Listening was always performed with the same ear and at the same place in the room. The devices were only used while receiving sound but because of the missing power control system, they were always emitting at maximum power.
Research Center of France Télécom (CNET; Centre National d'Etudes des Télécommunication), France
Geronikolou SA et al.
Frequent cellular phone use modifies hypothalamic-pituitary-adrenal axis response to a cellular phone call after mental stress in healthy children and adolescents: A pilot study
Augner C et al.
Effects of Exposure to GSM Mobile Phone Base Station Signals on Salivary Cortisol, Alpha-Amylase, and Immunoglobulin A