Interviewer: For our first feature we turn our eyes to the sky to see what dangers come from the sun. We'll learn it's not the light the sun produces, but the ultraviolet rays that are dangerous.
Dr. Katz: An ultraviolet ray is an electromagnetic ray that is shorter than visible light.Interviewer: Dr. Stephen Katz is the director of the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Dr. Katz: Ultraviolet B is the most damaging of the ultraviolet rays because ultraviolet B does get through the earth's surface and ultraviolet B can cause sunburn as we know it. It causes sunburn to a much greater extent than ultraviolet A causes any problems, but ultraviolet A can cause immediate pigmentation or immediate darkening of the skin. But it's UVB that all of the sunscreens have traditionally been geared towards blocking because that's the major form of ultraviolet that causes sunburn.