Last June, U.S. Food and Drug Administration (FDA) testing and labeling rules went into effect for chemical sunscreen products. And not a minute too soon, according to USC skin cancer researcher Myles Cockburn.

“It’s well overdue,” said the epidemiologist, an associate professor of preventive medicine at the Keck School of Medicine of USC. “There’s a wide variety of sunscreens out there — some very effective, some less so.”

Under the new rules, only sunscreens that meet FDA standards for protection against both ultraviolet A and ultraviolet B rays with a minimum SPF 15 value may be labeled “broad spectrum.” None may exceed an SPF value of 50+. (Because the SPF — or “sun protection factor” — scale is widely misunderstood by consumers, high values tend to promote unsafe behavior.)

Sunscreen manufacturers also may not claim their product is “waterproof,” “sweatproof” or a “sunblock.”

Only compounds containing zinc oxide or titanium dioxide — usually chalky and opaque in color — actually provide a physical barrier against the sun, Cockburn explained. Ordinary sunscreen works chemically through absorption by the skin. But to be effective against sun damage, it must be applied thoroughly at least 20 minutes before exposure, and it must be reapplied after sweating or getting wet.

As a skin protection strategy “it’s really imperfect,” lamented Cockburn, noting that sunscreen actually has been associated with increased risk of the deadliest skin cancer, melanoma — probably because it lulls users into a false sense of security, causing them to soak up more sun than they would otherwise.

Ideally sunscreen should be seen as a “last-ditch protection” when all other strategies have been exhausted, he said. Those preferred strategies include:

• staying indoors as much as possible during peak hours for sun exposure (10 a.m. to 4 p.m.)

• when going outside can’t be avoided, seeking shade

• when shade is unavailable, covering up with longs sleeves and a hat.

Not all fabrics are created equal, Cockburn noted. A niche for sun-safe clothing has emerged (such as UVskinz), but the FDA has yet to issue any manufacturing guidelines. Cockburn recommended that buyers beware: Just because a rash guard is labeled “UV block” doesn’t mean it has been lab tested.

He offered these common-sense suggestions for evaluating the sun-blocking properties of clothes:

• In general, lined fabrics are best, but tight weaves are also good.

• Any fabric that blocks overhead light is likely to block the majority of UV rays.

• Fabric color should make no difference.

Unfortunately, in Cockburn’s experience, the more sun-proof a fabric, the less likely it is to absorb moisture and feel comfortable.

Manufacturers’ claims about sunglasses also should be taken with a grain of salt. While many are advertised as UV blocking, there’s scant enforcement of such claims. Exposure of the cornea, lens or other parts of the eye to UV rays can lead to serious health problems, such as cataracts and macular degeneration, as well as deadly ocular or uveal melanomas. A cheap pair of sunglasses can actually increase one’s risk of these problems, Cockburn warned. The dark lens will cause the pupil to dilate, admitting more UV light than would the naturally contracted pupil of the naked eye.

Some tips when shopping for sunglasses:

• Lens color and darkness have nothing to do with the ability to block UV rays.

• While major brands, such as Oakley or Ray-Ban, are more reliable than $5 drug store sunglasses, do careful research before buying.

• Choose sunglasses that block 99 to 100 percent of both UVA and UVB rays.

• Frames matter. Choose close-fitting or wraparound styles that eliminate light from every angle, including reflective light.

Cockburn has been drumming these and other healthy habits into school children through SunSmart, an innovative educational program he and his Keck School team members, in conjunction with the Joint Education Project, have been implementing through the Los Angeles Unified School District since 2006. Last year, they won a four-year, $3.2 million grant from the National Institutes of Health to ramp up and formally evaluate the program.

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