What Are Ultraviolet (UV) Rays?

You probably know ultraviolet (UV) rays can burn and tan our skin. Scientists have also confirmed exposure to UV rays causes premature aging and skin cancer. We figure a better understanding of UV radiation will light the way to better health.

What’s the difference between ultraviolet rays, ultraviolet light and ultraviolet radiation?

The simple answer is nothing. In the sunny field of photobiology—the branch of science concerned with the effects of light on living organisms—those three phrases mean exactly the same thing.

So why do we need three names for the same concept? One answer might be this invisible, ultraviolet sun-energy actually has multiple roles: rays, light, radiation, waves and particles.

What are ultraviolet rays?

UV rays are electromagnetic radiation beyond the violet end of the visible spectrum. We can’t see them, but if we could, they would come after the color violet on a rainbow. They’re produced by the sun, but are mostly absorbed by particles of dust and smoke in the earth’s atmosphere. UV rays can cause burns or tans, but are integral in the skin’s production of vitamin D. Basically, we need them, but not too much. (i)

What do experts say about ultraviolet rays?

The spectrum ranges from lower energy, longer-wavelength forms of radiation to higher energy, shorter ones. Just like when learning the colors of the rainbow, our friend ROY G. BIV is useful here as well. After infrared light, the longest electromagnetic waves are red, then orange, yellow, green, blue, indigo, violet (ROY G. BIV) and finally, ultraviolet with the shortest of solar wavelengths.(ii)

Among ultraviolet rays, there is also an order of wavelengths. UVC rays are the shortest, followed by UVB and then UVA rays, which have the longest wavelengths. Because they are the shortest, UVC rays do not penetrate the atmosphere, whereas UVA rays are the most prolific. It might help to remember the shorter the wavelength, the more energetic the radiation, and the greater the potential for harm. Think of a puppy. It’s smaller, it’s more energetic, and unchecked, it can do damage.

Lucky for us, the ozone layer eliminates virtually all UV radiation below 290 nanometers (or billionths of a meter). This is referred to as vacuum ultraviolet because it is strongly absorbed by air. Thus, those puppies—vacuum UV, UVC and the shortest UVB wavelengths—are blocked. On the flip side, only minimal UVA is filtered. The UV radiation that gets through the ozone layer and reaches the earth is about 10-percent UVB and 90-percent UVA at midday (solar noon). This means the burning (UVB) rays are the most intense at solar noon, while the aging and damaging (UVA) rays are always a steady risk.(iii)

What's the difference between UVA and UVB rays?

Not only do UVA rays penetrate further into the earth’s atmosphere, they also penetrate further into our skin. This results in early skin aging because the radiation damages our collagen, the fibrous protein that gives our skin the ability to stretch. An easy way to remember this is to think of the “A” in UVA as standing for aging. High doses of UVA might be responsible for melanomas. The rates of melanoma have been rising over the past few decades. This could be because sunscreens that only blocked the UVB (burning) rays encouraged people to stay out longer than they would have otherwise.(iv) While scientists now know UVA rays contribute to the development of skin cancers by damaging cells, it is not yet known whether or not UVA rays initiate skin cancers.(v) (vi) Either way, it’s important to remember that even though UVA exposure doesn’t burn your skin, it causes long-term skin damage and increases your risk of cancer. Only broad-spectrum sunscreens will protect your skin from both types of radiation.

How do UVB rays affect us?

Sunburns occur when UVB rays penetrate the epidermal layer of our skin and damage our skin cells’ DNA. In order to prevent the reproduction of these mutated and potentially cancer-causing cells, our bodies kill the cells and get rid of them, via burned, peeling skin. This allows new, healthy cells to take their place (vii) (viii). Aside from the pain of the initial burn, it’s also believed repeated exposure to UVB rays could lead to non-melanoma skin cancers.(ix) (x)

Should we just avoid the sun?

