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SUNSCREENS

by Larry Thompson

You would think that all the questions about sunscreens have been answered by now. You slather it on before you go to the beach. It keeps you from being fried to a crisp. And, if you use enough, it helps prevent your skin from taking on that wrinkled, leathery look of photo-aged skin. Best of all, it protects you from the harmful ultraviolet rays that cause skin cancer.

If that's your perception, you're mostly right, but that view is not complete. While all the basic information remains true--sunscreens do protect skin from sunburn--a scientific debate simmers about the importance of lower-energy ultraviolet light to skin damage and whether current sunscreens provide adequate protection.

Just recently, the Food and Drug Administration delayed until December 2002 the implementation of a so-called final monograph on sunscreens- the kind of rules that FDA publishes for the more than 100,000 over-the-counter (OTC) drug products currently on the market. OTC drug monographs--which cover 80 classes or therapeutic categories of OTC drugs, including sunscreens--are a kind of "recipe book" covering acceptable ingredients, doses, formulations, and labeling. Once a final monograph is implemented, companies can make and market an OTC product without the need for FDA pre-approval. New prescription drugs, on the other hand, require pre-approval before they can go on the market.

In 1997, Congress ordered FDA to issue regulations on the prevention and treatment of sunburn. The agency completed the sunscreen monograph in May 1999 to meet the congressional mandate, and it initially gave the industry until May 2001 to implement it. The new regulation established a list of 16 active ingredients that companies can use in sunscreen products and simplified the labeling so consumers will know how to use these products properly. The monograph also applied to sunscreen-containing cosmetics.

But questions about the harmfulness of a certain type of ultraviolet light and how to best label sunscreens led FDA to delay these regulations until further studies could be conducted.

Sunburns and Suntans

Sunburn, which is caused by a type of ultraviolet (UV) light known as UVB, has served as a surrogate for more serious skin disorders, such as melanoma and basal and squamous cell carcinoma, three forms of skin cancer. Basically, the thinking was if you prevent sunburn, you'd prevent skin cancer.

In recent years, however, scientists have come to appreciate that a different form of ultraviolet light, called UVA, may be just as, or even more, important in causing some skin disorders. Although experts still believe that UVB is responsible for much of the skin damage caused by sunlight--especially sunburn--UVA may be an important factor in other types of sun damage, including photoaging and the development of skin cancers. Most sunscreens do a good job blocking UVB but fewer filter out most of the UVA.

"Both laboratory and epidemiological studies indicate that sun screens may not block the initiation or promotion of melanoma formation," says Ronald D. Ley, Ph.D., at the University of New Mexico School of Medicine's Steve Schiff Center for Skin Cancer in Albuquerque, N.M. Studies using a fish model of melanoma induction "suggest that the action spectrum [the defined wavelength of ultraviolet light that damages skin] for erythema induction is different than the action spectrum for the induction of melanoma." Erythema means red skin, that is, sunburn.

"There are a lot of data on both sides of the question about the tanning link to melanoma," says John Lipnicki of FDA's Center for Drug Evaluation and Research (CDER).

Now, with extra time before the monograph will be implemented, FDA and the scientific community have gone back to wrestling with the thorny questions that were not resolved in the initial document. Researchers will further study active ingredients, and test methods to measure how well products block UVA's effect on the skin. The agency will also work to make the labeling clearer.

Risks and Reality

These questions transcend academic curiosity. The death rate from melanoma in the United States has been going up about 4 percent a year since 1973, according to the Centers for Disease Control and Prevention in Atlanta. Although melanoma represents only about 47,000 of the nearly 1.8 million cases of skin cancer diagnosed each year, according to the American Cancer Society, it will cause 79 percent of skin cancer deaths. While cancer treatments continue to improve, melanoma recovery rates remain disappointing. Prevention is the better solution.

