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.
