Radiation from mobile phones is not strong enough to heat biological tissue or break chemical bonds in cells. However, it may affect cell behaviour. Researchers exposed ten female volunteers to radiation at 900 MHz from mobile phones to simulate an hour long phone call. They screened 580 different proteins in their skin cells. They found that the numbers of one protein increased by 89 % in all volunteers. Numbers of a second protein decreased by 32 % in all volunteers. This is the first study to show molecular effects of phone radiation on humans.