As prevention, however, sun screens alone appear to be imperfect. In the first study to test the protective effect of sunscreens on people--not just the hairless mice or other models used in laboratory studies--researchers at the Queensland Institute for Medical Research in Brisbane, Australia, reported in September 1999 that sunscreen use reduces the risk of developing squamous cell carcinoma by 40 percent. But using sunscreen did not reduce the risk of developing melanoma or basal cell carcinoma. The Australian study followed 1,383 adults for five years.

FDA believes sunscreens are an important part of a person's total sun protection strategy, but that sunscreen use alone will not prevent all of the possible harmful effects due to sun exposure, according to agency statements. (See "Safe Sunning.") Borrowing the "Slip, Slop, Slap" slogan from an Australian skin cancer prevention campaign, the American Cancer Society recommends that anyone out in the sun slip on a shirt, slop on sunscreen and slap on a hat.

The education campaign's benefits in Australia have been promising, says Robin Marks, M.B., of the University of Melbourne. "Suntans are out of fashion, especially deep tans. We can measure sunburn rates, and they have gone down." Most importantly, the epidemiological studies show the rates of skin cancer, including melanoma, are going down in the younger groups, says Marks, but not in the older groups whose skin already has been damaged by prior exposure to the sun.

As FDA ponders adjustments to the sun screen monograph before its implementation, the agency finds itself in the familiar position of needing to make regulatory decisions about important public health issues in the face of scientific uncertainty.

UVA vs. UVB

The complexities of light quickly overwhelm freshmen physics students, but some basic principles can be readily understood. In one model of how light works, the electromagnetic radiation can be thought of as a series of waves, like ocean waves at the beach, steadily marching toward shore. At the beach, the wind makes the waves by transferring kinetic or mechanical energy into the water. The harder the wind blows, the more energy in the water and the higher and closer together the ocean waves. On a calm summer day, widely spaced waves lap mildly against the shore. During a hurricane, the wave action intensifies, pounding the sand with closely packed wave after wave of crashing white foam strong enough to wipe away the beach.

The electromagnetic energy in sunlight works much the same way: The higher the energy of the light, the closer together its waves. Some types of light have waves that are far apart--like ocean waves on a calm day. Other types of light have waves that are packed closely together, like ocean waves on a windy day.

This difference in closeness of a light's waves, its wavelength, gives different parts of the electromagnetic spectrum its characteristics, such as the colors of visible light and the destructive capabilities of x-rays and ultraviolet light.

Physicists classify ultraviolet light into three types, by its wavelengths: UVA, UVB and UVC. The dimensions of their wavelengths are roughly 400 to 320 nanometers (nm) for UVA, 320 to 290 nm for UVB, and 290 to 200 nm for UVC. Although it may seem backwards, the shorter the wavelength and the lower the number, the greater the energy level of the light and the more damage it can do. For example, direct exposure to UVC for a length of time would destroy the skin. Fortunately, UVC is completely absorbed by gases in the atmosphere before it reaches the ground.

The longer wavelengths of UVB and UVA, however, pass right through the atmosphere, even on a cloudy day. That's why you can still get sunburned on a cloudy or hazy day. The molecules in sunscreens absorb most UVB and prevent it from reaching the skin just as the molecules of the atmosphere absorb UVC and prevent it from reaching the ground.

UVA, however, is another story.

According to a 1998 review article, most sunscreens do not protect the skin from the longer UVA wavelengths. And that may be critical to the creation of skin cancer. Approximately 65 percent of melanomas and 90 percent of basal and squamous cell skin cancers are attributed to UV exposure.

The precise wavelengths of ultraviolet that contribute to the formation of skin cancer still need to be sorted out. And scientists must still figure out how best to formulate sunscreens to provide effective protection against these wavelengths.

Scientists use a number of techniques to measure the UV-blocking ability of a sun screen. Some rely on electronic laboratory equipment, some on living tissue or live animals. Some testing procedures even use human volunteers.

