Just some facts (Score 3)

Microwave ovens operate at 2.45 GHz. This is the first resonance for water molecules. A typical microwave oven radiates 700W. Old cell phones radiate a maximum of 3W at 870 MHz. This is enough to heat the tip of your finger if you were to place it down on the PCB trace at the amplifier output. At most your head would absorb about 1.5 watts next to the antenna. The new PCS phones operate about 1.9 GHz with 500 mW power. I would be much more worried about getting cataracts than brain tumors. This phenomenon has been well documented. Alot of the "old timers" in radar developed cataracts after looking into too many waveguides. BTW 20 watts at 1.9 GHz will burn the sh!t out of your finger. I design RF power amps and kinda get my kicks outta RF burns!