Hazardous substances found in all headphones tested by ToxFREE project

Daily use – especially during exercise when heat and sweat are present – accelerates the migration of chemicals from the headphones into our body, said researcher Karolína Brabcová. Photograph: Iuliia Pilipeichenko/Getty Images/iStockphoto

You wear them at work, you wear them at play, you wear them to relax. You may even get sweaty in them at the gym.

But 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.