Wednesday, March 14, 2007

More on Sunscreens

This morning I finally came across the science article I’d been dreading. With the kids off to school and the dog walked, I settled in to my morning routine, coffee, bagel and Science Magazine. After skimming articles on ancient towers marking the solar calendar in Peru, brain evolution, and African penguins, I came across a News Focus article entitled “A Healthy Tan?” written by Ingrid Wickelgren. Over the past ten years as I’ve coated the kids with sunscreen I’ve been waiting for the inevitable. As a scientist I know that science is always on the move, particularly when it comes to understanding how the body responds to chemical or physical (as in the sun’s ultraviolet rays) insults. As scientists learn more, things change. So I’ve been waiting for the down side of sunscreens. The, “If we only knew then, what we know now.”

Though the news isn’t all that bad, it is worth considering that scientists and those in the health fields are still figuring out the best way to protect those of us who insist on playing in the sun (besides the obvious – just cover up!)

According to Wickelgren:

Anyone who relies on sunscreen knows it is sticky, inconvenient, and easy to forget. But sunscreen has a lesser known, and more serious, downside: It doesn't adequately protect against the deadliest form of skin cancer.

Although ultraviolet (UV)-blocking sprays and creams protect people against sunburn and the milder forms of skin cancer--squamous cell and basal cell carcinoma--they do not form an effective shield against melanoma, which doctors diagnose in 132,000 people worldwide each year. Ironically, says a growing cadre of skin biologists, what seems to protect best against melanoma is something that sunscreens efficiently thwart: a deep, dark tan.

Dark-skinned people, who also tend to tan well, are up to 500 times less likely to get melanoma and other skin cancers than are fair-skinned individuals. The ability to tan confers protection, researchers say, regardless of the skin's background level of pigmentation. This is due in part to the UV-shielding effect of melanin, the pigment that makes skin cells dark, and perhaps in part to an acceleration of DNA repair that some believe accompanies tanning. But tanning in the sun is a fool's wager, dermatologists say, because it causes dangerous DNA damage, which may lead to cancer before it can be fixed. To provide a sun-independent alternative, scientists are now developing compounds that trigger tanning and DNA repair by acting on molecules that control the melanin production pathway.”

The complete story can be found in Science, March 2, Vol 315 pages 1214-12166.