According to the FCC (link), no link has been shown between RF radiation and cancer.

As a physicist, I find the numbers telling. To cause cancer, the radiation would have to damage a DNA strand. The photon energy of RF radiation at 850 MHz is 3.5 micro-electron-volts . The energy of covalent bonds, the bonds between molecules in DNA, are on the order of 1 electron-volt--about 300,000 times the energy provided by the photon. This means that the photons from a cell phone can't break the bonds in DNA. Photons can't "gang up" to break the bonds--it just doesn't work that way.

Even at such low photon energies, it is possible for damage to be done to biological tissue with high radiation power, due to thermal heating (that's how a microwave oven works). None of the power absorption levels listed above, however, are high enough to do anything. In fact, they are roughly comparable to the amount of heat a normal person generates. If the average person consumes 2000 calories (actually kilocalories) a day, and weighs 80 kg (~180 lbs), then their heat generation is 2000 kcal/(24 hours)/(80 kg) = 1.2 W/kg (thank you Google Calculator).

Sorry for the rant, but after hearing a cancer specialist on say on TV tonight that cell phones have no proven connection to cancer I wanted to try running the numbers. If you really want to worry about what health risks your cell phone has, ask yourself how often you use it while driving.