An investigation into headphones has revealed that every model tested contains substances hazardous to human health, including chemicals linked to cancer, neurodevelopmental issues, and the feminisation of males.
The study found that even products from major brands such as Bose, Panasonic, Samsung, and Sennheiser contained harmful chemicals embedded in the plastics used to make them.
Campaigners have condemned the findings as “a market-wide failure,” calling for broad bans on entire classes of endocrine-disrupting chemicals in consumer goods and greater transparency from manufacturers about the substances in their products.
“These chemicals are not just additives—they can migrate from the headphones into the human body,” said Karolína Brabcová, a chemical expert at Arnika, part of the ToxFree LIFE for All project, a Central European civil society initiative behind the research.
“Daily use—especially during exercise when heat and sweat are present—accelerates this migration through the skin. While there may be no immediate health risk, long-term exposure, particularly for vulnerable groups like teenagers, is concerning. There is no ‘safe’ level for endocrine disruptors that mimic natural hormones.”
Globally, concern is growing about the impact of synthetic chemicals on ecosystems, animals, and humans, with links to rising rates of cancer, obesity, and infertility. Chemicals such as bisphenols, phthalates, and poly- and per-fluoroalkyl substances (PFAS) are widespread, yet many are still used in consumer goods with little public awareness of their potential effects.
Researchers warn that while exposure from individual sources may be low, the cumulative “cocktail effect” of daily contact with multiple sources poses serious long-term risks.
The ToxFree project focused on headphones because they have “transitioned from occasional accessories to essential devices” worn for long periods. Researchers purchased 81 in-ear and over-ear headphones from retail stores in the Czech Republic, Slovakia, Hungary, Slovenia, and Austria, as well as online marketplaces Shein and Temu, and sent them for laboratory analysis.
“Hazardous substances were detected in every product tested,” the team reported. Bisphenol A (BPA) was present in 98% of samples, while its substitute, bisphenol S (BPS), appeared in over three-quarters. These chemicals, used to strengthen plastics, mimic the action of estrogen in the body, potentially causing feminisation of males, early puberty in girls, and cancer.
Studies show that bisphenols can migrate from synthetic materials into sweat and be absorbed through the skin. “Given the prolonged skin contact associated with headphone use, dermal exposure represents a significant pathway, and it is reasonable to assume that BPA and its substitutes may transfer directly from headphone components to the user,” the researchers noted.
The investigation also found phthalates, potent reproductive toxins that can impair fertility; chlorinated paraffins, associated with liver and kidney damage; and brominated and organophosphate flame retardants, which share endocrine-disrupting properties with bisphenols. Most were detected only in trace amounts.
This study is the third conducted by the ToxFree project. Previous investigations revealed BPA in baby pacifiers, including products labeled BPA-free, and found that one in three women’s undergarments contained toxic chemicals.
