Even though UVB rays are stopped at the level of the skin, they can still cause burning and cancer of the skin, although they cause tanning as well. Meanwhile, UVA rays deeply penetrate the skin to cause burns, wrinkles, and skin cancer.
It could be worse. Luckily, the most dangerous UV rays—UVC rays—are blocked by the atmosphere (like tennis balls being hit into the net before they reach you), so they have little effect on you.
Find out more about this book:You: Staying Young: The Owner's Manual for Extending Your Warranty