I remember reading a study which suggested that cell phone radiation absorbed by the brain when the phone is close to the head (such as while talking) can help prevent Alzheimer's disease. I **** you not.

I also have done the physics on this and I'm not worried. Human cells range in size from about ~.00076mm to ~.008mm. Human DNA is about .0000025mm wide (and MUCH longer). Ultraviolet radiation is on the order of 0.00001mm to 0.0004mm which you'll note correspond to about the size of a human cell. Human cells aren't directly resonant with ultraviolet radiation, but they are close and hence the danger posed by the powerful ultraviolet radiation of the sun.

Cell phone signals on the other hand are on the order of 158mm for the 1900 MHz spectrum and 353mm for the 850 MHz spectrum. Nowhere near the size of the human cell. This puts the human body pretty safely outside of the range of cell phone radiation being harmful. The human body is transparent to them.

Granted there could be structures within the human body that serve as decent antennae for electromagnetic energy on that wavelength, but the very low transmitted power of a cell phone, the dispersion of that power over a very wide range (effectively reducing that power even more), and the high resistance that any structure would probably have mean these structures are also not very likely to add any harm.