Sun; let the fryer beware.

A sun-lover will probably tell you, "A little burn is a small price to pay for a great tan." But where there's smoke, there's fire. And where there's sun, there are dangerous ultraviolet (UV) rays.

Even when you don't get burned, UV rays add a new wrinkle to tanning. In fact, if you don't use a strong sunblock, they could add hundreds of wrinkles to your face, or even cause skin cancer.

It's a bit like war. "What you've got is a kind of bombing" by sunlight, says Dr. Albert Kligman, a dermatologist at the University of Pennsylvania.

MASTER BLASTERS

When you step outside, you probably notice the sunlight you can see. But visible light is only a small part of the sun's spectrum, the whole variety of rays it sends our way.

Each kind of sunlight wiggles toward us in a wave of a certain length--its own wavelength. Stealthy UV rays have wavelengths too short for your eyes to detect.

But UV rays can still "see" you: They zip right into your skin. And they pack a punch of energy--enough to ruin the molecules that keep skin healthy. UV rays actually break the bonds that hold these molecules together.

One of the two most dangerous UV bombers is the shorter--wavelength kind, called UVB While you listen to your Walkman on the beach, invisible UVB rays penetrate the outermost layer of the skin, the epidermis. There the bomb goes off. The UVB rays lay waste to basal cells, one type of cell that divides to produce new skin.

And when UVB rays reach a cell's control center, its nucleus, the blast can wreak havoc. Certain bonds in DNA--the cell's master molecule--are particularly sensitive to UVB rays. The bonds can't handle the rays' energy, so often break apart. Fortunately, cells have the ability broken DNA. But the they have to make repairs, the more likely they are to miss some damage. Or, the cells' repair machinery may make a mistake--forming a new bond in the wrong place. Either way, the result is a mutation, a change in the cells' genetic operating instructions. If enough damage occurs, the cells may divide uncontrollably. When that happens, the result is often skin cancer.

According to the American Cancer Society, an estimated 32,000 Americans will be diagnosed with melanoma, an often deadly form of skin cancer, this year alone. And that number is on the rise, possibly because people who've spent summer after summer soaking up the sun are now paying the price.

WRINKLE, WRINKLE LITTLE SCAR

Even if you don't get cancer, too much sun may leave you looking like a shriveled prune. The wrinkle-causing culprits: longer-wavelength UVA rays. They carry less energy than UVB rays, but they travel deeper into the skin, into the dermis. That's where collagen and ribbonlike elastin, the proteins that keep your skin smooth and supple, hang out.

"When you look at the elastin of a baby's skin, which has never been out in the sun, [you see] nice parallel interlaced bundles," says dermatologist Darrell Rigel of New York University Medical Center.

Elastin that's been in the sun a lot, however, loses its shape. "It turns into |solar spaghetti," says Rigel. That's because "the UV rays break and reform elastin's bonds." When that happens, Rigel explains, "the bands of elastin end up all pulling in different directions," wrinkling the skin above.

BLOCK IT--NOW

That's why skin doctors say it's so important to use sunblock--whenever you're in the sun. And the time to start is now. A recent study shows that one blistering sunburn in childhood is associated with an increased risk of melanoma later in life.

As for wrinkles, Rigel warns, if you keep soaking up rays, your skin will look old before its time.

So let the fryer beware. This summer don't have a (bomb) blast. Go outside, but use "sun sense." The Skin Cancer Foundation says: Wear a funky, wide-brimmed hat, pop on cool UV-blocking shades (see SW 5/7/93, pp. 8 and 18), take cover with clothing and shade, and rub in that sunblock.