We’ve all heard about the fact that the sun’s UV rays can damage the skin, both causing cancer and aging it—but what most people don’t realize is that there are different types of UV radiation.
Since July is UV Awareness Month, I thought this would be a perfect time to help explain the difference between the UV rays—and talk about just why they’re so dangerous to the skin. (I did a project on this in the 6th grade; it’s something I’ve always been passionate about!)
The sun’s ultraviolet or UV rays are divided into: UVA rays, UVB rays, and UVC rays. All are invisible to the human eye—and all UV radiation can damage the skin’s cellular DNA, triggering genetic mutations (which can then cause cancer). For years, it was thought that UVB rays were the most damaging to the skin, but it’s only been in recent years that researchers and scientists have discovered that UVA rays are even more harmful. Bottom line: all UV light is a proven human carcinogen. (Take a look at this illustration, below, from the American Cancer Society to see just how UV light can affect the skin.)
What you need to know:
UVA light—or Ultraviolet A Radiation—are called long-wave rays because they have a wavelength of 320 to 400 nanometres or nm (how wavelength is measured). This type of radiation is not filtered by the earth’s ozone layer, meaning as much as 150% as much UVA reaches the earth’s surface as UVB.
Why you need to be concerned: This light penetrates deep into the skin—into the mid-dermis—and is responsible for tanning and also for skin cancer, eye damage (including cataracts), and the breakdown of collagen, the main structural protein responsible for supporting the skin. (Note: when collagen breaks down, the skin sags—a key factor in premature aging.) And what’s more, these UV rays are present year round, at all times of the day, and can penetrate through clouds and glass.
“A tan results from injury to the skin's DNA; the skin darkens in an attempt to prevent further DNA damage. These imperfections, or mutations, can lead to skin cancer. Tanning beds are particularly bad for your skin because they emit only UVA rays. In fact, tanning salons emit doses of UVA as much as 12 times that of the sun.”
A good way to remember what UVA rays do to the skin is: the “A” in UVA is for “Aging”
UVB light—or Ultraviolet B Radiation—has a wavelength of 290 to 320 nm. It’s somewhat filtered by the ozone, but it only makes up about 4 to 5% of UV light (UVA makes up the rest).
Why you need to be concerned: This UV light penetrates less deep than UVA rays; it penetrates to the basal, or bottom, layer of the epidermis (the outermost layer of skin), where melanocytes—the cells responsible for pigment—are found. This is the type of light that can cause burning of the skin as well as skin cancer—and eye damage (including cataracts). While UVA rays are present at all times of the day, year round, UVB radiation is most prevalent between 10 a.m. and 4 p.m. and it doesn’t penetrate glass.
“UV radiation—both UVA and UVB—can also suppress the immune system, why people with herpes seem to break out in cold sores after exposure to the sun.”
A good way to remember what UVB rays do to the skin is: the “B” in UVB is for “Burning”
Take a look at this helpful illustration from the Skin Cancer Foundation:
UVC light—or Ultraviolet C Radiation—has a wavelength of 100 to 290 nm and is completely filtered out by the ozone layer so 0% reaches the earth’s surface.
Why you need to be concerned: This type of ultraviolet radiation could become a concern if the hole in the ozone layer ever grew to affect more of the earth.
"Did you know? UV radiation reduces our collagen production by 80% for 48 to 72 hours—within 24 hours of exposure to the sun."
Some things you can do to protect yourself from the sun’s UV rays:
√ Always wear broad-spectrum sunscreen (this protects against both UVA and UVB rays) whenever you’re outdoors—whether it’s 7 in the morning or 3 in the afternoon.
√ Avoid the sun between 10 a.m. and 3 p.m.—when UVB’s burning rays are most prevalent.
√ Never use a tanning bed. People who use tanning beds are 2.5 times more likely to develop a type of skin cancer called squamous cell carcinoma, and 1.5 times more likely to develop a type of skin cancer called basal cell carcinoma. In fact, according to researchers, when teens use tanning beds, they increase their risk of melanoma (the deadliest kind of skin cancer) by an incredible 75 percent!
√ Consider adding UV-protective film to your car's side and rear windows (many front windshields typically have it already) as well as to house and business windows—to block up to 99.9 percent of UVA radiation.
√ Know that clothing is UV-protective. Thicker shirts have more SPF than thinner ones, and darker colors give you more SPF protection than lighter colors. Clothing labeled UPF is also specifically protective against the sun’s rays.
√ Wear UV-protective sunglasses whenever you’re outdoors to shield your eyes from damaging UV rays.
I hope this information helps you protect yourself against the sun’s rays. Know that while UV light is a proven human carcinogen, skin cancer is one of the most preventable types of cancer.
Stay sun safe!