About 8 years ago, I noticed a small area just in front of my left ear that kept on crusting over and wouldn’t heal even with antibacterial ointment. I assumed that is was something called a pre-auricular sinus, which is very common, because I am an ENT doctor and I see them all the time.
I finally went to a dermatologist who diagnosed it as a skin cancer (a basal cell carcinoma), and it was successfully excised. I have been out in the sun a lot in my life, so I didn’t think anything else of it, but then I learned that the majority of skin cancers occur on the left side of the face, just like mine. Why? Because when you drive your car, the sun comes through the window and blasts the left side of the face causing damage to the skin, increasing the risk of developing a cancer.
It is important to understand that the ultraviolet spectrum contains two general categories, Ultraviolet A (UVA) and Ultraviolet B (UVB). UVB contains the wavelengths that cause an acute sunburn, but which are needed to make Vitamin D. So you need UVB, but not too much. If you expose large amounts of skin (chest, back, legs) to the sun (without sunscreen) mid-day for 20 minutes Spring-Summer-Fall, you will make about 5-10,000 units of Vitamin D.
UVA contains the wavelengths that penetrate deeper into the skin and are most responsible for photoaging (wrinkles). We now know that both UVA and UVB in excessive amounts cause skin cancer. The truck driver pictured below demonstrates the cumulative effects of UVA on the left side of his face after 30 years on the job:
The important thing to understand is that UVB cannot penetrate glass — so you cannot get a sunburn through glass. You also cannot make any vitamin D through glass. But UVA goes through glass with no problems. You absolutely should take steps to stop this!
The auto manufacturers treat windshields with special coatings that block both UVA and UVB, but the side windows allow a very large amount of UVA transmission. All the major tints block both UVA and UVB, protecting your face and neck. Why don’t the auto manufacturers do us the favor of applying a coating that blocks UVA? Because they don’t care.
Most states regulate the amount of tint you can have on your side windows, but most cops (at least in California) won’t hassle you unless it is really dark. Even if you put a clear plastic “tint” on the windows, you will prevent UVA from passing through. You just won’t get the additional infrared protection that a true tint provides, which helps keep the interior cool in hot weather.
Dermatologists don’t seem to ever mention this issue, and I don’t know why — but they absolutely should. I will never again own a car without aftermarket tint, and it is especially important for young people who haven’t accumulated wrinkles yet.
Now you know, so go out and put some tint on your windows, and protect your skin!!