I have a single, gigantic, east-facing window in my apartment, because I’m bad at real estate. But seriously, I know that probably sounds like a great feature, but it can be a pain. In addition to making curtain hanging and sleeping in intensely unpleasant, my window has the added consequence of pouring in unwanted UV rays into my life.
If you think that staying indoors or in your car during 10 a.m. and 4 p.m. is a surefire way to avoid sun damage, think again, my friend. Though you’re not getting the sun’s full force at its most powerful time of day and you’ll avoid the burn of UVB rays, those UVA rays might be doing long-term damage that you can’t immediately see. In fact, time of day matters even less when we’re talking UVA rays. Eek!
So, what are the options for a skin-conscious gal with a picturesque window that gets all up in the sun’s face? Or a guy who’s hitting the road for a cross-country trip?
How Much Sun Do You Get Indoors? In Your Car?
You’re almost certainly getting some sun in your home, office, and car, but exactly how much? While it’s not nearly as much as when you’re in direct sunlight, windows don’t do a complete job of UV defense.
Standard Erythemal Dose (SED) is a measurement of roughly the amount of UV-exposure it would take to induce erythema (redness) in healthy people who are the most sensitive to the sun. It’s the equivalent of 100 joules per square meter (Jm-2) (joules are unit of measurement for energy or heat) (World Health Organization). On average, those who work indoors get about 7 to 10 SED per day in the spring and 2 or more SED per day in the winter (Journal of the American Academy of Dermatology). Granted, this is definitely less than the SED you’d get outdoors, but it’s more than the 1 SED per day that’s generally considered to be a safe amount.
And you can bet you’re getting some sun in your car, too. A study done by the University of Washington found that cases of malignant melanoma (MM) and Merkel cell carcinoma (MMC) in the United States were more likely to be found on the left side (i.e. driver’s side) of the body (Journal of the American Academy of Dermatology). But don’t fret too much: In another study where professional drivers were asked to roll up their windows and jack up the AC instead, participants lowered their annual exposure to the equivalent of a weeklong ski trip. And there’s even more you can do to make sure you don’t even get that much UV exposure.
Which Rays Get through Windows?
Ever notice that you don’t seemed to get burned on long car rides or sitting by the window in your office, but you do seem to get tan? That’s because clear window glass typically blocks short waves (UVB = 290-320 nm) and lets in a surprising amount of long waves (UVA = 320-400 nm). Clear glass lets in a whopping 62.8% of UVA rays. But, keep in mind, not all glass is created equal; for example, tinted glass blocks more UV rays than clear glass (gray-tinted glass only lets 0.9% of UVA rays).
You probably know that UVB rays are often referred to as “burning” rays and UVA rays are often referred to as “aging” rays. That’s a fairly accurate mnemonic. The erythema (redness) and sunburn associated with UVB rays rears its ugly head quite quickly after exposure. But less intense UVA rays have few immediately apparent consequences aside from tanning (they’re the rays responsible). Don’t let that fool you. These rays, which are about 30 to 50 times more prevalent than UVB rays, penetrate the skin more deeply and cause all kinds of skin problems over time.
While they might not make you look like a lobster, they’re involved in serious long-term issues, such as skin cancer, solar elastosis, DNA damage, and signs of premature aging (Cosmetic Dermatology; Journal of the American Academy of Dermatology; Journal of Investigative Dermatology; Skin Cancer Foundation).
What Can You Do?
Don’t panic! While the UVA rays coming in through windows can be damaging, they are less than what you’d get outside and some places are more protected than you think. For example, tinted, reflective, low-emissivity, and laminated glass can all have some UV-filtering capabilities. And there are steps you can take at home and in your car to make sure you aren’t getting too much sun when you don’t want it.
If you have the capability (and aren’t a renter), you can get UV-coated glass, which block upwards of 98% of UV rays, and can be used in combination with other glass products for even more protection. Another option for cars and homes are UV filter films, which can block up to 99.9% of UV rays. To pick the right films, check out this list of films that have the Skin Cancer Foundation’s Seal of Recommendation. You can put these over car and indoor windows — particularly if you spend a lot of time by a window (at a desk, for example) — to make sure you’re not getting too much sun. And if you’re a renter like me, look for removable or static cling films that shouldn’t cause problems with your lease. Not only will these window solutions keep out the UV rays, the right choice can help cut down on glare, lower your energy bill, strengthen windows against shattering, and protect your furniture and carpets from sun damage over time.
And be conscious of times when you’re exposed to UV rays without being aware. For example, keeping the windows rolled down on a road trip can be refreshing, but it also puts you in direct sunlight (without even so much as the UVB-filtering window). For maximum sun protection, use UV filtering films and keep the windows up on car rides.
Overall
You might not see the effects right away, aside from a slight tan, but the UVA rays coming in through windows do damage your skin over time. These rays can result in higher risk of skin cancer and DNA damage, and can cause skin to age prematurely. But the solutions are pretty simple. If you UV-protect your windows, whether by installing UV-protective glass or by using window films, you can save yourself a lot of sun damage — even if you’re a renter. So, while the blinding sunrise in my 12-foot window might still keep me from sleeping it, window films will ensure that I’m not getting unwanted UV rays.