That hotel you have booked for your upcoming getaway? You might want to double-check whether there are any smoking rooms in the place—even if you requested a nonsmoking room: You can get third-hand smoke exposure from staying in a nonsmoking room if the hotel has other rooms where lighting up is allowed, according to new research published in Tobacco Control.

For the study, participants checked into a sample of rooms in 40 California hotels: 10 that had complete smoking bans, and 30 in which smoking was only banned in certain rooms. Researchers then tested surfaces and air in the rooms for tobacco smoke pollutants. The participants also stayed overnight in the guest rooms and then had their urine and fingers tested for exposure to nicotine and the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The test results showed that the nonsmoking rooms of hotels with partial bans had 40 percent higher air nicotine levels than the rooms in hotels with complete bans. While that’s much, much lower than the 2,100 percent higher levels that researchers found in designated smoking rooms, it’s still concerning, says study author Georg E. Matt, PhD, a professor of psychology at San Diego State University—especially since nonsmokers who stayed in the hotels with partial bans also had higher levels of contaminants from tobacco in their finger swipe and urine samples.

“Lo and behold, designation policy doesn’t really work,” he says. “We learned that tobacco smoke spreads throughout an entire hotel.”

While this study didn’t examine the health consequences of spending the night in a hotel with a partial smoking ban, previous research suggests that continued exposure to third-hand smoke can cause DNA damage that might lead to certain types of cancer.

That said, you don’t have to freak out if you’ve stayed at a hotel that allows smoking in certain rooms—or if it’s too late to change your upcoming reservations without losing your money.

“If you have a healthy young adult without any respiratory or heart conditions who stays in a hotel room one night in a designated nonsmoking room, I would not expect any great health outcomes,” says Matt. “But if you have, for instance, a hotel worker who every day for six to eight hours spends time in designated nonsmoking rooms, that’s a different story.”

People with asthma or other respiratory problems may want to be particularly diligent about seeking out 100 percent smoke-free hotels, says Matt. Even if that’s not you, asking a hotel if it allows smoking in any of its rooms—and choosing not to stay at ones that do—may help encourage change in the industry.

“It’s key that we turn these hotels into 100 percent smoke-free environments to protect hotel workers, as well as to protect nonsmoking guests,” says Matt.

More From Women’s Health:
What Smoking Does to Your Body
7 Ways to Protect Yourself From Cancer
Put Down the Hookah!

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