Choosing Sunscreens

New Warnings About Sunscreens

08-01-2009 // Roger Di Silvestro

The more researchers study the sun’s rays and how they damage our skin, the more they see the need for improving today’s protective lotions.

YEARS AGO, as an underling in the U.S. Army, I was stationed on the Pacific Front: San Francisco, California. There, at the Letterman Army Institute of Research (LAIR), my buddies and I engaged in combat with one of humankind’s most relentless enemies, and at the same time one of our oldest allies: the sun, a known carcinogen but also the basis of life on Earth.

At LAIR we were constructing a preemptive defense system against the sun, in the form of sunscreen, which back then we called suntan lotion. Before you develop any notions of Army dudes and dudettes lying around a swimming pool slathering on Coppertone at taxpayer expense, let me tell you that my memories of that time include sore lips and the lingering taste of cardboard. The sunscreens we tested went on our lips, which we then pressed against a piece of cardboard with a slit in it, attached to an ultraviolet-light-generating machine, which blasted us with known quantities of ultraviolet light. Against this standardized exposure we were able to determine which sunscreens worked best.

Back then the Army was interested mainly in avoiding sunburn in warm, sunny parts of the globe, like Vietnam. Today, we know much more about the effects of the sun, in particular that prolonged exposure can cause not just sunburn but also deadly cancers. In fact, with the thinning of the protective ozone layer in the Earth’s atmosphere, sunlight is causing more and more of them, with up to 1.5 million cases diagnosed yearly in the United States. Nearly 10,000 people so afflicted die each year. About one in three fair-skinned Americans will develop skin cancer after age 60.

The sunscreens we were testing at LAIR, in the days before the hole in the ozone layer had become part of the common parlance, were designed to protect against ultraviolet B rays (UVB). UVB causes the skin to produce a pigment called melanin, which darkens the skin. It also can cause sunburn if you spend more time in the sun than your skin’s defenses can handle.

In the past, creating a sunscreen that blocked UVB was seen as a major accomplishment. However, studies during the past 10 years indicate that another form of ultraviolet light, UVA (A rays) may also contribute to solar cancers, suppressing the immune system and allowing cancer cells to proliferate. New research on UVA suggests that to get protection against more than a sunburn (which itself does some bad things, aging skin prematurely), you need something more powerful than yesterday’s suntan lotion or even most of today’s sunscreens, since many of them are designed primarily to stop UVB rays.

But some do block UVA. Look for formulas that include zinc oxide, which blocks the widest range of rays from the UVA spectrum, or avobenzone, which also goes by the moniker Parsol 1789. Sunscreens containing these substances are on the cutting edge of combating the UVA threat, and they give you an edge against the sun.

Two other factors will sharpen that edge—sun-protection factor (SPF) and proper application. Select not only a sunscreen with the most-effective UVA blockers but also with an SPF that matches your personal skin needs . Experts suggest putting on about a shot-glass full of sunscreen every 90 minutes or so, unless you’re doing something that washes it off, like swimming or sweating, in which case, reapply more often.

Medical research on UVA is so new that the federal Food and Drug Administration has not yet determined how sunscreen companies should test their products for UVA protection. But new rules are expected in 2005, so stay tuned to learn about improvements in warding off solar carcinogens.

The biggest breakthrough in sun protection may be occurring at the Boston University School of Medicine, where researchers are testing a new sunscreen that uses DNA snippets that are absorbed by skin cells when the sunscreen is applied. The snippets send out chemical messages that make cells respond as if they had been damaged by the sun, triggering defense mechanisms that reduce cancer caused by later exposure to ultraviolet light. “The effects are relatively long lasting after a single application, at least days,” says Dr. Barbara Gilchrest, chair of the university’s Department of Dermatology and one of the researchers developing the new sunscreen. So far, the DNA-enhanced sunscreen has been tested only on mice and guinea pigs. “It will be a long time before this approach is available to the public,” Gilchrest says. Meanwhile, she suggests using water-resistant, broad-spectrum sunscreens as the most enduring protection against the ultraviolet.

Roger Di Silvestro is a senior editor for this magazine.

Preventing Sunburn
What’s SPF Got To Do With It?

Sunscreens are rated numerically based on their sun-protection factor (SPF), which indicates how long the lotion will protect you against sunburn based on your skin’s sensitivity. For example, if you can stay out 5 minutes before you burn without protection, then a lotion with SPF 30 will allow you to stay out for 150 minutes, presuming you apply the recommended amount. Unfortunately, many people apply less than half this amount and then get proportionately less protection. “People should pick sunscreens that they find pleasant to use, with an SPF of at least 15,” says Dr. Barbara Gilchrest, chair of the Department of Dermatology at the Boston University School of Medicine. She also recommends minimizing exposure to midday sun and wearing protective clothing during intense or prolonged exposure.

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