There is no question most skin cancers are related to sun exposure, yet even with sunscreen sales approaching $1 billion a year, skin cancer rates continue to climb. Melanoma diagnoses have risen nearly 2 percent a year since 2000 and are increasing even more among young white women.
Some experts blame inappropriate use of sunscreen, saying that people do not apply enough lotion (a golfball-size dollop) or do not reapply it every two hours as instructed. But there’s another major concern: Until recently, many sunscreens with a high sun protection factor, or SPF, were designed primarily to protect people from ultraviolet B rays, the main cause of sunburn. These sunscreens may have enabled users to stay out longer but did not necessarily protect them from ultraviolet A rays. These are associated with aging and skin damage, but some experts believe they may also be implicated in skin cancer.
“Sunscreen is not a magic bullet,” said Dr. Steven Q. Wang, director of dermatologic surgery and dermatology at Memorial Sloan-Kettering Cancer Center in Basking Ridge, N.J., and a spokesman for the Skin Cancer Foundation, which receives funding from sunscreen manufacturers. “It’s just one of the defenses against the harmful effect of UV radiation, and that message gets lost.”
This summer, most of the sunscreen on store shelves must conform to new Food and Drug Administration labeling rules that may help remedy consumer misperceptions. Still, concerns remain about ingredients in some sunscreens.
Use of the label “broad spectrum protection” now means the sunscreen has been proved to protect against both UVA and UVB rays, although the UVA protection may be comparatively weaker. Any product with an SPF lower than 15 must carry a label warning that it will not protect against skin cancer. Products cannot claim to be waterproof, only water-resistant, and labels must note a time limit of either 40 or 80 minutes before the sunscreen is ineffective. Manufacturers can still sell sunscreens with SPFs that exceed 50, though F.D.A. officials are evaluating whether they should remain on the market, said Reynold Tan, a scientist in the agency’s Division of Nonprescription Regulation Development. It’s not clear that sunscreens with higher SPFs actually are more effective, and consumers may not apply them as frequently.