850 MHz. That's the old analog cellular band. Handsets transmit on 825-845 and the cell towers transmt at 870-890. The little wimpy PCS phones are up around 1.9 GHz. (1900 MHz.) which is much closer to the resonant frequency of water (~2.4 GHz.). There, the concern is still RF induction heating of tissue (especially grey matter) and the effects are believed to be cumulative.
Also, since the little jobs don't have much range to them, the PCS providers need to build more towers, so power density is a concern.
On the subject of cell phones: Does anyone make a proper cell phone for the car? I mean with an 8 watt power unit in the trunk and a proper sized handset...
FCC limits power levels on the old CMT band to 3W for mobiles and 600mW (0.6W) for handsets. I think the PCS phones are handsets only, and due to their small size (smaller batteries) I would suspect they're running somwehere under 100 mW.