The harmful effects of ultraviolet light may be a fairly recent discovery but those effects are well documented. That’s not to say that the sun is all bad, however. In fact UV light is necessary for our body to produce vitamin D which, together with calcium, is needed to build strong bones. Exposure to adequate amounts of sunlight guards against depression. Ultraviolet light is also beneficial to those battling psoriasis. But too much will damage your skin and can predispose you to developing skin cancer.
To understand why the sun poses such a threat to our skin, we must discuss radiation. What is radiation, anyways? To put it simply, radiation is the transmission of energy. We are in fact surrounded by radiation. Visible light is a form of low-level radiation, as are radio waves and infrared waves. None of this is really harmful however because it is all non-ionizing (which basically means that it’s not strong enough the alter/damage our body’s cells).
Ionizing radiation on the other hand, is sufficiently powerful to damage our cells by stripping electrons from the individual atoms that make up those cells. X-rays are a very common example of ionizing radiation. CT or CAT scans also use x-rays. MRIs do not. Side note: We try very hard to limit patients' exposure to x-ray radiation, especially women and children. But it's important to understand that many times the benefit gained from a certain procedure far outweighs the small increase in risk. A standard chest x-ray produces 0.1 mSv of radiation; the average American is exposed to 3.1 mSv of natural, backround radiation each year. The risk is small, but it is there.
So, back to the sun. The sun produces another type of ionizing radiation called ultraviolet radiation. There are 3 types of UV radiation: UV-A, UV-B and UV-C. All are harmful! UV-C is actually the most harmful but it is completely blocked by the earth’s atmosphere. 99% of what reaches the surface is UV-A.
Ultraviolet radiation damages the skin by destroying structural proteins such as collagen and elastin and producing free radicals (unstable oxygen molecules). This results in premature or photo-aging of the skin. Many of the skin changes that we attribute to old age are more likely due to accumulated sun damage.
UV radiation causes cancer by damaging cellular DNA and the proteins responsible for repairing damaged DNA. The result is a cellular mutation. Often times this mutation leads to uncontrolled cell growth, i.e. cancer.
There are 3 main types of skin cancer: 1) Basal cell carcinoma, which is the most prevalent and least dangerous. 2) Squamous cell carcinoma, the 2nd most common, and 3) melanoma which is by far the most deadly type due to it's ability to rapidly spread throughout the body.
In my next post, we’ll talk about how each type of skin cancer is diagnosed and treated. But in the mean time, protect yourself! The American Academy of Dermatology recommends a water resistant sun screen with broad-spectrum protection (protects against UVA and UVB rays) and an SPF of 30 or greater. You can also avoid unnecessary exposure by wearing a wide-brimmed hat and seeking shade as often as possible.
And remember, "There is no safe way to tan!"*
*Unless your tan comes from a bottle, of course.
Visit the American Academy of Dermatology and read their FAQs here.