People 35 or younger who used the beds regularly had a melanoma risk eight-fold higher than people who never used tanning beds. Even occasional use among that age group almost tripled the chances of developing melanoma.

"This is more information in support of the conclusion that tanning lights cause skin cancer," says Martin A. Weinstock, MD, professor of dermatology at Brown University and chair of the American Cancer Society's (ACS) skin cancer advisory board.

The Swedish researchers studied the tanning bed use of 571 people who had developed malignant melanoma and compared it to the use of 913 healthy people (controls) who did not have melanoma.

Risk of melanoma more than doubled for those who first began using the lights when 35 or younger, and generally increased with more use of the lights until a person had used the lights more than 250 times. Using commercial lights also more than doubled the risk.

Too often, Dr. Weinstock says, the tanning lights are used by people expecting more sun exposure in the near future, such as college students nearing spring break or summer recess.

"They may think that a 'base' tan will protect them from skin cancer, but in reality, the lights just act as a radiation multiplier, further increasing their skin cancer risk," Dr. Weinstock says.

Lights used in tanning beds and sun lamps give off mainly ultraviolet-A (UVA) radiation, according to the study. UVA was classified as a probable human cancer-causing agent by the International Agency for Cancer Research (IARC) in 1992, according to the Swedish study. IARC is a part of the World Health Organization.

"The exposure to sunbeds was found to have greatly increased since the early 1980s, with 80 percent of such exposure among cases and 79 percent of such exposure among controls," writes lead author J. Westerdahl and colleagues of University Hospital in Lund, Sweden.

The authors found about one in three people in the study group used tanning lights, a level of use called "frightening" by Susan Boiko, MD, a practicing dermatologist with Kaiser Permanente in San Diego and a member of the ACS skin cancer advisory group.

"Many in the study were in the younger age groups and have long lives ahead in which more damage may show up," Dr. Boiko says. "Yet a significant number already have melanoma."

Skin damage and skin cancer at earlier ages is becoming more common, Dr. Boiko says. "In my practice, I see people who began using tanning lights and sunbathing in their early 20s and with some, by their 30s, I'm already removing precancerous lesions from their skin."

Dr. Boiko says some patients in their 30s are surprised to learn the skin damage for which they seeking medical attention was caused by radiation from the sun or tanning lights or both. "UVA radiation is very degenerating to the skin," she says. "Some people have really leathery-looking skin at an early age from regular exposure."

"It's not necessarily safer to substitute one kind of damaging radiation for another," Dr. Boiko warns. "And it's certainly not safer to add the two."

The number of new cases of melanoma found every year in this country is on the rise. The American Cancer Society predicts that, in the year 2000, approximately 47,700 new cases of melanoma will be diagnosed in the United States. About 7,700 people are expected to die of this cancer by year's end.