Want to know how long you can safely stay out in the sun? Check the index

Americans are bombarded with cholesterol counts, blood pressure levels and radon readings. Well, here's another scary number to fret over: the ultraviolet radiation index.

The National Weather Service introduced the index yesterday in 58 cities around the nation, as part of an effort to help Americans avoid hazardous overexposure to the sun.


Step outside in Baltimore around noon today and you'll bask in a "moderate" index level of 6, the weather service predicted. The scale runs from 0 to 10, or minimal to very high, in most areas.

In cities where the sun blazes brightest, such as Honolulu, the index stretches to 15.


Moderate means that fair-skinned people shouldn't stay outside without protection for more than 10 to 12 minutes, the weather service said. Those with darker skins can spend 50 to 60 minutes catching rays, but no more. People who need to spend more time outdoors should consider a hat, sunglasses and sunscreen, says the Environmental Protection Agency.

Long-term overexposure to ultraviolet radiation can trigger skin cancers, cataracts, immune system damage and cause premature aging of the skin. It probably contributes to the nation's 700,000 to 1 million new cases of skin cancer and 1.2 million cataract operations each year, according to officials with the national Centers for Disease Control and Prevention in Atlanta.

Dr. Simeon Margolis of the Johns Hopkins University said that he hopes the index causes sun worshipers to think twice.

"There are still 50 million to 100 million Americans who think that it's their responsibility to get a great suntan in the summer and who, like my children and my wife, go to the beach and lie in the sun and soak up rays, not always with skin protection," he said. "There is more and more recognition that that's a bad idea."

Will Matricciani, the owner of Fence Fair fencing company on North Point Boulevard in Baltimore County, has worked in the noonday sun since he graduated from high school 18 years ago. Now, he said, he's likely to keep track of the ultraviolet index. He may even start using sunscreen regularly.

"I think it's something that we should pay more attention to," he said. "A lot of my employees work outside. . . . There's more concern now, more so than there was before."

Mr. Matricciani said he is worried about reports of the thinning of the Earth's protective ozone layer, which filters out harmful ultraviolet rays.

The increase in illnesses linked to ultraviolet radiation may be more directly linked to lifestyle changes, said Barbara Reiley of the CDC.


"People spend more time in the sun," she said. "People are wearing less clothing. They're engaging in more outdoor activities. Older people are moving to warmer climates."

Weather service scientists in Camp Springs will generate the daily index, using local forecasts and combining them with data from satellites that measure ozone levels in the upper atmosphere.

Yesterday's forecast called for an index of 6 in Baltimore, Washington, Philadelphia, Pittsburgh and Norfolk, Va. New York rated a 5 and Miami an 8. Among the highest cities was Honolulu, with 11.

The index categories include:

Minimal: Index of 0-2; very fair people may burn after 30 minutes. Darker-skinned people considered safe up to two hours.

Low: Index of 3-4; fair people can spend 15 to 20 minutes in the sun. Others face damage after 75 to 90 minutes.


Moderate: Index of 5-6; explained above.

High: Index of 7-9; safe time only 7 to 8 1/2 minutes for the pale. Others should be safe for 33 to 40 minutes. In addition to sunglasses, sunscreen and hats, people should try to stay in the shade.

Very High: Index of 10 and up; light-skinned exposure should not exceed 4 to 6 minutes. For others, 20 to 30 minutes.