How safe are cell phones?

Experts say the concern over cell-phone use stems from a form of radiation that's produced when the devices communicate with their base station. Wireless phones transmit via radio frequency (RF), a low-frequency form of radiation that is also used in microwave ovens and AM/FM radios. While high-frequency radiation (the kind used in X-rays) is known to cause cancer at high doses, the risks of this milder form remain unclear. A cell phone's main source of RF is its antenna, from which it sends a signal to the nearest base-station antenna. The further a cell phone is from the base station, the more RF it needs to establish and maintain a connection. So, the theory is that any risks posed by RF would be greater for people who live and work in areas with fewer base stations.