Not at all! And who would willing give it up? We love basking in the warmth of a summer day and our bodies need vitamin D (xi) .It prevents a host of diseases, which is why a history of discriminating against sun exposure has had a negative impact.

Strong bones and a sunny disposition—the benefits of UV radiation

In 1820, English physician Sir Everard Home discovered heat wasn’t the only thing that affected the skin when it was exposed to sunlight (xii). He did an experiment where he placed one hand beneath a black cloth and left the other one bare in the sun. Despite the hand under the cloth being much hotter, the hand exposed to direct sunlight changed color. It was then he realized this change was chemical rather than thermal.

Soon after, sun exposure became a popular and effective treatment for rickets in children. Doctors would cure urban children with bent, deformed bones by taking them on country retreats or exposing them to sun lamps. These pioneers in heliotherapy—the use of sunlight to treat sicknesses—didn’t yet understand the relationship between bone development and health, but utilized the sun’s healing powers nonetheless.

Another chemical reaction that occurs when we’re exposed to UV radiation is the production of serotonin in our brain and beta-endorphins in our skin. UVB rays mentally make life a beach, even when we’re not at one.

Additional advantages of UV radiation include:

  • Prevents autoimmune disorders including type 1 diabetes and rheumatoid arthritis
  • Aids sleep
  • Lowers blood pressure
  • Treats symptoms of psoriasis
  • Decreases risk of colon, prostate, breast and ovarian cancers

What are the risks of UV radiation?

Chronic overexposure to sunlight can damage the skin. We also know devouring chocolate for every meal negatively affects your cardiovascular health. And drinking nothing but red wine could have multiple adverse health effects.

This isn’t to say one can’t indulge from time to time. Similar to chocolate and red wine, doctors have proven moderate sun exposure is good for you. Unlike chocolate and red wine, humans cannot live without UV radiation—but we’d never want to have to do without any of it! (xiii)

Sun-proponent Michael Holick claims the only major medical downside to moderate sun exposure is non-melanoma skin cancer. This is because, “there is no credible scientific evidence that moderate sun exposure causes melanomas.” (xiv)

While other specialists feel UV radiation plays a key role in melanoma, the relationship between the two is open to debate. Until we learn more, the best path to a healthy middle ground starts with protecting our skin, while enjoying the benefits of sunshine.

How do you stay safe in the sun?

Enjoy it, but take precautions, like avoiding the sun during peak hours, wearing protective clothing and wearing sunscreen. Avoiding sun exposure is a good idea at peak seasons and times of the day, particularly if you have fair skin or are taking medications that increase sun sensitivity. (xv)And of course, wearing a mineral sunscreen, like Goddess Garden’s will help you safely enjoy your time on the sun.

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(i) http://medical-dictionary.thefreedictionary.com/ultraviolet+rays
(ii) Holick, M. F., and Mark Jenkins. The UV Advantage. New York: I, 2003. 6.
(iii) Nelson, Christopher G. “Photoprotection.” Sunscreens: Regulations and Commercial Development. Ed. Nadim A. Shaath. Boca Raton: Taylor & Francis, 2005. 19-44. 21.
(iv) Holick 7.
(v)http://www.skincancer.org/prevention/uva-and-uvb/understanding-uva-and-uvb
(vi) Holick, M. F., and Mark Jenkins. The UV Advantage. New York: I, 2003. 7.
(vii) http://health.ucsd.edu/news/releases/Pages/2012-07-09-sunburn-and-inflammation.aspx
(viii) http://www.ncbi.nlm.nih.gov/books/NBK26873/
(ix) Urbach, Frederick. “The Negative Effects of Solar Radiation: A Clinical Overview.” Sun Protection in Man. Ed. Paolo U. Giacomoni. Amsterdam: Elsevier Science, 2001. 39-65. 56.
(x) Holick 6.
(xi) Holick 6.
(xii) Urbach 41.
(xiii) Holick 6.
(xiv) Holick 11.
(xv) Nelson 34-38.

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