A small German study demonstrated that the radiation from mobile phones raised blood pressure. The scientists suggested that the mobile phone radiation caused the arteries to constrict.

Ten young volunteers (26-36 years old) agreed to have a mobile 'phone strapped to the right side of their heads. The phones were switched on remotely at random intervals. There was no ‘on’ click to alert the volunteers.

The researchers measured blood pressure and certain heart functions while the volunteers were rested, seating or standing. They detected a 10-15mm Hg average increase in blood pressure whenever the phones were switched on. Such an increase could be dangerous for people who already have high blood pressure.