Ultraviolet (UV) radiation is the single most important cause of skin cancer, especially when the overexposure resulted in sunburn and blistering. Other, less common causes of skin cancer include repeated exposure to x-rays and exposure to coal tar, arsenic, and other industrial compounds.
Sunlight provides much that is beneficial and even necessary to life and good health. Tanning and burning, however, are not among those benefits -- there is no such thing as a "healthy tan."
Over the past decade, researchers have discovered that the tanning response begins only after DNA in skin cells has been damaged by exposure to sunlight. Although the exact wavelengths and timing of the solar radiation associated with different types of skin cancer are under investigation, the basic preventive lesson remains the same: protect your skin from the sun.
Fortunately there are ways to prevent most non-melanoma skin cancers and to detect them early when they do arise. When treated early, the vast majority of these cancers are curable.