Ultra violet light, which is part of natural sunlight, has been linked to a large list of medical problems, including skin cancer, cataracts, and other forms of blindness.
Anyone suffering from a sun burn knows first hand the negative effect that too much UV light can have on their body. Many modern forms of glass, from eye glasses to home windows, have UV blocking properties. It would be easy to assume that automobile windows offer the same protection. Unfortunately, according to a recent study published in JAMA Opthalmology that doesn't appear to be that case.
UV light can be broken into two sub-categories; ultraviolet A, and ultraviolet B. While both types have negative affects on the eyes and skin, UVA light has long been regarded as the more harmful of the two. It is up to fifty times more abundant, shines at an equal intensity throughout the entire day, and can even pass through clouds and basic forms of glass.
New findings, however, have show than UVB, with enough prolonged exposure, can cause serious damage to a cell's DNA over time.
Study author Dr. Brian Boxer Wachler, of the Boxer Wachler Vision Institute in Beverly Hills, California points out that while data isn't complete in regards to the level of UV protection car manufactures implement in their side windows, there is strong evidence that shows that cataracts and skin cancer are more prevalent on the left side of the body, which is the more exposed side for left hand drivers in America. The opposite is true for Countries like the UK, where drivers are exposed to UV light on their right sides.
In his experiments, Dr. Boxer Wachler used a hand-held UVA light meter in order to measure the level of UVA protection in both the front windshields and the side windows of 29 different automobiles. The cars were all manufactured between the years 1990 and 2014, and represented 15 different automobile brands.
Using the UVA sensor, light levels were documented for the exterior of the vehicle, behind the front windshield, and beside the driver's side window. The results of each measurement were used to determine the amount of UVA light blocked by each window.
The average UVA blockage for the front windshield's of the cars tested was 96%, and the total range for all vehicles was 95-98%; a very close grouping. The driver's side windows, however, offered far lower protection by comparison. Only 71% of UVA light was filtered on average, with some samples blocking as much as 96%, but other were as low as 44%. Of the 29 cars tested, only 4 blocked 90% or higher.
Dr. Boxer Wachler said of his study “The side windows of the automobiles tested provided variable levels of UVA potection, 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."