New UV Index to Gauge Sun’s Damaging Rays

Weather watchers, especially those with a tendency to sunburn, soon will have another index to consider when planning their outdoor activities: the solar ultraviolet radiation level.

Starting today, the National Weather Service forecast will tally the strength of the day’s rays in 58 cities, including Los Angeles.

With ultraviolet radiation from the sun now considered a culprit in a host of health problems, including skin cancer and cataracts, the new index will allow urbanites to take action to reduce their risks. The UV Index forecast will predict noontime UV exposures, when the sun’s damaging rays are at their strongest.

Residents of the sunny Los Angeles area today face an exposure index of 9 on a scale of 1 to 10, considered “high” but just short of “very high.” An index of 1 or 2 indicates minimal exposure risk, with low-level exposure risk at 3 and 4, and moderate exposure risk at 5 and 6. Ratings of 7, 8 and 9 are considered high, with elevated risks of sunburn and other damage for those not protected.

The new forecasts will be available daily to meteorologists as part of the standard package of weather indicators that they receive from the Weather Service. The new program was announced Tuesday by the Environmental Protection Agency and the National Oceanic and Atmospheric Administration--parent agency of the National Weather Service.

The program is modeled on one started in Canada two years ago, with apparently dramatic success. Eight in 10 Canadians since have told pollsters that they are aware of the government’s ultraviolet forecast and half of those surveyed said they have changed their behavior based on it by staying inside, covering up or using sunscreen. In fact, the program appeared to prompt a boost in sales of such protective lotion.

Officials predicted that by encouraging such precautions, the new forecasts might stem the dizzying rise of skin cancers and cataracts in the United States. Scientists believe that the rise in such illnesses may be attributed to a progressive thinning of a protective layer of ozone in the Earth’s upper atmosphere. They have urged steps both to protect that layer from further erosion from man-made chemicals and to warn people that they may be more vulnerable to the sun’s damaging rays.

In recent years, skin cancer has become the fastest-growing form of cancer, with more than 700,000 new cases each year. And 1.2 million cases of cataracts are diagnosed yearly in the United States, making the eye disease the most costly single item in Medicare spending. Excessive exposure to the sun also is believed to cause premature aging of the skin and to affect the body’s ability to fight off diseases.

“This forecast is a public education tool and it’s generally to increase awareness of the risks of exposure to UV rays,” said Stephen Seidel, of the EPA. “That’s the real value of the program: It becomes part of your consciousness, hopefully.”

But a warning to all who have been caught in the rain without an umbrella: The forecasts are still in the experimental stage because scientists don’t know yet how to predict with precision the strength of ultraviolet radiation through such meteorological obstacles as clouds.

Elbert W. Friday Jr., director of the National Weather Service, said that meteorologists in his agency will use satellites, ground-based weather observations and computer models to generate a picture of a city’s UV exposure at ground level about 30 hours in advance.

Seidel said that the index should be especially useful to parents of young children, who face particular dangers from exposure to ultraviolet rays. Because children spend more of their time outdoors than adults do, about 80% of their lifetime exposure to UV rays occurs before they turn 18. And it is cumulative lifetime exposure to UV rays that appears to increase one’s risk of developing skin cancers or cataracts.

The initiative may not be a hit with everyone, however. Los Angeles weatherman Dallas Raines said that he will not use the new index in his broadcasts, because he does not think it communicates useful information.

“My time is so short on the air. That’s the last thing I need is to take 15 more seconds out of my time just showing someone an index figure,” said Raines, a meteorologist for KABC-TV. “I’m not one to try to scare people. I’d rather explain to them what this means and why UV rays are dangerous.”

The Times begins publishing the index on its weather page today.

Dangerous Rays

The ultraviolet radiation index is developed using satellite instruments to measure the amount of ozone in the upper atmosphere. The ozone layer blocks incoming UV radiation but thin seasonally. Here is Tuesday’s index for selected cities:

EXPOSURE INDEX

Minimal: 0-2

Very fair people may burn in 30 minutes

Low: 3-4

Danger range 15-20 minutes for fair complexions

Moderate: 5-6

Fair complexions safe for 10-12 minutes

High: 7-9

Safe time only 7-8 minutes for fair complexions

Very High: 10+

Danger range 4-6 minutes for those most at risk

Source: National Weather Service, Times Washington Bureau