"We have a good way of measuring UVB protection with a sunburn or erythema test in humans," says Sharon Miller, an optical engineer in FDA's Center for Devices and Radiological Health. But scientists lack a simple measure of UVA's impact on the skin, she says. That makes it difficult to determine how much UVA protection a sun screen provides.

That leaves FDA with an unresolved technical dilemma that it is trying to resolve through additional research. "We are trying to determine a testing method that will demonstrate that a sunscreen is providing UVA protection," Lipnicki says. A claim such as "broad spectrum" on a sunscreen label needs to be supported by evidence that the product provides significant and meaningful protection across the entire UVB/UVA spectrum.

To Australia's Robin Marks, however, the issue is not UVA vs. UVB or even UVA combined with UVB. "The most common skin cancers seen in humans are related to sunlight, not to a limited band of the solar spectrum," Marks says. "It is the whole of all light coming from the sun. Don't concentrate on one band, but the entire spectrum. Keep it off the skin."

The SPF Debate

To figure out how much protection a sun screen provides, most consumers turn to a simple number: the SPF, or sun protection factor, listed on the label. Studies show that most consumers understand that the higher the number, the more the product protects the skin.

Unfortunately, studies also show that people often have the mistaken notion that the higher the SPF number of the sunscreen they use, the longer they can stay--and will stay--in the sun. In August 1999, the Journal of the National Cancer Institute published a study showing that use of higher-SPF sunscreens led to increased sun exposure. Two groups of French and Swiss volunteers used unlabeled sunscreen during their vacations. One group used SPF 10 and the other group used SPF 30. The group using the higher-SPF sunscreen spent 20 percent more time in the sun (72.6 hours vs. 58.2 hours) than the group using the lower-SPF sunscreen.

"Because of variations between individuals, products, exposures, and conditions of use, there is no really easy way to explain SPF in a few words," says FDA's Lipnicki. "In the past, it was explained in terms of the amount of time you could stay in the sun longer with sunscreen than without it before getting 'burned'. We have gotten away from that. Sunscreen should not be used to prolong time spent in the sun. Even with a sunscreen, you are not going to prevent all the possible damage from the sun. Some of the newer research in the last several years shows that the sub-erythemal doses [exposure to the sun that does not cause reddening of the skin], as little as one-tenth the energy needed to get a sunburn, start the process of skin damage of one sort or another."

In the final monograph completed last year, FDA proposed limiting SPF values on a sunscreen label to 30. Products with higher SPFs would be labeled "30+" (or "30 plus"). The agency took this action for two reasons: inadequacies in the testing methodologies for higher-level SPF formulations, and concern that the high SPF labeling may lead consumers to spend more time in the sun than they should.

The SPF portion of FDA's monograph immediately produced opposition from both industry groups and consumer organizations. The National Coalition for Sun Safety, an organization supported by the American Academy of Dermatology, advocated "a floor rather than a cap on SPF," wrote coalition co-chairmen Rex Arnonette, M.D., and Roger Ceilley, M.D. The organization wants a minimum level of SPF to ensure that all products provide some protection.

Industry, primarily represented by the Cosmetic, Toiletry and Fragrance Association (CTFA), opposed the 30-plus cap for several reasons, including consumer confusion, fear that manufacturers would remove effective sunscreen protection in their products to avoid misbranding, and unresolved scientific issues about UVA. With the deferral of the monograph's implementation, the industry, along with the agency, will have additional time to resolve the issues.

The Labeling Controversy

The questions surrounding labeling, which may have less to do with science and more to do with motivating human behavior, may prove to be the thorniest of all. Everyone agrees on the goal: Create a simple label that consumers can easily understand.

In addition to recommending the SPF limit on labels, FDA has proposed further label changes to help clarify the risks and benefits of sunscreen use and how to use the products properly. For example, FDA wants the label to avoid unsupported, misleading or confusing terms such as "sunblock," "waterproof," "all-day protection" and "visible and/or infrared light protection." And when the label says the product is "water resistant," or "very water resistant," it must mean that the product provides the stated SPF level after water resistance testing for a specified length of time. FDA and the industry also are wrestling with what it means to claim that a sunscreen is "broad-spectrum," that is, protective against both UVA and UVB.

