An investigation into the headphones used by millions for work, leisure, and exercise has found that every single pair tested contained substances hazardous to human health, including chemicals linked to cancer and reproductive harm.
The study, conducted by the central European ToxFree LIFE for All project, analysed 81 pairs of in-ear and over-ear headphones purchased in the Czech Republic, Slovakia, Hungary, Slovenia, and Austria, as well as from the online marketplaces Shein and Temu. Campaigners have condemned a “market-wide failure” after laboratory tests detected harmful substances in the plastic components of every product, including those from leading brands such as Bose, Panasonic, Samsung, and Sennheiser.
The Chemicals Inside
Researchers identified a cocktail of problematic substances. Bisphenol A (BPA), a known endocrine disruptor, was found in 98% of samples. Its common substitute, bisphenol S (BPS), was present in more than three-quarters of the products. These synthetic chemicals mimic the action of oestrogen inside organisms and have been linked to adverse effects including the feminisation of males, early onset puberty in girls, and cancer.
Other substances detected included phthalates, potent reproductive toxins that can impair fertility and have been associated with health issues from type 2 diabetes to reduced sperm count. Chlorinated paraffins, used to soften plastics, were also found. Certain short-chain chlorinated paraffins are classified as possible human carcinogens, banned in Canada since 2013 and listed for elimination under the Stockholm Convention, yet they continue to appear in consumer goods.
Trace quantities of brominated and organophosphate flame retardants, which have similar endocrine-disrupting properties, were additionally present. These chemicals, added to prevent burning, have been linked to harm to neurological, reproductive, and immune systems.
Migration and the ‘Cocktail Effect’
According to the ToxFree project, these chemicals are not inert additives. “These chemicals are not just additives; they may be migrating from the headphones into our body,” said Karolína Brabcová, a chemical expert at Arnika, which is part of the project. She noted that daily use, particularly during exercise when heat and sweat are present, accelerates this migration directly to the skin.
While the immediate health risk from a single product may be low, researchers warn of a potentially severe “cocktail effect” from daily, multi-source exposure to such endocrine-disrupting chemicals (EDCs). “Although there is no immediate health risk, the long-term exposures – especially for vulnerable groups like teenagers – is of great concern. There is no ‘safe’ level for endocrine disruptors that mimic our natural hormones,” Brabcová stated.
The investigation is the third of its kind by the ToxFree project, which previously found BPA in baby dummies and toxic chemicals in one in three pairs of women’s underpants. The group said it focused on headphones as the devices have “transitioned from occasional accessories to essential tools”, worn for long periods.
Regulatory Gaps and Calls for Transparency
The findings highlight ongoing challenges in regulating hazardous chemicals in consumer goods. Over 1,000 endocrine-disrupting chemicals are estimated to be in use, yet only about 1% have been studied for safety, according to the research briefing. While some progress has been made—such as an EU ban on endocrine disruptors in cosmetics and France requiring manufacturers to inform consumers of their presence—campaigners argue it is insufficient.
They are calling for broad bans on whole classes of EDCs in consumer goods and far greater transparency from manufacturers about what is in their products. The sheer number of chemicals, combined with delayed effects of exposure and the difficulty in tracking all harmful substances and their by-products, makes comprehensive regulation complex.
In a separate finding noted in the research, specific models like the Bose QC and Sennheiser Momentum 4 were found to have harmful substances in their ear pads in concerning quantities. Bose, Panasonic, Samsung, and Sennheiser did not respond to requests for comment on the investigation’s findings.
