What about wifi ? Since I, we, are sitting next to routers all day long, which I guess are sending more EMW energy through us than 3G towers.
The exposure from towers and base stations will be tiny compared to the exposure from devices. Inverse square law and all that.
With regard to cell-towers: the inverse-square law will underestimate your radiation exposure from a cell-tower, because they are directional and the inv.sq.law relates only to to perfectly isotropic radiators. In other words: you need to factor the cell-tower antenna gain (typically between 7-10dB) into your calculation.
That was my assumption too but I never tested it.
700-900 MHz is used for LTE as well, and is usually preferred due to its building penetration characteristics.