Karen Kaplan / Los Angeles Times

Indoor tanning is a great way to get skin cancer — especially if you start young. People who use tanning beds, sunlamps or tanning booths before age 35 are up to 75 percent more likely to develop melanoma, and those who begin before 25 may double their risk of other types of skin cancer.

So we are once again surprised to find that indoor tanning remains popular with the young women whose fair skin makes them the most vulnerable to the harmful effects of ultraviolet radiation.

The latest evidence comes from researchers at the Centers for Disease Control and Prevention. In a research letter published online Monday by JAMA Internal Medicine, they report that 29.3 percent of white high-school girls went to an indoor tanning parlor at least once a year, and 16.7 percent went “frequently” — at least 10 times in a 12-month period. In addition, 24.9 percent of white women younger than 35 indoor-tanned at least once a year and 15 percent did so “frequently.”

Why is this a problem? As we explained after a 2011 survey by the American Academy of Dermatology found that 32 percent of white women younger than 30 had visited a tanning parlor in the previous year (including 8 percent who did so on a weekly basis):

“The reason tanning turns your skin brown is that it becomes damaged by ultraviolet radiation. This is true regardless of whether those UV rays come directly from the sun or from an artificial source, like a tanning bed or sunlamp. Both short-wavelength UVB and the relatively longer-wavelength UVA damage the DNA in skin cells, increasing the risk of malignant melanoma and squamous and basal cell carcinomas. (And even if you don’t care about cancer risk, consider that UV waves break down the collagen in your skin, causing it to wrinkle.)”

The CDC says indoor tanning is dangerous, and the U.S. Food and Drug Administration warns consumers that the UV radiation from sunlamps and tanning beds “poses serious health risks.” The World Health Organization’s International Agency for Research on Cancer says UV-emitting tanning devices are “carcinogenic to humans.” The U.S. Department of Health and Human Services agrees, saying that exposure to sunlamps or sunbeds is known to be a human carcinogen.” (Spray tans seem to be OK, since they don’t involve UV radiation.)