant damage to the skin’s DNA over time.

UVA radiation is up to 30-50 times more prevalent than UVB; it is present at a relatively equal intensity during all hours of daylight, and it can pass through clouds and glass.

Dr. Boxer Wachler notes that, in the United States, the level of UVA protection in the windows of automobiles is unclear.

However, he points out that previous studies have suggested that cataracts and skin cancer are more common on the left side of the face – the side of the face that is most exposed to sunlight in U.S. drivers.

Could lack of UVA protection from the glass of automobiles be a contributing factor for these conditions? Dr. Boxer Wachler set out to investigate.

To reach his findings, Dr. Boxer Wachler used a hand-held UVA light meter to assess the level of UVA blockage in the front windshields and side windows of 29 automobiles – with years ranging from 1990-2014 – from 15 automobile manufacturers.

The researcher measured external levels of ambient UVA beaming onto the vehicles, as well as levels of UVA behind the front windshield and the driver’s side window of each vehicle.

Dr. Boxer Wachler then calculated the percentage of UVA blockage in each window.

He found that the average UVA blockage on the front windshield of the automobiles was 96 percent, with each vehicle ranging between 95-98 percent UVA blockage.

However, Dr. Boxer Wachler found that UVA blockage in the driver’s side window was much lower, with an average of 71 percent. Side window UVA blockage was also highly variable, ranging between 44-96 percent. Only four vehicles had side window UVA blockage over 90 percent.

Dr. Boxer Wachler says his results may help explain in part why rates of cataracts and skin cancer are higher on the left side of the body.

[…] the side windows of the automobiles tested provided variable levels of UVA protection, which may expose drivers’ left eyes and left sides of faces to greater cumulative UVA light. This exposure may increase the risk of cataract and skin cancer.

It remains unknown whether this risk can be modified for each individual based on vehicle profile (whether or not sunglasses are worn) or other factors, such as time spent driving in a certain environment.”

Dr. Brian Boxer Wachler

Dr. Boxer Wachler says his findings suggest automobile manufacturers should increase their levels of UVA protection in side windows of vehicles.

Furthermore, he says his results may have wider implications when it comes to UVA protection.

“It brings awareness of the other types of windows that make people vulnerable to the effects of the sun,” he adds. “These findings may also provide support for the recommendation that residential, commercial, and school glass windows have UV protection for adults and children alike.”

In an editorial linked to the study, Dr. Jayne S. Weiss, of the Eye Center of Excellence at Louisiana State University, says the study highlights the need for better UVA protection in the windows of automobiles, noting that the Enhanced Protective Glass Automotive Association have already called for laminated glass in every automobile window.

“Until this occurs,” she adds, “it is helpful for ophthalmologists to inform their patients that eye and skin protection may be indicated not only when outside but also when inside an automobile.”

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