WASHINGTON (AP) — Just as millions head to tanning beds to prepare for spring break, the Food and Drug Administration will be debating how to toughen warnings that those sunlamps pose a cancer risk.

Yes, sunburns are particularly dangerous. But there’s increasing scientific consensus that there’s no such thing as a safe tan, either.

This is a message that Katie Donnar, 18, dismissed until a year ago when, preparing for the Miss Indiana pageant, she discovered a growth on her leg — an early-stage melanoma, the most dangerous form of skin cancer.

She can’t prove tanning beds are to blame, but started using them as a sixth-grade cheerleader, says she stepped under the bulbs about every other day during parts of high school, and at one point even owned one. No more.

‘‘It seemed somewhat of a myth that I was putting myself at risk,’’ says Donnar, of Bruceville, Ind., who found the melanoma before it spread.

‘‘The warning label was so small, nothing to make me stop and think, ’This is real,’ ‘‘ she said of the tanning bed.

The World Health Organization’s cancer division last summer listed tanning beds as definitive cancer-causers, right alongside the ultraviolet radiation that both they and the sun emit. They’d long been considered ‘‘probable’’ carcinogens, but what tipped the scales: An analysis of numerous studies that concluded the risk of melanoma jumps by 75 percent in people who used tanning beds in their teens and 20s.

Next comes the U.S. Food and Drug Administration, which has long regulated tanning beds as ‘‘Class I devices,’’ a category of low-risk medical devices that includes bandages. Tanning beds do bear some warnings about the cancer link, but the FDA recently decided those labels aren’t visible enough to consumers and don’t fully convey the risk, especially to young people.

So in March, the FDA’s scientific advisers open a public hearing to explore stricter tanning bed regulation, both stiffer warnings and reclassifying them to allow other steps.

‘‘We don’t recommend using them at all, but we know people do use them so we want to make them as low-risk as possible,’’ says FDA UV radiation specialist Sharon Miller.

The Indoor Tanning Association, already fighting pending legislation that would tax tanning salons to help pay for Congress’ health care overhaul, argues there’s no new science to justify increased FDA regulation. Any risk is to people who overdo it, says ITA President Dan Humiston, arguing that’s easier to do in the sun.

The industry is open to some change in warning labels, Humiston says, to ensure customers ‘‘understand the whole process, so there’s no chance they could be overexposed, no chance they could get a sunburn.’’

But the FDA also says some people go too often, using tanning beds three times a week, for example, when its research shows once a week would provide visually the same tan.

The tanning bed debate isn’t an excuse to roast in the sun instead. Nor is melanoma the only risk. Also linked to UV exposure are basal and squamous cell carcinomas, which affect more than 1 million Americans a year. They’re usually easily removed but the American Cancer Society counts 2,000 annual deaths. Melanoma is more lethal: Nearly 69,000 U.S. cases were diagnosed last year, and about 8,650 people died.

Fair-skinned people who don’t tan easily are at highest risk. Melanoma is particularly linked to sunburns at a young age, and while it usually strikes in the 40s and 50s, doctors are seeing ever-younger cases like Donnar.

A good tan provides the equivalent of a sunscreen rated just SPF-4, and even good tanners can get melanoma, says Dr. Margaret Tucker of the National Cancer Institute. Their risk, like everybody’s, increases with increasing UV exposure.

Why? ‘‘If there was enough (UV) to give you a tan, it had to have triggered DNA damage,’’ says Dr. David Fisher of the Dana-Farber Cancer Institute and a spokesman for the Skin Cancer Foundation.

Here’s how: A protein called p53 is activated by genetic damage from UV rays. Its main job is to mend such damage, but it also sets off a chain reaction — triggering production of a hormone that filters down to pigment-producing cells called melanocytes and orders them to color the skin’s surface, Fisher explains.

In other words, ‘‘the very pathway for tanning is directly biochemically linked to the same pathway of carcinogenesis,’’ says Fisher.

He acknowledges it’s impossible to predict if a drop in indoor tanning might translate into less cancer because everyone gets sun.

‘‘We don’t want people to become indoor cave-dwellers,’’ says NCI’s Tucker.

So be out in the early morning and late afternoon, when those UV rays penetrate less, and use sunscreen. In Indiana, that’s Donnar’s new lifestyle, plus some spray-on tanners for pageants.

‘‘My friends call me ’snow princess’ now but I feel comfortable in my own skin.’’