The Erythemal Index is a measure of ultraviolet radiation (UV) at ground level on the Earth. UV exists to the left of the visible spectrum and is divided into three components (UV-A, UV-B and UV-C). UV-B (290-320 wavelengths) is the most dangerous form of UV radiation that can reach ground level. Atmospheric ozone shields life at the surface from most of the harmful components of solar radiation. Chemical processes in the atmosphere can effect the level of protection provided by the ozone in the upper atmosphere. This thinning of the atmospheric ozone in the stratosphere leads to elevated levels of UV-B at ground level and increases the risks of DNA damage in living organisms. Note: View of North and South America with red (denoting highest ground levels of ultraviolet radiation) dominating most of South America and the colors fading to blues (denoting lowest ground levels of ultraviolet radiation) over North America. This data was collected over the year 2000. Animator: Michael Mangos (GST). Scientist: Richard McPeters (NASA/GSFC). Platforms/Sensors/Data Sets: Earth Probe/TOMS.