UV rays or Ultraviolet Radiation are part of the light spectrum that reach the earth from the sun. UV wavelengths are shorter than visible light therefore they are invisible to the naked eye. Ever hear of UVC? Not likely. That’s because most UVC rays are blocked by our ozone layer and never reach the earth.
However, both UVA and UVB rays are able to penetrate the earth’s atmosphere and both are responsible for premature skin aging, eye damage (including cataracts), and skin cancers. They also suppress the immune system.
How do UV rays cause cancer?
UV rays damage the skin’s cellular DNA. The skin darkens as a self-defense mechanism in an attempt to prevent further DNA damage. It is this cellular damage that can lead to skin cancers. This casts a whole new light on the sun tanned look.
What are UVA Rays:
UVA rays account for 95% of the UV radiation that reaches the Earth’s surface. UVA rays are present with relatively equal intensity during all daylight hours throughout the year and can penetrate clouds and glass. As you can see from the above picture, UVA rays penetrate much deeper into the dermis than UVB rays.
Since tanning booths emit doses of UVA as much as 12 times that of the sun, they are considered much more dangerous than direct sun exposure. Recent research has shown that if someone uses tanning booths in their youth, that they are 75% more at risk for melanoma.
What are UVB Rays:
UVB are known to damage the skin’s top layers of skin, called the epidermis. UVB rays are the primary cause of sunburns. UVB rays intensity varies by season, location and time of day. The most significant amount of UVB hits the US between 10 AM and 4 PM from April to October.
UVB rays are generally blocked by glass.
Here are some interesting facts about UV rays:
- About 65 percent of melanoma cases can be attributed to ultraviolet (UV) radiation from the sun.
- About 90 percent of nonmelanoma skin cancers are associated with exposure to ultraviolet (UV) radiation from the sun.
- Up to 90 percent of the visible changes commonly attributed to aging are caused by the sun.
- A person’s risk for melanoma doubles if he or she has had more than five sunburns at any age.
- Incidence of melanoma continues to rise at a rate faster than that of any of the seven most common cancers.
- One or more blistering sunburns in childhood or adolescence more than double a person’s chances of developing melanoma later in life.
- While melanoma is uncommon in African Americans, Latinos, and Asians, it is frequently fatal for these populations. That’s because they generally go undetected until it is too late.
- Children under 6 months should not be exposed to the sun.
Best Practices as Recommended by the Skin Cancer Foundation:
- Seek the shade, especially between 10 AM and 4 PM.
- Do not burn.
- Avoid tanning and UV tanning booths.
- Cover up with clothing, including a broad-brimmed hat and UV-blocking sunglasses.
- Use a broad spectrum (UVA/UVB) sunscreen with an SPF of 15 or higher every day.For extended outdoor activity, use a water-resistant, broad spectrum (UVA/UVB)sunscreen with an SPF of 30 or higher.
- Apply 1 ounce (2 tablespoons) of sunscreen to your entire body 30 minutes before going outside.Reapply every two hours or immediately after swimming or excessive sweating.
- Keep newborns out of the sun. Sunscreens should be used on babies over the age of six months.
- Examine your skin head-to-toe every month.
- See your physician every year for a professional skin exam.
Disclaimer: The above article is only for informational purposes and is not intended to replace medical advice.
References:
Rogers, HW, Weinstock, MA, Harris, AR, et al. Incidence estimate of nonmelanoma skin cancer in the United States, 2006.Arch Dermatol 2010; 146(3):283-287.
Armstrong BK, Kricker A. How much melanoma is caused by sun exposure? Mel Res 1993 December 3(6):395-401.
Pleasance ED, Cheetham RK, Stephens PJ, et al.A comprehensive catalogue of somatic mutations from a human cancer genome.Nature;2009; 463:191-196.
U.S. Environmental Protection Agency. Health effects of overexposure to the sun. Link.Updated July 1, 2010.Accessed January 25, 2011.
Pfahlberg A, Kolmel KF, Gefeller O. Timing of excessive ultraviolet radiation and melanoma: epidemiology does not support the existence of a critical period of high susceptibility to solar ultraviolet radiation-induced melanoma. Brit J Dermatol March 2001; 144:3:471.
Ries LAG, Melbert D, Krapcho M, Stinchcomb DG, Howlader N, Horner MJ, et al. (eds). SEER cancer statistics review, 1945-2005. Bethesda, MD: National Cancer Institute; Link. Accessed January 24, 2010.
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Lew RA, Sober AJ, Cook N, Marvell R, Fitzpatrick TB. Sun exposure habits in patients with cutaneous melanoma: a case study. J DermatolSurgOnc1983; 12:981-6.
Cress RD, Holly EA. Incidence of cutaneous melanoma among non-Hispanic whites, Hispanics, Asians, and blacks: an analysis of California cancer registry data, 1988-93. Cancer Causes Control 1997; 8:246-52.
