Most people who own a smart watch or fitness watch use a band made of synthetic rubber to hold the device on their wrist. Although the bands are designed to feel comfortable against the skin, a recent study in the journal Environmental Science & Technology Letters found that they may be harmful. This is due to the substances they are made from known as fluoroelastomers which can contain large quantities of a dangerous so-called forever chemical known as perfluorohexanoic acid (PFHxA); it is unclear the extent to which this can be absorbed through the skin.PFHxA belongs to a classification of industrial products known as per and polyfluoroalkyl substances (PFAS), which do not biodegrade and resist breaking down after exposure to water and light, hence the nickname forever chemicals. They have been linked to extreme health problems like cancer, high blood pressure and infertility. Despite these risks, PFAS are widely used in products like non-stick cookware, umbrellas, cosmetics, furniture, cleaning chemicals, water-resistant fabrics and stain-resistant coatings. PFHxA specifically is commonly used in pizza boxes, rain jackets, firefighting foam and waterproofing sprays.RelatedHeres how to remove some persistent pollutants from your drinking water at homeWhile the scientists behind the study werent originally looking for PFHxA, the forever chemical was the most frequently detected compound within the 22 watch bands analyzed across numerous brands and price points. Lead author Graham F. Peaslee, a physicist at the University of Notre Dame, told Salon that the researchers had not even been aware that PFAS were used in the watch bands until they saw a full-page ad touting them for being made of fluoroelastomer."The good news is that the consumer can opt for alternative wrist bands to avoid potential PFAS exposure risks."We realized that the general public didn't recognize fluoroelastomers as a type of PFAS, Peaslee said. Like all other forms of polymeric PFAS, we suspected that these materials would also have other PFAS readily available together with the fluoropolymer, and we searched for 20 common PFAS. Thats when they found the surprisingly high concentrations of PFHxA, a forever chemical that can enter the body after being eaten, inhaled, consumed through drinking or absorbed through the skin.This was unique in the sense that it was the first time we had found only one PFAS, and that it was at such high concentrations much higher than we typically find in consumer products, Peaslee said.While the scientists didnt test this with humans, they still reported that the high levels of PFAS in these products poses an opportunity for significant transfer to the dermis [skin] and subsequent human exposure. Additionally, several of these watch bands were advertised as sports and fitness monitors, implying that the wearer may be exercising with them, which means additional sweat contact and open skin pores.Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter Lab Notes.Importantly, Peaslee noted that this is one instance in which a forever chemical was not necessary to include as an ingredient.There were many wrist bands available that don't use PFAS and without concern for the toxic shorter-chain PFAS that can be in direct contact with the consumer's skin, Peaslee said. The good news is that the consumer can opt for alternative wrist bands to avoid potential PFAS exposure risks.He added, It is just a question of knowing that they are present and it is possible to avoid those with fluoroelastomer materials.In addition to PFHxA, the nearly endless varieties of PFAS include perfluorooctanoic sulfonic acid (PFOS), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and perfluorononanoic acid (PFNA). As of 2019, there were more than 4,700 documented PFAS, even though most of them perform the same basic function making products more resistant to stains, grease and other kinds of damage.We need your help to stay independentSubscribe today to support Salon's progressive journalismAccording to Dr. Anna Reade, senior scientist at the Natural Resources Defense Council (NRDC), chemical engineers have created this wide variety of forever chemicals to engage in a practice known as regrettable substitution. When certain forever chemicals face increased regulation or notoriety, manufacturers try to have their cake and eat it too (often successfully) by swapping out the specifically banned compound for a slightly different alternative."There are two really good examples that are supported by just a ton of evidence now," Reade told Salon in July, mentioning the two different PFAS known as PFOA (which was used to make teflon) and PFOS (which was used to make Scotchgard)."When those came under scrutiny, one of the big substitutions was to use a four-carbon version of PFOS instead, Reade said. What they did was they just used a different chain length, exactly the same molecule, but just a shorter version of it, a smaller version."The final result was that "they switched to that and said it was safe because there wasn't any data on it," Reade said. The practice of engaging in regrettable substitution is still prevalent today.Read moreabout toxinsBy Matthew RozsaMatthew Rozsa is a staff writer at Salon. He received a Master's Degree in History from Rutgers-Newark in 2012 and was awarded a science journalism fellowship from the Metcalf Institute in 2022.MORE FROM Matthew RozsaRelated Topics ------------------------------------------Apple WatchExplainerForever ChemicalsHealthPfasPollutantsScienceSkinSmart WatchSmart Watch BandToxins