Science: The Sun's Dark Side

For all its beneficence, the sun is not too kind to those who, intentionally or not, overexpose themselves to its warming rays. While most of the harmful solar radiation is absorbed by the ozone layer, enough ultraviolet light gets through the atmosphere to endanger the unwary.

In addition to the occasional painful sunburn, long-term exposure to the sun, especially between 10 a.m. and 3 p.m., weakens the skin's elasticity and brings on premature wrinkling and sagging. Of greater concern, it causes as many as half a million new cases of skin cancer every year. Most of these are basal or squamous...

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