The band on your smart watch may contain chemicals that scientists have linked to fertility problems and cancer, according to a new study.
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are chemicals that are widely used in manufacturing everything from fabric to nonstick pans to cosmetics.
They don’t break down in the body or environment, hence the nickname ‘forever chemicals, and have been found in air, water, fish and soil across the world.
Some studies have linked them to birth defects, increased risk of prostate, kidney and testicular cancer and fertility problems.
The new paper tested 22 different brands of smart watches and found that 15 of them contained PFAS chemicals, though they did not reveal which brands.
They found more expensive brands were more likely to have high levels of the toxins than less expensive brands.
These devices are all the rage in a wellness revolution increasingly focused on individuals interested in tracking their sleep, exercise and heart rate data.
Roughly 21 percent of US adults and 35 per cent of Brits are believed to use a smart watch, and they wear them for an average of 11 hours at a time.
Smart watches offer programs to track sleep habits, heart rate, exercise and more. The average user wears their device for 11 hours a day, according to the study
Some studies have suggested that long term wear of products containing PFAS may make it so that these chemicals are absorbed through the skin and stored in the body
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This means around 54million people in the US and 13 million in the UK could be exposed to these chemicals for long periods every day.
The researchers did not share what brands they tested.
Some popular options include the ASWEE Smart Watch, which retails online for $89 (£70) and the AppleWatch, which retails online for between $249 (£195) and $799 (£625).
Many of these brands come automatically with a flexible, silicon-like band, though customers are able to swap it out for other options.
Traditionally, researchers have concluded that the most common way that PFAS takes up residence in the body is by being swallowed or inhaled.
However, some studies have suggested that prolonged skin contact with a PFAS chemical can make it get absorbed into your skin, but it’s unclear if this is common or if it has an effect on the body.
There are thousands of different kinds of these chemicals, and organizations like the Environmental Protection Agency are actively working to track what health effects each might have on the body.
This study, which was published in the journal Environmental Science & Technology Letters, focused on a PFAS called Fluoroelastomers.
The ASWEE Smart Watch which sells on Amazon for $89. The Apple Watch sells online for between $249 (£195) and $799 (£625)
These are sometimes added to watch bands to help them retain color even after frequent contact with oil from skin, but it’s not always clear what brands use the chemical.
So in order to determine how widespread the chemical was, the Notre Dame researchers conducted chemical analyses on each of the watch bands.
They were looking to see if the bands contained fluorine, a sign that the PFAS in question was present.
In 15 of the products, which is about 68 percent of those tested, the researchers found evidence of PFAS.
Most of those bands had advertised that they contained fluorine, but two tested did not divulge that the chemical was used in the manufacturing process.
The bands that cost more than $30 (£23) had higher levels of fluorine than those under $15 (£11).
The researchers also conducted chemical analysis for other kinds of PFAS chemicals aside from fluroelastomers – and found that all 22 contained at least some signs of one of the chemicals.
The researchers said these forever chemicals likely got into the product as a cleaning agent during the manufacturing process.
A 2024 study mapped out the potential different sources of a number of different kind of PFAS chemicals from manufacturing facilities. Each different colored dot corresponds to a different potential kind of industry
The researchers noted that it’s unclear if people readily absorb fluroelastomers through the skin, and if they do, how much they take up.
A 2022 study in Germany that had participants wear sunscreen with a PFAS chemical in it for 115 days found that 1.6 percent of the total amount of chemical applied was absorbed into the skin.
On the more extreme end, a different study conducted in 2024 by British researchers found that applying PFAS to skin cells grown in the lab caused about 58 percent of the total amount of chemical applied to be absorbed into the skin.
The authors said: ‘These limited studies suggest that dermal absorption of PFAS may represent a significant exposure route for short-chain PFAS when used in consumer products that are in contact with the skin’.
Even though the science is ongoing, study author Alyssa Wicks, said, consumers still may want to pay attention to what’s in their band out of an abundance of caution.
Dr Wicks said: ‘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.’
