We've been looking at radio frequency field exposure from multiple sources. The main source of exposure in communications is probably the mobile phone handset, because you hold it close to your head and the field strength is strongest right at the tip of the antenna. If you look at base station transmitters, the fields drop off very quickly as you move away from the transmitter. Ambient measurements have shown exposure levels to populations to be less than 1,000-fold from what you would get from a hand-held device.
The big concern is really with mobile phones themselves, rather than the upwards of 5,000 base station transmitters we have across the country now.