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What Does That SPF in Sunscreen Really Mean?
by: Angela Pirisi
Sunscreens have long been an ally in the battle against skin cancer, but experts say that people still overestimate just how much protection these products can provide.
The bad news is that skin cancer rates have continued to creep upward, at about 3 percent a year, since the early 1980s, according to the U.S. Centers for Disease Control and Prevention. That includes melanoma, the deadliest form of skin cancer, which is estimated to kill nearly 8,000 people in the United States annually.
Vigilant, proper sunscreen use can certainly help stem the skin cancer epidemic, so what are people doing wrong?
One mistake is believing that sunscreen is all you need to ward off the sun, and another is that the higher the SPF, the longer you can stay in the sun, experts say. The U.S. Food and Drug Administration has been trying to tackle that problem by allowing manufacturers to only market SPF 30-plus on their product labels, since they believe that any higher value is misleading to consumers.
The Sun Protection Factor (SPF) is a laboratory measure scientists developed to measure the time it takes skin to burn under UV exposure, but you have to do some of your own math, since it's an individual thing. If you know how long it takes you to start burning without protection in the midday sun, say 10 minutes, multiply that by the SPF number. In theory, for someone who burns in 10 minutes without protection, a sunscreen with an SPF 30 would deliver 300 minutes of protection against burning -- that's five hours. But experts note that's not the reality.
"That's the theory, but the SPF physically wears off with rubbing, sweating and water. The protection you get is more likely one hour to 80 minutes," said Dr. Henry Lim, chairman of the Department of Dermatology at Henry Ford Hospital, in Detroit.
Manufacturers aren't blatantly lying about protection, however. Lim explained that when sunscreens are tested, the amount applied to the skin is a lot more than what consumers typically use. "So, the 'in use' SPF is lower than the 'label' SPF," he explained. In other words, you're not getting as much protection for as long as you think, because you're in the real outdoors, not an artificially controlled lab.
So, what should you do? Still aim for SPF 15 or higher, said Lim, since the higher SPF does offer stronger protection, although not necessarily much longer protection. An SPF 15 blocks 94 percent of UVB rays, while SPF 30 blocks 97 percent of UVB rays.
An even bigger problem is that scientists haven't developed a standardized way to measure UVA protection yet. So the SPF value on a bottle only guides you as far as UVB rays go. Moreover, scientists are still fine-tuning UVA sunscreen ingredients to try increasing protection against the aging, cancer-causing rays.
"The trouble is that we have very good UVB blockers, but we don't have perfect UVA blockers," said Dr. James Spencer, a clinical professor of dermatology at Mount Sinai School of Medicine in New York City. The best one is Parsol 1789 (avobenzone), but it starts to break down when exposed to the sun. So, it offers two hours of protection, and no more than four hours.
Manufacturers are trying to deliver more foolproof sun protection. For example, last month the FDA approved a new product called Anthelios SX by L'Oreal, which combines three active ingredients to increase UVA protection: a new molecule called ecamsule (marketed as Mexoryl SX), plus avobenzone (Parsol 1789) and octocrylene.
Mexoryl SX is one of a new generation of UVA filters that doesn't break down in sunlight, so it extends protection time. "It's just another option for sun protection available to consumers," Lim said.
Other products are also achieving photostability, and therefore longer-lasting protection, by combining different ingredients in a certain way. For example, Neutrogena developed an ingredient called Helioplex, which stabilizes Parsol 1789, so it provides six hours of UVA protection.
Scientists have also been looking at dietary nutrients to boost skin's defenses against UV damage, and some sunscreen products contain antioxidant vitamins C and E already. "There's some scientific evidence of photo-protection, but they don't replace other sunscreen agents, they're adjunctive agents that help," Lim said. Since both UVA and UVB form free radicals, antioxidants may help prevent the damage they cause that potentially leads to skin cancer.
The ultimate hope is for a sunscreen pill, which you could pop before heading to the beach, with no mess or reapplication required. Already available is Heliocare, a nutritional pill supplement made with a fern extract that offers three hours of UV protection, but it's not meant as standalone sunscreen product.
"It's not something you use in place of a sunscreen, but it's a baby step in the right direction, since increased compliance is what we want," Spencer said.
Despite the advances in sunscreen products, the sun safety messages have failed, especially among young people. Findings from a recent CDC survey indicate that only one in seven (14.2 percent) high school students reported using sunscreen with a SPF 15 or higher when outside for more than one hour on a sunny day.
"People are tanning more, and using sunscreen less now," Spencer noted. "It's hard for young people to worry about something 20 years from now."
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