fitness tracker (image Amazon)

Could your smart watch or fitness tracker, or, more precisely, its strap, be forever? For their Scientific Investigation (IA) students are told they should investigate the relationship between a dependent and an independent variable and that IA's with the focus on just analysing commercially bought products should be avoided. However, in real-world chemistry research this is often not the case. Researchers at the University of Notre Dame, Indiana in the USA have recently analysed the amount of fluoroelastomers in 22 different straps used for smart watches and fitness trackers. Their findings were reported on 18 December 2024 in the American Chemical Society publication Environmental Science and Technology letters.

Fluoroelastomers is a generic name for fluoropolymer rubbers. They are more chemically inert, resistant to change at high temperatures (up to 225 ^oC) and resistant to oil and grease than other types of elastomers. Generally the higher the fluorine content the higher the resistance. Essentially fluoroelastomers consist of disordered polymer chains cross-linked in three dimensions. In their research the scientists at the University of Notre Dame found that 15 out of the 22 wrist bands tested contained elevated levels of fluorine and nine of them, including the three most expensive bands contained polyfluorohexanoic acid (known as PFH_xA).

polyfluorohexanoic acid, CF₃CF₂CF₂CF₂CF₂COOH

Per- and poly-fluoroalkyls (PFAS), which can readily escape from the surface of fluoroelastomers, are known to increase the risk of many health conditions including prostate, kidney and testicular cancer. Because they are so kinetically and thermally stable, PFAS are often called "forever chemicals" as they persist in the environment. An additional worry is that watches and fitness trackers are often worn overnight as well as during the day time and that significant amounts of PFAS may be being absorbed into the body through the skin. More research is obviously needed in this area. In the meantime it may be sensible to check that any wrist bands you are using are not advertised as containing fluoroelastomers.