Many people engage in a love-hate relationship with the sun. In the North, the sun is often welcomed after a long, cold winter. Some people claim that the sun lifts their spirits. For some, it is a matter of appearance: they prefer tanned skin to a pale complexion. For others, it is a matter of outdoor interests: they spend time in the sun engaging in a number of activities. At the same time, everyone knows that the sun causes skin damage, wrinkling, and, perhaps most alarming, fatal skin cancers. Regardless of your motivation for staying in or out of the sun, we think that it is important for you to know the science behind what effect the sun has on your skin. We hope that you will use this information to make wise decisions regarding sun safety and protection.
UVA and UVB
The sun emits ultraviolet rays. Two of these rays, UVA and UVB, reach the Earth’s surface to impact your skin. UVA is composed of longer wavelengths, which penetrate deeper into the skin, while UVB is composed of shorter wavelengths.
SOURCE: www.skincancer.org
UVA:
• is associated with skin aging and wrinkling (also known as photoaging)
• is the form of ultraviolet energy utilized in tanning booths
• can pass through window glass
• plays a role in the development of skin cancer
UVB:
• is associated with sunburns
• contributes to tanning and photoaging
• cannot pass through window glass
• plays a major role in the development of skin cancer
The American Academy of Dermatology’s website provides a useful way of remembering the difference between UVA and UVB rays. UVA rays are predominantly responsible for the Aging effects of sunlight while UVB rays are responsible for the Burning effects of sunlight. The most important take-home point, however, is that BOTH types of ultraviolet rays play a role in the development of skin cancer.
How do UVA and UVB rays lead to skin cancer?
The detailed answer to this question – as it relates to the responsible rays, the targeted genes, and the associated molecular changes – is constantly evolving and is actively being investigated. The basic idea, however, is well-established: UV radiation damages the DNA of cells within the skin. Cellular damage is dangerous because it can contribute to mutations that can develop into cancer.
“But I don’t see any evidence of sun damage…”
Actually, you do!
A tan is evidence of sun damage. It is the body’s attempt to protect itself from harmful rays. When melanocytes (the pigment-producing cells in your skin) are exposed to sunlight, they produce more color because they are trying to shield you from the sun. This process itself, however, can contribute to skin cancer.
A sunburn is a more obvious sign of sun damage. It is your body’s way of telling you to get out of the sun!
With time, increased exposure to the sun leads to cumulative damage, and the detrimental effects of the sun on your skin become more evident. What are some of these skin changes?
REFERENCES:
Brash DE, Ziegler A, Jonason AS, Simon JA, Kunala S, Leffell DJ. Sunlight and sunburn in human skin cancer: p53, apoptosis, and tumor promotion. J Investig Dermatol Symp Proc. 1996 Apr;1(2):136-42.
Facts About Sunscreens. The American Academy of Dermatology. http://www.aad.org/media/background/factsheets/fact_sunscreen.htm.
FP, De Fabo EC. UVB and UVA initiate different pathways to p53-dependent apoptosis in melanocytes. J Invest Dermatol. 2009 Jul;129(7):1608-10.
Marks JG, Miller JJ. Structure and Function of Skin. In: Lookingbill & Marks’ Principles of Dermatology. 4th ed. Elsevier Inc; 2006:7.
Understanding UVA and UVB. The Skin Cancer Foundation. http://www.skincancer.org/understanding-uva-and-uvb.html.