Spending a lot of time driving a car may increase your risk of skin cancer - especially on the exposed parts of your body on the side next to the car window (the left side in the United States and other countries where people drive on the right side of the road; the right side in the United Kingdom and other countries where people drive on the left).
The risk is increased even among people who keep their car windows closed.
In most cars, only the glass in the windshield is the type that blocks both ultraviolet A (UVA) and ultraviolet B (UVB) rays. The glass in the side and rear windows keeps out only UVB rays, not UVA. Blocking UVB prevents sunburn, but it does not completely protect against skin cancer.
In a study conducted at the St. Louis University School of Medicine, which involved 898 people who had skin cancers on one side of their body, men were more likely to develop skin cancers on the side of the body next to the car window (since this was an American study, this means the left side). Preliminary data gathered from skin cancer patients by the St. Louis researchers indicates that those who spent the most time each week driving were more likely to develop skin cancers on the left sides of their bodies. The risk was further increased in those who sometimes kept the windows open when they drove.
The same pattern was not seen in women, which may reflect the fact that women are more likely than men to sometimes ride on the passenger side of the car and therefore receive more nearly equal amounts of sun exposure to both sides of their bodies.
The Skin Cancer Foundation, a nonprofit organization devoted to the prevention and treatment of skin cancer, notes that penetration of UVA rays through car windows may place both drivers and passengers at risk for skin cancer - an important issue since automobile travel is at an all-time high. The risk may be especially high for some commuters. Nearly 10 million Americans spend more than an hour driving to work each day and the same amount of time driving home. This is 50 percent higher than the number who had such lengthy commutes in 1990. A substantial number of commuters - more than 3 million - spend more than 90 minutes per day traveling in each direction. People with long commutes and those who drive as part of their work may need to take special precautions to protect themselves against UVA rays while driving.
Another group of people who may be at high risk of skin damage from UVA rays transmitted through car windows is babies and children who spend a lot of time in the car. Babies and young children usually ride in the back seat, where all of the glass around them is the type that does not block UVA rays.
Putting on sunscreen before getting into the car is one way to protect against UVA rays. (Make sure to choose a sunscreen that provides UVA protection as well as UVB protection.) Another approach involves having UV-protective films professionally installed on the car windows.