New sunscreen labeling regulations were issued by the federal government last week for the first time in more than 30 years. The U.S. Food and Drug Administration's (FDA) new regulations attempt to ban sunscreen manufacturers from labeling their products with misleading information. Starting next year—two years for smaller companies—products that protect the skin from burning but not from long-term damage must indicate so on the bottle, and they cannot hint that they have greater durability and strength than they actually possess.

If the new labeling helps Americans protect their skin from sun exposure, it has the potential to reduce the rates of skin cancer in the U.S. Ultraviolet (UV) radiation bears responsibility for 90 percent of non-melanoma skin cancers, which will afflict one out of every five Americans, and 65 percent of melanoma cases, which kill about 8,700 people a year. But many questions remain regarding the extent to which the new labels will translate into real protection from skin cancer.

"My hope is the FDA regulations will make consumers choose sunscreens more wisely," says dermatologist Jeanine Downie, a spokesperson for the Skin Cancer Foundation.

Under the new rules, only products that protect skin from both UVA and UVB sun rays can be marked "broad spectrum," and sunscreen that does not meet the broad spectrum requirements, or that has a sun protection factor (SPF) of less than 15, must carry a warning that the product does not diminish the risk of skin cancer or prevent premature skin aging.

Only products labeled "broad spectrum" protect the skin from long-term damage such as premature aging and the risk of skin cancer. Although both UVA and UVB (two types of ultraviolet radiation) can cause long-term damage, UVB rays are the main culprits when it comes to causing sunburn. Because a sunscreen's SPF only indicates its ability to protect the skin from sunburn, lotions that protect against UVB radiation alone can still earn a high SPF without providing proper protection against long-term effects from both types of radiation. By requiring that sunscreens be labeled "broad spectrum" only when they deflect both UVA and UVB, the FDA is helping consumers choose a product that will also protect their skin from long-term damage.

Most commercial sunscreens combine two types of ingredients: light-absorbing chemicals and physical blockers. "The best protection is using a chemical with a physical blocker at once," Downie says, rather than using a purely physical or purely chemical formula.

Physical blockers, usually metal oxides such as zinc oxide or titanium oxide, act like miniature mirrors, reflecting the sun's rays before they can reach the skin. Chemical blockers, on the other hand, do not scatter UV rays. Instead, they absorb light, and then release it in the form of heat, essentially converting it to a different type of energy. Types of organic components include octinoxate, which blocks UVB rays, and oxybenzone, which protects against UVB as well as some UVA radiation.

Both types of sunscreen ingredients have come under fire from at least two advocacy groups: Friends of the Earth takes issue with physical blockers when they are reduced to nanoparticle size in order to render sunscreens more transparent. Unlike larger flecks of metal oxide, they fear the nanoparticles might pass through the skin. What if these materials have different physical properties when reduced to nanoscale, or interact negatively with the other chemicals in the sunscreen?

The Environmental Working Group, on the other hand, accepts nanoparticles in non-powder, non-spray sunscreens, instead reserving its animus for certain chemical components such as oxybenzone. The body can absorb this ingredient through the skin, and the EWG claims that it has been linked to hormone disruption and sun-activated allergic reactions.

Although the FDA is reviewing the safety information for sunscreen ingredients as part of its new regulations, the agency "does not have any reason to believe these products are not safe for consumer use," according to an FDA press release.

Downie agrees. "None of these products have proven to be toxic in humans at all," she says. "Sunscreen does more good than it does harm."

In addition to encouraging the manufacture of sunscreen that provides broad-spectrum protection, the FDA has banned exaggerated claims about sunscreens' strength and durability. Even broad-spectrum sunscreen with an SPF over 15 cannot be called "sunblock," because no lotion entirely blocks the sun's rays. Nor can sunscreen products be labeled as waterproof or sweatproof: There is no sunscreen that stays completely on the body when exposed to water. At the most, a product may be water- or sweat- resistant.

Not only do sunscreens come off the skin (particularly when exposed to water or toweled off) but their chemical components break down over time. To preserve the efficiency of sunscreens, the products should be stored in a cool, dry place and replaced every year. In addition, they should be reapplied at least every two hours or more frequently if exposed to water or rubbed off. Under the new regulations, water-resistant formulas must say on the label how long the product will protect skin before needing to be reapplied, either 40 or 80 minutes.

"Bottom line—we want clarity in the product, to make people put it on and reapply it," Downie says.

In addition, the FDA proposed a rule that would cap advertised SPF at "50 +", because the evidence that more expensive, higher-SPF products provide more skin protection is lacking. Many who wear high-SPF sunscreen spend more time in the sun and reapply less frequently than those whose sunscreen has a lower SPF. As a result, they end up with both sunburn and possibly long-term skin damage. In addition, many misunderstand the meaning of SPF.

If a very fair beachgoer burns after, say, 10 minutes of skin exposure, then a sunscreen of SPF 15 will extend her time in the sun by a factor of 15, allowing her 150 minutes of exposure before her skin burns—as long as she reapplies the lotion regularly to ensure that it doesn't degrade or rub off. Following the same application rules, SPF 30 sunscreen will give her 300 minutes, SPF 40 400 minutes and so on.

The tests used to assign values of SPF to various products, however, use more sunscreen than the average consumer. During testing, two milligrams of lotion are applied to every square centimeter of skin. In practice, most people use only one fifth to one half of that quantity, which means that their skin does not receive the full protection promised by the SPF number on the bottle.

For full SPF protection Downie recommends spreading at least two ounces (enough to fill a shot glass) of sunscreen on exposed surfaces, taking care to remember oft-neglected areas such as the back of the neck as well as the tops of ears and feet. But ultimately, the best protection is to stay out of the sun whenever possible.