Researchers at Johns Hopkins School of Medicine and at the University of Manchester in England found the first clinical evidence that the same molecular changes that occur with sun exposure happen not only in multiple exposures in a tanning bed, but from even a single exposure.

The 11 study participants were exposed to 10 full-body tanning salon sessions over the course of a two-week period. "The schedule we used was probably not unlike that used by teenagers preparing for a prom or fair-skinned travelers readying for a tropical vacation," the researchers write in the report.

One small portion of the participants’ buttocks was exposed for the first dose and then covered for comparison at the end of the trial, which compared a single ultraviolet (UV) dose to multiple doses.

When tanning parlors first came into being, lead author S. Elizabeth Whitmore, MD, says, they used primarily UVA (98%), the UV rays considered least harrmful. The rays were split at 98% UVA and 2% UVB. However, it took longer to tan. "When we did the study, we went to the manufacturer of the bulbs used in the tanning beds and asked what the biggest seller was and found that the 5% UVB was the most popular," she said. This is the one they used in the study, said Whitmore, an associate professor of dermatology at Johns Hopkins.

The researchers analyzed the study subjects’ skin and blood for two markers that indicate molecular change — cyclobutane pyrimidine dimer (CPD) and p53 protein. CPD indicates that there is DNA damage caused by UV radiation. The p53 protein indicates the body’s attempts at self-repair when it notices something going awry. "The cell responds by putting out a protein (p53)," Whitmore says. "It’s another indication that there is biologic activity and that there is cell damage." And this repair process can eventually fail to do its job completely and the cells begin to replicate abnormally, she says. This is the breakdown in the normal functioning of cells that can lead to malignancy.

The study shows that CPD was produced in a fairly consistent quantity with each exposure. P53 expression was found on the first exposure, but appeared to reduce in multiple exposures. Whitmore and her colleagues speculate that "multiple exposures lead to upregulation of DNA repair, thereby leading to a lesser functional need for p53 protein expression to slow the cell cycle or cause apoptosis [cell death]."

"This is a small study, but everyone reacted the same so it’s significant," says Herman Kattlove, MD, a medical oncologist and medical editor for the American Cancer Society (ACS). ‘It does point out that when our normal cells are exposed to these rays they undergo molecular changes." These changes are believed to be precursors to skin cancer and this study hammers home the point that this activity is not benign or in any way safer than a day at the beach, he tells ACS News Today.

"It should be a warning," Kattlove adds.

While tanning parlors do not actually claim their method of tanning is safer, it is often inferred by the lay public that this is indeed so, says Whitmore. "The importance of [this study] is that you now have it documented that there is no such thing as a ‘safe tan,’" she says.

In summary the authors write: "We believe the entrepreneurs providing this service should be required to inform clients of these "molecular changes" and the potential that they may increase a person’s risk of skin cancer."

The ACS says that there are more than one million cases of basal cell or squamous cell skin cancers, the two most curable, reported each year.

Melanoma, the most serious and deadly form, will be diagnosed in about 51,400 people in 2001. The way to prevent these cancers? Stay out of the sun, and if you are outdoors wear sunscreen with an SPF of 15 or higher and cover up. Visit the ACS website for tips on protecting yourself and your family while enjoying the outdoors, and take the sun quiz to find out if you’re ready for summer.