Scientists from the European ToxFree LIFE for All project tested commercially available headphones for 'endocrine-disrupting' chemicals. These compounds include the so-called 'forever chemicals' bisphenol A (BPA) and the similar bisphenol S (BPS), which mimic the effects of the sex hormone oestrogen inside our bodies, leading to the early onset of puberty in girls, feminisation of males, and cancer. Worryingly, despite well-reported biological effects, the researchers found that 'hazardous substances were detected in every product tested'.