Blue as the sky, pungent in odor, its name comes from the Greek for smell. Ozone, compared to other gases (oxygen, nitrogen, carbon dioxide), is rare in our upper atmosphere. Squashed down to sea level air pressure, all Earth's ozone would be Fig Newton-filling thin... less than one-eighth inch. Most of it (about 90%) ebbs and flows through the stratosphere, six to 25 miles above the ground. But ozone's unique optical properties allow it to function as a shield, keeping enough harmful ultraviolet (UV) radiation from reaching the ground to make life as we know it possible. Even just a little too much UV radiation and cells in human skin start to alter in unhealthy ways.

Sunshine strikes the Earth in rays of varying wavelengths. Long rays (infrared) are unseen but felt as heat. Intermediate length rays are visible as light. Shorter rays (ultraviolet) are also invisible and are further divided into three groups:

1) ultraviolet A (UVA), beneficial in low doses but may increase the chance of cancer in high doses
2) UVB, primarily responsible for sunburn and cancer
3) UVC, the shortest and most dangerous. UV rays contain enough energy to damage

DNA in living skin and eye cells. DNA controls your cells' ability to heal and reproduce. Earth's ozone layer allows life to flourish by passing the longer, beneficial wavelengths and effectively blocking almost all UVC, some UVB, and a little UVA.

According to NASA's ever-spinning satellites, the ozone layer's wavering protection lays four to eight percent thinner over the entire earth than it did ten years ago. A depletion of that magnitude could raise the chance of skin cancer in North America as much as 15 percent. Some experts disagree. NASA says Yes, Rush Limbaugh says No, but the point ends up being moot. Skin cancer can be thought of as an outdoor syndromes, the result of periods of intense overexposure to ultraviolet light even if the ozone was not depleted.

An estimated 32,000 U.S. citizens malignant melanoma, the vilest form of skin cancer, and between 7000 and 9000 will die when the cancer metastasizes (spreads) to other vital organs. That's a 300% rise in the last decade. Melanoma occurs in the melanocytes, the cells of the skin that determine skin color, and it occurs most often in people who are fair-skinned and freckled, people who sunburn easily. The average age at which melanoma strikes has been dropping dramatically. Ten years ago it was considered unusual to find skin cancer in anyone under 40. This year fully one-fourth of all melanomas will involve people in their 20s and 30s. Tragically, children are the most susceptible, but the problem may not show up for years. If caught early, malignant melanoma is virtually 100 percent curable. Physicians recommend a monthly skin check for the symptomatic ABCDs of skin cancer.

A for Asymmetry: One half of a mole or skin spot doesn't match the other half.
B for Border Irregularity: Ragged, notched, or blurred edges.
C for Color: Changes in color from black to brown to red, often with a combination of colors. Blue and white may appear.
D for Diameter: Any mole or spot that grows to more than one-fourth inch, about the size of the end of a pencil eraser.

Malignant melanoma is one of three common forms of skin cancer, but not the most common. That distinction belongs to basal cell carcinoma, with about one half million cases reported annually. Basal cells make up the base of the epidermis, the outermost covering of the body. UV radiation can cause these cells to reproduce too fast, producing a tumorous growth. Basal cell carcinoma usually start as a slow-growing, small, shiny (or pearly) bump that becomes an open sore taking longer than three weeks to heal. They often bleed, crust over, and open to bleed again. The cancer may be an itchy or tender reddish patch that comes and goes.

Sometimes it's a pale splotch, like a scar, and sometimes a circular growth with a raised border and depressed center. Squamous cell carcinoma, the second most common skin cancer, accounts for about 100,000 cases each year. Like the other forms, it appears most often on the face, ears, hands and forearms. In the past 50 years, shoulders, back and chests on men, and the lower legs of women, have become increasingly popular sites for skin cancer due to deliberate exposure of those body parts to UV radiation. Squamous cells make up most of the epidermis. When they become cancerous, they may look like basal cell cancer, but the problem can also appear as a wart that bleeds and crusts over, bleeds and crusts over. Cancerous squamous cells grow faster and metastasize more frequently than basal cell carcinoma.

Sun can damage skin in ways other than cancer. The earliest sign of skin damage is sunburn. Sunburns that continue to worsen several days after exposure may be a sun allergy. Sun allergies sometimes show up as severe sunburns, and, less often, as a poison-ivy-like rash. Overexposure to sunlight causes premature aging of the skin. But all of these problems can be thought of as preparation for later episodes of skin cancer. According to the Skin Cancer Foundation: The sun is the cause of at least 90 percent of skin cancers.

The danger of ultraviolet radiation is increased by reflection. Depending on the angle of reflection, water can reflect up to 100 percent of UV light. Angle of reflection is determined by the height of the sun above the horizon. Early in the morning and late in the evening, with the sun low in the sky, water may bounce only 10 percent of the UV rays back at you. At noon, with the sun directly overhead, water absorbs most ultraviolet light, and reflectivity drops to about five percent. But mid-morning and mid-afternoon, with the sun at a 35-45 degree angle, water can reflect all the UV rays striking its surface.

Sun-related skin problems, happily, are among the most preventable of outdoor problems. Take cover . . . the first line of defense is worn. Tight-weave clothing blocks a large amount of UV radiation, especially if it stays reasonably dry. A full-brimmed hat will shade face and neck, and a floppy brim breaks up UV better than a rigid brim. Sunscreens dramatically reduce the chance of skin problems. Although most experts agree screens with an SPF of 15 sufficiently protect most skin, recent studies show that higher SPF numbers offer additional protection, especially in the first few hours of exposure. Be sure your sunscreen guards against UVB and UVA radiation. Sunscreens are maximally effective if smeared on when skin is warm, and allowed to soak in for about a half-hour before extreme exposure. If you're someone with a very susceptible skin-type, consider completely blocking UV radiation with an opaque substance such as zinc oxide.

Ultraviolet A bombards the earth at an almost constant rate throughout the day, but approximately 80 percent of UVB strikes between 10AM and 3PM. Try to minimize your exposure during those hours.

Some medications, combined with sunshine, decrease the time it takes for UV light to damage skin: tetracyclines, antihistamines, sulfa drugs, diuretics, some oral contraceptives. Consult your physician or pharmacist.

UV light damages eyes as well as skin. The conjunctiva can swell from UV exposure, sun-induced cataracts can form from repeated exposure, and direct UV will burn the retina. Wear sunglasses that absorb or reflect UV light.

Back to Curriculum Updates