Sun smarts

Source: Best Health Magazine, Summer 2008; Photo: Alvaro Goveia

The Canadian Cancer Society estimates there will be 4,600 new cases of melanoma and 900 deaths from the disease this year. It also predicts that 69,000 non-melanoma skin cancers will be diagnosed. For those of us wanting to get outside and make the most of Canada’s oh-so-short summer, preventing sun damage means tracking down an effective sunscreen and following the latest expert advice for playing smart in the sun.

Emerging news on UVA

Sunlight radiates toward the earth in different wavelengths. Scientists have divided the ultraviolet (UV) end of the spectrum into three categories.

UVA rays, the most abundant, can penetrate deep into the skin and affect fibroblasts (cells that produce the elastin and collagens that help keep our skin elastic). UVB rays are less plentiful since the earth’s ozone layer absorbs a significant portion. With greater energy than UVA, they cause more biological changes in our bodies. And, despite the fact that we get exposed to much higher levels of UVA, it’s mainly UVB that tans and burns us. UVC rays, the third type, are completely absorbed by the atmosphere.

Traditionally, sunscreens have been formulated to protect us from UVB and, until recently, those are the rays that have been blamed for skin cancer. The theory was that tanning denotes DNA damage to our skin, which in turn leads to cancer. But because we get so much UVA—about 19 times more—scientists are now debating its role in skin damage and whether today’s sunscreens offer enough UVA protection.

UVA penetrates more deeply into our skin than UVB, making it the chief culprit in the major signs of aging. “All the wrinkles, sagging, the thinning on the back of the hands—things we associate with the elderly—that is not age, it’s sun damage,” explains Dr. David McLean, head of cancer prevention programs at the B.C. Cancer Agency in Vancouver. UVA slows the production of collagen, which gives the skin its texture. Over time, old collagen is broken down. UVA has also been found to suppress the immune function of our skin, and in fact doctors are now using UVA clinically to treat allergic responses. While this may be a benefit to allergy sufferers, there’s concern that immune suppression may also play a role in skin cancer.

The theory gaining ground for how we develop skin cancer is that melanin—the pigment responsible for a tan—can be oxidized to form free radicals, which are cancer-causing agents formed in the body. But the jury is still out on this science.

Wrinkle parlours

Despite warnings about the high levels of UVA in tanning salons, there are about 5,000 indoor locations across Canada, and that number is growing as tanning enthusiasts say they want to “get a start on a tan.” But a Scandinavian study found that baking in a tanning bed just once a month can boost your risk of malignant melanoma by 55 percent.

Understand what you’re buying

Broad-spectrum sunscreens (meaning those that protect us from both UVA and UVB) have been on the market for so long they are now considered the standard. But a surprising number of products still filter out UVB only. “The broad-spectrum ingredients tend to be more expensive than the narrow UVB blockers,” says McLean. “So the cheapest products may not block UVA at all.” He recommends using SPF 60 because to produce this level of protection, products must contain UVA-blocking ingredients such as Parsol 1789, also called avobenzone or dibenzoylmethane.

It may surprise you to know that the sun protection factor (SPF) on product labels is a measure only of the level of protection from UVB rays provided by the product. To determine the SPF, scientists test how much longer it takes skin to burn when it is coated with a sunscreen compared with skin that’s unprotected. Measuring a sunscreen’s ability to provide UVA protection has proven problematic because it has been difficult for experts to agree on a standard testing procedure.

But finally, a new system to rate UVA protection is about to be implemented by the Food and Drug Administration in the United States, and is expected to appear on labels in 2009. It’s a four-star rating system that tells consumers how well a product protects against UVA, with one star indicating low protection and four stars the highest level. Health Canada will need to decide whether to adopt or adapt this system, a process that could take up to 10 years, according to McLean. In the meantime, it’s up to sunscreen buyers to read labels carefully.

How much sunscreen?

Ensuring you don’t get too much sun means spreading on significantly more sunscreen than you likely do now. “The average person applies just one-quarter of the amount that’s used when sunscreens are tested for their SPF value,” says McLean. “That means an SPF 60 is acting as an SPF 15 as most people use it, and a 15 is only as effective as a 4.”

Use the equivalent of at least a teaspoon for each limb, the front of your torso and your back. Apply generously to the face, neck and ears. If you use too little, the UVA rays may be causing damage to your skin. “We have to work harder at remembering our ears and the back of our necks,” says Dr. Cheryl Rosen, director of the Canadian Dermatology Association’s sun awareness program. To allow active ingredients to bond with your skin and provide maximum protection, it’s best to slather on lots of sunscreen about half an hour before you go outside. Re-apply every two hours and don’t forget to use lip protection with an SPF 15 or higher. (Most lip glosses and balms do not guard the lips. In fact, a recent U.S. study showed some lip products may actually increase UV penetration into the lips’ surface.) The chemicals that protect your skin eventually break down, making a sunscreen less effective. To slow this breakdown, store products out of direct sunlight and hot spots such as the back window or dash of a car. Replace sunscreen at least once a year.

For added UVA protection, use a sunblock, which contains ingredients such as zinc oxide and titanium oxide that block and scatter, rather than absorb, UV light. Nano—or very small—particles in some formulations mean they are invisible when applied, compared with earlier versions that appeared as a thick white film, like that often seen on the noses of skiers.

Reducing your risk of skin cancer involves more than relying on a sunscreen. “Timing our outdoor activities has a profound effect on the amount of potential damage,” says McLean. “Playing tennis at 9:30 in the morning is more enjoyable than at one in the afternoon anyway.” And, of course, cover up with long sleeves and a wide-brimmed hat.

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