Complexity is the problem because consumers want simplicity. Industry already has conducted studies that test the effectiveness of different ways to present information on the label. For example, Schering-Plough Health Care Products of Berkeley Heights, N.J., tested a label that contained another number in addition to the SPF to indicate the degree to which the product protected against UVA. "The second protection number created unnecessary complications and confusion for the consumer," says Patricia Agin, Ph.D., Schering-Plough's photobiology research director. "UVA should complement and not distract from SPF on the label. A descriptive approach better conveyed to consumers the added benefit of UVA protection and did not distract from the SPF number."

"SPF should remain the primary index of efficacy," agrees Jay Nash, Ph.D., of Proctor & Gamble Pharmaceuticals Inc., of Mason, Ohio, "and any additional descriptor should be independent and commensurate with this information. Simplicity is the key to public policy."

Simple or not, the labeling issue is not trivial because studies already show that consumers may not use sunscreens correctly. The public under-applies sunscreens by as much as half of the recommended amount, concluded a study published in the Archives of Dermatology. Consequently, the study argued, consumers are receiving only half of the SPF protection they believe the product provides.

Couple that with prolonged periods of baking in the sun and you have a recipe for future disease.

Larry Thompson is the editor of FDA Consumer.

Safe Sunning

The basic advice about protecting yourself from the harmful effects of the sun remains sound, according to the Department of Health and Human Services. The department continues efforts, launched in 1998 with its "Choose Your Cover" public education campaign, to help all Americans, but especially the young, prevent skin disorders associated with excessive exposure to the sun.

The recommendation is simple: To prevent premature aging, sun damage, and skin cancer, you need to protect yourself and your family from the harmful ultraviolet (UV) rays of the sun. And sunscreen alone will not protect you. You need to use a total program to reduce the sun's harmful effects, including:

Lavishly apply a sun screen with a sun protection factor (SPF) of at least 15 and reapply it every two hours according to the directions on the label.

Reapply sunscreen as needed after swimming, sweating or towel drying. And use sunscreen even on cloudy days.

Avoid the sun during the middle of the day, especially between 10 a.m. and 4 p.m., when the atmosphere absorbs less of the harmful UV rays of sunlight than earlier or later in the day.

If you have to be out in the midday sun, avoid long periods of direct sun exposure. Stay in the shade.

Wear a wide-brimmed hat, protective clothing, and sunglasses.

Never leave children exposed to the sun without adequate protection. Because of the long time it takes for cancer to develop, studies suggest that over-exposure early in life may lead to skin cancers later in life.

Although industry studies show that consumer use of sunscreen products continues to improve--up 13 percent in 1999--the American Academy of Dermatology (AAD) says that consumers still do not apply the correct amounts of sunscreen to achieve the full benefit.

A study sponsored by Seventeen Magazine, Beiersdorf Inc.'s Nivea brand, and the AAD found an increase in the use of sunscreen by teens, but also found problems: Eighty-eight percent of teens spend a significant amount of time in the sun, but only 72 percent say they use sunscreen at least some of the time. Only about 40 percent of the teens say they use sunscreen often or all of the time. Young women use sunscreen more than young men (46.2 percent compared to 30.5 percent), and the reasons given for not using it include the belief that they never burn (30 percent), inconvenience (17 percent), and the desire for a dark tan (6 percent).

The difficulty, of course, is that teenagers won't see the effects of sun damage until they reach their 40s and 50s or later. By then, however, the damage already is done.

For more information on the DHHS education campaign, go on the Internet and connect to ChooseYourCover.

