Scientists find 'forever chemicals' lurking in certain smartwatch wristbands

Certain pricier styles of smartwatch wristband may not just be helping Americans stay fit — they may be exposing unsuspecting wearers to a hefty dose of "forever chemicals," a new study has found.

More expensive wristbands made from fluorinated synthetic rubber tend to contain high amounts of one such compound, called perfluorohexanoic acid (PFHxA), according to research, published Wednesday in Environmental Science & Technology Letters.

“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,” corresponding author Graham Peaslee, a University of Notre Dame PFAS expert and nuclear physicist, said in a statement.

PFHxA is one of thousands of types of per- and polyfluoroalkyl substances (PFAS), a group of manmade compounds known for their ability to persist in the human body and in nature. Found in various kinds of household products, certain firefighting foams and industrial waste, some types of PFAS have been linked to cancer and other serious illnesses.

Because of the ability of PFAS to repel water, sweat and oil, manufacturers have long included these compounds in items like stain-resistant textiles, menstrual products and fitness wear, the authors noted.

The wristbands in question contain what's known as "fluoroelastomers," synthetic rubbers made from chains of PFAS — which are highly durable during sweaty workouts and help avoid discoloration.

But the researchers warned that because the bands are so durable, they might provide easy access for forever chemicals to enter the wearer's skin.

Meanwhile, prior research has shown that more than a fifth of Americans wear a smartwatch or a fitness tracker — and they do so for extended periods of time, the authors noted.

The scientists ended up screening 22 wristbands from a range of brands and price points, looking for both fluorine — which indicates the possible presence of PFAS — and 20 individual types of PFAS. They found that not only did all 13 bands advertised as being made from fluoroelastomers contain the element fluorine, so too did two of the nine bands that were not marketed as such. 

Of all the wristbands sampled, the researchers observed that those that cost more than $30 contained more fluorine than those priced under $15.

When they checked all the wristbands for 20 different types of PFAS, they found that PFHxA was the most prevalent — popping up in nine out of 22 wristbands tested.

The median PFHxA concentration was nearly 800 parts per billion (ppb), with one sample surpassing 16,000 ppb, according to the study. As a basis of comparison, a 2023 cosmetics study conducted by team found a median concentration of around 200 ppb of PFAS.

To date, there are no federal regulatory limits that dictate safety levels for PFAS exposure through the skin. Currently, the Environmental Protection Agency only has set exposure thresholds for drinking water — and for six types of PFAS alone.

That said, Peaslee stressed that he and his colleagues "have never seen extractable concentrations in the part-per-million range (>1000 ppb) for any wearable consumer product applied to the skin."

The scientists acknowledged that they do not currently understand how readily PFHxA can transfer into the skin or whether the compound poses a health risk upon entry.

Nonetheless, the study's lead author, Notre Dame graduate student Alyssa Wicks, recommended opting for lower-cost wristbands made from silicone.

“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.