Many Smartwatch Wristbands Hold High Levels of PFAS ‘Forever Chemicals,’ Study Finds

Wearable tech devices like fitness trackers and smartwatches have become the constant companions of many who rely on them for alerts, transactions and health and location information day and night.

What wearers of these devices may not know is that many of them contain elevated levels of per- and polyfluoroalkyl substances (PFAS) “forever chemicals” that may be leaching from the wristbands into their skin, according to a new study.

The researchers found especially high amounts of a particular forever chemical, perfluorohexanoic acid (PFHxA), contained in more expensive fluorinated synthetic rubber wristbands, a press release from the American Chemical Society (ACS) said.

“This discovery stands out because of the very high concentrations of one type of forever chemical found in items that are in prolonged contact with our skin,” said Graham Peaslee, one of the authors of the study and a professor of physics at University of Notre Dame, in the press release.

PFAS are a category of chemicals found in consumer products that repel sweat, oil and water, and can persist in the environment for hundreds — even thousands — of years. The forever chemicals are frequently found in waterproof clothing, nonstick cookware, menstrual products, stain-resistant bedding and fitness wear like wristbands and smartwatches.

The wristbands contain fluoroelastomers, which are synthetic rubbers made from PFAS chains, that create a material capable of repelling dirt and avoiding discoloration. While the bands are durable and work well during intense workouts, they may also be a source of PFAS compounds that literally get under the skin of the person wearing them.

The researchers analyzed several watchbands for the presence of 20 individual PFAS, including fluorine.

They looked at 22 wristbands from a variety of brands and price ranges — most of them new, but a few that had been previously worn. All 13 wristbands were advertised as having been made from fluoroelastomers that contained the element fluorine. However, two out of nine of the bands that did not disclose that they had been made from fluoroelastomers did contain fluorine, indicating the potential for PFAS.

“Many ‘smart’ and ‘fitness’ watch bands are advertised to contain fluoroelastomers, a type of synthetic rubber designed to be resilient against skin oils and sweat. Fluoroelastomers, which are considered a polymeric form of per- and polyfluoroalkyl substances (PFAS), have historically involved the use of shorter-chain PFAS as surfactants in the polymerization process,” the authors of the study wrote.

The researchers found that wristbands priced at over $30 contained a greater amount of fluorine than those that cost under $15. They checked all of the wristbands for 20 distinct PFAS and found that PFHxA was the most common. It appeared in nine out of 22 of the tested bands. The average concentration of PFHxA was almost 800 parts per billion (ppb), with one sample exceeding 16,000 ppb.

Earlier research by the team on cosmetics found an average PFAS concentration of approximately 200 ppb. Just six PFAS currently have federally defined limits for exposure through drinking water in the United States.

“We have never seen extractable concentrations in the part-per-million range (>1000 ppb) for any wearable consumer product applied to the skin,” Peaslee said.

The findings of the study suggest that the large PFHxA concentrations found in fitness wristbands could be the result of the compound’s use as a surfactant when manufacturing fluoroelastomer.

Scientists don’t currently know how easily PFHxA transfers into human skin, nor what the possible health effects are once it is there. Peaslee said recent studies suggest a notable percentage could potentially pass through the skin under normal conditions.

“The very high concentrations of PFHxA readily extractable from the surfaces of fluoroelastomer watch bands, together with the current limited knowledge on the dermal absorption of PFHxA, demonstrate the need for more comprehensive exposure studies of PFHxA,” the authors wrote in the study.

The team recommended buying lower-cost wristbands that have been made from silicone, according to lead author of the study Alyssa Wicks, a graduate research assistant in the University of Notre Dame Department of Chemistry and Biochemistry.

“If the consumer wishes to purchase a higher-priced band, we suggest that they read the product descriptions and avoid any that are listed as containing fluoroelastomers,” Wicks said in the press release.