How Sunlight Ages Skin

Take a look at a long-haul trucker sometime, a guy who's been driving for decades. Look closely at his face. One side will have more wrinkles than the other. Guess which one? The left side, the side of his face most exposed to the open window. Do you know why it has more wrinkles? Because it absorbs more direct sunlight than the right side of his face that's shaded inside the truck cab.

Look at the face of a long-haul trucker from a country like Great Britain, where people drive on the left side of the road. The right side of his face has more wrinkles because that's the side that faces the open window.

We're not talking lying in the sun here. We're not talking sunburn. We're talking chronic, long-term exposure to micro-doses of ultraviolet light that never overtly damages the skin, but over the years causes a collection of micro-scars that leaves a telling impression: wrinkles.

The epidermis, the outer layer of skin, "is as thin as a sheet of paper," says John J. Voorhees, M.D., chairman of dermatology at the University of Michigan Medical School. "Ninety percent of the mass of the skin is collagen," a large protein composed of three intertwined chains of amino acids that contributes to the form, function and strength of the skin. That also makes collagen the principal recipient of ultraviolet light damage.

But the pathway to aged skin is not straightforward. Sunlight itself does little direct damage to the collagen protein. A growing body of research shows, instead, that ultraviolet light turns genes "on" and "off"--and which genes get turned on can make all the difference.

Normal skin maintains a dynamic collagen exchange. A common type of skin cell called a fibroblast exudes new layers of collagen when collagen genes are turned on. When collagen is damaged, skin cells produce enzymes that digest and liquefy the large collagen proteins into gelatin for disposal.

Voorhees' group discovered a complex genetic pathway through which sunlight can suppress collagen production by turning off the collagen-producing genes. At the same time sunlight activates collagen digestion by stimulating production of the destructive enzymes.

Damaged skin results. The skin now carries a wound, and it needs to heal. "Anytime you cut yourself more than superficially, there is always a little bit of a scar," Voorhees says. "Our claim is that wound healing is never perfect. It could be 99.9 percent perfect, but never perfect. And that 99.9 percent [healing after sun damage] is going to lead to the slightest imperfection that is not visible to the human eye, but after thousands of these over a lifetime, the micro-scars become macro-scars. This is the UV-induced aging we call photo-aging, and it is piled on top of natural aging that has nothing to do with the sun."

Prematurely wrinkled skin results. Although FDA has approved retinoic acid to treat chronic photo-aging, prevention remains the more effective approach.

Here's the really tricky part: Most of the genetic changes and resulting photo-aging appear to come from so-called UVA, the wavelengths of ultraviolet light in the A band of the spectrum. Most sunscreens currently on the market provide excellent protection against UVB, but not all provide equally good protection against UVA. "If you put on gobs of sunscreen, it blocks" the damage, Voorhees says. "But if you don't use much, it does not block [the damage] at all."

Moreover, sunlight turns on the genetic destruction quickly, but it also stops quickly when you get out of the sun. The level of collagen production is completely back to normal in two days.

"The average person thinks, 'I didn't get pink so I have no photo-aging,'" Voorhees says. "Our data suggest that is not true. You are going to be getting the photo-aged [signals that turn genes on and off] and develop the micro-scars without getting any pinkness at all. You can get photo-aged damage long before you get pink or sunburned."

A Label Caution

Although the Food and Drug Administration delayed implementation of its new rules on sunscreens, one new requirement in the monograph for over-the-counter sunscreen products went into effect on May 22, 2000, as originally scheduled. The new regulation requires all tanning products that do not contain sunscreen to bear the following warning statement on the label:

"Warning-This product does not contain a sunscreen and does not protect against sunburn. Repeated exposure of unprotected skin while tanning may increase the risk of skin aging, skin cancer, and other harmful effects to the skin even if you do not burn."

Tanning products that do not contain sunscreens and do not protect against the harmful effects of UV light are regulated as cosmetics. FDA requires this warning statement so that consumers are fully informed that such products do not provide protection from the sun.

Article reprinted from the FDA site