Smartwatches are a hot-ticket gift over the holidays, but a new study might have you rethink how you strap the device to your wrist in the future.

The study, which was just published in the American Chemical Society’s journal Environmental Science & Technology Letters, found that some smartwatch and fitness tracker bands may expose the skin to per- and polyfluoroalkyl substances (PFAS), aka forever chemicals. In fact, more expensive wristbands made from fluorinated synthetic rubber can have especially high amounts of a particular forever chemical called perfluorohexanoic acid (PFHxA).

“We actually saw a full-page ad in a magazine that promoted ‘fluoroelastomer’ watch bands, and my research group was surprised to see anybody advertising PFAS in a product,” Graham Peaslee, study co-author and a professor of physics at the University of Notre Dame, tells Yahoo Life. “We realized that many people probably didn’t recognize that fluoroelastomers are a type of PFAS.”

For the study, the research team screened 22 wristbands across a range of brands and price points. Some were brand-new; others were previously worn. The researchers discovered that all of the 13 bands that advertised that they were made from fluoroelastomers contained fluorine, which indicates the potential presence of PFAS. Two of the nine bands that didn’t advertise that they were made from fluoroelastomers also contained fluorine.

The researchers also discovered that wristbands that cost more than $30 typically contained more fluorine than those priced under $15.

The wristbands were also checked for 20 different types of forever chemicals. Based on the findings, PFHxA was the most common, appearing in nine of the 22 tested wristbands. The median PFHxA concentration was nearly 800 parts per billion (ppb), but one sample had a concentration of more than 16,000 ppb. (By comparison, the research team published a 2021 study on cosmetics and found that they had a median concentration of around 200 ppb of PFAS.)

That sounds like a lot — and it is. But how concerned should you be, given that this is on your wrist and not something you ingest? Experts weigh in.

Why is perfluorohexanoic acid bad?

At baseline, perfluorohexanoic acid is a forever chemical. That means it can build up in the body, with Peaslee noting that perfluorohexanoic acid “bioaccumulates” in the blood. “One recent Swedish study reports it to be the third most abundant PFAS in our blood,” he points out.

Perfluorohexanoic acid may do more than circulate in the blood, though. “The existing evidence suggests that this compound can cause liver, developmental, blood and endocrine effects in the human body,” Jamie Alan, an associate professor of pharmacology and toxicology at Michigan State University, tells Yahoo Life. (However, a data analysis conducted by the Environmental Protection Agency did not link perfluorohexanoic acid to cancer.)

How worried about this should you be?

It’s not entirely clear at the moment. While Alan calls the findings “interesting,” she points out that the study didn’t find how much perfluorohexanoic acid is absorbed through the skin, if any.

“Since intact skin acts as an effective barrier to many toxins, it’s unlikely that people will absorb a significant amount of perfluorohexanoic acid — or other PFAS chemicals — through the skin,” Dr. Kelly Johnson-Arbor, a toxicologist at MedStar Health, tells Yahoo Life.

Dr. Ife Rodney, a dermatologist and founding director of Eternal Dermatology + Aesthetics, agrees. “Your skin is a protective barrier from all of these agents,” she tells Yahoo Life. “Even if they were to directly get onto your skin, it’s not clear if they will be absorbed through the skin.” Rodney says she’s “doubtful” that the PFAS will be absorbed into your body enough to cause side effects, but stresses that more research is needed.

The researchers also chemically extracted compounds from the watchbands versus seeing how much leached off through regular use. “Obviously, we are not doing that when we wear these items,” Alan says. “So although they found very high levels, that does not mean any significant amount is getting into our system.”

She also points out that ingesting perfluorohexanoic acid is more likely to harm your health than wearing it on your skin.

Still, that doesn’t mean these bands are harmless. “A significant fraction of short-chain PFAS deposited on the skin can migrate into the dermis, and some fraction will actually enter the bloodstream after passing through our skin,” Peaslee says. “We have not done a human exposure study on these wristbands, but the potential is there for them to become a source of exposure to this toxic chemical simply because we make these wristbands out of a polymeric PFAS.”

Peaslee also points out that there are other nonfluorinated wristband options you can choose from, including ones made from lower-priced silicone.

If you have a smartwatch or fitness tracker band that contains fluoroelastomer, Alan says there’s no need to panic. “But it is good to be aware of cumulative exposure,” she says. If your band starts to get worn or you’re ready for a new look, you can always replace it with a PFAS-free option.