SCIENCE & TECHNOLOGY
June 24, 2002
Volume 80, Number 25
CENEAR 80 25 p. 38
ISSN 0009-2347


WHAT'S THAT STUFF?

SUNSCREENS
Active ingredients prevent skin damage

It was decades ago when i had time to lounge poolside for hours on end, but I do remember roasting myself in the sun for a healthy tan, basting my body with oils to enhance the effect.

Times have changed. We've always known that sun can burn our skin. But now we also know that long exposure to the sun's ultraviolet rays can prematurely age skin and ultimately lead to skin cancer. Add to those worries the depletion of upper atmospheric ozone: As a result, we are all likely to get an even higher dose of UV light during our time outdoors than during the days when I was a pool lizard.

And that healthy tan? It's really not so healthy after all. "A tan is the body's reaction to damage," Coty Senior Vice President of R&D Ralph Macchio says. "But you don't have to limit your fun in the sun if you use a good sunscreen."

It's no surprise then that sunscreen sales to beach and pool goers are on the rise. And active sunscreen ingredients are also finding their way into a variety of daily-use personal care products, such as moisturizers, eyeshadow, foundations, and lipsticks. Annual sunscreen actives sales in the U.S. and Europe are each about $100 million and are likely to grow 4% annually through 2006, according to industry consultant Kline & Co.

Sunscreens have not always been so prevalent. The first commercial sunscreens came out during World War II, when U.S. sailors used zinc oxide preparations to prevent sunburn. The general public picked up the practice in the 1950s and 1960s. I can remember some veterans sitting on the beach in the 1960s sporting a white blob of the stuff on their nose.

Companies such as Givaudan, a Roche division spun off in 2000, began to develop organic sunscreens in the late '60s, as they looked for a sunscreen that wouldn't leave a white haze on the skin. Then scientists started to become concerned about UV light's effects on skin.

Today, there are 17 sunscreen active ingredients approved for use in the U.S. and 25 approved for use in Europe. What's a body to use?

THERE ARE TWO basic types of active ingredients: inorganic and organic. Both afford protection against UV-B rays in the 280- to 320-nm range, the primary culprits in sunburn. Some offer additional protection from UV-A rays in the 320- to 400-nm range, which can penetrate more deeply into the skin and do greater long-term damage.

Inorganic sunscreens use titanium dioxide and zinc oxide. They work primarily by reflecting and scattering UV light. The organics include widely used ingredients such as octyl methoxycinnamate (OMC), 4-methylbenzylidene camphor (4-MBC), avobenzone, oxybenzone, and homosalate. They work primarily by absorbing UV light and dissipating it as heat.

Formulators often combine inorganic and organic sunscreens for a synergistic effect. In fact, that is how most are capable of achieving very high SPF--sun protection factor--ratings. SPF is a measure of how effectively a sunscreen in a formulation limits skin exposure to the UV-B rays that burn skin. The higher the number, the more protection a sunscreen formula affords against sunburn.

However, the SPF system does not provide an objective measure of protection against UV-A radiation. And although sunscreen formulators do say their products contain broad-spectrum protection, a U.S. consumer has no clear way to compare the UV-A protection offered by one product with another. Europe has an unofficial method, whereas Japan and Korea have a system in place.

Among the inorganics, zinc oxide offers much better UV-A protection than TiO2. Among the U.S.-approved organics, avobenzone offers the greatest UV-A protection, but others offer some protection as well, depending on their absorption spectrum.

A problem with inorganics is that they may leave a haze on the skin. Generally, the oil in a sunscreen formula helps wet the inorganic particles and gives the optical effect of transparency. But use of a formula with high levels of TiO2 could remind you of that veteran with the white blob on his nose.

However, cosmetic ingredients supplier Uniqema says its newest TiO2 won't have that problem. Its new Solaveil Clarus line has a particle size distribution between 40 and 50 nm, offering not only good UV protection but also avoiding the occurrence of large particles that give a whitening effect.

There are other ways around the problem. According to Gabriel E. Uzunian, Engelhard's director of cosmetic applications, a red interference pigment added to a sunscreen formula can counteract the whitening effect. The TiO2-coated mica pigment complements and enhances light skin tones and gives a more "natural" appearance to a beach sunscreen, Uzunian says.

Recent scientific work by environmental toxicologist Margaret Schlumpf and colleagues at the University of Zurich's Institute of Pharmacology & Toxicology suggests that OMC and 4-MBC--two widely used organic sunscreens--are potential endocrine disrupters. But industry research and government advisory committee reviews have disputed the work. The Food & Drug Administration still approves OMC for use in the U.S., though it never approved 4-MBC. The European Union's Scientific Committee for Cosmetic Products & Non-Food Products continues to approve OMC and 4-MBC.

So what is a body to do? "Everyone goes with safety," notes Karl Harris, Haarmann & Reimer's director of cosmetic ingredients. "I know of no one not using OMC, but some in Europe are taking a closer look at 4-MBC."

It all makes you think that people who have lived in the desert intuitively know something we sun worshipers never learned: It may not be a bad idea at all to wrap yourself in white, light-reflecting robes, especially at the beach. Otherwise, do choose a sunscreen with UV-A and UV-B protection--and wear it.



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