An investigation into headphones has found every single pair tested contained substances hazardous to human health, including chemicals that can cause cancer, neurodevelopmental problems and the feminisation of males.

Even products by market-leading brands such as Bose, Panasonic, Samsung and Sennheiser were found to contain harmful chemicals in the formulation of the plastics from which they are made.

Researchers bought 81 pairs of in-ear and over-ear headphones, either on the market in the Czech Republic, Slovakia, Hungary, Slovenia and Austria, or from the online marketplaces Shein and Temu, and took them for laboratory analysis, testing for a range of harmful chemicals.

“Hazardous substances were detected in every product tested,” they said.

Bisphenol A (BPA) appeared in 98% of samples, and its substitute, bisphenol S (BPS), was found in more than three-quarters. Synthetic chemicals used to stiffen plastic, BPA and BPS mimic the action of oestrogen inside organisms, causing a range of adverse effects including the feminisation of males, early onset puberty in girls, and cancer. Previous studies have shown that bisphenols can migrate from synthetic materials into sweat, and that they can be absorbed through the skin.