Global Broiling


If you want to keep from getting scorched on the hill, sunscreen is a mandatory accessory. But slathering on any old SPF lotion won't necessarily prevent the sun's rays from causing premature aging and skin cancer. In the U.S., SPF (Sun Protection Factor) ratings only measure how well a product limits your exposure to UVB rays. Fortunately, the Food and Drug Administration is working on ways to evaluate a sunscreen's ability to also block UVA rays—a potent form of deep-penetrating radiation that scientists point to as a factor in chronic skin damage.

But there's still a ways to go. "The FDA's labeling is a bit behind the times, says Robert Dellavalle, an assistant professor of dermatology at the University of Colorado. In Australia, Dellavalle notes, "broad spectrum claims on labeling—meaning the product blocks UVA rays as well as UVB—are submitted to government tests, in addition to SPF ratings. "We should look to adopt a similar system, but it's a lot of work to change the testing methods. It's not going to happen overnight.

While some sunscreens in the States put the broad spectrum tag on their packaging, there's still no mandatory testing of such claims. In the meantime, keep an eye out for ingredients such as zinc dioxide, titanium dioxide, or avobenzone (also called Parsol 1789). "These act like metal blankets that deflect all the sun's rays, says Dellavalle. They tend to cost more, but it's worth the extra few bucks not to have a permanent goggle-tan. —Geordie Brackin

January 2005



8 Images of Global Warming

The USGS Repeat Photography Project's side-by-side comparisons of glacier retreat over the course of a century reveal dramatic climatic change and global warming at Glacier National Park in Montana.