Weather Service and public health officials hope people will use the index to prevent overexposure to UV rays, which cause as many as three-quarters of the 700,000 skin cancer cases in the United States each year. Medical specialists say UV light also is responsible for eye problems and damage to the immune system.

The EPA and the Centers for Disease Control and Prevention are working with the National Weather Service to spread information about the index, which scientists developed during the last year. The index rates the danger of UV exposure on a scale of 0 to 15, with 15 indicating that even those who rarely burn could receive some skin damage after only about 20 minutes in the sun.

INFO-GRAPHIC,,Twp CAPTION: NEW UV INDEX The National Weather Service will release a UV reading each day in selected areas of the country, including the Washington area. The chart below shows various index values and the amount of time it would take for some skin damage to occur: Value......... For light-skinned................ For dark-skinned ranges ....... people who "never tan"... people who "rarely burn" .............. (most susceptible). ......... (least susceptible). 0-2 Minimal .... 30 minutes ............... More than 120 minutes 3-4 Low ........ 15-20 minutes .................... 75-90 minutes 5-6 Moderate ... 10-12 minutes .................... 50-60 minutes 7-9 High ....... 7-8.5 minutes .................... 33-40 minutes 10-15 Very High. less than 4-6 minutes ............ 20-30 minutes