Health: Indecent Exposure.(protecting skin from ultraviolet radiation through sunscreens)

indecent exposure

Some people don't use it enough; others rely on it too much. What scientists now know -- and many people don't -- about sunscreen.

ingredients can be found individually in many sunscreens.) "The bottom line," says Yohini Appa, executive director of research and development at Neutrogena, "is you can't correlate the UVB protection with UVA protection."

t takes about one ounce of sunscreen -- a shot-glass full -- to cover the average woman's body. Studies show that people apply one fifth to one half of that amount, leading to an alarming lack of protection. An SPF of 25, which means the wearer can remain in the sun 25 times longer than usual before burning, becomes an SPF of 7 if half the correct dose is smeared on. "People put on too little, too late," says Martin Weinstock, professor of dermatology at Brown University in Providence. Even the most health-conscious women fall short on sunscreen from time to time, and some of this failure is deliberate. "I never intentionally tan now. But if I go for a bike ride, I might forget the sunscreen to get a little sun," admits Jennifer, a 32-year-old mother in Denver. Or they may shield their skin selectively. "My legs are truly a scary white at the start of summer, so I always want them to get a bit of a tan," says Mindy, 36, a Web producer in Brooklyn. "I know that I should use self-tanning lotion, but I don't trust myself to do it evenly." Many people look to sunscreen as a means of buying time outdoors. "The number-one thing about sunscreens is they allow people to stay out longer," Stern says. "I'm a fair-skinned person who, before the era of sunscreens, could not have his shirt off midday in the summer without ...