Dangerous tans.

More than 28 million Americans patronize tanning salons each year, with young women constituting the fastest-growing group of users. A recent study published in the Journal of the National Cancer Institute found a staggering 51 percent of high school girls visited tanning beds at least four times in the past year. "Laying out" is a cheap pastime--sessions under the lights run for roughly five bucks a pop--but dermatologists wonder about the long-term costs.

Teens may run the greatest risk of developing skin cancer, says Margaret Karagas, associate director of the Center for Environmental Health Sciences at Dartmouth Medical School. Karagas' research shows that the risk of basal cell and squamous cell carcinoma increases for people exposed at a young age. Tanning lamps pose a particular risk, says Karagas, "because [they] mimic sunlight and provide such an intense, concentrated dose of ultra-violet (UV) rays."

Realizing the potential hazard to young women, many states are imposing legislation to curtail access to tanning facilities. In January, the Ohio state legislature passed a law requiring salons to obtain written permission from the parents of tanners under 18. New Hampshire and Connecticut have proposed similar laws but face strong opposition from the Indoor Tanning Association.

Tanning devotees are quick to dismiss suspected health risks. "Tanning indoors ... is the best way to maximize the benefits and minimize the risks of sun exposure," assures Sun Capsule Tanning Salon. Salons commonly claim tanning beds are a safe alternative to baking outdoors. They argue that the UV rays emitted by lamps seldom produce a reddish sunburn. But any UV rays are potentially carcinogenic. Tanning devices emit almost three times the intensity of outdoor sunlight, says the American Academy of Dermatologists, meaning a 20-minute tanning session can equal an entire day in direct sunlight.

Tanners seem convinced that establishing a "base tan" will protect them from sunburn, an idea dermatologists dismiss as a myth. "I wish I could convince people they don't need a base tan before a vacation," says Dr. Alan Rockoff, a dermatologist for MedHelp International. "Since the most protection that gives you is equivalent to a sun protection factor (SPF) of six, you'll need a 15 or 25 sunscreen anyway"

The facts remain that prolonged tanning sessions can result in sunburn, premature aging of the skin, retinal damage (if protective goggles are not used), suppression of the immune system and skin cancer. A study published in the American Journal of Epidemiology found that many young women who tanned in salons at least 10 times a year had seven times the melanoma incidence of non-users.

While findings such as these out rage medical practitioners (the American Medical Association would like to ban commercial tanning entirely), young women are strangely unconcerned. "Everything is bad for you these days, so why not?" shrugs one salon regular. CONTACT: American Academy of Dermatologists, [phone], www.aad.org; Indoor Tanning Association, [phone], www.theita.com.